\ ^ -^4 /^ Digitized by the Internet Archive in 2011 with funding from Boston Library Consortium IVIember Libraries http://www.archive.org/details/radioforeverybodOOIesc RADIO for EVERYBODY T ISTENING to the foremost citizens of the nation; JLj keeping in touch with the affairs of the world; enjoying the classical and popular music of yesterday and of the very hour; spanning hundreds and even thou- sands of miles withomt physical conductors between the talker and the listener; handling current by the kilowatt and by the thousandth of a watt; starting with the simple receiver and cuhninating with a powerful trans- mitter, even one capable of spanning the Atlantic, as shown in this painting — all these features and many others make radio the fascinating subject which it is to layman and professional alike. •— ^ Radio for Everybody Being a popular guide to practical radio- phone reception and transmission and 'o the dot-and-dash reception and transmission of the radio telegraph, for the layman who wants to apply radio for his pleasure and profit without going in'o the special theories and the intricacies of the art. By AUSTIN C. LESCARBOURA Managing Editor, Scientific American SCIENTIFIC AMERICAN PUBLISHING COMPANY MUNN & COMPANY .^ . New York 1923 BO^ON COLLKGE LTBRARf Copyright 19^2 By Scientific Americax Publishing Co. All Rights Reserved The right of translation into all languages, including the Scandinavian, is reserved. Printed in the United States of America by the Andrew H. Kellogg Co., New York PREFACE CLOTHES and books — good clothes and good books, to be sure — have something very much in common. Both must be made to fit a very definite type of person in order to prove satisfactory. So, in building or making a suit or a book for a given type of person, it is necessary first of all to study that type, take all the necessary measurements, learn what the likes and dislikes happen to be, and in every way study the type to be fitted. Then, with all these special facts in hand, there remains the task of building or making a suit or book to fit the type we have selected or the type that has selected us. This work is not a ready-made product; at least, that is not the way I have gone about put- ting it together. I spent some time studying the reaction of the general public to radio, follow- ing the inauguration of the first radio-phone broadcasting stations. I installed a radio-phone iv PREFACE receiving set in order to study this new art and its practical application at first hand. Indeed, the manuscript for this book was written on the very table on which I have my radio receiving set; and as urgent as this work has been in order to have it appear within the shortest possible time to be of greatest service to the public, I am free to confess that I have been unable to resist the temptation of donning the head 'phones and listening in on the radio-phone concerts at odd moments. So the work, you can rest as- sured, has been inspired by actual contact with the new art and with the persons seeking to gain a practical knowledge of this new art. The hundreds and thousands of inquiries which have found their way to the editorial rooms of the Scientific American alone, not to speak of conversations with persons met in and out of business, have been an invaluable guide in plan- ning this work to fit the new radio layman. Radio-phone broadcasting has changed the aspects of radio. A year or more ago, radio appealed to the boy and young man in search of some intricate, mysterious, time-consuming hobby in which to invest spare moments and inventive ability. These radio amateurs, as they are called, care more for the construction and PREFACE V wiring and theoretical functioning of their re- ceiving and transmitting equipment than they do for the actual signals they handle. They look upon radio as an engineering study. The radio-phone music and dot-dash messages are, in many instances, purely incidental. But our present radio-phone concerts have brought a new element into radio. What with talks by prominent men, weather forecasts, crop and market reports for farmers, bed-time stories for children, shipping news, fashion talks, health chats, musical selections and other features which can now be received every day and eve- ning right in the home, radio has become a means to an end. That end is the entertainment and educational value of the radio-phone broad- casting service. And the public is becoming more and more interested in that end, and with radio only so far as it is necessary in order to secure the radio-phone service. However that may be, the radio-phone service is a radio proposition. It calls for radio ap- paratus and some knowledge of radio com- munication as a whole, just as the owner of an automobile should have a general knowledge of the mechanism of the automobile, even though it is not necessary to delve deeply into the minute vi PREFACE construction of his machine and into the expan- sive field of automotive engineering. What is required is practical and helpful information about the mechanism with Which the desired re- sults are obtained. . This work has been written with that very thought in mind. It has been built or made for the layman who wants to enjoy radio-phone concerts and talks and bulletins to the utmost, but does not want to take up time and trouble studying the intricacies of radio engineering. It aims to give the essential information without the theory and mathematics. It has much of interest to the beginner who is going to build or buy a radio set; it can teach not a few things to the radio devotee who possesses a radio re- ceiving set and wants to learn more about his set and better sets; it may possibly have some- thing of interest for the radio amateur who has progressed pretty far along in the art, although I am frank to say that for the dyed-in-the-wool radio amateur and the radio engineer, this book is no doubt too elementary. I take this opportunity of thanking the radio fraternity as a whole for its co-operation. More particularly, I wish to thank Mr. Pierre H. Boucheron for going over the more technical PREFACE vii parts of this book; the General Radio Company, the Westinghouse Electric and Manufacturing Company, the Radio Corporation of America, the Pacent Electric Company, and C. Brandes, Inc., for their practical co-operation in enabling me to obtain much of the following data at first hand. In reading the following pages of this little book you will, I hope, obtain as much pleasure from its practical application as I have had in gathering the material together and writing it for you. The Author. New York, April loth, 1922. CONTENTS CHAPTER I. The Elements of Radio Reception and Trans- mission 1 CHAPTER H. Radio-Phone Broadcasting — What it is and What it Means 3^ CHAPTER HL Dot-and-Dash Broadcasting: Erom Market News to Time Signals 73 CHAPTER IV. Receiving Equipment and the Interception OF Radio Waves 93 CHAPTER V. Operating the Radio Receiving Set and Mas- tering the Telegraph Code 143 CHAPTER VI. Making .Big Sounds Out of Little Ones, or the Gentle Art of Amplifying 177 CHAPTER VII. Transmitting the Dot and Dashes of the Damped Radio Telegraph 205 X CONTENTS CHAPTER VIII. The Radio-Telephone Transmitter and C. W. Telegraph Transmitter 229 CHAPTER IX. The Unusual Uses of Radio on Land and Sea AND in the Air 247 CHAPTER X. Radio in Working Clothes or the Application OF Radio to Everyday Business 259 CHAPTER XI. How TO Construct Simple Radio Receiving Sets for Radio-Phone Programs 279 CHAPTER XII. The Radio-Telephone of Today and Tomorrow 307 Chapter I. THE ELEMENTS OF RADIO RECEP- TION AND TRANSMISSION AS far as nine persons out of every ten are concerned, the main interest in radio is to receive the radio- phone music and talks. Whether the receiving set is of the loose-coupled type or whether it employs the Arm- strong regenerative scheme makes little or no difference. These details are as so much Latin or Greek to the average person. The main object, after all, is to know just what kind of set is necessary, how simply it can be installed, and what it will cost. Otherwise stated, the average man is interested first and last in the performance and not in the thing itself. He wants to receive the radio-'phone service without delving into the intricacies of radio — and we do not blame him. It should be that way. The radio-phone broadcasting service has given radio a popular mission to fulfill. It has brought radio out of the laboratory and commercial world and introduced it into the home circle, there to enlighten and to entertain as nothing else ever could. Formerly, radio was known and appreciated by the pub- lic at large in a very general and vague sort of way; but it was only on rare occasion that the average man came into intimate contact with radio. Certain persons who became interested in radio Avere mostly of that kind who delve deeply into intricate things and master numer- ous and difficult details. They have an engineering or even an experimental and inventive turn of mind. Such 2 RADIO FOR EVERYBODY persons no doubt care more about the arrangement and delicate manipulation of the components of their receiv- ing sets than they do about the kind of messages that are picked up. Listening to a radio-phone service, they are thinking all the while in terms of decrement and modula- tion and continuous wave transmitters, and in many in- stances they do not even know what has been said or played at the end of the performance ! Their's is a real interest in radio for the art's sake, but they are decidedly in the minority. Today, be it remembered, the radio-phone service be- longs to everybody. It is intended for the public at large. And by the same token that branch of radio ac- tivity for which it stands must be kept devoid of techni- calities as far as possible if it is to expand and gain still further favor. Devotees of the radio-phone look upon the broadcasting service just as they would the phono- graph. When they purchase a phonograph they do not have to learn how the records are made, what makes one record better than another, what the rate of vibration is for the various instruments recorded on a given record, what is the wave form of each instrument as impressed on the record, and so on. Their interest starts and ends with the desire to hear music. And, notwithstanding the intricacies of the radiophone, they look upon the radio- phone in exactly the same way. Radio Without A Struggle — ^Can it be Done? Let us have no illusions on the subject. Radio is a difficult and intricate branch of engineering; indeed, it represents the highest technique in applied electricity. Hence it becomes impossible to give real, helpful informa- tion on radio reception and transmission, yet steer clear of such formidable terms as variometers, condensers, regenerative circuits, logarithmic decrement, damped and continuous oscillations, and so on. However, it can all be explained in a simple and elementary way, and it must be done. That, precisely, is the purpose of this book. RADIO FOR EVERYBODY 3 Starting out with the very rudiments of the art, you, the reader, are to be introduced step by step to the various phases of the radio art until you have mastered the essen- tial elements of the subject. Then, should you desire to delve deeper into this most interesting of hobbies, you can readily turn to the more advanced works which are now available in large numbers. To begin with, radio communication, whether it be the radio-phone or the radiogram, is based on a cause and an effect, separated by a greater or less distance. The cause is the transmitter, which sets up certain disturbances or waves in space which travel in all directions until they reach the distant point and create the desired effect, which is the result obtained with the receiving set. In the instance of the radio-phone service, the cause is the radio-phone broadcasting station. There are a number of such stations located in various parts of the United States; indeed, virtually every section of the country is now served with music, news of the day, weather forecasts, crop and market reports, and so on. The radio-phone station sets up disturbances or waves in space which travel in all directions. These disturbances or waves may be intercepted at any point within the range of the station, and when so intercepted can be brought to suitable receiving instruments and reconverted into the original sounds of the music or talk, as the case may be, so as to give a faithful rendition to the radio audi- ence. That is the effect. Now, just how the disturbances are set up and how they travel through space is still a problematical matter. Until Einstein came along and upset many of our pet theories with which we had explained so many things during several generations past, it was usually held that a radio transmitter set up vibrations or wave motions in ether. Ether is the name given to a hypothetical sub- stance held to exist everywhere, even in a vacuum. But with the ether explanation rendered more or less obso- lete by the said Einstein, as well as by certain astronomi- 4 RADIO FOR EVERYBODY cal experiments which have produced interesting and tell- ing results by way of confirming Einstein's theories, our pet radio explanation has been rather shattered. Still, for all practical purposes we can state that cer- tain kinds of waves of an electromagnetic character are produced by a radio transmitter, and that these waves travel through space at 186,000 miles per second. These waves, too, have much the same characteristics as the waves which we call light, except as regards their wave length and as regards their frequency of vibration. Whereas the waves of visible light have a length to be measured in niillionths of a millimeter, and a frequency of vibration of billions per second, the waves used in radio work are seldom less than 100 metres in length, and may be as long as 20,000 meters or more in the case of long-distance, high-power transmitters such as span the Atlantic. At the same time the frequency of radio waves is to be measured in millions down to thousands per sec- ond. These radio waves pass through space and pretty much through everything that stands in their way. They pass through stone walls, frame buildings, mountains, forests, and so on. Certain things, particularly masses of metal such as a huge steel structure, absorb a consid- erable volume of the radio waves, especially those of short wave length, but there is always a sufficient volume left to affect all receiving sets within range. The radio waves are everywhere, yet cannot be seen or felt. Without a receiving set it is impossible to tell if the air is permeated with radio traffic or whether it is absolutely barren. So far as is known, even the strongest radio waves have no direct effect on any of the five senses, which are the sole avenues whereby we ap- preciate anything that is external to ourselves. Directly, we cannot feel, hear, smell, taste or see the radio waves. While it is true that the eye is a detector of electro- magnetic waves such as light consists of, still, the unaided eye can only detect the very short waves of visible light which, as already mentioned, are minutely short and are RADIO FOR EVERYBODY 5 all contained within the narrow limits of a single octave ; and while by means of certain luminous screens known as fluorescent screens the range of visibility can to some extent be increased, no such method will render visible even the shortest of the waves used in radio. Radio and the Pond of Still Water Other methods have had to be developed to detect radio waves. These methods intercept the radio waves and convert them into some form of energy which will come within the scope of our senses. The receiving set presents the usual means of converting radio waves into sound waves which affect the human ear. Now let us consider a pond of still water as space, in order to follow the formation and propagation of radio waves. When a pebble is thrown into the smooth water it starts a series of concentric ripples or waves, which spread out indefinitely with a speed of a few hundreths of a yard per second, Similarly, the electro-magnetic disturbance set up by a radio transmitter spreads out in all directions in ever increasing circles, at the astounding speed of 186,000 miles per second — virtually instantane- ous, in the practical sense. As the waves spread out over the pool, little bits of straw or grass may be seen to move as the waves reach them. These bits of straw or grass may be compared with the radio receiving sta- tions which are also afTected as the radio waves reach them. It will be noted that the waves in the pond grow weaker as they extend farther and farther away from the point where the pebble was thrown into the water. The same thing occurs in radio ; as the waves spread farther and farther away from the transmitter, they become weaker until they no longer have sufficient power to actu- ate a receiving set. Here, then, is an important pomt to bear in mind. The waves become weaker with dis- tance. Thus at a short distance from a powerful trans- mitter, a relatively crude receiving set can be employed to 6 RADIO FOR EVERYBODY detect the powerful waves. At a greater distance, the same relatively crude receiving set no longer responds to the attenuated waves. At a still greater distance the waves are so weak that they do not produce proper re- sponse in better receiving sets, and it becomes necessary to resort to some form of amplifying device for the pur- pose of building up the strength of the waves in order to obtain the proper degree of audibility. All of which indicates that the question of distance in radio communication is governed by several factors. Be- ginners in radio will insist on being informed how far this receiver will work and how far that trarjsmitter can send, and they are always disappointed when told that questions such as these are not answerable. First of all, a receiving set cannot determine the distance over which it will receive. From a powerful transmitter it may re- ceive over a distance of 1,000 miles, but from a small amateur transmitter it may receive over a distance of only 25 miles. It is the transmitter, then, that determines the receiving range. On the other hand, the transmitter may actuate a high-grade receiving set at a distance of 1,000 miles, but a cheap set will not be actuated at a greater dis- tance than 100 miles. Again, atmospheric conditions have much to do with the range. Under ideal conditions the dis- tances covered may be three times the usual spans. Hence in all questions of receiving or transmitting ranges, it is necessary to take the receiving set, the transmitter, and the atmospheric conditions into consideration in order to obtain a satisfactory answer. There is no definite range for any given instrument ; specific conditions at any given moment decide the range. Otherwise, all statements of ranges must be approximations of a very crude sort. The Important Question of Wave Length Returning to the pool of water, it will be noted that the waves in spreading out from the transmitter maintain a certain distance between themselves. If the distance from the crest of one wave to the crest of another is RADIO FOR EVERYBODY 7 measured, we obtain the wave length, as in a — b in the accompanying sketch. In the case of the waves in water, the w^ave length is determined by the size of the stone, the wave length being greater when a larger stone is dropped into the water. In radio, however, the wave length has nothing to do with the size of the transmitter, although it is true that short wave lengths are employed for the smaller amateur transmitters, and longer wave lengths for the commercial stations, especially the huge transatlantic stations. While the waves are larger and therefore more powerful when a large transmitter is em- ployed, the wave length is determined by other factors as will be explained further on. What happens when a pebble and a large stone are dropped in still water. Note how^ the pebble causes small waves, and the large stone large waves. Measured from crest to crest. such as a — b, we obtain the wave length of the waves. The wave length determines the tuning of the trans- mitter and receiver alike. Tuning is such a confusing term to the layman, yet nothing could be simpler to understand. Tuning is nothing more than the adjusting of a receiver or transmitter to a given wave length, so that it will receive that wave length, in the case of the receiver, and transmit that wave length, in the case of the transmitter. Thus a transmitter is adiusted to 8 RADIO FOR EVERYBODY 200-meter wave length. The waves emitted by that trans- mitter are of 200 meters wave length. As they travel through space in all directions, they are intercepted by receiving sets. However, only those receiving sets that are tuned to 200-meter wave length receive the signals from the transmitter in question. Other receiving sets. tuned to a shorter or longer wave length, do not respond. On the other hand, if another transmitter is sending at the same time on a 600-meter wave length, then the first batch of receiving sets, adjusted to 200-meter wave length, will not respond to this second transmitter but will keep right on receiving from the 200-meter wave length transmitter. Other receivers, adjusted to the 600- meter wave length, will receive from the second trans- mitter, and so it goes. It is tuning that has made practical radio communi- cation possible. Were it not for tuned waves, it would be impossible for more than one transmitter to operate in a given area, for the simple reason that confusion would result if other transmitters operated at the same time. Now, with tuned waves, several transmitters can operate at the same time, and the receiving sets can be adjusted so that only the desired transmitters are inter- cepted and heard. Thus the radio broadcasting stations generally operate on 360-meter wave length. Amateur transmitters are by law limited to 200-meter wave length or less. Commercial stations operate on higher wave lengths. By dividing the wave 'length field into various classes, a 'minimum of interference results between trans- mitters. One can spend an entire evening listening to a radio-phone broadcasting station with hardly any inter- ference from radio /telegraph stations, thanks to the 360 meter wave length reserved for radio-phone service. Another question which rather confuses the beginner in radio is whether there is a limit to the number of receiving stations that can listen in to a transmitter. As a matter of fact, there is no limit — at least in practice. Any number of receiving stations can be operating at the RADIO FOR EVERYBODY 9 same time, picking up the signals or music from one transmitter. Furthermore, the transmitting operator can- not tell how many receiving sets are listening to what he is sending. He simply sends, and there is no telling how far his signals are going or how many persons are listen- ing in. Damped and Undamped Waves — Which? The waves dealt with so far in the pool of water are highly damped. Which means, in plain language, that The difference between damped or discontinuous waves, and undamped or continuous Avaves in water. Dropping a pebble into water causes damped waves, while using a paddle steadily produces continuous waves. they die down quickly. The pebble is dropped in the pool of water, and the waves created reach but a short distance away before they have virtually disappeared. In order to keep up a disturbance in the water, it is necessary to drop one pebble after another, so as to create a steady supply of waves, represented by groups or trains. Each group or train soon dies down, and is fol- lowed by the next one, and so on. In radio, we have the same condition when the usual spark transmitter is employed. The group or train of waves starts out strong but soon dies down, and a second train of waves must be started, only to die in the same manner. Such damped waves may be likened to the ac- tion of a pendulum. When the pendulum is given a push, it swings from side to side, but each swing is a trifle shorter than the preceding one, until the pendulum comes to a dead stop. Its action is damped, in other 10 RADIO FOR EVERYBODY words, and corresponds precisely to the action of damped radio transmitters. Of late years the undamped transmitter has gained much favor in radio. Unlike the damped transmitter, the undamped type produces a steady flow of waves. There are no groups or trains. It is just as though a paddle were used in the pool of water, said paddle being worked back and forth so as to produce a steady series of waves, all of the same size and strength, with a uniform wave length maintained throughout. Or again, as though the pendulum were given a fresh push at each swing, so as to restore the initial energy, and in that manner it would not die down just so long as the energy was supplied. Undamped wave transmitters are employed in many commercial and amateur transmitters. They are also known as continuous wave transmitters or CW trans- mitters for short. Radio telephony is always carried on by means of a continuous wave or undamped wave trans- mitter. In the case of the undamped wave telegraph transmitter, the steady flow of waves is altered into short and long trains to represent the dots and dashes of the telegraph code. In the case of the radio telephone, how- ever, the steady supply of waves is modulated or varied by means of a telephone microphone, such as the trans- mitter of the usual telephone instrument, in order to impress the characteristics of music or speech on the con- tinuous waves. Electricity may be made to vibrate or oscillate and it is this vibration or oscillation that creates radio waves. Cur- rent from a storage battery or dry battery flows steadily and only in one direction. Current flows out of one ter- minal of the battery, through the circuit, and back to the other terminal of the battery. That is direct current. However, there is another form of current known as al- ternating current, which is generated by machines known as alternators, and by other methods. Alternating current does not flow steadily, nor does it maintain the same RADIO FOR EVERYBODY 11 direction of flow. At one instant the alternating current is flowing through the circuit in one direction, and the next instant it is flowing in the opposite direction, only to change back to the first direction the next insiant, and so on. Each complete change of direction is known as a cycle. Commercial alternating current, which is generally used for lighting and power purposes in most sections of the country today, is known as 60-cycle current; that is to say, it has gone through 60 cycles of change in one second, each cycle consisting of a rise in positive voltage from to the maximum voltage and a fall to zero, and then a reversal with a negative rise in voltage from to -the maximum voltage, and back to again, and a repetition of the performance for the next cycle. Vibrating or oscillating currents of this kind are neces- sary to produce radio waves. However, the rate of vi- bration or oscillation, or the frequency, to use the radio term, must be of a much higher order than the 60-cycle frequency of lighting and power circuits. Thus the 200- meter wave length of the usual amateur transmitter repre- sents 1,500,000 cycles per second, while the 10,000-meter wave length of a highpower station- represents 30,000 cycles per second*. It will be noted that the frequency or number of cycles ^er second determines the wave length. The frequency, on the other hand, in both the receiver and the transmitter is determined by two factors, known as inductance and capacity. Inductance is the length of conductor in a circuit, so far as the layman is concerned, and we must keep to simple explanations in this work if we are to live up to its title. Thus if we have 100 feet of wire in a cir- cuit, we have four times as much inductance as in the same kind of wire 25 feet long. Inductance, for the sake of convenience, is generally arranged in the form of a spiral or a helix for the transmitter, using heavy conductor since the current being handled is rather a powerful one; for receiving purposes, on the other hand, the inductance is in the form of insulated wire wound 12 RADIO FOR EVERYBODY on tubes or wound in compact spools or coils for ready handling. The capacity is the ability of the circuit to store elec- tricity. Capacity is generally represented by a condenser, which is a reservoir or storage for electricity. In fact, the condenser is a real reservoir or storage for electricity. The storage battery is something entirely different, al- though it does serve to store electricity. It accomplishes this end by causing certain chemical changes, and these chemical changes in turn generate electric current which may be drawn from the battery until it is restored to its original chemical condition, or completely discharged. Thus the current proper is not stored : it only serves to create certain chemical conditions. For most practical purposes, however, the storage battery is the only means available for storing ordinary current. The condenser is always made up of sheets of brass, aluminum, copper or tinfoil, separated by some non-con- ductor of electricity, referred to as the dielectric. A cer- tain number of metallic sheets are connected to one side of a circuit, while the same number of metallic sheets are con- nected to the other side. The non-conducting material or dielectric separates two sets of sheets.. Between the sheets of metal there is created a static pressure. This pressure accumulates or becomes greater until the con- denser, no longer capable of retaining the pressure, dis- charges the accumulated electricity back through the cir- cuit of which it forms part. The discharged current flows through the circuit from one set of plates to the other, and recharges the condenser with the opposite polarity. No sooner is the recharging accomplished, when the condenser discharges again, this time in the opposite or original direction, of course, and so it goes, until the charge, getting weaker with each discharge, is entirely spent. All this can take place in a fraction of a second. Thus the discharge from a condenser takes the form of a vibrating current or oscillating current, which is the basis of radio waves. RADIO FOR EVERYBODY 13 The Antenna or Aerial Let us return for a moment to our pond of still water. Instead of a pebble, let us use a hinged paddle which can be moved back and forth to create waves. This paddle then becomes the agency for transferring power to the pool, which is the medium for distributing the waves. In radio the energy for creating the waves is generated by the transmitter, and a system of elevated and insu- lated wires, known as the aerial, serves to impart the energy or waves into space. An aerial or, as it is more popularly called in the case of the receiving end of radio, an antenna, is employed at the receiving end to inter- cept the waves and to bring the energy down to the receiving set. The receiving antenna may be likened to a hinged paddle at some remote point from the first paddle creating weaves in water. The receiving paddle is pro- vided with a bell. As the waves travel over the pond and finally reach the receiving paddle, they cause the paddle to sway and this action, in turn, rings the bell. This action is precisely that of the receiving antenna and the actuating of the receiving set. Aside from the aerial or the antenna, a ground con- nection is required in radio communication. The ground side means a good connection with any object that runs into the ground, such as a water pipe or a gas pipe, or even some object which is eventually connected with the ground, such as steam-heating pipe. In the country, where such pipes are not available, a good ground may be secured by fastening a wire to a bucket which is dropped into a well or other body of water. Again, an iron rod may be driven down into moist soil, or a large sheet of copper or gal- vanized iron may be buried in moist soil. However, the securing of a good ground, as well as the construction of the aerial or antenna, is reserved for other chapters. In reality, the aerial and the ground form a con- denser. The aerial and the ground are the plates of the condenser, while the space between is the non-conductor or insulator or dielectric, whichever you wish to call it. To 14 RADIO FOR EVERYBODY create radio waves it is necessary to have two surfaces separated by a distance of from ten to several hundred feet and to create between them an electric pressure which changes its direction first toward one surface, then toward the other. In other words, we must have a condenser effect. The current must change direction several thou- sand times per second. The aerial and the ground af- ford just such an arrangement, and between these we create an electric pressure of from one to 20,000 volts by means of a suitable transmitting equipment, which starts waves radiating out in all directions. These pres- sure waves are, however, only part of a radio wave. From any wire in which current is flowing electro-mag- netic waves are radiated ; therefore, radio waves are made up of both electro-magnetic and pressure electro-static waves. The creation of these waves may be compared to the action of hurling the pebble into the pond of still water, as already explained. The amperes (the measure of current flow) put into the aerial corresponds to the size of the pebble, while the volts (the pressure or poten- tial of an electric current) are equivalent to the force with which the pebble is hurled. The larger the pebble and the greater the force behind it, the bigger the splash and the consequent waves. The more amperes of cur- rent flowing in the aerial circuit and the greater the pressure in volts between the aerial and the ground, the stronger the waves radiated and the farther they will travel. Elements of Radio Communication So far, so good. In order to make use of radio waves for the practical purposes of sending messages and then receiving them at a distant point, it is necessary: (a) To produce regular electrical disturbances in a circuit which starts the waves. These disturbances are electrical currents which reverse rapidly in direction, or vibrate, so to speak. In radio parlance this characteris- tic is known as oscillating, and we speak of transmitting RADIO FOR EVERYBODY 15 circuits as oscillating- circuits, and of transmitters as os- cillators. The rapidity of the reversal determines the wave length, as we have already learned. ■(b) To get the waves into surrounding space, through which they travel with great speed. This is done by means of the transmitting aerial, which will be described further on. (r) By means of these waves, to set up electric cur- rents in a receiving circuit at a distant station. The device which these waves strikes as they come in, and which turns them over to the receiving circuit, is called the receiving antenna or aerial. (d) To change these currents so that they may be detected by suitable apparatus. The operator usually re- ceives the messages through sounds in a telephone re- ceiver. There are various ways in which radio waves may be set up. The simplest consists of a spark coil, such as the type employed in automobile ignition systems ; a con- denser represented by the aerial and the ground, and a soark gap arranged as shown in the accompanying diagram. The spark coil has two windings, namely, a primary and a secondary. To the primary coil, which consists of a rela- tively small number of turns of wire wound about the iron core of the coil, are connected the battery supply- ing the initial current and the vibrator or interrupter, which breaks up the current flow from the battery. The secondary consists of a large number of turns of wire wound over the primary winding. In the nature of elec- trical things, when current is passed through the primary, a high voltage current is produced in the secondary wind- ing. The primary current may be only six volts, but the secondary winding produces perhaps 5 to 10,000 volts. This stepping up of the voltage is a necessary part of radio transmitting. Transformers are larger devices in- tended for stepping up the voltage of heavy currents. At any rate, high volta?e current is produced in the secondary winding. The interrupter causes the secondary 16 RADIO FOR EVERYBODY to flow first in one direction, and then in the other, as the primary current is interrupted. The secondary cur- rent, flowing- for a moment in one direction, charges the condenser, consisting of aerial and ground. However, the capacity of the condenser is limited, and when it is charged to overflowing, it releases its energy which jumps the spark gap in the form of a fat spark, only to pile up on the other side of the condenser. Again the con- denser is filled to overflowing, and it discharges once more, this time causing the current to flow in a direction Ground The essentials of transmitting radio signals, comprising a spark coil, aerial, ground, spark gap, key, and battery, as well as an inductance coil for tuning purposes. opposite to that of the first time, and again the condenser is charged. Thus the discharges take place back and forth, but far faster than it takes to explain their action here. Indeed, the discharges travel back and forth with the speed of light, but gradually diminish in strength until RADIO FOR EVERYBODY 17 the charge is exhausted. Every time the vibrator in the primary circuit makes or breaks the current in the prim- ary, one of these trains of alternating- current or oscilla- tory current is started. Since they die down rapidly, they are known as damped oscillations. Each one of these trains produces a single tick in the distant receiving station telephone, and it is the rapidity with which these trains follow one another that characterizes the "spark" or sound of a transmitter. If we increase the capacity or the inductance in the transmitting circuit, we increase the wave length, just as the increasing of the length or the weight of the pendulum affects its rate of swing. In actual practice the transmitter is connected to the aerial and ground. The oscillations charge the aerial and the ground, which act just as a huge condenser, as already explained. The longer the aerial, the longer the wave length of the aerial by itself. This is known as its natural wave length, as distinguished from what its wave length may be raised to or lower to by external capacity and inductance. The waves travel out from the aerial through space, and through the ground to the various re- ceiving stations. These waves can be intercepted at any point within range of the transmitting station. Obviously, the waves become weaker as they travel out from the transmitter. A short distance away, the waves may be intercepted by an inexpensive and relatively crude receiving set, but at a greater distance, when the waves are considerably weaker, a more elaborate and more sensitive receiving set must be employed. For receiving the waves, an antenna and a ground con- nection are necessary. The first step is to tune the an- tenna-ground circuit so as to bring it into harmony or resonance with the desired waves. When this is done, the waves flow down from the antenna to the ground. They may be diverted into suitable receiving apparatus by the s^'mple arrangement shown in the accompanying il- lustr^ 'ion. However, even when they are diverted in this 18 RADIO FOR EVERYBODY manner, they are of frequencies of the order of several thousand cycles, and will not produce any sounds in the usual telephone receiver because they are beyond the range of audibility. But remember, the waves are in trains or groups. By making use of a device that can convert these trains or groups into direct current — current flowing in only one direction, we secure a series of im- pulses flowing in one direction. The device which accom- plishes this purpose is known as the detector. The current flowing through the telephone receiver is smoothed out into single impulses of a frequency corresponding to the An+enna Ground The essentials of receiving radio signals, comprising tiie an- tenna, inductance coil for tuning, crystal detector, telepliones, and tlie ground. speed of the vibrator or current supply at the transmit- ting end. Thus the diaphragm of the telephone is actu- ated at an audible frequency. In the case of undamped waves, which are produced in a different manner and received by more elaborate re- ceiving equipment, it is also necessary to bring the inter- cepted waves down to audibility. In the reception of con- tinuous wave radio telephony, however, the waves are modulated or altered by the impressed telephonic char- acteristics, and while the receiver may not make the actual RADIO FOR EVERYBODY 19 waves themselves audible because of their high frequen- cies, it does make audible the fluctuating potential of the waves and reproduces the sounds uttered at the trans- mitter. In other words, it does not concern itself with the carrier waves, but only with the sounds carried. Fitting the Radio Apparatus to the Task in Hand In entering upon radio as a hobby, the beginner is confronted with a question of choice of apparatus. Thus he can buy the parts and build his own receiving set and transmitter; he can buy the separate pieces of apparatus, Diagrammatic explanation of why a "detector detects radio waves. Tlie liigh frequency current produced by tlie inter- cepted wave is shown in the upper half of the diagram, Tvhile the lower half shows how the detector, being a one-way conductor, only permits half the current to flow^ through, therefore making it a direct current, which affects the tele- phone reeiver. Certain factors cause the individual pulsations of a wave train or group to slur into one note in the tele- phone receiver. Therefore, there is one sound for each train or group of waves. all finished and ready to be connected with other instru- ments so as to form a complete set ; or he can buy a com- plete receiving set and sending set, all wired, ready to be used. Latterly, because of the popular interest in radio, there have appeared various types of phonograph-like receiving sets, in which the radio mechanism is so simple that virtually no knowledge of radio is required. If the layman is only interested in receiving radio- phone service, and does not care to be troubled with even 20 RADIO FOR EVERYBODY an elementary knowledge of radio, then by all means the simplest type of apparatus is urged. In that event it is well to purchase a complete receiving set, already wired, as self-contained as possible, which only needs to be con- nected to the aerial and ground for immediate results. If the layman wishes to do a little experimenting and little by little master the details of radio communication, then it may be well for him to purchase separate radio units, each one finished but so arranged as to permit its use with other units for all kinds of purposes. Finally, if the layman wishes to build his own receiving set not only because of the experience gained but also on the grounds of economy, then the various parts can A simple receiving set, consisting of a variable inductance, a crystal detector, and a pair of telephones. Such a set will re- ceive radiophone concerts over 25 miles and perhaps more with good conditions obtaining. be purchased and assembled. Some manufacturers today offer all the parts for a complete receiving set, thus facili- tating work of this kind. For transmitting work, the same applies. However, it is well to say here that transmitting is something quite different from receiving. Anyone can receive, without RADIO FOR EVERYBODY 21 licenses or other formality ; but one must obtain licenses for transmitting. The transmitting station must be licensed by the Department of Commerce, as explained in another chapter, and the operator of such a station must pass an examination in sending and receiving in order to obtain an operator's license, without which one is barred from transmitting work. So, all in all, the layman had best confine his efforts to receiving only until some subse- quent time when he can afford to put in the necessary time to master the various details of radio in order to pass the Government test and obtain his operator's license. The growth of radio-phone broadcasting has created a demand for simple receiving sets with the minimum of controls and adjustments. Thus there have appeared re- ceiving sets made in the form of phonographs which repre- sent an effort to cater to the desires of persons who want the radio-phone service with all the radio left out, so to speak. These sets must be developed to a high state of perfection in short order, but for the present they must be looked upon as being somewhat premature at- tempts. In fact, much of the receiving apparatus which is now on the market is designed for radio communication work rather than for radio-phone broadcasting work, and this applies particularly to those sets making use of large horns for throwing the sound out into a room, in place of the head 'phones. The time must come when such sets will be designed with special attention given to the acoustical properties of the various components, just as the better types of phonographs have been consistently developed through unceasing experimentation and re- search until they have been taken out of the talking ma- chine class. For short ranges, inexpensive radio receiving sets can be obtained. There are sets selling as low as $15.00, which give passable results with the broadcasting station but ten miles or so away. For $25.00 there are several receiving sets available which give good reception of radio-phone service up to 25 miles or more. These sets 23 RADIO FOR EVERY/BODY are quite simple, having only one or two controls for varing the wave length, and a simple detector of the so- called crystal type. Such a detector, as will be explained further on in the chapter dealing with receiving appara- tus, requires no battery current. Stepping beyond the 25-mile range, we come to the bet- ter kinds of receiving sets with more elaborate tuning devices and the so-called vacuum tube detector. This detector, unlike the simple crystal detector, requires two The interchangeable panel idea is quite popular at present. ICach component of a receiving set is mounted on a standardized panel, and as many panels as are desired can be used at one time with or without cabinets. The idea is quite similar to the sectional bookcase, which grows with one's needs. batteries for its operation. It must have a low-voltage battery, giving from 1>4 to 6 volts, depending on the type employed, and a high-voltage battery giving from 15 to 22 >4 volts. The low- voltage battery is known as RADIO FOR EVERYBODY 23 A or filament battery, because it operates the filament just as in the case of an ordinary electric light, while the B battery or plate battery has to do with the intricate workings of the tube. In one type of receiving set sell- ing for $75.00, and quite effective for ranges up to 75 miles, a special 1^-volt tube is employed which can be operated on a single dry cell. Otherwise, the usual vacuum tube requires a storage battery because it draws over one ampere of current at a voltage of 6. Passing on to ranges over 100 miles, a still better set is required. We now reach a point where radio begins to cost real money. Figuring on the basis of $1.00 per mile, which is the figure generally quoted by conservative radio men, we come to sets of elaborate design costing upwards of $100.00, with numerous ac- cessories bringing the total cost up to $200 and $300. These sets are generally used in connection with what is known as an amplifier, which is a device for building up the weak signals or music or talk. The amplifier may be obtained in the one-step, in the two-step, or in the three-step models. Generally, the two-step model is em- ployed, for the reason that it gives an amplification of several hundred times the original signal strength, and does not cause too many foreign noises. Amplifiers make use of vacuum tubes, which in general appearance are very much like the detector tubes. They differ only in the vacuum content of the tube. Since the amplifiers magnify all sounds and irregularities in a circuit of which they form part, it stands to reason that everything is amplified together. For this reason the amplifier should only be used when the signal strength is quite low and must be increased for proper reception. Furthermore, amplifiers must be used in connection with loud-speaking telephones. It is often necessary to use the usual two-step amplifier, and then a separate amplifier for the loud- speaker when extremely loud music or talk is required for a large hall. At this point it becomes necessary to study the various 24 RADIO FOR EVERYBODY terms encountered in radio work, as well as the accom- panying diagram giving the various symbols showing how the different pieces of apparatus are designated in the wiring diagrams that follow. The author had wished to avoid all wiring diagrams, but found that there was no other manner in which specific information concerning the arrangement of radio apparatus, could be given. Simple transmitting and receiving sets could be shown in more pictorial form, but when the more advanced equip- ment is to be shown we must resort to the conventional wiring diagrams. However, a little attention given to these symbols will enable even the layman to master the art of reading a radio wiring diagram, and he then be- comes competent to read any wiring diagram to his very substantial benefit. The most common terms employed in everyday radio work are as follows : Aerial — ^One or more wires insulated from and sus- pended at a certain height above the ground and used to radiate energy in the form of electric-mag- netic waves produced by a transmitter. When used for receiving purposes, the correct name is antenna, though both terms are used interchangeably for either reception or transmission. Alternating Current, (Abbreviated A. C.) — An electrical current whose direction of flow is constantly chang- ing during a period of time. Thus, when we speak of a 60-cycle alternating current, we mean one that com- pletely reverses its direction of flow sixty times per second. Alternating current plays a prominent part in many phases of the radio art. Ammeter — An instrument used for measuring the flow of current in amperes through a given circuit. Ai ammeter is invariably connected in series with a given circuit, so that the current has to flow through it. Sometimes, the current is passed through a heavy conductor placed across the ammeter proper, such a Aliernator Ammeter Aerial Arc Batferu Bu zz&r T-t 1 — i|.|.|.|,|.l.|.h- Condenser — ] | — or -l^j_ Variable Condenser -4^ Connection of wires — \— No connection — p — Coupled coils § e Variable couplina WW Detector — }< — Galvanometer "(G)— Gap, plain « « Gap, cjuenched llllll Generator. D. C- O (c)rou*^ci ■==■ |i|i | i|i '| Grid leak and J^TL Condenser Inductance -^vwnn— Variable Inductance or Resistance — ww* — Variable resistance — ww^ Single pole ^^^ Switches Single throw"^ Single pole _^.^^ ^_ Double throw Double pole ^^^;"— Single, throw ~^ Double pole __'>v>. __ Double throw — "^ — Reversing I^^^^C Telepkone Receiver florc^^ Telephone Tronsmitter i(Jj Tra n sf o r m e r 1 Q i_ Vacuum Tube Variometer Voltmeter -- standard symbols used in radio wiring diagrams. These symbols should be mastered so that the radio devotee can understand wiring diagrams and follow out their instructions. 26 RADIO FOR EVERYBODY conductor is known as a shunt, and permits of handling heavy currents. Ampere — The standard electrical unit of current flow. Amplifier — This term is used in referring to either an amplifier tube or an amplifier receiving unit. It is the device which builds up or magnifies the waves or sounds in a radio receiving set. (See vacuum tube.) Amplitude — In radio work, this refers to the highest point reached by a wave or oscillation, i. e., the crest of each wave. A wave may, therefore, have a high or low amplitude according to the initial energy which created it. Antenna — See aerial. Armstrong Circuit — See Regenerative Circuit. Atmospherics — Also known as static, strays, X's. "The noises of space." Natural electrical discharges oc- curring in the ether and in reality miniature lightning storms. Since these discharges travel through the same medium as radio waves, they are readily picked up by receivers and prove very troublesome at times. It is comparatively difficult to tune out these dis turbances for they have no definite wave length. Audio Frequencies — Frequencies corresponding to vibra- tions which are normally audible to the human ear. All frequencies below 10,000 cycles per second are termed audio frequencies. (See radio frequencies.) B Battery — The battery used for supplying the plate current for the vacuum tube. This battery generally runs from 15 volts to 22^^ volts. Broadcasting — As applied to radio work, this stands for the simultaneous sending of intelligence either by radio telegraphy or telephony from a given central point for the benefit of a great number of receiving stations located within the broadcasting station's range. Capacity, (abbreviated C) — Capacity as used in radio work plays a very important part. The unit of elec- RADIO FOR EVERYBODY 2t trical capacity is the Farad, but the farad being too large for practical radio work, the micro-farad (ab- breviated m. f. d. — one millionth of a farad) is used. Thus we speak of a receiving or transmitting con- denser having a capacity of .001 mfd, or one thou- sandth part of a microfarad. Cascade Amplification — This refers to high amplification of received radio signals, wherein several vacuum tubes are employed in cascade fashion which means that one amplifies the sounds or waves and passes ANTENiNA LEAD ^^k.'-.'^ , •-.-^ ^ ■ TUNiNG COIL. i^i yr 8Af?E: WtRE, WlNOlNe CRYSTAL DETECTOR TUNING cost, St-iDER Receiving: set of simple construction, making use of a tuning: coil with single slider, a crystal detector, and a single telephone receiver. This set may be used for short distances. them on to another, which amplifies the sounds and passes them on to another, and so on. Thus, we may speak of a three-step (cascade) amplifier. Choke Coil — A coil wound to have great self-induction or choking efifect when in the path of alternating cur- 28 RADIO FOR EVERYBODY rent. Choking action when introduced in a radio cir- cuit is called impedance. Circuit — In radio and electrical work the path in which an electric current flows is called a circuit. A circuit may be open or closed or oscillating. Close Coupling — A tuning coil, set of coils, or a trans- former is saiid to be close-coupled when the primary and the secondary are very close together, thereby causing much mutual inductance. Coupling permits of the transference of energy from one circuit to an- other. Therefore, the closer the coupling, the greater the transference of energy and the interplay of the circuits. The primary of any coupler or transformer device is the winding which carries the initial cur- rent; the secondary is the winding which receives its current from the primary. In a coupler the primary is connected to antenna and ground, and the second- ary is connected with the detector circuit. Condenser — Two or more sheets of metal separated by an insulator called the dielectric. A condenser is used in radio work for collecting electrical energy, and for bringing circuits into tune or resonance. Counterpoise — One or more wires stretched immediately above the earth, but insulated from the earth. The counterpoise wires are usually directly beneath the regular aerial. This device is employed in trans- mission and reception when a good ground connection is not available. The counterpoise is used in aircraft radios, where a ground connection would be out of the question. It is also used extensively in continu- ous wave transmission. Continuous Wave, (Abbreviated C. W.)^ — A form of elec- tro-magnetic wave used extensively in radio work. C. W. waves have a constant amplitude and by the same sign no damping effect, as distinguished from the older form of discontinuous waves which are soon damped out. C. W. makes possible long-distance amateur radio telegraphy, as well as radio telephony. RADIO FOR EVERYBODY 29 Coupler — A device for transferring radio energy from one circuit to another. Ordinarily, the primary winding of the coupler is connected with the antenna VI ^^^^^^H^Hn 1 -^ . b r 5 "~^"''N!\G " -^ Mg- '^|ij|ili||iHM{WiBiBltB^ K3"3^V AND w-^r , .1 '^l^fl^BBHlBBllillii^^ Hfi^^^K, Tjs-' ''-~-^j|BpWMWwyi!!!WmliHli*«<»^^ I^HsiBMk 1 iBHBMllliWi' iii'iii Ill I'll' B^^g^ ^^^^^^B^^^m ^~-^^^^^H B^HWi|^ ^■H^^^^^PIP.^'?^ ^»M«^ I^^M*** -^'-'^S B|^H[^H^^^^^>^|^g 1,'v- iSE ^KBB^^maB!^,^' ^.^T^FSB-^ i. W^lwi^A^^WS' 1 tv'^B W^Sl^^^^^^^^^^m^l- ■ as-M M^S^^^B^^^^^^m m^^'t^^m- ■ HH^^^^I^^^^^V^'^^.w.w'Mm^ ..I'!-. k»«Ms»-;s'»^M hH'^' ^Wr^^^^™"-^' •%^:^5 ~-~«,'~;,a&So,.,*!a. '*™ H/«=^K ""'"^^ V| record' A^S'JMS 1 Receiving: set made in the form of a plionograph; in fact; this cabinet may be used as a phonogrraph or radio telephone receiv- ing- set at will. The radio set makes use of the phonograph horn. and ground, and the secondary with the detector circuit. Couplers are of several different types, such as the loose-coupler and vario-coupler. Crystal Detector — ^^Certain metallic crystals when intro- duced in a radio receiving circuit have the property of rectifying the incoming signal oscillations, which 30 RADIO FOR EVERYBODY are high frequency alternating currents, into direct current, so that the resultant intermittent direct cur- rent will work a sensitive telephone receiver. Detector — Any apparatus which transforms the oscilla- tions received by the antenna into visible or audible indications. Direct Current, (abbreviated D. C.) — An electric current flowing continuously in one direction. In a two-wire circuit, for example, direct current always flows from the positive source to the negative return. Therefore, direct current always has a readily de- terminable polarity, while alternating current (A. C), which is constantly reversing its polarity while flow- ing through a circuit, has no apparent polarity. Electron — The ultimate particle of negative electricity, which plays a fundamental part in the constitution of matter as well as in the electric current. Radio- active emanations, electric discharges, etc., consist of streams of electrons, ejected at immense velocities from the atoms of which they formed part; and ordinary electric currents are in some way an elec- tronic phenomenon. E. M. F. — Electromotive force or electrical pressure or potential, the unit of which is the volt. Ether — A hypothetical medium of great elasticity and extreme minuteness, supposed to pervade all space as well as the interior of solid bodies. It is the medium through which light, heat and radio waves have here- tofore been said to be transmitted. The Einstein theories have shattered the ether theory for the moment, however, although many radio men still cling to it in explaining radio transmission. Flat-Top Aerial — One whose suspended wires are stretched parallel to the earth. Frequency — In alternating currents, the rapid reversal of the current through a circuit. Thus, we speak of a 60-cycle current as one which has sixty complete re- versals per second or a frequency of 60 cycles. (See A huge radio receiving set and loud-speaker, made in the form of huge cabinet. Such a receiving set gives loud enough music to fill large hall or motion picture theatre. 32 RADIO FOR EVERYBODY Alternating Current and Audio and Radio Frequen- cies.) Grid Leak — A very high, non-inductive, resistance con- nected across the grid condenser or between the grid and the filament of a vacuum tube to permit exces- sive electrical charges to leak off to an external source, thus furnishing stable control under all opera- ting conditions. Ground, (or Earth which is the term used in England) — In radio work the ground is the other side of the wave distributing system. It functions in connection with the aerial or antenna of most sending and receiv- ing systems as a large condenser. The term "ground" is used for any connection with the earth, river or sea. (See counterpoise.) Harmonics — In radio, harmonics refer to the incidental waves mostly noticeable in undamped or C. W. wave operation. These harmonics differ in length and fre- quency to the true and original operative wave of such transmitters. The first harmonic is three times that of the true frequency, or one-third the wave length of the aerial; the second harmonic is five times the true frequency or one-fifth the wave length ; the third harmonic is seven times the true frequency or one-seventh the wave length. At times, amateurs will hear the harmonics of high power long wave stations while their tuners are set for much shorter waves. This accounts for the reception of a radio-phone sta- tion at two entirely different points on the tuner of the receiving set. Henry — The unit of inductance. Hertzian Waves — ^Electro-magnetic waves named after the discoverer, Prof. Heinrich Hertz, in 1887. These waves are the basis of radio communication. Hook-up — A diagram showing the wiring of any wireless receiving or transmitting set. Diagrams of this kind make use of certain conventional symbols to repre- sent the various pieces of apparatus. RADIO FOR EVERYBODY 33 Hot Wire Ammeter — An instrument used in radio trans- mission work for measuring the current in amperes by means of a wire that expands in proportion to the heat generated by the current passing through it. Impedance — This is the term apphed to the resistance offered by a coil of wire to a current flowing through it due to the counter-electromotive pressure, irre- spective of the actual resistance of the conductor in ohms. Counter-electromotive pressure is developed in certain forms of inductance, and this counteracts the flow of current to a greater or less degree. Impe- dance may be said to be the result of reactance. Inductance, (abbreviated L) — Inductance, like capacity, plays a very prominent part in radio circuits. It is the transfer of an electric or magnetic current from an electrified or magnified body to a non-electrified or non-magnetized body by close proximity but with- out actual contact. The unit of inductance is the Henry. In radio work the mil-Henry and the micro-Henry are the more practical terms used. Insulator — A non-conductive material through which electricity will not pass. Kilozmtt, (abbreviated K. VV.) — One thousand watts, a unit used in measuring large amounts of electricity. Loop Antenna — A small frame wound with a number of turns of wire used in reception and thus eHminating both outdoor antenna and ground connections. Loose-Coupler — (See Coupler.) Loud-speaker — Any receiving device designed to repro- duce signals or speech loud enough to be heard with- out the use of the conventional telephone receivers. Megohm — ^One million ohms. Microfarad, (abbreviated mfd.) — One millionth part of a Farad and the practical unit of capacity. Microphone — A device for converting sounds into elec- trical equivalents in a given circuit. In other words, the microphone transfers sounds to a given electrical circuit by causing certain variations in the flow of 34 RADIO FOR EVERYiBODY electricity. It is the instrument used in both wire and radio telephony to transmit speech, and generally consists of a mass of loosely packed carbon grains held between carbon blocks, and subjected to vary- ing pressure by the vibration of the diaphragm. Milliampere, (abbreviated M. A.) — The thousandth part of one ampere. Natural Frequency — The natural wave length obtained with any aerial or circuit without the introduction of other elements. Ohm — The unit of electrical resistance. Ohm's Law — The fundamental law of electricity. It states that the current in amperes flowing through a cir- cuit is equal to the pressure in volts divided by the resistance in Ohms. Oscillations — Alternating currents of very high frequen- cies are called electrical oscillations. If the amplitude of a series of oscillations is constant, the oscillations give rise to continuous or undamped waves ; but if the amplitude is not constant and is of a decaying nature, as in the spark method of transmission, we obtain damped waves. Potential — Term applied to voltage or electrical pressure. (See EMF and Volt.) Radiation — The transmission of energy through space in the form of electro-magnetic waves. By the radiation of a transmitter is meant the volume of high fre- quency current which is being delivered to the aerial for propagation in the form of waves. Radio Frequencies — Frequencies corresponding to vibra- tions not normally audible to the human ear. All frequencies above 10,000 cycles per second are termed radio frequencies. (See Audio Frequencies.) Reactance — See Impedance. Rectifier — An apparatus which converts alternating cur- rent (A. C.) into pulses of direct current (D. C.) Tungar, Rectigon and Kenetron apparatus are em- ployed for rectifying purposes. Certain metallic RADIO FOR EVERYBODY 36 crystals also have rectifying action when used as de- tectors in reception. Regenerative Circuit, (also known as the Armstrong cir- cuit) a radio circuit comprising a vacuum tube so connected that after detection and rectification, the signal introduced in the plate circuit is led back to or caused to react upon the grid circuit, thereby 'in- creasing the original energy of the signal received by the grid and greatly amplifying the response to weak signals. In reception, the leading back or feeding back of plate energy to the grid for further strength- ening is usually accomplished by means of a small coil placed close to the secondary of the receiving tuner. This small coil is frequently called the ''tickler." Resistance — 'Opposition to the flow of an electric current through a conducting medium. All metals have more or less electrical resistance. Copper is used univer- sally for both electrical and radio work on account of its low resistance, comparatively low cost and ready supply. Silver is a better conductor, but it is too expensive. The unit of resistance is the Ohm. Resonance — A very important function of radio circuits. Resonance in a given circuit is said to exiist when its natural frequency has the same value as the fre- quency of the alternating electromotive force intro- duced in it. The current is then in tune with the natural period of vibration of the circuit. The theory of electrical resonance is the same as that of acoustics, readily demonstrated by the tuning forks, where one tuning fork will not respond to another unless it is of the same key or pitch. Bringing a cir- cuit into resonance means bringing it into tune with another circuit or transmitter. Rheostat — ^A variable resistance usually employed to con- trol or regulate current flow. Selectivity — In radio work, the ability to select any par- 36 RADIO FOR EVERYBODY ticular wave length to the exclusion of others ; the fineness of tuning, in other words. Sharp Timing — Where a very slight change of a tuner or tuning system will produce a marked effect in the strength of signals. The sharper the tuning, the greater the selectivity. Storage Battery — Battery which can be recharged at inter- vals whenever it is run down; a storage battery is employed to supply .current for operating vacuum tube filaments. Static, (See Atmospherics) — Disturbances of an electrical nature which are created by natural causes and which interfere materially with radio work. When static is exceptionally bad it may be impossible to receive radio telegraph signals or radio-phone service through the heavy crashes and frying sound of the static. Transformer — Any device used in electrical and radio work for the transference of energ}^ from one circuit to another, with or without a change in the voltage as desired. Thus we have Power Transformers, Am- plifying Transformers, Telephone Transformers, Os- cillation Transformers, Tuning Transformers, etc. All transformers have a primary and a secondary winding. The primary winding receives the initial current, which it passes on to the secondary winding, with the same voltage, a higher voltage, or a lower voltage, according to the ratio which the primary and secondary windings bear to one another. Tuning — The act of altering capacity or inductive values or both in a radio circuit so as to bring the circuit into resonance with an external source of similar character. In radio receiving, the greatest signal strength is possible only when the combined induc- tance and capacity values of the receiver match those of the transmitter. Undamped — A train of high frequency oscillations of constant amplitude such as continuous waves or C. W. Vacuum Tube, (abbreviated V. T.) — In radio work this RADIO FOR EVERYBODY 37 term is applied to a glass tube exhausted of air and containing essentially a filament for the creation of electrons ; a plate, positively charged, to which the electrons are attracted ; and a grid, consisting of a helix of fine wire, inserted between the filament and the plate, for controlling the amount of electronic flow. This action of the vacuum tube plays three leading functions in radio work, namely, detection, amplification, and generation of high-frequency elec- tro-magnetic waves. Vario-Coiipler — (See Coupler. ) Variometer — An instrument which serves to vary the in- ductance and wave length value of any circuit in which it may be used. It consists of a set of fixed windings and a set of movable windings, the latter being rotated on twin axis in the usual construction. When both sets of coils carry the current flow in the same direction, the variometer has the maximum inductance value or wave length. When the coils are turned around so that the current flow in both sets of coils is in opposite directions, the coils are said to be ''bucking" each other and the inductance and wave length value are at a minimum. Velocity of Waves — Radio, electricity and light waves travel through space at the speed of 186,000 miles per second, or 300,000 meters per second. J^olt, (abbreviated V.) — The unit of electric pressure. Voltmeter — An instrument for measuring the voltage of a current flowing through an electric circuit. JVaff, (abbreviated W.) — The unit of electric power. To find power in Watts multiply voltage by amperage. 746 Watts equals one horsepower. 1,000 Watts equals one kilowatt (K. W.) Wave Length — Radio waves in their passage through the ether, travel in undulating wave form sim/ilar to the waves at a seashore. When the wind is blowing hard and steady the distance between each wave crest is comparatively long while if the wind is blowing more 38 RADIO FOR EVERYBODY mildly and in short spurts, the distance between wave crests is accordingly shorter and we have short waves. In radio, substitute the wind for the transmitter and you have the same action, so to speak. Wave length is, therefore, closely related to frequency, ' i. e., long wave lengths have low natural frequencies while short wave lengths have greater natural frequencies. In general, short wave lengths are used for short distance low-power work, while long wave lengths are employed for long-distance, high-power work. The foregoing list by no means covers all the terms which will be encountered in radio, but it covers the more common and perhaps least understood terms con- fronting the layman at the very outset. As one gets along ever so little in the radio art, one accumulates a vocabu- lary of radio terms quite readily and with no effort. After all, radio is a subject which one soon masters. It is relatively simple after the essentials are clearly under- stood. Furthermore, in no other line of endeavor will one find so much good fellowship and so many oppor- tunities of receiving a helping hand. In all parts of the country there are radio amateurs who are ever ready to extend a helping hand to the novice, and one will do well to get in touch with the radio amateurs of the vicinity at the earliest possible moment. They are the greatest asset the novice has at his disposal. Furthermore, the radio and electrical dealers handling radio equipment are always ready to extend all possible co-operation and information to those in need of radio aid. It is part of their service ; for, in purchasing radio apparatus, one is seeking a definite service rather than so much equipment. The reader is advised to keep in touch with radio devel- opments by reading the various periodicals devoted to the subject, as v/ell as the radio sections of the various news- papers now paying special attention to the greatest hobby of the age. A real fund of valuable information can be picked up in this manner, especially after acquiring the very necessary fundamentals of the art, the imparting of which is the purpose of this book. Chapter II. RADIO-PHONE BROADCASTING WHAT IT IS AND WHAT IT MEANS ^ ^ T ADIES and gentlemen, we take great pleasure in I J introducing Mr. Percy Grainger, the famous pianist and composer, who will entertain us this evening with several of his favorite pianoforte selections. After that, please stand by until 9.55 for the re-transmission of the Arlington time signals " A concert? No. A vaudeville performance? Hardly. A musicale in the home of a society leader? Not this time. It is merely a bit of radio-phone service taken at ran- dom. Another time it might be Mme. Lydia Lipkovska, court singer to the late Czar of Russia, or Miss Valentina Crispi, violinist, or Miss Sophie Tucker, famous delin- eator of darky and character songs. Again it might be Governor Edward I. Edwards of New Jersey, with his latest message, or Ed. Wynn and the entire company of "The Perfect Fool," representing the first attempt to broadcast an entire theatrical performance ; or Walter Camp, foremost authority in American athletics. The Radio Voice and its Audience Still again, at a different hour of the day, it may be the news of the moment, carefullv selected and clearly heralded word by word ; marine news, weather reports, children's bedtime stories, health talks, business talks, 40 RADIO FOR EVERYBODY fashion talks, agricultural reports, Babson's statistical service, or the official time signals. For the radio-phone service is unlimited in its scope of subjects, just as it is virtually unlimited in the size of its audience. But what is the radio-phone service? Where is it obtainable, and how? What does it cost? Why is it free? Typical questions, these, at a time when radio is at the height of popularity. Only a short while back, the hobby of radio was indulged in by boys and voune^ men, with occasionally a full-grown man, who, perhaps, were more fascinated by the technicalities of .the radio art than by the actual feat of communication through space. Yet it is true that these enthusiasts, then as now, were carrying on radio conversations among themselves by means of the dot-and-dash language of the telegraph code; but it was certainly evident that they spent a goodly part of their time arranging and rearranging their radio trans- mitters and receivers in their insatiable ambition to span greater distances. Then came the radio-phone service, not as an occasional thing to startle the radio amateurs already engaged in sending and listening to the dot-dash messages, but as a regitlar established practice. A subsequent development brought about a definite operating schedule and a pre- determined program, so that now the person with a radio receiving set knows what is in store for him tonight, to- morrow night, or even next Sunday evening. Radio- phone programs are printed and mailed to persons on the mailing list of the various organizations doino^ this kind of work. In various cities throughout the country there are radio- phone broadcasting stations now in operation, which send out all kinds of information, talks, and music. With the proper type of receiving equipment it is now possible for any one to receive the raSio-phone service from the nearest station, and, if there are several stations within receiving range, it is often possible to receive several radio-phone services, one by one, with absolute selectivity, although they may be operating simultaneously. That is to say. RADIO FOR EVERYBODY 41 with the apparatus properly tuned, one station may be heard ; then, by slightly altering the tuning, another station may be picked up, and so on. Further tuning may pick up an amateur radio-phone transmitter or a commercial The radio-phone receiving set finds a ready place in every pro- gressive home. 3Iany an hour can be spent listening to the musical programs, news of the day, weather forecasts, talks by prominent men, and other radio-phone broadcasting features. Station operating or "talking'' in the dot-dash-dot language of the Continental telegraph code, or again a powerful transatlantic station transmitting its messages at an ex- treme rate of speed, thanks to automatic transmitters at 42 RADIO FOR EVERYBODY one end and the photographic or phonographic recorders at the receiving end. Radio-phone broadcasting stations are sharply tuned; in fact, all radio-phone transmitters are sharply tuned ; for, as we shall learn further on, this is one of the cardinal points in favor of the continuous wave transmitter, which is the basis of the radio-phone. Thus the utmost selec- tivity is obtained at the receiving end, and interference is reduced to a minimum. Indeed, the day is not far distant when a broadcasting station will be sending various serv- ices simultaneously, ranging all the way from a sermon to a jazz dance piece, and from a talk on economics to a fashion chat. The listener wil! merely have to tune his or her receiver to any one of several wave lengths in order to obtain the desired service at that time. Back to the Humble Beginning There is no end of romance in the story of the radio- phone, radio telephone, or wireless telephone, whichever you please to call it. It is an invention that came back, so to speak, in a big way after an ignominious career. Such a wonderful thing — this idea of speaking through space without wires, cables, tubes or other physical con- nections — was almost certain to fall in the hands of un- scrupulous promoters, long before the serious, honest ex- perimenters had had a-n opportunity of evolving something more than a crude, laboratory demonstration. So a dozen years ago we find the radio telephone nothing more than a crude device, making use of a sputtering, uncertain electric arc as the generator of the high-frequency energy. This high-frequency current, so uncertain as to be almost hopeless, was modulated or varied by means of some form of carbon microphone. This instrument, as any one familiar with its construction must know by now, is quite unsuited to the handling of heavy currents. It consists of little more than a mass of tiny carbon granules held between two carbon members. The passage of a heavy current through such a mass causes the carbon granules to fry or bake because of the heat developed through the imperfect contacts. 44 RADIO FOR EVERYBODY It was the good fortune of the author to participate in wireless telephony back in 1908 and 1909, with a trans- mitter of the Telefunken type made in Germany. A series of experiments were being conducted for the United States Signal Corps, with a view to proving the practicability of radio telephony in military communication. The dis- tance to be spanned was some 18 miles, or the air line between Foi't Hancock, Sandy Hook and Fort Wood. Bedloes Island, in the very shadow of the Statue of Lib- erty overlooking New York harbor. The high hills of Staten Island intervened, making communication between the two points all the more difficult. For the transmitter we were using ten electric arcs, arranged in series and suppHed with a 550-volt direct current. Each arc consisted of a copper tank, filled with water, and a large carbon button. The ten arcs were arranged in two banks of five arcs each, and each bank was struck or started at the same time by pressing a single handle controlling five arcs at a time. Three sensitive ammeters indicated the state of each circuit — the input circuit, the closed oscillating circuit, and the antenna cir- cuit. The main object in this little game of wireless telephony was to get the three circuits, as reported by the meters, to behave — and what a job ! No sooner was one circuit tamed, so to speak, so that the needle of its meter remained practically stationary, when attention would have to be given to the other two circuits whose meters were playing all kinds of antics. Then, at the moment when by mere chance all three meters were more or less steady, we were ready to talk. There was little to say, because if we were heard at the receiving end, it was more of a miracle than anything else. So we simply shouted numbers into the huge horn connected with the carbon microphone— "One. two, three, four," and so on, followed by "Fort Wood, Fort Wood : how do you get me now? One, tw^o, three, four," and so on again, until the meters began their antics once more. Occasionally we played a phonograph, just as did so many other radio telephone workers in the pioneer days. RADIO FOR EVERYBODY 45 The microphone was a renewable affair. The German builders of the apparatus, with all their characteristic thoroughness and fine workmanship, made the microphone in the form of simple cartridges which fitted into a holder at the small end of a long but narrow cardboard horn. E^ch mi'crophone did not last much longer than five minutes after which it was little more than plain junk. While the author never knew the exact cost of these microphone cartridges, it is a. safe bet that they cost at least $2.00 each. Imagine wasting a $2.00 microphone for every five minutes of uncertain telephonic communi- cation ! Insurmountable Obstacles That Were Forgotten What of the results? Rotten, absolutely rotten! In all the long months of untiring efforts to work over the short eighteen-mile span between Fort Hancock and Fort Wood, the voice and the phonographic music only got through a half-dozen times, and then only for a few mo- ments so that odd bits of conversation or music were heard by the Signal Corps officers gathered at the receiv- ing end. There were many workers engaged in solving the wire- less telephone problem. Most of them used the arc gen- erator, following in the footsteps of the Danish scientist, Poulsen. Some used high-frequen'cy alternators, but the design of these early machines was such as to give a low degree of efficiency. Nothing like reliable communication seemed possible, for the technical obstacles w^ere far too great and too numerous. But ail the while certain stock promoters were reaping a harvest. To them, the wireless telephone presented an exceptional opportunity. The ever-credulous public liked the word pictures of the wireless telephone as painted by the clever stock salesman. The story of the Bell telephone was to be duplicated, but on a larger scale ; wireless tele- phones were to be installed in every home ; wires and cables were to be done away with ; every one would carry a wireless telephone about in one's vest pocket or hand- 46 RADIO FOR EVERYBODY bag, so as to ensure immediate communication with any one else, and so on. What a vivid picture, to be sure! Even at this late day, with the marvelous development that has taken place in wireless telephony, such a picture is quite out of keeping with what we can reasonably expect for decades to come. In fact, so long as the present sys- tem of wireless telephony is in force, it is doubtful if we can ever realize all the remarkable things that were prom- ised to the gullible stock purchasers of but a decade or more ago. Of course there were proofs. There had to be some- thing for the public to take interest in this latest scientific development, especially to the extent of parting with so much hard-earned money. Thus there was a demonstra- tion of the radio telephone between two of our cities. Everything worked to perfection. The results were abso- lutely wonderful. The public was enchanted, nothing less ; but the true scientists and radio workers were completely baffled. Then, when certain interests were closely inves- tigated, an unpaid bill for the leasing of a telegraph line between said two cities on a certain date, came to light. Needless to say, the date corresponded with that of the successful test of the wireless telephone. The inference is obvious. Another time, it was a German company's turn to make a demonstration for the German army. The test was to be bd:ween Berlin and another city over one hundred miles away. Although nothing of much consequence had ever been done with this particular German wireless telephone system, on this occasion it worked like a charm. An in- quisitive German officer, seeking some explanation for the sudden upward jump in the radius covered by the wireless telephone, not to forget the remarkable clearness and loud- ness of the received conversation, suddenly discovered a telegraph line running direct between the transmitting station and the receiving station. There was no physical connection between the two, please be sure to note ; but the transmitting aerial was parallel to and but a short distance away from the telegraph line at one end, while the ^t = O B %c. * 5* fll OSS lis IK^^^^^Mg r^^M f^~n M f'^ •- ,s • ^^^^^wi^ .:J '■liiilBiiililssM^^ ■ : i!S?;?!lis;fc: :.: :. :y5i'vi|ii; ■ ii 1 ■ /|j^ip Bp''' iiiiils-f'jis >■ "^ W ^^^^^wis- "!* * SSiiiiSftiB iilf lifiyk:^,^ ^'-^''"^ ■IWi^-^^^ - . "■"■*^ w\ %t' . ; , ^ . ; '^1' ■■ **^ ■ '■' ^jft^^^S y: , , ; " ., ;:^B|P^"''"'' ^ ri 48 RADIO FOR EVERYBODY receiving antenna was parallel to and but a short distance away from the direct telegraph line at the other end. As far as wireless waves are concerned, there could be little gained by having a direct connection. It was scarcely more than straight wire telephony, except for the short jump at either end. In fact, this form of wireless tele- phony has, strangely enough, come to be used during the past year or two for transmitting telephone messages over high-power transmission lines. It is also used in wire work in a somewhat modified form, being known as "wired wireless," as will be explained farther on. When a Rival Became a Partner And' skipping over the numerous attempts to make something out of- this remarkable laboratory toy, the wire- less telephone, we come to the time when the American Telephone and Telegraph Company took an interest in the vacuum tube perfected by Lee de Forest, as is explained elsewhere in this work. In the vacuum tube the telephone engineers realized that they had found a solution to many of their problems. The vacuum tube is nothing short of an electrical acrobat; it can do all sorts of tricks which no other electrical device has ever been able to perform. Thus it is a wonderful alternating current generator ; feed it direct current and it gives forth alternating current of a wide range of frequencies. It is this characteristic which makes it available for wireless transmission purposes. Feed it alternating current, and it delivers direct current. This characteristic, just the reverse from the preceding one, makes it available as a rectifier for charging storage batteries, and, some day in the near future, as a substitute 'for the elaborate and costly rotary converter units now necessary in electrical transmission work, for converting alternating current used in high-voltage transmission, back into direct current of suitable voltage for commercial use. Feed it high-frequency alternating current, such as radio waves, and it converts them into audible pulsating currents which affect telephone receivers and thus are converted into audible sounds. That is how it is used as a detector. RADIO FOR EVERYBODY 49 Feed it ever so slight a fluctuating current, and it will con- trol or modulate or modify a far more powerful current; thus we have the weak current moulding a powerful cur- rent, and it is this feature which gives us the amplifier. It is this characteristic, too, that makes the vacuum tuhe the finest telephonic relay ever devised. It is used in long- distance telephone communication, so that the voice cur- rents, when greatly attenuated after traveling over hun- dreds of miles of wire, are Ijrought to the grid memher The farmer, using an inexpensive radio receiving set, can now keep in touch with the outside Avorld. He hears the latest musical "hits," and he receives weather forecasts, crop reports, and other information of real A^alue. of the vacuum tube, and there serve to control a fresh and far more powerful current which starts ofif on the next lap of the journey, only to reach another vacuum tube when it in turn has become weak as a result of a long stretch. Again, the vacuum tube, because of its modu- lating characteristic, is the link between the carbon micro- phone or telephone transmitter of the ordinary kind, and the powerful currents of the radio telephone transmitter. At a stroke it eliminates all the troubles that seemed im- 50 RADIO FOR EVERYBODY possible of solution back in the early days of the wireless telephone. It was in 1915 that definite progress was first recorded in the history of the wireless telephone, for it was during the latter part of that year that the engineers of the Amer- ican Telephone and Telegraph Company succeeded in telephoning by wireless between Arlington, Va., and the Eiffd Tower, in Paris, or over a distance of three thou- sand miles. Over three hundred vacuum tubes were em- ployed to generate and modulate the high frequency cur- rent employed to span the Atlantic expanse. During the same tests the voice was carried through space all the way to Pearl Harbor, in the Hawaiian Islands, or a distance of almost five thousand miles. Do not forget that the stock promoters, back in the days when wireless telephony seemed so impossible to the really wise men, were telling us that the wireless tele- phone would be the great rival of the wire telephone. The wire telephone would certainly be put out of business in due course. Yet it was only when the engineers of the wire telephone came to take an interest in wireless tele- phony that this art made real progress. What is more, they developed wireless telephony to something practical; and the wireless telephone, in turn, gave wire telephony the vacuum tube and other valuable devices which made long-distance telephony practical. So instead of proving rivals, these two great means of communication have come to be partners, and always will remain partners. The Radio Link in Our Telephone System Came the war, with still greater progress. Radio tele- phony on a small scale had to be perfected, because instant communication had to be made available between airplane units and the ground posts. When the United States entered the war, the best radio talent was put to work on this problem, with the result that the radio telephone in small units as well as large units, became a reality. Today it is possible to obtain a radio telephone of 5-watt rating capable of transmitting over a distance of five to fifteen g.?-? B ? ""t^ SO 3 ^^.^ «:§ srs-* as * p frSo fc!* ^r Ji-a H a » S ^^a %*^ o » ?: S IP Hi S.'S 2lE S3? if o,^ RADIO FOR EVERYBODY WLEKLY PROGRAM RADIO-PHONE SERVICE WESTINGHOUSE ELECTRIC & Mf g Co. STATION W J Z. NEWARK. N. J. I MON., DEC. 12th, TO SUN., DEC. 18th, 1921. I This program can be heard by any one with suitable radio receiving apparatus within a radius of 100 miles of Newark. The service is absolutely free. Tune Instruments for 360-meter waves. REGULAR CONCERT DAILY, 8:20 to 9:25 P. M. MONDAY - - - Mme. May Peterson, Prima Donna Soprano, Opera Comique, Paris TUESDAY - .- - Os-Ke-Non-Ton, Indian Bar- itone; Messrs. Bertram Haigh and Ralph Brown, French horns; Miss Anita Wolf, Pianist WEDNESDAY -Mme, Gretchen Hood, Prima Donna Soprano, Theatre de la Monnai, Brussels THURSDAY - - Miss Helen Davis, Soprano; M. Cliff Young, Pianist FRIDAY - - - Westminister Orchestra SATURDAY - Dartce music SUNDAY - - Miss Ethel Mackey, Soprano and Miss Mary Emerson, Pianist. Sacred Music OTHER FEATURES General News - - Newark Sunday Call News Service, daily, 7:55 P. M. Children's Hour - - "Man-in-the-Moon" stories, by Miss Josephine Lawrence © Newark Sunday Call 'Tuesday and Friday, 7:00 P. M. Hourly News Service - - Newark Sunday Call; weekdays, every hour from 11.00 A. M. to 7:00 P.M. on the hour Radio Amateurs' Night - - Thursday 7 P. M. J. B. WALKER editor Scientific American Weather Forecast (Official Gov't) - - Daily, 11:00 A. M., 5:00 and 10:03 P. M. Marine News - - Marine Engineering Service, weekdays (except Saturdays), 2:05 P. M. Official Arlington Time - - Daily,, 9:55 P. M. (Program subject to change) One of the first programs of the radio- phone broadcasting: service. Compare this program with one of the present programs reproduced on facing page. miles, as well as a 5 00- watt transmitter capable of spanning 500 miles or more. The war made radio telephony what it is : it was not an ill wind, for it blew some good. Today, the radio telephone is part and parcel of our wire telephone system, and it is fast becoming as practical in its true field as the latter. In- deed, were it not for the high cost of this form of communica- tion, it would be quite within the scope of present achievement for any telephone sub- scriber to call up a relative or friend on an ocean liner several hundred miles out at sea, the voice being carried over the usual telephone line to the central ofifice, through trunk lines to the dis- tant radio transmitter, and thence transmitted through the air to the steamer. Two-way conversation could be effected, as with our usual telephone sys- tem. The radio link, RADIO TELEPHONE BROADCASTING PROGRAM AVa' York Cllu DIslrirt SUN., B. 12th,TOSUN.,FEB.19th, Sunday 3 P. M.— Rndio-Chapel sen-ices, "The Spirit of Lincoln in a R.idio-Unified World", by Rev. Ec'par Swan Wicrs. D.D., assisted by the quar- tette—Mrs. Wm. M. Rockwell, Mrs. M. S. Powell, Fred P. Taylor and George Roubaud; F. F. Kuxham, orpanist — from Uie Unitarian Church, Mcntclair, N. J. 4 P. M. — "Abraham Lincoln", an address by Rev. Robert Scott Inglis, of Newark, \. J. 4.S0 P. M.— 'My Country 'Tis of Thee". "Star Spanded B.-^nner"; also several popular selections, including -Ty Tee", "All That I Need Is You"; ployed by Paul 'U'hitehian's Orchestra, from the Palais RoyrI, New York. Arranged through the courtesy of Leo Feist, Inc. 7.00 P. M.— Sacred Music played by the Aeolian Orchestrelle. 8.00 P. ^L— "Listen to Me", "Sweet Lady", "Hawaiian Blues", and several other selections from Carleton's Tangerine, by members of the Tangerine Company, accompanied by the Casino Theatre Orchestra. Arranged through the cour- tesj' of Leo Feist, Inc. Monday 2.S0 P. M.— Ray- Miller's Record Orchestra, assis- ted by Cliff "Ukelele Ike" Edwards. 8.15 P. ^L— Miss Ethel Grow, contralto, who ap- peared in English Opera and Concert, and in Oratorio in England, under the direction of Sir Henry Wood. 8.-15 P. M.— Gustav O. Homberger, cellist of the Kaltenborn String Quartette, who appeared in concert with the leading orchestras of Europe as solo cellist under Von Bulow, Rubinstein, Weingartner and Richard Strauss. Mr. Horn- berger will play a programme of selections by Goltermann, Chcpin, and Moskowski. Tuesday 7 P.M. — "Man-in-the-Moon" stories for children. 7.45 P. M. — "Tuberculosis, Influenza and Com- mon Colds", a preventive lecture by Dr. Charles J. Hatfield, Managing Director of the National Tuberculosis .Association. 8.00 P M. — .\n address on radio by Paul F. Godley. 8.20 P. M. — A second recital to the radio-phone audierce by Mme. Gretchen Hood, Prima Donna Soprano, Theatre De La Monnair, Brussels; also of the San Carlo Opera Company, and prominent concert singer. Her program includes "Seger- bella" from Carmen, Bizet, and a group of bal- lads. Courtfsy of Aeolian Company. 8.45 P. M. — '.'Che Gelida Manina" from the Opera Boheme, Buccini, etc., ty Charles Harrison, Tenor Soloist, Fifth Avenue Brick Presbj'terian Church, for four years; studied with Frederick Bristol. 9.20 P. M. — Songs and readings by Mr. and Mrs. E. E. HoUe, of Newark, N. J. Wednesday 8.15 P. M. — ^Descriptive recital with music, of Verdi's opera, "D Trovatore." Thursday 7.45 P. M — "Modern Health Problems", an ad- dress bv Dr. Royal S. Copeland, Commission- er of 'Health. New York Citv. 8.00 P. M.— "TMiat is a Rotary Club and ^"hat Are its Relations to the Public" by Allan Smith, THUR.SDAY (conlimied) Ex-President of the Newark Rotary Club. Also a rotary song by Andrew Krenrich. 8.20 P. M.— Classical music. O.iO P. M. — A program of songs by Janet Bush-. Hecht, contralto soloist, First Congregational Church, Montclair, N. J., and a prize winner in a Newark Music Festival Contest. The program includes "In Flanders Fields", "Would You," "Bubbles", and "Joyous Youth", composition, of Mabelanna Corby, who will be the accompanist for these and other selections. Courtesy, Aeolian Company. Friday 7.00 — "Man-in-the-Moon" stories for children. 8.15 P. M.— "Party Night," when several well- known artists of vaudeville and the musical com- edy stage will entertain with songs and mono- logues. Saturday 7.00 P. M.— Irv Pages Cornell Orchestra, Cornell University, composed of the following: Irv Page, banjo; Geo. Cox, banjo; Lyman Breese, banjo; Sam Bird, traps and drums; Jack Wallace, saxa- phone; and Paul Miller, cornet, banjo and violin. 7.45 P. M.— "Fa.shion Talks to Women", Mar- jorie Wells, N. Y'. World. 8.00 P. M.— The "Daily Dozen" exercises address, by Walter Camp, foremost authority in, American athletics. 8.20 P. M.— Dance Music by the Femwood Dance Orchestra of Newark, N. J. 9.20 P. M. — Popular and character songs by Ailcen Stanley, soprano, well-known in vaudeville circles. 9.45 P. M.— "Hello Prosperity", "Don't Leave Me Mammy", etc., by Max Hitrig, dramatic tenor, known from Coast to Coast. Duo Art Piano Recital. Sunday 3 P. M.— Radio-Chapel Services, Rev. Clarence H. Wilson, D.D., Glen Ridge Congregational Church. 4 P. M. — "Boys of the World", an address by C. R. Scott, State Secretary of Boys' Work, Y. M. C. A., Newark, N. J. Music by quartette including Miss May Korb, soprano soloist, South Park Presbyterian Church; jVIiss Marian Adams, contralto soloist. Church of the Redeemer; Bruce Campbell, tenor, and Louis Burke, baritone, Clin- ton Avenue Reform Church. 6 P. M. — Program of classical, music by Mrs. Robt. Baldwin, ^■ioli^ist and Mrs. Ernest H. Harder, pianist. 7.45 P. M. — Sacred Music recital by the Aeolian Orchestrelle. 8.00 P. j\I. — ^Ed Wynn and the entire company of "The Perfect Fool", now playing at Geo. M. Cohan's Theatre, New York. For the first time in the history of radio an attempt will be made to broadcast an entire theatrical performance. Ar- ranged by the N. Y'. Globe. OTHER FEATURES Musical Program wcelidays, every hour from 11 a.m, to 6 p. m. on the hour. "FASHIO.V TALKS TO WOMEN", MarjorieWetlB. N. T. World Ensineering BABSON'S Statistical Service. Monday. 8 P. M. OFFTCAL ARLINGTON TrME 9.52 P. M. AGRICULTURAL REPORTS. Official, daily 12.00 M.. and 6.00P.M "MAN-IN-THE-MOON" stories by Miss Josephine Lawrence (©NewarkSundayCall). (■Program will be announced daily by radio pham 7.45 P. M.> A typical printed program of a single radio-phone broadcasting station. Such programs are mailed out to interested parties in order that one may know what to look for every evening of the forthcoming week. 54 RADIO FOR EVERYBODY as the radio telephone service is called when used in this manner, is destined to become commonplace within the next few years. Now the foregoing is no mere flight of fancy. It is a matter of record that the American Telephone and Tele- graph Company recently conducted a series of experiments with radio links and the trans-continental telephone line. Telephonic communication was established between the steamship ''Gloucester," cruising off Deal Beach, N. J., and Santa Catalina Island, situated some thirty miles off the California mainland in the vicinity of Long Beach. The telephonic communication, in this case, passed from the "Gloucester" to Deal Beach, N. J. ; from Deal Beach to New York via telephone line; from New York to San Francisco via trans-continental telephone line ; from San Francisco to Los xA.ngeles via telephone line ; from Los Angeles to Long Beach via telephone line ; and from Long Beach by radio to Pebbly Beach, on Santa Catalina Island, and from Pebbly Beach to the Avalon exchange. From ocean to ocean via radio, telephone line, radio again and telephone line, through all the various circuits without appreciable distortion ! The first commercial radio and connecting land toll line is the Santa Catalina Island and California radio link, which was set in operation the latter part of 1920. Radio telephone service between Santa Catalina and the main- land to connect up with the Bell system exchanges was installed at the request of the local telephone company. Catalina is one of the great tourist resorts in California. It attracts thousands of visitors daily throughout the year, who, heretofore, when they left the California main- land, remained completely isolated from the rest of the world until they returned to the mainland, except for the much overloaded naval radio telegraph station on the island. That this radio link, which bridges the 31^-mile gap between the island and the mainland, is not in the experi- mental stage may be gathered from the fact that it handles hundreds of messages each day. The large amount of 56 RADIO FOR EVERYBODY commercial traffic with scarcely any interruption which the Avalon-Los Angeles toll circuit has carried since its inauguration is ample proof of the practicability of toll lines containing radio links, where, due to physical condi- tions, direct-wire connections are impracticable. It is virtually impossible to delve deeply into the intrica- cies of the Avalon-Los Angeles radio link and wire cir- cuit, since it involves the moat elaborate telephone and radio engineering practice extant. Suffice it to state that the circuit consists of a little more than one mile of wire line from the Avalon central office to Pebbly Beach, a 31^-mile radio link to Long Beach, and 25 miles addi- tional wire circuit to Los Angeles. This combination wire and radio circuit is operated as a unit, providing through telephone and signalling from Avalon to Los Angeles. At Avalon the circuit may be connected to any local subscriber's line, and at Los Angeles to any local subscriber's line, through local exchanges, or with other long-distance lines reaching practically any subscriber in the Bell system. The radio link is a duplex system: one message may be sent in each direction simultaneously. For transmit- ting, a fair-sized aerial is employed, while for receiving a loop antenna is used at each end. These loops are of the solenoidal or helical type, six feet square, and consist of only four or five turns each. To make the duplex operation a success, it goes almost without saying that exceptional measures had to be taken, otherwise the trans- mitter at one end would drown out the incoming signals on the loop antenna but a short distance away. The elimi- nation of such interference was attained by the use of different carrier frequencies for transmission in the two directions. Great things can be expected of the radio link. Whereas it would otherwise be necessary for a person, desiring to telephone by wireless, to have a radio telephone trans- mitter of his own or to visit a radio telephone station, it now becomes possible to employ a distant radio telephone transmitter through any Bell system telephone. It is only 58 RADIO FOR EVERYBODY a matter of time when we shall talk over our telephone lines to our friends at sea, thanks to the radio link, although this service will always of necessity be expensive. How Radio-Phone Broadcasting Came About But the average reader of this book will no doubt be more interested in the radio-phone broadcasting develop- ment, which is a later-day phase. Before this broadcast- ing service became a regular thing, there were spasmodic efforts to send out musical programs, made by several radio companies, but these were intended rather as tests than as entertainment for tens of thousands of listeners. The present form of radio-phone broadcasting dates back to the latter part of 1920, when the Westinghouse Elec- tric and Manufacturing Company inaugurated the firsr radio-phone concert through its Pittsburgh station. Only a small number of persons heard the musical numbers sent out by KDKA, the Westinghouse station in Pitts- burgh. The phonograph was the only source of music, and the operator's announcements sufficed for lectures and talks. The novelty of the feat was sufficient, of course, for the public had not yet been pampered, so to say. Problems arose over the manner and method of broadcasting, which had to be solved by experiment. There were many times during the first few weeks of broadcasting when the concerts were anything but pleasant to the ear. Then, as time passed on and through experi- ence the operators found out for themselves the kind of phonograph records which transmitted clearly and those which did not, what to avoid in the way of speech, what pleased the public and what raised its ire, and the various other little details which made or marred a radio perform- ance, the concerts began to pick up not a little. During this experimental stage letters began to trickle in from various parts of the country, telling of the re- ception of music and talks from KDKA. At first, returns were small, and mostly replies from established stations, which are always on the lookout for new developments, in radio. These stations, by the way, lose no time in RADIO FOR EVERYBODY 59 corresponding with other stations they hear. After a time letters began to come from persons who had only recently purchased receiving sets, perhaps after hearing the concerts at one of the amateur stations. These lay- men increased in a steady stream and their number even at this writing increases steadily by leaps and bounds, Radio manufacturers are months behind in their produc- tion. Practically all the broadcasting by KDKA was pioneer- ing work. For instance, take the case of the radio church services. When the station was started, there was no program developed for Sunday evening. It was sug- gested that church services be tried. There was no prece- dent for this method of radio transmitting and conse- quently it was not known whether church services would broadcast well or, indeed, if the churches would consent to this method of handling their services. After some persuasion, however, permission was received from Cal- vary Episcopal Church of Pittsburgh, to broadcast its services. A district telephone line was installed between the church and the radio station for this purpose. Four microphones were installed in the church, to catch the voice of Edwin J. Van Etten, rector of the church, the choir, the chimes, and the organ, and the en- tire services were first sent out January 2nd, 1921. No one thing ever broadcasted by the radio station has been so popularly received. Letters poured in by the score to the Radio Division, telling of the pleasure and benefit of this new department in radio. Newspapers all over the country carried editorial announcements of the fact that church sermons were being broadcasted from Pittsburgh through the medium of the radio-phone. This was the first eflFort of its kind ; and it made the radio-phone safe for the future. From Canned Music to the Real Thing After a time, when the church services were well known to all radio enthusiasts because of the clearness of trans- mission, the Westinghouse Company was requested by 60 RADIO FOR EVERYBODY members of the Herron Avenue Presbyterian Church to install a receiving set and loud speaker to take the place of a long absent pastor. This was done, and the church assembled for an Episcopal service. But it listened to a sermon preached about fourteen miles away. This serv- ice, it goes without saying, was also a record, a milestone, if you please, since it was the first time two congrega- tions in separate churches had ever worshipped to one service, when a distance of miles separated them. It was also the first time that u metallic horn ever took the place of a flesh-and-blood minister. Again, this feat, al- most in the miracle class were it not for the fact that we have come to expect such marvelous things from modern science, attracted the attention of the press, with the result that more people than ever began to take an active inter- est in the radio telephone. In the meantime phonograph records comprised most of the evening musical programs. It was decided to do away as much as possible with the ''canned" music and substitute real singers and musicians. Talent was not hard to obtain for this work, in most cases volunteering its services. Human voices began to come over the radio telephone instead of records, and were an agreeable change. Again an improvement was made in radio broadcasting — another milestone. Not satisfied with having merely local talent, the Radio Division of the Westing^house orgfani- zation entered into an agreement with the managers of the local operatic concerts, with the result that when stars of the first magnitude came to Pittsburgh, their efforts, vocal and instrumental, were and are being broadcasted over hundreds of miles. Not only in opera, but in the world of sport, the radio-phone service has been introduced. Casting about for features that would enliven the evening programs, it was decided to 'broadcast, as an experiment, blow-by-blow^ returns of a boxing match held in Pittsburgh. A private wire was installed from a boxing club to the radio sta- tion, and a man prominent in sporting circles engaged to render a round-by-round version of the progress of the RADIO FOR EVERYBODY 61 fight. So KDKA was the first broadcasting station ever to send out fight returns. Afterwards, the Dempsey- Carpentier bout in Jersey City, N. J., was broadcasted by a Radio Corporation station round by round. But operatic engagements and boxing bouts do not cover the entire gamut of pubhc interest. So to the existing features there were added the news of the day, weather forecasts, agricultural reports, and other items of general interest, not to forget the occasional addresses by prominent men. In order to perfect the transmission of music and speeches by radio, the Westinghouse engineers have made considerable researches of the different frequencies of both. A studio has been built especially for the artists who sing, so that the radio-phone reproduction will be accur- ate. The studio in East Pittsburgh consists of a room :^0 by 30 feet, completely lined with burlap and devoid of windows, so that there w^ill be no reflection of sounds. A report is made of every song, where the singer stands, how far away from the transmitters, and other incidental details. This report is checked up later with a receiving station and from this data considerable information has been obtained regarding the transmission of various kinds of music. This is only by way of showing ho'w the new art has had to be developed, step by step. Extending the Broadcasting Area So successful did the East Pittsburgh radio-phone sta- tion prove and so great was the interest shown by the public and reflected by the unprecedented and even un- dreamed of demands for radio receiving equipment that the Westinghouse organization set to work opening up other broadcasting stations. At Newark, N. J., on the roof of the Company's plant, there was installed a power- ful broadcasting transmitter known as WJZ. Down on the first floor of the building there is an attractive studio, equipped with various musical instruments and hung with curtains to make it sound-proof. In this studio ar- tists have been singing and playing, while speakers have p aa'3 •IH e S to. 5 c -Ox §1 11 ^ o ■*^'^ fceg l» O ^ Jo Ms ^ a ^ a u u ft . =3W RADIO FOR EVERYBODY 63 delivered their messages, for the benefit of the greatest audience ever gathered at one time. It is estimated that over 300,000 persons hear the concerts and talks broad- casted by the Newark radio-phone station, and that the effective area covered by this service takes in one-tenth of our total population. The service of this station can be heard by anyone within a radius of 100 miles of Newark, though as a matter of fact reports of the re- ception of the musical numbers and talks have come from Canada, Wisconsin, Florida, Cuba, and 600 miles out at sea. Then there is the Springfield station, known as WBZ, which supplies New England with the Westinghouse radio-phone service. Another station has been established in Chicago, known as KWY, and is intended for the Middle West and the Western States. The W^estinghouse programs are of a high order and provide a wide variety of entertainment. Thus the New- ark station, WJZ, every evening from 8 :20 to 9 :15 broad- casts a concert with well-known operatic or concert stars frequently singing or playing in -person. At 8 :00 a digest of the day's news is sent out. An especially popular feature is the "Man-in-the-Moon" fairy tales for children. As this is written these bedtime stories are sent out on Tuesdays and Fridays at 7 :00 p. m. The stories delight the youngsters all over the reception area. At many of these parties the children are ushered into a darkened room just before 7 :00 p. m., and each is handed a tele- phone receiver connected with the receiving set. An illuminated moon lends atmosphere to the occasion. Sud- denly, out of the silence, comes a voice — "Hello children, are you listening? This is the Man-in-the-Moon" talking. What do you suppose I saw today?" — and a wonder-story follows, interspersed wnth musical selections. In addition, news bulletins are given out during the day, every hour on the hour; the official Government weather forecast is sent out three times a day ; and the official Arlington time signals are made available for amateur receivers at 9 :55 p. m., with the final dash at 64 RADIO FOR EVERYBODY 10 :00 sharp. Other features, such as election returns, bulletins of championship baseball and football games via direct telephone line from the fields, lectures by famous scientists, and so on, are given from time to time. These details are announced in advance over the radio-phone and are given in -weekly programs issued by the Company. Indeed, it is the certainty of the present radio-phone serv- ice that makes it so interesting. One can look forward to some definite evening because the musical program of that evening happens to be of most interest. It is very much like going to a concert or vaudeville ; for, while the actual performance cannot be seen, although it is clearly heard, this obstacle is perhaps more than counter- balanced in many instances by the fact that the audible side of the performance is brought right into the home. The Springfield station, in addition to many of the foregoing-mentioned features, sends out a periodical talk to farmers about market and stock conditions. The com- plete ^transmission of grand opera from the Chicago Opera Company productions has been the feature of the recently established station on the Commonwealth Edison Build- ing in Chicago. It is possible that the radio-phone in time wiH ht as popular in the home as the phonograph is today. But its destiny rests entirely in the hands of those who supply the broadcasting service, to be sure. Aside from the Westinghouse organization, there are other broadcasting stations. During the pioneer days of broadcasting the Radio Corporation of America's station at Roselle Park, N. J., known as WDY, did excellent work. At the time of this writing this station has been discontinued, leaving much of the broadcasting in the Middle Atlantic States to WJZ. The Roselle station was known for its operatic concerts, which included a lecture on the opera of the evening, together with the best selec- tions from that opera. Then there were the radio par- ties, which were made up of songs, talks, dialogues, mono- logues and other vaudeville features. There are various other organizations devoting a goodly part of their efforts to broadcasting radio-phone RADIO FOR EVERYBODY 65 news and concerts. In fact, as things stand at present it is safe to state here that virtually every part of the United States is covered by one or more stations. To give a list of stations is virtually impossible, for in an art that is so new there are bound to be frequent changes. Hence no attempt is being made to offer a list, because it would be hopelessly obsolete by the time it got into print. The reader is referred to the radio periodicals and to the daily newspapers that have radio sections, for the last- minute information on radio-phone stations. As it is, the WJZ or Newark station of the Westing- house organization is shortly going out of existence as this is being written. Word has gone out to the effect that the American Telephone & Telegraph Company, which is a factor in the Radio Corporation of America combine, is about to open a radio-phone broadcasting station on the roof of its 24-story building on Walker Street, New York City. Steel towers 100 feet high will support the aerial, and the station will be far more powder ful than WJZ which it is replacing. With an Eye to the Future ^ This radio broadcasting station will be unique in many respects. The distributing station is to be equipped with the latest developments of the Bell system, including the use of electrical filters and new methods whereby, as the business growls, several wave lengths can be sent out simul- taneously from the same point, so that the listening station may receive at will any one of several services sent out at the same time. The telephone organization will provide channels through which any one with whom it makes a contract can send out his own pragrams, just as the company leases its long-distance telephone wire facilities for the use of newspapers, banks, and other concerns. There have been many requests for such a service, not only from news- papers and entertainment agencies, but also from depart- ment stores and a great variety of business houses, ac- cording to a telephone official. (j6 radio for everybody The station when completed will cover a territory within a radius of from 100 to 150 miles of New York City, and imder particularly favorable conditions may be able to operate over a greater territory. It is estimated that more than 11,000,000 persons reside in the territory to be covered by the new plant. This is a new undertaking, true, and the fact is fully appreciated by the telephone organization. If there should appear to be a real field for such service and it can be furnished sufficiently free from interference in the ether from other radio services, it will be followed as cir- cumstances warrant by similar stations erected at impor- tant centers throughout the United States by the American Telephone and Telegraph Company. As these additional stations are erected, they can be connected by the toll and long-distance wires of the Bell system so that from any central point the same news, music or other program can be sent out simultaneously through all these stations by wire and radio with the greatest possible economy and without interference. While it is entirely possible, as has been demonstrated, to talk across the continent or even for much greater dis- tances over water by radio when all atmospheric conditions are favorable, such long-distance radio telephone trans- mission at present is not dependable and is not to be compared from a standpoint of service or economy with the transmission which is provided over wire. However, for a broadcasting service, which involves only one-way transmission, where the same message is given simultane- ously to a great number of people within reasonable dis- tances of the transmitting station, radio telephony offers a promising field for development. Heretofore, the broadcasting services have been sent out at considerable expense by the companies operating radio-phone stations, without charge to the sender or the receiver of the messages or music. However, it is abso- lutely obvious that the interest created in radio has been multiplied thousands of times by the radio-phone service, and there has sprung up a demand for radio receiving RADIO FOR EVERYBODY 67 apparatus that has exceeded the wildest expectations. Radio -manufacturers in many instances are months behind in their dehveries, and their greatest problem is produc- tion. This, mind you, at a time when practically every other line of business is searching every nook and corner for a buyer ! However, it must be obvious that this gratuitous service cannot continue indefinitely. A time must come when the radio market will be pretty well saturated, and it will no longer 'be attractive for companies to furnish free radio-phone service. No doubt by then the Government will be furnishing all kinds of news, such as agricultural reports, weather forecasts, official time signals, commer- cial reports, and so on by radio-phone, but there will still be a demand for musical entertainment. So, the way it seems now, the radio-phone service of the future must be a cross between a special publicity service and a free program. There will be free service, the same as now ; there will be musical numbers, news of the day, weather forecasts, and so on; but in addition there must be an occasional talk on the offerings of the leading department store, a subscription-'getting chat by the editor of a large magazine, a campaign speech by a candidate for public office, and so on. It will be the toll charged for such broadcasting service that will pay for the radio-phone concerts and news. It must come to that, sooner or later. Already department stores and others have planned and are going ahead with radio-phone transmitters, with the object of sending out entertainment, news, and their own particular brand of publicity. Interesting as this work may be, there is always a grave danger that it may be overdone. For, let it be remembered, there is only a limited amount of radio traffic that can 'be borne on the ether highways. It wouldn't take many radio-phone trans- mitters in any one locality to crowd each other so hard that a hopeless tangle would ensue. That is why the thought of radio-phone transmission, which is unfortun- ately so persistent with many amateurs and business or- .= SO s s2 — « 3 1* O fl s a ^ -t- :« o * .a o o aj h IB J- 2o« * c i « e <^ RADIO FOR EVERYBODY m ganizations, must be discouraged, particularly in crowded areas. The ether must be kept free and clear for the better class of radio-phone services. It must and will be a survival of the fittest, for the Government must step in and see that only those with a real service to offer are permitted to travel the ether highways, so long as our present knowledge of the art affords but a Hmited number of available wave lengths with which to operate. And at the Receiving End The radio-phone service of the present or the future is available to everyone provided with a suitable receiv- ing set. All that is necessary is some kind of aerial, which for this purpose may be a single wire, elevated 20 or more feet off the ground, and running longer than 100 feet if possible. About 150 feet is the best length, and there is no decided advantage in running a longer wire for the reason that the wave length of the radio-phone services is generally around 360 meters, and it is best to have the natural wave length of the aerial as near this value as possible. With a -much longer wire, it becomes necessary to insert a condenser in series, and this only reduces the efficiency of the aerial by that much. Hence 150 feet of ■wire is recommended. Aside from this simple aerial, a ground connection is necessary. For this purpose a con- nection may be made to a steam radiator pipe, water pipe, gas pipe, or to any object which is known to be connected with the ground in an efficient manner. In the country, where steam pipes, gas pipes and water pipes are not available, a good ground may be obtained by running a wire to a zinc or copper plate, and then burying the plate some six feet under the ground, in moist soil. Again, a wire may be connected to a pail which is lowered into a well or into a brook or lake. As will be explained in detail further on, the receiving set to use depends entirely on the distance between the receiving station and the broadcasting station. Thus within a 25-mile range, a simple receiving set will do. Beyond this range and up to 50 or 75 miles, a better re- •J'O ' RADIO FOR EVERYBODY ceiving set must be used, and it calls for a storage bat- tery or large dry battery to operate the vacuum tube detector which then replaces the crystal detector used for shorter ranges. For still greater ranges, a vacuum tube detector and a vacuum tube amplifier unit must be em- ployed, and the set then begins to mount up into con- siderable money. Even for short ranges, where a loud- speaking telephone is desired, an amplifier must be em- ployed, for it is the amplifier which builds up the radio waves so that they can be converted into loud sound waves and heard throughout a larger room, thus doing away with the necessity of wearing the usual head 'phones. There is nothing more facinating than listening to the radio-phone concert and service. One turns the tuning handle of the receiving set : short and long buzzes, fol- lowing each other in a lazy sort of way, indicate some amateur radio telegraph transrnitter at work. The tuning handle is turned a little more, and a peculiar moaning sound is heard. Turned still more, the sound becomes a weak voice or music, and a final turning of the handle brings in the radio-phone loud and clear. The tuning is exceedingly sharp. A slight turn one way or the other throws out the radio^phone altogether. The author, using a 60-foot wire as an aerial, running between the second floor of his house and a large tree, has been listening to the Newark broadcasting station evening after 'evening. In an airline, some forty miles separate him from the WJZ station, yet the radio-phone comes in loud and clear, using the vacuum tube detector only. With one stage of amplification, the sound is greatly increased, and with two stages it becomes possible to use a loud-speaker so that the radio-phone is to all intents and purposes on a par with the phonograph, and the head- phones become unnecessary. Still more remarkable, with certain atmospheric conditions it is possible to pick up the Pittsburgh radio-phone station just as loud as Newark, although under normal conditions Pittsburgh is only a trifle as loud as the nearest station. It is well to mention here that the radio-phone receiver 72 RADIO FOR EVERYBODY is subject to that bete noir which is dreaded by all radio men, namely, static, or atmospheric electricity. Static asserts itself by making all kinds of noises in the telephone receivers, ranging all the way from a frying sound to a loud scratch, which are most disagreeable and interfere materially with the radio-phone service. During the winter, the static is almost negligible, this being especially true during cold, dry winter nights. During the summer, however, especially with the super-sensitive radio receiv- ing sets now employed, static is quite troublesome, al- though it is seldom sufficiently heavy to break up the radio-phone reception altogether. The radio-phone is one of the greatest inventions of the age. It brings right into our homes the very informa- tion which we desire, and the best there is in music. Not so long ago an entire musical comedy was broadcasted, and the listener could almost visualize the performance. Even the dances were broadcasted, the actors wearing special shoes so that the sounds of their dancing could be transmitted. Imagine what the radio-phone means to the farmer, far removed from the city, yet at last in daily touch with the metropolis ! And there are many others who know or should know how the radio-phone now makes life more interesting and more enjoyable. Chapter III. DOT-AND-DASH BROADCASTING FROM MARKET NEWS TO TIME SIGNALS TO the layman, of course, the radio-phone broadcast- ing is the only thing that counts. The dots and dashes that are picked up are meaningless. It may be interesting to note the different kinds of radio telegraph transmitters that can be picked out of the air; perhaps there is some interest in noting their relative strength : but from a truly practical standpoint, they have little value to the layman who has not as yet mastered the telegraph code. However, aside from the radio-phone broadcasting service, there is an excellent radio telegraph broadcasting service now available in practically every part of the United States. It is known as the radio market news service of the United States Bureau of Markets and Crop Estimates and represents an effort on the part of the Bureau to make its market news more immediately avail- able and more effective than it can be made in any other way. Ever since the inauguration of the first market news service on fruits and vegetables in May, 1915, the special- ists of the Bureau have given continuous study to the problem of supplying market news on agricultural com- modities to those who may have use for such information as quickly as possible after it can be obtained. The market news services of the Bureau cover live stock and meats ; dairy and poultry products ; fruits and vegetables ; 74 RADIO FOR EVERYBODY hay, feed and seeds, and some other commodities asso- ciated with these four general groups. The information is suppHed to and is utilized by producers, shippers, dealers, brokers and commission men, manufacturers, warehousemen, demonstration and extension workers, banks, transportation agencies, chamber of commerce, buy- ing and selling organizations, and other commercial, exten- sion and educational agencies. Getting the News to the Public It is the function of the Bureau of Markets and Crop Estimates to gather or assemble market information from reliable sources and distribute it in such a way as to make it available to the greatest possible number who wish to use it. In performing this function it utilizes and co- operates with all agencies possible. It affiliates with State agencies which may or may not have similar functions with respect to the State as the United States Bureau of Mar- kets and Crop Estimates has to the Federal Government. It utihzes the railroads for information relative to ship- ments and movements. In one way or another, it assem- bles information from every available source where such information can be obtained. In utilizing radio communication as a means of dis- seminating crop and market information, the Bureau of Markets and Crop Estimates -is taking advantage of one of the agencies which has certain possibilities possessed by none that has been used in the past. This new method makes it possible for all who wish this information to help themselves to it, if they will but equip themselves to receive it in the form in which it is sent. The advantages of broadcasting information by radio are (1) that the information can be intercepted or coj>ied by means of suit- able equipment at any point within certain approximate limits, whether or not such point is connected by railroad, itelegraph or any other of the ordinary means of communi- cation, and (2) that the transmission of the news is instantaneous. These two factors in radio communication make it possible for any one, whether he is located in a RADIO FOR EVERYBODY 75 congested city or in the country a hundred miles from the railroad or telegraph wire, to receive the information with equal dispatch. Radio transmission can be effected either by the international telegraph code, using dots and dashes, or by radio-phone. The radio-phone will probably present the most good to the greatest number. For the present, and for some time to come, so it seems, the radio telegraph mostly is used for this work. This necessitates, for the time being, at least, a knowledge of the Continental telegraph code, which can be readily acquired if one is but willing to aevote a few months to intense study and prac- tice. In another chapter we shall have more to say regard- ing the code and how it can be mastered. Getting the Crop and Market Reports Crop and market reports sent out broadcast by radio can be received by any agency having suitable equipment. With the development of broadcasting by radio-phone, there is sure to be a demand for receiving equipment from many sources. Not much greater technical knowl- edge will be required to receive the reports by radio than to use an ordinary telephone. In general, at present the broadcasted reports are being utilized by various marketing agencies in giving to farmers the national crop and market reports combined with local market information which is distributed in other ways, by county farm organizations or other local agricultural agencies acting as centers of information for the county or locality, and by banks, shipping associations, commer- cial exchanges, commercial clubs and newspapers, all of which may serve as agencies for secondary distribution of the reports. In addition, the reports may be received direct by farmers, country elevators, dealers, shippers, and many others who will use the information in the transac- tion of their business. The extent to which this latter class will receive market reports direct remains to be seen. It is certain, however, that the State and county radio receiv- ing stations will be developed rapidly because of the economical reception and distribution of crop and market 76 RADIO FOR EVERY-BODY reports through them. Certain individuals or a small group of individuals may find it advantageous to solicit the aid of radio arnateurs in the community. This should be arranged for very carefully to ensure that the amateur is capable of receiving a true copy of the reports as broad- casted. The Radio Market News Service in the Making Since the radio market news service was begun experi- mentally by the United States Bureau of Markets, on December 15, 1920, it has developed very rapidly, so that at the present time the national market news is not only being distributed by the United States Bureau of Markets and Crop Estimates, but other agencies are extending the distribution of the national crop and market reports as well as local market reports. The service was started by the United States Bureau of Markets at Washington, on the date already mentioned. One report was sent out at 5 :00 p. m. each day from that station. This was continued for four months to determine the practicability of the method. When it became apparent that this method would not only be practical but also more economical and efficient for certain kinds of distribution than any other agency, the Bureau of Markets took up the matter with the Post Office Department and accepted their offer to utilize the radio stations of the Air Mail Service in the dissemination of crop and market reports. At the present time, the larger part of the radio market news service of the Bureau is handled through the Post Office radio stations. Many of the agricultural colleges giving instruction in radio communication in connection with their departments of physics or electrical engineering, either alone or in co- operation with the State marketing agencies, have set up programs of broadcasting. These began with the dis- semination of weather reports from the Kansas State Agricultural College in 1916. Crop and market reports are now being broadcasted frorrj several other colleges. Some privately owned stations are also broadcasting the information by radio-phone or by radio telegraph. RADIO FOR EVERYBODY 77 The map on page <9 shows the location of the stations now broadcasting. The leased wire connections of the Federal Bureau are also shown. The leased wire service of the Bureau of Markets and Crop Estimates was estab- lished in 1916 and during the past six years as many as 17,600 miles of leased wire and 61 branch offices have been in operation. The leased wire has been used to carry reports from the markets, shipment information and re- ports from shipping points as to supply and demand, and f . 0. b. prices. Even in its most extended form, the leased wire with the largest number of branch offices was never able to reach more than a small percentage of the people interested. The function of the leased wire will not be changed or curtailed by the establishment of the radio method, but will still be the nucleus of an effective system employing wired telegraph and telephone as well as radio telegraph and telephone. The Air Mail Radio Service of the Post Office Depart- ment was estabHshed primarily to give communication between the flying fields, in connection with the transpor- tation of mail by airplanes. These stations have to be available for service a large part of the day but have con- siderable time which is not necessarily occupied in the business of the mail service. The market reports are sent out on schedules which are adapted to the unoccupied time at the stations. This incurs merely a nominal ex- pense to the Post Office Department and inasmuch as the market information is obtained for other uses by the United States Bureau of Markets and Crop Estimates, the service as constituted at present incurs practically no additional expense to this Bureau. Because of the neces- sity of using stations not intended primarily for broadcast transmission but rather for interstation traffic it is not possible to organize as effective and complete a service as could be furnished by a chain of stations equipped solely for radio broadcast transmission. It is thought desirable, however, to take advantage of every facility at hand in order to obtain experience in handling market 78 RADIO FOR EVERYBODY news by this method and be ready to install a more effec- tive service shouild special facilities be made available at a later date. The Form of Crop and Market Reports Certain types of market information can be put into a form for rapid transmission by use of standard forms and code letters. This does not involve the ordinary use of code words and the necessity of coding and decoding the messages received, but it does make necessary the send- ing and receiving of the reports on special forms. Inas^ much as the sender and the receiver use identical forms, it is possible by the use of code letters preceding each blank space in which information is to be copied, to transmit rapidly a large amount of information prepared in stan- dardized form. By the use of such special forms and regular transmitting schedules a very effective service can be developed. This field has only been touched upon and great improvements undoubtedly will be developed in the handling of information in this way. The receiving of reports by telegraph codes, using dots and dashes, makes it necessary that receiving operators understand the international (Continental) code and be able to copy at least 15 words a minute. Wherever radio telephone communication is established, it is necessary only that the operator be able to adjust the radio receiving equipment properly, since the telephone reports are repro- duced in the radio receiving equipment just as they would be in a wall or desk telephone. Wherever it is desired to utilize the reports sent out by radio telephone, for pub- lication or further distribution, they can be received and copied by a stenographer. At the present time only a few special forms of reports have been developed for use in radio broadcast communication. Others will be developed from time to time as the service grows and modifications of the present forms undoubtedly will be made. In the forms already in use. two-letter code symbols are used to designate the information sent. These are used in two different ways : (1) A two-letter symbol is placed 80 RADIO FOR EVERYBODY at the beginning of the blank space which is to contain a certain type of information. The operator simply sends the two code letters and the information occupying the blank space. For example, in sending ''New Jersey sacked Irish Cobbler potatoes per 100 lbs. in consuming markets, New York (SR) $1.75-2.10," the operator would send only "(SR) $1.75-2.10." Code letters are also used to designate certain options or alternatives to indicate types of information. For example "Demand for Wheat, Mill- ing, Strong (DK) , Fair (DL) — , Poor (DM) • ." The operator would send (DK), (DL), or (DM), as indicating one of the three alternatives and the receiving operator would put a check mark in the blank space fol- lowing the letters received. Fractions are avoided wher- ever possible, but when necessarv are sent as f oHov^s : $1.50 Is sent as 1R50. $1.5014 is sent as 1R50 and 1 DN 2. ^ of 1 cent is sent as 7 DN 8 cents. G5J^ cents is sent as 65 and 7 DN 8 cents. All this, it will be noted, is to avoid confusion and error, for if there should be any doubt about the figures, it goes without saying that the entire value of the reports would be rendered worthless. A Question of Co-operation A number of States, through State bureaus of markets and State extension departments, are co-operating wi/th the Federal Bureau of Markets and Crop Estimates in organizing their States to receive and utilize radio crop and market reports. In some cases they have established regular information centers which serve as distribution points for sending out the information through other channels. In other cases progressive agricultural counties have installed receiving equipment in connection with farmers' organizations so that the information will be available to the county agent for further extension either through the daily newspapers, telephone exchanges, or other agencies. For the present it is probable that the larger application of the radio service will be through RADIO FOR EVERYBODY ^ 81 organizations or institutions which will obtain operators and equipment to receive the reports and distribute them or make them available to individuals or groups or organi- zations of producers. As the radio-phone comes into more general use, many of those engaged in producing or marketing farm products will undoubtedly obtain equip- ment to receive the reports directly as no special trained operator will then be necessary. In several States radio- phone equipment is being utilized so that the reports which are received in code over the leased wire or by wireless may be re-transmitted by radio-phone for the benefit of producers in the State. There are many technical problems in connection with radio telegraphy and radio telephony that have to be con- sidered in the dissemination of broadcast reports. The questions of wave length and kind of transmission are both very important. Although the amateurs are restricted to the use of 200 meters or less for transmission, a large percentage of them are equipped to receive messages over a much wider range of wave lengths. Questionnaires sent to a limited number of amateurs having radio trans- mitting sets show that about 50 per cent are now equipped to receive messages transmitted on wave lengths between 150 and 3000 meters. At first thought it would seem best to have the market reports transmitted on a short wave, but the lower wave lengths lack carrying power. The shorter waves have additional objections owing to interference. Since amateurs are licensed to transmit on the shorter waves, it would be very difificult for the one receiving market news to get solid copy — a comp'lete and accurate copy of the message as sent — if several nearby amateurs were transmitting at the time the Post Office station was transmitting. Because of the greater trans- mitting range and the decreased interference, wave lengths of 2500, 3000 and 4000 meters are being used at the present time. The stations from which the market reports are now- being sent by radio, the type of transmitting sets, the wave lengths used, and the time at which the several reports are sent are given in the transmitting schedule that follows : OS ri 0:= ^ c3 c« c3 3 (fl tfl Ui ^ ;-i ^ a ^ & a a gi g 8 ^5 3 3 lO :3 '»-' CM N— ' a> s a s s s a a OJ a a a a a a a" a s rt d a a D, dd a rj d dddddp H lo O O O O \o vo 'c3 loOOO^^^oioir) 13 •Tf CO CO CO CO O^ T-M (Nl (NJ CO 4f Tf Ti •iir o «-> S^ o 45 <-> +-> C/2 (u ^ o > *-. > o ^^o^Sg ^^ ^c/3-;3 xn-^^ p^^.^o£ S >-^ ^•n.^ -^o-^ ii p^ 3 c c ^ ^°.a.g OJ O 1— 1 o u Co »*-< rn C Cu r/1 "T^ QJ u 03 c "r^ <-> C "5 .>2artS:a§a o xi 5 O g o b < fc^ fc4 ■ o O I r^o 3 fa n o fV'' O <-t B 1 n' w o fD O O "> Q £,Q-p Ef5- >-« ^ .- o 5' p '3^ S o S '^ cr 0.< o i:^ 3 O M S f^ • Q- re p n o 7i pi ^ 2; 71 1 r O H 1 C/3 s s K :2: H-4 1 ^ :^ ^ :^ «j (D ftj v; m <^ < < o cr 3:5:<* n r> CD pi ^ n n O) 3 ^ 3!5t<' P ^ n' n re ^ P p p . rr ^ P P p ^ crq org C/3 g'^:^c^ C/5 » 7Q O) crq (jq O) r<. o ^ o o j:r '^ O O ?r O O JIJ" S C& rr| CSCC& ?SceI < < < ^ ^ *< < < ^ TO 'cl ft> fD ^ .^^™ ^ ^ rih^"' "" /'^ C/^R ^^n ^V.^^^ ^^CT^C/^S^ >3 '"'" ft! O < ri- ^-^ o o < <-^ <-^ ro ►^ O ►i- o o 2. n ^ o o ►4. n r5 o o «. \i- o XJ 0*0 t^"" o n "O ►rr o o -u t^sr ^?rj^ ST ^ hj^^ 'T3 't^'tJ , ^^ K) -P>- «-« KJ 4^ 1-t -( -( to 4^ kT i-T >-« t^J 45. (T-' <0 o t^ C/2 ro fi> a> o "^ CP C/2 W) ill S-i I-* o 3 I-' h- O -t^ tsj 00 00 00 4^ K) \0 00 00 C/l to O 88 s 8SS ^ p §8§88 ^888§ 3 ? 1 1 5^ o H 3 1 1 1 3^ 1 1 J 1 I 3 1 1 1 1 1 >-« s i 4^ to 00 o H 3 00 OO 4^ to vO P 00 00 en to o EL H 3 '^\^'^(J^'^ 4L "hi "hI o^ 4I en, O <-ri Ca Cn Cfi O cyi "O t3 XJ TD P 3 cyi Cn. en. en TJ "O XJ 'O P 3 3 CD 3 3 3 ft 3 3 3 3 3 3 3 3 3 3 fn s CO _^_^ OJ Co ^ 3 3 O 3 3 § 3^ 3 3 2^ 3 ^ O 3 3 ?5 3 ^P 3 n g CLP |3 1 I ft) S5 SI 1 1 s 84 RADIO FOR EVERYBODY The arc stations, it is interesting to note, usually have a greater transmission range than the spark stations. Furthermore, it should be borne in mind that spark stations transmit damped waves and the arc stations transmit un- damped or continuous waves. This information is neces- sary for the selection of the proper receiving sets, and more will be said about this matter in the chapter on re- ceiving apparatus. Why Radio Telegraphy is Used at Present The subject of radio telegraph and radio telephone transmission has been touched upon before. All things being equal and in readiness, radio telephone transmission would be the logical method to use. At present, however, it might be quite difficult to purchase reliable, hig^h^power radio telephone equipment on the commercial market, so claim the authorities ; furthermore, if the Bureau of Mar- kets and Crop Estimates had waited until the high-power telephone transmitter had become commercially available it would not have made the year or more of gratifying history which the service now has. After the broadcasting of market news by radio telegraph was shown to be prac- tical it was decided to use the radio transmitting stations of the Air Mail Service which were already installed and in operation. This forms the first chain of information- disseminating radio stations without the delay and cost of constructing new ones. It is probable that these and other like ones will remain the master stations for some time. Furthermore, when the Bureau of Markets and Crop Estimates is successful in its work of getting the various States, country and private organizations to equip them- selves to receive the radio telegraph market reports, great advancement will have been made, for those stations will be ready to rebroadcast the reports by radio telephone when that system can be installed. In other words, a radio receiving station that will pick up the telegraph messages from the ether will, without any alteration, pick up the radio telephone messages as well. RADIO FOR EVERYBODY 85 The Bureau of ^larkets and Crop Estimates is under- taking to establish on an efficient basis the radio market news serwce. There undoubtedly are many obstacles in the way of making it an immediate, complete success, but so far as these have been considered up to the present time, they are not insurmountable and it is thought that with the radio operators located over the country who are trying to receive the reports, it may well be that the Bureau will be able in a very short time to put the service on an entirely practical, substantial basis. At the present time the Bureau is entirely dependent upon the co-operation of the Post Office Department in the dissemination of the reports and they are giving their heartiest assistance to the Bureau in this work. It wil'l be some time before receiving stations will be distributed all over the country, receiving the reports regularly. A great many of the licensed amateur operators are receiving the reports and many of them are fully competent to do this. However, it cannot be considered as on a permanent basis until the State and county agencies have made provision for equipment and regular operators to receive the reports regularly. These are all controllable factors. The ap- parently uncontrollable factor which must be given con- sideration is the one of natural conditions, such as weather, strays and dust storms. These will be real obstacles, which in some localities and in some seasons will be found worse than in others, During midsummer, radio reception during daylight hours may be frequently interrupted. In fact, it 'may be impossible to receive the reports at times. It will not be necessary for our immediate needs to discuss the probable reasons for these peculiar atmospheric conditions which interfere with radio reception. It is a fact, however, that frequently during the summer months, the strays may completely drown out the radio signals picked up by the receiving set. The idea that higher amplification will relieve the situation is erroneous. The amplifier usually amplifies the strays along with the in- coming signal, so the amplified signal is often less intel- ligible than the signal received on a simple detector. The 86 RADIO FOR EVERYBODY use of high-power transmitting stations is an advantage in this respect. During storms it sometimes is not only impossible to receive any messages, but it may be unwise, especially if the storm is accompanied by lightning discharges. At such times the antenna should be grounded to protect the ap- paratus and no attempt made to receive radio messages. Although dust storms are not generally prevalent, they are to be reckoned with. Occasionally -the transmitting range of a station will be limited in a certain direction owing to an intercepting dust storm. There are yet other diffi- culties, such as fading of signals, which must be encoun- tered, but some of these are avoided by using the long SSSFM lo" zo' so" ^' fo' js' ••••••• •••••••••••••••••••••©•••••••••« •••»»«# «««»«««»ocooo ****•*••••••••••• •••••••••••^•••••••» ••••••••••••••• ••ooooo ••••••••••••••••••••••••••••©••••••••••####««#»«««0»00OOOOO S3* ••••••••••••••••• ••»«««««#«»o« ••••••••• •••••«»«««oooooooooo tZMoon lOP./ft. ^, ^ -, mmoooo J^« ^ /?. Diagrrammatic explanation of the official Navy time sig:nals as sent out by the Arlington station. These sigrnals are re-transmitted by several of the broadcasting stations. £ach black dot represents a transmitted dot, while the white dots represent spaces. The time signals start five minutes before 12 o'clock noon and 10 o'clock P. M. and follow the schedule here depicted, terminating with a dash on the hour, followed by a four dot space and the call letters '•N A A." waves. However, after taking all of these things into consideraftion it is quite probable that a high percentage of completeness may be anticipated in handling this kind of service. From General News to Time Signals Then there are other radio telegraph broadcasting serv- ices available to the owner of a receiving set. The most important of these is the broadcasting of time signals and RADIO FOR EVERYBODY 87 weather bulletins by the high power naval station at Arlington, Va. The time signals and weather bulletins are sent out twice daily on a wave length of 2500 meters, at 11.55 a. m. and 9.55 p. m. The signals begin at these times and the final dash is sent at 12 noon and 10 p. m. and are astronomically correct for the meridian of 75 degrees west of Greenwich. The signals are sent out as follows : Beginning at 11.55 a. m. or 9.55 p. m. a dot is sent every second for the first thirty seconds, then one second is skipped, and beginning with the thirty-first second to the fifty-fifth second the dots are again sent, one each second. The last five seconds of the first minute are skipped, and the signals begin again at exactly the beginning of the fifty-sixth minute. The same schedule is maintained through the fifty-seventh and fifty-eighth minutes right through until the fiftieth second of the last minute is attained. Then comes a silence or blank for ten seconds, and the next dash is exactly 12 o'clock noon or 10 o'clock in the evening, as the case may be. The general scheme of the time signals is perhaps made clearer by studying the accompanying chart. This time is absolutely accurate and is employed by ships at sea for the setting of chronometers, and by progressive jewelers and others desiring an accurate time service. The signals are transmitted at Arlington, to be sure, but the dots originate in a master clock at the Naval Observatory. No sooner are the time signals over than the Arlington station sends out .the weather bulletin in code — a code, however, Which is quite simple to understand. A weather bulletin, as sent out by Arlington, runs as follows : QST de NAA, USWB, S01081— T02261— DB0251 — HOOSM — C01261 — K00441— P1242. .. All of which means, when reduced to plain English, thait the letters stand for K — Key West, Fla. ; S — Sidney, Nova Scotia; T — ^Nantucket, R. I.; DB — Delaware Break- water ; H — Cape Hatter as, N. C. ; C — Charleston, S. C. ; P — Pensacola, Fla. ; B — Bermuda. The first .three figures 88 RADIO FOR EVERYBODY following the letter are the barometer reading at the various places. Taking the first set of figures sent out, S01081, the figures 010 represent the barometer reading of 30.10 inches, and the next figure represents the direc- tion of the wind, which hap- ■j — ^^^^ pens to be NW in this case, ^^/q ^\N£ since the numerals begin with ^^ 1 for North, 2 for NE, 3 for E, 4 for SE, and so on, ^^7 \ gjg as shown in the accompanying diagram, reading around the compass in the same direction ^^ ^/SE as travel the hands of a clock. J — ^"^ The last numeral means the ^ velocity of the wind, and the How numerals are used to r ^^ • i. 'U^ ' i.u c. indicate the points of the followmg table gives the fig- thrH^.^^Jr^r^ft^-in" T^*" ures and their values in statute the direction ot wind num- . , .- . erais used in the ArUngton miles (1.15 uautical miles) per weather bulletins. In • — Cairn to 3 miles per hour 1 — Light air 8 miles per hour 2 — Light breezes ... 13 miles per hour 3 — Gentle breezes . . 18 miles per hour 4 — Moderate breezes 23 miles per hour 5 — Fresh breezes .... 28 miles per hour G^Strong breezes. . . 34 miles per hour 7 — Moderate gale. . . 40 miles per hour 8— Fresh gale 48 miles per hour 9 — Strong ga'le .... 56 miles per hour 10 — Whole gale 65 miles per 4iour 11 — Storm 75 miles per hour 12 — Hurricane 90 miles per hour Now, therefore, take the code signal K00441. The K, it will be noted, stands for Key__West ; the figure 004 states that the barometer stands at 30.04 inches ; the next figure indicates that the direction of the wind is South East, and the last figure, 1, i;epresents the velocity of the RADIO FOR EVERYBODY 89 wind, which in this instance is light air, or a breeze having a velocity of only eight miles an hour. The Arlington time signals and weather bulletins are sent on a wave length of 2500 meters. The call letters of this station are N A A, which are signed immediately after the final dash in the time signals. Fortunately, the weather bulletins are sent at a slow, even speed, so that a person with only a slight training in the telegraph code can copy down the letters and figures. It is well to men- tion here that the bulletins are sent out by automatic transmitter, so that the dots and dashes are perfectly formed. Certain radio-phone broadcasting stations give out the time signals by radio-phone. This is accomplished by receiving the time signals from Arlington on a long-range receiving set, and then amplifying these signals until they are sufficiently loud in a telephone receiver which is held up to the transmitter microphone for retransmission via the radio-phone. In this manner the persons in the vicinity of the radio-phone broadcasting station can receive the time signals without having to tune up to the long wave length of the Arlington station. Furthermore, the radio- phone broadcasting stations receive the weather bulletins and broadcast them In plain English, which requires, of course, absolutely no knowledge of the telegraph code. Time signals and weather bulletins are broadcasted by other naval stations. Thus the Great Lakes station NAJ, transmitting on 1512 meters, sends out time signals at 10 p. m. (90th meridian time). Also, North Head, Wash., San Francisco, Cal., and San Diego, Cal., transmit the time signals at 10 p. m. (120th meridian time), followed by the weather bulletins. The Pacific coast stations broad- cast the information first on their usual working wave length, next on 952 meters, and finally on 600 meters. Reports from these stations are preceded by "USWBSF,'* the first four letters standing for ''United States Weather Bureau" and the last two for San Francisco. Weather reports from the Pacific coast stations are broadcasted at 8 a. m., noon, 4 p. m., and 8.00 p. m. Cape 90 RADIO FOR EVERYBODY Blanco broadcasts Tatoosh, N'orth Head and Eureka weather after local report. At 8 a. m. and 8 p. m. Eureka broadcasts the 6 a. m. and 6 p. m. weather conditions at Farallones; Farallones, in turn, broadcasts the 6 a. m. and 6 p. m. weather condftions at Eureka, and 7 a. m. and 7 p. m. weather conditions at the Farallones. Aside from the Atlantic coast abbreviations already given, the following are also necessary: Great Lake Region Duluth DU Marquette M Sault Ste. Marie U Green Bay G Chicago CH Alpena L Detroit D Cleveland V Buffalo ... F Pacific Coast Region Tatoosh T North Head . NH Eureka E San Francisco SF San Diego SD Aside from the time signals and weather bulletins, there are various press broadcasting services operating from time to time. Some of these have the amateur very much in mind, and in consequence transmit the press items at a slow rate of speed. AH in all, there is quite as much interesting news and general information to be obtained through the radio telegraph broadcasting as there is by radio^phone, although it goes without saying that the first can be received by any one without training of any kind, while the second presupposes at least a working knowledge of the dot-and-dash language of the telegraph. From Radio Telegraph to Radio-Phone As this is being written word comes to us to the efifect that Government information is shortly to be broadcasted RADIO FOR EVERYBODY 91 by radio-phone, this service taking- the place of the present radio market news service of the United States Bureau of Markets and Crop Estimates, as described early in this chapter. A radio-phone has recently been installed on the top floor of the United States Post Office Building in Washington, D. C, and sufficient power is now available to broadcast Governmental messages to the public over a wide area. Governmental information — data assembled by the various departmental bureaus relating to farming, fruit-growing, lumbering, mining, and general knowledge — is being distributed throughout the United States. Con- gress is being urged to establish a "Bureau of Communi- cation" in the Post Office Department, appropriating $500,- 000 annually for its maintenance, thus designating a clear- ing house for the broadcasting of knowledge of a varying nature by radio, catering to the diverse interests of 110,000,000 citizens. The abandonment of radio telegraphy in favor of radio- telephony as a vehicle for the transmission of weather and market information, which service was introduced April 15, 1921, marks the advent of a hitherto unprecedented popularity for the distribution of Governmental data by radio communication. Radio telegraphy, after eight and one-half months of practical app'lication, proved to be too specialized in nature, involving, as it does, a knowledge of the international telegraph code for use as a medium of circulating wxather forecasts and the fluctuating ten- dencies of the markets. Hence the decision to adopt radio telephony as the distributing vehicle, the operation of the radio-phone being little more complicated than the use of a common telephone, a sewing machine, or phonograph. It is contemplated that instant and almost universal popu- larity will be accorded the latter system. The present installation in the Post Office Department Building at Washington is the first unit of its kind to be placed in operation, and claims to novelty may be ad- vanced with regard to its mechanism. This wireless telephone puts 14 amperes into the antenna at 1160 meters wave length, which is a goodly amount of radio energy, as radio transmitters go. The modulation of the voice is 92 RADIO FOR EVERYBODY said to approach perfection. Preliminary tests have suc- ceeded in flinging the voice, so to speak, as far west as Bryan, Ohio, and southward to Atlanta, Georgia, dis- tances exceeding 1,000 miles. The transmitter is quite flexible, so that the service may be varied to suit varying operating conditions if necessary. Contingent upon the will of Congress in appropriating the requested $500,000 for estabhshment of a "Bureau of Communication," the service will be extended in its reach as well as expanded in nature. Isolated areas, as well as frequented points in the United States, will be visited by this hurry-up method of spreading the news. At present there are eight radio stations, as already described, orig- inally established in conjunction with the transportation of mail by airplane, used as distributing agencies of market and weather reports. These are located at Washington, D. C. ; Cincinnati, Ohio ; Omaha and North Platte, Neb. ; Rock Springs, Wyo. ; Blko and Reno, Nev. Radio-phone stations in prospect, by reason of the expansion of the service, will be located in Georgia, Texas, California, Mon- tana, Illinois and at some point in the New England States. A survey being conducted by the Post Office Department will determine the exact locations of these information-distributing stations. The Post Office Department voices the belief that the widespread dissemination of Governmental knowledge will not only prove of economical value to a varied citizenry of the United States, but will serve as a leavening process in Americanizing the increasing element of foreign popu- lation in our midst. The Post Office Department will not only give circulation to market news and weather fore- casts, in the event that Congress sanctions an enlargement of the service, but the different Government bureaus will be drawn upon for facts pertaining to discoveries and developments that will serve the diverse interests of the farmer, miner, rancher, fruit-grower, forester and lumber- man. Then, too, the public in general can appropriate to advantage much of the information circulating through space by reason of its practical value and entertaining quality. Chapter IV. RECEIVING EQUIPMENT AND THE INTERCEPTION OF RADIO WAVES THERE is nothing complicated about radio reception. The apparatus may be of the simplest sort, if the distance to be spanned is relatively small ; virtually no experience is required, for anyone can turn the few- knobs and adjust the detector; no licenses are required, and anyone can intercept radio waves without formality of any kind ; and the cost is low, considering the wonder- ful possibilities of a radio receiving set. It is only when one desires to span great distances and to have the dots and dashes or the radio-phone music amplified so as to be heard throughout a room, without the use of the usual telephone head set, that the cost mounts up. Even so, the cost is still no greater than that of a good phonograph, and certainly less than half the cost of a low-priced automo- bile. After all, it is a question of what is expected of the receiving equipment, and successful results demand that the receiving equipment 'be fitted to the requirements. Essentials of Radio Reception No matter how simple a receiving set may be and how modest the requirements, there are certain essentials which must be provided. Thus we have : First — ^One or more wires elevated from the ground and properly Insulated, to form the antenna or the aerial. The purpose of the antenna, or aerial, is to intercept the radio waves and to convey them to the receiving apparatus. 94 RADIO FOR EVERYBODY An alternative to the aerial is the loop, which is simply a large frame with several turns of wire, which may be used indoors with fair results. Second — A good connection with the ground, which may take the form of a connection with a gas, water, or steam pipe. In the absence of any one of these pipes, such as in remote country districts, a good ground may be ob- tained in other ways, as described further on. Again, the ground may take the form of an insulated network of wires, placed below the aerial but elevated from the ground by a few feet. Such a ground is known as a counterpoise, and is frequently used. No ground is re- quired when a loop is employed instead of an aerial. Third — A means of altering the wave length of the aerial circuit and the receiving apparatus, so as to inter- cept and detect any desired radio waves to the more or less complete exclusion of undesired waves. Tuning is accomplished by a wide variety of instruments and meth- ods, as will be explained. Fourth — A means of changing the frequency of the incoming waves from radio frequency to audio frequency so that they may be heard. The instrument that accom- plishes this result is known as the detector, and is of the crystal type or the vacuum tube type. Fifth — A companion instrument to the detector, which takes the audio frequency current delivered by the detec- tor, after the latter has converted the radio frequency into audio frequency current, and makes it audible to the human ear. This instrument may be any form of telephone receiver, ranging from the single receiver to the head set and to the loud-speaker. The first step, then, is to consider the aerial or an- tenna for receiving purposes. While the same aerial or antenna may be used for both receiving and transmitting purposes, as a general thing these purposes are by no means interchangeable if really efficient results are de- sired. Thus the ideal antenna for receiving — antenna, by the way, is a happier term for the receiving end than aerial, the latter applying more particularly to transmis- RADIO FOR EVERYBODY 95 sion work — is a single 'wire, insulated at both ends, ele- vated some 20 or more feet from the ground and mea- suring 150 feet in length. A shorter wire makes for a lower efficiency, while a longer wire, strange as it may seem, also detracts from the receiving efficiency. The reason for this is that the wave length of the aerial should be as nearly as possible that of the radio waves to be intercepted. Otherwise, in the case of a shorter wire, it is necessary to add inductance in order to bring up the wave length, and such inductance means some loss of energy. Furthermore, a shorter wire v^ill not intercept as much of the radio waves as a longer one. Now, on the other hand, a longer wire intercepts more of the radio How a receiving antenna may be installed in the country. The single wire may be run from the house to a barn, tree, clothes pole or other support. wave, but it is necessary to use either a variable or fixed condenser in series with the antenna in order to bring down the wave length, and such practice means a loss of energy. O'f course, we are considering the receiving set on the basis of amateur and radio-phone reception. If one desires to receive the long-wave commercial stations, a longer wire is quite satisfactory. Indeed, for the best kind of work it may be well to have several antennae, arranged for various classes of service. The Aerial and the Ground for Receiving As for the kind of wire to use, there is considerable latitude; indeed, in this general subject of antennae for receiving purposes there are no fixed rules to go by. 96 RADIO FOR EVERYBODY Various kinds of wire are used, among these being plain aluminum wire, which has the advantage of being exceed- ingly light and quite low in cost ; plain copper wire, which, of course, is an excellent conductor, although somewhat costly, especially in the larger sizes ; hard-drawn copper \vire, which has all the advantages of plain copper, plus greater strength ; copper-clad steel wire, which has great strength coupled with good conductivity; stranded phos- phor-bronze wire, which has long been the standard aerial wire in commercial and Government work ; and annunci- ator or bell wire, which is insulated. The last-mentioned Materials with which to erect the antenna, compris- ing a coil of bare copper or copper-clad steel wire, insulators, ground clamp, insulated wire for lead-in, porcelain tube to insulate lead-in passing into build- ing, and a lightning arrester. wire may sound freakish and merely an improvision ; but as a matter of fact the insulation makes little difference. Why? Simply because if the insulation were not there, the space immediately surrounding the copper wire would be taken up by air, and the air is about as much of an insulator as the usual cotton and paraffin insulation. Hence it makes little difference one way or the other, and annunciator or bell wire recommends itself in many in- stances because it is so easy to obtain. A pound of No. 18 wire is sufficient for a good single-wire antenna. Aluminum wire is not recommended very enthusiastic- ally by the author. Back in the early days of amateur RADIO FOR EVERYBODY 97 radio, when we used to spend our hard-earned money by the cent rather than by the dollar, aluminum wire was widely employed because a good many feet of it came with each pound. However, it has not the conductivity of copper by a good margin, and even when using No. 14: size it is not as good as No. 18 copper. Furthermore, it is difficult to solder aluminum wire joints, yet they should be soldered. If the joints are not soldered, water gets into them and oxidizes the aluminum wire. The oxide takes the form of a white crust, and is of such high resistance that it reduces the efficiency of the antenna materially. Hence aluminum v^ire should not be used ex- cept where cost is a prime essential, and even so, a small sized copper wire is preferable. Copper-clad steel wire is almost as good as solid copper, and costs considerably less. It is the kind of wire that is supplied with the usual antenna equipment as sold by wireless dealers. Hard-drawn copper wire of No. 12 or Xo. 14 guage is satisfactory for antenna construction ; however, stranded silcon bronze or phosphor bronze wire is more durable and w^ll stand greater strains. Now then, having selected the wire, the next step is to erect the antenna. Sup^rts are sought, since for re- ceiving purposes the height of the antenna is not so im- portant and the antenna may be supported by any suitable object, such as a house, tree, flag-pole, clothes-pole, and so on, making masts or supporting towers unnecessary. If possible, the wire should be horizontal, which means that the supports at both ends must be of the same height. It is necessary to insulate the antenna wire. This is done by placing little porcelain knobs or porcelain cleats, such as are used in exposed electric light wiring, at each end of the wire, as shown in the accompanying sketch. Such improvised insulators will serve quite nicely for ordinary installations, but if the antenna is apt to be sub- jected to considerable strains from high winds as well as coatings of ice, it may be well to substitute regular antenna insulators. These take the form of special moulded electrose insulators, with heavy galvanized rings 98 RADIO FOR EVERYBODY Screw Eye No. 14 Copper ^ Tie Wire No. 14 Copper Antenna Wire Insulator Simple way to insulate and fasten the farther end or free end of a sing:le wire antenna. moulded right into the brown insulating material. The insulator proper is provided with many deep grooves, so as to lengthen the surface of the insulator and therefore increase its resistance to leakage or loss. Small electrose insulators will do for the receiving station, if placed at the ends of each antenna wire, between the wire and the support. Another popular form of antenna insulator is one made No. 14 Copper Antenna Wire No. 14 Copper Tie Wire Insulator No. 14 Insulated ,^^^/ Copper Wire How the nearer end or lead-in end of the antenna is fastened and insu-lated. The lead-in w^ire is fastened to the antenna wire by means of a connector, or is soldered so as to insure a perfect and lasting joint. RADIO FOR EVERYBODY 99 of micarta, with a metal lined hole at each end. This kind of insulator is supplied with an antenna equipment now on the market, and has the advantage of considerable mechanical strength with good insulating properties. In the country the erection of the antenna is a simple matter, for there are virtually no restrictions such as one encounters in the crowded city. Thus the antenna wire may be run from the roof of the house to the roof of the barn, or even from the second floor of the house to the roof of the barn. If no barn is available, then the farther end of the wire may be supported by a clothes- pole or tali tree. The author, while this book is being written, is using a small antenna consisting of a single wire about 60 feet long, running from the third floor of a frame house to a tree in the yard. The antenna, made of No. 18 annun- ciator or bell wire, is about 40 feet high at one end, and certainly not over 10 feet at the farther end. While this antenna is an improvised one and is to 'be replaced by a single length of hard-drawn copper wire, some 150 feet long, running from the house to a taller tree than the present one, it has proved quite satisfactory for receiving the radio-phone service from the Newark station, about 45 miles distant, and the radio-phone service from the Pittsburgh station, considerably more than 400 miles dis- tant. However, the less efficient the antenna happens to be, the better must be the receiving equipment. The Pitts- burgh station ordinarily is received by the author with one stage of amplification, and when the atmospheric con- ditions are unfavorable, two stages of amplification must be employed. The Newark station is generally heard with the vacuum tube detector alone, although one stage of amplification makes it more enjoyable. In the city, the antenna presents a problem. What with congested conditions and a none too obliging landlord, the radio enthusiast is often forced to resort to a little strategy. The author, only recently a resident of the suburbs, traveled a rather thorny path in pursuit of radio while residing in New York City. One antenna after 100 RADIO FOR EVERYBODY another was removed by a highly miHtant janitor, carrying out the instructions of an overbearing landlord. The antennae took all kinds of forms, ranging from single wires ,«N5ULATOR INSUUATOR> SIMPLE SINGLE-WIRE L-TYPE How the L.-type single wire antenna is installed. Such an- tennae should not be shorter than 60 feet and not longer than 150 feet for best results in the reception of short waves such as are used in amateur and radio-phone work. running from one house to another across a court or large open space, to a number of wires supported on poles or supported by the dumbwaiter houses on the roof. Finally, the author simply ran a single wire down a chimney, from the roof to the cellar, a distance of about 75 feet. This wire was never detected, and it was tapped in the kitchen of the apartment, through a flue that led into the chimney. A poor antenna at best, it served to receive the Newark radio-phone service some 15 miles distant. All sorts of improvisions may be resorted to when an outdoor antenna is not practical. A metal bedstead, the T-TYPE ANTENNA, TAPPED IN CENTER Arrangement of a T-type single wire antenna. When the antenna runs longer than 150 feet, it may be desirable to tap it in the center for the lead-in, provided the lead-in can be dropped straight down to the receiving apparatus. telephone line with a fixed condenser in series, the bell wiring of the house, the fire-escapes, an indoor antenna of any shape and size — all these improvisions are possible for nearby signals. RADIO FOR EVERYBODY 101 So far, only single wire antenna have been dealt with. The wire is tapped at one end by another length of wire leading to the receiving instruments. This second wire is called the lead-in, and it is preferable to have it of insulated wire, so that if it touches a wall or roof coping or other object there will not be the leakage that would occur with bare wire. But supposing the antenna is stretched over a greater distance than say 125 or 150 feet, and the receiving station must be located near the middle of the span, then what? Simple enough. The antennae so far described are called the L-type, because the antenna proper and the lead-in form an inverted L shape. If the antenna is to be 200 or INSULATORS V-TYPE ANTENNA The V-type antenna, consisting of two wires of about equal length, diverging to two different supports. 300 feet long, then the tap is taken at the center, and to all intents and purposes the antenna is equivalent to two single wires 100 or 150 feet long. In other words, the wave-length of the long wire is halved by tapping it at the center. This type of antenna is known as the T-type. Another modification of this type is the V-type, in which two wires of about the same length run from the lead-in, at one end, divergingly to two more or less separated sup- ports at the farther end. This form of antenna has the same wave-length as the average of the two wires, and is more efficient than a single wire. Then there is the umbrella type which must be employed where a stretch of over 40 feet is not to be had. In this case a tall pole must be used as the center support, and the wires numbering six to ten, radiate downward in all 103 RADIO FOR EVERYBODY directions, being insulated at the top and bottom ends. The lower end of each wire should be 20 feet from the base of the pole, so as to obtain as much spread as possible. The lead-in wire is taken from the top, the various wires being connected together and spliced to the lead-in wire. The erection of the umbrella type is somewhat complicated, as compared with the simple single wire antennae, and is therefore not recommended for receiving purposes except in cases of absolute necessity. For receiving purposes, a multi-wire L-type or T-type antenna is not necessary, hence a description of the multi- wire antenna e — or more properly called aerials, since they are to be used for trans- mitting — will be left for the chapter dealing with trans- mission. The lead-in connects the antenna with the receiving instruments. One of the problems is to bring the an- tenna through the wall or window into the station, no matter where it may be lo- cated. Some amateurs pre- fer to bore a hole through the glass pane of a window, but this is a somewhat tedious job and one that is apt to end in a disaster unless there is considerable skill behind it. A better plan is to cut a board in order that it will fit in the window frame below the partly raised window, so as to keep out the air. The window is brought down on the board. A hole is made in the board and provided with a porcelain tube insulator, through which is passed the lead- in. The lightning switch or arrester can be mounted on the board, if desired. Then there is the ground connection, which is highly important. Indeed, the effectiveness of the antenna system depends largely upon the character of the ground connec- tion. The most practical ground connection is the water UMBRELLA TYPE ANTENNA, The umorella type antenna, which is only employed when it is impossible to obtain a sufficient span for the antenna. This type is quite popular in transmission work. RADIO FOR EVERYBODY 103 supply system. Where this is not available, pipes con- nected with the heating or gas system may be used, al- though these are to be regarded with some suspicion. Sometimes a non-conducting length of pipe is inserted in the gas line before it reaches the earth, so that it is not a true "ground" connection. However, the results obtained soon disclose whether the pipe is grounded or not. At any rate, the pipe selected is scraped with a knife A convenient manner in which to bring the lead-in wire into the house. A board of about the same width as the window frame is inserted at the bottom or top of the win- dow frame, and the window is then pushed against it so as to shut out the air in cold weather. The lead-in passes through a hole in the board, which may be insulated. Thus the window^ can be raised or lowered without trouble. or rubbed clean with sandpaper until it is bright, and connection is made by means of ground damps, which can be obtained at any electrical supply store, or by wrap- ping ten or more turns of copper wire about the cleaned section of the pipe, good and tightly so as to make firm contact. No. 14 wire is preferable for the ground lead, althoug^h anything up to No. 20 will do. Naturally, the insulation is removed from the wire at the point where it makes contact with the pipe. If possible, the wire should 104 RADIO FOR EVERYBODY be soldered, for one cannot take too much pains with the ground connection. More receiving troubles originate with a poor ground connection than from any other source, for the good and sufficient reason that this end of the installation seems so simple that it is often slighted. Too much is taken for granted. However, if no solder is used, then it is well to wind insulating or friction tape about the connection, so as to hold it firmly in position and to prevent corrosion between the copper wire and the pipe. Where the above-mentioned means of ground connec- tion are not available, wires or plates may be buried in the earth and connected to the apparatus. Such wires or plates should include an area of at least 30 square feet, buried in damp soil. Another method is to attach the ground wire to a metal bucket which is then lowered into a well, a brook, a pond or a lake. Doing Away with the Ground Connection — The Counterpoise There are places where a ground connection is out of the question. Take, for instance, desert country, where the soil is sandy and without moisture of any kind. Or again, take rocky country, where there is just a thin layer of soil over solid rock. Obviously, a ground is out of the question. It then becomes necessary to resort to what is known as the counterpoise, which consists of at least the same number of wires as the antenna, suspended beneath the antenna and used in place of the usual ground connec- tion. The counterpoise wires should be elevated but a few feet from the ground, and just as carefully insulated as the antenna wires. In aircraft, the counterpoise form of ground is em- ployed. It must be evident that no ground connection is possible w^hen the machine is in flight. So the antenna consists of one or more wires which are paid out while the machine is in flight, and which trail behind some 100 or more feet in length, while the ground is represented RADIO FOR EVERYBODY 105 by a counterpoise made up of all the metal fittings and stay wires and control cables of the machine. The counterpoise is especially efficient and almost neces- sary in conjunction with continuous wave transmission, as will be described farther on when we come to transmitting equipment. When the summer comes along in such locaHties where thunder storms are common occurrences, it is necessary to give some consideration to lightning. The antenna, How the lightning: switch is installed. It should always be installed on the outside of the building, with the ground wire going as straight as possible. The blade of the switch is con- nected with the antenna, one jaw^ is connected w^ith the receiving set, and the other is connected directly to the ground. Thus the antenna may be connected with the receiving set or "grounded." after all, presents but a small target to lightning, but even so it is well not to take chances. Just as 'electric power lines and telephone and telegraph lines must be protected against lightning, so must the antenna be provided with some protective device. The Fire Underwriters require the installation of a lightning switch or protective device, 106 RADIO FOR EVERYBODY and this should be done as a precautionary measure. The approved type of Hghtning switch is a single-pole, double- throw, 600-volt, 100 ampere, knife switch, mounted on a composition base. The slate base so often provided with such switches is not satisfactory, because -it absorbs moisture and causes quite a little leakage of the radio currents when used in this manner. Lightning switches are required to be mounted on the outside of the building, and the ground connection may be made to an iron pipe driven several feet into the ground. This connection should ibe made with weatherproof copper wire. No. 6 B. & S. guage or larger. It may well be worth while for the radio enthusiast to mount the switch on electrose pil- lars, since these oflfer the maximum insulation, and the pillars, in turn, can be mounted on a stout oak board. However, where only receiving apparatus is being used — and we are dealing with receiving apparatus only in this chapter — lightning protection may be obtained by the use of a vacuum-gap protective device. This device should be installed in place of the lightning switch and should be permanently connected to both the antenna and ground wires. The vacuum-gap lightning protector is made in several different types both for indoor and outdoor in- stallation. The outdoor type is preferable, because the shortest possible route to the ground should be provided for any possible lightning charge. All radio supply houses handle the various types of vacuum-gap lightning protector. Using the Loop in Place of Antenna and Ground Interesting results may be obtained by using a loop in place of the usual antenna and ground, although it is well to remember that the loop is by no means as effective as an outdoor antenna. A loop consists of a suitable wooden frame on which are wound a number of turns of bare or insulated wire. The frame should be suspended or mounted in such a manner as to permit of being swung in all direc- tions. The loop receives best when it is pointing edge on towards the transmitter, and it is this characteristic of the RADIO FOR EVERYBODY 107 loop which makes it interesting. It indicates the direction of the transmitter being intercepted, and this forms the basis of the radio compass which has found such wide use in modern navigation. Loops are of two general types : there is the spiral loop, which is of the flat type, inasmuch as all turns are in the A solenoidal type loop of simple construction, which can be used in place of the usual antenna. same vertical plane and each turn encloses an area smaller than the preceding turn ; and there is the solenoid loop, in which the coils are all of the same dimensions, spreading out horizontally so as to form a square helix. A loop only three feet in diameter is sufficiently large to pick up 108 RADIO FOR EVERYBODY radio-phone broadcasting stations a few miles distant, and larger loops may be employed at greater distances. Trans- atlantic reception is effected by means of loops, which have the advantage of reducing atmospheric disturbances and other interference to a minimum. However, loops The spiral or flat type of loop, which may be readily made and which affords no end of interest- ing possibilities. do not begin to prove as effective as outdoor antennae, hence amplifiers must be resorted to when using loops. Since the number of turns comprising any loop depends largely on the wave length desired and the dimensions of the frame, it is best to decide the exact number in each case by experimentation. To this end the loop should be made with bare wire so that one can tap any number of RADIO FOR EVERYBODY 109 turns, or the insulated wire should be bared at certain points so as to permit of tapping. More will be said about loops in the chapter on operating the receiver. One of the neatest forms of loop. The turns of wire are spaced about one inch apart for the best results. The Irreducible Minimum Among Receivers With the antenna and ground accounted for, the next step is to consider receiving equipment. The simplest receiving equipment comprises a detector and a single telephone receiver. The detector, as we have already- learned, is a device which changes the frequency of the incoming waves from radio frequency to audio frequency no RADIO FOR EVERYBODY so that they may be heard in the telephone receiver. Let us consider the simplest kind of detector. Nothing could be less complicated or less expensive than the crystal detector. It makes use of one of several different kinds of mineral crystals v^hich possess the de- sirable characteristics. The most popular crystal body today is galena (lead peroxide), a silvery gray mineral which breaks in squares with mirror-like surfaces. Rest- ing on the galena crystal is a fine piece of wire, and it is GALENA DETECTOR WfTH SPRING GALENA AND CRYSTAL / CONTACT DETECTOR SWITCH FOR EITHER ETECTOR A crystal detector unit. In this case two detectors are mounted on the sanie base, with a switch for selecting either detector. the contact between the crystal and the wire which does the rectifying of the high frequency radio energy, of the order of 20,000 to 6,000,000 changes of direction per sec- ond, to impulses of varying strength traveling in one direction only, and therefore capable of operating a tele- phone receiver. Sometimes another crystal is employed in contact with the galena, in place of the wire. - Now with all crystal detectors the matter of adjustment is an important one. Unfortunately, the crystals are not uniformly sensitive. Here and there on a given surface there are sensitive spots, and these must be sought out. Hence when using a crystal detector the wire member must be shifted about on the surface of the galena crystal until a sensitive spot is found. Once a sensitive spot is found, the detector need not be readjusted for some time. RADIO FOR EVERYBODY 111 However, if it is jarred the sensitive contact may be lost, and readjustment is then necessary. While the crystal detector is far more sensitive than the earlier forms of detector employed during the pioneer days of radio communication, it is not nearly as efficient as the vacuum tube type, v^hich vv^ill be described further on. However, the crystal type is inexpensive and may be used with the simplest kind of equipment. It requires no batteries of any kind. The simplest receiving set, therefore, consists of the antenna and ground connected to a plain crystal detector, with a telephone receiver in parallel; and no attempt is made to tune such an arrangement. At short distances from a pow^erful radio^phone or radio telegraph station, a crude receiving set of this kind serves quite nicely. Indeed, from France comes the little receiving set v^hich may be carried about in one's pocket. It comprises a telephone receiver, on the back of which is mounted a crystal detector. Such an arrangement is used in Paris for receiving time signals from the powerful Eiffel tower, and even radio-phone concerts are picked up at consider- able distances outside the French metropolis, when using this diminutive receiver. Instead of using a single wire resting on the galena crystal, this device has ten wires resting on ten different places on the crystal, and a switch is provided so that the operator can select any one of the ten wires. Obviously, one or more of the wires are almost certain to be resting on a sensitive spot ; if not, the crystal can be shifted slightly, so as to give ten new spots. This idea is truly ingenious, and works out very well in prac- tice. The little set is provided with tiny spools containing the necessary connecting cords and clips, so that one can hook up to any suitable ground and to anything that will act as an antenna. The framework of a large awning, the fire escape, an iron bedstead, an umbrella — all these and other similar metallic objects may be used for receiv- ing messages from powerful stations but a very short distance away. 112 RADIO FOR EVERYBODY Simplicity Combined with Efficiency With no provision made for tuning, a receiving set must perforce be of a low order of efficiency. Furthermore, all signals come in at the same time, if several transmitters are working in the immediate vicinity. By providing the simplest kind of tuning device, the efficiency of the crystal de- tector and telephone receiver is immediately improved. There are several simple types of tuning devices. One of these is the inductance coil, which con- sists of a large number of turns of copper wire, wound in a single layer on a solid mandrel or tube, and provided with some means for varying the number of turns of wire which are used. A switch may be employed, with contact points so arranged as to represent say every ten turns of wire, in order that ten, twenty, thirty, forty and so on turns may be obtained at will. Again, two switches may be used, one switch working by groups of ten or twenty, while the other switch cuts in one turn at a time. In this manner a relatively fine adjustment may be obtained. If 68 turns represents the proper adjustment, the first switch is turned to the point connecting with 60 turns, and the second switch is turned to the eighth turn of wire. This arrange- ment is found in certain of the present-day receiving sets. Another means of varying the number of turns of an inductance coil is a sliding contact, which moves over the bared section of the wire. Such a device is termed a tuning coil, and is illustrated on page 117. Bare or insulated wire may be used on the tuning coil, so long as the adjacent turns are insulated one from the o'^tp^ -^^ ] ntri G The simplest receiving set that will give fair results, using a rough tuning coil, crystal detector, fixed con- denser and telephone. RADIO FOR EVERYBODY 113 the proper contact is afforded between slider and wire. There are several ways of connecting the tuning coiL a typical one being indicated in the accompanying diagram. It will be noted that the best arrangement calls for two sliding contacts or "sliders" as they are termed, and that in this instance the detector is really in a separate circuit from the antenna-ground circuit. It will be noted that this two-circuit arrange- ment is by far the most efficient, and in the most advanced types of receiv- ing equipment the two circuits are even separated from each other, so that there is no physical connection between the two. A small fixed condenser is placed across the telephone receiver, as indicated, in all crystal detector cir- cuits of this general category. The tuning coil, with its sliding con- tacts which do not always make per- fect contact, has more or less become obsolete. In its place we now find more delicate devices which give a finer adjustment, since the continuous-wave transmitters now widely employed in radio telephony and in radio telegraphy are exceedingly sharply tuned and even a fraction of a turn of inductance makes a considerable diff'erence. So present practice favors another form of tuner known as the variometer. The variometer, which is shown in the accompanying illustration, comprises a fixed set of coils and a movable set of coils. As the knob of the variometer is turned, the relationship between the fixed and the movable coils is altered. When the variometer dial is set at 180, or what- ever may be the maximum dial reading, the coils are so arranged that the current will flow in the same direction in each set of coils, thus adding wave length to the circuit Ti e A two-slide tuning coil arranged for tuning the antenna- ground circuit and tlie closed detector circuit. 114 RADIO FOR EVERYBODY in which the variometer is placed. When the dial is set at 0, the two sets of coils are so arranged that the current will he flowing in opposite directions in both sets of coils, and the coils are then said to be in opposition or ''bucking"' each other. In that condition the inductance is greatly reduced, and the wave length is therefore at a minimum. Hence a considerable range of wave-length values may be obtained with very fine adjustment by the turning of the variometer knob. There are no loose contacts to bother FIXED COiL OR WINDING HANDLE AND DIAL MOVABLE CO!L OR WINDING The mechanism of the variometer. This instrument consists of two sets of coils, one fixed set and one movable set. with, and the rotary action is far more convenient than the movement of sliders along a tuning coil. In the inexpensive receiving sets now being offered to the public, the tuning is effected by several methods. The lowest priced sets use merely an inductance with taps taken off at regular intervals and connected to the points of a RADIO FOR EVERYBODY 115 switch. This rough tuner is placed across the detector and telephone. Since the telephone offers too much resistance 10 the passage of high-frequency current to the detector, a small fixed condenser is placed across the telephone. Such a set, it must be evident, is satisfactory for short distances only, and cannot tune with any degree of ac- curacy so as to throw out undesirable stations and con- centrate on any given station. The sets selHng for $20.00 or $25.00 are of a better grade, being provided with either a two-slide tuning coil^ with the sliders arranged in the form of swinging arms so as to be operative by means of knobs, or a variometer. A crystal de- tector is supplied with such sets, as well as a pair of tele- phone receivers. A finer ad- justment m.ay be obtained with such arrangements than can possibly be obtained v^ith the simpler sets, and of course the results are accordingly ever so much better. Sets of this kind may receive radio-phone service over a distance of 25 miles or less, and with good conditions obtaining the range may be increased to 50 miles. The Newark radio-phone broadcasting station re- ceived word some time ago that an amateur in Albany some 120 miles distant, was receiving the radio-phone music with a crystal detector, and this case is perhaps not so unusual. However, freak conditions are not to be depended upon, and when a definite distance must be spanned day after day, the receiving set should be con- sidered on the basis of minimum performance. Radio telegraph stations carry much farther than radio-phone, so that these same sets may receive radio telegraph sig- nals over 100 miles distant. Wiring scheme for a single varioinet.er and a crystal de- tector. This arrangement pro- duces excellent results. 116 RADIO FOR EVERYBODY The Mission of the Variable Condenser So far, we have only dealt with inductance as a means of tuning. Inductance makes for greater wave length: the more inductance is placed in a circuit, the greater the wave length. There is another device for varying wave length, and that is capacity, which was described in the first chapter. Capacity is presented by a condenser, which KNOB ON DIAL SHAFT FOR MOVABLE PLATES Outside and inside views of a variable condenser, showing its simple mechanism for varying capacity. may be of the fixed or variable kind. For the present we are interested in the variable kind. Various forms of variable condenser are available, some with fixed and movable plates, the movable plate being hinged so that it can be moved toward or away from the fixed plate ; others with a set of fixed plates and a set of movable plates that slide in grooves and pass in between the fixed plates with- out touching them; still others with a delicate means of increasing or decreasing the distance between a fixed and a movable plate ; and, finally, the rotary type, in which there is a set of fixed plates and a set of rotary variable plates which glide in and out of the fixed, set without RADIO FOR EVERYBODY 117 touching them. The maximum capacity is secured when the plates are nearest to each other or when the plates are entirely meshed, as the case may be. There is a simple rule that applies to the use of variable condensers in affecting wave length. When the condenser is in series, the wave length is reduced considerably, and hne variations may be obtained by adjusting the condenser. When the condenser is across or in parallel with induc- tance, it augments the wave length in proportion to the amount of capacity use. The value of the variable condenser comes in the fine adjustment of which it is capable. Thus the inductance typioai two-slide tmits may be relatively crude, tuning coil. yg^ the variable condenser con- nected in series or in parallel with the inductance will serve as the finishing touch. It is much like a weighing operation, in which weights of several pounds are placed on the scale, while the delicate balancing is accomplished by a sliding beam weight. It is for this reason that in many radio receiving sets the inductance is varied in pretty big steps, while the finishing off, so to speak, is left to one or more variable condensers or even variometers, since the variometer is also capable of fine adjustment. The crystal detector is limited to short distances and to weak or moderate audibility in the telephone receivers. It is out of the question to ask for a loud-speaker in connection with a crystal detector. Again, a fairly large aerial must be used in connection with a crystal detector, unless one is situated within five to ten miles of a radio- phone broadcasting station, or within thirty miles of a radio telegraph station. Hence, sooner or later, and rather sooner than later, the radio enthusiast gets around to the vacuum tube detector, even though it does mean storage batteries and dry batteries, as well as more elaborate re- ceiving equipment. But the results are so much more 118 RADIO FOR EVERYBODY satisfactory with the vacuum tube detector that there is scarcely any comparison between such a set and the crystal type. The Vacuum Tube and What It Does The vacuum tube is the most interesting as well as the most useful device which has been developed during the progress of the radio art. Without going into the history of this device, it may be said that Edison originally discov- ered the peculiar behavior of an incandescent lamp fila- ment by inserting an extra wire in a lamp bulb. He discovered the fact that when a lamp filament is cold, no current can be passed across the vacuum between the filament and the extra wire or plate inserted in the vacuum. However, the moment the filament is brought up to incan- descence, a current can be passed across the vacuum gap between the filament and the plate ; but the current can only be passed in one direction, since this device is a uni- directional or uni-lateral conductor of electricity. Thus the vacuum tube, as this device is called, may be used to rectify alternating current, since it allows the current to flow in one direction only and therefore converts alter- nating current into pulsating direct current. This prin- ciple is employed in certain storage battery recharging outfits, as well as in the detection of radio signals. What really takes place in the vacuum tube is subject to a good deal of theorizing, and bulky volumes have been prepared on the subject. It is not within the province of this book to deal with theories, but suffice it to state that the white hot filament gives off milHons of infinitesimal electrically charged units known as electrons. These electrons travel from the filament to the relatively cool wire or plate placed in the vacuum tube, and thus form a bridge over which one-way traffic of outside electric cur- rent is permitted. Depending on the number of electrons, the bridge is of greater or less capacity, and therefore accommodates more or less traffic. Now in the present-day vacuum tube there is a traffic n- ^ X) ,"0 z !jR 2H > 2> C/) o r> m on H 120 RADIO FOR EVERYBODY officer, so to speak, who decides how much traffic shall pass over the electronic bridge. It was Dr. Lee de Forest, the radio pioneer and inventor, who discovered how the traffic could be regulated, and introduced what we are pleased to call a traffic officer for the purpose of an ana- logous explanation. This third member, known as the grid, surrounds the filament and comes between it and the plate, so that the electrons must pass through the grid in order to reach the plate. Any charge which is impressed on the grid immediately affects the electronic flow, allowing a greater or less flow ; and, consequently, the external current being passed over the electronic bridge, between the filament and the plate, is likewise altered by the grid charge — our little traffic officer, as it were. The grid consists of a piece of wire bent in zig zag form or again as a perfect helix or flattened helix, surrounding the filament and separating the latter from the plate. The vacuum tube is a most sensitive device. The slight- est charge impressed on the grid controls faithfully and instantly a rather strong current flowing between filament and plate. In this manner it becomes possible to control a strong current by means of a weak current. The incom- ing radio waves are led to the grid, where they serve to control the electronic flow, and this in turn controls the flow of current through the tube to the telephone receiv- ers. The arrangement is such that the radio waves are converted into audible sounds in the telephone receivers — loud, clear signals, such as never could be obtained with a crystal detector. The vacuum tube can be used for a great many differ- ent things. It is a rectifier of alternating current ; that is, it converts alternating current of almost any frequency and of any strength within its capacity into direct current. It can, conversely, convert direct current into alternating current of a wide range of frequencies. It permits of controlling a powerful current with a weak current; this feature is the basis of the amplifier, since the character - RADIO FOR EVERYBODY 121 istics of a weak current are impressed on a current several times as powerful, therefore giving that much louder response in a telephone receiver. This characteristic is also the basis of the telephone repeaters, now employed in long-distance telephony. Vacuum tubes permit of re- building attenuated telephone currents at any desired in- terval of line, so that a greater distance may be spanned. The vacuum tube, of various capacities ranging from the small 5-watt tube to the large 250-watt tubes, can also be used for transmitting purposes, but that is another story which is left for later on. The "A" Battery and the ''B" Battery of Vacuum Tubes Now the use of any vacuum tube involves a battery for heating the filament, which is the "A" battery but is more commonly referred to as the filament battery, as well as a high-voltage or '*B" battery which serves to pass current across the electronic bridge from the filament to the plate, when the filament is heated for the device to be actuated, whether it be a telephone receiver, an amplifier circuit, a recorder or other instrument. The filament battery, in the case of the more common vacuum tubes, is a 6-volt bat- tery although there are special vacuum tubes which oper- ate on lower voltages. A special tube used on certain Westinghouse receiving sets operates on a single dry cell, or about 1.4 volts at the outside, and draws but l^ ampere of current. The usual vacuum tube, such as the Radiotron, requires close on to 6 volts and a trifle over 1 ampere. Another standard tube, known as the A-P tube, requires not more than 5 volts and about .7 ampere. This means that dry cells are quite extravagant in this connection, since with a drain of about one ampere, any dry cell will not last very long. If dry battery must be used, it is well to employ two sets of five cells each, the two sets being connected together. In other words, the five cells of each battery are arranged in series, with the carbon of one cell connected to the zinc of the other, 122 RADIO FOR EVERYBODY and then the end carbons of both sets are connected to- gether for one side of the combined battery, and the zincs of both sets are connected together for the other side of the combined battery. This virtually means a battery of .twice the life of a single b-attery, although the voltage remains the same. The name of this arrangement of batteries is series-parallel. Still, there is nothing that really takes the place of the storage battery in operating vacuum tubes. This is espe- cially true where more than one vacuum tube is being- used, such as when using one or two stages of amplifica- tion, as is explained in the following chapter. The storage battery may be of any standard type, although since the heavy demand for radio equipment began some few months back, there have appeared several special storage batteries particularly intended for radio work. These storage batteries are characterized by all-rubber cases, eliminating the possibility of leakage from cell to ground or from cell to cell, and doing away with one of the most frequent causes of noisy sets. Furthermore, such batteries are of a smaller ampere-hour capacity than those used for automobile starting and lighting service, thus making them lower in cost and more convenient to handle and recharge. A storage battery must be recharged when it runs down. In a subsequent chapter we shall consider the care and recharging of the storage battery. Suffice it to state that where a radio set employs several vacuum tubes, so that the drain on the storage battery is considerable, it pays good dividends to install some form of recharging ap- paratus. In this manner the storage battery may be re- charged whenever necessary, at a minimum of expense and without losing valuable time. Aside from the storage battery for the filament, a "B" battery must be provided. This battery must be a high- voltage one. In the early days of vacuum tubes a number of flash-lamp batteries were connected together so as to obtain the necessary current, but today there are special dry "B" batteries put up in compact units of 22^^ volts RADIO FOR EVERYBODY 12: each. These **B" battery units come in a small size and a large size. If the receiving set is to be used at regular intervals, it is the part of better judgment to buy the larger size. A single ''B" battery unit is necessary for a vacuum tube detector circuit,- and two units are neces- sary if an amplifier is also used with headsets, and three or four units if a loud-speaker is employed, as will be explained in the next chapter devoted to amplifier circuits. The dry '^B" batteries come in two types, aside from GL m 60 TO TUNER -=-"6" Principle of vacuu>m tube's operation: GLi — Grid leak; CC — condenser ; F — filament ; G — grid ; P — plate ; VT — vacuum tube; "A" — Storage battery for operating vacuum tube fila- ment; R — rheostat for filament current; "B" — ^high voltage "B" battery or plate battery, and telephones. the two sizes. There is the fixed voltage type, in which two leads or terminals give the full voltage of the battery, and there is a variable voltage type, in which lugs, binding posts, or holes and plugs permit of using a number of different voltages. The variable type is especially useful in using certain types of vacuum tube with which the ''B" voltage must be carefully adjusted. When it comes to amplifier tubes, the "B" voltage may be anything from 45 volts up. There are also available special low-capacity high voltage 124 RADIO FOR EVERYBODY storage batteries, which may be used in place of the dry battery units when a set is subjected to extensive use. Such storage batteries may be readily recharged and their Inexpensive receiving: set making use of a variometer tuner and a crystal detector. Such a set is good for a range of 25 miles, perhaps a little more, when receiving radio-phone . programs! operating cost must of necessity be lower than when using dry batteries, which, when discharged, are worthless and must be thrown away. Often the question is asked : Why is it not possible to use the usual lighting current for operating vacuum tubes. RADIO FOR EVERYBODY 125 The fact of the matter Is that we are deahng with dehcate fluctuations in the vacuum tube. If the filament voltage should vary even in the slightest degree, the electronic flow would likewise vary and cause a corresponding noise in the telephone receivers. Therefore, for absolutely quiet operation it is necessary to employ a steady and positive flow of current such as can only be supplied by a battery. Lighting current, whether of the alternating or direct variety, could readily be reduced* down to six volts, but in either case there is a distinct "hum" which would be con- stantly heard in the tekpho-ne receivers and which would drown out the delicate radio signals. Hence lighting cur- rent is out of the question. A Vacuum Tube for Every Purpose It is well to remember that all vacuum tubes are not identical, nor are they absolutely interchangeable. They may look alike if they are of the same size and kind, but there may be slight differences in internal dimensions and degree of vacuum or gas content which are not apparent even upon close examination. Thus the type now in most general use is classed as a soft or gas content tube and requires a critical adjustment of both the "B" or plate voltage and the "A" or filament current. Tubes of this type are extremely sensitive when properly adjusted. The variation of the filament current is accomplished by means of a variable resistance or rheo- stat placed in series with the filament lighting battery. In some receiving sets the rheostat may be calibrated in ohms or even in plain divisions, but in most sets it is not cali- brated at all, a simple arrow indicating in which direction to turn the knob in order to increase the voltage or brighten the filament. The "B" or plate voltage, on the other hand, is variable in steps of 1^ volts, by means of a variable voltage "B" battery as already described. The proper terminal or lug or plug hole of the "B" battery is found by experiment, and no further adjustment is re- quired for a long time to come. The majority of vacuum 126 RADIO FOR EVERYBODY tube detectors operate best on ''B" voltages between 16^ and 22^, and this range is covered by the variations pro- vided on the various types of variable plate batteries. pp 1 RHEOST/V| / ^B- VACUUM ^Sli^^ Pi|P^^^^W*"^^^w| p K-TUNiNG R- DIAL AMD W HANDLE ■ / A medium-priced receiving set making use of a special vacuum tube whicli operates on a single dry cell, instead of a 6-volt storage battery. However, there is no harm in using a fixed voltage "B" battery, except that the best results are not likely to be obtained except if the tube should happen to be one that works best on 22^ volts. RADIO FOR EVERYBODY 127 Amplifier tubes, which look just like the detector tubes and cannot be told apart except by testing their electrical characteristics, are not critical in adjustment when com- pared with detector tubes, and they will operate success- fully on plate voltages of 40 to 80 volts. Where a detector and two-stage amplifier combination is used, three or four 22^ volt units may be connected in series, and connections to the receiver are made in a manner which permits the use of the full voltage on the amplifier tubes, while a variable portion of the same battery is used for the de- VARIABLE CONDENSER Rear view of a simple receiving set vphich makes use of a simple inductance and a variable condenser, as well as a crystal detector. tector tube. Where extremely loud signals are desired plate voltages of 100 or over may be used without damag- ing the amplifier tubes, but the use of this voltage increases tube noises and is therefore not desirable when receiving signals with the telephone head set. However, this infor- mation is only included here as part of the receiver prob- lem, and more will be said about amplifying tubes in the next chapter devoted exclusively to amplifiers. 128 RADIO FOR EVERYBODY A detector tube which does not prove to be critical as to plate voltage and filament current is usually defective. A good detector tube will give greatly increased signal strength with a certain plate potential and filament bril- RYSTAL DETECTOR VARIABLE CONDENSER NDUCTANCE CONTROL TtLEPHONE JACK Front view of receiving set shown on page 127. The cabinet of this set is made of metal instead of the usual wood. liancy. An amplifier tube which requires a critical plate voltage or filament current adjustment will not give satis- factory results as an amplifier. Tubes of this character will generally be found useful as detectors. In certain receiving sets which include an amplifier, it is sometimes RADIO FOR EVERYBODY 129 found that amplifier tubes are recommended for use throughout, for the reason that the wiring provides for a common plate voltage and filament current adjustment. Such practice may simplify the construction and operation of the set, true, but from the standpoint of efficiency, it is mighty poor business. A soft or gassy tube, known as a detector tube, should be used for the detector, and a hard tube should be used for amplifying. These tubes, while they may look alike, are by no means interchangeable, except where the best results are not expected or de- manded. Having been introduced to the vacuum tube in a general way, we can now return to receiving sets once more. The vacuum tube can be used in place of a crystal detector in almost any circuit, and in such applications it will prove a considerable improvement over the latter. Then, by using special vacuum tube circuits, especially of the so- called regenerative variety, which will be described later on in this chapter, the sensitiveness of the vacuum tube is so much superior to the crystal detector as to make a comparison quite out of order. The wiring scheme already shown gives the fundamen- tals of vacuum tube hook-ups when used as a detector. It will be noted that a small fixed condenser and an ex- tremely high resistance, known as a grid leak, are placed in series with the tuner. Furthermore, the polarity of the connections is of utmost importance. Primary and Secondary Circuits and How They Are Coupled So far, the circuits have been of the simplest type, with a physical connection between the aerial-ground circuit and the closed circuit, known as the oscillating circuit, in which the detector is placed. Now for reasons which need not be explained here, since this work does not attempt to concern itself with the theories or the mathematics of radio but rather with the application of the results, many sets make use of distinct aerial-ground and oscillating 130 RADIO FOR EVERYBODY Loose-coupler of the old type which has now become more or less obsolete. circuits, with no physical connection between them. Trans- ference of energy between the former and the latter is effected by means of two windings which are brought into more or less close inductive relation. In one form these windings are known as a loose-coupler, in another they form a vario-coupler, still an- other arrangement calls for compact coils held in hinged holders so that they may be swung towards or away from each other. The loose-coupler is the forerunner of the v a r i o - coupler and the compact coil arrangement. It consists of a large tube on which are wound many turns of wire, which is the primary and is connected with the antenna and the ground, and a smaller tube, which slides in and out of the large tube and is wound with many turns of wire. Some means, such as a slider or a multi-point switch, is generally employed to vary the number of active turns in both the pri- mary and secondary of the loose coupler. In keeping with modern prac- tice, which has done away with sliding arrangements in favor of rotary adjustments, the vario- coupler has become the stand- ard device for coupling the primary and secondary circuits of a receiving^ set. The vario- t 1 J. u J vt, Vario-coupler, which has coupler has a tube wound with taken the place of the old many turns of wire, forming *yp« loose-coupier. the primary or antenna-ground circuit, and a wooden ball or composition frame, which is mounted on a rotable shaft and is also wound with many turns of wire to form RADIO FOR EVERYBODY 131 FT T^ How a loose-coupler or vario- coupler is introduced in a crystal receiving set. In tliis instance the primary is adjustable. the secondary or the oscillating circuit member. The accompanying- diagrams indicate better than words how the loose-coupler, vario-coupler, or inductance coil mounting may be em- ployed in connection with a vacuum tube or a crystal detector. Obviously the vacuum tube is to be used wherever possible. There are also given several cir- cuits in which fixed in- ductance units, vario-meters and condensers are em- ployed. The radio amateur soon learns to arrange and re- arrange his receiving equip- ment until he obtains the best results — if he is ever satisfied. Inductance in Small Packages The tuning coil has more or less become obsolete, and in its place we find more compact forms of in- ductance. One of these later-day forms is a single layer of wire wound on a tube, after the fashion of 'the tuning coil, but having a mul- ti-point switch connected with vari- ous numbers of turns, in- using a loose-coupler or Tario- (iff^:^c\ ni n ^lirlpr TVipn tViPrp coupler in connection with a steaa 01 a snaer. i nen mere variometer and a variable con- are the compact mductance denser for increasing or decreas- •1 1 ^^ T\ ing the antenna circuit w^ave coils, such as the Duo- ^ length. 132 RADIO FOR EVERYBODY Lateral and the Honeycomb types, which, while fixed as regards their wave length values, are used interchangeably so that the operator can readily shift from one coil to another and thus vary the wave length in big steps, de- pending on a variometer or a variable condenser for the finer tuning. Second only to the development of the vacuum tube, the concentrated inductance has marked a new era in radio. Prior to 'the war there were in general use the huge, bulky, single-layer inductance coils then so closely identified with long-wave recep- tion. Compact re- ceiving sets, sim- p 1 e adjustments, and the neatness that goes with small units, were not to be thought of because of the bulkiness of the inductance then employed. The demand for compactness and simplicity, to- gether with the far greater effi- ciency and prac- ticability, on the part of the war- ring nations, called for a radical change in inductance de- signs. As a consequence, so-called bank-wound coils were employed to an increasing extent, followed soon after by the present types of concentrated inductances. Today practically all receiving sets with a long-wave capacity are provided with these compact inductance units since a long wave length can be obtained in a very small space. Special mountings have come into use for these compact One style of mounting which takes two or three compact inductance coils for a loose- coupler, and tickler coil combination when using a regenerative circuit. RADIO FOR EVERYBODY 133 inductance coils. The usual method is to mount the coils on a block by 'means of a fiber band which passes around the coil to hold it in place. The block, in turn, is provided with bayonet plugs so that it can be readily plugged into a circuit. A loose-coupler arrangement is effected by means of a stand which permits of moving the coils towards or away from each other, and, in some cases, even turning one of the coils from the vertical to the horizontal position. Another form of compact inductance is known as the spider-web inductance. This consists of a sheet of in- sulating material in which radial slots have been cut, and the wire is wound spirally in and out of these slots, so as to make a flat or pancake inductance unit. Such inductance units can be used as a loose-coupler by having one fixed and the other hinged. The Question of Telephone Receivers Little or nothing has so far been said regarding the telephone receivers, yet here is an important member of any receiving set. In fact, no matter how elaborate a receiving set may be, if the receivers are not of the best available type, the results are not as good as they might be. Radio telephone receivers are not just ordinary tele- phone instruments. They are far more sensitive than anything which is ever used in regular wire telephony. First of all, they are constructed with the utmost care; secondly, they have windings of very fine wire, as com- pared with 'the relatively large wire used in the ordinary telephone receiver. Thirdly, the diaphragm of the usual wireless receiver is far thinner and therefore more delicate than that used in the ordinary telephone receiver. Fourthly, in certain types of wireless receivers the two receivers of a head set are matched in tone, so that both ears receive precisely the same sounds. This feature makes for the utmost response on the part of the ears, and therefore the best signals. Xo matter how inexpensive a receiving set may be, it 134 RADIO FOR EVERYBODY is poor business to economize on the telephone receivers ; for it is a fact that a receiving set is no better than its telephone receivers. The telephone receivers, after all, are the final link in the chain of reception; they comprise the agency which actually conveys the radio signals or music or what not to the operator's ears, and as such they can add to or detract from the receiving set as a whole. ADJUSTABLE INDUCTANCE ^ COtL i l#^ HFjV WfNOOW FOR DETECTOR TUfiEs! H / WINDOWS FOR AMPUIFIER: / TUBES 1 PRIMARY ^^*^*^S^S! s ^^Hj^^^^^^^^^^^^^'x .'"7^"-^''-^'^ SECONDARY CONDCNSEK PLUG FOR TELE. ^HOM£S '''illlllllllf^ Receiving: set in wliich three compact inductance coils, adjusta- bly mounted on top' of cabinet, permit of variable coupling and regenerative action. The unit at right is the vacuum tube de- tector and two-stage amplifier. Of radio telephone receivers, there are various types and special merits are claimed for each type, as might well be expected. However, there is one fact that applies to all types, and that is the care with which a really good receiver must be constructed. That is why the better offerings cost considerably more than others ; and it will generally be found that the better offerings are well worth the extra cost. If the radio amateur does not feel he can afford the better kind of telephone receivers, he can at least start with an inexpensive pair, and later on go to the better kind, experiencing thereby considerable pleasure RADIO FOR EVERYBODY 135 in the increased range and clearer signals or telephone messages which he obtains with his receiving equipment. Certain types of receivers have been carefully matched for tone and pitch, and respond loudly to signals over a wide range of frequencies, especially those of high pitch, thus permitting reception that would not be possible with inferior head sets that do not respond to signals of high frequency. Other types have two solenoids wound on the pole pieces of a laminated permanent magnet which acts upon an iron reed fastened to a conical aluminum diaphragm. The reed is adjustable and, therefore, the ^ ^^COMPACT INOUCTAMCE COW. CRV5TAL DETE.CTOR S^ raB TUNING DIAL Sm i .' I!! ^ ' ^ — X ''K ' Q FILAMENT "RHEOSTAT f^0t^ "t".* {.^^^SmL i «v ^ .. « l^ % / ,„ ■ ^^k...^ i^'.-liie •«'»^.,€ © '' ^^m MEAD PM0NE5 ^^'^■■B ^1^0^- Y ^mk '■""' TELEPHONE PLUG Receiving set making use of compact inductance coils for rapidly- changing the wave length range in erg steps. The unit at right is the vacuum tube detector. reed note can be made identically the same in both ear pieces to coincide with the spark frequency of incoming signals or what is known as the beat frequency. An ad- justment screw is mounted on the back of each receiver case and is designed so that excess adjustment cannot be made. The diaphragm is of unusual design, being of a conical shape with greater thickness toward the center. This design is said to result in improved reproduction. 136 RADIO FOR EVERYBODY There is still another type of wireless telephone receiver in which a solenoid winding is mounted in such a manner with relation to the long permanent magnet within the A single circuit tuner making use of a variometer and a variable condenser, as well as a tickler for regenerative effects. The general tuning is done with the first handle, the fine tuning with the lower left-hand knob, and the regenerative effect is controlled with the lower right-hand knob. case as to actuate an armature which connects with a mica diaphragm. The slightest current variations throughout RADIO FOR EVERYBODY 137 the solenoid windings will actuate the armature which in turn vibrates the diaphragm. With all receiving sets, whether of the crystal or the vacuum tube type, it is generally impossible to use a loud- i ^^"^^^^^1^ TEUEPHONE ^lll HEAD- SET ^I^Mr '-^^F^^LvACUUM-TUSES Companion unit to tuner siiown on preceding page. This unit is the vacuum tube detector and two-stage amplifier. The two knobs are the rheostat controls for the detector and amplifier tube fila- ments. The telephone plug may be inserted in one of three holes or jacks, if detector only, one stage or two stages of amplifica- tion are desired. speaking telephone — an instrument equipped with a horn that projects loud sounds throughout a large room, thus making the use of telephone head sets unnecessary. A loud-speaker must be operated by means of an ampHfier, 138 RADIO FOR EVERYBODY and this phase of radio reception will be described in the next chapter. It occasionally happens that nearby trans- mitters are received so loudly that they may be heard some distance away from the telephone receivers. Under such circumstances, it is obviously possible to attach a Regenerative set making use of tickler coil. P — primary of Tario-coupler ; TIC — tickler coil; VCl — variable condenser for varying- antenna-ground wave length; VC3 — variable con- denser for varying secondary of vario-coupler ; GLi — grid leak; GC — grid condenser; VT — vacuum tube detector; B — high voltage or plate battery; FC — fixed condenser; T — 'phones. The dotted line indicates how wiring would run for an ordinary, non-regenerative set. horn to a telephone receiver and thus have an improvised loud speaker, but this is certainly the rare exception rather than the general rule. Regenerative Reception or Self Amplification So far, the various receiving layouts or hook-ups have brought the radio frequency energy right to the detector, which in turn rectified it and passed it on to the telephone receivers. Now if the energy which is about to be passed on to the telephones is partly re-impressed on the grid of the vacuum tube, it will add materially to the voltage of the incoming signal. This will naturally give a greater charge on the grid, and consequently a greater variation RADIO FOR EVERYBODY 139 of plate current, which in turn means louder signals. In this manner the sensitiveness of the vacuum tube is greatly increased ; indeed, it is operating as a detector and an amplifier combined. This practice is known as the regen- erative or feed-back reception. But how is the plate energy re-impressed on the detec- tor? There are two methods in general use for obtaining the regenerative effect. The first makes use of what is known as the tickler — an extra coil which is brought near the inductance or winding of the detector or oscillating circuit. Thus the simplest type of regenerative receiver consists not of two compact inductance coils but of three coils, adjustably mounted, as shown in the diagram on f A ri VCt \- R. FC - in order to pick up any given radio telephone or radio telegraph station. With a loose-coupler tuner, the oper- Nothing: is simpler tlian erecting' the antenna for receiving pur- poses. A single wire, with insulators at either end, is run between the house and a barn, tree, or clothes pole. Then a tap is taken oflf the near end of the antenna and brought into the house. This is known as the lead-in. 148 RADIO FOR EVERYBODY It is best to pass all wires through porcelain tubes when they enter the house, as shown here, even thougrh the wires may be heavily insulated. It is an additional precaution Avell worth taking* ator soon learns how to adjust the primary and secondary circuits, and how much coupling to use. With condensers or variometers, the operator becomes familiar with the adjustments of the various dials for picking up any desired transmitter. Indeed, some instruments are provided with dials that have plain subdivisions, without numbers of any kind, or even with plain pointers and blank backgrounds ; yet the operator soon learns just where to place the dials or pointers in order to obtain the desired results. At first, the operation of a radio receiving set is apt to be a little complicated and possibly disappointing, for the reason that the operator may not obtain the best results immediately. But at the end of an hour or two the oper- ator readily masters the various adjustments and knows RADIO FOR EVERYBODY 149 just where to place the dials and pointers in order to pick up the transmitters which he wants to listen in on. Fur- thermore, it is interesting to note that any extensive change in the antenna varies the relative adjustments of the receiving set. Thus if the operator is accustomed to a giveil antenna, the changing of the proportions of that antenna or its height will upset the previous tuning values and the operator will have to learn his adjustments all over again. However, much of the fun that is afforded by radio comes in learning how to tune the receiving set and in searching for new transmitters. Installing the Receiving Set In a way, the few pointers regarding the installation of the receiving set should come ahead of the foregoing 1 '^ m ', E 1 - 1 I j 1 '"[^^^m M m -. ^^^^//axiei^ * ^M^mJMt HHI 1^ The vacuum gap type of lightning arrester is widely employed for receiving stations only. It is automatic in its operation, being always ready for action, no matter whether the receiving set is being used or not. 150 RADIO FOR EVERYBODY data on the operation of the simple receiving sets. But as a matter of fact one need pay little attention to the installation of the simple sets, for the reason that their simplicity limits their efficiency, so that the finer details of installation hardly apply to them. When it comes to elaborate vacuum tube receiving sets, it may be well to give a little thought to the installation for the purpose of obtaining the utmost efficiency. To begin with, the receiving apparatus should be so placed as to permit of the shortest possible leads from the receiver to the point where the antenna lead-in enters the building. Sufficient space should be provided between the instrument and the edge of the desk or table to allow the operator to rest his forearm when adjusting the con- trols. Right here we can draw a comparison with the simpler sets, which have a single knob or perhaps two knobs on top of the case or on the side, the adjustment of which does not have to be so delicate as to call for the resting of the forearm. In the case of elaborate vacuum tube apparatus, however, the turning of a knob a hair's breadth may make for all the difference between distorted music or talk, or perfect reception. The antenna lead from the lightning switch should pass through the wall or window within a porcelain tube or special lead-in insulator. We have already read of the board which can be placed in the window frame so that the window may be raised or lowered without interfering with the lead-in passing through the board placed at the top or the bottom of the window frame. If the lead-in is not insulated itself — heavily insulated wire is generally employed for this purpose — then it should be supported away from the walls by means of small wall insulators. The ground connection lead does not require any special insulation ; ordinary No. 14 rubber covered copper wire is well adapted to this purpose. From Bed Springs to Fire Escapes and to Loops There are times when one cannot install the usual type of antenna for receiving purposes. In such an event one RADIO FOR EVERYBODY 151 j^ Too much pain» cannot be taken vrith the ground connection. The ground may seem simple enough — and it is; but one should use a good ground clamp whenever possible, and connect it with the cold water pipe for best results, as shown here. need not give up the idea of radio, for almost anything will serve for an antenna especially when receiving from nearby stations. Excellent results may be obtained with a piece of wire about 40 feet long, just strung back and 152 RADIO FOR EVERYBODY forth in a room or placed behind the picture moulding so as to be out of sight. We know, of a man who uses an antenna for receiving from the Newark broad- casting station at a distance of 250 miles, and, on oc- casion, from Pittsburgh, some 650 miles away. The same man receives the signals of Nauen, Bordeaux, and other European high power stations with the same antenna. The usual fire escapes found in the city make excellent antennas. However, care must be taken in Simple vacuum tube hook-up for use with a loop antenna. Note that VC is a variable condenser; GL — grid leak; V — variometer acting as the "feed back" inductance; T — tele- phone receivers; B — *'B" or plate battery; FC — fixed con- denser; K — rheostat for filament current; A — filament battery. This arrangement will operate over short distances. For greater range a radio frequency amplifier must be used scraping the paint ofif clean in order to make a good con- nection with the metal. Sometimes a gas pipe makes an excellent antenna, while the water pipe is used for the ground. If nothing better presents itself, a metal bed- stead or bed spring serves as an antenna, with good re- sults. Indeed, the problem of the antenna need never RADIO FOR EVERYBODY 153 trouble the radio devotee, for the reason that with the sensitive receiving equipment of today most anything will serve as an antenna when working over short distances. Then we have the loop, which takes the place of antenna and ground connection. The loop is connected in the same way as would be the secondary of a vario-coupler or loose-cO'Upler. A condenser is placed across the loop terminals so as to vary the wave length. A typical loop hookup is given in the accompanying wiring diagram, which, it will be noted, makes use of a plate variometer as the feed-back in order to obtain regenerative action. A loop outfit of this kind gives good results over reason- able distances, although it does not cover the same dis- tance as would the same equipment when used with a good antenna. However, during the summer months when there are many lightning storms and when static is -at its very worst, the loop presents an interesting means of reception. To begin with, the loop is safe from light- ning even at the height of a lightning storm, since it can be used indoors. Furthermore, the loop does not pick up static as does the usual antenna, for the reason that it -does not make use of a ground connection. But it is well to remember that a loop intercepts but a small portion of the usual energy intercepted by a good antenna. Therefore, for best results a radio frequency amplifier, such as described in the chapter on amplifiers, should be employed in order to build up the wave energy intercepted. The loop is a directional receiver — it receives best when pointed end on towards the transmitter. Many inter- esting experiments can be performed with a loop. Elaborate receiving sets presuppose the use of the vacuum tube detector, for no really efficient radio reception at considerable distances can be obtained without this form of detector. With the introduction of the vacuum tube, however, the operation of a receiving set becomes a trifle more complicated than with the crystal detector, for while the latter does not give forth sounds of its own and is virtually silent except for the wireless telegraph and radio telephone waves, the vacuum tube creates plenty of noises 154 RADIO FOR EVERYBODY of its own in addition to the desired signals and telephone messages and music. A person passing from a simple crystal set to a vacuum tube set may be disappointed at first, because the vacuum tube makes so much noise and has to be tamed occasionally, so to speak, in order to subdue it, especially when using the utmost regenerative action. But when the vacuum tube is once adjusted prop- erly, the clarity of the received messages or music, together with the strength of such messages or music, is so far ahead of the crystal detector as to make a comparison a sheer waste of time. Vacuum tubes should not be put in place until it has been ascertained that all battery connections have been correctly made. This will avoid the accidental destruction of the tubes. The tubes, which cost upwards of $5.00 each, may be burnt out just as any electric lamp can be burnt out by applying excessive voltage on the filament. There are on the market little fuses which fit on the con- necting pins of any vacuum tube, and it may be the part of good judgment to provide one's vacuum tubes with these little fuses as a measure of protection. At any rate, if all battery connections are checked over and found to be correct, it will avoid the accidental destruction of the tubes whether fuses are provided or not. The filament lighting battery, which is generally a storage battery, may be placed on the floor directly be- neath the apparatus and the wires connecting this battery with the apparatus should be at least No. 14 B. & S. copper wire, properly insulated. Dry battery, consisting of four cells, may be used with a single standard detector tube, but it is expensive practice and not very satisfactory. The condition of a storage battery may be tested by means of a hydrometer or a voltmeter. The hydrometer is an instrument which measures the specific gravity of the storage battery liquid or electrolyte, to give it the technical name. The cap or plug of each cell of storage battery is removed, and the hydrometer tube is inserted in each cell. Squeezing the rubber bulb of the hydrometer^ RADIO FOR EVERYBODY 155 and then releasing it, causes the electrolyte to rise in the glass tube of the hydrometer. The specific gravity can be Xarge loop antenna employed for the reception of trans-Atlantic messages by a New York newspaper. The loop is mounted so that it can be orientated or pointed towards the transmitting station. 156 RADIO FOR EVERYBODY readily determined, and the relative charge of the cell ob- tained in this manner, by means of the bob or float. One popular form of hydrometer now on the market has three colored balls in the glass tube, instead of the usual bob with buckshot, which may be a little confusing to the layman. If all three balls of this new hydrometer stay up when the electrolyte is introduced, the battery is fully charged. If the white ball goes down or sinks, the battery is all right. If the green goes down, the charge is lean. If the red goes down, the charge is dead. This hydrometer affords a simple test for any storage battery. When using a voltmeter, it is necessary to have an The construction of a **B" battery, showing the separate cells, the waterproof partitions, the special insulation, the terminals, and the method of sealing: the entire battery. instrument especially intended for the purpose, which measures from to 3 volts, or to 5 volts. The fully charged cell registers 2.2 volts. When the voltage drops to 1.8 volts per cell, the battery should be recharged. To allow the cell to drop below 1.7 volts is bad practice, for it hastens the wear and tear on the battery. Storage batteries are rated in ampere hours. Generally speaking, a 20-ampere-hour battery will furnish a current of 1 ampere for 20 hours, 5 amperes for four hours, and RADIO FOR EVERYBODY 157 so on. If a vacuum tube detector alone is being used, then a 20-ampere-hour capacity is sufficient. If ampli- fiers are employed, a 60-ampere-hour storage battery should be used. Vacuum tubes of the standard type re- quire about 1 ampere each, so that a 60-ampere-hour bat- tery should operate a receiving set of detector and two- step amplifier for about 20 hours, after which the battery must be recharged. Storage batteries may be recharged by means of a simple home recharger, or can be sent to a nearby garage or battery service station. The home recharging sets are designed for direct or alternating currents. The latter class are of two general types, namely, the vibrating reed type and the vacuum tube rectifying type. The former has a vibrating reed which rectifies the alternating current and steps it down to a suitable charging current. The vacuum tube rectifying type has a special vacuum tube which rectifies the current. A transformer steps down the current. The author has used a vibrating reed re- charger with excellent results, and at a cost of but a few cents for each charge. In fact, in the long run a recharg- ing set pays for itself many times over, since the regular price of recharging a battery is 50 cents to $1.00 in most service stations, while the cost with a home recharging set is a matter of 10 to 20 cents, depending on the size of the battery and the length of charge. The plate batteries, which are the high voltage batteries, will be most accessible if placed directly back of the receiver so that the wires can be readily brought to the proper binding posts of the receiver and amplifier units. Of late a number of B storage batteries have appeared on the market. It is claimed that the storage battery type is more economical in the long run than the dry battery, and that it furnishes a more uniform and less noisy cur- rent, which is an important consideration in vacuum tube work. These batteries run about 22 or 24 volts per unit, and two units can be used for amplifier operation. They can be readily recharged, since their ampere hour capacity is 2 or less. 158 RADIO FOR EVERYBODY x\ll receiving sets and amplifier units are provided with jacks or binding posts for one pair of telephone receivers. If the jack is used — the jack is simply a metal hole or socket in which fits a plug fastened on to the cords of a telephone receiver — only one telephone receiver or head set can be used at a time. However, there has recently appeared on the market a multiple plug, which is inserted in the jack in the usual manner and which provides two Vibrating type of rectifier and stepdown transformer outfit for recharging storage batteries on the usual alternating cur- rent supply line. The vibrating reed, which appears under the handle, rectifies both sides of the alternating current so that direct current is obtained. The volume of direct current is indicated by the ammeter. holes or jacks for two head sets or for a head set and a loud-speaker, each instrument being provided with the proper plug. Furthermore, there is also available a mul- tiple jack which may be mounted on an instrument or on a table near the instrument. The multiple jack presents three jacks all connected in series and so constructed that one, two or three plugs can be inserted. As each plug RADIO FOR EVERYBODY 159 is inserted, it connects itself automatically in series with the circuit, while the unused jacks are short-circuited so that the circuit will remain closed except for the jack or jacks being used. The use of these devices is to be recom- mended where more than one person is to listen in. Of course, where binding posts are used for the telephone connection, two pairs of telephone receivers can be clamped under the binding posts. When the telephone receivers are connected directly with a vacuum tube detector, they may be arranged in parallel, but when they are used with a one or two-step amplifier, they should be arranged in series because of the high voltage used. In the latter case they are arranged with one tip of each telephone set going to one of the binding posts, while the two remaining tips of the tele- phone sets are connected together, thus putting the sets in series. The use of the multiple jack or multiple plug simplifies this matter and makes positive and noiseless connections. A Few Pointers on Operating the Receiving Set With the fifty-seven varieties or more of receiving sets now on the market, it would be impossible to give precise directions on the operation of each set. However, the vacuum tube receiving sets fall into a few general classes, so that broad instructions on each class are certain to fit every individual case with due allowance made for the peculiarities of each particular set. The simplest vacuum tube set is of the single circuit type, in which no loose-coupler or vario-coupler is used. Furthermore, no regenerative action is employed, which' greatly simplifies the operation but also makes the set less sensitive than it might be. Such a set makes use of a tuning coil or variometer, and perhaps a condenser. The inductance may be fixed, in the form of a compact in- ductance unit, with a condenser in series or in parallel to vary the wave length. However that may be, the ad- justment of wave length comes down to the one or two components, and is soon restored in each case. 160 RADIO FOR EVERYBODY The operation of the vacuum tube requires a little care. The filament rheostat must be varied until the best signals are obtained, after tuning them in to the utmost strength. Generally the signals are loudest and clearest when the filament rheostat is moved up to a point just before the hissing sound is heard in the telephone receivers. With most vacuum tubes, the plate voltage is critical for best results, so that the B battery should be varied in order to obtain the loudest and clearest signals. Either a B battery of the variable voltage type can be employed, or a rheostat can be placed in series with the battery and the plate circuit. For the very best results, a potentiometer should be used with the B battery for the most accurate adjustments. The potentiometer is a resistance placed across the source of energy, while hooking up to one side and using a sliding contact to take current off the resist- ance at any point, thus making for very delicate control as compared with the simple series resistance of the usual rheostat. The use of the regenerative arrangement complicates the operation of a set not a Httle but it also makes for louder signals than could ever be obtained with a simple circuit. Regeneration is obtained either by means of a tickler coil or by a grid variometer, as a general thing. Take the case of the tickler coil, which controls the amount of regenerative or feed-back action. First the detector tube is adjusted until it is as near silent as pos- sible, yet responds to the spark signals. This is generally before the point where the tube becomes noisy, although at times the temperamental tube works best when the rheostat has been moved past the noisy point and into another zone of relative silence. Then the tuning handle or handles are adjusted so as to bring in the desired sig- nals or telephone messages. Furthermore, by means of the tickler handle, the quality of the reception can be improved if necessary. If too much tickler action is used, the signals or the radio-phone are apt to be mushy and distorted because of excessive regeneration. Finally, the RADIO FOR EVERYBODY 161 signals or radio-phone are refined by turning the vernier adjustment, if the set is provided with such a device. The vernier is simply an auxiliary tuner which deals with much finer variations than the main tuner. It is neces- sary in the best types of receivers, because regenerative circuits are extremely sensitive and sharply tuned for the best results. Generally, when using the regenerative method of recep- tion, a radio-phone station denotes its presence by a whistling sound as the tuner is varied. By moving the tuner back and forth over the entire range of wave lengths, whistling sounds may be detected at certain points. Then the tuner is finally adjusted so as to get in between these whistling sounds, where there is a silent zone. It is in this zone that the radio-phone music or talk is heard. At other times these whistling sounds are due to contin- uous wave or undamped wave transmitters, which, like the radio-phone, make use of the same kind of waves and therefore have the same characteristics. Once adjusted, a regenerative receiving set will main- tain its adjustment fairly well. Occasionally, the vernier or the tuner may have to be readjusted, especially if the character of the music, if one is listening in to a radio- phone concert, is changed materially. The filament rheostat may also be altered at times to improve the strength or the clarity of the music. When it comes to two- and three-circuit receiving sets, the tuning requires more care, otherwise the operation is the same. Again the tickler adjustment, starting at zero, is gradually increased until a position is reached just below the oscillating point. The oscillating condition is indicated by a soft hissing sound in the telephone. The final adjustments are maae with the vernier or verniers. Sometimes it may be found necessary to adjust the tuner and the tickler at the same time in order to maintain the proportion necessary to keep the receiver on the verge of the oscillating condition, which is the most sensitive one. The adjustment of the coupler will also be found most important, more so when one is endeavoring to cut 162 RADIO FOR EVERYBODY down interference to a minimum. After all, the main advantage of the two- and three-circuit receivers, over the single circuit regenerative receivers, is that they provide real means of eliminating troublesome interference. (NCOMINC vwwvww LOCAX. BEAT CURRENT 4AAaaAMaa/VVw' H^OOULATEO PLATE CURRet^r APPROXIMATE nUEPHONC CURRENT 0-$ How CW waves are detected, with an undamped receiving- arrangement. The CW wave is shown to represent the in- coming signals. The local circuit, employing a vacuum tube, is made to oscillate, producing its own wave or local current, which differs but slightly from the frequency of the incoming signals. This slight difference sets up a *'beat current." This beat current, in turn, modulates the plate current as shown, which is pulsating direct current, having been rectified from the alternating beat current. Finally the telephones slur the modulated plate current variations into the large pulsations indicated. Spark Signals and C W Signals The reception and amplification of spark signals will be most satisfactory when the regenerative action is con- trolled to a degree which will produce maximum ampli- fication without causing an oscillating condition in the RADIO FOR EVERYBODY 163 circuits. When the oscillating condition is reached, which is indicated by hissing noise, the tone of the spark signal will be destroyed and reception through interference will become virtually impossible. The tone of a spark trans- mitter, which means a damped wave transmitter, may be altered when adjusting the receiver from the plain de- tector action to the oscillating condition. That accounts for the fact why a transmitter, which is heard as a series of flute-like dots and dashes one moment, becomes a mushy but extremely loud series of dots and dashes the next. The flute-Hke sounds are the real sound values of the sparks, while the mushy sounds are the false sound values given to them by the oscillating action of the detector. What are known as continuous wave signals, including the interrupted continuous waves and the modulated con- tinuous waves, all of which are explained in the chapter further on dealing with continuous wave transmission, as wx'll as the radio-phone, may be received in like manner, but a special condition may be obtained by allowing oscil- lations to take place in the receiver, producing the exact frequency of the incoming wave length. This is known as the ''zero beat" method and in this condition amplification is greatly increased due to the augmented feed-back of energy from the plate to the grid circuit. It is only pos- sible to make use of this method while the incoming fre- quency remains constant, and its successful application requires considerable skill. In the reception of continuous waves the plate circuit feed-back or tickler action is to be increased to a point where oscillations are constantly taking place and this condition must be maintained throughout the entire tuning operations. The most successful means for reducing spark inter- ference while receiving modulated continuous wave sig- nals, including radio-phone, is the use of the zero beat method described above. This will cause the spark signal to become distorted and suppressed while greatly increas- ing the amplification of the desired signal. As the oscil- lating condition is a prerequisite in the reception of 164 RADIO FOR EVERYBODY continuous wave signals, it follows that spark signals are more readily suppressed than are the modulated contin- uous wave signals. Where the carrier wave length of the modulated continuous wave signal and the wave length of the undesired signal are almost identical, it may be possible to suppress the undesired signal by changing the frequency of the desired signal to the point where the carrier wave frequency of the modulated continuous wave signal is beyond audibility. The coupler adjustment also makes for additional freedom from spark interference. The elimination of continuous wave signals while receiving spark signals is easily accomplished by reducing the plate variometer or tickler dial settings until the oscillations cease, unless the continuous wave station is very powerful and located nearby. From Radio-Phone to Dots and Dashes Sooner or later, and better sooner than later, the radio enthusiast turns to dots and dashes because, after all. the radio telegraph still dominates the air as far as the volume of traffic is concerned. While the music and the radio- phone talks may be most interesting to the laity, the fact remains that many things of great importance are being missed if one does> not understand the telegraph code. Formerly, the Morse telegraph code was largely em- ployed in radio telegraph work in this country. At that time the Marconi land stations and ship installations used the Continental code, which is the present code, while the other radio organizations as well as the Government and amateur stations used the Morse code, which is the code used on our telegraph lines. However, in order to have a uniform code with the rest of the world, the Continental <:ode was finally adopted as the standard radio code. This code differs from the former Morse code in the fact that it has no spaces between the letters themselves. In the Morse code, for instance, the letter C is represented by dot dot space dot. The letter R is just the reverse, namely, dot space dot dot. Now, since there are spaces between the letters themselves, it stands to reason that the space Form 778 U Department of Commerce BUREAU OF NAVIGATION RADIO SERVICE INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS TO BE USED FOR ALL GENERAL PUBLIC SERVICE RADIO COMMUNICATION 1. A dash is eiqual to three dots. 2. The space between parts of the same letter is equal to one dot. 3. The space between two letters is equal to three dots. 4. The space between two words is equal to five dots. A . _ B _ . . . C , Period.... -. Semicolon . . . D _ . . E . Comma — . — . — F , G :, 11 Colon Interrogation . . . K FTrlfimaHnll pnlllt ApoKtrophp . _. . L . M Hyphen — .... — Bar Indlcatlnir fraction. — . . _ . P . . Parenthesis - . . . . n . _ . T_ AV . Underline Double dash Z . . Attention call to precede every trans- General Inquiry call — . — . . — A (German) . . i or A (Spanish-Scandinavian) From (de) — . . , CH (German-Spanish) Invitation to transmit (go ahead) t (French) . . _ . . 5i (Spanish) . (German) . I' (German) . . AVamlnp — ^hlpfi power . . . • , — . Question (please repeat after )— Walt . Break (Bk.) (double dash) _ . . . _ 1 . 2 . . .^ Understand — . 3 4 . . . . Error • ppr^lrpd (0. K.) . . 5 6 _ . . . , Position report (to precede all position messages) — . — . 8 , , End of each message (cross) . . 9 _, Transmission finished (end of work) (eoncluslon of correspondence). . 11—6860 Chart of the Continental radio code as now employed in all radio communicatioji. 166 RADIO FOR EVERYBODY between the dots and dashes forming a single letter must be shorter than those between letters, and it is this fea- ture w^hich makes the code more complicated and more liable to error than the Continental code, which has no spaces within the letters themselves. The Continental code may be readily mastered with a Httle patience. The best method to proceed in learning the telegraph language is to learn the code letters not so much by remembering the dot and dash combinations ^s by learning the sounds. In other words, when an operator listens to a telegraph message he does not notice the dot and dash combinations of each letter and then translate these combinations into the proper letter or numeral. Instead, he catches the certain sound or com- bination of each letter or numeral, and automatically his trained mind reads off the message in letters. The ■trained operator never thinks of the letters in dots and dashes, just as the reader, in reading this line of type, does not notice the letters in each word but recognizes words as complete units by their general appearance. In writing, the same is true. The rapid writer does not think of each letter as he writes; his words are his units, and he writes as he thinks. Therefore, the code must be learned by means of some instrument which simulates radio dots and dashes. For this purpose a simple buzzer operated by a battery and a telegraph key, may be used. Again, one can purchase a regular practice set, which has buzzer and key com- bined in one unit. A very ingenious little practice set is shown in the accompanying illustration, which contains a battery, buzzer, telegraph key, and a lamp for visual signals. The first step, once the practice set is at hand, is to learn the code letter by letter. The code is given in the chart on page 165. Note that A is a dot and a dash This is translated into a short snappy push on the tele- graph key followed by a longer push. The key should be held with the index and middle fingers of the right hand resting lightly but firmly on top of the knob, with the RADIO FOR EVERYBODY 167 thumb in light contact at the side or beneath the rim of the key knob. All characters should be made by wrist motion, with the elbow stationary, and all muscles of the arm and fingers should remain perfectly flexible. One of the most difficult things for the beginner to learn is proper wrist motion, which is so essential to good transmitting. The beginner should never start with the key knob close to the table, due to the fact that this will interfere with the forearm and free wrist movement. Transmitting in- volves a downward pressure on the key of short or long duration, it being unnecessary to do any elevating of the key as this is pro- vided for by the spring compression under the key. The beginner should first learn to recognize the letters of the Continental or International code in- stantly when heard, without conscious ef- fort. In order to ac- quire this knowledge he should start to send at a slow rate of speed, remembering that a dash is equivalent in duration of time to that taken for making three dots. When opera- ting the key, listen to the sound produced by the buzzer, or, if the practice set has a visual indicator such as a lamp, watch the flash produced by the blinker, as it is called. In a surprisingly short time smoothness and speed in both sending and receiving will be developed. In some prac- tice sets a head receiver is worn so that the buzzes are heard in the same manner as though they were received from a radio telegraph transmitter. Taking the telegraph code, the beginner should start with the first four letters, mastering them in turn. Thus, Buzzer practice set employed in learning the radio code. This little set is also provided witli a small lamp which gives visual code signals when desired. 168 RADIO FOR EVERYBODY the beginner will note by studying the code chart that dah de dah de — and not dash dot dash dot — is C, in- stantly, and that dah de de de is B. In other words, he learns what sounds represent each letter, and he does not stop to figure how many dots and dashes he has heard. It is left to the mind to perform two functions for each letter, namely, to think of the symbol and then the letter. It will be found that as the code is mastered, the letters will form in the brain automatically, and when this stage is reached the speed can be greatly increased. After mastering the first four letters, the beginner goes on to the next four. With these mastered, he repeats all the letters from the beginning again, and then passes on to the next four, and so on. It may require several evenings to memorize all the letters and numerals, and £nally one can go on to the various punctuation marks -and other characters. To recognize the symbols instantly, even when they are sent at slow speed, takes much longer, of course. Sending is much simpler than receiving. With all the symbols memorized, the beginner should sit down by the hour and translate newspaper articles or magazine articles or any other "copy" into the Continental code, using the practice set. In this manner he trains his ear to the various sounds, and after all the ma:stering of the code is just that, nothing more. The next step is one which presents two alternatives : Either the beginner can get in touch with some other be- ginner and spend some time each week transmitting mes- sages back and forth to each other by means of a buzzer practice set, or the beginner can listen in on his receiving set to the amateur transmitting stations, endeavoring to pick up letters here and there. The second method is not apt to produce immediate results, for the reason that ,much of the traffic is entirely too fast for the beginner. However, certain radio telegraph broadcasting stations have the beginner very much in mind these days, and transmit at a very slow speed in order to furnish prac- tice for the beginner. There are automatic machines 170 RADIO FOR EVERYBODY which send messages at any desired speed for training the beginner. This is an excellent self-instructor. One method of learning the code is to attend a radio school. The schools, thanks to their wide experience, have perfected methods of training beginners which produce early results. But in the main one can teach one's self if sufficient patience is exhibited. Listening to radio telegraph stations and attempting to jot down on paper as many letters as are recognized finally results in copy- ing more and more letters and words until perfection is attained. Aside from the telegraph code, there are certain abbre- viations that have been inaugurated by the International Radio Convention. The list of these abbrevations is pre- sented on the facing page, and while it may not neces- sarily be memorizd, it is well to remember the more im- portant ones. When and Where A Radio License is Necessary Having mastered the code and become a radio operator of more or less ability, a person can consider a trans- mitting set. Otherwise a transmitting set is out of the question, unless one has a licensed operator to run it. The owner of an amateur transmitting station must ob- tain a station license before it can be operated if the signals radiated therefrom can be heard in another state, and also if such a station is of sufficient power to cause interference with neighboring licensed stations in the receipt of signals from transmitting stations outside the state, which means that virtually all transmitters must be licensed. These regulations cover the operation of radio telephone stations as well as radio telegraph stations. Station licenses can be issued only to citizens of the United States, its territories and dependencies. Transmitting stations must be operated under the super- vision of a person holding an operator's license, and the party in whose name the station is licensed is responsible for its activities. Form T72 a. Department of Commerce BUREAU OF NAVIGATION RADIO SERVICE INTERNATIONAL RADIOTELEGRAPHIC CONVENTION LIST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION ANSWER OR NOTICB PRB QR\ QRB QUC QRD QRP QRO QRH QR4 QRK QRL QSP •QSV QSW QSX QSY QSZ QTE QTF Do yon wish to communicate by means of the International Signal Code! What ship or coast station la that? What Is yonr distance! What Is yonr true bcarln;! Where are yon bound for? Where are yon bound fromt What line eajing Is degrees from Yonr position is — latitude longitude. * Public correspondence ia any radio work, offidal or private, handled oa com- mercial wave lengths. _ When an abbreviation is followed by a mark of interrogation, it refers to the ques- tion indicated for that abbreviation. ii— «86o List of abbreviations now employed in radio communication for the purpose of saving time and trouble. 172 RADIO FOR EVERYBODY The Government licenses granted for amateur stations are divided into three classes as follows : Special Amateur Stations, known as the "Z" class of stations, are usually permitted to transmit on wave lengths up to approximately 375 meters. General Amateur Stations, which are permitted to use a power input of 1 kilowatt and which cannot use a wave length in excess of 200 meters. Experimental Stations, known as the "X" class, and school and university radio stations, known as the '*Y" class, are usually allowed greater power and also allowed the use of longer wave lengths at the discretion of the Department of Commerce, which has charge of the grant- ing of licenses and the enforcement of the radio laws. All stations are required to use the minimum amount of power necessary to carry on successful communication. This means that while an amateuf station is permitted to use, when circumstances require, an input of 1 kilowatt, this input should be reduced or other means provided for lowering the antenna energy when communicating with nearby stations in which case full power is not required. Malicious or wilful interference on the part of any radio station or the transmission of any false or fraudulent dis- tress signal or call is prohibited. Severe penalties are provided for violation of these provisions. Special amateur stations may be Hcensed at the dis- cretion of the Secretary of Commerce to use a longer wave length and higher power than general amateur sta- tions. Applicants for special amateur station licenses must have had two years' experience in actual radio com- munication. A special license will then be granted by the Secretary of Commerce only if some substantial benefit to the science of radio communication or to com- merce seems probable. Special amateur stations located ,on or near the sea coast must be operated by a person holding a commercial license. Amateur station licenses are issued to clubs if they are incorporated, or if any member holding an amateur operator's license will accept the responsibility for the operation of the apparatus. 174 RADIO FOR EVERYBODY Applications for operator's and station licenses of all classes should be addressed to the Radio Inspector of the district in which the applicant or station is located, or, if this is not known, to the Bureau of Navigation, Depart- ment of Commerce, Washington, D. C. The accompany- ing map indicates the territory covered by each radio district. Each district has a Radio Inspector, w^hose address is given below : First District Boston, Mass. Second District New York City Third District Baltimore, Md. Fourth District Norfolk, Va. Fifth District New Orleans, La. Sixth District San Francisco, Calif. Seventh District Seattle, Wash. Eighth District Detroit, Mich. Ninth District Chicago, 111. Once more, let it be clearly understood that no Hcense is required for a receiving set only or for the operator of a receiving set. However, all persons are required by law to maintain secrecy in regard to any messages which may be overheard. This is a blanket law, of course, intended to safeguard the interests of those transmitting and receiving private dispatches and special press reports, and does not apply to broadcasted telegraph and telephone service. Persons who wish to operate a transmitting set must apply to the radio inspector of their district for the neces- sary form and, at an appointed time, undergo an exam- ination which covers their proficiency in receiving and sending telegraph messages, as well as in the theory and practice of radio. Operator's licenses are of the amateur and commercial grade, depending on the proficiency of the person examined. There is no fee or charge for either an operator's or a station license. Every person engaged in any form of radio communi- cation should have a copy of a pamphlet, ''Radio Com- munication Laws of the United States," which can be £.W 176 RADIO FOR EVERYBODY secured by sending fifteen cents (not in stamps) to the Superintendent of Documents, Government Printing Office, Washington, D. C. The laws regulating the operation of private radio stations in Canada are different in several respects from those in force in the United States. For instance, a station which is used only for receiving must have a station license. For authoritative information, inquiry should be rnade of the Deputy Minister of the Naval Service, Ottawa, Ontario. Call Letters and What They Mean All radio transmitters have call letters. Just as auto- mobiles carry license plates with the State and a number plainly marked on them, so do all radio transmitting sta- tions use calL letters consisting of two or three or four letters and numerals. If one station wishes to call an- other station, it calls by means of the call letters of the desired station. The Government assigns call letters at the time the station license is granted. Every radio amateur should have a copy of the pamphlets ''Amateur Radio Stations of the United States," and "Commercial and Government Radio Stations of the United States." The price of each of the pamphlets is fifteen cents, and orders should be sent to the Superintendent of Docu- ments. These pamphlets contain lists of the amateur, and commercial and Government stations in the United States, and of the call letters assigned to the stations. A new edition of each pamphlet is published on June 30 of each year. A monthly publication called the ''Radio Service Bulletin" is issued which contains information regarding changes in the radio regulations and traffic. Chapter VI. MAKING BIG SOUNDS OUT OF LITTLE ONES, OR THE GENTLE ART OF AxMPLIFYING MUCH of the present success of radio depends on the amphfier apparatus now in use. The ampHfier is the instrument which makes possible the magnifying of Aveak signals or sounds in an electrical circuit. An incom- ing radio-phone wave may be so weak that the sounds cannot be heard in the telephone receiver, yet throw in one step or stage of amplification and immediately the sounds are loud and clear. The music or the talk as- sumes a depth and roundness that has been lacking when receiving with the ordinary detector circuit. Throw in another step of amplification or two steps in all, and the sounds are so loud that they can be heard when the telephone receivers are laid on the table. Or, a loud- speaking device may be hooked up and immediately the sounds are heard throughout the room without the aid of the telephone receivers. The amplifier has served to increase the range of all transmitters to an unbelievable extent. Thus with a given transmitter in the old days of crystal detectors, the usual range might have been say 100 miles. Today, thanks to the regenerative receiving circuit already described, which amplifies the signals considerably, and also thanks to a two-step amplifier, the same transmitter may operate a thousand miles with ease. Not that the transmitter is any the more powerful or more efficient than it was 178 RADIO FOR EVERYBODY formerly, but the receiving set, because of the regenerative arrangement and the amphfier, responds when the waves are that much more attenuated or weakened. From Transatlantic Radio to Transcontinental Telephone The amphfier is responsible for many of our recent achievements. For instance, the recent spanning of the Atlantic by twenty-nine amateur transmitters, usmg one kilowatt or less and a wave length below 200 meters, would have been impossible were it not for the highly efficient receiving equipment and amplifier employed by the American observer stationed in Scotland for the purpose of picking up the weak signals. An ordinary set would not respond to such signals, and the transmitters would be said, under such circumstances, to be incapable of spanning the 3,000 miles or more of space between America and Scotland. Yet with the proper receiving set and super-amplifier, the transmitters were found to span the intervening space with a varying degree of success. Which only serves to prove once more that no matter how weak the trans- mitter may be, its waves are propagated through space and keep on going farther and farther away with virtually no end. It may seem fantastic to believe that the waves from a little amateur transmitter when once started keep on going through space for years and years, until they may reach the moon and the distant planets ; but such must be the case. The whole problem is one of having a receiving set sufficiently sensitive to respond to the attenuated waves, and then an amplifier -^^hich can build up the signals to audibility. The amplifier principle is used in telephone work. The trans-continental telephone would not be the success which it is were it not for the vacuum tubes now em- ployed as amplifiers or repeaters. After going through many hundred miles of wire and becoming attenuated as a result, the weakened telephonic currents are passed througfh vacuum tubes in order to impress their charac- teristics on other circuits, which in turn have fresh and RADIO FOR EVERYBODY 179 powerful currents ready for another jump^ of several hundred miles. These currents, in due course, become at- tenuated in their turn, and again resort is had to vacuum tube devices. The vacuum tube has proved to be the most reliable form of telephonic relay or repeater ever DETECTOR AND AMPLIFIER FILAMENT \ RHEOSTATS. ! j DETECTOR- SWITCH TUNINO PANEL J Combination tuner and detector-amplifier set nuade up of two units mounted one above the other as shown. This comprises an excellent receiving set, with detector and two-stage ampli- fier completely self-contained. developed, working with virtually no distortion when properly designed and handled. In the previous chapter we had something to say re- garding the action of the vacuum tube. We learned of the flow of electrons or ions from the hot filament, and how this flow of electrons or ions formed a one-way bridge for the B battery current connected with the tele- Y vO H'I'I'I'I'I'I'I'I*- \siMjmj r-|l|l 1 1 1 l|l 1 CO T \<^/ ' UUUMiL HiNi|«|i|i|i|i|»— ^^^"^^^^"^^ cQ H 5 fl S^ aj rt 35 -OS fl 11 * T 2 - i SI fci .5 5 3 « si « 9 S •"« - as OS a S I -S-^ 4>0 « ©-§ .2 5 g i> 5S 2tt *• fc, «5 4, !8 © III A RADIO FOR EVERYBODY 181 phones. And the grid, as we learned, is the control for the traffic over this one-way bridge. In the case of the amplifier tube, the grid is again employed as the control Instead of using a pair of telephone receivers in the plate circuit of the receiving set, the two leads or "out- put" terminals are brought to the amplifier apparatus, as shown in the accompanying diagram. The first step is to pass the receiving circuit current through the primary of a special amplifying transformer. Such transformers are available in many different styles but all serve the same general purpose. They are sometimes called inter- valve transformers. The secondary of the transformer is brought to the grid and to the filament of the amplifier tube, as shown. The plate circuit of the amplifier tube contains a B battery of higher voltage than the detector B battery, and the telephone receivers. However, if an- other stage or step of amplification is desired, then the plate current from the first tube is brought to the primary of a second amplifying transformer, and the secondary is connected with the grid and filament as before. This second amplifier bulb has a B battery and a pair of tele- phone receivers or the loud-speaking device, as the case may be. A third step may be added in the same manner. Three steps or stages of amplification are considered the limit in actual practice, for the reason that beyond that point tlxe adjustment of the circuits becomes too difficult for satisfactory work. Please note that the same fila- ment and B battery may be used for the detector and the amplifier tubes, but for the sake of simplicity most of our diagrams show separate batteries being used for each tube. Whereas the amplifier tubes and detector tubes may look alike, they are quite different as far as the electrical characteristics are concerned. Amplifier tubes are not critical in adjustment when compared with detector tubes and they will operate successfully on plate voltages of 40 to 80 volts. Where a detector and two stages of ampli- fication are used, three 22^ volt units may be connected 182 RADIO FOR EVERYBODY ■(ENT RriC05T.MS iNTdRVA^vt T»!«F RS Tl'Bt S.OCKET5 Simple mounting for a two-stage amplifier, comprising the fila- ment rheostats, the intervalve or amplifying transformers, and the tube sockets. in series and connections to the receiver made in a manner which permits the use of the full voltage on the amplifier tubes while a variable portion of the same battery is used for the detector tube, say anywhere from 16 to 22 volts. Where extremely loud signals are desired the plate voltage may be 100 or over ; and while such high voltage will not damage the amplifier, it will increase tube noises, and is therefore not desirable when receiving signals with the telephone head set. No more than 45 volts is required even with several pairs O'f head phones. An amplifier tube which requires a critical plate voltage or filament current adjustment wili not give consistently satisfactory results as an amplifier. Tubes of this charac- ter will generally be found useful as detectors. Audio or Radio Frequency — Which? The amplifying arrangements described so far, and for that matter the greater part of the amplifying apparatus RADIO FOR EVERYBODY 183 now available and in regular use, is known as the audio- frequency type. It is called the audio frecjuency type for the reason that it is handling currents of frequencies well within the audible range. There is another type of amplifier known as the radio-frequency type, which, up till the present time, has been rarely used. However, at this writing the radio frequency type is rapidly coming into general use for long-range reception, as well as in connection with loop antennae and diminutive antennae of all kinds. In the case of audio-frequency amplification, the amplifying is done after the signals have been passed through the detector and rectified so as to produce audio- frequency currents, while with the radio frequency ampli- ORiD !_EAK AND CONDENSE^ HOLES foR i^^°"^ FREQUENCYJ CONNECTIONS Components of a combination radio frequency amplifier, vacuum tube detector, and audio frequency amplifier, mounted in a neat steel cabinet. 184 RADIO FOR EVERYBODY fier the waves are amplified before they are passed to the detector. The advantage of the radio-frequency ampHfier lies in the fact that it amplifies only the wave and not the many little irregularities and imperfections which exist in. the usual receiver and amplifier equipments. Further- more, most detectors have a critical point at which they FILAMENT RHEOSTATS WiNOOW \FOR AMPLIFIER TUBE.3 "^^"-^^-^ FOR DETECTOR OR AMPLiFiER CO.MNECTfON Two-stage audio frequency amplifier, with filament rheostat handles, switch handle for connecting: the detector alone, or one stage or two stages of amplification into the circuit, as well as the input, output, and filament current binding posts mounted on the front paneL begin operating. Signals which come in weaker than the critical point of the detector make no impression on the detector, and are therefore lost entirely. No matter how many steps of audio-frequency amplification may be piled up behind the detector, the signal which has failed to- RADIO FOR EVERYBODY 185 actuate the detector will certainly not be heard. With radio- frequency amplification, on the other hand, there is virtually no critical point, and even the weakest signal is built up to the desired degree before it is passed on to the detector, there to be rectified to audio-frequency cur- rent, which, if desired, can be passed on through one or more stages of audio-frequency amplification in order to build up the signal strength. In extreme long-distance work, it is not uncommon to ^0-60 VOLTS b I 6 VOLTS a Resistance type of radio-frequency amplifier. Tlie set of wires b are for tlie plate battery current, with the polarity indicated, while the a set indicates the filament battery current. The wire marked 1 is the grid wire from the tuner. R are the filament rheostats; Rl, 2 are resistances; Am are ampli- fier tubes; D is the detector tube; FC — fixed condenser; T — telephones; VC — variable condenser. find two stages of radio-frequency amplification, followed by a detector and two stages of audio-frequency amplifi- cation. When using a loop antenna, it is usually necessary to employ radio-frequency amplification unless one is near the desired transmitter. The radio-frequency ampHfier builds up the wave energy before passing it on to the detector, and in that manner enables one to hear signals which would not affect the detector otherwise. After all is said and done, it is really the radio-frequency ampli- fier which makes for extreme sensitiveness in the receiv- 186 RADIO FOR EVERYBODY ing set, and enables almost urtbelievable distances to be spanned, while it is the audio-frequency amplifier which makes for loud signals and for the successful operation of loud-speaking devices. The simplest type of radio-frequency amplifier is known as the resistance-coupled type, and is shown in the wirins^ diagram on page 185. In this arrangement the amplifying transformers are replaced by suitable resis- tances and condensers, the amplified energy bemg passed from one circuit to the other by means of the resistance coupling. This method is preferable in many instances because of its simplicity and because of the fact that the radio or the audio frequency can be amplified at will. If the grid condenser is eliminated on some of the tubes in a multi-stage amplifier, as shown in the diagram on page 185, then the incoming radio frequency is amplified before it is rectified, and after it is rectified by going through the detector tube it is then amplified again at audio frequency in order to obtain volume of sound. Amplifying at radio frequencies, although it is rather diffi- cult to do so at times, has numerous advantages and the experimenter is urged to try amplifying at radio fre- quencies wherever possible since one of the principal advantages of this method is that radio frequencies are inaudible to the human ear and the amplifying action is therefore carried on without unpleasant noises to the listening operator. By using special transformers the transformer method ■can be applied to radio frequency amplification, reducing it to something almost as simple as the audio- frequency amplifier. There have been introduced of late special radio frequency transformers which function over the wave length band of 200 to 5,000 meters, and which have been designed particularly for the short wave band of 200 to 500 meters. These transformers mark a real step forward in the art, and must make for the wide appli- cation of ithe radio frequency method of ampHfying. This method of amplification doubles and triples the receiving ranges ; it makes signals audible that cannot be received o vjjkftjuu — i^ ■oinnnnr 03-=- X MSiSlSlSU r-nmnnrr\ } ^ft 188 RADIO FOR EVERYBODY with other types of ampHfying circuits ; it is vastly superior to any other method of amphfying telephone speech ; it eliminates tube noises ; it increases selectivity ; it increases signal audibility at each stage at least twenty times; it makes possible the use of small loops or frame antenna to receive as well as with high antennae ; and it gives a 20-watt amateur radio telephone set the trans- mitting range of a transmitter of several times the power. Please note that radio-frequency amplification can be used in 'Connection with any existing receiving set, even if said set is of the simplest and most elementary type. Another radio-frequency arrangement. VCl — variable con- denser in aerial-ground circuit; LiC — loose-coupler or vario- coupler; VC2 — variable condenser across secondary; Am — amplifier tube; Kl, 2, 3, 4 — rheostats; PS — primary and sec- ondary of intervalve or amplifying transformer T; GL, — grid leak; D — detector; B — plate battery; A 1 and 2 — filament bat- tery; rc — fixed condenser; T — telephones; TICK — tickler coil; G — ground. For radio-frequency amplification builds up the wave strength before it is passed on to the detector, so that in every sense of the word it is as though the receiving set were moved a considerable distance towards the trans- mitter. Thus a crystal detector can be used in conjunction with the radio-frequency amplifier, for after the wave strength has been built up by the radio- frequency ampli- fier, it is rectified by the crystal detector. Then, if de- sired, the rectified current from the crystal detector can be amplified by means of audio-frequency amplifiers. RADIO FOR EVERYBODY 189 Sometimes the crystal is employed in this manner, for the reason that it is silent in its operation and is not apt to introduce noises into the circuit. When and Where to Use an Amplifier Most receiving sets are complete without an amplifier. In other words, the amplifier is something apart from the regular receiving set ; it is an accessory ; it can be added at any time to the usual run of receiving sets. So the question arises as (to when and where an amplifier should be employed. The amplifier of the audio-frequency type, which is the type generally used, should be employed when loud sig- nals are required. Take the case of the radio-phone service, for instance. At a reasonable distance the music and talk come in good and clear, but it cannot be denied that ithe music and talk are generally thin, so to speak. The music or the talk has no depth, no sense of realism. It seems to be in one plane, just like the motion picture is in one plane when viewed on the ordinary screen. It lacks the depth so necessary for realism, even though it may be quite loud. x\t least those are the author's obser- vations, as well as those of many persons who have listened in on his receiving set. However, the moment the amplifier is used, even with one step, there is introduced a loudness and clarity, as well as depth, which make for realism. These features are particularly noticeable in the case of a radio chapel service, where the minister may be preaching and is followed by the choir. Without amplifiers, the voice of the minister and the voices of the choir are on the same plane, but with the amplifier we obtain a sense of depth and the entire rendition sounds as though it were in a large church. So the amplifier, then, makes for better results, let alone loudness. Fortunately, an amplifier is not such an elab- orate piece of mechanism. It consists merely of a vacuum tube of the amplifier model, a filament rheostat, a transformer, and the necessary batteries and connections. Like the vacuum tube detector, it requires a filament 190 RADIO FOR EVERYBODY battery and a high-voltage B battery. When telephone head sets are to be used, only 45 volts is required for the B battery. In that case two B battery units of 22/4 volts each are connected in series, and a tap is taken from the connec- tion between the units and brought to the de- tector in order that the detector will not have more than 22^ volts, while the amplifier will have the full voltage. It is well to mention here that a variable voltage battery should How the radio-frequency amplifier is used with the loop antenna for long distance reception. VC 1 — variable con- denser across loop terminals; L. 1 and Li 2 — inductance coils; VC 2 — variable condenser; FC — fixed condenser; Am — amplifier tube ; D — detector tube ; T — telephone receivers ; B — plate bat- tery; A — filament battery; K 1 and 2 — filament rheostat. Note the extra resistance. RADIO FOR EVERYBODY 191 be used for the detector, since a good detector tube has a critical voltage adjustment for the B battery, and a fixed voltage battery for the other unit. Some battery manu- facturers are now supplying a combination B battery of 45 volts, with part of the battery made variable so as to obtain the critical B battery voltage for the detector. Amplifier units can be purchased at a reasonable cost. Thev come in one-stasre and two-stas^e models, and in some instances a three-stage model can be obtained, al- though this model is rare for the reason that its adjust- ment calls for considerable skill as compared with the one and itwo-stage models. Then again, there are units avail- able in which the detector is included. Thus one can obtain a detector and one-stage model, and a detector and two-stage amplifier model. Fortunately, the same storage battery is employed for the detector and the amplifier tubes, just as the B battery is used for all the tubes of one set. This simpHfies the problem and makes for economy. A so'ft or gassy tube, known as a detector tube, should be used for the detector, while hard or highly exhausted tubes should be used for the amplifiers. However, in some sets where a single rheostat may be employed for the detector and amplifier tubes, and a rigid B battery voltage is used on all tubes, it is sometimes good practice to use amplifier tubes throughout, including detection. This is not the most efficient practice, but it makes for simplicity, since amplifier tubes do not require the delicate manipulation and adjustment that are called for with soft or gassy tubes. Of course, the sensitiveness w^hen using amplifier tubes throughout is bound to be greatly reduced, for it is the delicate adjustment of the gassy tube which makes it so highly responsive to weak signals. The Question of Loud Speakers Sooner or later the radio enthusiast wants to do away with head 'phones in order that the radio-phone service 192 RADIO FOR EVERYBODY may be used for danc- ing or even for enter- taining a roomful of persons. In that event some form of loud- speaker must be used. The simplest form of loud-speaker is one which makes use of the existing receivers, without extensive al- terations of the re- ceiving and amplify- ing arrangements. There are horns avail- able which may be fitted to the regular telephone head set. These horns are pro- vided with soft rub- ber pieces or even with clamps, so that the regular head set may be held in place while the sounds from both receivers travel up through a horn and are amplified so as to be audible some distance away. These devices are excellent in a limited way, and their main attraction is the fact that they can be used without alteration of any kind. However, where something of a more ambitious nature is wanted, it becomes necessary to use special loud- speakers. The simplest loud-speakers are those which .make use of a single telephone receiver of the same .general type as those used with head bands, as well as a special horn. There are all kinds of devices of this gen- eral class, ranging from horns of pressed paper or wood pulp, made in the general form of the channels of the human ear, and pressed copper reflectors, as well as horns of a more conventional design. liOud-speaker attachment that fits on the tone-arm of any phonograph so that the usual horn of the phonograph is used to amplify the sounds. RADIO FOR EVERYBODY 193 One of the most popular forms consists of a specially designed metal horn mechanically attached to the mechan- ism of a special telephone receiver, in which the stand- ard mica diaphragm has been replaced by a strong corru- gated metal diaphragm which will stand practically any amount of abuse without damage. A large amount of experimental work was carried on by radio experts before final decision was made on the horn and it is believed that the design furnishes as fine a quality of reproduc- tion as can be obtained except through the use of a very elaborate sound chamber such as is found in high- priced phonographs. The loud-speaker in question, which is shown in the accompanying illustration, will work satisfactorily from a two-stage audio-frequency amplifier and, using good amplifying tubes, 150-200 volts may be used without damage to the instrument. By good tubes is meant, in this case, especially ''hard'' tubes. The usual am- p 1 i f y i n g tubes are operated on 45 volts, and this voltage will produce only weak re- sults with the usual loud-speaker. If more B battery is added, such as by connecting a third and even a fourth unit to the usual B battery, the results may be poorer with the regular am- plifier tubes. Some radio workers use the 5-watt trans- o^^ ^f ^he several loud-speakers now mittinc'" tubes as am- available for home use. This model ..^ ^ . 1 • 1 may be used in connection with any plmers, m which case two-stage ampUfier. 194 RADIO FOR EVERYBODY voltages up to and even exceeding 100 volts may be ap- plied. In such an arrangement it is well to try the 5-watt tube in the second stage of amplification, and to use the regular amplifier tube in the first stage. One form of loud-speaker which is proving very popu- lar is a simple telephone receiver of special construction which may be attached to the tone arm of the usual phono- graph. In this manner one saves the cost of a special horn, and at .the same time one has the pleasure of hearing the regular phonograph do duty as a radio re- ceiver. The results with such an arrangement are very good, and the volume may be made extremely great by using sufficient voltage on the telephone. Loud-speakers require plenty of voltage, and there is no getting away from this fact. The simple devices which take the the regular head sets or single receiver operate ofif the regular amplifier output without changes of any kind ; but when it comes to filling an entire room with loud music or talk, the problem becomes quite complicated and certainly expensive. All of which brings us up to the problem of real loud- speakers such as are used in the most ambitious kind of radio reception, as well as for public speaking and other work. Hence this subject is worthy of treatment at length, including a ILttle back history. Loud-speakers of this kind are known as electrodynamic receivers. The Early Days of the Electrodynamic Receiver In 1911 two inventors, E. S. Pridham and P. L. Jen- sen, were actively affiliated with the development of arc radio transmission and reception at Napa, California. During the course of work, they made a very exhaustive study of various methods for the reception of rapid radio signals. Naturally enough, the development of what is known as the string galvanometer was carried out, and it was while conducting these experiments that several new and improved receiving devices were built. Among them was the first step in the development of the electro- RADIO FOR EVERYBODY 195 dynamic receiver, now well known for its loud-speaking characteristics. This early type was built along the lines of a modern voltmeter, with a revolving coil in a magnetic field at- tached by lever action to a diaphragm. This, however, was not a success as a telephone receiver, and while it Special power amplifier, used in connection •with extra power- ful loud-speakers such as are employed for projecting the radio- phone entertainment in a large hall. This amplifier is used in addition to the usual amplifier of the receiving set. did reproduce the voice with remarkable distinctness, it was not nearly loud enough, or even as loud as the or- dinary electro'magnetic type. While this instrument was not important in itself it was to be taken into considera- tion as the forerunner of the practical electrodynamic reproducer of today. 196 RADIO FOR EVERYBODY After many experiments with the revolving coil, the idea was definitely given up and a new line of experiments started. The next instrument developed was the true electrodynamic loud speaker or receiver, although it was not known at that time that it had loud-speaking character- istics. Two very large electromagnetic structures were made, and a small coil of fine wire wound on mica about three inches long by one inch wide, and very flat and thin, was also introduced. This coil was suspended in the air gap of the two electromagnets, rigidly attached to a diaphragm. The coil was located in such a way that both the three-inch sides of the flat coil were in a strong mag- netic field of the proper polarity when the magnets were energized. Both sides of the diaphragm were enclosed and ear tubes led out, one side for each ear. The total weight of the receiver was about sixty pounds. At once it was found that this new receiver had different internal characteristics than the electromagnetic type of reproducer. In spite of the great weight oif movable parts attached to diaphragm alone, about two ounces for the movable coil, it was found that the new instrument gave better speech reproduction from weak impulses than the ordinary receiver. Overtones were held, consonants and sibulent sounds were reproduced perfectly; in short, the quality of the speech was a revelation. But in spite of the fact that this instrument responded to impulses weaker than those necessary to affect t:he electromagnetic type of receiver, its loud-speaking qualities were still undiscovered ; in fact, they were not yet developed in this particular instrument. A number of experiments were performed with this instrument which were at that time nothing short of re- markable. The two inventors realized that there were great possibilities in the principle and proceeded to try out the new type against existing telephones. On a trip through the East in August, 1913, one of the inventors remained in Denver, Colorado, while the other proceeded 198 RADIO FOR EVERYBODY to New York City. Arrangements were then made to get a through telephone connection from New York to Denver. Such arrangements, h o w - ever, were not fav- ored by the telephone companies as articu- late speech was not possible over that dis- tance of straight wire. It must be remem- bered that this was be- fore the day of vac- uum tube repeaters and that line condi- tions were very bad over long distances. After three days the connection was made, and although the in- ventors were warned by the telephone com- panies that they would not be able to under- stand each other, very satisfactory speech was carried on using the electrodynamic telephone. At the same time, nothing could be understood over the receiver as ordinarily used. This test proved to the inventors that their device had merit, and that the next problem was to so condense and re- A popular small sized type of loud- speaker employed with the usual two- stage amplifier of the radio receiving: set. A 6-volt storage battery is used to energize the field coils. RADIO FOR EVERYBODY 19^ design their receivers so that it would be commercially practical, for complete it weighed 60 pounds. This original receiver had a moving coil wound to 70 ohms resistance, so that it might be interchanged with the ordinary 70-ohm magnetic receiver. This amount of wire, however, was one of the things which made up the weight of the moving parts, and in order that these moving parts might be made as light as possible, the moving coil was cut down to 20 ohms resistance and a proper induction coil supplied to fit it. The coils were still wound fiat on a mica sheet, but in or- der to reduce still fur- ther the weight of the complete instrument, one of the electromag- nets was done away with and the little coil was found to function perfectly with only one side of the coil in the magnetic field. This type was finally developed, and was the first of the electro- dynamic receivers to be commercially suc- cessful, out of all the types which had been developed by the in- ventors thus far. This tvpe was brought out in July, 1915. Immediately the re- sistance of the mov- able coil was reduced, it was found that the receiver had loud- Another type of loxid-speaker, larger 4 • 1 , . than the one shown on the facing page Speakmg cnaractens- and intended for a medium-sized hall. 200 RADIO FOR EVERYBODY tics, and still retained its perfection of reproduction of speech. It was then realized that no loud-speaker could be expected to give forth loud speech unless sufficient modulated current was supplied to it, so it became neces- sary for the inventors to turn their attention for a time to the development of a transmitter for use in conjunc- ion with the electrodynamic receiver. A transmitter was . ... , POLE PIECES \^^^ i^ 1 1 'wA 1^ '-Bi Diaphragm MOVABLE COIL The mechanism of the electrodynam^ic type of loud-speaker, • consisting: of the pole pieces of the electro-magnet, the movable coil, and the diaphragm. accordingly built that would pass a little over one ampere of modulated voice current and deliver that amount to the induction coil supplying the movable coil, attached to the diaphragm. It was found that this transmitter in conjunction with the electrodynamic receiver would give a volume of sound that was enormous and which would carry for blocks even though the original speech was no louder than a person would ordinarily talk. This, then. RADIO FOR EVERYBODY 201 was the final stage in the electrical design of the electro- dynamic receiver, and whatever subsequent improvements were made were along the mechanical rather than on the electrical characteristics of the apparatus. Limitations of the Ordinary Telephone Receiver The ordinary telephone receiver such as is used on our present-day telephone lines operates on the electromag- netic principle. The voice current passes through a wind- ing on a permanent magnet, changing its flux intensity and consequently its pull on a diaphragm placed directly over the pole ends. Its weakness lies in the fact that if the diaphragm is placed at a distance away from the pole pieces the magnetic influence is greatly lessened, and if placed too close the diaphragm hits the poles. A com- promise position is selected whereby the diaphragm is placed at such- a distance from the poles to allow it some motion before hitting the poles, and yet near enough to get a fair magnetic pull. Another weakness is that the diaphragm is under tension always and has to be made stilt to withstand this tension. All types of receivers using the electromagnetic principle will give forth sound only up to a certain point and then the diaphragm will hit the poles. In the electrodynamic receiver the diaphragm is in no way directly concerned with the magnetic flux. There are no pole pieces to interfere with motion, which may be as great as the elastic limit of the diaphragm. A large horn attached immediately above the diaphragm provides the air column for the diaphragm to move. In the present instrument the field is magnetized to a point approximat- ing 20,000 Hues per square centimeter with a current of .6Q amperes flowing in the field coil. The movable coil, w4th a resistance of 20 ohms will take car.e of approxi- mately 10 watts of modulated current as supplied by an amplifier through the proper step down coil and will give off sound accordingly. When it is remembered that only an extremely small fraction of a watt is necessary to pro- 202 RADIO FOR EVERYBODY duce an audible signal, some idea may be realized of the volume of sound generated by this instrument, produced by the flow of ten watts. It must be remembered also that due to the electrodynamic principle involved, all of the incoming energy is transferred into air vibrations, and that the instrument is not only capable O'f producing loud responses to large inputs, but also is superior for clear articulate response to very small currents and is fully as sensitive if not slightly more so in this respect than the best design of electromagnetic receivers. Commercial development of this type of receiver pro- ceeded along several interesting and different Hues. For receiving telephone speech alone, without loud-speaking characteristics, with a 70-ohm coil, a receiver was built using permanent magnets to be used on ships and in marine stations where communication was difficult. This type of electrodynamic telephone, using a double ear tube arrangement from the diaphragm, has become standard equipment of United States Navy destroyers for marine telephone communication and is being used on hundreds of merchant vessels for the same purpose, in conjunction with the anti-noise transmitter. The receiver can easily he made water-tight and its clearness of reproduction makes it indispensable for talking to the noisy engine room of any vessel. A phonograph attachment was developed and placed on the market in 1916 and consisted of an electrodynamic receiver of the loud-speaking type, and its horn, a control box containing the proper induction coil and switches to control the current of the device, and a transmitter tone arm. Many and varied were the experiments necessary to determine the proper location of the transmitter on the phonograph tone arm in order that needle scratch be eliminated, and yet perfect reproduction of the music be maintained. This equipment was also supplied with a hand transmitter in order that speech might be amplified by the same instrument. The voice and music from a phonograph can thereby be amplified enormously for out- door use. RADIO FOR EVERYBODY 203 Making the Speaker's Voice Carry for Miles Power vacuum tube amplifiers were built and at present the apparatus is such that voice, words and music have been transmitted through the air for over ten miles under favorable conditions and a very satisfactory arrangement made whereby speakers need not hold the transmitter in the hand, the amplifier being so sensitive that it will pick up impulses through a collecting horn and ampHfy them, for the assembled audience. At the same time the electro- dynamic receiver was modified mechanically and the flat coil changed into a circular one, still, however, moving in a strong magnetic field, and unchanged electrically. For radio signal amplification and broadcasting, the receiver is identical with the exception that the step-down coil is \yound to adapt itself to the receiving circuits of a wireless receiving set. With ordinary radio type vacuum tube amplifiers signals are received in such volume as to make the use of head phones unnecessary, and also allow •these signals to be heard by large numbers of people. It is especially popular in the reception of radio telephone speech and music. The public and commercial history of this electro- dynamic receiver, is very interesting. The inventors could have done no better when they called the device the "great voice," deriving the name magnavox from the Latin words magna and vox. It is truly the great voice and has had a profound influence in public affairs during the last few years. Its initial bow to the public was made Christmas Eve, 1915, at the Municipal Christmas Tree Celebration at San Francisco, California. That it fulfilled the expec- tations of the inventors may be fully realized in the words of the San Francisco Bulletin of the following day — "The slender tone of a single violin plainly heard a mile away ; Tetrazzini's voice on a phonograph record resound- ing from end to end of the vast stadium; the words of Thos. W. Hickey reading Lincoln's Gettysburg address reverberating like the roar of a giant ; a piano solo resem- bling the chimes of Westminster Abbey, played by a Co- 204 RADIO FOR EVERYBODY lossus of Rhodes — these things made possible by the new invention." After this first demonstration, attended by 50,000 peo- ple, the electrodynamic receiver has officiated at nearly every large gathering of public importance since the war, where speakers needed amplification of the voices. During the war no demonstrations were made because of the great pressure of government orders in the factory. Several notable examples are as follows : Ex-President Wilson spoke at San Diego to 50,000 ; at Reno to 6,000 in three different theatres at the same time. The Prince of Wales spoke to thirty thousand also at San Diego. The Victory Loan was opened by an aviator delivering a speech by radiophone and magnavox to 30,000 at Washington, D. C. President Harding and his political opponents used the electrodynamic loud speaker constantly during their cam- paign to talk to crowds varying from 40,000 to 100,000 in the case of ex-Governor Cox at Sheepshead Bay. Many other instances may be cited where this apparatus has made it possible for a single speaker to address enormous crowds. The electrodynamic principle involved in the construc- tion of these loud-speakers is perhaps the only satisfactory principle by which a loud-speaker may be constructed to give great volume from one instrument. There is prac- tically no limit to the sound which can be given off by the electrodynamic receiver, and this volume of sound is directly proportional to the input of modulated voice cur- rent. At present the instrument will satisfactorily take care of 10 watts of power through the movable coil and would take care of more if an amplifier were built to give more than this amount in its output. With 10 watts in the receiver coil, however, an individual has no trouble in speaking well over a mile distinctly and can talk to as many people as can conveniently assemble. Chapter VII. TRANSMITTING THE DOT AND DASHES OF THE DAMPED RADIO TELEGRAPH FOR those who are satisfied to listen to what others have to say and make absolutely no reply, a receiving set is all that is required. And the great majority of radio enthusiasts never go beyond the receiving stage, because they are satisfied to receive the radio-phone concerts and news, as well as the dot-dash messages of Government, commercial and amateur stations alike. When the radio enthusiast desires to do a Httle "talking"" on his own account — when he tires of Hstening to others or when he wants to be able to take a hand in any discussion that may be taking place in the ether — he must resort to a transmitter of some sort or other for generating the waves that serve to affect the apparatus in distant receiving sta- tions. He may wish to send in dots and dashes, or again, he may desire a radio telephone transmitter in order that he may actually talk and have his voice heard at distant points ; but in either event he must go through the for- malities of obtaining a station license as well as an oper- ator's license, both of which were unnecessary when he confined his efforts to receiving. In this chapter we shall deal only with the simple radio telegraph transmitters, leaving the more advanced types and the continuous wave apparatus, which makes radio telephony possible, for the next chapter. Please note, however, tfiat most radio ama- teurs are now turning to the C. W. type transmitter, and that spark or damped wave sets must -soon become obsolete. 206 RADIO FOR EVERYBODY What the Radio Transmitter Does Electromagnetic waves, by means of which radio com- munication is carried on, are produced by the transmitting apparatus. Power must be suppHed by some kind of electric generator or battery ; this power must be converted into high frequency currents by means of an oscillator or wave generator; and the high frequency currents must be introduced into an aerial system consisting of the aerial and the ground connection, in order that the radio waves may be propagated in all directions through space. Now the radio waves, as we have already learned, may be of the damped or the undamped variety. Damped VVWWWWl A schematic comparison between damped and undamped waves. The damped waves, shown above, consist of w^ave groups or wave trains, while the undamped or CW waves are of uniform height and wave length and without a break. waves consist of groups or trains of oscillations repeated at regular intervals, the amplitude or voltage of the oscil- lations in each train decreasing continuously as shown in the accompanying diagram, where the center line indicates O potential, and the length of the line the lapse of time. The number of these waves or trains per second is some audible frequency. When such waves strike a receiving apparatus, as we have already learned, they cause a tone in the telephone receiver. Signals are produced by means of a sending key, which lets the trains of waves go on for a short time (producing a dot) or for a longer time (pro- ducing a dash). The operator manipulates the key in order to form the dots and dashes which represent the desired letters, numerals, punctuation and other char- acters of a dispatch. RADIO FOR EVERYBODY 207 The principles of damped and undamped waves are the same in many respects, so that much of what is told regarding damped wave apparatus applies to undamped waves as well. Particular attention is first given to damped waves, as the apparatus is simple and easily ad- justed and has long been employed. Damped oscillations or weaves are produced when a con- denser discharges in a circuit containing inductance. The condenser is discharged by placing it in series with a spark gap and applying a voltage that is high enough to break down or spark across the gap. Such an arrangement is presented in the diagram on page 208, where a trans- former, supplied with current from a generator or battery, charges the condenser placed across its terminals until the condenser charge has been built to a point where the spark gap breaks down. It is as though one were stretching a rubber band, thus storing up considerable mechanical energy, until the breaking point was reached. Then, as the rubber band snapped, all the stored up energy would be discharged. When the spark gap breaks down the pent up energy of the condenser is discharged. Unlike the rubber band, how^ever, the charge in the condenser dis- charges across the gap and recharges the condenser in the opposite direction to almost the same extent as before, followed by another discharge w^hich again charges the condenser in the original manner but of still less extent, followed by still another discharge, and so on with the current going back and forth just as does any pendulum which has been given a push, until its swings or oscillations become weaker and weaker and the pendulum comes to rest. In discharging, which only requires the fraction of a second, the current passes through the inductance and sets up electric oscillations which are damped out or, to put it another way, soon reach zero. These discharges, which follow each other in such rapid succession, form the groups or trains at regular intervals. Now the standard generator frequency for most radio 208 RADIO FOR EVERYBODY work today is 500 cycles per second. This causes the con- denser to charge and discharge 1,000 times per second, or once for each positive and once for each negative maxi- mum if the spark gap is of such a length as to break down Inductance Power 3ou rc€ T^^^Sf^mcr ^P"'^ <^°P The simplest kind of damped radio wave generator, consisting of a power source, an induction coil or transformer for stepping up the current, a condenser, a spark gap, and an inductance. The charging and discharging of the condenser through the in- ductance and across the spark gap sets up the oscillations or radio waves. at the maximum voltage given by the transformer. The number of sparks per second is called the spark frequency. With the standard spark frequency of 1,000 per second the amount of power the set sends out is considerably greater than it would be at the low rate of 60 cycles per second, because the transmitted radio waves are more nearly continuous. The radiated wave trains strike a receiving antenna more frequently and their amplitude does not need to be as great to produce the same effect as stronger waves received at longer intervals of time. The higher frequency produces a tone in the receiving tele- phones that is more easily heard, because the ear is more sensitive to sound waves of about 1,000 per second and also the tone is more easily heard through atmospheric disturbances. A 60-cycle supply may be used if the num- ber of sparks per second is increased by the use of a rotary spark gap giving several sparks per cycle, as will be described further on. RADIO FOR EVERYBODY 209 The Simplest of Transmitters Nothing could be simpler than the arrangement shown in the accompanying diagram. Indeed, in the pioneer days of radio such a hook-up was employed for covering distances up to 100 miles with a 10-inch spark coil, and back in the crude beginnings of amateur radio most ama- teurs made use of a spark coil and the plain aerial arrange- ment here shown. In those days the transmitters were gaged by the inch; that is to say, the amateur talked of his transmitter by referring to the sparking distance of his coil. Thus he had a two-inch, three-inch, ID-inch and so on set, according to his monetary resources or construc- tive ability as the case might be. The simplest form of damped radio transmitter, consisting: of a po-wer source, telegrapli key for making: long: and short signals of the radio code, a transformer for stepping: up the current, a spark grap, and the aerial and the g:round. In this arrangement, known as the plain aerial transmitter, the aerial and ground comprise the condenser. The arrangement shown in the diagram comprises a source of power, a means of raising the low voltage to a high one, say of 20,000 volts, which is sufficient to spark 210 RADIO FOR EVERYBODY across a one-inch gap between needle points, a simple spark gap, a telegraph key for making and breaking the primary circuit, and the aerial and ground connection. When the key is pressed the power supply passes through the primary of the induction coil or transformer, as the case may be. When the current is broken, or when the direction of the current is changed as in the case of alternating current which is used with a transformer, the secondary current flows out into the aerial and ground, which act as a con- denser, accumulating the charge. When the charge reaches a certain point it can no longer be contained in the aerial- ground condenser, and consequently it dis- charges across the spark gap, setting up oscillations in the aerial circuit. Simple as such a system may be, it is hardly permissible in general practice for the Tunlna le good reason that the Inductance S waves emitted are of )^ such broad wave length that they j^ cannot be readily tuned out at the g receiving end. Any amateur of long experience can tell you stories How inductance is added to vary the wave lengrth of the aerial. In this in- stance the same apparatus as shown on page 209 is employed, but a tuning inductance, known as an aerial induc- tance or loading coil, is added. of the days before the present radio laws, when it was possible with even a one-inch coil and other simple ap- RADIO FOR EVERYBODY 211 paratus to prevent the most powerful stations from carry- ing on their business, if the amateur transmitter happened to be located a short distance away. The one-inch coil simply monopolized the ether in its immediate vicinity. It came in loudly at almost any point on the tuner, so that it could not be tuned out in order to receive a signal from a distant transmitter. However, it does not carry for any distance, so that outside of deliberate interference it was of no real value. Furthermore, one of the first things which the radio law accomplished was to put an end to these broadly tuned transmitters and in their place insisted on transmitters whose emitted waves must be sufficiently sharp so as to have them interfere as little as possible with other waves. The plain aerial arrangement, as this layout is called, has other advantages aside from its simplicity. Its effective- ness comes in when the sending operator wants all possible stations to hear him immediately, as for instance when a ship is sending out a distress call. At such a time inter- ference is a desirable thing, because the distress call must be heard by every possible receiving station within range. With the regular sharply tuned waves, a receiving oper- ator may never hear the signals for the reason that his receiver is adjusted for another wave length and is too sharply tuned to respond to a sharply tuned wave. The broadly tuned wave, on the other hand, can be heard with almost any receiving set adjustment. The plain aerial has also a definite advantage in military activities for the purpose of drowning out or "jamming" the enemy's sig- nals. For amateur purposes, however, the plain aerial arrangement is a thing of the past. A modification of the plain aerial arrangement is shown on the preceding page, which has a tuning inductance in the aerial circuit so that wave length of the emitted waves may be varied to some extent. Placing a condenser in the aerial or ground lead also varies the wave length, but instead of increasing it, as is the case with inductance, it decreases the wave length. 212 RADIO FOR EVERYBODY The Transmitting Aerial In transmitting the aerial problem is far more involved than it is for receiving. As we have already learned, a single wire of almost any length or even a bed-spring Inverted Ir-type aerial, with the lead-in taken oflf at one end. or fire-escape or other mass of metal will do for an an- tenna in connection with a good receiving set, but the aerial of a transmitting set must be properly constructed if satisfactory results are to be obtained. To begin with, a single-wire aerial is unsatisfactory for transmission purposes. Two or more wires must be used, and four wires or more give the best results. Then T-type aerial, with the lead-in taken oflF the middle of the aerial span. the height is important; the aerial should never be less than 25 feet above the ground or roof, and preferably 50 feet or more. In the accompanying diagrams several types of trans- mitting aerials are shown. The most common is the in- verted L-type, with the lead-in at one end. The T-type should be used when the span is greater than 100 feet RADIO FOR EVERYBODY 213 in order to reduce the natural wave length of the aerial. The umbrella aerial should be used when one is working in a crowded space and there is no room for the usual types of aerials. The umbrella aerial makes use of a single tall mast, with wires radiating downwards in all directions. The lower ends of the wires should be at least 20 feet away from the base of the mast. The construction of the transmitting aerial is consider- ably more involved than that of the receiving antenna. It must be larger and therefore stronger, and it must be better insulated because it is handling high-voltage cur- rents. The drawing on page 215 gives a few pointers The V-type aerial — a rare type which should only be em- ployed when a suflScient span cannot be obtained, thus mak- ing a double aerial of this kind desirable. concerning the construction of a good, substantial multi- wire aerial for transmitting purposes. Note that the ends of each wire are insulated with hard rubber rods pro- vided with screw-eyes at each end, or with regular elec- trose insulators. As a further precaution, insulators may be inserted in the ropes or wires supporting the spreaders, as the sticks supporting the wires are called. Pulleys 214 RADIO FOR EVERYBODY are provided on the supports of the aerial, so that the lat- ter may be raised or lowered at will for inspection and repairs. Guy ropes or wires are arranged with insulators for the purpose of keeping the aerial perfectly flat, despite wind and the unequal sag of the wires. The lead-in wires are taken off each wire of the aerial, brought down a con- siderable distance to a point where they converge into one lead-in cable, just before entering the station. The special electrose lead-in insulator shown makes a very neat lead-in arrangement. It will be noted that this insulator is provided with a brass rod passing through it, both ends of the rod being equipped with nuts and lugs for making connections. The strop or egg insulator is a popular form of insula- tor for the reason that it possesses great strength and good insulating properties. Furthermore, in the event of mechanical failure, it will be noted that the two wires or ropes passing through different holes in this insulator merely come together, so that the mechanical arrange- ment still holds fast even if the insulation arrangement may be broken down. The same aerial may be used for receiving and trans- mitting. In former days the same aerial was always used for both purposes. The aerial, in such a case, is designed with the transmitting end in view, since any good trans- mitting aerial gives good results with a receiving set. In order that the same aerial may be used for both purposes, a send-receive or aerial change-over switch is employed. This switch is connected with the aerial and with the re- ceiving and the transmitting sets in such a manner that when it is thrown one way, the aerial is connected with the receiving set, and is used for receiving, and when it is thrown the other way, it is connected with the transmit- ting set and is ready for transmitting. Obviously, it would not do to have the receiving set connected with the aerial at the same time as the transmitter, since the latter, with its powerful output, would cause damage to the delicate receiving apparatus. RADIO FOR EVERYBODY !15 Many amateurs today prefer to use a separate aerial and antenna for transmitting and receiving. The aerial and antenna are connected with a single switching device in such a manner that only one of them can be used at a Maif MA*t •Ssz 6Tro^ OP «^ insylAtor L!ectrod«. InsoUTo** for CArryifN^ LeAd-i'r\ Wire5 Constructional details of a good flat-top transnaitting aerial, the strop or egg type insulator, and the electrose lead-in in- sulator. time, so as to preclude operating the transmitter while the receiving set is connected with its antenna but a short distance away. In transmitting work a good ground is necessary, for the best results. A ground that is imperfect or of high resistance will take away from the transmitting range in no little degree. 216 RADIO FOR EVERYBODY Transmitters That Are Sharply Tuned Single-circuit transmitters are not permitted under the present radio laws, for the reason that ^ . the waves emitted are not sufficiently I ' ' ^ sharp. Too much cannot be said in favor of the radio laws -in this direction; any IT 5G Tunincj^ Inductance o or Helix Simple transmitter arrangement for producing fairly sharp waves of the damped variety. PS — power source; K — telegraph key; T — transformer; C — condenser; SG — spark gap; A and G — aerial and ground; and the tuning inductance or helix. one who has been listening in to the radio-phone service must have experienced the annoyance of some spark sta- tion breaking in on the mus'ic. It is only by assigning certain wave length bands to the various classes of trans- mitters, and insisting that their waves be kept sharply tuned within narrow tolerances, that interference can be reduced to a minimum. In order to emit sharp waves which come within the stipulations of the radio laws, it is necessary to produce the oscillations in a closed circuit which is directly or inductively coupled to the aerial or ''open" circuit. Such an arrangement is shown in the diagram on page 217, where the induction coil or transformer serves to charge the condenser, which discharges across the spark gap and through the inductance. The inductance^ it will be noted, forms part of the "closed" or oscillating circuit and also part of the aerial or "open'" circuit. Thus it serves as an auto-transformer, as a single coil transformer is called. Any number of turns of this inductance which is made RADIO FOR EVERYBODY 217 up of a number of turns of heavy wire or strip, may be cut into the closed circuit and into the open circuit, so as to estabhsh the proper ratio between the circuits. The positions of the spark gap and the condenser are sometimes interchanged, bringing the spark gap across the trans- former. There is practically no difference in the oper- ation, as a result of such a change. In connecting up the various components of a trans- mitting set, heavy wire, certainly not less than No. 12, insulated or bare, should be used. It is preferable to use copper strip, if possible, since it has a greater surface area and the currents with w.hich we are now dealing travel on the suface rather than through the entire con- ductor. The conductors should be neatly run from one connection to the next, and arranged so as not to come near one another because of the danger of sparking. Fur- thermore, the conductors must be kept as short as possible, for in a transmitting set the induc- tance represented by a few feet of conductor is sufficient to make the wave * .... • length of the oscillating cir- Addjf.onal .^ , . t. 11 InciucTancc tor cuit SO great as to be well ^ Y/aves beyond the permissible 200- -* meter wave lensth of ama- SG Short wove Condenser Same arrangement as shown on the fac- ing page, but with an aerial inductanoe or loading coil for increasing the w^ave length, and a ground series condenser for reducing the wave length, of the aerial- ground circuit. 218 RADIO FOR EVERYBODY teur transmission. So the components must be placed close together, and connected with the shortest possible conductors. This also applies to the connection with the aerial, which should be made as short and as direct as possible, in order to secure high efficiency and keep within the wave length requirements. In order to determine the proper number of turns for the closed and the open circuits, the usual method for the amateur is to use a measuring device known as a hot-wire ammeter in the aerial circuit, for the purpose of measuring the aerial current. Approximate results may be obtained by the use of a low resistance lamp, such as a small auto- mobile lamp or even a pocket flashlamp -bulb. The lamp is used in place of the hot-wire ammeter, the maximum current in the aerial being indicated by the maxi- mum brightness of the lamp filament. If the current is apt to be too great for the lamp, it Transm ittinoj Coupler Simple spark transmitter for producing: I Q sharply tuned waves of the damped variety. | In this case a transmitting coupler or loose- • coupler arrangement is employed, so that the -rz- oscillating or closed circuit is entirely separ- ated from the open or aerial-ground circuit. The primary P and the secondary S comprise the transmitting coupler. should be shunted by a few turns of wire. The ammeter and lamp must be eliminated or even short-circuited ex- cept when actually needed, in order to keep the resistance of the aerial circuit down as low as possible. In actual practice, the closed circuit is first adjusted to the desired wave length, which can best be determined by RADIO FOR EVERYBODY 219 the use of an instrument known as a wave meter. Then the aerial circuit is adjusted until the lamp or hot-wire ammeter indicates the maximum output, proving that the two circuits are in resonance. Most of the progressive radio clubs — and there are radio clubs in practically every part of the country — ^^have wave meters for the use of their members. The best method of tuning, aside from waiting for the radio inspector to tune the transmitter when he comes to inspect it, is to call upon the local radio club for aid in this direction. One method largely employed by amateurs in tuning their transmitters is to adjust their oscillating circuit and then the aerial circuit for maximum output, after which they ask a radio friend to listen in on his receiving set to the test signals and to determine whether they are higher or lower in wave length than those of other amateur sta- tions known to be tuned to a wave length below 200 meters, which is the maximum set for amateur transmis- sion. This latter method, however, is not very accurate. In most instances it is best to wait until the radio inspec- tor comes to the station in order to check up the trans- mitted wave lensrth. The inspector, being provided with a wave meter, sees to it that the station is emitting a wave within the set limits and also that the wave is sufficiently pure or sharp to comply with the law. At this point it is well parenthetically to point out that the transmitter problem may be materially simplified by purchasing a complete transmitter in one unit. Today the practice is to make the transmitter apparatus into one simple unit in the form of a panel, the controls and meters being placed on the front face, and the various components at the rear. Such a transmitter has wave length adjustments and hot-wire ammeter, as well as other controls which simplify the tuning and general operation. If a complete transmitter is not employed, then it is necessary to purchase separate pieces of apparatus and to arrange them in some suitable manner. Any radio supply house will gladly furnish the necessary technical assistance 220 RADIO FOR EVERYBODY in the installation of a radio transmitter. Then again, if one has cultivated the friendship of the radio amateurs in the general vicinity, one can obtain all the necessary help in this direction. So much for the directly-coupled set which we have so far discussed, and the tuning of a transmitter. There is another arrangement known as the loose-coupled set, which is shown in the diagram on page 219. Here the closed and the open circuits are not connected directly, but are inductively coupled. Such an arrangement makes for sharper waves and a high degree of efficiency. The coupling may be varied so as to obtain the best results, the adjustment depending largely on the type of gap employed. The Question of Transmitting Condensers The most common types of condensers used in radio transmitting circuits employ mica or glass as the dielectric, with tinfoil or thin copper as the conducting coatings. Compressed air and oil condensers are sometimes used in professional work, but they are balky and certainly well outside of the province of the amateur. For very high voltages the condenser plates are sometimes immersed in oil to prevent brush discharge. Brush discharge is the leakage of current which takes the form of tiny purple streamers or sparks about the edge or any conductor of high voltage current. For moderate voltage a coating of paraffin over glass plates, especially at the edges of the metal foil, will satisfactorily reduce brush discharge. Today, however, the amateur is indeed fortunate in that his condenser problem is solved by purchasing one or the other of the several manufactured condensers which come in compact molded units, or in wooden or metal cases. A condenser of suitable size can be obtained in one unit or built up of several units. The transmitting condensers mostly used today are of the mica insulated type. These condensers have been found to be superior to any other type. Each mica con- denser is composed of several sections or units enclosed INOiCATING 'IMSTRUMCNTa *! MOTOR- GENERATOR '•COrsTROLS I COUPUNQ, ^<"CONTROl_ we: length CNTROL.S auENCHED GAP >WER CONTROL "iNEL. Panel type damped wave transmitter, such as is employed on board steamers. This transmitter makes use of a quenched grap, which is mounted on the front of the panel. (See page 223. > ^^22 RADIO FOR EVERYBODY in a common casing of aluminum or wood, depending upon the capacity and voltage. Each of these sections or units comprises alternating sheets of mica and foil, over a thousand in number. The sections or units thus con- stituted are piled on top of one another in the aluminum casing, and each section or unit is separated from the next by a sheet of mica. The sheets of mica are larger than the sheets of foil, so as to avoid any brush discharge at the edges. Air, moisture, and small vacuum pockets must be elimi- nated from each section or unit, hence an insulating ad- hesive of special composition, having the required dielec- tric properties, is forced through the entire condenser. The moisture and air are expelled, and the vacuum pockets are filled with this adhesive, which is deposited in a thin layer on each of the thousand sheets of mica. Next a melted wax compound is poured into the aluminum casing, so as to fill any empty spaces between the condenser sec- tions or units and the case. Before the wax has hardened a pressure plate is placed on the topmost section or unit. After the cover is screwed on, this plate presses all the sections together. Because they are pressed together, the sections cannot move about. It is highly important that the spacing between the metal foil and the mica be kept constant — an end secured by the use of the pressure plate. A post passes up through the cover of the case and serves as one terminal, the case serving as the other when metal is used for the case. The efficient use of the space inside the condenser — the active surfaces taking up the larger part of this volume — is, of course, a big factor in making the mica condenser a fractional part of the size of the glass plate or Leyden jar condensers of equal capacity. The Leyden jar con- densers are the bottle-like contraptions with an inside and outside tinfoil coating, seen in physics laboratories and in connection with X-ray and electro-therapeutic apparatus. Yet the mica condenser has 2,000 square inches of active surface as compared with 175 square inches for a glass dielectric condenser of equivalent capacity and voltage. RADIO FOR EVERYBODY 223 Since the mica condenser consists of over a thousand sheets of mica and foil, the full voltage across the trans- former is minutely subdivided. Hence the potential that does act across a single unit is so very small that there is lK si y AERi'^^i. iNDUCTANCE infa fS3i :|i»; .. SiSill wi ^i ^H li ^B WAV E - u £ N ;. r k Sa|^9P# CHAN61N0 1 H^K^^F M SVytTCHELS 1 gB|HB 1 K1 icA -""^^n^^BiliH ; CONDENSERS ^m^^^^^^^M ,^^^4^ 1 ,:;V|f" 1 ■TRANSFORMER- ^CASING Panel type damped wave transmitter, the front view of which appears on page 221. Simple as the front view may seem, it will be noted that the transmitter is quite complicated with most of its mechanism mounted at the rear of the panel. 224 RADIO FOR EVERYBODY no destructive brush. The losses m the dielectric increases greatly with the voltage. Therefore, if the voltage of each section in the condenser is reduced markedly, the problem of preventing the brush discharge is met. It is better to control several hundred volts in this manner than twenty-thousand volts individually. When the spark gap of a transmitter is broken down by the high voltage it becomes a conductor, and readily allows the oscillations of the condenser discharge to pass. Dur- ing the interval between discharges the gap cools off and quickly becomes non-conducting again. If the gap did not resume its non-conducting condition, the condenser would not be charged again, since it would be short- circuited by the gap, and further oscillations could not be produced. The restoration of the non-conducting state is called ''quenching." A device called the quench gap is described further on. Spark Gaps of All Kinds A plain spark gap usually consists of two metal rods so arranged that their distance apart is closely adjustable. The gap must be kept cool, so that the discharge will not arc and to this end the rods are often provided with cooling fins. The length of the gap which can be employed is limited by the voltage that the transformer is capable of producing, the ability of the condenser dielectric to with- stand the voltage, and the -fact that for readable signals the spark discharge must be regular. If the gap is too long, sparks will not pass, or only at irregular intervals. If the gap is too short, it may arc and burn the electrodes. Even if no arc takes place, the voltage is reduced by too short a gap and this results in reduced power and range. The length for smooth operation can usually be determined by trial. It is found that a short gap between cool electrodes is quenched very quickly, the air becoming non-conducting almost immediately after it has broken down, or as soon as the current falls to a low value. This action is also improved if the spark gap is enclosed in an air-tight cham- POWER SUPPLY AND AERIAL AMMETERS AERIAL INDUCT- ANCE CONTROL WAVE LENGTH CONTROL. SPEED AND VOLT AGe CONTROL COUPLING CONTROL QUENCHED SPARK-GAP ENCLOSED 3VNCHROMOt*-S RO-r/VRY GAP- OrM GENERATOR SHAFT MOTOR GENERATOR CONXRO PANEL Another type of damped wave transmitter, such as is nsed on board ship. In this instance there are two methods of obtaining: the oscillations or waves. There is the quenched pap mounted on the front of the panel, and the synchronous rotary gap mounted at the right. 226 RADIO FOR EVERYBODY ber. The standard form of quenched gap, as such a gap is called, consists of a number of flat copper or silver disks of large area, say three or four inches in diam- eter at the sparking surfaces, with their faces separated by a space about the thickness of a piece of heavy paper. To provide the necessary total length of gap for high voltage charging, a number of these small gaps are put in series, so that" the spark must jump them all, one after the other. The disks are separated by rings of mica or paper. The larger gaps handling considerable power are kept cool by means of a small fan or blower. But all quenched gaps are provided with projecting fins for radiating heat, and in some designs air spaces are provided between the pairs of disks which form the successive gaps. The number of gaps is determined by the voltage, allowing about 1,200 volts per gap. Eight or ten gaps are sufficient in most transmitters of this type. The quenched gap is not used in sets having a supply frequency as low as 60 cycles per second. The sparks obtained at that frequency are found to be irregular and not of a good tone. For this case, a rotary gap is used, as will be explained. For 500-cycle supply the quenched gap is adjusted to break down at the maximum value of the applied voltage; that is, with its total length so ad- justed as to give one spark for each half cycle of the applied current. Discharges at other times are not pos- sible, and as a result of this regularity a clear note is obtained. One advantage of the quenched gap is that it aids the production of a so-called pure wave — one which is sharply tuned. It has also the advantage of being noise- less in operation, on account of the very short gaps and the enclosure of the spark. A 500-cycle current supply may be obtained by using what is known as a motor-generator — a motor operating oflf the usual supply current, directly connected with a 500-cycle alternating current generator which supplies current for the radio transmitter. Such motor-generator sets may be obtained in a wide range of capacities for the smallest as well as the largest transmitters. RADIO FOR EVERYBODY 227 A rotary gap consists of a wheel with projecting points or knobs, with a stationary electrode on each side of the wheel. The spark jumps from one stationary electrode to one of the moving points, flows across the wheel, and then, after leaping the corresponding gap on the other side, passes out at the second stationary electrode. The number of sparks per second is thus determined by the speed of the wheel which is motor-driven, so that signals of high pitch can be produced. An advantage of the rotary gap is the prevention of arcing, because of the motion of the wheel and the fanning effect, and because the electrodes brought successively up to the spark gap have time to cool in their idle intervals. There is still a more elaborate form of spark gap which is seldom found in amateur work but which mi'ght as well be mentioned here, since we have covered practically all forms of transmitters of the damped wave category. This more elaborate form is known as the synchronous rotary gap. The wheel of the rotary gap is mounted on the shaft of the motor-generator set which furnishes the alternating current. The mounting is such that the spark points or electrodes are brought opposite each other at just the mo- ment w^hen the alternating current voltage in the condenser reaches its maximum value, positive and negative. Thus 500 cycles will produce 1,000 sparks per second. This regular occurrence of the discharges gives smooth and efficient operation, as well as a pure musical tone. A rotary gap that is not so timed with the alternating cur- rent supply is called non-synchronous. Attempts to produce a high pitch spark with a 60-cycle source by means of a synchronous gap giving, say, exactly six sparks per half cycle have not given satisfaction, be- cause the applied voltage is not the same at the time of the different sparks, and while the note is of high pitch, it is not musical. It has been found better to use a non- synchronous gap in such case, producing a large number of sparks per second and letting them occur wherever they may happen during the cycle. The irregularities will 228 RADIO FOR EVERYBODY somewhat balance up. While the tone is not strictly musi- cal, it can be made of high pitch. The non-synchronous gap is best used if nothing but a 60-cycle or other low frequency source is available. Such a low frequency, however, is being avoided in modern apparatus, the stan- dard frequency being 500 cycles per second. But for the amateur who cannot go to the expense and trouble of a small motor-generator set for generating a 500-cycle cur- rent, the rotary gap will be found quite satisfactory on 60-cycle supply. Chapter VIII. THE RADIO TELEPHONE TRANSMIT- TER AND THE CW TELEGRAPH TRANSMITTER THE transmitters described in the previous chapter are of the damped or discontinuous variety. They are suitable for radio telegraph purposes, although the con- tinuous or undamped wave type has proved to be so much better than the former that more and more radio amateurs have turned to this latter method. The continuous wave transmitter carries farther with a given amount of power ; the equipment is in many respects simpler; it is silent in operation; it can be interchangeably used for radio tele- graph or radio telephone. We have already learned that damped weaves are sent out in trains or groups, and that the oscillations in each train or group die down or are damped rapidly. The un- damped or continuous waves, known as CW for short, are not damped, nor do they die down. The waves are continuous just so long as the transmitter is operated. The only change in the amplitude or potential of the waves is when they are modified by means of a telegraph key to form the dots and dashes of the telegraph code, by means of a buzzer to give what is known as modulated C. W., or by the voice modulations for radio telephony. The Vacuum Tube in a Transmitting Role Thanks to the recent development of the vacuum tube as a generator of high frequency oscillations, it now 230 RADIO FOR EVERYBODY becomes possible to produce continuous oscillations or CW on a small as well as large scale. This fact has resulted in the production of compact, continuous wave transmit- ters which may be used for radio telephony or radio telegraphy by the amateur. In fact, at this writing the CW transmitters now being offered are no more compli- cated in their operation than the receiving sets ; in truth, at a glance one could not tell a small CW transmitter apart from a vacuum tube receiving set. Let us consider a typical radio telephone and telegraph transmitter now on the market. All the controls and apparatus necessary to operate this transmitter are mounted on two panels, each measuring 9 inches by 4^ inches. The left panel contains the grid, plate, and the antenna inductances and their control switches ; a compact induc- tance unit serving as a choke coil ; a send-receive transfer switch; and variable antenna condenser. The right-hand panel contains tube receptacles, standard modulation trans- former, filament rheostat, radiation ammeter, grid leak, grid stopping condenser, and filament insulating condenser. These various terms will become clearer as we read more about the elements of a CW transmitter. Using a 100-volt "B" battery on the plates, this set radiates .1 to .2 ampere and the range is 10 to 15 miles. With 350 volts impressed on the plates .3 to .4 ampere will be radiated, giving a range of 25 to 30 miles. With 500 volts plate voltage, the aerial ammeter reading will be .5 to .6 ampere, or sufficient to cover 35 to 50 miles. By the addition of a buzzer and key, modulated con- tinuous wave transmission is possible and the above ranges, which are for the radio-phone, are doubled. Adding a key only, provides continuous wave communication, trip- ling the ranges. However, with the key only, the waves are absolutely continuous, or what is known as straight C W, and do not serve quite as well for amateur purposes as the interrupted or modulated CW, which may be de- tected with any type of receiving set within range. The straight .continuous wave can only be detected with a « 3 5-* ►"« s o X a ►s S". c p is ^;2 e.3 3" &»' o* ■O-d OB t O P 1 SO 3 -» ^ 3D • 1 i.i§ -:S3 tt ' i ^ o < z § o 0) n > i Ik c ^HHh hb ^ >• o » V 2 ' i ~fl ■ u£' c \ >^ "JflH Eb lii« i ? ^ W H ^ c 05 3} , ^s^Cn ^9 kS ^,^ "~~~~~^->w ,illiaj| ||i|L rS^S^ ,1 ■ IbB pll /^ J ■ s ^H^gi. Jh H, 1^^ i I ffl^srf ■B^^^t ll sgB ^? y -- ..._--„ J 1 HK r^^^w H l^^gM' ,aB ■H ^R^' ■ I^H ^ ^ JHB ^M 1 p "^ 3! 1| Q P" jMBfj BB^^^^^ri |^fc'~ ~ 5 ^^^H |i|i|il|yi|[' (ft wk K f ~- ^^^^K ■ \i 1 1^ ^u -1 ^--^ V ■^^K$ 'W H ff^ ^M^B^^^M i-'- \ ' > r r, -W^* fBmi'::' 4 %4 P ^tt I'^^^^p 1 - a; > T K 1 1 1 % ipx,^ i X '^, ,*f->^ M-j—y^ ^ ft ■ ^B B ^ -_i O JB 1 B \ n n ■0 ^V^^^HE IE 9H|H pl !^ 2; i ,.^,_' ^^^B ^S^^SB^s wH| IB§pB|^^p H 'j ^BH^^^ffia^^^H 1^. J i^^^^EB 1 — z ; - SBH^S^hI ■n ^HMpfm ^ ? B^B^^kB^^S ttH |^HH|^^^ ^' - 1 E^^^^HB^HHHj I^BI ■nf^K[^Wft^ Z ; ■ 1 n 2 -i : ' ^^^^^^^^^^^^H ^^H wB/B^^m. <£ ^^^^^H H W^^m «^ ^m 1 n ^-^^p^BB B HH 1 232 RADIO FOR EVERYBODY receiving set intended for and adjusted for continuous wave reception, as explained in previous chapters dealing v^ith receiving sets. A six-volt storage battery lights the filaments and pro- vides current for the microphone, while the plate current can be o'btained from a rectifier unit and transformer operating on alternating current supply, or any motor- generator set. Any manufacturer of radio-phone trans- mitters will explain just what equipment and accessories are required for this kind of work. It is too involved to be treated in this popular work. Then there are the larger types of radio-phone trans- mitters. A relatively simple cabinet set, with a panel measuring 13 inches by 11^ inches, and 8 inches deep, may be relied upon for uninterrupted, dependable trans- mission over distances up to 60 miles. Variable controls have been reduced to a minimum and operation could not be further simplified in many of the ofiferings of this class. On the face of the panel are the plate current milli-am- pere radiation meter, two filament rheostat knobs, the send-receive switch, a switch for changing from speech to modulated CW or straight CW, antenna condenser switch and motor control switch. On the rear of the panel are filter condenser, constant current coil, high frequency choke coils, grid condenser, plate condenser, filament in- sulating condenser, antenna condenser, grid leak, four tube receptacles, modulation transformer, antenna inductance, and microphone resistance. To supply the plates with a potential of 350 to 500 volts, a 32 or 110-volt dynamotor (a single motor and generator tmit) or a 32 or 110-volt motor-generator (a motor and a generator connected together) is required, while for the filaments and microphone a 10-volt storage battery is necessary. The 32-volt potential is mentioned because certain rural districts make use of this low voltage in their isolated plants that siipply lighting current. So much for the complete sets of low and moderate power. When it comes to more ambitious ranges, running into the hundreds of miles, a much larger transmitter RADIO FOR EVERYBODY 233 must be considered. Following the panel idea, there are one-half, one-kilowatt, two-kilowatt, and larger CW telegraph and telephone transmitters. The various con- trols and meters are mounted on the panel, while the various components are mounted at the rear, both on the reverse side of the panel and on iron brackets and shelves. Why CW is Popular In time it is believed that virtually all radio amateur stations and, for that matter, commercial stations, will be using CW or undamped wave transmitters for these reasons : Typical radio-phone transmitter, which is provided with rectifying tubes so that it can be operated on. an alternating: current lighting: circuit. (1) Radio telephony is made possible on a small or large scale. (2) Extremely sharp tuning is obtained and consequent reduction of interference between stations working close together. A slight change of adjustment 234 RADIO FOR EVERYBODY Typical CW transmitting equipment, showing: its simplicity. The coil at the left is a grid coil, while the instrument at the right is a transmitting helix, made up of a number of turns of flat copper strip. The clips are for the purpose of making the necessary connections at any points , on the helix in order to obtain the proper wave length values. throws a receiver out of tune, and the operator may pass over the correct tuning point by too rapid a movement of the adjusting knobs, so sharp is the continuous v^ave transmitter. (3) Since the oscillations go on continuously instead of only a small fraction of the time, as in the case of damped waves, their amplitudes need not be so great and hence the voltage applied to the transmitting condenser and aerial are much lower. This means that the problem of installation is reduced to a minimum and the installation of such a set is made relatively simple. (4) With damped waves the pitch or tone of received signals depends wholly upon the number of sparks per second at the transmitter. With undamped or continuous -waves the receiving operator controls the tone of the re- ceived signals, and this can be varied and made as high or as low as possible in pitch to distinguish the signals from RADIO FOR EVERYBODY 235 atmospheric disturbances and to suit the pitch to the operator's ears and to the sensitiveness of the telephone receivers. These advantages, freedom from interference caused by other stations, the use of high tones and low vokages, and the greater freedom from strays combine to permit a higher speed of telegraphy than could otherwise be obtained. How CW Transmitters Work Persistent, continuous or undamped waves, whichever you wish to call them, can be generated by several distinct methods, each having its advantages and disadvantages, as follows : (1) The arc or Poulsen method, so named after its Danish inventor. Oscillations of radio frequency are A 50-watt transmitting tube, showing^ its principal elements. Like the amplifier and detector tubes, it comprises a filament, grid, and plate. 336 RADIO FOR EVERYBODY obtained by means of an electric arc burning in an atmos- phere of hydrogen and in a strong magnetic field. The arc method produces undamped waves of rather long wave length, and is ordinarily operated on 500 volts direct cur- rent. It has been discovered that an electric arc between proper electrodes, shunted by an inductance and a con- denser, will produce continuous oscillations through the shunt circuit, and such a circuit is used to excite an aerial circuit for transmitting purposes. Depending on whether a telephone microphone or key is employed, the arc gen- erator may be arranged for radio telephony or telegraphy. Needless to say, the arc is unsuitable in many ways for amateur radio purposes, because it is too elaborate to begin with, the oscillations are of too great a wave length, and the arc cannot be constructed for small powers yet produce efficient results. (2) The high frequency alternator method, which is practically an alternating current generator of special de- sign having a great number of poles revolving at a high speed, in order to obtain the necessary high frequency. A standard General Electric Company two-kilowatt high frequency alternator designed for a frequency of 200,000 cycles or 1,500 meters wave length must be revolved at a speed of 20,000 revolutions per minute. This is a very high rate of speed. Imagine a speed seven or more times as fast as the turning of the average electric fan ! Again, needless to say, this is not a good method for the average amateur. Skipping over several other highly technical methods, we come to the vacuum tube oscillator method, which is brought about by using what is known as the Armstrong "feed back" or regenerative system, which has already made our acquaintance in the previous chapters dealing with receiving systems and methods. This kind of €W transmission is brought about by placing an inductance in series with the plate, and this, in turn, is placed in inductive relation with the grid, causing the plate current to act on the grid and producing oscillations of a frequency ^38 RADIO FOR EVERYBODY dependent entirely on the constants or electrical values of the circuit. Perhaps the accompanying diagram makes the foregoing description clearer. It will be noted that the arrangement here shown is very mUch like the usual regen- erative receiving hook-up, except that the telephone re- ceivers have been left out, and a telegraph key is placed in the primary circuit of the oscillation transformer or -S-B rr vc, n G Simple CW telegraph transmitter which may be assembled by any one. A — aerial; G — grround; P and S>^primary and sec- ondary of the loose-coupler LC; VCl — variable condenser for reducing wave length of aerial-ground circuit if neces- sary; VC2 — variable condenser; OT — oscil- lating tube; A — filament battery; K — fila- ment rheostat; B — filament battery; F— feed-back or tickler eoil. transmitting loose-coupler in such a manner as to short- circuit several turns every time it is pressed down. This causes the wave length to fluctuate, and produced the dots and dashes in the sharply tuned continuous waves inter- cepted at the receiving end. The experimenter is practically limited to the vacuum tube for his experiments and work with undamped waves because of the cost and other deterrent features of other VACUUM TUBES INDUCTANCE UNIT WAVE t.ENGTH 'CHANGiNG GEAR POWER CONTROLS Mechanism* of a commercial CW telegrraph transmitter, using^ several 50-watt tubes and a chopper for producing modulated continuous waves. 240 RADIO FOR EVERYBODY systems. Even leaving aside the consideration of cost, in most instances the undamped wave generators other than the vacuum tube operate best on long wave lengths which are barred to the amateurs. However, the fact remains that the vacuum tube makes an excellent generator — one that is quite flexible, too, since its power can be increased merely by connecting more bulbs in parallel. Placing the key across a few turns of the oscillation transformer, so that the CW transmitter is tuned and r-T-T detuned with the V A ^ l|l|lH^^lKn 1. ^ 1 1 333= operation of the key, I I ^^ often done. It will Uoooo,,..^.^_J be recalled that the sharpness of u n - damped waves is quite __ marked at the receiv- J 5 ing end, so that it fol- J lows that when the set ~ is detuned, even to the extent of two turns of the secondary Simple method of produciiiF ^ ^ ^ ^ C OSCillatioU buzzer modulated CW waves, transformer the Note the buzzer Inductively ' connected with the grid cir- cuit. A — aerial; VCl — vari- able condenser in aerial- ground circuit; VC2 — vari- able condenser in oscillating circuit ; R — filament rheostat ; A. — filament battery ; B — plate battery. waves are not heard at that moment. In this manner it is pos- sible to make dots and dashes with an or- dinary* telegraph key even when handling considerable transmitting power, since little power is broken by the contacts. Another method of CW transmission is to use mod- ulated persistent waves by having a transformer in the grid circuit and a buzzer and key in the primary winding of same, as shown in the accompanying diagram. The note emitted is similar to the tone of the buzzer used, and such signals can be received on any type of receiving set as distinguished from the straight CW waves which RADIO FOR EVERYBODY 241 cannot be heard with the ordinary crystal detector working in a damped wave receiving circuit. What is known as a chopper is also used to break up the continuous waves in order to make them audible with any type of receiving set. The chopper is simply a motor- driven commutator or circuit breaking device, which breaks a circuit a given number of times according to the speed at which it is revolved. The chopper can be placed in series with the grid resistance and its rate oi rotation will then determine the note of the CW signals, and make them audible to any receiving set. The matter of the aerial is a very important consider- ation in CW transmission, for the reason that the waves are so sharply tuned that the slightest change in wave length affects the reception of the waves. Thus if the aerial should sway with the wind and change the distance between its wires and the ground, the wave length of the transmitted waves will also be varied, ever so slightly to be sure, but enough to give some trouble at the receiving end. For this reason special aerials are often used in C W transmission. Instead of using the flat-top aerial, with the wires side by side supported on spreaders at either end, the cage type of aerial is often employed. This aerial has hoops or rings at each end instead of the usual spreaders, and the wires are arranged on these hoops or rings so as to form a round or cage-like aerial which is supported in the usual manner. The cage type of aerial is more constant in its electrical characteristics and is therefore more satisfactory in CW work. Furthermore, to ensure still greater rigidness, the counterpoise form of ground is also employed to a large extent in CW trans- mission. The necessity for a rigid aerial system is, obviously, more essential when the dots and dashes or the telephone modulation is obtained through a change in wave length, than w^hen the dots and dashes and telephone modula- tion are caused by a change in amphtude or voltage. 24^ RADIO FOR EVERYBODY pHBi iiiiif ,- ww» 1 ■■Iiiiii ■^iil 1 mmBims- '•:=! 1 wiiiltililiSffliiWil^ ■«*■:- ■ ■ - 1: I ^■:fa*:-^e--^-iyv smmm 'imsmmmemm liiiiaMps ..i ^Bliiiiii^^ ■-, . CW telegraph and radio-phone transmitter of the panel type, with the various controls and meters mounted on the front face. Transmitters of this type are being used in several of the radio-phone broadcasting stations. The general subject of CW transmitters is such a large one that we cannot afford to go deeper into it at this time. Then again, it is very well covered by more advanced works, and certain radio companies have brought out ex- RADIO FOR EVERYBODY 243 ceptionally complete and explicit literature on CW trans- mission. Radio Telephony Reduced to its Simplest Form If one is satisfied with a range of but a few miles, a CW transmitter may be readily assembled, and it can be almost as easily used for radio-phone work as for radio telegraph. First of all, the radio amateur must obtain the proper vacuum tube. So far we have spoken of the vacuum tube detector and the vacuum tube ampUfier tubes, but now we come to the transmitting tubes. The standard trans- mitting tubes now available on the mar- ket come in 5-watt, 50- watt and 2 50- watt sizes. For our pres- ent purpose the 5- watt is the most pop- ular, since we are dealing with low power. Two 5-watt tubes in parallel will put from one and one-quarter to one and three-quarter am- peres in the amateur's aerial. Using one of these tubes as a mod- ulator and the other as an oscillator, for experimental radio telephony, distances up to 40 miles can be covered, and at least four times that distance when the two tubes are connected in parallel for CW telegraphy. Four or five 5-watt tubes can be worked in parallel with increased range. The 5-watt tubes are also used as power B Hlllll-VSAW A ^ A simple continuous wave telegraph transmitter, making: use of a single 5-watt tube. This set transmits straight CW. A — aerial; I — aerial in- ductance; B — high voltage battery; VCl — variable condenser; G — ground; K — telegraph key; VC2 — grid conden- ser; OT — oscillating tube; A — filament battery ; K — filament rheostat. 244 RADIO FOR EVERYBODY amplifiers in radio receiving circuits. The energy ampli- fication obtained therefrom is particularly useful for the operation of loud-speakers. The 50-watt transmitting tube is intended for \ / long-distance telephony and telegraphy. Two ^A 50-watt tubes connected in a self-rectifying or in a straight direct-cur- rent plate excitation cir- cuit will give aerial cur- rents of three to four am- peres at amateur wave lengths. A single tube operated from a direct- current source or a recti- fied alternating cur- rent source will put two and a half to three amperes in the amateur's aerial. Hundreds of these tubes are already in Simple combination • , . radio telegraph and usc m amatcur trans- radio-phone trans- mittingf S t a t i O n S mitter. A — aerial; ^ S , I— aerial inductance ; thrOUghoUt the COUU- ^n b B— higrh-voltage bat- ^ j Hic;tpnrp«; nn tery; VCl— variable ^^J' ^"*^ QlSianceS Up condenser; TR — telephone microphone; tO 1 900 mileS have VC2 — variable condenser; K — telegraph -, ' j •, key; OT— oscillating tube; A— filament been COVercd by USmg battery; K— filament rheostat. {^ ^n appropriate OS- cillating circuit. The 250-watt tube is the most powerful tube of the series now on the market for experimental and general transmission purposes. This tube is equipped with a spe- cial filament which gives exceptionally long operating life. Let us return to the 5-watt tube and to the simple trans- mitter, which is more in the province of this book than the more powerful, more elaborate transmitters. A simple radio-phone transmitter may be readily built or rather assembled by the radio enthusiast, who wishes to do a TR NX rr RADIO FOR EVERYBODY 245 little talking on his mvn account and is willing and ready to secure his operator's and station licenses. The first step is to obtain a 5-watt transmitting tube. Then we need two 22^ -volt B battery of the same kind as we used for the receiving sets. On one battery a 5- watt tube, under good conditions, will transmit 5 to 10 miles. Then we need a variable condenser of 0.001 mfd. maximum capacity, which is connected in the ground cir- cuit, and another variable condenser with a maximum capacity of 0.0005 mfd. which is placed in the grid circuit. A suitable CW helix or inductance is also required. This last-named piece of apparatus may be purchased already made, or it can be constructed of heavy copper wire made into a coil with the turns separated ^4 to }4 inch apart. Clips are used to make connections with any desired part of the helix or inductance. A six-volt storage battery, vacuum tube socket, filament rheostat, and a \ I / telegraph key complete the outfit. A micro- \/a phone can be substituted for the key and the set converted into a short-distance telephone transmitter. If possible, a hot wire ammeter should also be included with the set. This instru- ment is placed in the ground lead and serves to 8:=: How two or three tubes may be arranged in parallel for obtaining greater power while still using the same simple arrange- G ment. In this case straight CW telegraph is obtained. 246 RADIO FOR EVERYBODY indicate when the transmitter is adjusted to maximum efficiency. Tuning the set is accompHshed in very much the same manner as with the damped wave transmitter. With the filament of the tuhe Hghted and the set oscillating properly, the series and the grid condensers are varied until a max- imum output is indicated by the ammeter. However, this method does not indicate just what the wave length may be, and one may be overstepping the 200-meter limit. It may be well to have nearby amateurs listen in and say whether the emitted wave appears to be below 200 meters, and also when the transmission is at its best. The output of the transmitter can be increased by using a higher voltage on -the plate. By means of additional B battery units, the voltage can be increased to 90 volts. It must be remembered in this connection that the energy for the waves is taken from that source. Just so long as the tube does not glow with a blue haze, the B battery voltage can be piled on, increasing the efficiency and the range. Another scheme is to use two or three tubes in parallel, with the grids connected together and also the plates. Only one B battery is required for all the tubes. Much could be said here regarding modulator tubes, which permit of modulating heavy transmitting currents by means of ordinary carbon microphones through the medium of vacuum tubes known as modulator tubes, and magnetic modulators. Then there are filter reactors, rec- tifiers, filters, microphone transformers, and other devices which enter into the more elaborate CW transmitters, but for further information along these lines we must look to more advanced works specializing in CW transmission. Chapter IX. THE UNUSUAL USES OF RADIO ON LAND AND SEA AND IN THE AIR RADIO has many uses aside from the broadcasting of entertainment and news and the Unking of widely separated points. In fact, it seems as though we have done httle more than scratch the surface of its vast pos- sibiHties, and that the inventive talent of today must lead us to still greater and more startling achievements in the application of radio. In the early days of radio, too much was expected of it. There was much promise of the transmission of power by radio in order that airships and automobiles and street cars and ocean liners might be operated by distant power plants without the agency of wires or cables. Yet we know today that the transmission of power by radio is still a remote possibility ; we know that, starting with one kilo- watt at the transmitting end, we obtain less than a thou- sandth of a watt, or one millionth of the original power expended at the receiving end. . The radio method of transmitting power is a most inefficient one, and only if we hit upon some entirely new principle of transmission and reception can we hope to make anything of the idea of radio transmission of power. However, whatever radio wonders may have been ex- pected in the early days have been more than realized, even though the present achievements may be along en- tirely different lines. 248 RADIO FOR EVERYBODY The Marvels of Radio Control One of the most promising fields of unusual radio, if we may call it such, is the one given the broad name of radio control. This means the controlling of machinery and other things at a distance through the use of radio. Thus small vehicles and boats controlled by radio have attracted no little attention wherever they have been shown. Mysterious as these things may be, there is really nothing very complicated about them. This does not mean to say that anyone can construct a successful radio- con- trolled car or boat with little trouble, because there is a good deal of experimental work to be performed before such a delicate assembly can be made to work properly; but the principles are public property and may be em- ployed by anyone of an inventive turn of mind. The principle of radio control rests on the transmission of certain signals or radio waves which affect a detector in the same manner as the usual receiving set. Instead of rectifying the intercepted wave energy "for a pair of tele- phone receivers or for a loud-talker, however, the detector in this case passes its output over to a delicate relay, which is a device that is actuated by a source of delicate current so as to open and close the circuit of a more powerful local current. The more powerful current can therefore be made to do whatever work is desired. So, if we press the key of a transmitter, tuned to the right wave length, the machinery to be controlled intercepts the signal and operates its relay, which in turn closes the local current circuit for the performing of any desired task. However, such a simple system gives only one com- mand, so to speak, and since a number of different tasks, must be commanded by means of the remote control, some other agency must be introduced of multiplying the num- ber of commands that can be issued. There are several ways in which a number of different things can be commanded or controlled by remote control.. The simplest method is to use a revolving contact drum,. \ ■■»- 1 L *. 1^ J^ 1^ 250 RADIO FOR EVERYBODY as it is termed, on which are arranged metal strips which can make various combinations of electrical connections and which come into action one by one as the drum is revolved. This drum is revolved continuously at a pre- determined speed, or step by step. In the latter case one combination of connections after another is brought into action by means of an electro-magnetically operated ratchet device, which functions through the closing of the relay contacts. Every time a signal is sent out by the transmitter, the relay of the receiving device closes the circuit, current is sent through the combination that hap- pens to be effective at that moment, and the drum is then given a one-step turn to the next combination as the signal stops. The next signal sent through repeats the same performance, but with the combination then effec- tive being used. Now the combinations can be arranged to do all kinds of different things. Supposing we are dealing with a model submarine, controlled by radio. The first combina- tion on the drum starts the motors ; the second steers the craft to the left; the third brings the rudder to the nor- mal position; the fourth steers to the right; the fifth causes the driving motors to drop to half speed ; the sixth deflects the diving rudders so that the craft submerges; the seventh brings the craft back to the surface again; the eighth stops the motors. But supposing we want the craft to steer to the right, when the combination then effective is the seventh, or the one that brings it back to the surface, what then? Simple enough. We simply send out one short snappy signal after another without appreciable pause between them, so that the craft does not have time to respond to any one of the controls, brought into play in rapid suc- cession until we reach the desired control, when we stop and the craft obeys. Generally, some indication is pro- vided so as to show just what combination happens to be operative at any given moment. Little colored lights can be used to indicate when the start of a cycle of com- binations is at hand, and the operator knows just how 252 RADIO FOR EVERYBODY many signals to send in order to reach the desired control. Another method is to use a steadily revolving drum aboard the vehicle or boat to be controlled. A watch, carefully synchronized so that its large hand will turn at the same speed as the revolving drum, is used by the operator. In this manner the operator, while watching his synchronized indicator, knows just the right moment to press the key in order to take advantage of any desired conditions for any desired commanci. The Radio Compass and What It Means Something has been said regarding the use of loops for receiving purposes. A loop consists of a wooden frame with a number of turns of wire. The loop is used in the same manner as would the secondary of a coupler in a receiving circuit, with a variable condenser or variometer to vary its wave length. No ground is employed. The loop receives signals loudest when it is pointing end on towards the transmitting station, and this fact has brought the radio compass into existence. The radio compass is nothing more than a loop receiv- ing set. Thus the loop, which is mounted in such a manner as to be readily swung about on its vertical axis, is orientated until signals are picked up and a line can then be drawn on a corresponding map to indicate the direction from which the signals are coming. However, the loop indicates only the general line along which the signals are being received, and there is no telling whether they come from one end of the loop or the other. How- ever, in most instances the operator knows whether it is in one direction or the other, and he only requires the directive line. The radio compass generally consists of two or more radio compass stations on shore, at the entrance to a harbor or some other point. A ship, wishing to know its exact bearings, calls up the radio compass stations, and these stations, by orientating their loops, secure two directive lines for the ship. Since the radio compass sta- tions are located a certain distance apart, forming the RADIO FOR EVERYBODY 253 base of an imaginary triangle, and since a pair of stations obtain an angle reading formed by the direction of the received signals and .$ ■^ f *> H /^o y> ^^^ r^ jr-y^r ' Si^ ^ V Scandma^ (L, f^ ' f^ ■^prrfL''P^- Central Europe ^/k I Unrted ^^£: ii--:s^=^^^^^Z-—-:^^^^^?t^ I ^\% PJ ^-^"^^Y^^^ ^W--. - ■ Central AmwSr2^T. and Antilles ^W^ -. y\Lo\\ ^SS^ ^/ BrazzavillA V) C)" yC south Af}^ ^v /. 'i /=... ■ • The French communication scheme. The French stations are evidently intended to divide their time between a number of terminal stations and the spans are extremely long. How- ever, work is progressing on several large stations for this world-wide scheme. 264 RADIO FOR EVERYBODY nearly as many more channels of communication to the system as those already shown. In the second place, the plan shown is preeminently a commercial one, both in the placing of the terminal stations and in the practically exclusive use of each American station for a single channel. This latter feature permits the speedy handling of large volumes of traffic and avoids the troul)lesome delays which result when the time of a transmitting sta- tion is excessively "chopped up" or divided between too many receiving stations. The system is one of moderate and long spans, this being dictated to some extent by the Our American scheme for world-wide radio communication. Every station sliown in this map is either in operation or under construction, and by far the greater portion of the stations are those already in operation. geographical location of the United States, its particular communication, needs, and the absence of American po- sessions at certain points. The needs of the United States, considering these circumstances, have very greatly stim.u- lated to the technical improvement of radio communication, and have led to the satisfactory solutions of the problems of long-distance communication. The case is an inter- esting illustration of the stimulating and helpful influence of natural obstacles. It has long been known that traffic from one country to another is by no means evenly distributed throughout 266 RADIO FOR EVERYBODY the twenty-four hours of the day, the days of the week, or the months of the year. There are very pronounced peaks, and depressions or lull of traffic found to exist. Thus, the traffic between two countries will generally be heaviest for the hours during which daylight is common to both, and will drop to a minimum during the week end. It would be desirable to handle the peak of the load without permitting traffic to pile up, but this may not always be feasible for reasons of economy, both of equipment and of necessary personnel. This has led to the attempt to secure a high load factor for communication circuits by encouraging some of the users of the service to accept a certain delay in the delivery of their messages which are then sent at a reduced rate. Thus we find in addition to normal messages, which are sent irt the order in which they are received, the "deferred" messages which are sent at the earliest opportunity when traffic has slackened sufficiently to permit their introduction. "Night letters" and ''week end letters'* are sent during the periods in- dicated, and are obviously intended to fill an otherwise dull period in the circuit. On some circuits, "urgent" mes- sages are accepted which take priority over all others, and require the payment of a considerably increased rate. As a general rule, the minimum number of classes of mes- sages required to maintain an acceptable load factor is desirable not only because of the increased routine in handling traffic of many different classes but also because of the confusion in the public mind and the possible dis- satisfaction which results when the type of service rendered in any given case is not clearly understood in advance. The huge radio stations for inter-continental work are interesting studies. One of these stations is the Radio Central, located at Rocky Point, Long Island, some 70 miles east of New York City. However, the actual opera- tion of this station takes place from New York City, the dots and dashes being formed by an operator in New York City and sent over telegraph lines to the Radio Central station, where they are automatically transferred 2'68 RADIO FOR EVERYBODY to the powerful radio transmitter, consisting of a num- ber of 200-kilowatt high-frequency generators. Radio Central is in realty several stations in one. It comprises a number of separate transmitters so as to ensure simul- taneous communication with a number of stations abroad. Operating a Trans-Atlantic Station at a Distance It has always been a problem to control several hun- dred kilowatts of power at frequencies of 20,000 cycles per second by breaking it up into the dots and dashes of the telegraph code at speeds as high as 100 words per minute or more. When it is considered that this is equivalent to starting and stopping the flow of power fifty times per second, accurately and faultlessly, and that the initial control power is merely the few watts that can be drawn from the terminals of a telegraph line, the magnitude of the problem becomes evident. By the development of high-speed power relays and the new "'magnetic amplifier," the problem has been very elegantly solved. The mag- netic amplifiers at the Rocky Point station enable the powerful transmitters to be operated at long distance, so to speak. These ferromagnetic devices accurately modu- late or control the flow of power from the alternators to the radiating system or aerial wires. To radiate the large amounts of power required to bridge transoceanic stretches, a large and lofty radiating system or aerial is required. The main tower at Tucker- ton (N. J.) is 850 feet high. At the New Brunswick (N. J.) station a row of 400-foot masts stretching 6,000 feet from the station support the ''multiple tuned" aerial sys- tem. The latest form of aerial is that employed at the Radio Central station. It consists of a line of 410-foot towers with 150-foot spreaders at the top of each, and stretching a mile and a half from the station building.. Twelve such rows of towers, each fed by its own high- frequency alternators and constituting in effect a separate transmitting station, will enable the Radio Central sta- tion to be used . for simultaneous communication with an 2:^a Twelve of the seventy-two steel towers comprising the aerial supports of the Radio Central wireless station. Each tower is 410 feet high, while the cross-arm measures 150 feet from tip to tip. 270 RADIO FOR EVERYBODY equal number of receiving stations abroad when com- pletely realized. An area of about ten square miles is being devoted to this giant station, which will be by far the largest in the world when completed. In radio reception there have also been very marked advances during the last few years. Each row of appara- tus in its especially shielded cases is capable of handHng one transoceanic channel. Each operator is provided with a telegraph key controlling the transmitter on the corre- sponding circuit, so that he can, if necessary, "break" or interrupt the transmitting operator to obtain a correc- tion or other information from the station which he is receiving. When reception at high speed was desired, recording was sometimes accomplished on modified phonographs which were run rapidly and the records were later trans- scribed at lower speeds by a number of operators. This method of receiving at high speed has been superseded by modern forms of ink recorders especially developed for radio reception. Photographic recorders, in which the received signals are photographed as a wavy line on a paper ribbon, have also been used in high speed reception. Wire and radio communication, according to Mr. Gold- smith, should work hand in hand in any comprehensive scheme of world communication. The land wires and cables have very clearly demonstrated their great capabili- ties and usefulness ; but radio communication, even at this early state in its development, has shown that it should be considered as an integral element of any well-considered plan for communicating all over the globe. Today ap- proximately 15 per cent of the traffic across the Atlantic from the United States is handled via radio, which is a hopeful showing for a new art, to be sure. To the extent that there is harmonious and intelligent co-operation be- tween the various communication systems, we may hope for the satisfactory solution of the problem of giving every person on earth rapid and reliable communication. Looking up at the top of one of the steel towers of the Kadio Central wireless station. The cross-arm at the top serves to support the sixteen wires which form the aerial. 272 RADIO FOR EVERYBODY When Wire and Wireless Work Together Fortunately, there are no physical limitations to prevent the interconnection by skilled persons of wire line and radio circuits. Messages received by radio telegraphy or radio telephony can be automatically transferred to wire lines and over them relayed to any point reached by them. Conversely, telegraph or telephone .signals on a wire line can be used to control radio telegraph or radio telephone transmitters. So that any wire system may be extended by the addition of radio relays and, reciprocally, any radio system may be extended by the addition of wire relays. This process of adding wire and radio Hnks or relays to each other can be carried on to practically any desired extent and should constitute an element in the communication systems of the future. On a moderate scale it is being carried out commercially today in the case of messages from European countries received by the Radio Corporation of America at its receiving stations on Long Island and in New Jersey. From these points the messages are automatically relayed over wire lines to the New York traffic office of the company in the heart of the financial district, where the receiving operators take down the messages by ear, if sent at hand speed, or the messages are automatically written down by ink re- corders if received at high speed. A similar transfer of telephone signals to and from wire hues has been demonstrated as a commercial propo sition in highly successful fashion by the American Tele- phone & Telegraph Company, in the Avalon-Los Angeles radio toll circuit, in which regular radio telephone mes- sages are sent by radio over a 31 3^ air gap without the subscribers realizing that their conversation is being handled in any other manner than by wires. Experiments have been carried on with the steamship Gloucester and the Deal Beach radio-phone experimental station, and per- sons have talked over the regular telephone instrument in their home to the ship at sea. More recently, still more spectacular experiments have been carried on with liooking up through the center of one of the steel towers. While this steel work may appear delicate because of its simplicity, it possesses great strength because of the diagonal bracing. 274 RADIO FOR EVERYBODY the steamship ''America'' while 400 miles out at sea. It is only a matter of time when we shall be able to 'phone to the ship at sea with the same ease that we call up long-distance points. Certain countries, such as the United States, are so situated geographically as to serve naturally as important relay centers for inter-continental communications. Com- munications from Europe to South America, and from Europe to the Far East naturally pass over the United States. In view of the rapid rate at which the power, required to bridge a certain distance reliably by radio, increases with distance for spans of more than a few thousand miles, it is advantageous, holds Mr. Goldsmith, to establish relay points in the United States whereby communications from Europe to the regions named will be received in the United States and thence automatically or otherwise relayed to their destinations. The Traffic Capacity of the Long-Distance Ether Some doubt may have been entertained by engineers as to the traffic-carrying capacity of the ether for long-dis- tance communication. The figures for long-distance tele- graphy can be at least roughly estimated without serious difficulty. We shall assume continuous wave transmis- sion, with an appropriate form of key modulation in sending the dots and dashes, and without any tone modula- tion whatever. Under these conditions, and taking into account both side bands produced as the result of actual transmission, it has been found that a speed of 100 words (or 500 letters) per minute corresponds to the occupa- tion of a band of frequencies in the ether roughly 100 cycles wide. This is on the basis that the radio-fre- quency generator maintains its frequency constant during transmission. We shall also assume that the receiver is sufficiently selective to exclude all signals on frequencies outside of this 100 cycle band. Under these conditions, we may say roughly that on each cycle per second of available ether frequencies we can transmit one word The power plant and station building of the Radio Central wireless station. In the foreground are the sprays and cooling basin for cooling and condensing purposes, forming part of the power plant operation. 276 RADIO FOR EVERYBODY per minute. Assuming further that long-distance traffic will be handled in the range of wave lengths between 6,000 meters and 40,000 meters, a reasonable assump- tion on the basis of present-day practice — and also a conservative one — we shall have available a band of ether frequencies of from 50,000 to 7,500 cycles per second, or 42,500 cycles in all. According, we can ultimately transmit at least 42,500 words per minute via radio over long distances, or no less than 61,200,000 words per day. If we extend the range of available wave lengths for long- distance communication below 6,000 meters through the further reduction of atmospheric disturbances ; if we eliminate one of the side bands resulting from transmis- sion; and if we assume the possibility of using the same wave length for transmission at several points of the earth's surface with directional discrimination between several transmitters at the receiving station, the already enormous daily message-carrying capacity of the ether will be greatly increased. As a matter of comparison, we may state that the figure of 61,200,000 words per day is roughly 150 times the actual traffic sent across the Atlantic Ocean by cable and radio at the present time. A number of perfectly reasonable requirements must be met by transmitting and receiving stations in order to realize the ultimate capacity mentioned above, according to Mr. Goldsmith. The transmitters must have strictly constant generator frequency consistent with their key signaling speed and the receivers must be highly selective for a correspondingly narrow range of frequencies and yet follow the signals accurately. Even today radio en- gineers are confident that these results will shortly be obtained by carefully chosen technical expedients. The nature of world communication makes it interna- tional in character. Both wire lines and radio waves know nothing of national boundaries, a fact which is sometimes resented by the nations, particularly during hostilities. It is this essentially international character of long-dis- tance communications, particularly of the unguided 278 RADIO FOR EVERYBODY variety, which has led to the international regulation of radio communication. In 1912, the London Radio Con- vention was agreed to by most of the nations of the world and given force by corresponding national legisla- tion in each case. These regulations of the London Con- vention were fairly general in character and covered the most essential points only. Thus there was left con- siderable and proper leeway for each nation to settle its own national problems in communication according to local needs and the nature of local institutions. It would seem that some such policy is wise, especially where im- portant matters of truly international scope clearly require settlement in the interests of eiTecive communication and to avoid inevitable disputes. Beyond this point which is defined without much difficulty by the experts in the art, regulation becomes burdensome and tends to retard the progress of the radio art and to discourage initiative. For the rapid growth of world communication, as far as a radio is concerned the degree of regulation of the art by the various governments should be restricted to the enforcement of the international regulations together with such control of the nationality of the owners and personnel of the radio companies as may be deemed nec- essary for national security. The entire field of un- guided communication, as Mr. Goldsmith calls radio, is so new and is developing so rapidly that great harm can be done by well-meaning but injudicious legislators and officials. Like all pioneer arts, its successful and speedy, development depends on wide freedom of experiment by enterprising investigators and encouragement of effort on the part of wide-awake companies. Chapter XL HOW TO CONSTRUCT SIMPLE RADIO RECEIVING SETS FOR RADIO- PHONE PROGRAMS AND now for those who wish to construct their own simple receiving outfits, here is a chapter devoted to their particular interests. First of all we shall describe an entire receiving station, including antenna as well as a crystal detector receiving set. This station will enable one to hear the messages sent from medium^ower transmitting stations within an area about the size of a large city, and to hear high-power stations within 50 miles, provided the waves used by those stations have wave frequencies between 500 and 1500 kilocycles per second, which, translated into plain Ens^lish, means w^ave lengths between 600 and 200 meters. Much greater distances are often covered, especially at night. If a person constructs the coil and other parts as indicated, the total cost of this set can be kept down to about $6.00. If, however, a specially efficient outfit is desired, the cost may be about $15.00. The Essential Parts of Receiving Station The set about to be described has been designed by the Bureau cf Standards at the request of the States Relations Service of the United States Department of Agriculture, for the use of boys and girls radio clubs. There are five essential parts to this receiving station. 280 RADIO FOR EVERYBODY as well as any other receiving station, namely : the antenna, lightning switch, ground connections, receiving set proper, and telephone receivers. The received signals come into the receiving set through the antenna and ground connec- tion. In the receiving set they are converted into an electric current which produces the sounds in the telephone receivers. The telephone receiver is either one or a pair of telephone receivers worn on the head of the listener. A number of telephones may be used with such a set, but a loud-speaking device, which does away with head phones, is not practical with a simple set of this kind. The purpose of the lightning switch is to protect the receiving set from damage by lightning. It is used to connect the antenna directly to ground when the receiving station is not being used. When the antenna and the connection to the ground are properly made and the light- ning switch is closed, an antenna acts as a lightning rod and is a protection rather than a source of danger to the building. The principal part of the station is the receiving set proper. In the set described in the following paragraphs it is subdivided into two parts, the tuner and the detector, and in more complicated sets still other elements are added. The Antenna, Lightning Switch and Ground Connections The antenna is simply a wire suspended between two elevated points. Wherever there are two buildings, or a house and a tree, or two trees with one of them very close to the house, it relieves one of the need of erecting one or both antenna supports. The antenna should not be less than 30 feet above the ground and its length should be about 75 feet. (See Fig. 1.) While this figure indicates a horizontal antenna, it is not important that it be strictly horizontal. It is in fact desirable to have the far end as high as possible. The "lead-in" wire or drop-wire from the antenna itself should run as directly as possible to the Hghtning switch. If the position of the adjoining build- ings or trees is such that the distance between them is RADIO FOR EVERYBODY 281 greater than about 85 feet, the antenna can still be held to a 75 foot distance between the insulators by increasing the length of the piece of rope (D) to which the far end of the antenna is attached. The rope (H) tieing the antenna insulator to the house should not be lengthened to overcome this difficulty, because by so doing the antenna "lead-in" or drop wire (J) would be lengthened. Details of Parts — The parts will be mentioned here by reference to the letters appearing in Figures 1 and 2. Fig. 1. — Construction of antenna for reception purposes. A — screw eye; B — rope; C — pulley; D — rope; E — insulator; F — antenna; G — Insulator; H — rope; I — screw eye; J — lead-in wire; K — lightning: switch; L — ground wire; M — ground pipe; N — lead to receiving set; O^ — insulating tube. A and I are screw eyes sufficiently strong to anchor the antenna at the ends. B and H are pieces of rope }i or j/z inch in diameter, just long enough to allow the antenna to swing clear of the two supports. D is a piece of ^ or ^ inch rope sufficiently long to make the distance between E and G about 75 feet. C is a single block pulley which may be used if readily available. 282 RADIO FOR EVERYBODY E and G are two insulators which may be constructed of any dry hardwood of sufficient strength to withstand the strain of the antenna ; blocks about 1^ x 2 x 10 inches will serve. The holes should be drilled as shown in Fig. 1 sufficiently far from the ends to give proper strength. If wood is used the insulators should be boiled in paraffin for about one hour. If porcelain wiring cleats are avail- able they may be substituted instead of the wood insulators. If any unglazed porcelain is used as insulators, it should be boiled in paraffin the same as the wood. Regular antenna insulators are advertised on the market, but the two improvised types just mentioned will be satisfactory for an amateur receiving antenna. F is the antenna about 75 feet between the insulators E and G. The wire may be No. 14 or 16 copper wire either bare or insulated. The end of the antenna farthest from the receiving set may be secured to the insulator (E) by any satisfactory method, being careful not to kink the wire. Draw the other end of the antenna wire through the other insulator (G) to a point where the two insulators are separated by about 75 feet, twist the insulator (G) so as to form an anchor as shown in Fig. 1. The re- mainder of the antenna wire (J) which now constitutes the ''lead-in" or drop-wire should be just long enough to reach the lightning switch. K is the lightning switch. For the purpose of a small antenna this switch may be the ordinary porcelain base, 30 ampere, single-pole double-throw battery switch. These switches as ordinarily available have a porcelain base about 1 by 4 inches. The "lead-in" wire (J) is attached to this switch at the middle point. The switch blade should always be thrown to the lower clip when the receiving set is not actually being used and to the upper clip when it is desired to receive signals. L is the ground wire for the lightning switch; it may be a piece of the same size wire as used in the antenna, of sufficient length to reach from the lower clip of the lightning switch (K) to the clamp on the ground rod f M). M is a piece of iron pipe or rod driven 3 to 6 feet into RADIO FOR EVERYBODY 283 the ground, preferably where the ground is moist, and extending a sufficient distance above the ground in order that the ground clamp may be fastened to it. Scrape the rust or paint from the pipe before driving in the ground. Fig:. 2. — Arrangement of receiving- instrument and connections with antenna and ground.. J — lead-in wire; K — lightning switch; Jj — ground wire; N — lead to receiving set; O — insu- lating tube; P — receiving set; Q — ground for receiving set. N is a wire leading from the upper clip of the lightning switch through the porcelain tube (O) to the receiving set binding post marked "antenna." O is a porcelain tube of sufficient length to reach through the window casing or wall. This tube should be mounted in the casing or wall so that it slopes down 284 RADIO FOR EVERYBODY toward the outside of the building. This is done to keep the rain from following the tube through the wall to the interior. Fig. 2 shows the radio receiving set installed in some part of the house. P is the receiving set which is described in detail below. N is the wire leading from the ''antenna" binding post of the receiving set through the porcelain tube to the upper clip of the lightning switch. This wire, as well as the wire shown by Q, should be insulated and preferably flexible. A piece of ordinary lamp cord might be un- braided and serve for these two leads. Q is a piece of flexible wire leading from the receiving set binding post marked "ground" to a water pipe, heating system or some other metallic conductor to ground, except M, Fig. 1. If there are no water pipes nor radiators in the room in w^hich the receiving set is located, the wire should be run out of doors and connected to a special "ground" below the window, which shall not be the same as the "ground" for the lightning switch. It is essential that for the best operation of the receiving set this "ground" be of the very best type. If the soil near the house is dry it is necessary to drive one or more pipes or rods sufficiently deep to encounter moist earth and connect the ground wire to the pipes or rods. This distance will ordinarily not exceed 6 feet. Where clay soil is encoun- tered this distance may be reduced to 3 feet, while in sandy soil it may be increased to 10 feet. If some other metallic conductor, such as the casing of a drilled well, is not far "away from the window, it will be a satisfactory "ground." TuNER^ Detector and Telephone At least the telephone will have to be purchased. The tuner and certain accessories can be made at home. Tuner {R, Fig. 3) — This is a piece of cardboard or other non-metallic tubing with turns of copper wire wound around it. The cardboard tubing may be an oatmeal box. Its construction is described in detail below. RADIO FOR EVERYBODY 285 Crystal Detector (S, Fig. 3) — The construction of a crystal detector may be of very simple design and quite satisfactory. The crystal, as it is ordinarily purchased, may be unmounted or mounted in a little block of metal. For mechanical reasons the mounted type may be more satisfactory, but that is of no great consequence. It is very important, however, that a very good tested crystal be used. It is probable also that a galena crystal will be more satisfactory to the beginner. The crystal detector may be made up of a tested crystal, three wood screws, short pieces of copper wire, a nail, set screw type of binding post, and a wood knob or cork. The tested crystal is held in position on the wood base by three brass wood-screws as shown at I Fig. 3. A bare copper wire may be wrapped tightly around the three brass screws for contact. The assembling of the rest of the crystal detector is quite clearly shown in Fig. 3. Plione (T, Fig. 3) — It is desirable to use a pair of telephone receivers connected by a head band, usually called a double telephone headset. The telephone receivers may be any of the standard commercial makes having a resistance of between 2000 and 3000 ohms. The double telephone receivers will cost more than all the other parts of the station combined but it is desirable to get them, especially if one plans to improve his receiving set later. If one does not care to invest in a set of double telephone receivers a single telephone receiver with a head band may be used; it gives results somewhat less satisfactory. Accessories — Under the heading of accessory equip- ment may be listed binding posts, switch arms, switch con- tacts, test-buzzer, dry battery and boards on which to mount the complete apparatus. The binding posts, switch arms and switch contacts may all be purchased from dealers who handle such goods or they may be quite readily improvised at home. There is nothing peculiar about the pieces of wood on which the equipment is mounted. They may be obtained from a dry packing-box and covered with paraffin to keep out moisture. 286 RADIO FOR EVERYBODY Details of Construction The following is a detailed description of the method of winding the coil, construction of the wood panels, and mounting and wiring the apparatus. Tuner — See R. Fig. 3. Having supplied one's self with a piece of cardboard tubing 4 inches in diameter and about y2 pound of No. 24 (or No. 26) double cotton cov- ered copper wire, one is ready to start the winding of the tuner. Punch two holes in the tybe about }^ inch from one end as shown at 2 on Fig. 3. Weave the wire through these holes in such a way that the end of the wire will be quite firmly anchored, leaving about 12 inches of the wire free for connections. Start with the remainder of the wire to wrap the several turns in a single layer about the tube, tightly and closely together. After ten complete turns have been wound on the tube hold those turns snugly while a tap is being taken ofif. This tap is made by making a 6 inch loop of the wire and twisting it together at such a place that it will be slightly staggered from the first tap. This method of taking off taps is shown quite clearly at U, Fig. 3. Proceed in this manner until six twisted taps have been taken off at every ten turns. After these first seventy turns have been wound on the tube then take off a 6 inch twisted tap for every succeeding single turn until ten additional turns have been wound on the tube. After winding the last turn of wire anchor the end by weaving it through two holes punched in the tube much as was done at the start, leaving about 12 inches of wire free for connecting. It is to be understood that each of the eighteen taps is slightly staggered from the one just above, so that the several taps will not be bunched along one line on the cardboard tube. See Fig. 3. It would be advisable, after winding the tuner as just described, to dip the tuner in hot parafiin. This will help to exclude moisture. Upright Panel and Base — Having completed the tuner to this point, set it aside and construct the upright panel shown in Fig. 4. This panel may be a piece of wood approximately ^^ inch thick. The position of the several GROUND TUNLR. I-TURNTOEACHTAP I0-TURN5 TO EACH TAP TWI5TE:DTAP ^ i\\\ ^^^^S- ^ o ni vl ^^ 1 c \ m\\ ^^^^^^r; /ol l/l ■ JO \m\\ /I ^^^^^=^^ ^i rn 2 \ \\\ m i ^^^^^^=^^ '7i ^ 0* 11 il^ft^ 1 § vl' l\ ^B 1 < > \ W i\\ \ ^^s=^ ^ — 1 ^ \i\\ ^ \\\\ l\/^S 1 /^ ^^^^^ V AW^^g^ ^ ^^^^^^ Ar- li.''* ^^^^^ PI \ ITH- /|i -s^^- i'.';^- ~^ --- ~-^^^:::= i/ &^ H Vl/ ^ /' ! K^ o \ \ \V V "0 1 i 2 Z \ A ^■'y 1 ^ 1 H \ A / H i z (yi LV a t 1 "0 -^ -^- ■-=■ O 1 H f J 294 RADIO FOR EVERYBODY silk covered wire, with the adjacent turns side by side. At every ten turns the wire is looped and twisted together so as to form a tap, the loop being passed through a hole in the mailing tube and the tap brought over to its respec- tive switch point, to which it is connected after the primary is ready for assembling. The final turn of the primary is passed through two holes close together so as to hold the winding firmly in place, and the end brought to the last switch point. When the primary is completely wound, it is mounted on a block of wood which acts as the sup- port. It is left largely to the builder as to how the primary is mounted. One method is to use a round piece of wood of about the same diameter as the inside measurement of the mailing tube. This block is nailed on the end piece and the mailing tube is slipped over the block to which it can be firmly glued or tacked. The taps have, of course, been scraped and connected with their respective switch points. Now for the secondary. This is constructed in virtually the same manner, using a smaller mailing tube which fits inside the primary tube. The winding is of the same sized wire for the sake of simplicity, and taps are taken at every ten points and brought to their respective points of a ten- point switch. The mounting of the secondary must be carried out in the same manner as the primary, except that the latter has a stationary support, nailed firmly on the base board of the loose-coupler, while the former has a movable support. The movalDle support is made up in the manner indicated in our drawing, so that the secondary can be moved in and out of the primary, between guides. This completes the loose-coupler. The next step is to construct variable condensers, which are necessary for fine tuning. Inasmuch as the loose-coupler tunes only in big steps of ten turns at a time, it is necessary to employ variable condensers in order to effect sharp tuning so essential in the satisfactory reception of radio-pnone service. The simplest variable condenser to construct is probably the so-called book type, which is illustrated in our drawing. RADIO FOR EVERYBODY 295 This consists of two pieces of wood, which are fastened together by means of an ordinary hinge, so that they may be moved toward each other or drawn apart, as the case may be. A small wooden strip or even a nail prevents the two pieces from coming into actual contact. On each strip of wood is mounted a piece of sheet aluminum or copper, which acts as one of the condenser plates. Bind- ing posts are used in the manner indicated to make proper BINDING POST COPPER OR ALUMINUM PLATES BUMPER HINGE Top view of book type of variable condenser, consisting: of two boards hinged together, two pieces of copper or aluminum sheeting, arranged as shown. connections. The capacity of such a condenser is in- creased by moving the plates close together and lessened by moving them farther apart. Items That Must Be Bought The grid leak consists of a very high resistance unit. This is obtained by drawing a pencil line on a sheet of paper, and clamping this pencil line between two heavy copper washers so that the grid current for the vacuum tube must flow through this exceedingly high resistance. However, the grid leak has to be constructed with con- 296 RADIO FOR EVERYBODY siderable accuracy, so that it may be the part of better judgment to purchase a grid leak at any radio supply store. It is a matter of 50 or 75 cents, and it is certain to be correctly designed and constructed. The vacuum tube must be purchased, of course, and aside from the telephone receivers and batteries, it repre- sents the most expensive single item for such a set. The tube must be a detector tube, also known as a gassy tube, and costs either $4.00 or $5.00, depending on the type employed. A vacuum tube socket must also be purchased, at a cost of anywhere from 50 cents to $1.50, depending on the type selected. A vacuum tube requires two batteries, namely, the filament battery of six volts and the B or plate battery of 22^ volts. A 6-volt storage battery gives the best service for filament current, because the heavy drain of the vacuum tube filament soon wears out any dry battery. Still, if the reader is going to construct his own set it is almost certain that he will not want to go to the expense of purchasing a storage battery, hence dry batteries must be used. Four or five cells of dry battery may be used, although it will increase the life of the dry cells a great deal if two sets are employed, connected in what is known as series-parallel. That is to say, four or five cells are connected in series, with the carbon of one coil going to the zinc of the next cell. Then, the zinc of one battery is connected with the zinc of the other battery, and the carbon of one battery with the carbon of the other battery. This arrangement gives a battery of twice the amperage or current, and the drain caused by the tube is not so serious. The filament rheostat may be made, although it will hardly pay when simple rheostats can be purchased for one dollar or less. The rheostat serves to control the filament current, which must be accurately regulated for satisfactory results, since the vacuum tube is a delicate piece of mechanism. The B or plate battery must be purchased. This battery RADIO FOR EVERYBODY 297 comes in a compact block, either in the large or the small size. There are two types of B battery, namely, the fixed voltage and the variable voltage types. The latter is rec- ommended, since it permits of regulating the plate voltage applied to the vacuum tube, and this is a most important consideration with many vacuum tubes. The telephone receivers must be bought, and it is well to invest in good receivers. If there is anything that tends to make or undo a radio receiving set it is the tele- phone receivers. Inexpensive receivers are certain to prove the most expensive in the long run, because the Arrangement of dry cells in series-parallel, in order to obtain a steadier voltage and a longer life from the dry battery used with vacuum tubes. owner of such receivers may soon tire of them and ask for something better, only to find that his inexpensive receivers have no market value and must therefore be junked. With all the various components constructed and pur- chased, ready for use, they are assembled as shown in our assembly drawing. To operate the set, the primary switch is placed on the middle switch point and the variable con- denser in the aerial-ground or primary circuit is varied slowly. ^leanwhile, the secondary switch is also placed on the middle switch point, and the secondary condenser is also varied. When the desired signal or radio-phone 298 RADIO FOR EVERYBODY service is intercepted, the switches and variable condensers are rapidly adjusted until the best results are obtained. All the while, of course, the vacuum tube is lighted and the filament rheostat is carefully adjusted for the loudest yet clearest sounds. Such a set will work satisfactorily over a range of 50 miles, although it is not as satisfactory as one using the Armstrong regenerative or feed-back circuit, which is somewhat more involved and is described further on in simple form for home construction purposes. However. the various radio supply houses are now offering the various components for regenerative receiving sets, as well as amplifier units. An excellent receiving set may be constructed by purchasing a vario-coupler, two vario- meters, grid leak and grid condenser, and the various other accessories such as the rheostat, vacuum tube and socket, binding -posts, and so on, connected as shown in our chapter on receiving sets. For really good results, as far as a home-made set is concerned, it is necessary to employ the regenerative arrangement. This arrangement, as has already been described elsewhere in this work, is virtually a self-am- plifier, and adds a great deal to the efficiency of the re- ceiving set. One of the very best yet simple receiving arrangements which has come to the attention of the author and which he has constructed for his own experimental use, is shown in the accompanying drawings. It is a verv simple form of two-circuit receiving set, using a plate variometer for the feed-back or regenerative agent. First of all, it is necessary to construct the main tuning member, which is simply a mailing tube measuring 3^ inches in diameter by 4 inches long, on which two wind- ings are carefully wound. The first winding consists of twenty turns of No. 20 B. & S. gauge double cotton cov- ered wire, wound close together, of course, while the sec- ond winding, starting one-eighth away from the end of the first winding, consists of 40 turns of same sized wire, also wound close together. The windings should be held I 5 ^ 0«! 9 or; & s o 1 o p p o & X p -3 ii 9 300 RADIO FOR EVERYBODY in place simply by making holes in the cardboard tube and passing the ends of the windings through these holes. Under no circumstances should the windings be varnished -40 TURNS FIBRE SHELL How the fixed winding: of the variometer is made. A frame work is built up with sheet fiber on a square form, and held together Avith shellac or glue. The wind- ing is placed on this form, as shown. or shellacked, as this introduces certain undesirable char- acteristics. Both windings are fixed, their wave length values being altered by variable condensers as shown in the accompanying wiring diagram. The variable condensers may be of the home-made variety, using the book type already referred to in the previous set. Two such condensers will be necessary, and it is well to make them of good size so that they will have ample capacity. One condenser is placed across the primary winding — or in series with it if the wave length of the antenna-ground circuit is to be reduced — while the other is placed across the secondary winding. RADIO FOR EVERYBODY 301 A fixed condenser must be constructed. This consists of nothing more formidable than a number of sheets of tin foil separated by pieces of paraffined paper. A good condenser may be made by cutting ten pieces of tin foil so that they will measure one inch wide by three inches long and cutting eleven pieces of paraffined paper so that they measure one and one-quarter inches wide by two and one-half inches long. The paraffined paper and the tin foil sheets are assembled in staggered order as shown in the accompanying sketch. The pile of tin-foil and paraffined paper can be placed between two pieces of cardboard and held together by means of a rubber band or piece of thread wrapped around the cardboard end pieces. The grid leak had best be purchased, for it is a rather 40 TURNS FIBRE SHELL Completed variometer, showing the movable coil partly turned. The fixed and the movable windings are connected in series, so that the current must pass through both of them, one after the other. 302 RADIO FOR EVERYBODY difficult thing to make even though it does not consist of more than a pencil line drawn on a piece of good paper and clamped between two copper washers. If the con- structor wishes to build the grid leak as well as other parts of the set, he is welcomed to try it, although it would seem that since this item costs but 50 cents to buy it ready made — and properly made — it is best not to waste time and effort in trying to construct a grid leak. Then we come to the filament rheostat. Here again, it is best to purchase a manufactured filament rheostat, which may run all the way from 75 cents to $2.00, depend- ing on how well it is made. The tube socket must also be purchased, representing an outlay of from 75 cents to $2.00, depending on the type selected. The "A" battery is the filament battery, and consists of either a dry battery, preferably composed of ten dry cells arranged in series multiple as depicted on page 297, or a 6-volt 20-ampere-hour storage battery. The "B" battery is the high-voltage battery for the plate circuit. It consists of a single block of battery supplying 22>^- volt current. The telephone receivers may be a single receiver or a regular head-set, according to taste — and pocktbook. Finally, there is the variometer used as the feed-back device. The variometer had best be purchased, for it is a difficult instrument for the home constructor to tackle. Of course, a variometer may be constructed, because it consists simply of a fixed winding and a corresponding turnable winding. But the point in the case is to make a variom- eter that will work properly, and that requires a little ex- perience and skill. However, if the builder insists on constructing the variometer, he may do so. A simple design is shown in the accompanying sketch. It consists of a stationary wooden frame, built up in the manner indicated, and a movable frame. Now the stationary winding is placed on a form made of fiber strip, shellacked together to make it strong. This frame, with its winding, is placed inside the stationary frame. The movable winding, on the other TINFOIL TINFOJL PAPER SEPARATORS THREAD FASTENINGS 11^^^ TERMINAL WIRE How the fixed coupler is made, and the construction of the small fixed condenser. The first drawing shows the mailing tube with twenty turns and forty turns for the primary and secondary windings. The second drawing shows the assembly" of the fixed con- denser. The third shows a side view of the assembled condenser. 304 RADIO FOR EVERYBODY hand, is wound on the movable form, as indicated. Each winding should consist of 60 turns of No. 20 double cotton covered wire. No nails should be used in making this instrument, glue or wooden pegs being used through- out. A suitable shaft should be provided, so that the movable coil can be turned by means of a handle. A dial can be drawn, with graduations from 1 to 100, or a dial ±A I'I'MI'I How the various components of the simple regenerative set are connected together. A — antenna; G — ground; P — primary; S — secondary; VCl — primary condenser; VC2 — secondary con- denser; FC — fixed condenser; GL, — grid leak; VT — detector tube; A — filament battery; B — "B" or plate battery; K — rheo- stat; T — telephone receivers; V — variometer for feed-back. and handle can be purchased from any radio supply house. However, after all is said and done, the best results will be obtained by purchasing a variometer, since this is a rather difficult instrument to construct — and construct right. The set is arranged as shown in our assembly drawing. It is a simple set to operate and permits of extremely sharp tuning. The regenerative arrangement makes for ^•3 So 'to f O ^1 C ;: or; (R X « a C n p 5" 5' "a! « p » j; 3 ffi 306 RADIO FOR EVERYBODY excellent results, so that this set will receive from radio- phone broadcasting- stations over 100 miles away under favorable circumstances, without an amplifier. With an amplifier, which may be readily constructed by purchasing the necessary components and assembling them in the manner indicated by the wiring diagrams in the chapter dealing with amplifiers, the range may be materially in- creased. Some companies are now offering complete receiving sets in knockdown form, so that the purchaser can wind the coils and assemble the components himself, thus sav- ing considerable money and gaining practical knowledge in radio construction. These sets are highly recommended to those who desire to build their own apparatus yet wish the best type equipment now available. Chapter XII. THE RADIO TELEPHONE OF TODAY AND TOMORROW ASIDE from the broadcasting o£ interesting pro^ grams, the radio telephone has other and very im- portant uses. It must become a part of the regular wire telephone system; indeed, it already forms part of our telephone system, although only in an experimental way. The Radio Link There is genuine romance in the story of the radio telephone. A dozen years ago it was a crude laboratory toy, with little prospect of ever becoming a practical, work- aday thing. It was handicapped with a most unsavory reputation, because it had been made the catspaw of fraudulent stock-selling enterprises. The very publicity which had been accorded in unstinted measure had done untold harm, for the general public had come to expect too much of this young and quite unwieldy means of rcommunication. The radio telephone started out as a competitor of the wire telephone, although in truth it could never hope to rival the more conventional system. Yet the radio tele- phone only started on its practical career when the tele- phone engineers — the very men against whom this newer form of communication was to compete — took an interest in certain radio equipment, particularly vacuum tubes, and 308 RADIO FOR EVERYBODY General scheme of the radio link as used between tlie California main phone system with that of the Santa Catalina Island and making arrangement, so that two messages can be developed them to a practical point. Today, the radio telephone is not a competitor of the wire telephone: it is an accessory. It became practical through* the efforts of the telephone engineers, but in turn it has made wire telephony possible over longer distances and with greater clearness than could ever have been possible with the former equipment. The radio telephone today is part and parcel of our wire telephone system, and it is fast becoming as practical as the latter. Indeed, were it not for the high cost of this form of communication, it would be quite within present accomplishments for any telephone subscriber to call up a relative or friend on an ocean liner several hundred miles off shore, the voice being carried over the usual telephone line to the central office, through trunk lines to the distant radio transmitter, and thence transmitted through the air to the steamer. The radio link, as the radio telephone RADIO FOR EVERYBODY 309 land and_ the island of Santa Catalina, connecting the mainland tele- them a single system. The radio link in this installation is a duplex handled at one time, or one in each direction. service is called when made a part of the usual wire tele- phone system, is destined to become commonplace within the next few years. Now the foregoing is not a mere flight of fancy. It is a matter of record that the American Telephone & Telegraph Company recently conducted a series of experi- ments with radio links and the transcontinental telephone line. Telephonic communication was established between the steamship "Gloucester," cruising off Deal Beach, N. J., and Santa Catalina Island, situated some thirty miles off the California coast in the vicinity of Long Beach. The telephonic communication, in this case, passed from the "Gloucester" to Deal Beach, N. J. ; from Deal Beach to New York via telephone line ; from New York to San Francisco via transcontinental telephone line; from San Francisco to Los Angeles via telephone line; from Los Angeles to Long Beach via telephone Hne ; from Long 310 RADIO FOR EVERYBODY Beach by radio to Pebbly Beach, on Santa Catalina Island. From ocean to ocean via radio, telephone line and radio again! The first commercial radio and connecting land toll line is the Santa Catalina Island and California radio link, which was set in operation well over a year ago. Radio telephone service between Santa Catalina and the main- land to connect up with the Bell System exchanges was installed at the request of the local telephone company. Catalina Island is one of the great tourist resorts in Cali- €" » i&^, ,,...^;. :... -'V;':"^-^"^' i SAMTA 'V^ CATALINA SS ', ^ T~~-v \ ,/ '"^ ~- f-v .; ' '•». f/ A^ PEBBu ^~ 7<^'BeACH AVALON Map and diagrram showing the radio link between the Cali- fornia mainland and Santa Catalina Island, and the wire sys- tems at either end, all of which function as a single unit when connected together in this manner. fornia. It attracts thousands of visitors daily throughout the year, who, heretofore, when they left the California mainland, remained completely isolated from the rest of the world until they returned to Los Angeles, except for a much-overloaded naval radio telegraph station on the island. That this radio link, which bridges the 31^-mile gap RADIO FOR EVERYBODY 311 between the island and the mainland, is not in the experi- mental stage may be gathered from the fact that it han- dles hundreds of messages each day. The large amount of commercial traffic with scarcely any interruption which the Avalon-Los Angeles toll circuit has carried every day since its opening, is an ample proof of the practicability of toll lines containing radio links, where, due to physical conditions, direct wire connections are impracticable. Mechanism of the Radio Links It is virtually impossible to delve deeply into the intri- cacies of the Avalon-Los Angeles radio link and toll cir- cuit, since it involves the most elaborate telephone and radio engineering practice. Suffice it to say that the dia- gram at the left of page 310 shows schematically the Avalon-Los Angeles circuit, consisting of a little more than one mile of wire line from the Avalon central office to Pebbly Beach, a 31^-mile radio link to Long Beach, and 25 miles additional wire circuit to Los Angeles. This combination wire and radio circuit is operated as a unit providing through telephone and signalling from Avalon to Los Angeles. At Avalon the circuit may be connected with any subscriber's line and at Los Angeles to any local subscriber's line, through local exchanges, or with other long-distance lines reaching practically any subscriber in the Bell System. The difficulties overcome to surmount interference from radio stations along the Pacific Coast and a naval station on Catalina Island, together with the many sets on ships, were many, we learn from the engineers of the American Telephone & Telegraph Company and the Western Elec- tric Company, who installed the radio link. Practically uninterrupted service now has been made possible, how- ever, and the quality of the transmitted speech is almost perfect; so much so, in fact, that a user of the telephone service that includes the radio link notices virtually no difference in the service. Among some of the technical obstacles it was found nec- essary to overcome before satisfactory operation of the 312 RADIO FOR EVERYBODY radio link was possible was the problem of housing the receiver and transmitting apparatus in the same building or in close proximity. This was accomplished by properly shielding all leads, shielding the receiver to prevent cross- talk from the transmitter, and the use of specially designed filter circuits for the receiver. The radio link is, in truth, a link. It functions as part of the regular telephone system with little or no extra complication, so far as the everyday operation and use of the system is concerned. Operators are located at the cen- tral offices in Los Angeles and Avalon, operating ordinary telephone switchboards. They handle the radio link traf- fic in the same manner as if the wire circuits were being- handled. They ring up in the same way by the operation of the usual ringing key. In fact, the installation of a voice frequency ringing system, which permits the use of a ringing key at the regular exchange switchboards in Los Angeles and Avalon, for signalling gave rise to some trouble and necessitated some changes in design before it was successfully placed in operation. This was due to the fact that the apparatus was rushed for the installation before it had been given a thorough field trial by the engi- neering department of the Western Electric Company. The radio link is a duplex system; that is to say, one message may be sent in each direction simultaneously. For transmitting, a fair-sized aerial is employed, as indi- cated in bird's-eye view on pages 308 and 309, while for re- ceiving a loop antenna is used at each end. These loops are of the solenoidal type, six feet square, and consist of only four or five turns each. To make the duplex opera- tion a success, it goes almost without saying that excep- tional measures had to be taken, otherwise' the transmitter at one end would drown out the incoming signals on the loop antenna but a short distance away. The elimination of such interference was attained by the use of different carrier frequencies for transmission in the two directions. Filters, amplifiers and repeaters are employed in large numbers, the basis of all this equipment being the im- proved vacuum tube. An interesting feature of the receiv- 314 RADIO FOR EVERYBODY ing apparatus is the provision of relays which close a buzzer alarm circuit when the filament of any vacuum tube fails. The radio transmitter employed at either end makes use of a circuit in which the oscillations are generated directly in the antenna circuit. The modulation of the radio car- rier frequency is accomplished by what is known as the "constant current system," in which both oscillator and modulator tubes are of 50 watts rating. These tubes are of the coated filament type, having relatively low filament power consumption and very constant operating charac- teristics. The transferring of the speech current from the telephone line to the radio link is an elaborate process. Briefly, it may be described in this manner : The speech current is applied to a speech amplifier tube, through an im/put transformer. The output of this amplifier is im- pressed on the grid circuits of the two parallel modulator tubes through a transformer. The action of these modu- lator tubes is that of an amplifier and their ouput voltage is impressed on the plate circuits of the two oscillator tubes by means of a reactance, which is common to the modulator and oscillator plate circuits. This modulation of the oscillator plate potential results in speech frequency variation of the amplitude of the antenna current. The frequency of the antenna current when not modulated is nearly that corresponding to the free period of the antenna circuit. A Record to be Proud Of Since the radio link is the only telephone channel be- tween the island and the mainland, it was very heavily overloaded from the day of opening until the cessation of the summer tourist traffic in the latter part of September, 1920. Due to the methods employed, the high grade cir- cuit, and so on, a great deal more traffic is handled over this circuit than is generally handled by a single toll line. A record of all of the interruptions to service is kept at both of the stations together with the cause of the delay, its duration, and other information. It is interesting to Vacuum type employed in radio transmission, especially for the sending: end of the radio linli. 316 RADIO FOR EVERYBODY note that althouo^h the circuit was open to commercial service during the worst of the static season, subscribers had but Httle or no difficulty in using the circuit. Trans- mitting frequencies! of 400 and 470 meters were chosen for the stations after an extensive survey of the ether, so that the telephone would cause the least interfernce to and be interfered w^th the least by radio stations in the vicinity. Some trouble was experienced from the Avalon spark station located about one mile from the receiving station. Avalon transmits on 300 meters, while the Pebbly Beach station had its receiving apparatus tuned to 470 meters. Upon investigation it proved that the wave emitted by the spark transmitter was a broad one, and that when the wave is kept sharp and within certain definite limits of purity, so to speak, little or no trouble is experienced from this station. The circuit, due to the choice of sites, directional char- acteristics of the loop antennas, and selectivity of the radio receivers, is quite free from interference and it is only occasionally that an interfering spark signal is heard. The harmonics from the Poulsen arcs installed at the Naval Radio Stations at San Diego and Englewood, Cali- fornia, have given rise to some trouble. If the arc har- monic beats with the radio carrier and side frequencies of the radio telephone station at either an audible or nearly audible rate, the quality of the speech over the circuit may be affected materially. This is in effect the same result which obtains when speech signals are received on an ordinary heterodyne receiver when the local oscillator is not adjusted to the same frequency as that of the trans- mitter. Although this trouble can be eliminated as soon as it is discovered by shifting the carrier frequency of the radio telephone transmitter a few thousand cycles, it is obvious that in the future, when many stations may be expected to be operating, this difficulty must be eliminated in a more elaborate manner. The radio link also provides for a full duplex radio tele- graph circuit, capable of sending and receiving messages in two directions at the same time. Ordinary telegraph Special form of switchboard and radio controls for connecting the radio link with the regular telephone system. 318 RADIO FOR EVERYBODY instruments are used at the terminals and ordinary tele- graph lines lead to the radio installation. This duplex telegraph service operates simultaneously with the radio telephone with no interference whatsoever. The Radio Links at Sea The day is not far distant when every passenger steamer at sea will be just as much within reach of the regular telephone system and just as much an integral part of that system as the modern city apartment. There is nothing new in this prophecy : it has been talked about and virtually promised ever since radio telephony came into existence a decade and a half ago. But today we are making very substantial progress toward the early realization of telephony from ship to shore, along with all the other things promised for radio telephony. Already we are telephoning to sea over the regular tele- phone lines. Experiments are being carried on, and while much remains to be done in the wa,y of perfecting and refining the various details of this combined telephone and radio telephone system, the results indicate that the idea is feasible and most likely practical. A person talks over the regular telephone line and listens in the same manner as usual. The other person on board ship also speaks in the usual manner. Aside from occasional interference from other radio transmitters, especially radio telegraph, there is nothing to indicate that the conversation is other than an ordinary telephone conversation. Recently an official of the Bell System was called to the telephone at his residence in New Canaan, Conn,, to answer a call from Captain Rind, who was on his ship the "America" of the United States Line as it approached New York. At the time, the "America" was still 24 hours from port, or about 370 miles distant. "Hello, this is Captain Rind." "Captain, this is Mr. Thayer of the telephone company. I'm up in New Canaan. I understand you are three or four hundred miles at sea." I? OS o 2. ^ i L ^ 1^^? '^^^^m^^Kmmm^^mmm 320 RADIO FOR EVERYBODY "Yes, we were 370 miles from Ambrose light at 7 :30. We expect to dock tomorrow evening at 7 or 8/' "What kind of a trip are you having?" "W^e're having a good trip for this time of the year." ''Well, I'm glad to have had the pleasure of speaking to you. I think It is fine that we can meet and talk this way." That was how the conversation ran. Over 100,000 per- sons heard the conversation ; for the radio link, connecting the wire telephone system with the ship radio set, makes use of radio waves that may be intercepted and heard with the usual radio receiving set. It may be that at some future date some combination of wave lengths will be em- ployed to make the radio telephone link more or less pri- vate; but for the time being the conversations are more or less public because of the large number of amateur receiving sets within range. Preliminary to her last voyage to Europe, the steam- ship "America" had been equipped with a radio tele- phone set. Throughout the eastward trip tests were car- ried out between the ship and the radio telephone station of the Bell System located at Deal Beach, N. J., some 33 miles south of New York in an air line. These tests were overheard night after night by numerous radio amateurs along the North Atlantic coast, and led to many questions concerning their purpose. Similar inquiries were antici- pated upon the return of the ship and it was thought de- sirable by the telephone officials to advise the public by means of a demonstration before representatives of the press. The evening of March 5th was selected as the time for this demonstration, since the ship was scheduled to be then between 350 and 400 miles from port, a distance consid- ered to be the fair working range, under normal atmos- pheric conditions, for the radio transmitters both on board ship and at Deal Beach. The success of the demonstration proved that the time had been well chosen ; for, with the exception of 10 or 15 minutes during which the wireless waves were subject to "fading," as the radio engineers say. RADIO FOR EVERYBODY 321 telephoning between the ship and shore proceeded without the shghtest difficulty. Tying Ships and Shore by Telephone The schematic drawing on pages 322 and 323 gives a general idea of how these experiments in ship-to-shore telephony have been carried on. The reader will note that two separate stations are being used on the Jersey coast. Deal Beach being the transmitting station and Elberon the receiving station. For those who are more technically in- clined, it might be pointed out that the wire circuit was operated on the four-wire principle between Walker Street and the radio stations, and on the ordinary two-wire prin- ciple from Walker Street to New Canaan. A hybrid coil and balancing network, such as forms an essential part of all telephone repeaters, established the union between the two- and four-wire circuits. The steamship ''America," belonging to the United States Shipping Board fleet, is a 28,000-ton vessel en- gaged in passenger service between New York, Cherbourg, and Bremen. On the trip of which we are writing she carried a large booking of passengers who, during the pro- gress of the tests, not only manifested considerable inter- est in them but also expressed in no uncertain terms their willingness to talk with persons on shore should they be given the opportunity. These passengers, in turn, had many friends in this country who were equally anxious to communicate with them; indeed, the engineers in charge of the Deal Beach station reported an avalanche of more telephonic calls than they took time to count from parties who wanted permission to talk with friends on board. One of these requests actually came by telephone from as far west as Chicago. The demonstration not only brought out the possibilities of ship-to-shore communication, but also illustrated its shortcomings — shortcomings which are, in large measure, characteristic of radio in all its forms. At regular inter- vals throughout the test, which lasted for over an hour, intelligible communication with the ship was prevented by General scheme ox the radio link as employed to couple up a ship with the wire telephone system. This particular diagram applies to the experiments conducted by the American Telephone & Telegraph Company between the steamer "America" and the Deal Beach sta- tion. The arrangement in the large circle represents the coupling system at the test room in the Xew York headquarters of the telephone conxpany. Two-way communication is maintained with the radio link, by using a transmitting and a receiving station at the land end, as depicted. 324 RADIO FOR EVERYBODY interference from spark stations, most of which were on vessels at sea, the spark stations near New York very generously having stopped their sending during the period of demonstration. The elimination of interference be- tween stations, all engaged in carrying commercial busi- ness, is one of the important technical problems of radio still waiting solution. Another limitation of the radio telephone was forcibly brought out by the number of telephone calls which came in from persons who said they had simple radio sets in their homes and were listening in on the whole conversa- tion between the speakers on shore and on the ship. A telephone message, once it has been given to the radio transmitter for propagation through the air, is virtually public property, and as upwards of one-half million radio amateurs throughout the country know, it is the simplest matter in the world to listen in on such a message. How- ever, there are ways in which secrecy may ultimately be obtained for the radio link of a telephone system. Moreover, atmospheric conditions exert a marked in- fluence upon the ease with which a radio message travels through space. These conditions vary greatly from day to day and from hour to hour. This can well be illustrated by the observations which have been made in connection with the radio link of the telephone system operating be- tween Long Beach, California, and Catalina Island. The distance between the mainland and the island is 30 miles, and the sets have been made sufficiently powerful to trans- mit speech across this distance under the most unfavorable conditions. On the other hand, it has been found that this amount of power is sufficient under exceptionally favorable conditions to make these messages readily audi- ble in New Zealand, 5,000 miles away. One of the most difficult radio problems the telephone engineers have en- countered is the transmission of a fixed quantity of cur- rent over the telephone lines in spite of the extremely variable intensity of the radio signals which are to be relayed over these lines. Another atmospheric phenomenon which is a source of no PS. If ^^ 9 So — 3 3* I = * id • « 3 .3 S5 so •5^ Bsp 326 RADIO FOR EVERYBODY most serious disturbance to radio transmission and which thus far has baffled all attempts to eliminate it, is the so- called "static." Fortunately, for the demonstration we have just described, there was very little static present. Its occurrence varies greatly with the season of the year, imd in the northern hemisphere is particularly trouble- some during summer. Indeed, there are hours and even days together when all but the strongest radio signals are obliterated. The radio link — the spanning of space between bits of regular telephone system — must come. The difficulties in the way of everyday, practical ship-to-shore communication are numerous and formidable, but they are certain to be brushed aside just as so many other obstacles in radio have been overcome. And What of the Future? To say that the radio link between land units and be- tween land units and ships at sea, is here in a practical and workaday way would be to exaggerate the facts in the case. Much remains to be done, as any one who has listened in to the experiments must realize. The inter- ference from other radio stations, the static, the fading away of a transmitter — all these features hamper radio telephony to a marked degree and must be very much ameliorated before we can hope for a system that will be as positive and reliable as our present wire telephones. Of course, for short spans, like the Long Beach-Avalon radio link, for which a good deal of power is employed in view of the short distance, the results are really reliable; but then the radio link must be capable of spanning many hundred miles, especially in telephoning to sea, if it is to be made of some commercial value. The question of secrecy is an important one, for nobody cares to be talking to a relative or friend while one hun- dred thousand other persons are listening in. Just so long as the messages stay on the wires, they are private, but at the present stage of radio telephony the moment these same messages are passed through the radio trans- 328 RADIO FOR EVERYBODY mitter they become public property. However, this ques- tion of secrecy can be solved — and it will be solved, in the very near future. There are several ways in which this end -can be attained. Perhaps the ultimate solution will be obtained by a system of double or triple waves employed simultaneously for the transmission of speech so that unless a person has a receiving set which intercepts a certain combination of waves, only a small and almost unintelligble part of the conversation will be detected. It is also quite possible to use a device at the transmitting end which continually alters the wave length of the trans- mitted radiophone waves, while the receiving set is also provided with a means of altering its wave length in step with the transmitter. As for static, it will be with us for many years to come. There have been many so-called static eliminators intro- duced from time to time, and we are assured over and over again that this arch enemy of radio has been banished for all time. But the fact remains that despite all kinds of static eliminators said to be practical and available, we continue to be troubled by static in our commercial and amateur work alike. The wire telephone was not perfected over night, and we cannot expect the radio telephone, which dates back to but a fev/ years in point of real, practical development, to evolve into perfected communication overnight. Then the problems of transmitting through space are consider- ably more numerous and involved than those of the wire telephone. It is going to take time, but the day must come when the radio telephone will be an everyday con- venience. INDEX "A" Battery 121 Abbreviations, Radio 171 Aerial 13, 24 Aerial and Antenna, Separate 215 Aerial and Ground 14. 95 Aerials, Types of 212-215 Air-Mail Radio Service 77 Amateur Stations 172 Alternating Current 24 Ammeter 24 Ampere 26 Amplifier 26. 195 Amplifying Tubes 127, 193 Amplifier, Two-Stage 182 Amplifier Units 191 Amplifiers, When and Where to Use 189 AmpHtude 26 Announcer, The 51 Antenna 13, 280 Antenna in City 99 Antenna, Various Types 101, 102 Antenna, Erecting 95, 147 Antenna Materials 96 Arlington, Va., to Paris, Experiments 50 Atmospherics 26 Audio Frequencies 26 Audio or Radio Frequency — Which? 182 Audio Frequency Amplifier 184 Avalon-Los Angeles Link 272, 311 Battery A 121 Battery B 26, 121 Battery, Storage 122, 124 Beats 140 Bed Springs, Use of 150 Boat, Radio-Controlled 250 330 INDEX Boxing Contest, Transmission of 71 Broadcasting 1, 26, 59, 61 Broadcasting Schedule 82 Broadcasting Station 55, 68 Bureau of Markets and Crop Estimates 85 Business, Radio in • 259 Buzzer Practice Set 167, 190 Buzzer Test -. 146 Cage, Aerial 241 Call Letters 176 Capacity (Abbreviated C) . 12, 26, 27 Cascade Amplification 27 Choke Coil 27 Chopper 241 Circuit 28, 129 Close Coupling ". 28 Code, International 165 Code, Learning 166, 168 Coil, Loading 113, 116 Combination Set 145 Communication, Telephonic 54 Compact Inductance 130, 132, 134 Compass, Radio 252 Concentrated Inductance • 132 Concert, Radio-Phone 70 Condensers 12, 28, 220, 222 Condensers Transmitting 220 Condenser, Variable 116 Congress and Radio 92 Connections, Simple 28, 112, 113 Continuous Wave (Abbreviated C. W.) 28 Counterpoise 28, 104 Cost of Sets and Parts 21, 291 Coupler 29 Crops and Market Reports 75, 79 Crystal Detector 29, 110,144, 285 C W and C W Signals '. 140, 162 C W Waves, Buzzer Modulated 240 C W, Popularity of 233 C W Transmitters - 235, 238 Damped and Undamped Waves • 9, 207 Department Stores and Radio 67 Detector 30 Detector, Crystal 110 Detector Tube 128 Dielectrics 220 Direct Current (Abbreviated D.C.) 30 INDEX 331 Distance in Radio Communication 6 Dry Batteries 123, 297 Electrical Symbol 25 Electrodjaiamic Receiver 194, 200 Electron 30 E. M. F 30 Ether • 30 Experimental Stations 50, 172 Filament Battery 121, 154 Flat-Top Aerial 30 Frequency 30 Future of Wireless 65 Government Use of Radio 91 Grid, Employment of 181 Grid Leak 32, 30Q Ground 32, 95, 102, 151 Ground for Transmitting 215 Guided Wave Transmission 256 Harmonics . . . • 32' Head Sets 135 Henry 32 Hertzian Waves 32 Hook-Ups 32, 152 Horn, Metal 193 Hot Wire Ammeter 33 Hydrometer, Use of 154, 156 Impedance 33. Inductance (Abbreviated L) 33 Inductance Coils 135 Installing the Receiving Set , 149 Instruments, Cost of 23 Instruments, Range of 23 Insulator 33, 98, 214 Insulator, Lead-in 103 Jamming Signals 211 Kilowatt (Abbreviated K.W.) 33- Lead-in Insulator 103. Lightning 105 Lightning Switch 105, 282 Long Island Radio Central 265 Loop Antenna ■ 33, 106, 107, 155 Loose-Coupler 130, 131, 292- Loud-speaker 33, 192, 194, 197, 198, 199 L-Type Antenna 101 Magnavox 204 Map of Radio Inspection Districts 175 Marine Type of Transmitter 225 532 INDEX Market News Service 75, 76 Megohm 33 Mica Condenser 223 Microfarad (abbreviated mfd.) 33 Microphone 33 Milliampere (abbreviated M.A.) 34 Modulator Tubes 246 Music, Transmission of 61 Natural Frequency 34 News, Distributing the 74 Night-Letters 266 Ohm 34 One Step Radio Frequency Amplifier 187, 188 Operating the Radio Receiving Set 143 Operation, Pointers on 159, 160, 161 Oscillating or Vibrating Currents 11, 34 Plate Battery 121 Phonograph Attachment 192, 202 Post Office Department and Radio Service 77,82 Potential (See EMF and Volt) 34 Primary and Secondary Circuits 129 Programs, Wireless 52, 53 Radiation 34 Radio Apparatus, Fitting 19 Radio Communication, Elements of 14 Radio Communication Laws 174 Radio Compass 252 Radio Control 248 Radio for Farmers 49 Radio Frequencies 34 Radio Frequency Amplifier 183, 184, 186, 190 Radio in the Home 41 Radio Inspection Districts 174, 175 Radio License 170, 172 Radio Link 50. 56, 307, 311, 318 Radio-Phone 1, 40 Hadio-Phone, Broadcasting 39, 58 Radio-Phone to Dots and Dashes 164 Radio Reception 93 Radio School 170 Radio Signals 16, 18 Radio Telegraphy, Use of 84 Radio Telephony in Simple Form 243 Radio Transmitter, What it Does 206 Radio Waves 15 Range of Instruments 23 Reactance (See Impedance) 34 INDEX :m Receiving Equipment 20, 93, 109, 12a Receiving Set, Simple ill Receiving Station 57 Reception, Radio 93 Rectifier 34 Rectifier and Stepdown Transformer 158 Regenerative Circuit 35 Regenerative Reception 138, 142" Regenerative Set 138 Remote Control 248 Resistance 35 Resonance 35 Rheostat 35 Rockv Point Station 266 Rotary Gap 227 Secondarv and Primary Circuits 129 Selectivity 35 Self Amplification 138 Sets. Receiving Ill Sharp Tuning 36 Sharp Waves 216 Signals. Radio 16 Sliders 113 Solenoidal Loop 107 Spark Gaps 224, 227 Spark Interference 163 Spark Signals and C W Signals 162' Spiral Loop 107 Standard Symbols 2.5 Static (See" Atmospherics) .26, 36. Stepdown Transformer 158 Storage Battery 36, 122 Storage Batteries, Rating of 156 Storage Batteries, Recharging 156' Storms 105 Studio, Broadcasting 68 Symbols, Standard 25^ Telephone Receivers ' 133 Telephone Receivers, Limitations of 201 Telephone System and Radio Link 50 Tickler Coil 138, 140- Tikker , 140 Time Signals 86, 89 Traffic. Long Distance 274 Transatlantic Radio to Transcontinental Telephone 78 Trans-Atlantic Station, Operating 268 Trans-Continental Telephone 66. 334 INDEX Transformer 36, 186 Transmission, Code . , : . . . 80 Transmitter 17 Transmitter Layout 230 Transmitters Sharply Tuned 216 Transmitting Condensers 220 Transmitting Tubes 243, 245 T-Type Antenna . 102 Tuner 136, 284 Tuning 8, 36 Tuning Coil 117 Tuning Inductance 211 Tuning, Simple Sets • 146 Tuning Transmitters 42, 219 Umbrella Type Antenna 101, 102 Undamped Transmitter 10 Undamped Waves 9, 36 Undamped Wave Transmitter 10 Vacuum-gap, Lightning Protector 106 Vacuum Tube 36, 37, 118, 121, 125, 154, 292, 299, 313, 315 Vacuum Tube, Amplifier 127 Vacuum Tube as Transmitter 229 Vacuum Tube Oscillator Method 236 Variable Condenser 116, 295 Vario-Coupler 130 Variometer 37,113, 114, 301 Velocity of Waves 37 Vibrating or Oscillating Currents 11 Voice Carrying 203 Voice, Radio 39 Voice, Transmission of 60 Voltmeter 37 Voltmeter, Use of 156 V-Type Antenna 101 Watt (abbreviated W) 37 Wave Length 7, 37 Wave Lengths, Questionnaire on 81 Wave Aleters 219 Wave Transmitter Damped 221 Waves, Damped and Undamped 9 Waves, Transmitting 17 Weather Reports 88 Wire and Wireless Work Together 272 Wired Wireless 254 Wireless Telephon}^ Early 44 Wiring 115, 288 World Communication 278 pBjj^ Date Due M 1 ,Qq| s ^ f) 1 BOSTON COLLEGE 3 9031 01460937 4 TK6550 dup. 7/27/82 T escarbcura, Austin C Radio for ever^ody L. v.. BOST ^ COLLEGE LIBRARY ^SITY HEIGHTS '^ILL, MASS. *-' . two weeks and may be lenewe*. period, unless reserved. Two cents u iS charged for each book kept overtime. If you cannot find what you want, ask the Librarian who will be glad to help you. The borrower is responsible for books drawn on his card and for all fines accruing on the same. f>