Radio Broadcast

RADIO BROADCAST

WILLIS K. WING, Editor JUNE, 1926

i RADIO BROADCAST ADVERTISER 97 109

J.B. 7he Gold Standard ofRadio R&ceivers MODEL TEN One Tuning Control ^bs Calibrated iri Meters.' Simply select your program from the newspaper, turn up its wavelength and in comes your station.

This precision-built FERGUSON, with its resistance-coupled amplifier, delivers all of the music exactly as broadcast. From the silvery strains of the soprano to the deep boom.' boom! of the bass drum each note comes through in perfect timbre and with all the countless delicate overtones and shadings that give music its greatest charm. Complete shielding of all tuning elements gives this Receiver its great selectivity. Write us!

J. B.FERGUSON,INC. 225 West 57th Street New York, N.Y. Sold by No Seasonal Models Authorized Ferguson Continually Developing Dealers Refinements, A6-TUBE RECEIVER

Tested and approved by RADIO BROADCAST THE ANTENNA SYSTEM AT 2 LO, THE MAIK BRITISH STATION

The "parent station" of the British Broadcasting Company system has its towers located atop Sel/ridge's store, Oxford Street, London. head This The antenna is 125 feet high. Many British listeners are content with simple crystal reception, using phones. station, in common with the other main stations of the system, gives a crystal range of about twenty five miles. Signals from this antenna have been received frequently in the United States and Canada, mainly during the three International Radio Broadcast Tests I RADIO BROADCAST

VOLUME IX NUMBER 2

JUNE, 1926

How New York Talks to London

The Story of a Wonderful Radio Engineering Accomplishment Due to Many and not a Single Individual How the Principle of "Single Side Band" Transmission Made Possible Transatlantic Telephoning A New Triumph for the Vacuum Tube By EDGAR H. FELIX

ISTORIANS have leaned heav- power broadcasting installation. A fairly lary. Its methods are complex but what ily on Samuel Morse's "What new principle was applied, known as single they accomplish is easy to comprehend. God hath wrought," and Alex- side band transmission. Only one- fourth to one-sixth the power is H ander Graham Bell's "Come Engineers can understand exactly just required to transmit a given distance; here, Watson, I want you," in describing how single side band transmission works, it occupies only one-half the wavelength the first telegraph and the first telephone. but to the layman it is simply another new band required by the usual broadcasting But the recent demonstration of two-way phrase added to radio's growing vocabu- transmitter, and it is less subject to fading transatlantic telephony, exactly fifty than the older methods of radio years to a day after Bell delivered telephone transmission. his famous message to Watson, pro- But what is single side band trans- duced no significant sentence to in- mission, and how is it accomplished? spire future generations of high You probably know that when school essayists. Instead, twenty or speech or music is heard from your thirty newspaper men on this side of receiver, it is responding to a carrier the Atlantic conversed with an equal wave, varied in intensity by the number of their confreres on the process of modulation, to accord other side about the weather, short with the sound waves at the broad- skirts, and prohibition. No one casting studio. The carrier wave utilized the opportunity to crystal- acts as the bearer or carrier of the lize the significance of the occasion audiofrequency currents. But what in an apt and epigrammatic phrase. you actually hear with your radio But the reason is not hard to find. receiver is the result of modulation. The first telegraph and telephone In your experience of fishing for were largely the products of a single long distance stations with a regen- individual's effort; their contribu- erative receiver, you have often tion, the successful solution of a heterodyned the carrier wave of a problem pursued in the face of pio- far-away stranger without being able neer difficulties. The transatlantic to "clear up" the signal to make it telephone, on the other hand, is the intelligible. Inveterate distance en- product of hundreds of creative thusiasts often become dyspeptic minds. No one man may point to from exasperation if frequently sub- it as his achievement, for, in the jected to this experience. What equipment installed by the America, they are after is modulation, not car- Telephone and Telegraph Company, rier. Single side band transmission the Radio Corporation of America, accomplishes the remarkable feat of and the British Post Office, literally transmitting only modulation, sup- thousands of inventions and pro- pressing the carrier before it reaches cesses, each contributing its part to the transmitting antenna. the success of transatlantic tele- we can make this more THE LOW-POWER UNITS Perhaps phony, are utilized. clear by an analogy. Suppose you Of the Rocky Point transmitter. The speech input, modulat- It was an extraordinary radio tele- have a gold coin, deeply engraved ing, filter, and amplifying panels, are depicted. The operator phone which these re- with both faces alike, which wish accomplished is regulating the volume of the incoming speech from New you sults, not a mere overgrown super- York by means of a potentiometer to reproduce at a distant place. In 112 RADIO BROADCAST JUNE, 1926 order to reduce the cost of the sample coin you would naturally slice it in half, since the design on one side, being the same as that on the other, would serve as a satisfactory model. Still greater economy is affected by making the sample slice of the coin just thick enough to include the deepest part of the engraving. The indentations in the coin correspond to the variations in the carrier wave produced by modulation. As long as these variations are transmitted, we have all that is necessary. Carrying the analogy still further, to reproduce the coin at the distant place, it is necessary to restore it to its normal thickness, in order to have a coin exactly like the one of which it is a replica. This, too, is one of the requirements in the reception of single

THE RECEIVING EQUIPMENT IS SHOWN HERE To the right the operator is adjusting the apparatus which is used to pick up Rugby's signals, while the gentleman sitting is responsible for the wire line circuit to New York. The necessary oscillator for restoring the carrier wave to the incoming single side band impulses is incorporated in the receiving equipment to the right

side band transmission. A local oscillator, set precisely to the suppressed carrier frequency, is necessary to restore the carrier in the receiver. This feature contributes to the secrecy attainable by the new system. The sine the carrier is familiar to almost A MODULATED RADIO FREQUENCY WAVE curve, representing wave, every broadcast listener. So is the effect of modulation upon the car- Would look like this if we could see it. As the author points rier. But observe, in the that modulation is out, modulation is really twice accomplished. Both the upper accompanying diagram, and lower components of the carrier wave are varied really twice accomplished in that both the upper and lower components

THE POWER STATION AT ROCKY POINT, LONG ISLAND

In this building are housed the commercial radio telegraph transmitters in addition to the radio telephone used for the transatlantic experiments JUNE, 1926 HOW NEW YORK TALKS TO LONDON 113

frequency. This desired side band having been isolated successive by modulation and filtering is now amplified by three power amplifiers, a 750- a watt, 15-kilowatt and, finally, a i5O-kilowatt unit. The output of this huge amplifier energizes the antenna system at Rocky Point, and about 100 kilowatts of power is radiated into the ether. The diagram on page 114 clearly explains the operation of the transmitter. The illustrations show the various instruments which accomplish these progressive steps. The picture on the first page shows the low-power parts of the transmitter. The two panels at the left comprise the speech input equipment, which is connected with the telephone circuit to New York. The operator is adjusting the volume by means of a potentiometer. These and the next panel include the two oscillators and filter systems which secure the desired lower side band between 55,800 and 58,500 cycles. At the right is the panel containing the low-power amplifiers, which increase the side band to the 75O-watt power level. The upper picture on this page shows the 15- kilowatt and the i5O-kilowatt amplifiers. The many fuses provide protection to the filament circuits. Above the fuses are a series of TWO AMPLIFIER UNITS plugs, through which the plate current Or the high-power section of the transmitter. of each tube may be measured. The

The of the are i and ratings amplifiers 5 kilowatts, panel shown in the center of the picture 150 kilowatts. A circular bank of water-cooled switches in timing and recording mech- tubes may be seen in the background. The posi- anisms means of which the tion of these amplifiers with relation to the rest by hours each of the equipment can be followed by referring to transmitter tube is used is automatic-

the on 1 picture diagram page 14 ally recorded. A close up view of a bank

of 1 5 water-cooled power amplifier tubes is shown in the middle of the carrier wave are varied in accordance picture on this page. Note the elaborate with the speech or music. In fact, if you water-cooling arrangement to the have a receiver which tunes with exceptional necessary dissipate heat generated the tubes. sharpness, you may have observed that by there are two places on the dial, extremely THE WATER-COOLED TUBES close together, at which you hear a station with maximum volume. These two mod- A LMOST as essential to transatlantic <* as the ulated waves are called the upper and lower telephony development of single side band are the side bands. In single side band transmis- transmission, high power water-cooled tubes. In the sion, only one of these side bands is radiated into the ether. accompanying picture of one of these

HOW THE TRANSMITTER WORKS DRIEFLY, the transmitter works some- ' what as follows: A telephone transmitter is used to secure an audio frequency current which is an electrical equivalent of the sound waves fed into it. For intelligible FIFTEEN WATER-COOLED TUBES conversation, a frequency band from 300 to On a circular are shown above. 3000 cycles in width is required. This is bank, The lower picture, to the shows used to modulate the output of a low power right, the telephone control board in the Gen- oscillator set to a second. 33,000 cycles The eral Post Office in Queen Victoria Street, output of this oscillator, when modulated London. It was from this point that British men by speech, has the usual two side bands, the newspaper recently spoke to their American brotherhood by means lower from 30,000 to 32,700 cycles and the of the transatlantic radiophone upper from 33,300 to 36,000 cycles. The next process is to pass this carrier and two side bands a filter e. through which sup- difference (i. 30,000 to 32,700 presses the upper side band. The lower is minus 88,500 or 55,800 to 58,500). now used to modulate the output of the The two side bands are so widely second oscillator working at a much higher separated that they are easily filt- frequency, 88,500 cycles. When two alter- ered. The lower side band, 55,800 nating currents are combined in this way, a to 58,500 cycles, is isolated by a carrier and two side bands are again pro- filter, and fed to a series of power duced. The upper side band is equal to amplifiers. the sum of the combined frequencies Up to this point, only feeble cur- e. (i. 30,000 to 32,700 plus 88,500 or 1 18,- rents have been used to produce 500 to 121,200) and the lower to their the single side band of the desired 114 RADIO BROADCAST

tubes, half of the plate has been cut voltage for test purposes, should it be re- away in order to reveal the rugged fila- quired. ment, which draws 750 watts, and also Considering that ten kilowatt broadcast- the grid controlling the electrons which ing stations are frequently heard in Europe, flow to the plate. The plate serves as it may seem surprising that 1 50 kilowatts the outside of the tube. This element of single side band transmission are re- cannot be sealed within a glass tube, as is quired for transoceanic telephony, espe- done with smaller tubes, because glass cially considering that the new method of would melt under the high temperatures transmission is four to six times as efficient generated by these huge power tubes. The as the old. But there are vast differences lower half of the tube is immersed in between occasional freak reception and the water circulated by a pump. Those parts of the tube Desk showing through the Telephonenc glass are the sup- ports for the elements, and conducting terminals for the grid and coooo filament connections. A consider- IZOOOO able length of hose (0000 is required to insu- late the plates of the tubes which are (the plates 90000 are, of course, elec-

trically connected eoooo to the water jackets)

at from 6000 to i o,- 70000 ooo volts above ground potential. 60000 The plate potential 50000 is secured through trans- high-voltage MOOD formers and rec- tified two-ele- by 30000 ment water-cooled

tubes. Perhaps the 20000 most difficult problem which had to (0000 be met in the design of these tubes was a method of sealing the copper plate to the glass in order to maintain the vacuum within the tubes throughout the range of temperatures encountered. THE RECEIVING APPARATUS

ONE of the accompany ing photographs IN may be seen the receiving apparatus, a highly efficient yet altogether unconven- tional unit. The amplification equipment necessary to convey the received matter to New York by wire line, is also shown in this illustration. The three units at the right comprise the radio receiving equipment, including the necessary oscillator which restores the carrier wave. The two panels at the left include the line amplifiers and the switchboard by which the correct line to New York is selected for conveying the received signal, and the necessary service wires for intercommunication purposes. At the far left is the testing equipment for the wire line circuit to permit undisturbed speech between the receiving point in Maine and in New York. The B batteries shown are used to secure an unfluctuating JUNE, 1926 HOW NEW YORK TALKS TO LONDON 115 THE NUCLEUS Of the whole transmitter consists of the water-cooled tubes, an example of which is here shown. The plate element has TRANS-ATLANTIC RADIO TELEPHONE TESTS TWO-WAY CONVERSATION been cut away to show the grid and filament which, or- dinarily, are hidden from view I Houlton, Me. Receiving Station r y^SSKc- 5770 meters ^ Bibliography on Single Side Band Transmission Peceivino/Stjtjw " Carrier Current Telephony and Telegraphy." Colpitts and Blackwell, ,,,-i--'-~5'lKc- 5260 meters Jonl. A. I. E. E., April, 1921. " Application to Radio of Wire Transmission Engineer- Rocky Point ing." Espenschied, Line -Direct Rodio Path idio Transmitting Dotted Proc. I. R. - E., October, 1922. Station Full Lin. Land Wire Path " - Relation of Carrier and PockyPoint Wroughton 3350 Miles Radio. Link Side Bands in Radio Transmis' -Houlton -2990Miles Rugby sion." R. L. Wroughton- London -90 Miles Hartley, Proc. I. R. London -65 Miles E., February, 1913. Wire Link -Rugby " Houlton -NewVbrk -GOO Miles Transatlantic Radio Tele- NewYork -Rocky (bint- 75 Miles phony." Arnold and Espenschied, Jonl. A.I.E.E., August, 1923. " Power Amplifiers in Trans- atlantic Radio Telephony." Oswald and Schilling, A BIRD S-EYE GLIMPSE OF THE ROUTE FOLLOWED BY THE RADIO WAVES Proc. I. R. E., June, 1925. "Transatlantic Radio Tele- As they hurtle from Rocky Point to England. Note the frequent repeater stations which are neces- phone Transmission." Espenschied, Arnold and sary to boost up the telephone conversations as they travel the wire lines. The main receiving sta- Bailey, Proc. I. R. E., February, 1916. tions, both in England and America, are some distance from the transmitters, but wire connecting "Production of Single Side lines enable persons at both Rugby and Rocky Point to listen-in to the conversations coming from Band Transmission." across the Atlantic Heising, (Del'd I. R. E., March 19, 1924)

to speak to someone in Europe, you need help to better mutual understanding; mu~ merely call the long distance operator and tual understanding means more tolerant A CLOSE-UP OF THE give her the usual information. It must adjustment of differences, and that, in the ANTENNA SYSTEM be born in mind that the tests were con- last analysis, means greater stability and Six towers, one of which ducted by engineers who have devoted more enduring peace. is shown below, support a six-wire The several years to the design and maintenance system. towers at Rocky Point of the experimental single side band trans- are 410 feet high and mitter. To be it commercially practical 1250 feet apart. They must be within the province and ability of lie in a north to south direction commercial personnel to maintain and operate the complex equipment. For ordinary messages of greeting, the apparatus of to-day is adequate, when conditions are favorable, but the commercial possibilities of transatlantic telephony will not be fully realized until the system is perfected to a degree that it can be used without flaw for business, news, and official conversations. This requires an adequate degree of secrecy, adding still further com- plications. Means have already been developed, however, for attaining the same degree of secrecy in radio transmission as is possible for wire communication. Un- doubtedly, this work can be successfully applied in single side band transmission. It is idle to speculate upon the possibilities of better human understanding which will follow widespread international telephone communication. Political divisions have grown larger in direct proportion to improvements in communication. Tribes cemented into nations when roads were built and when ships began to travel the seas. The telegraph and telephone has expanded nations to the size of continents. Perhaps the new influence of the radio telephone will play a vital part in cement- ing nations all over the earth into a single harmonious whole. The least that may be said is that international telephony will THE MARCH OF RADIO

Past President, Institute of Radio Engineers

How Crystal Frequency Control Works

'E HAVE seen and heard the B battery is connected with the tinfoil teristic tone, the same tone every time it much lately about frequency plates in the opposite sense, that is, battery is struck. This is called the characteristic control of a radio station by terminals are interchanged, the slab will vibration, or natural longitudinal vibration, it the rail. It will with the Wlmeans of crystals, but ap- shorten (where previously lengthened) of vary length parently the statements and descriptions and correspondingly grow thicker. of the rail, being a higher_note the shorter have been such that no simple idea of the The reverse of this process is also true. the rail. principle involved has been made. If the slab of quartz is stretched length- There are other modes of vibration for The two possible crystals to use for this wise, its tinfoil plates, now connected to a the rail, some of them pretty complicated. purpose are Rochelle Salt and quartz. sensitive voltmeter instead of to the B In the case of a small slab of quartz, there The peculiar property which these crystals battery, show that a charge has been are two principal natural vibrations, that possess has to do with their change of developed on them; the voltmeter deflects fixed by the length of the slab and that fixed shape when put into an electric field, such by an amount proportional to the stretch by its thickness. The natural vibration as that which exists between the plates of of the slab. If the slab is compressed rate (longitudinal) for a slab two inches a condenser in an operating radio set. lengthwise, the voltmeter again shows long, one inch wide and an eighth of an There are others of the so-called piezo- the development of a charge, but it is now inch thick is about 50,000 vibrations per electric crystals, but they show the effect in the reverse sense, that is, the voltmeter second; if the slab is only one inch long, the to a minor degree only. Quartz is really may deflect backward. natural vibration is about 100,000 per the only one available because Rochelle From what has been said, it is seen that second. The vibration fixed by the thick- Salt is so fragile. if an alternating voltage is applied to the ness of the quartz is generally much higher Imagine then a small plate of quartz tinfoil plates, the quartz slab will altern- than that fixed by its length. which has been properly cut from a quartz ately lengthen and shorten with the same The frequency of the natural vibrations crystal. If tinfoil is pasted on the two frequency as that with which the voltage of one of these pieces of quartz is remark- faces of the slab and these two pieces of alternates. Furthermore, this lengthening ably constant. Quartz seems to show no tinfoil are connected to a B battery, the and shortening of the slab will of itself fatigue, as do the metals, after vibrating slab may lengthen and become correspond- generate an alternating voltage on the a long time; neither has change of tem- ingly thinner. The amount of lengthening tinfoil plates. perature much effect on this frequency of is extremely small; it can be disclosed only Now, a small quartz slab acts just the vibration. In fact it seems as though the by the most accurate measurement. If same toward vibrations as a large metallic natural frequency of a piece of piezo- rod, such as a street car rail. Imagine electric quartz may be one of our funda- The photograph heading shows the antenna, masts and one of these is in the air a mental standards at station house of the Berlin broadcasting station at Witzleben. suspended by physical some future The tall tower is meters and the other 80. A 135 high couple of stirrups; if it is struck on the end date. duplicate station has already been erected at Munich. with a it will Cables connect the station with the studio in the city. hammer give out a charac- There are two or three ways of making JUNE, 1926 FUNDAMENTAL RADIO PATENTS IN LITIGATION 117

of these local stations. one of these pieces of quartz serve as a standards be set up and that in view of use The amateurs, from the would be would frequency standard for a radio station. the extra expense and usefulness of such whom band taken, still from 100 meters The simplest connection uses the quartz stations their channels be kept completely have their band down, stations further that in the grid circuit of a small tube, there free from interference. The local he says. He predicts they being a suitable coil in the plate circuit. will in general send out material of would "cheerfully give up the 150 to 200 to service Between the grid and filament connection especial interest to those in its vicinity; meter band the greater of the there is a small condenser-like arrangement, the amount of power required is small public as a whole." Now such a sug- in from a say such as would be made by using two and as a result many such stations, gestion should come committee nickels held about one sixteenth of an inch Senator Dill's opinion, could operate on of technical experts, not from a legislator, confesses to and furthermore would. like to hear apart. Between the two nickels a small the same wavelength. He we quartz slab is placed, and when proper no expert knowledge on the question but from the amateurs themselves rather than filament current and plate voltage are speaks from the point of view of an enthusi- to take Senator Dill's prediction of their applied to the tube, it oscillates at a astic fan. The wave band from 1 500 kc. to feeling in the matter. frequency fixed by the natural mechanical loyikc. (200 to 280 meters), he says, is at Even should the broadcast band be vibration frequency of the quartz slab. present practically useless because of the extended to as high as 2000 kilocycles (150 If the piece of quartz is not a very good interference between the many class A meters), most of the receivers on the market would be useless for them. piece (piezo-electrically), the plate circuit, stations operating within these frequency today receiving should have a condenser in parallel with limits. It is interesting to observe that Senator its coil and the plate circuit tuned to a One of his suggested remedies is to put Dill's idea regarding the division of stations frequency approximately the same as the all the local stations on a very few channels; into the two classes mentioned above is natural mechanical frequency of the by limiting the amount of power allowed already working itself out. A few of the quartz. The quartz, however, and not the to such stations (and possibly materially stations of the class of WEAF, wjz, WGY, tuned plate circuit, will fix the frequency decreasing the number of such stations) he KDKA, and similar ones are rapidly becom- of oscillation. The small crystal-controlled feels that three or four channels should ing known among listeners as national tube is used to excite a larger one which suffice for all the local stations in the coun- stations whether they are so legislated or in turn may directly control the station try. Such a scheme certainly could not not. We certainly agree with Senator frequency. The final power controlled be put into successful operation to-day with Dill that whatever change may be made in may be measured in kilowatts, but the the present number of such stations, as long frequency allocation, the channels of these frequency of this great amount of power as they use the reasonably high powers high class stations should never be en- is being controlled, to perhaps one part in which they do. croached upon; in fact, any move to change a million, by a piece of quartz about the Senator Dill then recommends that the conditions in this lower part of the fre- size of a quarter. wave band from 2000 kc. to 1500 kc. (150 to quency band should be to pull out the un- 200 meters) should be taken over for the desirable stations rather than add new ones. Pending Radio Legislation

THE radio legislation awaits definite action by Congress we ASbegin to wonder if the present year's activity in getting bills formulated and under way is to be as futile as was last year's. Surely Congress can see that the regulations of 1912 are insufficient to deal with the present situation and that there is a real and insistent demand for some regulation which can take care of to-day's difficulties. The Secretary of Commerce, capable as may be the present incumbent of that office, is practically helpless when confronted by an important radio question. Congress is not performing its required function if it leaves Secretary Hoover with his present severely limited power in radio matters. Senator Dill recently gave an interview in which he expressed some interesting and some rather drastic ideas. He says:

The question has arisen during our consideration of the bill as to whether the regulation of radio should be entrusted to the Secretary of Commerce, or to any other one man. It is my belief that at the present stage of development the details of administration should remain with the Department of Commerce, but that a non- partisan commission should be established with authority to pass finally upon questions which may be referred to it by the Secretary of Com- merce or any one else. The decisions of this commission should, of course, be subject to review by the courts.

He goes on to suggest a new division of stations, according to their power into INSTALLING AN ANTENNA IN WINNIPEG, MANITOBA "national" and "local." He recommends The local telephone company grants the right to use a telephone pole that for the national stations most rigid for $6 a year and their linemen erect the antenna for a small sum 118 RADIO BROADCAST JUNE, 1926

Important Radio Patents at for the Radio Corporation, showed ex- special achievement acclaimed being the to that it was invention of the transmission of Present in Litigation periments prove operative. alleged The court has the two demonstrations to ultra-audible sound waves through water. consider in rendering its opinion. The By ultra-audible was meant sound waves are at present being tried in decision in this case will probably be with- so high in frequency as to be the the courts, several of the important beyond THERE held until other evidence is before the court. human hearing. radio patents, the decisions on which The Hazeltine Corporation has haled the Some of the marvellous features of these may very materially affect the radio A. H. Grebe into court and that sound waves brought two or three columns business. The Armstrong idea of regener- Company case is now under way. The Grebe of newspaper comment. The fact that ation, insofar as it relates to oscillating " "Synchrophase, it is claimed, is a neu- they are inaudible and to that extent secret, tubes, is being contested by the government tralized set which the Hazeltine that be made to travel in in a suit in the state of Delaware. Arm- infringes they may straight patents. The Grebe claims it does lines instead of in all directions strong's priority over other inventors Company scattering not at in force. as does sound, and others of apparently depends altogether upon a infringe any patent present ordinary many The validity of the negative C its remarkable characteristics were lauded sketch of a supposedly regenerative circuit, battery and the grid leak patents is also soon to be as the discoveries of the Research Labor- which was accompanied by practically no tested out in court. The C staff. explanatory disclosure. Should this sketch battery patent, atory from Lowenstein the A. T. & T. That is not the fact and we this be proved by the government's experts to bought by publish and the leak statement of fact in fairness to those who be no true disclosure of the regenerative Company, grid patent, granted to are both controlled did the work. the a principle, there is a possibility that the Langmuir, During war, group in the radio field the Radio of from Columbia Westinghouse Company may lose one of its by Corporation, scientists, principally and the Grebe has been selected was the of most valuable radio patents. Company University, assigned problem the R. C. A. as defendant in these suits. ultra-audible sound and in the files The Radio Corporation has just finished by Navy Another that of a suit in the Federal Court of Brooklyn patent, Mathes, in which are complete accounts of all the prop- the is held the erties as against one of the Hazeltine licensees. The grid negative by voltage drop now hailed inventions of the Naval due to filament current a Research Garod Company was the defendant in the flowing through Laboratory. resistance, is also involved in this suit. Those scientists suit, but the Hazeltine Corporation under- were sworn to secrecy The above four or five took the defense of its licensee and Hazel- patents mentioned by the Naval authorities on all the work as at in come near had tine himself served as expert for the Garod present litigation very they done, otherwise the scientific to basic in radio Company. The Radio Corporation based being patents apparatus journals would have received clear and as it exists its suit on its possession of the Rice and to-day. authentic reports of this most fascinating Hartley patents, both of which it controls. branch of acoustics. If the Naval Research They attempted to show infringement by Something About "Supersonics" Laboratory wants the Garod Company. to make more discoveries on the action of Hazeltine showed experiments to prove purported to be an inter- sound of this nature (up to 200,000 vi- to the court that the Hartley patent was view with Dr. H. C. Hayes of the brations a second) it would do well to con- practically inoperative for the circuits used WHATNaval Experimental and Research sult the files of the Navy Department for in broadcast reception. After he had Laboratory at Bellevue, on the Potomac the years 1917-18. The most remarkable his of these completed tests, Waterman, an expert River, was featured a short time ago, the properties supersonic soundbeams, as given in the reports mentioned above, have not yet been made public in so far as we know.

What About Libel by Radio?

ARE all of us very adverse to a censorship of radio channels WEfreedom of is one of the speech foundation stones of our Constitution and any measure which threatens to encroach on this feature of American liberty at once arouses our antagonism. But a situation has now arisen which demands some analysis and action and when the probable legislation is passed we shall again be reminded that "liberty" as our radical element interprets it, isn't quite the same thing as most of us take it to be. While the Constitution grants to each of us liberty of speech and action that liberty is guaranteed in so far as the speech and action do not interfere with the rights of others. The rights of others are generally overlooked by those who insist upon complete liberty for themselves. In our country it is a crime to write libellous matter and it is punishable by fines and imprisonment. This is as it should be. We are at liberty to write only that which does not PART OF THE NAVAL RESEARCH LABORATORY AFLOAT interfere with the rights of others. The Sound barges on the near spoken word, however, is generally Potomac, Washington, where experiments are in progress designed to the super-sonic for undersea not a cause of action for slander the telephone communication. As Professor Morecroft points out, much research on sound waves was carried out slanderous super-audible by Columbia University experi- remarks must be written. The menters and others, the recent war during reason for this distinction is evident when JUNE, 1926 NEED FOR A LAW TO COVER LIBEL BY RADIO 119 one considers how difficult it would be to the alleged slanderer are apparently beyond Broadcasters Association gives us the prove conclusively what a man said. What the grasp of the law. unexpected news that some stations are a man has written, however, is there for When one considers the future and at present being charged royalties of more the judge and jury to see for themselves. possible increase in censorship at our radio than $25,000 in one year! How about slanderous remarks spread stations it becomes ever more evident that over the radio channels of the country? we must guard against a possible monop- Can the Voice be Carried on Does the man have no redress of the radio broadcast service. If injured legal oly Light Beams? if his reputation is besmirched in the hear- the station owner is allowed to censor ing of a million of his countrymen? Evi- what shall and shall not be sent out over to a news dispatch dently here some new regulation is required his channel, a combine of stations might A;CORDINGfrom Birmingham, Alabama, it and it looks as though it might soon be become a dangerous factor in controlling seems as though radio waves may forthcoming. Representative Blanton of a country's news. A monopoly of radio be somewhat affected when they travel Texas proposed an amendment to the channels is not to be put in the same class through a beam of light. Some experi- White Bill which makes it a crime to utter with the wire telephone monopoly of the menters were manipulating a huge search- scandalous remarks over a radio channel. A. T. & T. Company. Such, we believe, light on the top of a high building and This, the House did not incorporate in functions for the direct benefit of the Amer- apparently their voices were carried to some the final form which reached the Senate. ican public, but a broadcast monopoly of the radio antennas in the neighborhood. According to the Blanton amendment any would be a bird of entirely different hue. The report states that engineers of the person who utters a libel or scandal by General Electric Company are investi- radio may be prosecuted either in the state Fees For Broadcast Music Should gating the phenomenon to see if the effect from which it was broadcast or in any state be Fixed is a real one and if so how it can be con- where it was received. trolled. A court in Oklahoma City already has a to the National As- There may be a real effect to be found; case before an action to which the sociation of some it has been known for a time that an it, A1CORDING Broadcasters, long Blanton amendment would apply. Station radio stations are being charged arc, such as is used in searchlights, could KFJF, operated by the National Radio extravagant figures for the privilege of reproduce the human voice with a remark- Company of Oklahoma City is in trouble broadcasting copyrighted music. Legisla- able degree of fidelity. If the current from because the pastor of a local church de- tion at present under consideration will a radio receiver is passed through an arc clared over this radio channel that Sheriff compel the broadcasting station to pay light, which is already burning from the Friss had accepted a bribe not to en- a statutory fee every time a copyrighted current supplied by a continuous-current force the Prohibition Law. The pastor number is sent out, but nevertheless this generator, the arc will act as a very good is sued for $55,000 and the radio com- legislation has the support of the broad- loud speaker. (Of course precautions have pany for $20,000 in the libel action of casters' association. This support is based to be taken not to burn up the radio set). the sheriff. As the law stands, the sheriff's on the theory that whatever tax the new If then this effect is a reversible one, action probably cannot be sustained, but law provides, the broadcaster will at least which seems very likely, voices in the with the proposed amendment in effect, know what the performance is going to vicinity of the arc will vary the intensity the minister would have to prove his cost him. The station manager needs to of the light beam in a manner corresponding assertion or be adjudged liable for damages. devote perhaps ninety per cent, of his to the sound waves. If, then, a beam of It has not yet been defined legally as to program to music, so that music they must light does affect the radio waves traversing what extent the radio station is liable for have. The statement of the National it, we could expect the voice of the arc the material sent out over its channels, but if the Blanton amendment becomes operative the law may make it a co-defendant with the scandal-dispensing speaker. This will make more necessary the precaution which most stations take at present to have their speakers read, from a written copy, whatever they have to say. Someone must have previously read over the copy and the station operator must check what actually goes out over his channels with the copy beforehand. If material departures are made by the speaker, the operator can shut off the microphone until the speaker comes back again to the material which he was supposed to send out. Since the above was written the Okla- homa court has dismissed the Friss case, the lawyer for the defense putting up the plausible argument that the radio station was no more liable for scandal sent over its channel than was the telephone company for permitting a scandal to travel over its wires connecting the speaker's microphone to the radio station. With the law as it exists at present, the dismissal of the suit was a foregone con- clusion; courts are to see that the laws Barratt's of the land are obeyed, but it is not their A CORNER OF THE GENERAL POST OFFICE RADIO LONDON function to apply old laws to new and ROOM, The photograph shows some of the automatic Wheatstone transmitters in use. The circuits unforeseen circumstances. New regulations tape here are London-Halifax, which is carried out on long waves via Leafield (Oxford), and Egypt. The must be passed to meet new conditions and operator is checking the signals as they leave the transmitting antenna many miles away, through until the radio station owner and they are, the loud speaker at the right JUNE, 1926 120 RADIO BROADCAST

for other interior cities, money is provided three new radio test trucks. With the additional inspectors provided for, it is can be anticipated that much closer watch to kept on the broadcast channels help eliminate avoidable interference.

The Month In Rddio

award of a medal for "conspicuous ser- THEvice" with a selection committee composed of well known names in the world of science and our excel- public affairs has been announced by lent contemporary, Popular Radio. Their announcement states that "it shall be awarded without discrimination to all amateurs men, women or children, of any race, nationality, color, or creed through whose prompt and effi- W. G. CADY HIRAM PERCY MAXIM cient action radio is utilized to perform an essen- shall be tial part in rescue work. The awards Middletown, Connecticut- Connecticut; President Hartford, restricted to non-professionals only." Commu- Professor of Physics, Wesleyan University of American Radio and Relay League, nications should be addressed to Dr. E. E. Free, (Especially written for RADIO BROADCAST) of International Amateur Radio Union of Radio, " Secretary, Committee Awards, Popular The oscillator plays the same part in the written (or RADIO BROADCAST) (Especially West 43rd Street, New York City. transmitter that a does to a dock. " 627 pendulum The broadcast listener thinks he has had a It determines the wavelength of the station thrill when be bears the announcer of a distant in trans- IMPORTANT change Navy where it is used. The reason for using the letters and what the station give his call say been at the it makes ANmitter practice has inaugurated crystal as the master oscillator is that next number of a program is to be. But it Great Lakes. The use Naval Training Station, a very much more constant frequency possible isn't thrill at all to what the will be any compared of the thirty-kilowatt arc transmitter, than could he assured without it. The fading amateur when communicating enjoys all the traffic will be handled so two-way discontinued and of radio signals which amateurs find he works back and forth and holds two-way a by a new triode outfit, generating frequency troublesome is due, in part, to the fact that the That's communication with the antipodes. If the use of not of 8630 kilocycles (34 meters). wavelength of the broadcasting station is the thrill. And, that's the real office of as re- big this high-frequency transmitter proves constant but varies slightly. The quart{ radio. Listening is not even half of the game. the arc oscillator liable as is now anticipated, oscillator entirely does away with the varia- into the amateur trans- "Anybody can get will dismantled. be permanently bility of wavelength. the code is no mitting game. Learning Lakes station is the first of the This Great "Experiments with the crystals were begun i's an stumbling block. On the contrary, it to on it Navy outfits rely solely high frequency; in wartime when they were used in connection is secured. The easy thing if a little help in this work and so has been a pioneer really with the detection of submarines. A crystal brotherhood communicating great of two-way deserves the honor of showing the other Navy which was mounted in a suitable case was amateurs all over the world, is ready and stations the way. and when it was connected with an hand submerged, anxious to help and to extend the warm effected communication with the This station electrical source it sent out a beam of high- of welcome. U. S. S. Seattle when this vessel was in Honolulu frequency sound which came back as an echo "There is a country in the world the station hardly harbor last summer, and also this was submarine which happened to be amateurs. from any where there are no transmitting which in touch with Commander MacMil- kept in the neighborhood. The echo was received In North America, we amateurs have our of Green- lan when he was on the northern end on the same that sent out the sound. in crystal American Radio Relay League, and foreign a All of that official land almost year ago. Navy "There are various circuits for quart; our International Amateur countries we have traffic was handled this station. through crystals in connection with vacuum tubes. Radio Union. Our amateur transmitting months schedules of For the last few daily Some these are circuits for on a world-wide of oscillating brotherhood is organised traffic with have been carried out Washington stations, while others are for the national and transmitting basis, and is fast building up with various It was found that frequencies. purpose of using the crystals as frequency international that are of very well or friendships 8630 kilocycles carried equally day night standards wavemeters and indeed." for calibrating great value so that was chosen as the official frequency. other measurements in the radio laboratory."

operator to be heard in nearby radio Interesting Things SCHUMANN-HEINK (New York; receivers. Whether this possible effect MME. I Said Interestingly opera and concert singer): "When sang is a real one, the engineers working at the over the radio in New York the other day, my task will soon let us know. son, who is one of my most intelligent and to the radio /CORDON C. SLEEPER (New York; Presi- severest critics, listened-in analyze Increased Radio for ^-^ of voice. He told me after- Appropriation dent, Sleeper Radio Corporation): "Only reproduction my ward that he had heard me breathe in the of Commerce a comparatively few firms, suffering from unwise actually Department it 1 was horrified, for is an unforgiv- overproduction, have been guilty of the practice singing. of the in- able sin for a to let her breathing be RECOGNITION great of 'jumping' accompanied by slashing price singer heard. crease of work loaded on the Radio reductions, and the sooner they pass out of exis- IN could not have been Supervision Service of the government, tence the better for everyone concerned. Rep- "Now, my breathing the interests of the heard the keenest ear of an observer sitting Congress has increased the funds available utable companies having by radio business at heart and themselves desiring in the first row of the orchestra. The micro- for that service by about fifty per cent. a inches from me as I to continue in it, have not and will not tolerate phone was only few sang, over what it was last year. The budget and their good work in maintain- and it therefore caught the slightest vibration. for this but this price cutting, allowed $354,000 work, radio hundreds or ing standards will be especially evident during In other words, my audience, has been cut to $335,000. Even so, it is of miles heard me as this year. thousands away, though more than was for the " I $115,000 provided Radio has by no means even approached the they were standing a few inches from me as Besides a wonderful to present year's operation. opening sales saturation point, but 1 feel confident that sang. This gives radio advantage additional sub-offices in Dallas, Memphis, the next twelve months will see that condition hear the finest shading of tones and the details Los Angeles, Pittsburgh, and half a dozen nearer in sight." of the singer's technique." The ist Lab" Circuit

New Applications for the Toroid Coil -Another Experimental Article Introducing a Circuit of High Qain, Sound Design, and Unusual Efficiency Another Fascination for the Home Experimenter By KEITH HENNEY Director, Radio Broadcast Laboratory

THE average home end of a set. But many people experimenter who pos- believe that the radio fre- article is which describe a circuit which has sesses a laboratory of the first of a series quency part of receivers is a known and used in various a number in- sorts, there appear to fragmentary forms by of closed book. vestigators. The original circuit is probably due to Dr. L. M. Hull. Bells be two possible directions in If the home experimenter and others of the Western Electric Company have also contributed much. A which his energies may be will look over the radio writ- great deal of development and research, covering many months, has been done spent. Either he conducts ex- ings of the last few months in RADIO BROADCAST Laboratory, and in the form in which the circuit is for their own sake, which is a idea in it- periments now presented in this series, we believe confidently that the radio constructor good or he works at small self he will find considerable many will find a circuit which has more to offer than -rmy-design presented to him tasks, with the completed since the introduction of RADIO BROADCAST'S famous Roberts circuit. For mention of toroid coils, and he whole a receiver, let us say efficiency and that term is not used idly it will be difficult to find any home may wonder if all the conflict- in mind. constructor's circuit which can compare with it. This article presents the ing statements are correct. the circuit and describes several models which Suppose, then, that you are experimental background of Probably, if he has been inter- can be built. Later articles will show how to build a number such an enthusiast to whom the exactly of ested in radio for any length of models which are decidedly worth waiting for. We present here enough series of articles appearing in time, he. will know that the material to keep the true home experimenter busy for some time to come. this for home ex- toroid is not a new but magazine THE EDITOR. idea, perimenters has appealed. ^^^^ that coils of this nature have *^ E -VS?> The experiments related so far been employed in the telephone have been for their own sake, industry for years. Its migra- although the apparatus described has been tion into the field of radio frequencies was such that many applications exist for it. thought of by many people witness the Suppose that you wish to design a new fact that a good half-dozen appeared on the receiver. In what direction will you market practically simultaneously. And turn? the experimenter will find that some of the The home experimenter, having decided articles, written evidently by people who Output that he wishes to design a new receiver, know, state that the toroid has no business will not depart from the general rule, in the radio industry. which is that he likes to see concrete results To dispute the right of the toroid coil of his day's work. He does not wish to to a place in the radio sun requires that into a blind blunder alley. He proceeds FIG. I the complainant have a clear picture of with caution. and this The fundamental unit around which every radio what he asks of a coil, upon point Radio, as he looks at it, seems to be like receiver is built. A coil and a condenser will many people seem to have hazy ideas. have considerable across it when a blackboard upon which new ideas are voltage properly The experimenter will sit down and draw tuned, and this voltage when applied to the input written daily, and as often erased. Some a picture of the fundamental radio circuit, of an amplifier will be considerably augmented. of the ideas are few of them are new. coil and a condenser with their terminals good, The extent of the amplification depends upon a And up in the corner of the blackboard the inductance and resistance of the coil connected together. He will attach to marked "do not erase" are the tried and these terminals, the grid and filament of true schemes that have come down in I . will through engineering field. His reasoning will prob- a vacuum tube, as shown Fig. He the of radio. The elimination stormy days ably be something like the following. note that he has the input circuit of a high of the the tuned radio super-heterodyne, Practically all new ideas that radio frequency amplifier. What he wants, then, frequency amplifier, the regenerative de- schemers have are due to the desire to im- is to find out the relation between the tector is not Further than expected. that, prove either the quality of reproduction what can one say? or the selectivity and sensitivity of the The home reasons experimenter, then, radio frequency part of their receivers. that he needs a new and he knows idea, Present day high quality transformers, the beforehand that he will not stumble likely use of properly constructed and operated that will over- upon something completely resistance amplifiers, the introduction of throw conditions in the radio existing semi-power tubes and the general application of cone speakers of high quality leave little to be expected from the low frequency

FIG. 2 the source of their their names differ too. The first is These circuits are all the same, drawn differently and depending upon popularity, " and the third is the so-called circuif the original Hull circuit appearing in QST, the second is the newspaper and Radio version, Bridge" 122 RADIO BROADCAST JUNE, 1926

.00025 mfd.

RADIO BROADCAST Photograph FIG. 3 Three methods of introducing voltages into toroid coils. One, Bremer- Tully, uses an extra coil placed inside the toroid proper, N'axon uses turns placed outside the toroid, and the Radio Foundation coils have an FIG. 4 external coupling coil A toroid receiver circuit which uses no additional coupling coils but which utilizes part of the detector coil to introduce energy into the detector circuit. A similar was used in amplification he can get from this combina- Thus the experi- system the RADIO BROADCAST "Universal" receiver tion of gear and the kind of coil he uses. menter may see that the difference in gain THE GAIN IN R. F. AMPLIFIER COILS between the best solenoid and the average it is difficult to get energy into the coil. CORTUNATELY the business of de- toroid is not so great as many would like For this reason, a circuit in the neighbor- * termining the effect of using a good or to prove, and when one couples this fact hood of powerful broadcasters is not so bad coil has been done for the experimenter with many of the other advantages of the likely to be disturbed by local signals ex- and the work described in RADIO BROAD- toroid he will see that there are few difficul- cept those arriving at the receiver through CAST many months ago by Harry A. ties in the path of a good toroid receiver. the proper means the antenna. The Diamond, in April, 1925. This nice piece of These difficulties, however, exist and the fact that the field is restricted indicates research was performer! by H. T. Friis and experimenter should not fall into the error that the coils may be placed closer to metal A. G. Jensen of the Bell Technical Labora- of jamming a toroid into any existing cir- end plates of condensers, closer to wires tories, and has been generally neglected cuit with the assumption that it will work carrying radio frequency currents of wrong by many experimenters and writers. phases, and even In this paper, the fact is demonstrated closer to each other that the voltage gain of such a coil-con- without the many denser combination is a function of the troubles incident to inductance of the coil and the square root inter-stage coupling. of the resistance of the circuit. Since The use of toroids most of the resistance exists in the coil, it makes possible the behooves the experimenter to reduce the conservation of space, resistance as much as possible but this the maintainance of factor is not so important as many writers the resistance of cir- would have us believe. In fact, the cuits at their lowest statement that toroid coils are less efficient point, the reduction FIG. " " than solenoids need not bother the builder 5 of " " pick-up from ex- These drawings show how the H ull and the Universal systems of good receivers at all, for the difference ternal sources, the differ. In the Hull circuit, the coil has been reversed in gain between a toroid coil amplifier and plate prevention of inter- one using a solenoid of the lowest resis- stage coupling by- tance will not be audible to the human ear. properly. It can't be done. This article stray electromagnetic fields, and naturally If the experimenter is equipped, he can and those soon to follow will show how the makes neutralization of high-gain amplifiers perform the illuminating experiments him- toroid can be used in a circuit whose per- a much simpler problem. All of these self of determining what voltage amplifi- formance is astounding. things are possible, of course, provided that cation he may secure, but he may also use proper precautions are taken, and provided USE AND ADVANTAGES OF THE TORIOD COIL Friis and Jensen's formula to do the same that the experimenter does not play with an thing. These engineers state that the great advantage of the toroid coil inherently unstable or unbalanced circuit. maximum voltage amplification possible THElies in its restricted field. This means Now for a little history. In the Jan- is as follows: that energy from the coil is not likely to uary, 1924, QST, Dr. L. M. Hull described (A L X 2 */ expand about the coil itself and interlink a circuit that promised considerable vol- _~ X 2 with other fields, and by the same token tage amplification. It was brought to the V RP x R where Rp is the tube impedance V- is the tube amplification factor R is the resistance of the circuit L is the inductance of the coil f is the frequency He should use this formula and the data below, which are for two types of coils taken from Sylvan Harris's article in Radio News for January. = Rp 12,000 ohms (2OI-A) 1* 8 R = 10.3 (solenoid) 1 8.8 (toroid) = f i ooo kilocycles BROADCAST Photograph L = 300 microhenries. = FIG. K (toroid) 17 " = An experimental set-up of the Bridge circuit." Coils of small dia- (solenoid) 20 meter are recommended in order that their external field will be small LAB" CIRCUIT 123 JUNE, 1926 THE "RADIO BROADCAST attention of several radio experimenters with the result that the circuit is now R. F. Choke variously used and variously named. It has come to the Laboratory in many guises, among them being the "Belts" circuit, the Western Electric Bridge circuit, the R. F. L. circuit, and on the Pacific coast it is probably known as the Best circuit. Fig. 2 is a compilation of several of these circuits, including Doctor Hull's original scheme shown in QST. Although many have claimed credit for connecting an amplifier-detector coil as Doctor Hull has done, it is believed that he should get whatever glory there is in it. The circuits in this Figure are really all the same thing, drawn differently. Although the Hull circuit was not orig- it has inally designed for toroid coils, lent itself to their use with peculiar effec- The chief trouble with toroids tiveness. FIG. 7 at is that few seem to know present people The Toroid Receiver circuit containing all the modifications to bring all previous circuits up to date. how to get energy into them without This circuit employs the Rice system of neutralization, condenser feed-back to introduce regeneration and an condenser in the detector coil so that a. c. be to spoiling all of their good qualities. Fig. into the detector, isolating may employed The conven- light the amplifier filament 3 shows several methods. tional inductive coupling with external coupling coil is bad since it introduces receiver is to determine the correct place In- large capacity and resistance losses. to tap the toroid coil. This problem inductive coupling by means of a separate volves a knowledge of the input impedance in Type Tube plate coil is not so good since it results of the detector tube and the output im- two fields, a strong one due to the tuned pedance of the amplifier tube, the number circuit and a weak one due to the plate of turns on the coil, the inductance of the circuit. Neither of these coils are complete coil, and the frequencies to be received. toroids and naturally the field is not so Considerable work was done by the wri- constricted as one wishes. ter in RADIO BROADCAST Laboratory and be used. In Fig. 4 is a circuit which may Cruft Laboratory at Harvard to determine There is but one intertube coil which is a the proper turn ratios, and the data below induc- complete toroid tapped for the plate is based on the empirical formula that the tance. If this system is used, the ordin- correct ratio between the grid and plate ary Hazeltine method of neutralization can coils is as follows. not be used and other resources must be drawn upon. is contrasted In Fig. 5, the Hull method with the circuit of Fig. 4. It will be noted that there is little difference between the two circuits. In the Hull method, the plate coil has been reversed. Although they look much alike, there are certain structural advantages of the second which make it worth while. In the first place, a condenser may be used to isolate 'the plate and grid coils as far as d. c. and low frequency a. c. are concerned. This makes it possible to light the filament of the first tube from a. c. In the second case, the Hull arrangement makes it possible to add regeneration to the detector without extra coils. In other words, the toroid coil receiver which can most successfully be operated is a stage of radio-frequency amplification added to a regenerative detector the heart of the "Aristocrat," the Roberts, the Browning-Drake etc. The first coil may be a loop, a solenoid, a toroid or any type of inductance, while the amplifier- detector coupling is a toroid of only one winding. WHERE TO TAP THE COIL

question of greatest importance THEat this stage of the home experimentei 's departure upon the development of a new 124 RADIO BROADCAST JUNE, 1926

Important Facts Concerning the Circuit-

of Receiver Circuit Circvit Origin 1 stage tuned neutralized radio-frequency high Hull; Bell Telephone Laboratory Engineers gain amplifier, regenerative detector. Coils Toroids, solenoids, diamond weave, etc. sat- Audio Any Amplifier isfactpry tuner coil may be used in the antenna Any good type of audio amplifier may be con- circuit. nected to the detector output. Tubes 199's or 20lA's satisfactory. Neutralization Parts Rice Required 2 sockets, 2 coils, 2 tuning condensers, 1 feedback condenser, 1 neutralizing condenser, 1 filament Regeneration control, 1 output jack, 1 isolating condenser, 2 Capacity Feedback choke coils, 1 grid leak and condenser. FIG. IO The size of the tuning condensers employed will depend entirely upon the size of the coils used. The standard commercial coils usually take a .0005-mfd tuning condenser. The isolating condenser is 0.5-mfd One method of making a trap for the amplifier and the grid condenser .00025-mfd. A 15-plate midget condenser is satisfactory for regeneration and a neutralizing condenser of the three-plate type is suitable for use in the circuit. circuit. Sufficient wire is wound on the grid leak tube to tune to the offending frequency with th .ooo25-mfd condenser. A nail placed inside the tube broadens the tuning sufficienctly so thai the number of turns is not critical mu tube requires that there be practically thrills. As an adventure into circuit build- as many turns in the plate coil as in the grid ing, it is strongly recommended. For the coil to get maximum amplification which reader, however, who wants a set he can by-pass condenser across the B batterie: and if all leads are short al will be somewhat greater than with a low build with the certainty that it will work and direct and least a i.o-mfd is impedance tube such as 2OI-A and the easily and surely, it cannot be recom- condenser across the B selectivity will suffer accordingly. mended. battery, it may not be necessary. Fig. 6 is an experimental model of the It is better, however, to include this con- EXPERIMENTING WITH THE CIRCUIT "bridge" circuit built in the RADIO BROAD- denser, which may be as small as o.i-mfc at the coil terminals so itsel! CAST Laboratory to determine whether the home experimenter is encouraged that the coil circuit was practical or not. The diagram THEto try the "Bridge" circuit and then is as nearly complete as possible. The tun- of connections is in 2. It will to condenser is across the entire given Fig. progress to that shown in Fig. 7, the ing placed coil and be noted that the amplifier is neutralized ideal form. It has all of the advantages only part of the voltage developec by tapping into the interstage coil. This of which toroids are capable and few of the is applied to the grid. This represents a scheme represents a circuit that will work disadvantages. Neutralization is effected slight loss which is not noticeable, especially and in nearly every case it will be excep- by the Rice method which makes the am- since regeneration is used in this circuit. The radio tionally sharp and with considerable sen- plifier practically independent of the de- frequency choke may be There is the wound of small wire in slots in an sitivity. difficulty, however, tector circuit. With low loss coils, proper insulating it form as shown in that cannot be neutralized unless every- spacing of wires carrying radio frequency the February RADIC in is BROADCAST on or it 2 thing the circuit placed properly and currents, and shielding if necessary, an am- page 443 may be is of the on which about turns of correct value. The amplifier plifier with a large voltage gain will result. spool 400 No. 32 tends to insulated wire are In the oscillate until the detector is There are many interesting points about wound. Labora- turned to it when enough energy is ex- the circuit that are worthy of discussion. tory, choke coils have been wound with the wire from an old coil. tracted to stop oscillations. In other Considering the detector inductance, it is spark Coil; words, the set tends to "lock" into the fre- seen that it consists of a coil which has been which may be used are manufactured b> that is the Samson Electric quency desired and other signals physically divided into two parts which Company, and one is shown in have great difficulty in breaking through are connected together, as far as radio Fig. 6. the two tuned circuits. frequency currents are concerned, by a The condenser connecting the plate ol the The receiver whose circuit is shown in large by-pass condenser. This condenser detector tube with the lower end of the detector Fig. 2 will give any home constructor many has the same position in the circuit as the coil may be any of the smal "junior" condensers now on the market The maximum capacity depends upon the size of the choke coil and it must be large enough so that the detector will oscillate on the lowest frequency (longest wavelength) that is to be received. If the choke is very large, a smaller feed-back condensei may be used. If the choke and condensei are too small, tuning somewhere in the broadcast frequency band, erratic results will be obtained. It may cause the detector to oscillate at some frequencies and not at others, or it may be necessary tc introduce more capacity to stop the detector from oscillating. Fig. 8 shows a complete receiver using two toroid coils. Fig. 9 shows a Laboratory model oi this receiver in which is used a choke coil wound of 400 turns of No. 36 enameled wire on an ordinary cotton thread spool. Regen- eration is smooth and quiet in this circuit. The wire which connects the plate of the RADIO BROADCAST Photograph detector to this condenser is "hot" and it FIG. 9 must be from other wires This receiver uses kept away Samson condensers which make a compact receiver possible, an All American toroid and carrying radio frequency energy. a Superaudioformer. It is a complete three-tube set on a baseboard 6 by 12 inches. Note The Rice of the condenser which connects the two parts of the detector coil as well as the copper shield system neutralization is between the antenna coil and the toroid employed, making the amplifier and de- JUNE, 1926 THE "RADIO BROADCAST LAB" CIRCUIT 125

lector circuits practically identical with of the coil. These You Don't Know About Tour R. F. regard to the placing of inductances and wires are twisted, con- Something Amplifier the a capacities. The center tap on antenna stituting condenser, SPEAKING of radio-frequency amplifier circuits, which use IN inductance must be within one or two until the proper capac- Rice neutralization, Mr. Henney analyzes a peculiar, phenom- turns of the center if exact neutralization is ity is found. enon, which, to our knowledge, has never before been suggested. to be attained. Another method con- "// the receiver seems to be inoperative, no signals coming through, or the seems to oscillate without to the The isolating condenser and the tuning sists in removing the if amplifier regard neutralising condenser, or if a platf meter shows that the first tube is taking a condenser of the detector circuit must be "works" from a grid large plate current, this tube is probably oscillating at a very high frequency. well insulated, or the batteries will be leak and winding about This frequency is usually in the neighborhood of 3748 kc. (80 shorted if the condenser shorts. The loo turns on the glass meters), and is controlled by the "leakage" inductance of the coil and same be said of the neutralizing con- tube. This inductance may the capacities attached to it. What actually happens is the following. denser of the which should be is then into a amplifier, slipped The tuning condenser is practically a short circuit for the very high fixed at the proper point and not varied .ooo25-mfd. condenser frequencies. In other words, the coil is an inductance with its two ends as is common on many receivers now in use. with grid leak mount- connected together. If the coupling between the two halves of the coil were ings and wire removed perfect, the resultant inductance when the ends were A NEW ANALYSIS OF TROUBLE IN THE R. F. connected would be the is or added until stability together {era. Actually, however, coupling AMPLIFIER not the resultant inductance is not and the circuit re- is attained. perfect, jero, sonates to this leakage inductance and the capacities attached to it. LOW loss coils are used for the ampli- If this trap is found IF A_ trap tuned to the oscillating frequency and placed in the mid-tap fier, a trap may be necessary in the mid- necessary at all, the set will solve the difficulty since it puts enough loss into the circuit, of the antenna The is cannot be neutralized tap secondary. trap at that frequency, to stop oscillations." necessary for stabilizing the circuit and until the trap is prop- is useful and frequently necessary in all erly tuned, and little r. f. amplifiers using Rice neutralization. that is done to the remainder of the circuit form on which is placed some adhesive If the receiver seems to be inoperative, no will affect the frequency at which this ampli- tape or absorbent material which is cov- signals coming through, or if the amplifier fier oscillates when it is on oscillation bent. ered with collodion before the form is re- seems to oscillate without regard to the This is a phenomenon that has never before moved. The coil is then wound about a neutralizing condenser, or if a plate meter been described as far as the writer is aware. cylindrical center which makes a solid core. shows that the first tube is taking a large Coupling between amplifier, grid, and plate It may be remarked here that toroid plate current, this tube is probably oscil- coils has no effect upon it, and in the coils furnish an excellent use for enameled lating at a very high frequency. Laboratory, a mid-tap coil a yard away wire and what experimenter is there who This frequency is usually in the neigh- from the plate coil and connected to the has not longed to use a supply of such borhood of 3748 kc. (80 meters), and is tube through twisted leads still caused the wire that has been in the laboratory for a controlled by the "leakage" inductance of amplifier to oscillate. At times, the am- long time? the coil and the capacities attached to it. plifier tube has taken as much as 20 milli- These coils have a low distributed ca- What actually happens is the following. amperes with 90 volts on the plate and pacity and will tune to a wide range of The tuning condenser is practically a short negative 4.5 on the grid until the trap frequencies. Commercial coils are wound circuit for the very high frequencies. In in the mid-tap had been properly fixed. to be used with .oooj-mfd condensers al- other words, the coil is an inductance with This trap circuit will tune sharply, and though there is no reason why they cannot its two ends connected together. If the to make it more effective, some resistance be made for smaller capacities. coupling between the two halves of the coil should be added to broaden out its reson- The present article will be followed with were perfect, the resultant inductance when ant frequency. This may be done by using another giving exact constructional details the ends were connected together would be resistance wire, or by placing an iron nail of a complete toroid receiver of exceptional zero. Actually, however, the coupling is or screw in the grid leak tube. The first gain. Methods will be shown of winding not perfect, the resultant inductance is trap the writer made was constructed of traps, choke coils, and of operating the not zero, and the circuit resonates to this wire wound on an iron nail hammered into amplifier filament from alternating current. leakage inductance and the capacities at- the base board. Wire was added until It is hoped that home experimenters who tached to it. oscillations ceased. assemble the circuit will give the Labora- A trap tuned to the oscillating frequency an to hear of their dif- OPERATING THE CIRCUIT tory opportunity and placed in the mid-tap will solve the ficulties or successes. difficulty since it puts enough loss into the IS not difficult to neutralize this ampli- at that to oscilla- ITfier if are taken. It circuit, frequency, stop proper precautions Bibliography tions. is best to start experiments with a 199 type 1. "Anti-Regenerative Amplification," QST, There are several methods of tube as the amplifier and to learn all the making January, 1924, Lewis M. Hull. this One is to wind about 100 turns tricks with this tube. Then one trap. may 2. High Frequency Amplifiers, Bell System Tech- of fine wire on a dowel rod and to tune this to a tube like a 2OI-A graduate higher gain nical Journal, April, 1924, Friis and Jensen. inductance by means of a small condenser which is more difficult to neutralize. 3. A New Five-Tube Receiver, Radio, March, until oscillations cease. This tuning con- The detector is made to oscillate and a 1925, E. E. Turner. The R. C. L. Standard denser may be two six-inch lengths of carrier wave is picked up. The neutraliz- 4. New York Sun, Dec. R. H. Siemens. annunciator wire soldered to the two ends ing condenser is varied until tuning the 12, 1925, amplifier condenser does not change the pitch of the beat note. Less trouble will be had in neutralizing and controlling the set if both coils are toroids. Battery leads should be twisted and made into a cable, keeping them away from grid leads and radio frequency leads. Commercial types of toroid coils may be FIG. I I adapted for use in this receiver without The specifications for the choke coil for use in the difficulty. It is only necessary to tap the Lab circuit are given above. Twenty slots are coil in the proper place. It is not necessary provided wherein No. 36 dec. or enameled wire is to remove additional coupling coils which FIG. 12 wound until the slot is filled. The lead is then con- are the manufacturers. veyed to the adjacent unfilled slot which is filled provided by The position of the tuned trap in the same manner. Coils may be wound on a rectangular in the mid-tap of the amplifier How

How Manufacturers Avoid Broken Cabinets, Damaged Coils, Tubes, and Sockets Sugges- tions for the Amateur Who Ships His Own Set

By STANLEY W. TODD ^American Railway Express Company

Proper cushioning facturers have taken the additional pre has been found to caution, where the sets are unusuall;

be the only way by large or heavy, to place the carton in ; which the effect of crate. such shocks and jars Most of the damage to radio sets, th HOW NOT TO PACK A RADIO RECEIVER can be neutralized. express companies find, is encountered no his receiver A woolen blanket will not afford suffi- It took some time when the manufacturer ships cient protection for a set when shipped for transportation to his dealers, but when the latter refor experts and box man- ward the sets to customers, after havin; ufacturers to deter- taken them from the original package am RADIO enthusiast who has mine what was necessary to be done to replaced them again for shipping. The; with the trick o gained quite a reputation for his pack radio shipments so that they would are not always familiar in the skill in set construction, recently ride safely. This led to the development putting the cushions proper position spent many days making a set of what is known as the "air cushion car- so that they serve the purpose of offsettini A his lived in another which most of the radio manu- in transit, as intended. Fans whi for one of friends who ton," large jars These are make their own of course, are les city. facturers are now using. usually sets, familiar with the of air cushion When it came to the final step of prepar- made to fit each particular size of set, and importance and trouble is encountered trans ing the set for shipment, this fan took an much by old woolen blanket and wrapped the set in portation companies in handling thei radio it, and then put it in a wooden crate. That shipments. was ideal packing, he argued, for, of course, PROPER SHIELDING AGAINST BUFFETING it would be all that was necessary for pro- and would the fine ma- tection, prevent IT SHOULD be emphasized that neithe cabinet he had to some ' hogany gone pains loose excelsior nor paper used for cushion to from scratched or marred. get, being ing absolutely neutralizes the shocks of or But on it that the set had arrival, appeared dinary handling, because when it is crushec suffered the and when the severely by trip, down, especially if a wooden box is used tubes were in the sockets and the bat- put practically every jar of a serious nature i a came from tery connected, not murmur transmitted to the set. There are too mani the loud The man for whom it speaker. fine adjustments in the average receive was made at once communicated with the not to cause some trouble, if extreme can builder and claimed that the com- express COMMERCIAL PACKING FOR A MANU- in handling is not encountered, especially had treated the pany shipment pretty FACTURED SET when the cushioning feature is disregarded in it to him. roughly getting Inside the larger packing carton, usually made Damage often occurs to some of thi An who had of is more card- express company supervisor, up corrugated material, placed handsome cabinets used by manufacturer: to the rather difficult board so arranged as to provide an air cushion given much study because of the inherent weaknesses of thi around the set problem of packing radio shipments prop- completely erly, was brought into the case. When he examined the container and found that the cushions, so called, are merely corru- only a heavy blanket had been used to gated board, scored or bent in such a man- cushion the set against the normal shocks ner as to provide at least a two-inch open and jars of transportation, he knew just space between the inner wall of the outside where the trouble lay. It was apparent carton and the top, sides, and bottom of that the blanket offered little protection the set. The shipping unit is thus a box of this sort, which is considered absolutely within a box. essential in every good radio "package." The air cushions hold the set in sus- The average builder of a radio receiver, pension and prevent the jars which the amateur or professional, handles a set shipment may encounter in transit from very gingerly in carrying it around. He reaching the delicate instrument inside. would consider it quite a problem if he had When put upon a flat surface, the cushions to take it a distance the air from and that great by hand, always prevent escaping, PLACING THE RECEIVER IN THE BO> fearing that the fine inside adjustments gives a spring-like quality, absorbing the Air cushions are arranged on all sides. The onli would be disturbed. In transit, a shocks and the instrument shipment holding tightly step yet to complete is the placing of the cor may be handled thirteen or fourteen times. so that it cannot shift. Some manu- rugated pasteboard on top of the panel JUNE, 1926 HOW TO PACK RADIO SETS FOR SHIPMENT 127 material. The grain of the wood in the Here again the air cushion idea has in the package, and provides a cushion of end pieces of a cabinet, for instance, should helped to solve the problem. Express some sort to protect the tube from shocks run crosswise and not lengthwise. Other- companies recommend the use of cartons and jars. wise, when the end pieces are grooved out sufficiently large at least to allow one inch Despite all precautions taken, there are where the back panel fits, the wood is on the bottom and top of the mouth of the still some cases of filament breakage. As weakened and a slight shock will cause the bell. The base should be packed separately this slender wire is less than one-fourth ends to split with the grain. If the either in another carton or in a separate the diameter of a human hair, a slight jar cabinets are made of green wood or un- compartment in the carton holding the may break it. A heavier shock will dis- seasoned lumber, similar trouble may turb or disarrange other elements inside of develop. the tube, causing short circuits in the tube, Panel breakage used to be quite com- A fan who ships a tube only protected mon, because in a good many sets some of by the carton that he buys it in from the the necessary parts, like condensers, heavy dealer is taking a big chance, as it was not coils and the like, were hung from the rear intended to serve as a forwarding carrier. of the panel without support. In trans- A tube carton should be placed in another portation, this weight proved too much and strong container large enough to allow a cracked panel sometimes resulted. In several inches of excelsior on all sides of the the sets of to-day, with the large use of sub- tube carrier. Tubes that have been used panels and the tendency to place the heavi- for any length of time should not be ship- est parts on the base, the panel is given ped, as the filament is exceedingly brittle much more consideration, and, therefore, even though the tube may still function, rides without often encountering trouble. and may not stand handling. Of course, common sense dictates that BEFORE SEALING THE CARTON In the express business, the employees the tubes should not be left in the set when have been so cautioned Note how the receiver is completely and firmly frequently regard- a receiver is shipped, nor should any loose suspended by its interior case. The normal ing the need for extreme care in handling will not the or equipment be placed in the cabinet. Obvi- shipping jars dislodge apparatus all kinds of radio shipments, that this traffic damage the cabinet if similar precautions are ously batteries should be sent separately to-day is being given special attention. taken whether or not the receiver is manufactured or home built. The amateur shipper may not be able to produce a box as workmanlike as the ones from the box factory, but he can easily apply the same principles and be sure of adequate protection for his set when it is shipped

bell. A hole should be cut in the card- board which fits into the carton, to hold the neck of the horn firmly. At least one cushion or filler should protect the mouth of the bell from coming up against the bottom of the carton. "Fragile" labels and one "This Side Up" label on the top, assure proper treatment in transportation. SHIPPING RADIO TUBES

A S TO the packing of radio tubes, the THE TOP AIR CUSHIONS ** leading manufacturers have adopted SHIPPING THE HOME-MADE SET In this particular type of carton fit snugly over standard cartons which have proved satis- Transportation companies prefer the use of air- the of the receiver the dials and panel protecting These a corru- cushion cartons, but where these cannot be the factory. usually comprise face of the panel. When shipped, this re- obtained, the best packing material to use is ex- collar with a felt to be ceiver will have cushions on all sides, thus reduc- gated wrapping celsior. At least three inches of this material ing the chance of damage to an absolute minimum should be placed all around the receiver to insure safety in transit ' and there are special ways for packing both dry cell batteries and wet storage A good many of them are radio fans them- batteries. Practically all of the manu- selves and know how delicate the set facturers are using individual cartons for construction usually is. B batteries, thus removing any danger of Even though prices of receivers gener- short circuiting, while the standard crate ally are lower than they were a year ago, it for a storage battery is so made that it is undoubtedly false economy to attempt to must always be handled "right side up." skimp on the proper packing materials Such crates or boxes are made so that ex- that will insure the set being properly pressmen will have something to take hold handled in transit. If the average fan of in handling them. would give the same time and care to the Much trouble in transportation has been SHIPPING CASE FOR A 3O-POUND SET packing of the set as he does to the con- encountered in handling shipments of loud Receivers which weigh more than 30 pounds struction and hook-up, much of the break- will travel more with a wooden crate speakers. The bell or horn of the type in safely light age encountered in the movement of the around the corrugated packing case most common use is made of wood or fiber, radio traffic would be avoided. and is classed as "fragile." The parch- The transportation companies are seek- ment disc type cannot stand much rough placed around the tube, and the whole in- ing the cooperation of the public with tht handling. Most manufacturers use car- serted in a special carton. This carton is proposal, which seems to be fair, that if a tons made for their particular type of not expected to prevent a tube from being radio shipment is packed with due regard loud speaker, and most instances of damage smashed in case of an accident, but it is for its fragile and breakable character, in shipments have come in the reforward- strong enough to protect the tube from they will do their utmost to handle it prop- ing of them by dealers and individuals. injury, if it is held firmly, allowing no play erly during its travels. A few of the Sets Submitted in the RADIO BROADCAST- Eveready Contest for a non-radiating Short-Wave Receiver

E illustrations on these two pages depict some of the magazine to frown on "bloopers," it has not been possible to de short-wave sets that many interesting have been received scribe in the editorial pages of the magazine a simple and efficien in the RADIO BROADCAST-Eveready contest for a non- receiver for the higher frequencies. radiating receiver to operate on the short amateur waves. From the manuscripts submitted, fifteen have been chosen a With the close of the contest, the of elimination is the process actively most promising from the standpoint of their non-radiatin, under and the winners will be way, probably announced in the July qualities, simplicity of construction and operation, and ori number of RADIO BROADCAST. This contest was announced for the ginality. From these fifteen, the judges will choose the three tha reason that all short-wave sets now in practically operation radiate seem to possess the highest qualifications, and these three will bi more or less violently, and since it has long been the policy of this described in RADIO BROADCAST. The receivers illustrated here are not chosen with any particulai idea in mind, except to show characteristic receivers. Thei indicate nothing whatever of the relative merits of the fifteer from which the final choice will be made. The receiver at the left came from W. S. Pritchard, of 430* Euclid Avenue, Cleveland, Ohio, and uses four tubes, two detectors an oscillator, and one stage of audio-frequency amplification. Com plete shielding is used to eliminate stray couplings and, althougl the photograph does not show it, there is a brass cover for th< receiver, making it a very attractive piece of work. The receiver below was constructed by L. W. Hatry, 46 Soutl Marshall Street, Hartford, Connecticut one who has long beet known in the amateur game. This receiver is typical of the ex cellent construction that appears in the best amateur sets to-day and in gives good detail the relative arrangement of parts, in eluding the disposition of the sockets for the plug-in coils. On page 129 are three more short-wave receivers, the one ir the upper right representing the product of Mr. J. Kriz, 1628 Rigg: Place, Washington, D. C. It is a three-tube set with a o RADIO stage BROADCAST Photograph radio frequency amplification before the detector. The amplifiei THE ENTRY OF W. S. PRITCHARD, CLEVELAND, OHIO and detector operating at radio frequencies are tuned with i o mon

RADIO BROADCAST Photograph THE ENTRY OF L. W. HATRY, HARTFORD, CONNECTICUT JUNE, 1926 PRIZE CONTEST SHORT-WAVE RECEIVERS 129 complicated than with the ordinary Reinartz set. In the RADIO BROADCAST Laboratory it seems to have a penchant for southern stations, as XDA, Mexico City, has been heard pounding away at a great rate for many successive evenings. The second receiver on this page was built by Robert H. Free- man, East Orange, New Jersey, and is a four-tube set. It shows an excellent arrangement of parts, with a minimum of gear between the coils and condensers. The receiver below was constructed by another well-known amateur, F. Cheyney Beekley, Glastonbury, Connecticut. In this case, the apparatus is mounted on a metal sheet which has been bent so that it forms a continuous shield, a part of it being used as panel and a part as base board. A Silver-Marshall coil is used as inductance, and all parts carrying radio frequency currents are kept well away from the shield. As this is written, tests are under way to determine the relative RADIO sensitivity and freedom from objectionable radiation of the BROADCAST Photograph various receivers. A fixed oscillator of low power is installed in SET SUBMITTED BY J. KRIZ, WASHINGTON, D. C. the Laboratory and signals from it are picked up at the shack which houses 2 GY, about 400 yards distant, and the audibility measured. All receivers are compared with a Reinartz circuit set temporarily used as a standard and which has proved to be very sensitive and simple to handle. The first test for radiation is a simple one. The receiver is made to oscillate with 90 volts on the detector, and is attached to an antenna at the Laboratory. If its signals can be heard at the shack it gets a poor rating with regard to radiation. It has been found that the Reinartz receiver puts R} signals into the shack under these conditions, and it forms one method of communication between the Laboratory and 2 GY. If the signals from the receiver cannot be heard, the distance is decreased until they are audible and equal in strength to those of the Reinartz, and then points are awarded. While there is no reason why any operator RADIO BROADCAST Photograph should use 90 volts on the detector tube, such practice in our tests CONTEST RECEIVER OF ROBERT H. FREEMAN, EAST will determine the maximum distance at which the conclusively ORANGE, NEW receiver will cause trouble to other listeners. JERSEY

RADIO BROADCAST Photograph ANOTHER SET, SUBMITTED BY F. C. BEEKLEY, GLASTONBURY, CONNECTICUT 4V This post may be '' eliminated and common * - C A post used in its place

FIG. I

The modified Silver circuit employing a grid leak and detector, r. f. oscillation control, and separate C and B battery connections is shown here. Thi changes are more evident when one compares this circuit with the original circuits appearing in the November, 1925, and January, 1926, RADIO BROADCAS* or with the circuit shown in Fig. 9, page 132. The B battery terminals, I, 2 and 3 are for the 90, 90-135 and 135 volt taps of the battery respectively

gtessive

Changes Which Will Improve This Receiver, Built by Many Readers of RADIO BROADCAST By THE LABORATORY STAFF

HAVE made several changes in the or post. This would reduce the number of Model 1926 Silver receiver (described battery leads or posts to eight, since there in RADIO BROADCAST for November, are two+C posts to be provided for. By I 1925 and January, 1926), all of which including small blocks of C within battery have added to the selectivity, sensitivity the cabinet and directly wired to that part and tone quality of the receiver." This, of the circuit to which it applies, the number in the main, is the gist of numerous letters of battery leads may be cut to five: received RADIO BROADCAST. writ- by The i. minus A minus B; 2, plus A; 3. plus B 45; ers their letters with a usually complete 4. plus B 90; 5. plus B 135. Reference brief outline of the changes made. to the modified circuit diagram, Fig. i, In the RADIO BROADCAST Laboratory, will make this suggestion quite evident. we have been conducting some very inter- IMPROVING DETECTOR SENSITIVITY esting experiments of our own on this receiver. Our report, with which is blended of the main changes in the receiver much of the valuable information gleaned ONEproper is the replacement of the de- from those who have built and experi- tector C battery with the more standard mented with this set undoubtedly will aid grid leak and detector. In including the those who have had and are having con- grid leak and detector in the circuit, it is siderable difficulty in making their own model of this set work properly. In all probability, it will be found helpful to provide the receiver with a terminal strip having 12 posts. It is doubtful whether the majority of manufactured battery cable cords have enough leads so that it alone may be used to connect the receiver to all the batteries used. Several of the terminal posts may be eliminated or one lead may be used for several purposes, as in thecase of the A B+ C lead JUNE, 1926 CHANGES IN THE MODEL 1926 RECEIVER 131

FIG. 3 Modified Detector One of the Circuit simplest changes is in substituting a grid leak and condenser for the C battery method of detection. The connections for the change are outlined in the circuit Fig. 2

-A Line

RADIO BROADCAST Photograph In a leak and condenser for the substituting grid C battery 1st. STAGE: AUDIO 2nd. STAGE AUDIO 3rd STAGE AUDIO method of detection, the return or lower side of the detector secondary circuit must connect to the positive terminal on the detector tube socket. These are outlined here To J changes Detector 5

FIG. 4 To apply an effective voltage to To B + the of the detector and first Separate plates Terminal for Plate and second stage audio amplifiers, Volts 90 to 135 the lower side of the plate resistances are connected to a separate B battery terminal post as shown here. Since in the loud speaker circuit, there is no high resistance, the plate of the last tube has a full 135 volts applied to it

RADIO BROADCAST Photograph FIG. 5 Since it is not possible to make use of the battery cable cord for all the terminals, it is necessary to employ more terminals for the additional battery connections. These are provided by the use of the Fahnestock clips as shown

FIG. 6

To control satisfactorily, oscillation in the radio frequency stages, a variable high resistance unit is connected in the radio frequency plate circuits as shown. This resistance, for best re- 67', or 90 V sults, should be by- passed by a fixed condenser. Various values may be tried. That suitable in RADIO RADIO BROADCAST Photograph BROADCAST'S Laboratory tests was an .oo6-mfd fixed condenser. The FIG. 5oo,ooo-ohm variable resistance employed in the original Silver circuit 7 will usually be found unsatisfactory in the modified circuit. One having The position of the variable resistance is not changed in the modified .a maximum of 200,000 ohms such as the Centralab No. 201, or 203 receiver. Merely replace the 5oo,ooo-ohm unit for one having a maxi- is recommended mum of 200,000 ohms 132 RADIO BROADCAST JUNE, 1926

200,000 ohm Oscillation Control .006 mfd. Condenser

RADIO BROADCAST Photograph

135V. FIG. 8 BBat. The changes made in this circuit are evident from a glance at the illustration which shows Fahnestock clips for separate B and C voltages, a grid leak and de- 90 to 135 V. tector, and a variable resistance of 200,000 ohms shunted by a .oo6-mfd condenser BBat.

PROPER B BATTERY FOR THE PLATES OF this last stage a semi-power tube may be 1. Provide separate leads for first and second THE AMPLIFIER TUBES employed to the best advantage. r.f. stages, first and second audio stages, and last also detector if other than resistance In all the stages, both r.f. and a.f. it is stage; stage, - coupled amplification is employed. resistance coupled, audio- decidedly necessary to be sure that one uses 2. Insert a 200,000 or variable WHERE is joo.ooo-ohm frequency amplification employed, the correct C battery as indicated in Table I . resistance in series with plates of both r ,f. tubes the plate return side of the detector and These same changes as made in the re- and B battery terminal. first and second stage plate circuit resis- sistance audio amplifier will hold for good 3. Eliminate C battery for detector and re- tances connect and then lead to both transformer and choke coil audio am- together place with grid lead and detector. another terminal or cord. This with the in separate plification exception that these 4. Use proper C battery voltage on r.f., first is so that B voltages in excess of 90 may cases, lower B voltages will be found satis- and second a.f. and last a.f. stages. Use a be applied to the first two stages of resis- factory. In the latter two types of audio 5. semi-power tube, with proper B and in the last audio tance audio amplification without affect- amplification named, a separate connec- potential grid bias, stage. ing the radio-frequency amplifiers. In the tion from the plate circuit of circuit the connections original diagram, the detector tube will be , were such that not more than 90 volts found necessary to prevent could be applied to the plates of the first the detector from continu- two audio amplifier tubes without, at the ously oscillating. The extra same time increasing the r.f. plate voltage. lead may well connect to the is in This change outlined Figs. 4 and 5. 45 volt B plus terminal of The plate return of the last audio stage the B battery. should connect to its own terminal for a In summing up, then, the separate B voltage, which may be still modifications which will be higher than for the first two stages. In found beneficial are:

R.F.T.

ANT.

GND.

FIG. 9 This is the original circuit showing how either transformer- or resistance-coupled audio frequency amplification may be used. A comparison between this and the circuit shown in Fig. I will make obvious the alterations B*90 B+45 A-B-C+ Conducted by John Wallace

Why it is Difficult to be Funny Over the Radio

radio programs are improving in Occasionally, very occasionally, we hear some- difficult to deal with. quality, even the most thing We refuse to laugh lugubrious crape- thing that reassures us that humor is broadcast- THAT must at a radio wise-crack for much the same hanger admit. And we make haste able. For instance perhaps we have howled heartily at reason that we to admit it. don't out loud at a The healthy condition of compe- Ford and Glenn. The laugh funny "Happiness Boys," Billy we are tition where several paper reading in the street car. The existing hundred broad- Jones and Earnest who hold Hare, forth over contagion that a casters are daily for the listeners' cherished sweeps laugh through a vaude- vieing WEAF Friday nights, are ears of consistently funny. ville house is denied the listener-in. Efforts of has, necessity, resulted in a And there are a few considerably others. In speaking here of the radio clown higher level of to inject the element of entertainment. humor we have in mind rapport specifically monologues by laughing with his audience Need we say that them kind words do not and invariably meet wit-and-repartee skits, and do not mean to with dismal apply as a blanket failure. Nothing in the world compliment to the whole include humorous or humorous songs musical sounds more mournful and mirthless brotherhood of broadcasters. stations than a loud Many skits, which get by partly on the of the are as strength "haw haw" as conveyed radio. just bad as they were two, three, or four music. by As to years But the what the humorists themselves have to ago. stations that have pro- In of our support alternative solution of the say on the we gressed have done so such and bounds subject, append the following re- by leaps problem it might be observed that the radio even port compiled by from interviews that, though a minority, have audience Myra May they greatly differs from the theater audience in that with boosted the three prominent comedians, B. average rating of broadcast fare. it is Billy Van, not a "crowd." It presents no Will Nor does the "group Rogers, and Joe Cook. encomium apply to all mind" to the depart- radio entertainer, and hence is a ments of "The hardest thing for the comedian to bear broadcasting. Certain types of in mind when program have improved while others have talking over the radio," says Mr. Van "is that the audience is lagged behind. By far the greatest advance has looking at him ears and that been in music, both high- and through he must to them low-brow. We doubt if radio will ever appeal through their offer mental eyes. This means that he can't any better jazz bands than it now furnishes shamble out with an awkward and (though, with the help of the gait look around him with a jazz composers it may well offer better bewildered expression while the take jazz music). There are highly skilled spectators in the to be details of his baggy trousers, enormous syncopators heard from every part red nose of the country. shoes, and absurd little hat cocked on one side of his head. And real music is being heard more He can't and more depend on any to frequently. A fair smattering stage properties bring out an obscure of the best symphony orchestras are point. He has to attract the attention of his audience regularly on the air. The roll of opera immediately and his stars and concert artists who have been explain properties as he goes along. "He is allowed heard once or oftener has reached amaz- much less leeway than on a stage. He can not walk from ing proportions. Sports announcing is away the another program item that has evinced microphone and leave his invisible audience he is great progress. Others could be enumer- wondering what doing. He can do his ated. only work as well as possible, secure in the But tossing aside, for the moment, our knowledge that good work will hold the who horn, and picking up our hammer, we people listen-in as with surely as it holds those who sit in front point, tears behind our eyelids, to one of the type of program that has improved footlights. "There are, certain nary a whit. And that is the "humorous" moreover, very positive 'don'ts' that radio hu- program. All great art, unless it be too govern morists. Diction must infernally sublime, has an element of hu- be perfect, voice mor in resonant and or about it. But radio, the most every syllable clearly enun- "art" ciated. Much of this is loudspoken of this Age of Progress accomplished by is word substitution, because certain words lamentably devoid of this enlivening feature. do not carry well. The letter V for This is due to example never goes over the air one of two things: either distinctly. the So that if the comedian is a program directors haven't been spend- telling story where on the stage he would use the word ing enough sleepless nights cogitating on this or it 'string,' he must substitute 'twine' for subject, is inherently impossible to the benefit of his radio audience. put across humor through the me- WILL "In a dium of radio. Which of these reasons ROGERS telling joke, there is always the is the correct One of the best known humorists in grave danger that the won't be one we have not yet doped stage America, whose point out. opinions on humor radio are Perhaps you have? At rate by presented in this department clearly emphasized. Perhaps the last any this month. we'd be Entirely parenthetically, Mr. is re- sentence which usually contains the very much interested in hearing Rogers pith ported to have returned from Florida with the of on the remark that the story will be distorted and the your opinion subject. the real flower of that state is now the sucker all-day listeners will have waited in vain for the 134 RADIO BROADCAST JUNE, 192* humor. They will have endured the long- Joe Cook made his radio debut not long winded explanation that led up to the climax and ago. too fast be- then missed the whole point. As a result, the "At first 1 found myself talking he "but radio comedian tells his story much more directly cause I was rather nervous," confesses,

1 had the than he would on the stage, he can not allow any inside of about three minutes, caught

I as I were rambling from the main point, any loitering by spirit of the thing. felt though really audience. the the wayside and yet he must not be too abrupt, talking direct to my Throughout afraid too direct. whole time I was on the air, I was deathly " 1 as 1 Radio, however, has brought a great contri- I was mechanical, that sounded though instead of with bution to humor in that it has clarified the jokes were talking into a record joking of the merrymaker. Where a a real flesh and blood audience. professional " 1 don't want to as a radio for I slight innuendo, a double meaning that was pose expert, it is have had limited So slightly risque, could be used on the stage, really very experience. I have told the same stories absolutely taboo on the air. Only the cleanest far, however, that I tell over the foot- of clean humor, entirely free from suggestion, is through the microphone

In I believe that there will be permissible. Considering the millions of people lights. time, humorists who will write material that may be listening-in and the little children specialized This material will that are probably part of the audience, this is especially for the radio. be much cleverer and more subtle right and proper. probably very for "The comedian is considerably hampered by than the usual line of patter in use to-day, lack COOK this very diverse audience. He can not tell when you appeal strictly to the ears and JOE must create witticisms that appeal locally, he can not tell even the prop of personality, you Who tells his opinions of the difficulties o over" humor on the air. Mr. stories that hold a race, a class or a religion up to proportionately brighter quips to hold your "putting Cook a favorite on is best knowr ridicule, he can not make a pun that is compli- audience. Broadway, perhaps" for his of the four act is the same as impersonation Hiwayians' cated, he cannot jest of things which are not "My radio practically my in familiar to the every day life of his hearers." stage, except that I try to put more unction Says Will Rogers: "Talkin' over radio is like the former. On the stage, I can juggle with It would be possible to take some selection ii talkin' over the footlights. When I'm most balls, bottles, ladders, musical instruments; on literature that every child should know and havi I with voice and serious, people think I am tryin' to be funniest. the radio, can juggle only my it read by some such master voice as Julii Lots of times I could swear would a big the musical instruments." gags get play Marlow's. It would be possible on holidays flat. never can tell laugh, fall perfectly You such as Washington's Birthday, to have notec what is going to strike the public funny. Why Radio Cannot "Educate" authors read from their own selections. N< I child could listen to Edwin read hi: Generally I make up my gags as go along. Markham loud noble "Lincoln the Man of the Best ones I ever pulled come to me all of a sud- HAVE never emitted whoops poem, People,' concern- without getting a fuller appreciation of Abrahan den while I was killin' time trying to think of and hurrahs in these columns Lincoln and a finer feeling for poetry. something to say. WEing the educational potentialities of It would be possible to have musical selections "'Swinging a rope is all right," I remember radio. And for the very simple reason that we both vocal and instrumental, played to a nationa 'when neck isn't in it. Out West do not believe that radio can educate. To saying, your audience of school students. Geography coult where I from won't let me with to Mr. is to "de- come they play educate, according Webster, be made a rich adventure by introducing fre this rope, they are afraid I might hurt myself.' velop or discipline the mind by systematic quent talks by men and women who had recenth Well, the audience started to laugh and forgot to instruction or training." This, radio is not visited areas which the children were studying There are also for radio in thi look at the lariat. I was saved. After that, 1 likely to do. large possibilities of instruction. More than hal started to make remarks regularly until the time But most of the blah we read about radio as improvement the teachers of the United States have had les come when I hardly did anything with my lariat. an "educational" factor is sincere enough, and than two years of training beyond the four-yea "Now when I talk over the radio, I sure don't can be made true enough by the simple device high school. need a rope. Course, 1 can't hear whether the of substituting the world "informational" for Were there a radio in every school, it would bi folks are at but that's a "educational" wherever the latter laughin' my gags, pretty appears. possible to broadcast master lessons and reci good thing after all. I jest imagine they laugh, For radio certainly can inform In the space of tations in various subjects which would be ricl whether they do or not, and that way puts some an hour's random dial twisting we are likely to in suggestions to younger and inexperience* teachers. There is another that is mos heart in my act. If I was to hear them not glean information on any subject from the Care angle is an arduous laughin'. it'd like to break my heart." and Nurture of White Mice to Efficient Methods important. Teaching occupation There are long hours of uninterrupted strain of Lubricating a Traveling To break this strain a few times the Crane. during da; by genuinely helpful inspirational material ove While are still we skeptical the radio would enable the teacher to come bacl about the ultimate value of into the day's work with fresh vigor. These ar radio the thousand and one just a few of the possibilities. extension courses offered by many colleges throughout the Mr. Morgan does not mention it, but Oak country, we are quite amena- land, California has conducted an experimen ble to the arguments offered by (through KGO) in the use of radio in teaching ii one Joy Elmer Morgan of the the schools, with results that the Oakland schoo National Educational Associ- authorities declare to be most satisfactory. Ii ation in favor of the use of fact the situation in Oakland has passed thi radio as an ally of primary experimental stage and the system has beei education. For the fact that adopted as a fixture. A nation wide extensiot radio is a puny educational of this practice seems inevitable. force while standing on its Of course we who learned our three R's in thi own legs doesn't argue that dark ages before radio need have no fears tha it can't be put to some good the infant generation of readers and writer use with some better estab- and arithmeticians is going to learn any mon lished educational medium to with radio's help than we did without it. Bu cling to. still, we in our day, didn't have to risk our slende Mr. Morgan urges that radio young necks on the way to and from schoo receiving sets be given a place dodging speeding automobiles, so it seems onl^ in the class room. Among the fair that the children of the machine age hi 25,000,000 school children in entitled to whatever of good machinery has t< the United States, he points offer. out, there are probably a mil- Let the normal schools hasten to offer a coursi BILLY B. VAN lion who are studying approxi- in The Quick and Careful Tuning of Radii Another humorist artist with words and ideas. His impressions mately the same thing at the Receiving Sets. Perhaps it might be given bj of the possibilities of humor on the air are quoted for the first time same time. Says Mr. Morgan: radio! JUNE, 1926 LISTENERS TELL WHAT THEY WANT 135

What the Listeners Say They talk too fast. Other suggestions offered to Want improve announcing were: Stop the announcers from trying to be humorous; make the an- management of station wjz during the nouncers be brief and eliminate broadcasting last two months circulated 10,000 lengthy descriptions of selections or the life THEquestionnaires covering afl of the im- story of the composer. portant phases of broadcasting, so that the There seems to be a preference for programs impresario in making up the programs would broadcast by a chain of stations linked with a know just what the public most desires in the city station where there are plenty of artists. form of radio entertainment. The question- One listener expressed the opinion of many with " naires were sent to all who wrote to the station the answer. Better programs are generally reporting on reception of the 5o-kilowatt trans- put on by a chain of stations than any one mitter. station can promote." A number of Pacific The questionnaire was impersonal. No one Coast listeners commented upon the fact that it was asked to sign his name. Each questionnaire would be a good plan to have a chain of stations was accompanied by a stamped addressed en- in the Far West linked by wires with New York. velope. More than 4000 were completely Broadcasting of church services on Sunday answered and returned to the station. The were commended by many who answered the results have been tabulated, under the direction questionnaire. Many specified their religion of statistician, and they show what .broadcast but did not express a desire for any particular FREDERICK WILLIAM WILE listeners prefer to hear on the radio. denominational service on the radio. KDKA'S Classical music was 33 per cent, more popular church service won mention in Washington special correspondent and political special many than cases. observer, who broadcasts decidedly interesting jazz. talks every Thursday evening through WRC The answers revealed that orchestral music is and wjz. His subject is "The Political Situa- the most popular. The other instrumental Concerning Radio Plays tion in Washington," and if you enjoy keen ob- music is rated as follows: bands, symphonies, servation and well done verbal reporting, you violin, organ, piano, 'cello, saxophone and RAISE from Heywood Broun, a keen ob- had better hear him cornet. In the instrumental group, quartets server and critic, as quoted from his column were half again as popular as trios and twice as P in the New York H'orld: Esperanto as the Interational much in favor as duos. I am less sceptical than I was once about the Relative values of the service end of the pro- Radio Language potentiality of broadcast drama. I have heard grams showed news is 25 cent, more per popular several plays upon the radio and never with de- to be convinced that than time and which ranked HAVE yet signals sports, light. But recently John Drew appeared during Esperanto either can or should be made second and third respectively. National and the Eveready Hour and when he did a snatch WEan international language. Our preju- local news broadcasts ranked about equal in from "Rosemary," dramatic illusion was established. did succeed in a situation dice against this coined auxiliary tongue is based importance. The other service features were He making become alive and take on Given on several, what we consider good, reasons. But voted for as follows: stock reports, financial poignance. sufficiently high skill on the part of the perfor- we have a sincere respect for the tenacity of the reports, road conditions, agricultural infor- mer, it is extremely difficult to set a boundary Esperanto propagandists, who certainly have mation and cotton reports. and say, "Beyond this point the radio is ineffec- little to its The most broadcast in the personally gain by promulgation. popular sport tive." We are in receipt of a letter from Robert S. United States is baseball, according to the Woolf, American secretary of the International questionnaire. Baseball was 10 per cent, higher And the following remarks by George Arliss, Radio Association, from which we quote: than football, which received the second highest vote. There is but one solution to the problem The other sporting events which confronts successful world-wide broad- ranked as follows: boxing casting, and that solution is the idea of an inter- and horse national, auxiliary language. From the time racing. Hockey of the Roman Empire there have been thoughts did not show up well in the and schemes for a single world tongue; many votes submitted by listeners have been invented, tried, and found wanting in this country, but the Cana- but there is a language which in actual practice dian answers placed hockey has been suitable. That is proved language in first place as the favorite Esperanto. sports broadcast and horse In its grammar and its system of word- racing was second. Baseball building, Esperanto is the extreme of simplicity. received a few Canadian An educated person can learn it well for reading, writing and speaking in three months of ordinary votes. Canadian votes for study. After a few hours' study one can take up football were very few. correspondence in the language with interesting Travelogues ranked far people in all parts of the world, thereby ma- ahead in the field of talks. one's and inter- terially increasing knowledge Scientific topics were second, national viewpoint. with the other subjects voted Particularly in radio use Esperanto has been for as follows: politics, found to be the only suitable world language. health, economics, Beginning with a speech from wjz in Newark. literary, and June 19, 1922, about Esperanto as the coming art, debate, forum, world language, the number of stations broad- beauty. casting about and in Esperanto has grown pro- The questionnaire clearly portionately with the increase in the number of shows that men announcers radio stations. In five discourses about 1922, are more popular than wo- were broadcast in America and Esperanto men announcers. Several Europe. In 1925 about fifty such items were on spaces on the questionnaire the air, more than two hundred in 1924, and were so that radio during 1925 approximately twenty stations on provided both sides of the Atlantic have broadcast fans could make comment regularly in Esperanto. Many stations have on the art of announcing. been giving lessons in the language on the air, The general complaint was in the United States such lessons being broadcast that the announcers do not WRNY of New York, the station of Radio by give the station call letters News, which magazine has been an ardent sup- frequently enough. Some K. M. LANDIS AND WILLIAM WRIGLEY, porter of Esperanto as the only suitable auxiliary JUDGE JR. complained that there are language for international radio use. A recent They are lending their august presence to the studio of KFWO at too between report from Germany states that every station long pauses Santa Catalina Island, California. Just why, Major Lawrence selections and that the an- in that country is now giving a weekly program Mott, owner of the station (try to find him in the picture), failed in Esperanto. nouncers in many cases to inform us 136 RADIO BROADCAST JUNE, 1926

Mr. John Wallace, RADIO BROADCAST, Garden City, New York. SIR: Why wouldn't it be a good idea to let us have some folk songs once in a while, oftener, if possible? Gee, with that ancient and honorable name of yours, I'd be strong for the "hundred pipers and a' and a'" and all the rest of the Scottish songs, reels and strathspeys. These, to my way of thinking, contain the very soul of music. What is more inspiring than "The Cock o' th' North," more tender than "A Pretty Girl Milking Her Cow" (Irish) and for sheer loveliness try and equal "Annie Laurie." COLIN F. MORRISON. Wayne, Michigan.

iii>iiiniNiiui

versatile Graham McNamee of WEAF'S THEstaff added no little interest to our nightly ear work, some time ago, when he read a group of verses, among them Gray's " "Elegy" and Kipling's Boots," to a decidedly rousing THE A & P GYPSIES musical accompaniment. We learned later of Who are one of the steady features of the week's radio program heard through WEAF, WEEI, WJAR, at least four bridge games he broke up with his WCAP, WWK, and wcco every Monday evening from nine to ten, Eastern Time. The orchestra is impassioned and hypnotizing recital of the mad under the direction of Harry Horlick "Boots."

at were in- who makes sanguine prediction that the radio picture will stimulate the interest and appreci- Shenandoah, Iowa, we ation of the in the KFNFformed certain play is destined to be a greater dramatic art public possibilities of the by publicity material, theatre itself. broadcast for consecutive hours on its than the motion picture: thirty birthday. Yours for larger and longer days! The great value of the radio play, is that it When, with the millennium, comes the forty brings to its listeners what the motion picture Communications hour day, we shall utilize the extra sixteen hours never can give, the literature of the theatre. It for in bed of a is rather easy for most people to visualize the lying morning. setting, or surroundings in which a story takes Mr. John Wallace, place. But it is almost impossible for them to RADIO BROADCAST, ARRANGEMENTS are being made, we are the after is ** supply conversation, which, all, the Garden City, New York. told by KOA, whereby all important athletic literature of the drama. SIR: matches and contests throughout the country In the of Barrie, of Pinero, or the I plays O'Neil, have been interested in your "Listeners will be relayed to Denver by a network of leased charm lies in the spoken words. When Point of View" and in the they columns, February wires and flashed over the microphones. To are in the produced pictures audience sees only I noted in issue, "Readings Foreign Languages." what extent will be handled in detail or the in its across the they story proper setting, flitting The other evening while looking up a German screen. must the conversation play-by-play, however, will depend on the They supply word in the dictionary and listening to some themselves, out of their own in their nature and general interest of the attraction, it experience, station who was broadcasting in a foreign own vernacular. But the radio will retain was said. In the case of and other play language it suddenly occurred to me to get a golf, tennis, all this and the charm, intelligent, sympathetic dictionary of that language, pick out some word tournaments, it was expected that a summary listener will be able to create on the of his stage used frequently and hear just how it was proof final returns would be sufficient. own imagination the for the setting story. nounced. The result was startling and I picked out several more with equal satisfaction. And DID not hear "The Miracle" as Mr. Arliss is of the that, to across opinion get now when I see those words 1 can \A/E pronounce ' broadcast WGBS the New to an audience, an actor must be seen, not by during merely them quite easily. If that linguist would tell York run of the spectacle, but have just recently heard. He does not look forward to successful his listeners what he was going to read on a heard it broadcast from the Auditorium theater professional actors ever becoming "radio stars" certain night and hour from a certain station we in and tender it beloved by thousands of far away fans. Con- could get the article and follow his reading and Chicago by WON, sundry palms tinues Mr. Arliss: gain a great deal more than in any other way, as one of the best things of the year. Of course even if we didn't understand any of it at first. the success of the broadcast was mostly due to I doubt if, over the radio, there will ever be C. J. FINNEY, the enormous appeal of the play itself, but a enough difference between the thousand-dollar- Nashotah, Wisconsin. none the less large share of praise must go to the a-week man and the hundred-dollar-a-week radio technicians who made its aerial man to attract the successful actors to the radio Mr. John Wallace, possible with so little diminution of effec- "stage." RADIO BROADCAST, presentation tiveness. "The Miracle" Until some way is devised of making the radio Garden City, New York. being preeminently play a profitable commercial proposition, 1 think SIR: a spectacle and feast for the eye would seem, off it will be always a Little Theatre movement. 1 often wonder why the broadcasting stations hand, to be poor material for the radio. But its if a were with so seldom furnish Perhaps, great company formed, harp music. The harp always story is of such simple dramatic effectiveness the finest actors, the best plays with which to broadcasts its music well, and its tones are so that it lost nothing in the telling by Bill Hays, work, and only those could listen in who have sweet and that it cannot but be a pleasing great the WON announcer. And the colorful music, that company's machine, the radio play would favorite with most everybody. Probably the the chanting, the hymns, and the roars, shouts, take the same place as the motion picture or greatest radio treat I ever had was when, about and cries of the 600 or more who took the theatre. But on the whole, 1 am inclined to a year ago, a harp ensemble of forty harps was persons believe that the radio play will be for the small, broadcast from New York by one of the best part in the production were ably transmitted, uncommercial theatre group. That will not stations. We have plenty of saxophone, har- which, we opine, was no mean engineering feat. prevent it from becoming a great art, however. monica and "old time fiddle" music, but the Neither the radio nor the can the of all moving picture harp, grandest musical instruments, "Eveready Hour" heard through ever take the of the theatre. The Theatre seems to have been the shelf. Can't place put upon THEWEAF, WEEI, WFI, WCAE, WOR, WWJ, WOC, is the art. But of the the we some of our only complete two, persuade accommodating pro- and WSAI will KSD, WJAR, WCCO, WTAG, WON, WEAR, radio play be most satisfying to those who gram directors to take it down, dust it off, and at 9:00 o'clock (E. S. T.) each Tuesday evening love the drama for its literature. Neither the hunt up someone who can tickle the strings we have come to count the radio play nor the moving picture play will ever occasionally. Then I'll be ha-a-a-a-a-ap-py! among pleasantest radio's the hurt the real theatre; rather, I think, they will go H. G. Reading. of offerings. For instance there was hand in hand. The radio and the moving Franklin, Pennsylvania. program of old time "Sob Ballads" of thirty STATIONS 137 JUNE, 1926 NEWS OF THE BROADCASTING

these heart- times, inhale one-half teaspoon salt, one teaspoon of the North Shore Music Festival at years ago. The interpretation of casting and one cup of flour. Then Illinois. If the similar "festi- renderers by the Eveready artists was in delight- baking powder, Evanston, many breathing naturally, exhale and sift. At- fashion. the songs were such vals" of equal or lesser importance throughout ful burlesque Among to a of tention. Jump squatting position quick the are as should as: "Break the News to Mother," "After the country tapped by radio, they time. Twist sideways and forward right and "The Picture Turned Toward the Wall" be, the last two weeks of May and the first two Ball", left as far as possible and beat egg swiftly and weeks of June will come to be the most musical and "The Bird in the Gilded Cage." briskly, arms forward over head. Raise the in the radio cooked egg with the flour and in four counts period year's offering. make a stiff which is stretched at the A RRANGEMENTS have been made by WRC, dry dough, waist. Thighs flexed, lay flat on the floor and a radio Pask- Ji at Washington, to broadcast week by week play by Dailey roll into marbles the size of a walnut. to Hop director of has one of the the adventures and experiences in the African man, WGBS, proved a straddle in boiling water but do not boil at JAZZMANIA" of the headed Dr. best novelties offered by that station. It Jungle exploring party by a gallon. After ten minutes remove and wipe National is in the form of a dramatic and musical fantasy. William M. Mann, director of the with a rough towel and serve with fish soup. of vaudeville fame, is co-author Zoological Park, which set out last month under Jimmy Kemper, and takes the role. Mr. Paskman the auspices of the Smithsonian Institution, in principal effort of the officials of the Bakelite collaborated with Rudolf Frimi on "Chan- cooperation with Walter P. Chrysler, auto- (who to determine mobile manufacturer. THECorporation and station wjz sonette," a recent song hit), composed a number ot The accounts of the adventures will be con- the makeup of the Bakelite hour by a series of original lyrics specially for "Jazzmania." four test resulted in a tied vote. The Another of the seems tained in letters written by Dr. Mann to the programs repetition fantasy likely submitted for radio audience of WRC, and rushed to the United four types of program approval and is worth watching for. assisted a small States from the interior of the African wilds. were: i. Concert artists by orchestra; 2. Grand a varied They will be read in connection with the "Zoo opera; 3. program prominent vaudeville singers, Van and classical and semi-classical selections mixed Talks" and broadcast under the direction of of by THESchenck, are among the latest recruits to instrumental and vocal Chamber Doctor Mann, and Austin H. Clark, of the soloists; 4. the ranks of broadcasting artists. They are music concert. The first three named received Smithsonian Institution, during the past year. appearing three times a week before the micro- an number of votes. So at the Doctor Mann is an explorer of international equal present phones of WMCA. Bakelite hour is varied each A fame, having been associated with many of the being Sunday. in Central and set type of program will, however, eventually be greatest scientific expeditions ORDER that those who live in the Metro- South America. In he visited the selected from the three. IN 1914 Egypt, politan area may know something about with Sinai Peninsula, Palestine and Arabia current theatrical conditions in other cities of Dr. C. of John Phillips, collecting specimens the various "Music Festi- the United States, Oliver Sayler, well known mammals and birds. Later he was in charge WHETHERvals" being held at this time of the year critic, who has been a regular feature at WGBS of the Mulford to the Amazon Valley expedition in various parts of the country are being broad- ever since the station has been operating, has and across South America to collect and study cast we can not, at present writing, foretell. left New York on a tour of the country. Each used in the manufacture of drugs and to plants We know that definite plans have been made by week Mr. Saylor will report by wire on plays on make collections. zoological KOA to broadcast Denver's far-famed Music week the road, this report to be read at the regular A Doctor Mann the radio year ago began celebration and annual spring festival. And time for his "Footlight and Lamplight" series of notes of interest from presentation weekly efforts are being made to arrange for the broad- every Thursday evening at 8:30. the National Zoo and discussions on the habits and idiosyncrasies of the animals, most of which are very familiar to the residents of Washington and visitors to the Capital City.

dance tunes of other years are being THErevived successfully on the air by William Spencer Tupman's Hotel Mayflower Orchestra through WRC. In each of the Tuesday Night "Melody Hours," played by the orchestra for the radio audience, three of the most popular dance tunes of the last fifteen years are presented without announcement of titles. Weekly prizes for naming the numbers are offered. The "Melody Hours" are broadcast from 10:30 the to 1 1 30, E. S. T., every Tuesday night from Mayflower Gardens of the Mayflower Hotel.

/CHICAGO has all too few "indirect adver- ^-' tising" programs which is unfortunate, as programs of such origin form the very back- bone of radio entertainment. There is, however, the "Federal Master Artists Series" broadcast each Friday evening at 9:00 through KYW. This series is financed by the Federal Electric Company and prominent among its offerings have been two concerts by the Jacques Gordon String Quartet, an able organization whose members are recruited from the Chicago Symphony Orchestra.

following yarn has been wandering THEabout in the public prints. It has long been divested of any evidence of parentship or author- hood, so we, in turn, will "steal" it. It has to do with a housewife, inexperienced at dial twisting, who attempted to tune-in a cooking lesson program with this startling result: Hands on hips, place one cup of flour on the THE WEAF SHAKESPERIAN PLAYERS shoulder, raise knee, depress toes, and wash thoroughly in one half cup of milk. In four Who have been heard, to the tune of much favorable comment, through WEAF every Saturday counts, raise and lower left foot and mash two evening at 8:15 in tabloid presentations of Shakespeare. Back row, left to right: Geral Stopp, Webster hard-boiled eggs through a sieve. Repeat six Katherine Emmet, Laurence Cecil. First row: Alfred Shirley, Margot Lester, and Charles Cuttin

Results of Actual Field Tests With Wave Traps on a High Power Station The Sec- ond of Two Articles Showing How Receivers Can Be Made More Selective How to Build a Radio-Frequency Amplifier and Adapt it to Your Receiver High Power Broadcasters Need Not Cause Interference

By HOWARD E. RHODES

paratively small and The open end of the antenna was pointing the only persons toward the station, which was an advantage who will be seri- over having the closed end point toward the ously affected by it source of interference, since reception is are those living notably poorer in the direction of the open within one or two end. miles of the trans- In the first place, a resonance curve was mitter. Beyond this taken on a wave trap. The trap used THE UX.DER SHADOW W/Z'S TOWERS distance, the signal was a General Radio instrument and is tests under the towers station at Bound interference great of WJZ strength has de- shown in Fig. 2. Many other commer- Shielded receivers Jersey. and other radio sets which were really creased to a point cially available are satis- selective could tune out the station even at this location types equally where it is a very factory. The resonance curve was taken simple matter to using an audibility meter. The curve, A series of articles concerned with eliminate it with any selective receiver. It therefore, does not represent any electrical interference from local stations there is, therefore, only within this comparatively quantities but is actually a direct indication is naturally forced into the discussion small area that any special arrangements of the audibility of the signal. From the must be used to eliminate the curve it is evident INthe question of super-power (so- signal. that within 20 kilocycles felt the need of called) and its effect on local reception. RADIO BROADCAST the audibility decreases to about 10 per This question has received a great deal obtaining some actual data on high power cent, of the original value, indicating that and its effect so a series of of publicity lately in the press and in radio on reception, the band of frequencies neutralized by the publications. In RADIO BROADCAST, not experiments were undertaken, designed trap only extended about 20 kilocycles on to it is to cut out many moons ago, Carl Dreher, writer of show whether possible either side of resonance. In order to "As the Broadcaster Sees It" took up interference when the receiver is located obtain this curve it was found necessary the cudgel for super-power; and stated the a comparatively short distance, say one or to use the trap conductively coupled, with case in this wise: "Everybody is increasing two miles, from the interfering trans- the entire coil of the wave trap in the power who has the money, because it is the mitter. antenna circuit as shown in Fig. 4. Taps next sound technical step." We are not The field tests by the technical staff of are provided for use when the trap is going to discuss the theoretical points that RADIO BROADCAST were made at a point inductively coupled to the antenna, but enter into a consideration of high power; about i^ miles from the transmitter of wjz if so connected, it was found impossible but are going to confine ourselves to the located near Bound Brook, New Jersey. to eliminate the signal. The same test was practical results of super-power. For, This station has a capacity of 40,000 watts, concludes Mr. Dreher, "After all, we can and during our tests was presumably talk ourselves dry and in the end the issue operating on full power. will be decided by performance." There were two major points to be de- It is generally agreed that high-power termined: stations should be located in the country 1. How successfully could the signal be as far from town as is any conveniently eliminated? so as to reduce to a minimum possible, 2. Did the high powered signals have any the number of affected. field persons The blanketing effect on the signals from other strength of a high frequency wave bears stations? an inverse relation to the distance from the HOW THE "HIGH-POWER" TESTS WERE MADE source (neglecting the effects of various kinds of absorption) so that the field tests were made on an ordinary strength rapidly decreases within a com- THEfour-tube unreflexed Roberts receiver small area around the trans- and in order to eliminate a wave paratively wjz, trap RADIO BROADCAST Photograph mitter. was used. There was unusual nothing FIG. 2 It is quite evident then, that if the about the receiver and it was operating on A wave trap manufactured by the General transmitter is located in the the an antenna a horizontal run of about country, having Radio Company. This unit is not only useful amount of trouble it causes will be com- 50 feet and a lead-in of about 30 feet. as a trap but is also an excellent wavemeter JUNE, 1926 CUTTING OUT THE LOCALS 139

1,800 company operating the station and the 1,600 public is, doubtless, and it 1,400 necessary, seems logical that the

1,200 operating company should take cogniz- 1,000 ance of the interfer- m ence which has been o 800 created by the operation of their station 600 and do whatever they can to help in the way 400 of supplying infor-

200 - mation, investigating complaints, etc. There are several factors contributing ft - O o O O to the opposition to CYCLES DIFFERENT FROM RESONANCE high-power. One of is the fact that FIG. 3 these started An audibility curve showing how the strength broadcasting of an interfering signal is decreased by the use on low power. Low of a wave trap power meant two RADIO BROADCAST Photograph APPLYING A WAVE TRAP things, first, that very PRACTICALLY made with several other traps including the sensitive receivers A wave trap in a home in Bound Brook, New Jersey, attached to a five- one-control set is successful in out not a mile Accuratune, made by the Mydar Radio were necessary in tube, tuning wjz away. The photograph was taken when one of the staff of RADIO BROADCAST and the Filtrola, manufactured order to obtain Company, recep- Laboratory visited Bound Brook to test the operation of wave traps in a by the All-American Radio Corporation. tion if the receiving locality where they are needed The major reason for using the General point was located at Radio instrument in taking the data con- any distance from the transmitter; and sec- disappeared and the only objectors left tained in this article was that it uses a ondly interference from near-by stations were those, who, with no acquaintance calibrated condenser, which was essential was not serious except in a very restricted with radio, felt that the interference could in making these measurements. After the area quite close to the station. The result not be eliminated. So we had letters to tests with the General Radio and other was that many receivers were made with newspapers, petitions to Congress, and a wave traps mentioned above, a home made no means of eliminating local interference. general rumpus all out of proportion to the trap was tried and results were quite sat- Consequently, the advent of high power importance of the question. There was isfactory in every way. A home made caused many listeners to raise a loud cry of talk of blanketing effect of high power and unit, very easy to build, is illustrated in protest because of the interference pro- so on. At the beginning a lot of us got Fig. 8. duced, while many others immediately excited and no one did anything. It is supposed by some that a high power settled down to the problem of its elimin- After the noise somewhat subsided it station would have a blanketing effect on ation and constructed wave traps. Op- became evident that the problem and its reception in the vicinity in that the exist- position from these individuals soon solution was not as serious as was first ence of very strong signals thought. The excitable in the ether would in some souls found out that by way or other neutralize the use of simple wave the signals from other sta- traps they could do what tions so as to make their some very sensitive re- reception very difficult. ceivers seemed unable to

I n our tests no such effects do. And so, with the in- could be noticed. WOR, stallation of this simple separated from wjz by ap- device, a great deal of the proximately 80 kilocycles, agitation subsided. could easily be tuned-in In the vicinity of New without any interference. York, most of the com- Broadcasting from a Phil- plaints were lodged against adelphia station located 60 wjz. If this station had times as far away as wjz, opened on some hot sum- and having only i per mer night, when the static cent, of the power could was strong it would have be tuned-in without diffi- been welcomed with open culty. arms by many of its now bitter We BLANKETING AND INTER- opponents. should realize the advan- FERENCE ISN *T NECESSARY of located near WITH HIGH-POWER tage being a powerful broadcaster, for THESE tests, we be- it is the one thing that lieve, show quite con- will make summer recep- RADIO BE DCAST Photograph clusively that a high power tion at all Now DIRECT HELP FOR THE LISTENER pleasant. station need not cause there is only one good B. S. McCutcheon showing a Bound Brook resident how to use a wave trap success- excessive interference. A way to get rid of static fully. Mr. McCutcheon's job is to investigate every letter of complaint by visiting certain amount of co- and that is to have the home of the complainant and studying the situation. He has been able to help enough operation between the the listener-in in 90 per cent, of the 900 cases he has investigated signal energy coming down 140 RADIO BROADCAST JUNE, 1926

tuned circuit it is not possible to obtain a filter with such a frequency characteristic. Fig. 6 shows how an actual unit differs from the hypothetical case of Fig.

5. With a low resistance circuit, a curve like A is obtained; if the Trap resistance is made ten times as Input To Receiver large, the characteristic changes to that of curve B. In taking these curves, the input voltage was constant so that the ratio of the currents at frequency / indicates considerable decrease in efficiency caused by high resistance units. Hence the import- well low resis- - ance of designed A tance circuits. Receiver Now, if the receiver is to be FIG. 7 selective, it must have a sharp A diagram of a radio-frequency amplifier which resonance curve but not too will increase the efficiency of many receivers sharp for, from the point of view of exact quality, a very high degree of selec- As selectivity was a measure of the tivity must not be attained, since that docs receiver's efficiency as a filter, so sensitivity not permit the equal transmission of all the is a measure of its efficiency in the amplifi- side bands of the carrier wave which carries cation and detection of radio frequency FIG. 4 the voice frequencies. Fulfilling this one energy. A receiver using several stages How the wave was con- trap and only requirement for selectivity of tuned radio frequency is an example of nected to obtain the curve in Fig. 3 namely, that the resonance curve of the sensitivity obtained by use of amplification receiver be sufficiently sharp has nothing and the regenerative detector is an excellent to drown through the antenna completely to do with sensitivity. example of sensitivity through the use of out any noise. an efficiency detector circuit. The radio- These remarks concerning high-power frequency amplification of a receiver is the consideration of were brought about by a ratio of the voltage on the grid of the de- of the problem at hand; the elimination tector to the voltage picked up by the interference. The first article of this series antenna and it is this ratio that determines in the RADIO BROADCAST appeared April the sensitivity. and described the construction and oper- ADDING A AMPLIFIER ation of wave traps, such as were used in RADIO-FREQUENCY the Bound Brook tests. is a comparatively simple THEREmethod both the HOW TO ATTAIN SELECTIVITY AND IN- whereby selectivity CREASED SENSITIVITY and sensitivity can be increased at the same FREQUENCY time, which involves the use of an additional TIOWEVER, a wave trap merely of tuned FIG. 5 stage radio-frequency amplifi- n functions to increase selectivity and cation. This can be An ideal resonance curve easily accomplished it is evident that it would be somewhat for a radio receiver in connection with practically any type better not to increase the only selectivity of receiver in use so that it affords an but also at the same time to increase the excellent method of increasing the efficiency of receiver. would sensitivity the This of a receiver. it to cut out the make possible interfering An excellent manufactured radio-fre- and also to receive from more signals signals quency unit designed for use in this mannet distant stations. We shall now describe is the Penetrola, made by the Walbert Man- a unit which will accomplish these two ufacturing Company of Chicago. 1 1 is pos- It should first be clear as to what things. sible to connect this unit to a receiver is meant and by selectivity sensitivity. without any changes whatsoever. The The selectivity of a receiver is a measure Penetrola is illustrated in Fig. 13. of its as a filter of electrical waves. efficiency A home-made radio-frequency unit In other words, the whole idea of "tuning" adapted for use in this connection is shown is so to adjust the electrical characteristics in Fig. 7. This design proved to be excel- of the tuning elements to reject all fre- lent from the standpoint of adaptability quencies except the desired one. The to existing receivers with a minimum completeness with which undesired fre- number of changes. The completed unit quencies are eliminated depends upon the is shown in Figs. 8 and 9. It was con- resistance of the tuned circuit. The lower structed in the Laboratory. this resistance is the better will be the The following notes are given for those selectivity. wishing to duplicate the RADIO BROAD- The filter for a broadcast receiver perfect CAST model. would have a characteristic like that of FREQUENCY The parts used in the model are as Fig. 5 which represents an ideal band-pass FIG. 6 follows: filter. It should be noted that the sides The reason for the use of low loss circuits. Curve are vertical so that all frequencies outside L,, General Radio Coil, D A is obtained from a low resistance tuned circuit, LI, Type 277 of the band a-b are completely attenu- and curve B from another circuit with ten times C Cardwell .oooj-mfd condenser. ated. Practically, with the single radio as much resistance Cn Hammarlund midget condenser JUNE, 1926 CUTTING OUT THE LOCALS 141

FIG. One of the diagrams in this Figure is the type of antenna connection used in your receiver. The diagram Fig. 1 1 shows the adaptation necessary to include an r. f. amplifier-wave trap.

I Amsco socket In wiring the unit, make all leads to the grid need be given. In order to adapt the Miscellaneous parts, wire, screws, binding posts, and plate as short as possible, otherwise it receiver to the unit, some slight change is etc. is apt to be difficult to control spurious necessary. i panel and cabinet j"n 8" oscillations. The actual circuit is very The antenna system of a receiver is I Rathbun dial simple and no other special instructions usually connected by one of the methods I Filament switch illustrated in The apparatus listed Fig. above need not neces- 8. In Fig. 1 1, we have sarily be used. Any revised these standard parts will circuits so as to in- give entirely satisfac- dicate what changes tory operation. are necessary in order to attach the Those wishing to radio am'- construct a home frequency made coil should plifier. Readers should determine adhere to the fol- what type of an- lowing specifica- tenna circuit is used tions: in their receiver and

L L 60 turn coil of then locate it in No. 22 wire on a Fig. 8. The num- tube. 25-inch Tap eral preceding the the coil at the 2ist RADIO BROADCAST notes given below turn from the fila- Photograph refers to 8 so ment end. FIG. 9 Fig. The left-hand shows a home made wave that can be used to eliminate that the notes con- LI 1 5 turn coil of No. picture trap 22 wire wound over interference. The right-hand picture shows a model of a radio-frequency amplifier cerned with any of the filament end of the circuits can the secondary. readily be found.

APPLYING THE UNIT (i) This is the TO YOUR RECEIVER simplest receiver to which to attach the location of r. f. amplifier Dis- THEthe various parts connect the antenna is shown clearly in and connect the an- Fig. 12 and no dif- tenna terminal of the

set to terminal No. i ficulty should be of the Then had with regard to amplifier. remove the the placement of ground terminal to bfnding units. If duplicate post No. 2. If an an- parts are purchased, RADIO BROADCAST Photograph tenna series condenser the of panel layout FIG. IO is used (indicated by Fig. 12 can be used. dotted lines in the The "Penetrola," a completely enclosed radio-frequency amplifier, which will greatly increase the sensitivity and selectivity of a receiver

ox o* o*o 2 -S

FIG. 1 1

The circuits of Fig. 10 revised so as to permit the use of a radio-frequency amplifier 142 RADIO BROADCAST JUNE, 1926

Ant Gnd. A Bt drawing) the connec- other end to terminal No. 2. The antenna KTO to Input tion to terminal No. I connection is of course removed from the second- p~| Receiver a a_ should be made from ary coil. the side of the con- (4) Practically the only method of adapting denser which connects the circuit to the amplifier is by removing the to the coil. variometer and substituting in its place a coil of (2) This circuit is the same type as in the former circuits. Revised, practically the same as it appears as in No. 4 Fig. 1 1.

No. i with the excep- (5) This circuit is very easily changed over.

tion that there is a Connect terminal No. i to the antenna terminal connection between on the receiver. Terminal No. 2 should connect the antenna coil and to the other end of the antenna coil. An optional

the secondary winding method is illustrated in Fig. 1 1 where the marked "a" on the antenna tuning condenser C has been shunted diagram. This connec- and connection made directly to the ground tion should be re- terminal. moved and then the circuit is a duplicate of After the necessary changes have been No. i. This connec- made, the batteries can be connected. tion must be removed Remove all the tubes before this is done in order to prevent so as to prevent damage in case an error short-circuiting the B has been made. When are sure battery. you every- is correct, the terminals (3) In order to thing battery the adapt this circuit to on new amplifier unit should be con- the new unit, it is nec- nected to the corresponding terminals on essary to add a new the receiver. Finally, the antenna and winding to the antenna ground should be connected to the correct coil. This winding binding posts. The receiver and amplifier should consist of 15 can now be turned on Fil.Sw. and the set operated turns of No. 22 wire in a normal fashion. The Rathbun dial wound over the fila- will cause the ment end of the sec- straight-line capacity condenser to tune as it were a ondary winding. One though straight- FIG. 12 end of the coil would line frequency unit so that all stations will Apparatus layout of the radio-frequency amplifier then be connected to be evenly separated over the entire 200 Refer to for the schematic of this unit Fig. 7 diagram terminal No. i and the degrees of the dial.

ADIO BROADCAST Photograph

FIG. 13 Another photograph of the amplifier illustrated in Fig. 8 A Simple Set Tester for the Home

THE TESTER IS HERE SHOWN IN USE IN THE "RADIO BROADCAST LABORATORY

An Easily Constructed and Inexpensive Tester for the Home Experimenter Which Should Simplify Testing of Circuits and Receivers Its Construction, Operation, and Applications By SID GOODWIN Radio Editor, Portland, Oregon, "Telegram"

job of trouble shooting in any upon the individual's experience and in- a receiver from which one of the tubes has piece of radio apparatus is not at telligence to know where and what to look been removed it is possibe to note the all pleasant, but after the novelty for. To build the trouble shooter described action of the various circuits by flipping the THEof building receiver after receiver here no special effort on the switches on the front of the trouble shooter requires part has worn off, the home constructor will of the constructor except that he be able panel. find that the addition to his equipment of to understand the simple .wiring and as- In this way it may be determined a simple trouble shooting device will be sembly of the instrument itself. Merely whether or not the grid circuit is open, well worth a few hours spent in constructing by placing a prepared plug in the socket of whether or not the plate circuit is open, or it. it may be observed whether the B battery Besides preventing a ruffled temper, this applied to the socket is of incorrect polar- The Tester Will Do unit expedites the matter of locating ,,\Vhat ity. Filament volt-age may be determined trouble in radio receivers means of and of the various batteries in- by 1. Show an open grid circuit. polarities several throw-over switches and a triple- 2. Show an open plate circuit. dicated. Once an incorrect reading is ob- scale voltmeter. Parts that are defective 3. Indicate the voltage applied to each tube tained, it is plain that trouble exists in filament. may be located quite easily and new parts, that part of the circuit in which the 4. Indicate the plate voltage for each tube before in f switches are being placed a receiver, may be o a receiver. connected. tested to determine whether or not there 5. Test fixed and variable condensers for The plug, to which is attached four flex- short circuits. are any defects in the manufacture. ible leads, each about four feet long, may 6. Test coils for open circuits. Usually when a receiver will not work, be made from parts found in the junk box. 7. Test audio transformers for open circuits. the constructor first checks his and A round of wood of the diameter of wiring 8. Test phones and loud speakers for open piece then after that inspects each individual circuits and in so doing, will guide you the tube socket shell may be smoothed over piece of apparatus employed in the as- in locating the faults in your radio re- with sand paper; machine screws fastened ceiver. sembly. Much depends in such a test in the base and holes drilled from the top 144 RADIO BROADCAST JUNE, 1926

down to the tops of the screws are enough tor. The several photographs will serve and wired in accordance with the circuit to make connection to the leads. Or better as a to those who wish to guide duplicate diagram, Fig. 4, which, by the way, is a yet, if an old tube is handy, the glass may exactly the construction described here. rear view of the trouble shooter, the de- After the be broken away and removed entirely from parts have been assembled vice may be put into operation. the shell and the leads soldered to the prongs on the inside of HOW TO OPERATE THE TESTER the shell. A wooden plug to two fit inside the shell may be pre- top pin jacks THEmarkedTl Test, minus and pared to serve as a handle. are connected to A socket adapter will serve plus, directly the volt-meter so that a read- the purpose of a plug admir- ing on the intermediate scale ably. The leads attached to is obtained when a -volt the prongs may be led up 45 block of B is added to through a central hole bored battery the circuit in which is included in the wooden handle part of the of unde* the plug. piece apparatus test. This is shown in The voltmeter employed in Fig. 3. the trouble shooter constructed Where it is desired to test for in RADIO BROADCAST Labora- continuity of circuit, a reading of the voltmeter will indicate tory is a Jewell, triple range, a circuit. In case a No. 88160, type 55, having complete three scales as follows: 0-8 condenser is to be tested then no is desired since the volts, 0-80 volts, 0-160 volts. reading condenser itself That employed in the model presents an circuit to the flow of constructed by the author is open direct current from the bat- also a triple range type as fol- a of lows 0-7.5 volts, 0-30 volts, tery. By inserting pair in the circuit 0-120 volts. The former is phones it may be noted whether or not the undoubtedly better since it condenser is or allows readings of voltages in noisy leaky. The leads from the excess of 135 which is often plug, are connected to their re- used in audio amplifier circuits. spective pin jacks, namely minus A and Two anti-capacity switches Grid, Plate, plus A. The of the type manufactured by pin jack marked B the Federal bear- battery connects by the fifth Company, BROADCAST Photograph flexible lead to the ing the number I424W, are FIG. high side of the B satisfactory as the controls The front or voltage battery. panel view of the tester shows the placement of the switches, pin which are larUs anrl fli n-CH/ifi-h^c flic ri nol civ a ic fi" v i *->" M. ,,,.-,, ,1 1 .-,,,,-,,,- : Before the in operated from the jacks and flip-switches. The panel size is 8" x 10". No panel layout is inserting plug as the panel front to connect the shown, each constructor may approximate the layout shown above to con- socket of a radio re- form with the parts he chooses to employ the two meter into the various parts ceiver, anti-capacity of the circuit under test. switches should be in a neutral Then after Six pin jacks are arranged position. the in hexagonal form, and an- plug is inserted, pushing the lever of the left switch other pin jack is placed at the upward will center. These are for making produce a reading connection with the flexible on the voltmeter which by cords which lead to the test means of its scale adjuster has been turned to the clips, and thespecially prepared high plug which fits into the socket scale reading. Such a con- .of a radio receiver. dition indicates a continuous 1 All these units are mounted circuit for the grid circuit part of the tube on a panel 8x 10 inches, which circuit under test. if desired, may be fastened When this same lever is pushed to a box or base. downward, the plate circuit is' thrown into the meter cir- The materials required for the construction are as fol- cuit, and should there be no lows: reading; obviously an "open" is present. 1 Panel 8 x 10 inches. The switch at the right 2 Anti-capacity switches (Federal is for measuring A and B No. I424W). voltages. By shifting the 7 Pin Jacks. position of the clip of the 7 Terminal Pins. lead emanating from the B i Voltmeter. Triple scale (Jewell battery tip jack, the tyP6 55 or 55-88160). voltage of individual sections of the I Plug constructed as described 28 feet flexible lead wire, bus B batteries may be measured. bar, etc. It should be remembered that no voltage should be measured No panel layout is necessary which is calculated or one RADIO BROADCAST Photograph since the for the var- position FIG. 2 suspects to be higher than the ious be to parts may changed rear view scale of the meter A of the tester discloses the fact that simple point-to-point employed. suit the of the construe- connections fancy make the wiring of the device not difficult, and easy to check When filament voltage is JUNE, 1926 A SIMPLE SET TESTER FOR THE HOME "LAB" 145

front of the tester is panel thrown to the Neutral "Grid" position, it indicates, if a reading is obtained, that not only is the tuner secondary winding continuous but that the secondary of the audio reflex transformer is unbroken. Since the C battery in this part of the circuit is so connected that its voltage is added to that of the battery employed to obtain Rear of a it is multi-reading, obvious that at the Switch Down same time an indication is obtained which will tell whether or not the C FIG. 5 The three battery is in a top notch condition. positions which the flip-switches may assume. When the handle is Fixed Condenser When the switch is thrown to the pressed upward, the cam arrangement forces the blades downward under Test circuit, the of the plate continuity plate into contact with the lower fixed blades of the coil is manifest. switch and when FIG. 3 winding pushed downward, the action the test in the detector is just the opposite. When the handle is in a A picture-diagram of the method employed to test Inserting plug horizontal position then no contact results. condensers with the aid of the pin jacks labeled socket, the grid leak and condenser must "test." and numer- Coils, transformers, phones, be bridged by a clip or other connection ous other radio articles be tested in a similar can be may to short it out of the circuit before a reading obtained for the grid circuit. fashion In the plate circuit, the continuity of the circuit will be evident for both measured it is that the possible the tickler coil and the primary meter will read backward. This of the audio reflex transformer be corrected may by reversing when a reading is obtained. the of the two leads position A glance at Fig. 6 will show in the terminating minus and how the meter of the tester is A plus tip-jacks. thrown into the grid or plate When the plug is inserted in circuit. thedetector tube no read- socket, When the test terminals of the ing will occur when the left hand instrument are used, a pair of switch is tilted to read upward phones may be inserted in a of circuit for the continuity grid series circuit, and an additional circuit. This is because the grid check will result where it is not condenser produces a virtual FIG. 6 always possible, because of the circuit, and it is open necessary Here at the left is how the circuit looks when the switch on the front of high resistance of some radio to short it out with a or the is thrown to the "Grid" At the the circuit in- clip panel position. right apparatus, to obtain a reading of wire to obtain a dicates the connections when the same switch is thrown to the "plate" piece reading. on the voltmeter. The A and B switch causes a of the of When the This trouble shooter will position. merely reading voltage only circuit either filament or plate batteries under test is satisfactory, indicate the circuit in which a click will be heard in the there is error. After this mani- phones. festation, it is to con- necessary Another use for the test ter- duct a minute inspection of minals is to determine the ap- that part of the circuit indicated proximate resistances of various by the test as defective- actually units by a voltage drop calcula- to locate the source of trouble. tion. We will suppose that it is Considering that without such desired to determine the resis- an instrument, the radio set tance of a large coil such as the builder must slowly check and secondary of an audio trans- inspect each part of a wired re- former. Several things must be ceiver, with the attendant pos- known. First, by reading the sibilities of incorrect checking, voltmeter, determine the exact the device described here is one value of the voltage source in that should grace the equipment volts. Then determine the vol- cabinet of all dyed-in-the-wool tage when the unknown resis- experimenters because of its tance is included in the circuit. very evident time-saving quali- J With these values, the formula ties. The total cost of the tester ,9- - Rv ( E B By) should not exceed $20, and may RX = be m- E may run less if the constructor is V able to use some parts he has voked. Here RX is the un- already on hand. known resistance, RV is the re- Suppose that an actual test sistance of the voltmeter, which is to be made of the original may usually be obtained from two-tube Roberts receiver, the manufacturer; EB is the which employs a stage of tuned battery or source voltage; and neutralized radio frequency am- EV is the voltage reading on the plification and a regenerative voltmeter. An audio trans- detector whose output is re- former will often seem satisfac- flexed through the first tube to when tested for FIG. 4 tory continuity be amplified at audio frequency. although a short in its windings The wiring diagram for the tester as viewed from the rear. Bus-bar, When the is inserted in the exists. A test of its resistance plug covered with spaghetti tubing, will make your tester look, as far as wiring first socket and the switch on the is considered, like this circuit diagram, presenting a pleasing appearance will, however, prove conclusive. NEW APPARATUS

A Short Description of Some of the Radio Parts and Accessories Which Have Been Tested and Approved by the "Radio Broadcast" Laboratory

is "Half [CANNING the advertising pages of a serviceable device which will dissipate the the battery "Full," -Full," or a popular radio magazine reminds electrical charges that might collect in the "Low." us of our childhood days when, at antenna. A lightning arrester of an ap- From the Richard Davis Company we Christmas, we gazed into the tinsel proved type is a good investment, since it have received a combined loop and Tim- bedecked window, brightly illuminated, makes of the antenna system a very effi- mons cone arranged in a very attractive of the largest toy emporium on Main cient protection against lightning. The style. It is possible to rotate the loop on Street. We were amazed at the multipli- second device received from this company two axes thereby adjusting it to the actual city of the goods offered us. And so with is a charging resistor control which may plane of the wave front of the intercepted the modern radio fan. He cannot help but be used for regulating, by means of a radio wave. In short, this device combines notice the many new and distinctive radio calibrated resistance, the rate of trickle both the input and output units of a re- devices set out for his scrutiny and deliber- charge of A storage batteries, and receiver the loop and speaker. ation. duces this function to the mere turning of The man building his own plate-supply To list and illustrate all, or even a goodly a switch. unit will find the Tobe Deutschmann B portion of such devices, is rather impossible Cardwell's new taper plate condenser is Block of especial interest. Gathered into in such a limited space, but a few that have a distinctive contribution to the radio one can are all the condensers that are nec- been tested and approved by the RADIO market. It is different from most of the essary for the filter and by-pass circuits of BROADCAST Laboratory are depicted here. s.l.f. condensers in that the straight line a plate-supply unit. Appropriate binding Manufacturers, it can easily be seen, ar-e curve is obtained by the use of tapered posts afford means for connections to two bent on simplifying the operation of the plates which vary the air space between i-mfd. sections, two 2-mfd. sections, and radio receiver, and at the same time there the rotor and stator plates as the former is one 8-mfd. section. is a very evident trend toward beautifying rotated, without employing the long, slender The three gang condenser of .ooo35-mfd. the appearance of the complete radio in- plates as is common with most s.l.f. con- capacity for tuning three circuits simulta- stallation both inside and outside the re- densers. neously, is manufactured by the United Sci- ceiver cabinet. Two types of meters offer to the labora- entifiic Laboratories, Inc. Novel vernier The Acme Trickle Charger, shown below, tory man and home radio enthusiast a adjustments on two sets of the stator makes possible the recharging of one's means of checking up on the conditions of plates make it possible to compensate for storage battery after the set is switched off his batteries, the A, B, or C. The Hoyt slight differences between the coils in a for the night. It is a compact instrument meter, shown on the top of the first page, is three-circuit receiver. measuring only about 5 x 3^ x 5! inches, of novel pattern. With it, five different The Walbert .ooo35-mfd. variable con- and operates from no and 115 volts a. c. sets of readings may be taken by merely denser indicates a tendency prevalent rate is The charging .5 ampere. turning the meter in its support for each among manufacturers toward dust proof For the home constructor interested in individual range. One connection to the enclosed condensers. Considering that the super-heterodyne, the St. James 280 kc. meter is common, while the second connec- much can happen in the way of noise pro- intermediate-frequency amplifying trans- tion goes to one or other of the remaining duction caused by dusty, dirty plates in a formers will offer something brand new binding posts, depending upon which read- variable condenser, this is a step to be and of decided interest. The transformer ing is desired. The possible readings are commended. primary and secondary coils, which are of as follows: 0-75 volts; 0-150 volts; 0-7.5 Those fans who have contemplated the the honeycomb type, are enclosed in an air amperes; 0-15 milliamps.; and 0-75 milli- purchase of a Bosch cone loud speaker evacuated glass tube resembling a radio amps. will be interested to know that the Bosch vacuum tube in a socket. The Cellokay meter has been designed Magneto Company are putting out one the L. S. From Brach Company come for telling the actual state of the A battery of their cones with a wicker work front to two fine additions to radio equipment. when its terminals are applied across the harmonize with summer porch furnishings. Brach The lightning arrester will appeal, latter's posts. A direct reading is ob- The Laboratory has not been given the especially for summer use, to all who desire tained which tells at a glance whether opportunity to test the Bosch cone.

Photographs by RADIO BROADCAST THE ACME TRICKLE AN R. F. TRANS- CHARGER BRACH'S LIGHTNING ARRESTER FORMER JUNE, 1926 NEW APPARATUS 147

THE NEW BOSCH CONE A DUST-PROOF CONDENSER WALBERT'S

Photographs by RADIO-BROADCAST CARDWELL'S TAPER PLATE CONDENSER

HOYT s "ROTARY METER A COMBINED LOOP AND TIMMONS CONE

THE TOBE DEUTSCHMANN B BLOCK

THE CELLOKAY METER A TRIPLE GANG CONDENSER It is a of the United Scientific Lab- By connecting it across the A battery, the production oratories S. To for needle will indicate the condition of the battery (U. L.). compensate slight differences in the coils are by pointing to either "Low," "Half." or "Full."' employed (which matched as as two To the right, Brach's charging control suit- naturally closely possible), of stator have verniers able for trickle chargers groups plates How Radio Wire Lines are Equalized

Technical Practice in England and America Details of the Operation of American Broadcasting Stations The Role of the Engineer in Radio Comment of Interest to Broadcasters and the Public "AS THE BROADCASTER SEES IT" By CARL DREHER

Drawings by Stuart Hay

elementary theory of loss of In one instance a 225-mile circuit be- equalizer disclosed in an article on "The high frequencies in audio trans- tween two cities, almost all open wire, has Design of a Broadcasting Station," by mission over wire lines and cables, a "cable equivalent" of 12 miles. That is, A. G. D. West, Assistant Chief Engineer THEand simple methods of correction this actual 225-mile run of open wire cor- of the British Broadcasting Company, or equalization were discussed in the May responds to 12 miles of standard cable, published in the Year Book of Wireless RADIO BROADCAST. The treatment of with a resistance of 88 ohms and capacity Telegraphy and Telephony (The Wireless this subject will now be continued with a of 0.054 microfarads per loop mile, and the description of a number of types of equaliz- 12 miles of standard cable be used may 0-200 Ohms ers in common use in broadcasting. as its equivalent in all calculations. An- First, however, it should be understood other circuit between the two cities contains that in line correction, as in politics, there 23 physical miles of cable, in three sections, is no universal remedy or panacea. Each the rest being open wire. This circuit 004-0.2 Mfd. case requires individual treatment, depend- has a cable equivalent of 40 miles, and is ing on the nature and length of the circuit, correspondingly harder to equalize. The terminal apparatus, and transmission re- type of cable is also a factor. I n the second quirements. Open wire lines, consisting of case cited above, the cable sections are FIG. 3 wires strung on crossarms fastened to poles, what is known as five-pair, 14 gauge paper Shunt equalizer for radio wire lines require the least degree of correction, since lead cable, which means that there are common in the United States the capacity is relatively low. Such lines, of course, are not as reliable in sleet or wind World, London). This is de- as aerial or subterranean cables, in which a signed to equalize between 50 large number of pairs are bunched and en- and 8000 cycles per second, cased in some suitable protective covering, and represents English prac- such as lead, or fabrics tice in this field. The insulating possess- Input range ing the requisite mechanical strength. On of the variables is not given. the other hand, a cable, with the two sides Fig. 2 shows a correcting of a pair in contact (insulation to insulation, amplifier designed by Mr. Julius that is) and also close to other conductors Weinberger to give a character- has a much higher capacity per unit istic, flat up to 4000 cycles, length than an open wire pair with the and rising from 4000 to 10,000 two wires several inches or is in separated by alizing Circuit cycles. This described Mr. feet of air. As a result, the attenuation, Weinberger's "Broadcast Trans- or loss of energy, is much greater for a FIG 2 mitting Stations of the Radio given distance, and likewise the loss of Corporation of America," Pro- The Weinberger amplifier "flat" 104000 cy- is not as corrected. the Institute higher frequencies easily cles and "rising" from 4000 to 10,000 cycles ceedings of of Radio Engineers Vol. XII, No. five pairs of wires, size 6, Dec., 1924. The rising characteristic No. 14 B. & S. copper, the is derived from the resonant circuit LC, B Bat wires insulated from each tuned to 10,000 cycles, with a capacity C other by paper covering, with equaling 0.00025 m fd. a lead sheath over all. The simple shunt equalizer used gen- The only type of cable erally in this country is shown in Fig. 3. adaptable to broadcasting use A typical range of constants is given. The is "paired" cable, in which theory of operation is simple. The coil- the two wires of a circuit condenser circuit is resonant to some are twisted, and sometimes high audio frequency, say 5000 cycles. shielded, to avoid inductive Across its terminals it presents a very high interference from other cir- impedance to currents of this order of fre- A Bat cuit's. "Straight-laid" cable, quency, so that it has little effect on their in which the circuits are not strength and they pass on undiminished to isolated in this way, cannot the input equipment. For currents of be used for audio transmis- low frequency, the coil L is practically a -'I'll'W sion. Even a short section short circuit. The combination is there- Bias Bat will ruin an otherwise quiet fore an equalizer, dropping out the ex- FIG. I line. cess of low notes and retaining the high. British practise in line equalizing Fig. i shows a type of The scries resistance R regulates the de- 149 JUNE, 1926 TECHNICAL NEWS OF THE STUDIOS

is not gree of equalization. When the entire cago, printed resistance is out, leaving the shunt circuit to show the two bridged directly across the line, equali- pretty girls and zation is at a maximum. So is the loss in Frank Westphal, the director and signal strength, which must be compen- studio sated for by amplification. announcer, but to give technically inclined readers an op- Among the Broadcasters portunity to observe the method used to WKRC reduce the reverber- ation time of the sketch shows the new studio studio. Instead of layout of WKRC of Cincinnati, in the deadening the room THEnorth wing of the new Hotel Alms. by means of drapes, The 125-foot towers are on the roof of an equivalent acou- the building. It is said that the arrange- stic effect has been ment shown was not decided on until secured by means of two of the officials of the staff had visited the solid absorbing twenty-six broadcasting stations in the material used for the United States. walls. The space occupied by the WKRC layout But who put the microphone on ALMS PLACE the piano? We will wager that none of the operators were CONCERT STUDIO around when

24'-6"x 29'- 3" that photograph was posed. ANNOUNCERS RM. 6'x8'-~ WBAL

are next YOUinvited to REAR STUDIO CONTROL RECEPTION ROOM gaze on the VIEW, studio control PANELS WBAL, BALTIMORE 30'-6" x 34'- 9" panels (rear view) of WBAL, Baltimore, Mary- WEAF land. Apparently not all the equipment was in when this photograph of the best known regular features ONE is NEW STUDIOS was taken. There is enough, how- on the air the Sunday night Capitol IN ever, to enable you to understand Theatre broadcast through WEAF, New ALMS THE HOTEL its chain. and FOR why a broadcasting station gets York and The smooth per- WKRC out of order once in a while. fectly controlled job invariably turned CINCINNATI.OH10

is about 3600 square feet. This area includes a large orchestration studio, solo studio, control room for the studio director and announcer, a separate operating control office, a private office for the studio director and engineer, a promenade, artists' lounge room, and a large reception hall. Both studios and the announcer's control office are glass-enclosed to permit visitors to watch the broadcasting. The ceilings of both studios are to be sound-proofed with felt. The walls will be constructed of double thicknesses of sound insulating material, so that each studio will be effectively isolated. The finish will be white, and the acoustic composition used will give the effect of blocks of caen stone. Italian period furniture, suitable draperies and paintings will complete the arrangement.

photograph of the new down- OURtown studio of WENR, operated by the Ail-American Radio Corporation, located in the Kimball Hall Building, Chi- A NEW STUDIO OF WENR, CHICAGO WHICH HAS A NOVEL WALL TREATMENT 150 RADIO BROADCAST JUNE, 1906

said they were engineers, to say that he was an engineer. If he was given the title of Chief Engineer, then all doubt was dispelled. The man was a genius he frequently said so himself and that his words dripped with wisdom was proved by the fact that he always spoke in such intricate and technical terms that the promotors of the enterprise could not make head or tail of what he said. All that remained was to put his masterpiece into a fancy box and wait for the money to roll in. ... Sometimes the creditors have received as much as twenty cents on the dollar. In this day of high pressure salesmen, well nourished advertising agencies, fifty- thousand-a-year executives, scientific management, expert industrial prophets, and all modern improvements, it is well to remember that our little radio world rests on the shoulders of only one Atlas, the engineer. Or, if you prefer Biblical to mythological figures, do you remember the "HE WAS A GENIUS HE FREQUENTLY SAID SO HIMSELF injunction to build your house upon a rock? I f so, you have a better memory than many out is no accident. One of the reasons, put on the air simultaneously in any vol- of the radio set manufacturers whose stock we are told, is that two of the control ume proportion desired. issues dropped from the twenty dollar to engineers assigned to cover the evening the fifty cent class during 1925. Look into program listen to the Sunday afternoon The Role of the Engineer in Radio the cause of these sad declines, and you performance in company with the assistant will find them many and various, but there conductor of the theatre, taking notes I were entirely ignorant of radio is one factor which turns up in seventyifive in a technical wanted cent, all and is or which later guide them in producing a IFconditions, sense, per of wrecks, that poor first-class of work in transmission. to a set, and had mediocre The started piece buy good receiving engineering. thing It may also be of interest to consider no means of getting expert counsel, 1 wrong, and it would be a miracle if it had the amount of equipment tied up whenever should adopt the following curious pro- ended right. And miracles occur in hagio- the big duck, WEAF, and all the little cedure. Instead of listening to salesmen, logy, seldom in radio. ducklings, to the number of about fifteen, who, in my unprepared state, would prob- What, then, is this engineer, whose horn with their are connected together by wire lines. Ac- ably merely befuddle me talk, I blow so loudly? It has been said that an cording to Mr. George F. McClelland, or reading advertisements, which nearly engineer is a man who can do with one Manager of Broadcasting for WEAF, 9300 always start with the claim that the set horsepower what any fool can do with two; miles of wire are used to carry an important advertised is the eighth wonder of the and that is not a bad definition. Going program from the Atlantic coast to stations world, I should try to find out what per- back a step, we find that this efficiency east of the Missouri River, from Minne- centage of their gross income various manu- arises from superior quantitative know- apolis on the north to St. Louis on the facturers devote to research. When I ledge. The engineer knows definitely south. The currents travel through under- had discovered the one with the highest where he "is at" and where he wants to go. ground circuits and over 124,000 telephone ratio in that regard, I should look over a But so does a shop-foreman. Going back poles. The telephone lines, as originally list of his sets, buy the most expensive another step, it appears that the engineer's designed and installed, were intended only I could afford, and let it go at that. I proficiency rests on the organized body of for transmission of the essential frequencies might not end up with the best receiver 1 technical knowledge handed down to him of speech. The lines used for broadcast could buy for the money, but I rather through the various sciences from which his transmission must be equalized over a far think I would. Neglecting all the other art is derived. He knows his underlying greater range, in order that natural speech factors involved, the single consideration I physical theory, is able to express it mathe- and music may be delivered to the various have suggested would probably set one on matically, that is, succinctly, exactly, and stations on the chain. About one hundred the right path. generally, to confirm it by measurement, men cover the transmission, not only in The fact is that in radio, as in every other and finally to apply it practically to his the broadcasting stations themselves, but field, one is not apt to get something for machine. The engineer is to the cut-and- at twenty-four repeater stations along the nothing. And progress must be bought try set constructor what Oscar of the lines, where the audio currents are boosted like everything else. One manufacturer Waldorf is to a chef in a hash-house. in order to maintain proper quality and turns out a better product than another, The necessity for design and production margin over noise. as a rule, because he spends more in finding engineers is obvious, since they must be out how to make his machines superior. depended on to get out the product. The WHT It is really astonishing how many radio department which is more likely to be ne- manufacturers have gone into production glected is that of research and development. THROUGH Reeve O. Strock, the chief on a formidable scale, advertised exten- Instead of parting with the necessary cash engineer, WHT reports the installation sively, sent out an army of salesmen, and for a development division, some short of a "mixing panel", a device such as invested a gold-mine in the whole structure, sighted executives think they can get away was described in the April, 1926, RADIO when they really had nothing to sell. The with it by imitating their competitors. BROADCAST, to secure greater flexibility in product itself was the last thing they This has two disadvantages. One is that balancing musical ensembles. The report thought about. A radio receiver, to them, the competitors may not be worth imi- does not give much in the way of circuit was a radio receiver. An engineer was tating. The other is that the copying firm details, but it is stated that five studio anybody who said he was an engineer is always a year or so behind the copied. microphones and all incoming lines may be and could get a few other people, who also The proper procedure is to originate when JUNE, 1926 THE IMPORTANCE OF THE ENGINEER 151 one can and to adapt good ideas derived installed at the hotel, it was impos- "Please Send Up a Wire" from competing sets, when expedient, and sible to test the lay-out until a few hours as far as business ethics will allow. All before the dinner was to start. Then, to time ago, in this dizzy de- manufacturers an on the consternation of the com- of keep eye competing everyone, SOMEpartment an otherwise respec- sets, and know their good and bad points bination of public address and broadcasting table publication, I wrote a skit quite as well as they know the strength station audio amplifiers howled lamentably entitled, "The Laying of the Lines." and weakness of their own equipment. as soon as the connections were made. This opus was my burlesque conception That is, all manufacturers who are not The diagnosis was simple coupling be- of a young woman radio critic's idea of asleep, and in industry, as when one is freez- tween the pick-up microphones and the remote control, derived from a paragraph ing, sleep is death. If you walk into loud speakers in the banquet hall. The written by the fair one (since departed the laboratory of a manufacturer of loud tables were all set up, the speakers' plat- from the radio ranks), in which she gave it speakers, you will find every model of loud form had been placed, nothing remained as her opinion that the lines between New speaker on the market, some intact and but to bring on the food. But without York and Schenectady must have been some taken apart. Furthermore, there the public address and radio service the "carelessly laid" on one occasion when will be characteristic curves of all these banquet would have been, as the boys in they became noisy during a concert. instruments, showing how some of them the shipping room say, a flop. What was to Pouncing on this phrase, I wrote a piece lose the low frequencies, some the high, be done? It was a problem that had to be in which I pictured myself as "laying the and some both, and depicting the various solved in a hurry. One of the engineers lines" by rushing up the east bank of the humps and troughs which make them what looked around in the annoying,~raminative Hudson with a roll of twisted pair under they are. But the enterprising manufac- way these bipeds have in such situations. my arm. One must write about some- turer and his engineers do not spend much He observed a small balcony, which he thing. time chuckling over the faults of competing inspected thoughtfully. He went under Extravagant? Absurd? Even so. And makes; they try, rather, to evolve some- it and clapped his hands. He went back yet it was brought home to me, the other thing superior to anything hitherto known, into the middle of the room and clapped day, that whatever nonsense one writes, and to surpass themselves as well as their them some more. He directed an assistant it will be only a little more foolish than the rivals. And this holds for all the numerous to stand under the balcony and slap his sober thoughts in some people's heads. parts and complete sets on the market; palms together enthusiastically, while the Attend, then, to a true story. in every case the firms interested fall into first engineer stood at the far end of the A movie actor, nationally famous and two main classes: those who strive for hall and listened. He then had a micro- fabulously rich, had finished a new picture. improvement and those who are satisfied phone placed under the balcony. The For the sake of the publicity, the producer to copy the leaders. The former class assistant spoke to it. The system repro- arranged to broadcast some scenes from the " is also found to be soundly financed, while duced without howling. If the speakers' photoplay, with a musical accompaniment, the camp-followers generally skate on table is placed in the lee of that balcony," and to add to the interest, the star was to thin ice. Good research is one of the remarked the engineer, "you will get public speak from the studio to the radio audi- elements of sound financing; it is insurance address service. Otherwise not." And ence. against dropping behind in the race for immediately all the king's horses and all The arrangements having been made technical supremacy, which, in the last the king's men were set to moving the in the usual manner, and the event sche- analysis, determines profits. speakers' table under the balcony, and duled for a certain evening, a telephone Sound engineering is as important in the banquet was run off successfully. The call was received at the broadcasting development and operation of broadcasting incident was not an unusual one. In the station on the afternoon of that day from a stations as in the manufacture of receiving last analysis, if the engineer's part of the third assistant secretary of the cinema equipment. The two fields are analogous, show is sick, the whole show is sick. If celebrity. The substance of it was that development having its place in each, fol- he crashes, all is lost. He is the founda- Mr. X desired to attend a prize-fight in lowed by production in one case and tion and the framework. Let the elegant Two Hundred and Twelfth Street (about operation in the other. There has never gentlemen in the superstructure remember nine miles from the studio) that evening, been a first class broadcasting station that. and would it not be possible to rush a wire without a first class development division behind it. If you see a station that remains unchanged from year to year, all you may safely conclude is that it may have been a good station once. It is not only a matter of apparatus, but also of sound methods in operation. Tests and pro- cedures must be carefully planned or a smooth performance on the air need not even be hoped for. If the engineering is unsound, no amount of brilliant program work will make up for that weakness. An instance: a very important dinner was to be broadcast. In addition to the speakers at the banquet, it was necessary to furnish public address service in the banquet hall on the entire output of the broadcasting station. That is, programs from other cities were to be broadcast and simultaneously made available through the public address system to the diners. The best method of handling this was to feed the public address system continuously from the control room amplifiers of the station. As a new amplifier system was being "WOULDN'T IT BE POSSIBLE TO RUSH A WIRE UP THERE?" 152 RADIO BROADCAST JUNE, 1926

which it up there, so that Mr. Atlantic, X could broadcast sometimes worked as without missing his far east as Gibraltar. diversion? The wavelength was Yes, truth will beat somewhere up in the fiction any day. The two thousands, about name of the miracle- 2800, if I recollect, and each it seeking star will be night sent several given on application thousand to any United States words of press, start- Senator. ing around 8 P. M., at

about 1 2 words a min- news Memoirs of a ute, including items, baseball scores, Radio Engineer. and other items of

XII interest. I was able to get a very readable ACCOUNT signal from WSL, and so far has been copied him every MY In this of urban ama- night. way teur radio. I I had the baseball did, "MY MAGAZINES SERVED SOMEWHAT LIKE indeed, take radio scores every night at A LOVER'S PICTURE OF HIS SWEETHEART" with me on my vaca- about ten o'clock, tions, but only in when nobody else in the form of magazines on the subject, of the free end of the wire must have been Bushnellsville knew them until noon the manufacturers' catalogues, and the like. around 40 feet, and it was practically following day, Then the mail, including As I was going to school, I enjoyed parallel to the side of the hill on which newspapers, arrived by stage coach, the a vacation period of some two months the cottage stood, so that it had a slope of village being four miles from the nearest each summer, which was spent in the thirty degrees or so, reckoning from the railroad station. Most of the natives Catskills, as a rule. The radio reading horizontal, and fell into the class of sloping, knew nothing about radio, and believed matter which I took away with me served or, as they were then sometimes called, that I secured the ball scores by some sort somewhat like a lover's picture of his "compromise" antennas. The lower end of necromancy. sweetheart, and had the same limitations. of the wire was supported by a tree about Sayville was the only station I could get After a month's absence from my receiving thirty feet high, and thence the lead-in reliably. Time signals from NAA, Arling- set, I usually felt a great longing to hear dropped vertically to my window. ton, were weak, although generally audible actual signals again, and there were several Bushnellsville is practically in the center at the 10 P. M. transmission. On 600 years when I returned to the city a week or of the Catskill range, about 120 miles meters I heard a few ships, and wsc, the so sooner than was necessary, because my northwest of New York City, with moun- Marconi station at Siasconsett, Massachu- craving for dots and dashes could no longer tains for thirty miles and more in every setts. None of the New York city stations be restrained. A curious mania, and one direction. The elevation is 1600 feet ever let out a peep as far as Bushnellsville which 1 scarcely comprehend to-day, al- above sea level, and the tops of the moun- was concerned. Mountain reception on though I remember it clearly enough. tains rise 1400 feet higher. Under such a crystal was a different proposition from Presumably what killed it was an overdose unfavorable receiving conditions I had my city experiences, relatively close to of dots and dashes when I went into radio little hope of picking up daylight signals, WNT, NAH, and WCG. But, even as con- professionally. and I never did. 1 listened often, but ditions were more difficult, the thrill of In 1913, however, my family occupied heard only static crashes, and plenty of being in touch with the outside world was a cottage in Bushnellsville, Greene County, them, because scarcely a day passed in greater. There was a peculiar incongruity New York, and my receiving equipment this valley without a lightning storm of between the green clad hills and my an- went up there with me. It consisted of a greater or lesser severity. But what I tenna, and the mastery of space which radio loose-coupler covering a range of from 300 expected to get was the nightly press communication gives to man seemed more to 3000 meters, approximately, galena report of WSL, the Atlantic Communi- remarkable in the hills than in the city, detector, and 2ooo-ohm telephones, with cation Company's large station at Say- where mechanical appliances and triumphs the usual accessories. The water supply ville, Long Island. This transmitter was are the regular thing. in the house came from a spring about a Telefunken spark set rated at 35 kilo- In walking and driving about the Cat- 2000 feet distant, through galvanized iron watts. I don't know what the actual an- skills in those years (1912-1914) I never saw pipe, partly on the surface and partly tenna power or "Turm Kraft," as the another antenna. I have sometimes won- this buried; gave me a good ground. I German engineers called it, amounted to dered whether I was the first to introduce strung a single-wire antenna to a tree about possibly something in the neighborhood of radio into the haunts of Rip Van Winkle, 250 feet from the house, and higher up the 10 kilowatts. Anyway, it was the powerful in the summer of 1913. If there are any hill. I climbed the tree and my sister set of its time, and did a great business other claimants to the honor, let them helped me on the ground. The height communicating with vessels crossing the speak now, or forever hold their peace.

A regular portion of Mr. Dreher's department, "As the Broadcaster Sees It" is devoted to technical procedure in broadcasting stations. That section of his department is of especial interest and help to the many engineers and others engaged in the daily solving of problems of broadcasting. Mr. Dreher invites contributions from other broadcasting engineers, telling of l(inl(s of operation, or any f(ind of short report on their daily technical experiences which will be helpful to those similarly engaged. All contributions accepted will be paid for at our regular space rates. We believe, also, that the technical side of the operation of a broadcasting station is of deep interest to the great body of radio experimenters as well as to those who ma\e their living supplying broadcast service to the listener. The material appearing in this department is so written that it is sufficiently technical to be of help to the engineer, but yet not too involved for the average experimenter to comprehend. JUNE, 1916 RADIO BROADCAST 153

Atlanta. Ga 930 590 375 550 595 745 660 520 470 Baltimore. Md 350 600 420 315 405 170 85 200 730

Birmingham, Ala. . . . 1050 580 415 615 640 855 775 610 400 Boston, Mass 840 730 540 600 190 270 475 1100 Buffalo, N. Y 4OO 450 395 175 215 295 280 180 655 Calgary, Alta 2060 1370 1620 1645 1555 2000 1200 1755 1950 Chicago, 111 840 230 300 225 700 650 400 250 RADIO BROADCASTS Cincinnati, O 730 230 215 225 560 500 250 300 Cleveland, O 540 300 215 75 400 XM 110 480 Dallas, Tex 1515 800 795 1000 990 1350 1280 1060 540 Davenport, la 990 160 360 455 390 860 800 560 200 Denver, Colo 1750 900 1080 1200 1140 1600 1550 1310 775 Booklet of Des Moines, la 1135 300 500 605 540 1010 965 710 265 Detroit, Mich 600 225 225 75 475 435 200 440 Elgin, 111 870 35 280 335 260 740 690 440 255 Galveston, Tex 1585 945 880 1100 1090 1400 1315 1125 690 Hastings, Neb 1400 560 740 865 795 1265 1215 965 445 American Havana, Cuba 1500 1315 1100 1250 1325 1300 1270 1215 1165

Indianapolis, Ind. . . . 790 160 100 255 230 630 575 325 230 Iowa City, la, 1045 200 405 505 435 900 860 600 210 and Joliet, 111 870 35 250 330 260 730 680 430 225

Kansas City, Mo. . . . 1225 400 545 690 640 1080 1025 775 230 Lansing, Mich 680 170 240 170 85 550 520 280 400 Los Angeles, Cal 2560 1730 1875 2020 1950 2420 2360 2110 1565 Louisville, Ky 815 270 90 300 310 645 570 345 245 Madison, Wise 925 120 370 405 325 800 760 520 300 Memphis, Term 1120 480 410 620 615 950 870 655 240 Mexico City, Mex. . . 2300 1675 1600 1800 2120 2115 2035 1860 1420 Broadcasters Miami, Fla 1280 1180 950 1085 1150 1100 1025 1010 1050

Milwaukee, Wise. . . . 840 80 320 335 255 725 690 450 325

Minneapolis, Minn. . . 1110 360 590 620 545 1005 980 750 465 Montreal, P. O 260 740 700 490 515 335 400 470 970

New Orleans, La. . . 1340 820 700 910 925 1150 1080 910 590 New York. N. Y 190 700 560 400 475 90 310 870 Oakland, Cal 2650 1820 2000 2115 2030 2500 2490 2240 1705 Philadelphia, Pa 270 650 500 350 435 90 250 800 Pittsburgh, Pa 475 400 250 110 200 310 250 550 Providence, R. I 40 825 700 525 585 150 235 450 1000 St. Louis, Mo 1100 250 300 480 440 870 800 550

San Francisco, Cal. . . 2650 1820 2020 2140 2065 2540 2500 2240 1715

Schenectady, N. Y. . . 145 700 6OO 400 460 150 210 350 900 Seattle. Wash. 2500 1710 1950 2000 1920 2400 2385 2115 1695

Springfield, Mass. . . . 80 760 645 460 525 120 200 395 960 Tampa, Fla 1160 1060 775 925 985 1000 930 870 855 Toronto, Ont 440 425 400 190 200 350 340 225 640 Valparaiso, Ind 815 45 200 270 210 670 625 370 255 Arranged by Washington, D. C. . . 390 590 400 300 390 200 125 190 705 Winnipeg, Man 1350 710 970 940 850 1295 1275 1050 845 LAWRENCE W. CORBETT Worcester, Mass 40 800 700 500 570 155 235 435 985 Zion. Ill 850 45 285 320 240 720 675 420 290 Sixteen

WAVE- FREQUENCY LENGTH POWER Log Sheet IN KC. IN METERS IN WATTS Northfield, Minn. 890 336.9 500

Shenandoah, la. . . . 1110 263 1000 CALL WAVE- DIAL DIAL Seattle, Wash 660 454.3 1000 SIGNAL LENGTH FREQUENCY 2 3 Burlingame, Cal. 1330 226 50

Long Beach, Cal. . . . 1290 233 500

Salt Lake City, Utah . . 1270 236 250 David City, Neb. . . . 1330 226 100 Wichita, Kans 1300 231 50 Omaha, Neb 1210 248 100

St. Paul, Minn. . . . 1190 252 50 Dublin, Tex 1190 252 15

Greenville, Tex. . . . 1240 242 10 Los Angeles, Cal. . 1300 230.6 500 Carterville, Mo. 1160 258 20 Spokane, Wash. . . . 1130 266 100 St. Louis, Mo 1150 261 100

Fort Worth, Texas . . . 1140 263 590 508.2 lOOOJ Anchorage, Alaska . 1320 227.1 100 Iowa City, la 1340 224 10 Holy City, Cal. . . . 1380 217.3 100 North Bend, Wash. . . 1390 215.7 50

Hollywood, Cal. . . . 1330 225.4 50 Beeville, Tex 1210 248 250 San Francisco, Cal. 1120 268 50 Columbia, Mo 600 499.7 500 Olympia, Wash. 1370 218.8 50 Los Angeles, Cal. 1090 275 500 Galveston, Tex 1160 258 50 Colorado Springs, Colo. 12SO 239.9 100 St. Louis, Mo 550 545.1 500 Denver, Colo 1280 234 50 Ogden, Utah . . . . 1340 224 50 Oakland, Cal 1170 256 50

Salt Lake City, Utah . . 1150 261 100 Oakland, Cal 1360 220 50

San Pedro, Cal. . . . 1460 205.4 50 St. Louis, Mb 1250 240 500

Independence, Kans. . 1270 236 15 Houston, Tex 1250 240 10 Welcome, Minn. 1320 227 50

Cape Girardeau, Mo. . 1340 224 50 San Diego, Cal. . . . 1220 246 500 Albuquerque, N. Mex. 1200 250 10 Ogden, Utah . . . . 1150 261 500 Hollywood, Cal. 1190 252 500 Upland, Cal 1420 211.1 50 St. Louis, Mo 1400 214.2 250 Chico, Cal 1180 254 100 South San Francisco, Cal. 1330 226 500 Oakland, Cal 1450 206.8 500 Ayalon, Cal 1420 211.1 250 Pineville, La. 1260 238 100 Fourteen Three 154 RADIO BROADCAST JUNE, 1926

WAVE- CALL LOCATION FREQUENCY LENGTH POWER SIGNAL IN KC. IN METERS IN WATTS Log Sheet KDKA East Pittsburgh. Pa 970 309.1 Varies Devils Dak KDLR Lake, N. 1300 231 5 CALL WAVE- DIAL DIAL Salt Lake 1220 246 50 KDYL City, Utah .... SIGNAL LENGTH FREQUENCY 2 3 KFAB Lincoln, Neb 880 340.7 1000 KFAD Phoenix, Ariz 1100 273 100 KFAF San Jose, Cal 1380 217.3 50 KFAU Boise, Idaho 1070 280.2 750 KFBB Havre, Mont 1090 275 50 KFBC San Diego, Cal 1390 215.7 50 KFBK Sacramento, Cal. 1210 248 100 KFBL Everett, Wash 1340 224 100 KFBS Trinidad, Colo 1260 238 15 KFBU Laramie, Wyo 1110 270 500 KFCB Phoenix, Ariz 1260 238 100 KFDD Boise, Idaho. 1080 278 50 KFDM Beaumont, Tex 950 315.6 500 KFDX Shreveport, La . 1200 250 100 KFDY Brookings, S. Dak 1100 273 100 KFDZ Minneapolis, Minn 1300 231 10 KFEC Portland, Ore 1210 248 50 KFEL Denver, Colo 1180 254 50 KFEQ Oak, Neb 1120 268 500 KFEY Kellogg, Idaho 1290 233 10 KFFP Moberfy, Mo. . 1240 242 50 KFGQ Boone, la 1330 226 10 KFH Wichita, Kans. 1120 268 500 KFHA Gunnison, Colo 1190 252 50 KFHL Oskaloosa, la 1250 240 10 KFI Los Angeles, Cal 640 468.5 4000 KFIF Portland, Ore 1210 248 100 KFIO Spokane, Wash 1130 265.3 100 KFIQ Yakima, Wash 1170 256 100 KFIU Juneau, Alaska 1330 226 10 KFIZ Fond du La.c, Wise 1100 273 100 KFJB Marshalltown, la 1210 248 10 KFJC Junction City, Kans 1370 218.8 10 KFJF Oklahoma, Okla 1150 261 500

KFJI Astoria, Ore. . . 1220 246 10

KFJM Grand Forks, N. Dak. . . . 1080 278 100 KFJR Portland, Ore 1140 263 50 KFJY Fort Dodge, la 1220 246 50 KFJZ Fort Worth, Tex 1180 254 50 KFKA Greeley, Colo 1100 273 50 KFKU Lawrence, Kans 1090 275 500 KFKX Hastings, Nebr 1040 288.3 5000 KFKZ Kirksville, Mo 1330 226 10 KFLR Albuquerque, N. Mex. ... 1180 254 100 KFLU San Benito, Tex 1270 236 10 KFLV Rockford, 111 1310 229 100 KFLX Galveston, Tex 1250 240 10 KFLZ Anita, la 1100 273 100 KFMR Sioux City, la 1150 261 100 KFMW Houghton, Mich. 1140 263 50 Two Fifteen

WAVE- WAVE- CALL FREQUENCY LENGTH POWER CALL LOCATION FREQUENCY LENGTH POWER SIGNAL IN KC. IN METERS IN WATTS SIGNAL IN KC. IN METERS IN WATTS KFWV Portland, Ore 1410 212.6 50 CKAC Montreal, P. Q 730 410.7 1200 B. 730 410.7 KFXB Big Bear Lake, Cal. . . 1480 202.6 500 CKCD Vancouver, C 1000

. Sask 630 KFXD Logan, Utah . . . 1460 205.4 10 CKCK Regina, 475.9 500 KFXF Colorado Springs, Colo. 1200 250 500 CKCL Toronto, Ont 840 356.9 500 KFXH El Paso, Tex 1240 242 50 CKCO Ottawa, Ont 690 434.5 100 KFXJ Denver, Colo, (portable) . 1330 215.7 10 CKCW Durham Co., Ont. (Not Active) 910 329.5 5000

KFXR Oklahoma, Okla. . . . 1400 214.2 15 CKFC Vancouver, B. C 730 410.7 50 KFXY Flagstaff, Ariz. 1460 205.4 50 CKNC Toronto, Ont 840 356.9 500 KFYF Oxnard, Cal .... 1460 205.4 10 CKOC Hamilton, Ont 880 340.7 50 KFYJ Houston, Tex. (portable). 1260 238 10 CKY Winnipeg, Man 780 384.4 500 KFYO Texarkana, Tex. . . . 1440 209.7 10 CNRA Moncton, N. B 1030 291.1 500

KFYR Bismarck, N. Dak. . . 1210 248 10 CNRC Calgary, Alta Uses CFAC or CFCN KGO Oakland, Cal 830 361.2 4000 CNRE Edmonton, Alta Uses station CJCA KGTT San Francisco, Cal. 1450 206.8 50 CNRM Montreal, P. Q Uses CHYC, CKAC

KGU Honolulu, Hawaii . 1110 270 500 or CFCF KGW Portland, Ore. 610 491.5 500 CNRO Ottawa, Ont. . 690 434.5 500 Sask. Uses station KGY Lacey, Wash 1220 246 50 CNRR Regina, CKCK K.HJ Los Angeles, Cal. 740 405.2 500 CNRS Saskatoon, Sask. Uses station CFQC Kill.! Spokane, Wash. 760 394.5 1000 CNRT Toronto, Ont. . Uses station CFCA

KJBS San Francisco, Cal. 1360 220 5 CNRV Vancouver, B. C. 1030 291 . 1 500 KJR Seattle, Wash 780 384.4 1000 CNRW Winnipeg. Man. Uses station CKY KLDS Independence, Mo. 680 440.9 1000 KLS Oakland, Cal 1200 250 250 KLX Oakland, Cal 590 508.2 500 KLZ Denver, Colo 1130 266 250

KMA Shenandoah, la. . . . 1190 252 500 KMJ Fresno, Cal 1280 234 50 FOLLOWING these instructions, a sixteen-page booklet giving all

KMMJ Clay Center, Neb. . . . 1310 228.9 1000 BYthe call signals, frequencies, wavelengths and power of American and KMO Tacoma, Wash. . . . 1200 250 100 Canadian stations, together with a distance KMOX St. Louis, Mo 1070 280.2 1500 broadcasting computation table and will result. to 1 it will be seen that the KMTR Los Angeles, Cal. . 1260 238 500 log, Referring page 53, KNRC Los Angeles, Cal. 1440 208.2 250 page has been divided up into four sections, each section representing a KNX Los Cal. 890 336.9 1000 Angeles, of the booklet. 1 his is made of KOA Denver. Colo 930 322.4 5000 page completed page up pages one, three, KOAC Corvallis, Ore 1070 280.2 500 fourteen, and sixteen of the booklet. KOB State College, N. Mex. 860 348.6 1000 The pages should be cut from the magazine with a sharp razor blade KOCH Omaha, Neb 1160 258 250 as near to the binding as possible. Next, these two pages are carefully cut, KOCW Chickasha, Okla. . . . 1190 252 200 each into the center horizontal line taken as a KOIL Council Bluffs, la. . 1080 278 500 two, being guide. We KOIN Portland, Ore 1410 212.6 500 then have four rectangular sheets, two consisting of original pages 153 KOWW Walla Walla, Wash. . . 1170 256 500 and and two of and The next is to cut KPO San Francisco, Cal. 700 428.3 1000 154, pages 155 156. procedure KPPC Pasadena, Cal 1310 229 50 around each of these sheets on the border line. Thus the original page KPRC Houston, Tex 1010 296.9 500 numbers, date, and magazine title will be removed. It is advisable to KPSN Pasadena, Cal 950 315.6 1000 leave a slight border in this operation to allow for the KQV Pittsburgh, Pa 1090 275 500 trimming up KQW San Jose, Cal 1300 231 500 finished booklet. KRE Berkeley, Cal 1170 256 100 Each sheet is then folded down its center vertical line and the folios Kans. 880 340.7 KSAC Manhattan, 500 inserted within each other to the numbers KSD St. Louis, Mo 550 545.1 500 according page printed.

KSL Salt Lake City, Utah . . 1000 299.8 1000

KSMR Santa Maria, Cal. . . . 1430 209.7 100

KSO Clarinda, la . . . . 1240 242 500 Four Thirteen JUNE, 1926 RADIO BROADCAST 155

CALL SIGNAL WTAQ WTAR WTAW WTAX WTAZ WTIC WWAD WWAE WWAO WWI WWJ WWL

CFAC CFCA CFCF CFCH CFCK CFCN CFCO CFCU CFCT CFCY CFDC CFKC CFMC CFQC CFRC CFXC CFYC CHCS CHIC CHNC CHSC CHUC CHXC CHYC CJBC CJCA CJCD CJGC 'CJKC CJSC CJWC CJYC 156 RADIO BROADCAST JUNE, 1926

CALL SIGNAL WBAO WBAP WBAX WBBL WBBM WBBP WBBR WBBS WBBW WBBY WBBZ WBCN WBDC WBES WBNY WBOQ WBRC WBRE WBT WBZ WBZA WCAC WCAD WCAE WCAJ WCAL WCAM WCAO WCAP WCAR WCAT WCAU WCAX WCBA WCBD WCBE WCBH WCBM WCBQ WCBR WCCO WCLO WCLS WCOA WCSH WCSO WCWS WCX WDAD WDAE WDAF WDAG WDAH New 1926-27 Trends in Radio

The "Truphonic" the New Donle Contribution to Better Amplification New Localized Single Control Over* coming Existing Difficulties Important Socket Improvements These Anticipate Trends for the New Trade Year

Reported by DONALD WILHELM

invention, engineer- established themselves as a kind of a new means of amplification certain ing skill and manufacturing re- legal tender in the changing scheme to have important results in 1926-27. CLEARLY,liability are the factors that of things. II. A new localized control con- have told and will continue to tell It can be taken for granted, thus, to denser now in production is a sound Radio's story. go no further, that the Alden Com- and ingenious device with many speci- Every year has contributed its bit. pany at Springfield, Massachusetts, fic advantages, one of which is that it The greatest contribution, for instance, having been duly admired for its many can be operated as easily as one fingers of the last year probably consisted of efficiencies by such business magazines any three contiguous keys on a piano. better re-arrangement of parts inside as System and Factory has the needed III. Another Alden development and out of our millions of receiving precision and reliability and standing consists of a new method of gang socket sets. What improvements and new to back up its announcement with mounting, universal in its applica- trade lines will set off 1926-27 from deliveries scheduled to a day and hour. tion by manufacturers and home- all other years is now the big news. But it needs to be added that this constructors, and economical in cost. For the technicians have all been hard company has not been content with IV. The fourth major Alden de- at work. And the manufacturers are pacing its production to current needs velopment is a new cushion-mounted keen to serve the technicians. Hereto- and to limiting its field to areas amply socket for vacuum tubes. Protected fore both on occasion have been pre- consolidated. In other words, it has by the earliest patents, it is devised to mature have been "right" too soon. brought its established organizing gen- provide an exclusive means to hold a Obviously, many manufacturers lack ius to bear on the solution of prob- tube out of physical contact with the the ability and capital to make deli- lems of supreme importance to Radio base while providing adequate elec- veries in a dependable way. And with the result that its products will trical connection. many more risk patent difficulties undoubtedly occupy larger space than The large usefulness and detailed that interrupt their plans. ever on store counters, in wholesale advantages of these and other Alden But it is my privilege here and now departments and in catalogues, and products are of such strategic import- to announce and to describe the con- in the radio receivers made by reputa- ance to the radio public and trade at tributions to be made by one company ble manufacturers. the present time that the following de- whose prestige and organization were In preliminary fashion it is worth scriptions of their functioning clearly established even before its central pointing out four major new contribu- are in order. loyalties were diverted to radio parts. tions evolved by this company: I. THE DONLE TRUPHONIC This company used to have for its I. The Donle Truphonic reflects slogan when molding insulation to all the interest we all have in improved Transformer, resistance and im- manner of needs, "You Design It, reproduction. It is synonymous with pedance amplification all have had We'll Make It!" Now its slogan their innings. might better be, "We have Designed Transformer coupling when of the TRUPHONIC COUPLING it Here It Is!" So, when it makes most costly type is fairly efficient. such an announcement as the follow- Resistance in the -400 coupling gives, ing, that announcement is news! In TRANSFORMER opinion of many, the best quality of 'X other words, when it devotes its New COUPLING. reproduction, yet it is not particularly England plant, its high skill and un- efficient, requires extra voltage in B failing facilities to improvements that batteries and has the weakness of are revolutionary, the radio public /ZOO deteriorating elements. and the radio trade can take its The rather ex- safely / RE.Sm-ANCE_COUPLINC. impedance coupling, accomplishments as final. pensive, gives markedly better quality It is sufficient to repeat that of than the transformer, being practically course a household word has for years equal to resistance. been the word "NA-ALD." ^ Now comes a new means of ampli- Alden adapters, for instance, have fication superior to resistance coupling. made possible the practical use of With three tubes it has an amplifica- power tubes in every vacuum-tube Chart showing superiority of remarkable new tion, practically free of all distortion, receiver now in use. And, past ques- "Truphonic" coupling, which gives large and greater than the best audio trans- constant amplification over the entire musical scale. tion, the power tube has afforded the former amplification with two tubes. From this it will be seen that transformers usually to This new is so distinctive in opportunity greatly improve quality give large but varying amplification, missing the coupling reproduction by increasing gain and low notes. Resistance gives constant, but small, performance that it merits a distinc- cutting down overloading. amplification. While only the improved, Tru- live name TRUPHONIC. method has the both, without Alden sockets and dials a great phonic advantages of It is the invention of H. P. Donle, their defects, giving large and uniform amplifi- of them to an in- who has more than a hundred inven- family answering cation. Curves show input-output ratio of complete finitude of uses likewise long since amplifying unit. tions to his credit, including the Sodion ADVERTISEMENT NOT COPYRIGHTED 157 NEW 1926-27 TRENDS IN RADIO

detector tube, the diamond weave coil ing only one large dial in the center of and other devices which set this in- the panel were offered to the public. ventor apart as one of the greatest of Practice in many instances demon- tube experts. strated, however, that these receivers, The Truphonic was the result of if satisfactory at all, were really con- definite mathematical calculations ex- trolled not by the "single" dial alone. tensively tested out. One or more and usually more addi- One of the tests, charted on the pre- tional dials or knobs on the panel ceding page, shows graphically a defi- greatly affected the proper tuning of nite superiority of the Truphonic over the set. These smaller knobs were any other method of amplification yet intended to be vernier in their action. evolved. The accompanying chart In fact they were often critical and shows that it gives nearly as flat a hard to adjust. So, to put it simply, characteristic as resistance with none usually the so-called single control re- of the objectionable distortion of trans- ceiver was found in fact to be harder former amplification. Still this chart to operate than the receivers employ- does not adequately suggest what the ing two or three dials of large and more when it is convenient size. Truphonic accomplishes The Truphonic Amplifier, a great new invention in The means in tihe effort substituted for other couplings any for those who value quality reproduction employed, standard circuit, for the improved to attain single control, were multiple quality suggests the subtle but very safe to predict that in view of the condensers mounted on a single shaft, definite difference that exists between widely recognized inadequacy of audio all moving together, all controlled by the new Orthophonic and the old frequency amplifiers many of the a single dial. Victrola. Therefore it will not be prominent set manufacturers will in- The Hogan patent covers this gen- surprising if the Truphonic extensively clude the Truphonic in next year's eral principle. It is a well-known fact supersedes all existing forms of audio models. The better service given by that the method of using multiple amplification couplings. the Truphonic, its reasonable cost, condensers mounted on a single shaft Now, much has been written, of its longer life and the economy it involves a necessary compromise be- course, on the subject of correct, un- passes on to the user in lowered battery tween flexibility of control on one hand distorted or uniform amplification over consumption make the wide popularity and the single control idea on the other. the entire audio frequency band. of Truphonic amplification a certainty. Competent radio engineers have recog- Those who have experimented with It requires no additional B batteries, nized the inevitable limitation this resistance amplification know its prac- needed in resistance coupled amplifica- method of control puts upon the proper tical limitations. From a study of tion. To put it simply: Its total cost, adjustment of the required tuning curves we know that transformer ampli- in view of its merits, is surprisingly low. elements and that, working from this fication magnifies the middle frequen- Truphonic, for many good reasons, limitation, different compromise ar- cies, leaving noticeable weaknesses in is music up the street of the radio rangements must be made throughout the low notes and overtones. Even amateur. It affords room for an end- the receiver. when these distortions are not audible less variety of experimentation with Really, the problem of evolving a one has a vague and disquieting sense of hook-ups already in existence. Vari- simple method of utilizing all the ad- the inadequacy of the music or speech ous circuits which the radio magazines vantages of single control without any rendered. On the other hand, the and new^oapers have popularized will of its limitations, still remained. chart herewith shows the remarkably doubtless be modified to include the The Alden Company now believes flat characteristics of the Truphonic, Truphonic amplifier. In addition that it has solved this problem, that which affords faithful reproduction radio writers cannot fail of having its new localized control unit will over the entire musical scale. their interest evoked with resulting answer to the large existing need. And again referring to the chart, one wide publicity. Heretofore the two concentric, in- can see that Truphonic amplification dependently controlled drums used on n. THE NEW NA-ALD LOCALIZED gives more gain than resistance am- the Radiola Super Heterodyne have CONTROL UNIT plification. Those most familiar with been the nearest approach to securing resistance amplification best know its Single-control tuning so simple that the practical benefits of single control limitations. "grandmother can operate it" has without any of its weaknesses. Authorities agree that resistance long since been an ideal. Practically The Alden unit goes a step further. coupled amplification will not super- all the radio engineers in the country It employs three concentric drums. sede other methods, and call attention have given thought and effort to con- These overcome one of the disadvan- to the known fact that the gain per trol so simple that a child might use tages of the two concentric drums used stage with resistance coupled amplifica- it in the dark. And 'way back, of on the Radiola Super Heterodyne tion is not sufficient to merit its use course, there appeared on the market i.e., they do not stick together and throughout the audio end. As a various so-called single-control re- prevent one from moving without matter of fact many sets designed to ceivers with only one movable dial, the other. Instead, in the Alden unit, utilize the resistance method employ though engineers knew that absolute each moves freely on its own axis. one or more stages of transformer single-control with only one movable Yet the three move together when coupling to get the required boost in dial was still a day dream. desired as is customary with single- audio signals. To be sure, many factory-made re- control dials. The Alden Company feels that it is ceivers neat in appearance and featur- This Na-Ald Localized Control Unit

The improved new Gang Socket Mountings are compact and universal in use, taking easily both types of tubes 158 ADVERTISEMENT NOT COPYRIGHTED NEW 1926-27 TRENDS IN RADIO

This device all the without th: amazingly simple tuning accomplishes good of single control, losing flexibility of separate controls. There is a drum for each condenser, and each drum moves freely separately, or in unison with the others. Called the "Na-.4ld Localized Control Unit," it merits wide popularity among set builders

opens new possibilities for the electrical It is also made in a twin-dial model production of the materials used for experimenter and the cet manufacturer. affording two variable tuning elements. insulation. The laminated material It is pleasant for an engineer to realize developed for the new gang sockets is III. THE NEW NA-ALD GANG SOCKET that he can use three variable therefore molded in accordance tuning MOUNTING with controls and still retain all the ad- the dictates of long specialized ex- vantages of single control. One of the principal items of labor perience, and is produced in a plant These controlled drums carry a space involved in the construction of a re- equipped for quantity production with for logging stations and a convenient ceiver is the placing of tubes with their a minimum of waste. means of indicating exact dial locations respective connections. Any improve- More to the point, this improved stations in of kilocycles and meters. ment in this field clearly has wide ap- gang socket is new in principle. The complete Na-Ald Localized Con- plication, answers to extensive needs. In all set construction gang sockets trol Unit consists of three separate Having specialized for years in the utilize at least one connection common condensers with three tuning control manufacture of sockets, it was logical to each tube. By providing in ad- drums mounted on a suitable bracket, for the Alden Company to devote itself vance an absolutely universal gang complete and ready for use in building to betterment of sockets with the result socket the new Na-Ald saves a vast a receiver. that out of its long experience it has deal of labor in eyeletting and soldering Each condenser is independent, be- evolved for the use of set builders a and other means for Connection with ing operated by a separate drum. new gang socket mounting with con- independent contacts. In other words, There is no frictional connection be- clusive advantages over any now on the the new gang socket provides a con- tween the drums, so each can be moved market. tinuous strip of conducting metal from freely. This control, being new in its To begin with, the material and one end of the gang socket to the other. conception and its practical applica- space required for the use of this new Moreover, a second common connector tion, does not infringe existing patents socket are reduced to a minimum so is provided for use in tapping the on single control of several tuning that this new Na-Ald mounting is un- second filament contacts if desired, units. License to use is conveyed by matched for both convenience and and these filament contacts can be its sale. economy. Further, the Alden Com- tapped separately. The condensers and controlled drums pany long back even before it began Another attractive feature of this are supported on a rigid metal bracket. to manufacture radio products were new gang socket is that it takes both The control drums extend beyond the expert in the sound and economical the old and the new type of tubes, maximum swing of the condensers making it universal in its application. and pass through the front panel for And in other ways these new Na-Ald tuning. Since there is no direct con- gang socket mountings lend themselves nection to this front panel, the panel to a variety of uses. itself may be of any material desired They render a positive service to either of wood, of metal or of the set builder in anticipating and bakehte. solving in advance some of the hardest This unit greatly simplifies set con- of mechanical and designing problems. struction. It may be assembled to Working from them, since they are brackets carrying a gang socket, sub the last word in compactness and panel or other desired equipment and efficiency, engineers can devote their simple wiring connections with a time and attention to details of greater minimum of soldering. The whole set importance affecting the physical ar- thus makes a very compact and rugged rangements of the other instruments unit. within the receiver. The unit, moreover, permits sharp For every reason, thus, not the least tuning. The diameter of the drums is of which is that the new gang sockets 4.5 inches made purposely large to will greatly simplify the work of de- facilitate exact tuning. This large signers during the coming year, manu- size also makes it possible to swing facturers and set constructors will wel- This a idea how the Na-Ald from the highest to the lowest wave gives general of come these compact and efficient Localized Control Unit may be assembled to the lengths almost without and recommend them as instantly, phy- panel. Also illustrating the wonderful ease it mountings sical a effort, by finger or two. gives to tuning standard equipment. ADVERTISEMENT NOT COPYRIGHTED 159 NEW 1926-27 TRENDS IN RADIO

They provide an attractive, conven- To change over, in an instant, fron. ient, self-contained unit. ordinary tubes to power tubes it is only It is to be added that an exception- necessary to have on hand only three ally high quality of workmanship is new parts: a B battery, a C battery employed, and that all the connections and a Na-Ald Connectorald which is are covered by the insulating material provided with leads to these batteries. are protected from dirt and moisture, No wiring whatever is necessary. which cause many sets to become in- Produced as they are at low cost, operative or inefficient and qualify easy to install, definite and certain in under the recent ruling of the Fire their results, Na-Ald Connectoralds Underwriters' Laboratory against ex- were designed for wide use and have posed live metal connections on current found it. operated sets. The demand for them promises to be greater than ever during the coming IV. THE NEW NA-ALD CUSHION MOUNTED all set owners want one! SOCKET A new addition to an illustrious family the year. Nearly improved Na-Ald Spring Socket no electrical Every set dealer needs them the Radio constructors have long ap- contact between the tube and the set, other than the company itself has had a busy time grid, filament and plate leads preciated the advantages of cushion answering inquiries and getting con- mounted sockets. But it has remained nectorald shipments out on schedule. for Alden with its slogan "It's the The Na-Ald gang socket mounting And a jobber might as well have a Contact that Counts" to develop a can, of course, be used with the great- blank page in his catalogue as to fail mounting for this purpose that meets est ease for assembly in any equipment to reserve ample space for them. all requirements. desired, but it fits well with especially SET BUILDERS CAN COUNT ON ALDEN This new socket construction, more- both (or either) the Donle amplifier over, is protected by the well-known and the Na-Ald localized control unit. A well-known set manufacturer Friedrich patent and others covering A complete receiver using the Na- telegraphed an order, recently, for the principle of vacuum tubes held out Ald devices assembles in a space of 7 x a quantity of Na-Ald dials. Under of physical contact with the base by 12 inches. This great compactness stress of heavy commitments he means of contacts which are also the need not reduce in any way the elec- wanted them "quick." But he was electrical connections. And they, also trical efficiency of the receiver. Even greatly surprised and pleased to re- have protection covering the principle in this small space there is room to ceive his shipment in less than forty- of socket construction in which there include shielding where desired. eight hours. And he was even more are openings for the prongs of vacuum The localized control tuning device, surprised when he was told that his tubes with metal strips pressing against affording the simplest and most per- order was built up from raw materials the tube prongs, frictionally holding fect tuning control available; the to finished product in a day. the tube in the socket yet allowing it Na-Ald Donle amplifier for the audio It is a fact that most of the Alden to be withdrawn. frequency end, a distinct advance over production is built up from raw ma- They take both types of tubes. all existing methods; and the conven- terials to finished products in a day. In all respects, therefore, they are as ient gang socket mountings all, jointly It is paced the plant is geared trouble-proof as engineering and pro- and separately, adaptable to all stan- throughout to systematic output typi- ductive skill can make a radio part. dard circuits. fied by mechanical carriers flanked on Thus the Alden rich in both sides THE COMBINED ALDEN LINE FOR line, already by swift-fingered girls doing utilities for set is their bits. It has a flexible ECONOMICAL RECEIVER CONSTRUCTION builders, vastly respective broadened in its scope, solving in ad- and reliable labor supply. It has ad- These four major additions to the vance many of the knottiest problems vantages in that it has on occasion Na-Ald line are only part of the story. of set design and construction. been able to serve New York City Na-Ald dials, sockets, adapters and jobbers as promptly as they could be DON'T OVERLOOK NA-ALD connectoralds have for been served New York manufac- years legal CONNECTORALDS by City tender in the radio market. The turers. And it can supply New Eng- additions made to these established Of course, everyone except one or land, the Middle West, and the South products, while affecting widely varied two has a set nowadays. Most of us by truck or express with certainty and radio problems and opening many new have ordinary tubes in our sets, and speed. opportunities both in engineering and all of us want the best possible results This flexible yet carefully inspected in the manufacture of useful radio from our sets. But we all know that service from a plant so well organized equipment, still are closely related one ordinary tubes when overloaded cause that it has a "vest-pocket shipping to another. They can be combined distortion, and the effect is like that of room," is without question an asset effectively. listening to someone who is over- to the jobber or manufacturer who Many set manufacturers will find straining his voice. uses the Alden standard parts in his that combining two or more of the To put it simply: Because we all receivers. Na-Ald units will not only effect econo- want the best results, and power tubes He can bank on the certainty and mies inherent in each unit but will also therefore, thousands have found great promptness of Alden deliveries. prove a great labor and worry saver be- satisfaction in using Na-Ald Connec- And he can bank on Alden financial cause of their practical interrelation. toralds. standing and business methods as well.

Connectoralds and Na-Ald Adapters make possible the use of practically any tube in any set, including the new pooler tubes which add much power and greatly clarify the outcoming music or speech 160 ADVERTISEMENT NOT COPYRIGHTED RADIO BROADCAST ADVERTISER 161 POWER By NOE H. TYAR

In radio we sense a sort of subtle beauty that makes a distinct appeal to the imagination. Even experienced broadcast artists say they never face the microphone without a thrill, a thrill that comes with the realization of the wonderful wizardry of wireless. No wonder they are willing to give of the best and finest that lie within their power. Surely no voice could be too clear, no note too pure, no har- mony too perfect that is to be caught and thrown broadcast to the four winds, broken to a million pieces and each piece captured, amplified and reproduced in nearly instantaneous and perfect accord with the original. Truly, the folk who work in the studio are living in an atmosphere laden with wonder and romance. But do not all those who come in contact with radio in all of its myriad branches feel the same awe? Does not the set owner experience much the same thrill when he tunes in a station as does the artist at the other end? And how about the men behind the scenes, especially the research workers who RELIABILITY is the keynote of radio reception in the well have made this marvel possible? appointed home. And reliability, linked with true tone qual- Let us make a visit to the Raytheon is the foundation which the success of laboratory in Cambridge and get ac- ity, upon RAYTHEON quainted with the men who are actu- B-power units has been built. ally doing the day by day research that is so essential to progress. The perfected B-power unit has joined the radio receiver To those who visualize a laboratory with a source of inexhaustible as a dusty and cobwebby corner in a dark the first in this that flows with basement, glance power; power is a , full up-to-date laboratory will be an eye- unceasing regularity from the wave rettifying tube ample opener. Instead of some old, wizened, turbine-driven of huge generators to gray-haired eccentric peering through capacity eliminate B-batteries his horn-rimmed at a test in the central station. glasses tube, on even the largest ten-tube set. we see a dozen bright eyed young men When your present set of B-batteries in as many different occupations. RAYTHEON units are runs low and in- B-power One rather tall, studious looking reception wavers, manufactured by the companies chap is seen operating a sort of death- stall a RAYTHEON B-power unit. The shown on the that cost followingpages. defying apparatus splits the ear of operation is negligible and you with intermittent and crackling hissing are permanently relieved of the neces- sounds. Suppose we investigate and sity for buying B batteries. see just what is accomplished by this affront to our ear drums.

Making Experimental Models Upon approaching as near as seems safe without endangering our lives, we see that he is on a row of half RAYTHEON working finished tubes which look very much RAYTHEON MANUFACTURING COMPANY JL ADVERTISEMENT CAMBRIDGE, MASSACHUSETTS ^ RAYTHEON

Tested and approved by RADIO BROADCAST 162 RADIO BROADCAST ADVERTISER

like the standard Raytheons, with which we are familiar. The six or GENERAL Ru>10 eight tubes on which he is working are minus the regular brass bases, and up at the top where we are accustomed to see 365 a little glass tip, we now find long Type Type 366 Rectifier glass tubes which run up to an intri- Filter Choke Transformer cate system of glass piping. Price 10 Price 10 Among the network of fragile glass tubing which composes this system, we see large glass bulbs supposedly filled with rare gases, queer looking Modernize your Radio Set- mercury gauges which resemble huge thermometers bent all out of shape, Build a Practical "B" Eliminator and a swift running vacuum pump "B Elimination." The popular topic of discussion among radio experimenters todayis battery that pounds away doggedly in appar- Constanc worry whether the "B's" are run down and their continual replacement will soon be a thing of the past in radio. A "B" Eliminator never runs down and never has to be replaced. ent disregard of the fact that nature For a dependable plate supply unit which requires absolutely no attention other than its abhors a vaccum. We turn to our com- original installation, build a "B" Eliminator of General Radio parts. Write today for full data on General Radio Rectifier Transformers and Filter Chokes, and placent guide who assures us that the our circular with full instructions for building a Practical "B" Eliminator. get apparatus is simply a system to make GENERAL RADIO Co. Cambridge 39, Mass. up tubes for experimental purposes. It seems that the building up of satisfactory gaseous rectifier is a rather complicated process. Among the most important of the operations is the one MODERN "B" Power Unit of "bombarding" which attracted our It's Better Because It's Modern attention due to its ear-splitting noise. "Bombarding" a tube means that it is Modern "B" Power Unit is a perfected unit behind which is our subjected to extremely powerful high unconditional guarantee of satisfaction. frequency currents having a frequency of several million cycles per second. It is an electrically correct unit. Into it has been built every element This brings the metal of the tube that makes for It can parts practicability. to a brilliant orange-white heat that volts, thereby permitting the supply 150 drives whatever residual gases may use of big power tubes. A variable have been in the metal out into the amplifier control allows the use of any intertube so that the vacuum pump may mediate as in the case of voltage Super- draw them out through the exhaust. and other of receivers Heterodyne types The bombarder is quite a heavy and more than one requiring amplifier voltage. complicated looking piece of appar- The Unit is moisture proof and is tested for atus which can be moved around the 2500 volts between input and output in order floor on wheels, but the active element to eliminate all fire hazard. which js used to heat the tube is simply a small coil of about 3" in diameter MODERN ELECTRIC MFG. CO. * Toledo, Ohio and a dozen turns. When the high frequency currents are running through this coil it will rapidly heat up any piece of metal which is held near it; glass, paper or even a match would keep quite cool even when put on the inside of the coil due to the fact that these articles are not good conductors. After each of the several tubes in the process has been bombarded four Better Condenser' times, the engineer adjusts several of the various stop-cocks in his system of A constantly number of the American increasing discriminating glass tubing and we learn that he is Radio Public call a filter condenser a "TOBE." They have learned now the desired amount of as we have known that the "TOBE" is "the better condenser." letting pure gases into the tubes. After this opera- When you build your improved Raytheon plate-supply unit, tion he directs the flame from a blow ask your dealer for the "TOBE" B Block, containing in one unit all the required capacities and at a saving of $2.50 over the cost of torch at the top of each bulb where it condensers. And separate Raytheon recomends "TOBES" as un is joined to the tubing, and with a dex- surpassed by any for use in Raytheon circuits. terous sweep of the wrist removes each finished tube with its vacuum tight tip carefully sealed by his torch. CORNHILL "What will be the fate of these new BOSTON, MASS. rectifiers?" we ask, rather hoping that ADVERTISEMENT ^RAYTHEON^

r Tested and approved by RADIO BROADCAST it RADIO BROADCAST ADVERTISER 163

B-eliminator is the "B" unit Thordarson has Even on the we have witnessed the first of a new Raytheon first plate supply approved. modern it without hum, when built with the line of Raytheon tubes which would all-frequency amplifiers operates specially designed some day revolutionize the radio market. Of course there is the possibility, it seems, but these are merely a half dozen of a thousand different models that have been made and put to up 'Raytheon-type almost as many different tests during From each ex- the past few months. Transformers and Chokes model some little detail is perimental Transformer R-195 Larger in capacity learned that helps in the production Will not heat up in continuous service- Un- of Raytheons of greater ruggedness Separable plug, 6 foot cord attached. at deal- and But the fundamental conditionally guaranteed. Price, reliability. ers, or by mail, $7.00. and basic upon which rec- principle Choke R-196 Completely shielded and for a tifiers operate have been known mounted in large steel case. Binding posts neat 60 long time and no revolutionary change at base for assembly. Capacity milliamperes. Unconditionally guaranteed. in these can be principles expected. Thordaraon Transformers and Choke Price, at dealers, or by mail, $5.00. are Standard >ri tlie B-eliminators of leading makers Write jar Hook-up Bulletin Research, and Research Workers THORDARSON ELECTRIC MANUFACTURING CO. let take a look at some of Transformer specialists since 1895 Now us WDRL0S OLDEST AND LARGEST EXCLUSIVE TRANSFORMER MAKERS the other activities. To investigate Chicago. U.S.A. and understand them all would re- qure more time than is at our disposal, but we may at least get a smattering of what it is all about. Out in one of the smaller rooms we find what looks like the realization of O.K.'d a radio experimenter's dream, with a by few chemicals, a delicate balance scale, and other nameless apparatus thrown OARQSTAT RAYTHEON in for good measure. Over in an al- cove we see a desk and table, and seated there two engineers earnestly because CLAROSTAT passed with flying discussing a sheaf of papers covered with figures and rough diagrams. It colors the most searching tests Raytheon is we that the fundamental here, learn, had ever a variable resistance. work on the phenomena of gaseous given conduction is done; work that may have no immediate value but is yet CLAROSTAT has no equal for voltage con' blazing the trail for the practical applications in the years to come. From trol in "B" Battery Eliminators. Only the studies made here will come new CLAROSTAT you a wide range of applications of filamentless rectifiers gives in far different fields from those in control and a current carrying capacity which are now as they recognized of other variable leaders. greater than that any dark We are now introduced to the resistor. "sanctum sanctorum" where the glass blower does his work. He likes to S. host other known eliminator have just the right amount of darkness P. A of nationally so he can tell colors of the by changing makers hare also approved and endorsed Ctarostat glass just when it is ready for man- ipulation into some of the intricate bends and bulbs that are constantly If your dealer cannot supply you, write direct in demand. A slight draft of air might have a bad effect on both the temper of the glass and the glass- American Mechanical Labs. Inc. so close the door . worker, we quietly 285-287 North Sixth St., N. Y. and proceed. Brooklyn, Out in the main room again we see a whole wall dotted with rectifier bulbs Special types for "A" and "B" Battery Eliminators mixed with carbon lamps, all lighted to various of It is for Manufacturers degrees brilliancy. $2.25 here that the experimental models are put through their final test, a life test ADVERTISEMENT

Tested and approved by RADIO BROADCAST 164 RADIO BROADCAST ADVERTISER

under heavy load to see how they will stand up in service. And it is on this test more than any other that the work of the laboratory staff is judged. Upon taking an inventory of the Transformers Chokes laboratory personnel, we find that one man is a physicist of ten years' experi- 509 Full Wave ence on conduction 514 20 Henry gaseous problems, Manufactured in five of these in work at Raytheon Tubes years graduate 25, 40, 50 and 60 Harvard Another is a $6.00 List University. cycles professor of electrical engineering at M. I. T., in charge of graduate research Build your Eliminator with Dongan B-Power Units the product of an organization at that Institution. Three of the staff that has specialized in transformers for 15 years. Correct engineering principles are graduates of the same school with and exactness of construction are Dongan characteristics that you'll appreciate in the of Master of Science, and your finished Eliminator. degree three others are engineering graduates. Set Manufacturers An addition to our standard models we will build for you special unmounted Transformers and Chokes. Many of the practical production DONGAN ELECTRIC MANUFACTURING CO. problems are solved by John A. Spen- cer, inventor of the "Click" 2991-3001 Franklin Street Detroit, Mich. Spencer Thermostat now used in automatic ^TRANSFORMERS of MERIT for FIFTEEN YEARS Hi' electric irons. Of equal ingenuity is his brother, P. L. Spencer, who has had many years of practical radio experience with the Wireless Specialty Company and the Submarine Signal Whatever Power Supply Company. A competent and serious group of men is this. To know that Unit You Build they are devoted to but one main prob- the of A. C. there are Potter Filter lem, proper application power to radio receivers, gives one con- Condensers Made for It fidence. But let us resume the role of observer, since we came to learn. It is absolutely necessary to have the best contests they have proved their exceptionally long densers to have good results with either your "A" life under ham continuous usage. or "B" Supply Unit. Potter Condensers meet every requirement: they arc made with the Made in three tyo-s A B, and C, tested 300, 500 and 1000 voles D. C. Each best foil, best insulation, best impregnating com- respectively. type Maintaining B-Power Quality pounds obtainable. They remove all traces of comes in all capacities. Special models for Ray- theon "B" A. C. impulses, eliminating all hum. In many Eliminator, Raytheon Power Pack, etc. Over here at another bench we see a At your dealers An young fellow putting a finished B- or write direct FILTER American-made power unit through its paces. This to us ^Product seems rather strange since we understood that the Raytheon Company POTTER MANUFACTURING CO., NORTH CHICAGO, ILL. made nothing but the rectifier tube. And yet in a large steel cabinet near

this bench we see some 1 5 or 20 B- power units of all shapes and sizes, some with switches and W-B-3 Two Voltages * Webster meters, knobs, Detector and Amplifier $47.50 and others with sides One variable resistance taps plain metal with the barest minimum of and W-B-4 Three Voltages with taps power tube tap - - - - 50.00 controls. These units have been made Two variable resistances SUPER-B various manufacturers and by W-B-D For 110-125 D. C. they Three Voltages - . . . 25.00 have been submitted for test and ap- 15% to 50% more volume and better tone quality on Prices slightly higher in Canada and the distant stations as well as locals. in stations never proval by Raytheon laboratory. West of the Rockies GETS Brings before logged. All parts properly balanced in new Webster The standard test consists of (i) circuit an filter improvement particularly noticeable in high- the at var- powered receivers. measuring output voltage ious loads on the detector, radio fre- It supplies steady, noiseless flow of plate current and thereby clarifies signals and builds up volume. It forever eliminates noises quency and audio frequency taps; fron run down "B" batteries and the expense of replacing them. (2) detecting any hum or noises that It reduces cost of set to minimum. connect it to operating Just exist at of the above loads light socket and it keeps your "B" power always ready at full effi- may any ciency costs less than j^ of a cent per hour. Delivers up to 60 on a sensitive electrical circuit; (3) milliamperes at 150 volts ample for most powerful set. Note testing the reliability of the controls especially Model W-B-f with two variable resistances and three voltages with power tube tap. This is adjustable to any set and and switches; (4) testing the condens- is essential for those tube in last audio using power stage. ers with several times the normal op- Write us to-day for full information and Free booklet, "Improving to make sure of their Your Radio." erating voltage ability to stand up in service and (5) THE WEBSTER COMPANY a test the Compact 5j" high, 4%" wide general inspection and of 3506 West Lake Street 111. 10" long overall Chicago, ADVERTISEMENT

Tested and approved by RADIO BROADCAST RADIO BROADCAST ADVERTISER 165

durability and quality of all parts used in the construction. Let us stop for a moment to consider what this means to the average radio fan who has no laboratory facilities of his own to make such tests before selecting a B-power unit. It means that he now has a standard upon which he can rely. Of course different units will have different features and prices, backed as they are by many manufacturers in different parts of the country, but the buyer has the satisfaction of knowing that any Ray- theon unit will do the job for which it is designed and rated. This is true not only of the complete units, but of the separate parts for home built units which have been tested and approved in the Raytheon laboratories. In other words, there is one branch of the radio industry in which all products must reach a certain standard of performance before they are offered to the public. Not only does the Ray- Reliable theon Company maintain rigid test and inspection of its own product, the rectifier tube, but it actually goes so the who far as to protect consumer PeribrmanceAlways buys a B-power unit using that tube.

Every baseball team has its "pinch hitter." He's the man who can step The Raytheon Policy up and perform under any circumstances. And that is the way you learn to feel about your radio when it is equipped with a Majestic Super-B. The full significance of this policy and how it is carried out is not appre- You clear tone in of volume under all sorts of receptive ciated without some thought. One get fine, plenty conditions. The cost of operating set, too, is reduced to the infinitesimal question that immediately arises is, your tenth of a cent an hour. "What prevents any manufacturer from putting out a Raytheon B-power and unit, without having it tested and ap- When you consider these advantages you will realize why engineers proved by the Raytheon laborator- technical experts who know radio equipment specify the Majestic Super B. ies?" In the first place any manufac- Its technical superiorities are: Two chokes of 41 Henrys each and 20 micro- turer of standing who values his repu- farads of capacity in the filter circuit. The use of 30 gauge wire of low re- tation is glad to have his product tested sistance for winding the chokes and transformer also permits voltage regula- out even- by specialists who can offer suggestion of better control. Unusually large condenser bank smooths tions as to its improvement. The re- trace of ripple with a wide safety factor to spare. liable Companies do not wish to put out a unit that would not pass Majestic Super-B Current Supply, complete with Raytheon Tube, the most severe tests. They welcome capacity I to 12 tubes, including the use of new 135-150 volt power this service by an unprejudiced organ- tubes. ization. 1 10 volt, 60 cycle. Price $39-5 If there are Companies who do not see the wisdom of this policy the Ray- The Majestic Standard-B is a smaller B current supply unit, designed for of tubes or 201 one 1 12 theon Company exercises its privilege sets having not more than 6 2OiA-type 5 A, plus type of protecting the consumer by refusing of 135-volt power tube. to sell tubes to the offender. Even the with most intrepid "bootlegger" would hesi- Majestic Standard-B Current Supply, complete Raytheon tate to put out a Raytheon B-power Tube. 1 10 volt 60 cycle. Price $32.50 unit minus the tube and against the competition of approved units. All Raytheon tubes are sold through the GRIGSBY-GRUNOW- HINDS CO. Manufacturers of approved B-power units. In the unit buying complete 4550 Ave. Illinois with the Raytheon tube satisfaction is Armitage Chicago, assured. ADVERTISEMENT RAYTHEON

Tested and approved by RADIO BROADCAST if 166 RADIO BROADCAST ADVERTISER

The Radio Broadcast

SHEETS

INQUIRIES sent to the Questions and Answers department of RADIO BROADCAST have heretofore been * " answered either by letter or in The Grid." From this issue on, however, the latter department will be discontinued, and all questions addressed to our technical senice department will be answered by mail. In " place of The Grid," we present herewith the first of a series of Laboratory Injormation Sheets. These " sheets will contain much the same type of information as has appeared in The Grid," but we believe that the change in the method of presentation and the wider scope of the information in the sheets, will make this section of RADIO BROADCAST of much greater inter est to our readers. The Laboratory Information Sheets will cover a wide range of information of value to the experimenter, and they are jo arranged that they may be cut from the ma gamine and preserved for constant reference. We suggest that the series of Sheets appearing in each issue be cut out with a ra^or blade and pasted on filing cards, or in a note book. The cards should be arranged in numerical order. Several times during the year, an index to all sheets previously printed will appear in this department. " Those who wish to avail themse'ves of the service formerly supplied by The Grid," are referred to page 175, where it is explained in detail.

DeLuxe

C7T REPUTATION for fine dSv transformers that has been No. 1 RADIO BROADCAST Laboratory Information Sheet June, 1926 maintained for over a quarter-cen- tury! Today this high standard of manufacture is more apparent than ever for radio has adopted each of Regeneration the advanced, dependable AmerTran tinue to oscillate even if the radio cease Products as the leader in its field. METHODS OF CONTROL waves coming in. The loudest signals arc obtained just The new AmerTran DeLuxe Audio TXTHEN radio waves of the frequency to which before the tube "breaks into oscillation." Signals * the antenna circuit is tuned are being received can be received even while the tube is oscillating if Transformer actually puts the devel- the high frequency currents flowing in the coil pro- the oscillation frequency is kept exactly the same opment of the "audio side" ahead of duce high frequency variations in the grid potential as the carrier-wave frequency. which, in turn, produce high frequency currents existing acoustical devices. Faithful (of considerably greater energy) in the plate circuit, If we could "feedback" some of this to amplification with natural quality plate energy increase the original potential applied to the grid, it over the entire audible range is con- migl.t help to increase the original potential applied to the This can be done in several A sistently obtained with this audio grid. ways. very common method is shown in A. transformer. It sets a new standard The essential addition to the circuit is the coil in This is called the "tickler" coil, of audio amplification. the plate circuit. and upon being brought up near the antenna coil its mutual inductance, or transformer action, affords As the receiving set of the future is des- a means which energy from the plate circuit is tined to be operated) the American by power fed back into the antenna circuit. The tickler must Transformer is now two l: Company offering be connected the right way too, for if the connec- units of the finest type especially adapted tions are reversed its effect will be to reduce the to the use of the new 7^2 volt power tubes antenna current instead of increasing it. If the There are several methods of controlling feed- either a variable tickler as in A or a in the last audio stage. These are the Amer coils are brought too close together, a point will be back, by by shunted across a fixed tickler Tran Power Transformer and the Amer reached where more power is being fed back to the variable resistance antenna circuit than is being dissipated therein. coil. Another method is by the use of a variable Choke which are strictly up to standard, and The tube is then said to be oscillating, and will con condenser, as illustrated in B. may be depended on in the type of audio amplifier required. The Power Transformer also has filament supply windings for the power tube in the last stage and forthe rectifying tube, and supplies sufficient plate current, after rectification, for the operation of the set. RADIO BROADCAST Laboratory Information Sheet June, 1926 AmerTran De Luxe, 1st Stage $10.00 AmerTran DeLuxe, 2nd Stage 10.00 AmerTran AF-7 (3V4-1) .... 5.00 Factors Radio AmerTran AF-6 (5-1) 5.00 Governing Receiving AmerTran Power Trans. PF-45 15.0O AFFECT DISTANCE the material in which they flow. In the case AmerTran Power Trans. PF-52 HOW THEY 18.OO of ordinary telephony over land wires, the AmerChoke is such that the current is about Type 854 6.00 'TWERE are three main factors governing the attenuation 1 distance that can be satisfactorily covered be- one third, at the end of every ten miles, of those tween a given transmitting station and a given re- of what it was at the beginning Write today for interesting free booklet shows ceiving set. These can be siated as follows: ten miles, and a little calculation "Improving the Audio Amplifier" that to talk across the continent without 1 . The amount of interference. 2. The inverse distance effect. As the radio any amplifiers inserted along the line would waves spread out in all directions from the require an immense amount of power. Yet, by AmerTran Products Are Sold Only the Insertion transmitting stati9n their strength naturally at Authorized AmerTran Dealers decreases. At twice the distance, their am- of fifteen plitude is halved; at four times the distance, amplifiers or sta- AMERICAN TRANSFORMER Co. it is only one quarter, etc. This same fact relay could also be expressed by saying that the tions along the the 178 Emmet Street Newark, N. J. strength of the signals is inversely proportional line, to the distance. A curve illustrating this is attenuation The law is DEALERS The Sale of AmerTran Radio Prod- shown in the accompanying diagram. pre- curve is based on ideal conditions, and neglects vented from acts East of the Rockies is handled exclusively etc. 05 "getting un- by the AmerTran Sales Company, Inc., 178 Emmet absorption by buildings, fading, 3. which is a different der way," Street. Newark, N. J. Direct to dealer sales The attenuation, quite pol- and a ridicu- Some territories are thing. It acts simultaneously with the inverse icy. available for parts small dealers and service stations. distance effect to reduce the amplitude of the lously waves. Attenuation of the waves is due to power is their being dissipated in the form of heat. enough for Whenever the waves strike any object in which proper trans- - Transformer Builders for they can produce electric currents, the cur- continental 1 2 789 10 land line te- Over Twenty-Five Years rents are produced at the expense of the energy 3456 of the waves and heat up, to a minute degree, DISTANCE lephony.

Tested and approved by RADIO BROADCAST LINCOLN RADIO BROADCAST ADVERTISER 167

The Crosley 5-tubf-5-38 Excerpts All the volume, selectivity and burity of tone available in the best f-tube setptut from Telegrams: the Cresfendon The "Tested RFL-60 within Crosby S-t*bt~RFl^6O your A set of marvelous performance two blocks of local 500-watt and beautified by the ' nix tic decorative (C/>(^ broadcasting station, using panel twenty-five foot wire on floor for aerial. We picked up stations all over the country and when local station came in tuned it out and picked up WSAI at 319 meters. The local station is 270 meters. This is the only set ever tested under these condit ions that would tune this station out at any point on dials." The Crosley S-tube-RfL-7S Simplicity and speed in tuning, Decatur, 111. fidelity of tone and decorative beauty, enhanced by the art panel . . . . . The 4-n,kc- 4-29 "We tested one of new Crosley your jn which the Crescendon is equal RFL60 sets here in our build- to one or more additional lubes an antenna about 75 of tuned radio jre- ing using auency amplification feet long and directly under and parallel with our transmitting aerial. Theexception- al selectivity of the Crosley receiver us to tune permitted Prices slightly higher west of the Rockies out our station WTAX, just as easily as we would tune out a Chicago station." Strea- tor, Illinois. By Expressed Opinion of "An RFL60 tested in competition with other receivers of much higher price proved its The Fans The Greatest Radio unquestionedsuperiority. new Crosley models offer the greatest values on the radio market." Kansas City, Mo. Values Ever Offered!

"The Model 4-29 is classed with the Model 5-38 Trirdyn. Real sensitivity and selec- bringing in Pacific points with performance! Amazing ample volume, using a Musi- tivity! Marvelous tonal qualities inspiring volume. cone. RFL-60and75arevery selective. Haveseparateddis- And surpassing beauty ! tant stations on less than one degree on the dial. Have log- Read, in the column at the left, the enthusiastic Mexico and Pacific ged City comments of a few of the radio fans who have Coast Stations with plenty of many volume." Miami Fla. voluntarily written or wired us their praise.

"The RFL sets outstripped True radio values at astonishingly low prices. Hear much outfits. higher priced a Concert at dealer's. These sets bring in Canadian, Crosley your nearby Crosley Cuban and Mexican stations as as those on easily nearby For descriptive catalog write Dept. 20 states.' Glasgow, Ky. THE CROSLEY RADIO CORPORATION, CINCINNATI, OHIO What's the idea of a keeping Powel Crosley, Jr., President fellow up all night foolin' around with that darned Owning and OperatingWLW, first remote control super-power broadcasting station inAmerica little 4-29? I've been in the radio game for seven years and was beginning to believe that there wasn't a set in the world that would keep me up late but when that little 4-29 started to pull in Houston, Texas and with such extreme volume I sat and took notice. CROSLEYT T E R. COSTS LESS up I got California stations with unbelievable volume last night. KFI came in so loud that it could be heard over a * block on a Musicone speaker. I've gotten over one hundred and twenty -five stations in fntertainment CornerQ RAMihc for only three nights. Spring Valley. 111. Manufactured under Armstrong U. S. Patent No. 1,113,149, or under patent applications of Radio Frequency Laboratories, Inc.

Tested and approved by RADIO BROADCAST 168 RADIO BROADCAST ADVERTISER

Why No. 3 RADIO BROADCAST Laboratory Information Sheet June, 1926 THE The Browning-Drake Receiver

SHEET No. 4 is shown a of the QN diagram mounted so as to make its position, in re- ^-* popular Browning-Drake receiver, which, in lation to Lz, variable. METALLIZED its form, was described Glenn improved fully by Fi, Fa, FS, Fixed filament control resistances to H. Browning, one of the designers, in the December match the type of tubes employed. 1925, RADIO BROADCAST. The first article appeared J Single-circuit filament control jack. in this for 192-1. magazine December, Three stages G .00025-mfd. grid condenser and leak (6- of audio are impedance-coupled amplification em- megohm) . in this circuit. The constants of the circuit T 2 ployed Ti. , Two uv-199 tubes. as are as follows: shown, T3 , T 4 , Two uv-201-A or High-mu tubes. If the latter are used, Fi and Fa may be Ci .0005-mfd. variable condenser. omitted. Ca .00025-mfd. variable condenser. TS, Semi power tube. Cs .00025-mfd. fixed condenser. C4 .0.1-to 1.0-mfd. fixed condenser. Although choke-coupled amplification is shown in Cs ,0001-mfd. fixed condenser. the diagram, the circuit may be used just as well Li 46 turns No. 20 d.s.c. wire on a form has 3 inches with transformer or resistance -coupled audio stages. METAL long been recognized in diameter, with a center tap. If the transformer-coupled form of amplification is as the best of electrical conduc- La 75 turns No. 20 d.s.c. wire on a 3-inch form. desired, only two stages will be necessary for aver- L,3 24 turns No. 28 d.c.c. wire wound in a groove age requirements. and under the filament end of the The is tors. The metallized resistor gives placed center tap employed on the antenna coil secondary. for use when one's antenna is in excess of 100 feet conductive resistance and abso- L4 20 turns No. 28 d.c.c. wire wound on a 2$- in length, but it is advisable to employ a single-pole inch form to fit in grid end of secondary (L2). double-throw switch at this point so that either lutely silent operation. I 100-henry choke coils. antenna connection may be used without undue R 1 -megohm grid leaks. changes being necessary. The reason for this is that N Neutralizing condenser, consisting of a small the capacity of the antenna has to be taken into brass disc about an inch in diameter, consideration as well as its length.

Why I entered the RESISTOR No. 4 RADIO BROADCAST Laboratory Information Sheet June 1926 Business In concentrating upon the reduction of losses in coils The Browning-Drake Circuit and condensers, too little attention has been given to the development of an equally vital factor efficient resistors.

Resistance is, at once, radio's greatest enemy and best servant. It is the balance wheel. It is used to control power houses, radio stations and even radio receivers. We have studied the shortcomings of modern fixed resistors and now offer the result of much research and experimental work the LYNCH METAL- IIZED RESISTOR. Arthur H. Lynch

^IXED RESISTOR" r A- B- B*45 B9P 8*135 C C-4H C-9

Complete data, on the sizes of the various units, used in this circuit appear in Sheet No. 3

No. 5 RADIO BROADCAST Laboratory Information Sheet 1926 PRICES: June, .25 to 10 Megohms .SO above .01 to .24 .75 Transformers .001 to .01 #1.00 ^L PRIMARY-SECONDARY RATIOS secondary current as the secondary voltage is related to the primary voltage. An auto transformer The LYNCH METALLIZED FIXED RESISTOR ordinary commercial iron-core transformer is no different except that the winding having the ^HE* consists of two coils of wire wound on fewest turns is a of the other a concentrated coating of simply merely part winding. comprises the same core. So as the of such a Thus one coil is of long secondary only required. metal one-thousandth an inch thick transformer is open circuited, or connected to some- There are several simple formulas regarding upon a glass core and sealed within a thing with an impedance so high that not much transformers that are quite useful: current flows, we have a very simple relation be- glass tube. Each Resistor is warranted Primary Turns Primary Voltage tween the voltage delivered by the and to secondary noiseless, impervious moisture, and that applied to the primary. This relation states Secondary Turns Secondary Voltage that the ratio of these two is of permanent resistance value. voltages the same as is Primary Turns Srcondmy furri-nt the ratio between the primary and secondary turn numbers. A ten to one transformer would Secondary Turns Primary Current The LYNCH label is your guarantee of step-up be one with ten times as many turns on the second- Primary Voltage Secondary Current accuracy, dependability and satisfaction. ary as on the primary. Secondary Voltage Primary Current If your dealer cannot supply you, order A transformer corresponds to gears in mechanics. If an of or levers we increase Values obtained by the use of the above relation- direct and we will ship postpaid. by arrangement gears a mechanical force ten times, we know instinctively ships will serve as fairly close approximations. In that we must expect the part of the arrangement general, the smaller the load being supplied by the that is exerting the "stepped-up" force to move transformer, the more correct this data will be. ARTHUR H. Inc. ten times as as the where the LYNCH, slowly part original Ordinary Transformer force is If we choose to gain in Auto Transformer Manu/octurers of Radio Devices being applied. Usmg Two Coils force, we lose correspondingly in speed, or else we Fisk Bldg., Broadway &. 57th Street could get "something for nothing." The electrical transformer is not a source of power. It merely New York, N.Y. changes the power put into it at one voltage into the same power (with a small percentage loss) at a DEALERS write vsl different voltage. Hence, just as the speed went down in the mechanical case, so the current is less in the high tension or high voltage side of the transformer. The primary current is related to the RADIO BROADCAST ADVERTISER 169

"I've just had a lesson in radio economy, and, believe me, it's illuminating"

"I WENT into my radio dealer's this noon for a couple of On 1 to 3 tubes Use Eveready No. 772. Eveready 'B' Batteries and said, 'Tom, give me a pair of On 4 or more tubes Use the Heavy Duty "B" Bat- Eveready 45-volt "B" Batteries No. 772's.' teries, either No. 770, or the even longer-lived Ever- 'How many tubes in your set, Jim ?' he asked. eady Layerbilt No. 486. 'Five,' I answered. On all but single tube sets Use a "C" battery. 'Then what you want is a pair of Eveready Layerbilt When following these rules, the No. 772, on 1 to 3 tube No will last for a or more 486V sets, year ; and the Heavy Duties, on 'Why?' I asked. sets of 4 or more tubes, for eight months or longer. 'Because the Eveready 772's are meant for sets having We have prepared a new booklet, "Choosing and Using one to three tubes. With average use of the set, and used the Right Radio Batteries," which we will be glad to send with a "C" battery*, they should last a year or longer. But you upon request. This booklet also tells about the proper on a five-tube set, with average use and with a "C" battery, battery equipment for use with the new power tubes. they will only last about four months. *NoTE : A "C" battery greatly increases Anyone with a four or five tube set the life of your "B" batteries and gives a of unobtainable without should buy a pair of Eveready quality reception it. Radio sets may easily be changed by No. 486. Used with a Layerbilts LEFT-A'O. 486, any competent radio service man to permit 4. 5 w innre "C" should last for the use of a "C" battery they eight tubes. 55.50. Battery. months or longer.' and " RlGHT-Ecer- Manufactured guaranteed by but the 772's cost 'Yes, only eadl/ Dry Cell Radio"A" Bat- NATIONAL CARBON COMPANY, Inc. $3.75 each,' I said, 'and the Layer- tery, 1 Vt volts. New York San Francisco bilt $5.50. There's some difference.' ' Canadian National Carhon Co., Limited 'Well, figure it out for yourself,' Toronto, Ontario said Tom. 'Two sets of 772's should Tuesday night means Everyready Hour last about you eight months, and 8 P. M., Eastern Standard Time, will cost you $15. One set of Ever- through the following stations: eady Layerbilts should last about WEAF New York vr ski-Cincinnati wjAR-Previdence WT \M-Clevtland will eight months, and cost you EVEREApv WEE i-Boston w wj- Detroit only $11.'" Radio Batteries WY \-Pkiladehhia woe- Davenport WCK ( The simple rules for this satis- last Buffalo co Minneapolis -they longer wcAK-Pittsburgk ( St. Paul faction and economy are; 5/. Louis

Tested and approved by RADIO BROADCAST 170 RADIO BROADCAST ADVERTISER

No. 6 RADIO BROADCAST Laboratory Information Sheet June, 1926 Dielectric Constant

ITS EFFECT ON CONDENSER CAPACITY the larger condensers, of one or two microfarads capacity, oiled paper is generally used. Its use '"PHE capacity of a condenser depends upon helps to reduce the cost and the break-down volt- -I several different factors, the most important age of such a condenser will be greater than if of which are: 1. Area of plates; 2. Number of plain paper is used. plates; 3. Distance between plates; 4. The dielectric Solid dielectrics have the disadvantage that if or insulating material between plates. they are once broken down and punctured, due to excessive voltage, they are rendered useless. How- The effect of the first three quantities on the ever, if a liquid dielectric is used, this disadvantage capacity is easily calculated by means of formulas cannot exist, and for this reason laboratory con-

Vaseline

SUPER-EMISSION RADIO TUBES

Excel in All Characteristics

Standard Types Power Amplifiers Short or Long Prong Bases

JOBBERS DEALERS A few territories open for exclusive distribution

Write ^ow for 'Detailt

CABLE SUPPLY CO. INC.

Sales Offices 907 Broadway New York RADIO BROADCAST ADVERTISER 171 (Sis RH"amm ar Ivindl )

Oton, D. C. Rued evening during the t'sts, I logged in no less than a dozen stations. However, regenerative sets absolutely ruined reception. I was able to make out only partly some station in Testimonials on the South America operating at 300 meters. From results Hammarlund- Roberts obtained I am sure that Ha-'imarlumi-Roberts is cap- Receiver able of Trans- Atlantic Re- ception. I feel that Ham- irarlund-Robertfi is one of the best buys in radio to- day. G. J. A. Electrical Engineer Last night I received PWX at Havana, Cuba on the loud speaker. Other stations that I get regularly are : WFOB at Atlanta, Williamiport, Pa.

Georgia ; Nashville, WSM, We have tested the Ham- Tenn. ; \VGY. Schenectady, marlund-Roberts and find it X. Y. ; \\SMB. New Or- to be exactly as you rec- leans, Louisiana ; CZE, ommended. Surprising vol- Mexico City, Mexico. ume and very clear and Ready to back your set deep tone, se- against any other of the exceedingly lective. H. B. S. same size. Logged over 100 stations the first week. R. F.

Lansing, Mich. On the first night of the Hxtt- of is an feature of the Hammarlund-Roberts Trans-Atlantic I . Montana assembly outstanding Tests, had on SIMPLICITYreceiver. Thousands of amateur builders in all of the en- PWX, Havana, Cuba, During tests the Hammai- parts country testify the loud speaker, so loud lund- Roberts was installed thusiastically to the ease of assembling this circuit and express their delight at the that it could be heard at in the Butte Radio Club times all over a six-room Headquarters and dials set results secured by their own handiwork. house. for 2LO. Immediately we Have not Aeard of anyone were able to get through this record. I have The secret of their success lies in the flawless of beating for a few mom ents . long technique every part entering ten witnesses to this recep- enough to hear announce- into the assembling of this set. The Hammarlund-Roberts receiver the tion. J. R. ments made in English, represents German, anil Spanish. This composite achievement of ten leading engineers, backed by ten of the best known man- was followed by both in- ufacturers of radio is the of a has been chosen 13 strumental and vocal music. parts. Every part work specialist and M. R. C. because it meshes easily and yet efficiently with every other related part in the set. Morristown, Tennessee I assembled the Hammar- After you have assembled this receiver you will want your friends to call around lund.- Roberts Receiver in one day's time. The set is and for themselves as a radio And will be highly efficient and up to \\heeling, W. Va. judge your ability engineer. your pride all claims made by you. justified. The Hammarlund-Roberts receiver combines remarkable volume and On January 25th, 1926. I I have owned many factory Picked up 7EAJ of Madrid, sensitivity with an unusual degree of selectivity and tone quality. As for distance built sets and will say that the Hammarlund-Roberts is Spain. Reception was so on either side enthusiastic users of the Hammarlund-Roberts loud and clear from the you have testimony by superior to them all. This cone speaker. It was de- in all sections of the country. A perusal of these comments will revolutionize all set is capable of building up tremendous volume with- sirable to cut the volume desire to of considerably. your previous ideas of five-tube performance. Should you verify any out distortion and behaves I have received CZE of like a thoroughbred. these reports we will be glad to furnish with full name and address on request. Mexico City and PWX of you I get New York, Atlantic City, Jacksonville, San Havana. Cuba ; both of these stations I have re- Francisco Montreal. Havana, cfivi-d before these tests Cuba, and Mexico City. however. I have logged over 90 stations and more are coming in all the time. N. E.C. 4Ta m m a rl u n d oDerts Hammarlund-Roberts 1182-A Broadway, New York City

-**| SEND FOR THIS BOOK

Contains step-by-step instructions on the assem- I bly, wiring and operation This famous instru- of the Ha mirarluml- Rob- UNION erts. illustrated ment and other parts Fully ; n shown here are some PHONE TIP > ost complete "How to of the quality units Build It" radio book ever in the Hammarlund- JACKS published. 25c. DIALS and SOCKETS . Knbnls. RHEOSTATS

Tested and approved by RADIO BROADCAST 172 RADIO BROADCAST ADVERTISER

STARTLING! A Department for the Exchange of Ideas and Sugges- Two New Products by tions of Value to the Radio Constructor and Operator

General Instrument to this department are welcome and those used will be CONTRIBUTIONSpaid for at the usual rates, that is, from two to ten dollars each. A prije of twenty-five dollars is given for the bist ilea used during each three-month period. The prizewinner for the last period was announced in the May RADIO BROADCAST. Manuscripts intended for this department should not exceed about three hundred words in length, and should be typewritten. Little consideration can be given to manuscripts not typewritten. Envelopes should be addressed to this department, RADIO BROADCAST, Garden City, New York.

A WOODEN STAND TO HOLD A an arm, C, extended outward from a verti- MACHINIST'S DRILL cal support, D. A single large wood block, E, forms the base. The base is to amateur mechanic, interested hinged the work-bench or other base ordinary in obtaining additional service by strap hinges, permitting of the entire THEfrom a limited number of tools, structure tilted. will find in the wooden stand fixture illus- being Screws secure the several pieces of wood trated in Fig. i, a means forobtainingawide forming the frame, making a fixture that is extension of use from the hand type of fitted in an hour or so, with machinist's drill. readily up only tools. With this fixture, and a hand drill secured wood-working The dimensions, as will be evident from to the frame structure, it is possible to do the drawing, will vary with the size of drill drilling work with great facility and ac- available. curacy. Drilling glass, deep drilling in GEORGE A. LUERS, steel, cutting with an expanding type of Washington, District of Columbia. drill, and similar jobs requiring care and patience, are possible with this form of A SIMPLE CONE LOUD SPEAKER G. I. Shielded Units drill fixture. ALTERATION The same fixture also of Are single stage T. R. F. Amplifiers used inter- permits holding of the drill changeably as detector or amplifier increasing SB- work horizontal, through tilting ONE speakers sometimes develop a lectivity and sensitivity of any set. frame. This position enables small parts buzz or rattle that cannot be over- CAN BE USED to be turned up from pieces of brass and c come by ordinary mechanical ad- As complete Receivers using i to 8 tubes steel rods, with a file for a cutting tool. justment. This will be especially noticea- To replace old tuning units The merits of this stand will be evident ble on fairly weak volume, causing a blurring To add R. F. to set. Amplification any to the user of the drill, but a main feature of voices. A practical and proven remedy They cover entire Broadcast band with absolute is the simplicity of its construction. A is to apply a small daub of rubber cement and increase stability amplification. drill support block, A, is the means for of the sort that remains semi-flexible after Each unit a complete receiver in itself with dial, holding the drill and permitting of its drying thoroughly, around the needle socket and SFL condenser in a UX mahogany crys- being moved endwise. Two guide blocks, shaft actuating the instrument, at the taUined aluminum "can." B-B (into which A slides) are attached to point of its connection with the cone tip. On the front side, back off the small nut on the shaft ^--Guides end enough to allow the cement to coat its Hinge surface, and dry before tightening Drill stand tilled on side for filing work the nut, forming thus a rubber washer. After a e the

477 Broadway New York rf i Hand Drill A. H. KLINGBEIL,

FIG. I Ashtabula, Ohio.

Tested and annroverl hv RADIO BRD \nr\sT RADIO BROADCAST ADVERTISER 173

A WINDING FORM FOR. LOW LOSS ceed as follows: Unscrew the cap of the COILS FOR THE ROBERTS SET loud speaker unit and lay the diaphragm, face the table. In the exact center r up, on form described below winding scrape the lacquer off and solder a 3-inch was used to make several sets of length of No. 14 wire. Make sure that the low loss coils for the Roberts THE wire is in the exact center and perpendic- and was found to work hook-up very nicely. ular to the diaphragm. Now the and LIST OF MATERIAL REQUIRED replace diaphragm tighten the on the unit. With a of cap pair pliers A piece of hardwood 2\ inches in dia- bend up a half-inch length of the wire as meter and ij inches thick. shown in the diagram. An machine screw 1 inches with A 1 long, Next the unit should be connected to the nut. phonograph. It may be used with any Thirteen pins yj x 4 inches long

^Victrola Reproducer Take the piece of hardwood and lay out 13 holes around the circumference f inch from the edge. See Fig. .2. Drill a &- Adjustable Loud Unit inch hole at each of the 13 points radially Speaker with the center. Now drill a hole at right angles to the thirteen holes, through the Use the center, using a No. 18 drill. Then put the block in a vise and saw in half on the center fine used to lay out the thirteen holes. Bradk^ohm, After sawing clean up all the rough edges PERFECT VARIABLE RESISTOR with a sharp knife or file; also put an as- on the so that B-Eliminators sembly line, A, Fig. 2, edge for the blocks will be assembled the same way support for Speaker Unit ---" each time. The form is now ready for use. FIG. 3 TT THEN you build your Put the blocks back together using the VV B-battery eliminator 3% machine screw and nut to hold them; make of phonograph providing that it is follow the recommendations then insert the thirteen pins and tighten placed parallel with the reproducer on the of leading radio engineers up the machine screw until the pins are all phonograph; that is, so that the diaphragm by using the Bradleyohm securely held in place. Wind the coil by in the loud speaker is parallel with that for your variable voltage going over two then under two pins until in the phonograph reproducer. control. Several the number of turns are in place. Bradley- required The loud speaker unit should rest on the Now remove the machine screw and take ohms can be used to advan- turntable of the phonograph in a position two halves of the block and tage in B-eliminator, th.e apart you so that the wire will fit into the needle every arc ready to fasten the windings. whether factory-built or receptacle of the phonograph reproducer. Weave cord through them, threading it to obtain several Next tighten the thumbscrew, holding the homemade, in between the cross wires, removing the turned-up end of the loud speaker wire steps of voltage for detector, firmly in the needle receptacle. radio frequency and audio- 832 Nul Thirteen equally With this type of reproducer you are frequency circuits. \spaced the of ' X utilizing properties your phonograph its S* '/>" holes The Bradleyohm with horn and reproducer, yet you may play discs your victrola at any time, by simply loosen- scientifically-treated ing the needle set screw and removing the provides a marvelous range radio speaker unit. of control without steps or ALTON C. CHAMBERLIN, jumps. The turning of the Ballston Spa, New York. small bakelite knob gives you instant control over a wide A BETTER METHOD OF WINDING range. INDUCTANCE COILS Be sure to investigate the ad- "/ii'M" Pin single layer solenoid coil, when vantages of the Bradleyohm FIG. 2 supported by a minimum of di- and other Allen-Bradley THEelectric, is one of the most efficient radio devices for your B forms of inductances. One sees pins one at a time after the wires are frequently eliminator. directions for winding these coils and fasten- securely tied at each pin. have a ing the turns in place with strips of adhesive You wilj now self-supporting paper such as grocers use to fasten low loss coil, with only a small amount of tape, packages. The trouble with this method cord holding it in place. is that the adhesive does not ARTHUR W. SMEALLIE, tape always hold Scotia, New York. firmly. A coil which is much stronger mechani- AN IMPROVED RADIO cally may be made by using strips of paper REPRODUCER which have been coated on one side with beeswax. From a piece of strong, good THIS time, when everyone is quality, paper, cut strips about half an devoting energy to obtaining better inch wide and a little more than twice as ATquality of reproduction from his long as the finished coil will be wide. Melt radio receiver, it seems that 1 a little beeswax and, a small brush, proper using Allen-Bradley Co., should mention a new of radio re- coat one side of each type strip. 278 Greenfield Ave., Milwaukee, Wis. producer which I have developed for my Wrap two or three turns of paper around Please send me latest literature own use. The quality of reproduction is the bottle or other cylindrical object which your on the and other Allen- wonderful because high and low notes are you intend to use as a form. Make the Bradleyohm Bradley radio devices. reproduced alike. The tone resembles paper wrapping wide enough so it will pro- that of the new "Orthophonic" Victrola, ject over one end of the bottle for several Name . . . and the volume may be regulated by the inches. Place the prepared strips, wax volume adjuster on the phonograph. The side out, at equal distances around the Address. diagram, Fig. 3, clearly shows the general circumference of the bottle. Snap a idea of the reproducer. couple of rubber bands over them, and I would suggest that a unit of good qual- everything will be held in place. ity be used and that it be adjustable. Pro- Start winding the coil about a fourth of 1

f Tested and approved by RADIO BROADCAST -if 174 RADIO BROADCAST ADVERTISER

the distance from the ends of the strips. After winding the required number of turns take the brush and paint some melted beeswax across the coil over each of the paper strips. Then run the tip of a fairly lor hot flatiron along the same place. The heat will melt the wax and it will run in between the turns, holding them firmly. Then bend over the ends of the paper strips radio and lay them along the outside of the coil, pressing them into place with the hot flatiron. They will immediately stick. aerials Now grasp the projecting end of the paper which was wrapped around the bottle and pull the coil and paper away - from the bottle. Remove the paper from COPPER the inside of the coil, and the operation is completed. wire The finished coil is strong enough for

COPPER combines A FIG. 4 o the essential J'- any radio use. If several connections are qualities of made to it with bus bar, the bus bar will probably furnish all the support required to suspend it firmly in position in the radio set, and no hard rubber or other material resistance to cor- need be used as a support. H. LESLIE CURTIS, rosion, Lakeport, New Hampshire. tensile HOW TO USE ANTENNA INSULA- strength, TORS TO BEST ADVANTAGE

sketches in Fig. 4 show the high conductivity. right and wrong way of making THEthe lead-in wire twist at the supporting insulators. In A, the wrong way, the chances are that, due to wear, the lead-in will break, necessitating repairs. In B, the lead-in tension and friction is relieved by passing the lead-wire through the hole m the insulator. COPPER & BRASS S. P. EMERICK, RESEARCH ASSOCIATION Oswego, New York. A COLLAPSIBLE ANTENNA 25 Broadway, New York the approach of summer readers might be interested in an WITHidea for an antenna suitable for use in a canoe. This antenna is compact when not in use, and can be made in a

short time. It is efficient too, as I have

1" between knots- '",>String

CHECK YOUR TUBES AND BATTERIES To Set Ever? owner nf New Kadiola, Victor and Brunswick set hould srnd for circular No. 7811 describing this high resistance voltmeter for plugging into phone jackH. Canoe Jewell Electrical Instrument Co. 1650 Walnut St. - Chicago ,A. "26 Years Making Good Instruments' " RADIO BROADCAST ADVERTISER 175

to Readers by the

Technical Information Service to be Conducted by the Laboratory Repair Service for Receivers Calibration and Measurement Work

1ROM this time on, all questions which CALIBRATION AND MEASUREMENT were sent to "The Grid" will formerly THIRD service of the Laboratory which is be handled the Technical Informa- by A available to readers, is the Calibration and tion RADIO BROADCAST Service, Laboratory. Measurement Service. For a moderate fee, That service is maintained under the following wavemeters, coils, transformers, etc., will be rules: measured or calibrated by the Laboratory. 1. subscribers to RADIO All questions from Characteristics of tubes will be measured and BROADCAST will be answered free of charge. the Laboratory is in a position to perform other to RADIO BROADCAST will be 2. Non-subscribers similar services. Communications on this sub- charged a fee of One Dollar for the Labor- ject should be addressed to the Director of the Technical Service. atory Laboratory. All will be answered mail and 3. questions by Our correspondence indicates that an increas- none will be in RADIO BROADCAST. published number of readers of RADIO BROADCAST are _ ing _ The Technical Information Service of the becoming interested in home experimental radio *50.to*25O.a it is to define the Laboratory feels that important work. Many of these newly interested experi- scope of its service to readers. Although the menters have been led into this work through Week in RADIO Service is of very general help to our readers, Keith Henney's articles which appear from time Get into the great new BIG-Pay Industry there are certain demands which can not be met. to time in the magazine, telling how the con- Radio. If you re earning a penny less than $50 a week, clip now. Send for AMAZING" structor can build and use his sim- coupon The Technical Information Service: properly own FREE BOOK. Be A Radio and reliable audio- and radio- Expert, and draw down big 1. Cannot make between various ple wavemeters, comparisons money for the easiest and most frequency oscillators and other valu- kinds of receivers or manufactured apparatus. important fascinating work in the world. able The Calibration and Positions Need 2. of manufactured receivers laboratory apparatus. everywhere. Wiring diagrams for Radio in Service should Experts every i Measurement be of cannot be supplied. This information can be practical help community. Short hours. BIG to these home PAY. Free all the experimenters. book, gives ' secured from the various manufacturers. My charges facts. for consultation 3. Complete information cannot be given about Learn hour. REPAIR QuicklyAnd $2 50 per SERVICE BLANK Easily At Home All success duo sets described in other publications, but in W. Master Radio Engineers will to you." R. all cases will be Black ill.Brook- (wherever possible), inquirers Repair and Service Department show you how to qualify, and at for referred to a source of information where the RADIO BROADCAST Laboratory, quickly easily home, Radio s fine jobs. We guaran- can be obtained. In this data connection, Garden City, New York. tee to train you successfully. -trained men the monthly department in RADIO BROAD- GENTLEMEN: Every day N. R. I. are taking good places in the Best in Publica- I CAST "The Current Radio am enclosing with this blank, a letter to Radio field. Thousands of now the tions" should be of great help, and should be the Repair and Service Department, RADIO openings awaiting "Radio a gold trained man. FREE EMPLOY- m i n e y our consulted. That department records the BROADCAST Laboratory. I am not forward- MENT SERVICE. Many course worth thousands." A. other big features. Get the most important constructional, technical, ing receiver at this time but I desire to R. Herke, Win- my facta CLIP COUPON. nipeg and general radio articles which appear. submit a receiver, which is a ...... receivers or circuits cannot be de- Get This 4. Special described in RADIO BROADCAST for FREE Book! the Technical Service. signed by epair Send coupon below for FREE BOOK "Rich 5. Those who ask questions which cannot be Overhauling Rewards in Radio." answered in the scope of a letter will be re- Read for yourself. No Rewiring previous experience ferred, if possible, to sources where the infor- needed. Common Inspecting and Test schooling enough. mation can be obtained. D WRITE NOW. In response to many requests, lists of the D various groups of apparatus tested and approved RADIO BROADCAST will be mailed by Laboratory NAME to all inquirers without charge. REPAIR SERVICE FOR READERS You ADDRESS. get all service of the Laboratory will be further these sets THEextended to aid readers, and we are glad to announce the inauguration of the "Repair and TECHNICAL INFORMATION Receiving sets, from simplest kind to thousand Service Department, RADIO BROADCAST Labora- INQUIRY mile receiver, inducted to help you learn. AN OFFER. Other feature* The will undertake to BLANK UNEQUALLED special tory." Laboratory repair for limited time only, so ACT QUICK! and put in condition, for a moderate charge, re- Technical Service, National Radio Institute ceivers built by readers. Only sets which have Dept. FU-5. Washington, D. C. RADIO BROADCAST LABORATORY, been described in this magazine will be eligible Garden New York. for this service. In a later number of RADIO City, GENTLEMEN: BROADCAST, the full scope of the Repair and MAIL COUPON Service Department, will be outlined. Those Please give me fullest information on the readers who now have sets which would attached questions. I enclose a stamped they NATIONAL RADIO INSTITUTE like to submit, should communicate by letter addressed envelope. Dept. D. C. with The and Service of the FU-S, Washington. Repair Department O I am a subscriber to RADIO BROADCAST, Laboratory, RADIO BROADCAST, Garden City, and therefore will receive this information Without obligating me in any way, please send me your free book "Rich Rewards in Radio," also New York. Facilities are available to repair free of charge. complete information on your practical, home' readers' receivers at once. The Laboratory has study Radio course. U I am not a subscriber and enclose $1 to no wish to with local radio ser- compete repair cover cost of the answer. Name . . vices, but many readers desire to submit their -Age. sets to RADIO BROADCAST for attention directly Address . and we are glad to accommodate those who feel NAME. .. that their local facilities are not sufficient to Town... .State. help them out of any difficulties they may have ADDRESS..

experienced. , ^

Tested and approved by RADIO BROADCAST 176 RADIO BROADCAST ADVERTISER BOOK REVIEW

A Practical-Theoretical Book Especially for the Beginner

PRACTICAL RADIO. By Moyer and. Woslrel. Published by McGraw-Hill Book Company, New York, 271 paqes (182 Illustrations). $'75-

is a thorough description of the principles and practice of radio reception, UNIFORM HEREwritten for the beginner, and avoiding too technical details whenever possible. The TO A QUARTER OF chief feature of the book is the large amount of - practical data presented, such as the fire under- ONE PERCENT writer's regulations for radio equipment, tables of data on various tubes, instructions for reacti- vating thoriated filaments, a trouble shooting detailed instructions for an SILVER-MARSHALLinterchangeablecoils were the hit of last season. They chart, putting up It for and wave and were the first completely interchangeable, antenna, making using traps, low-loss coils. Now, they are further im- If for making several types of radio receivers. Also proved all types will be supplied, wound directions are given for the proper care and use with enameled wire, accurately spaced on threaded, moulded plug-in-forms. S-M Coils of batteries, a chronological tabulation of impor- are the commercial uniform or a from now for only products enough today year single tant events in the history of the art, and, in the control receivers without And the five sizes tune from 30 stage compensation. chapter on transmission, a copy of the Interna- to 3000 meters with a .00035 condenser. a negligible field they can be Possessing tional Morse code with a list of conventional ab- effectively and efficiently shielded. See them at your dealers for all popular circuits. breviations, and the location of the various radio districts of the United is A PRICES States, given. good feature is the list of questions at the end of each A 30- 75 Meters. E 1400 - 3000 Meters Type" " Type $3.50 which to show the reader B 70- 210 . chapter quickly help " " $2.50 113 unwound Form 1.25 C 190- 550 . whether or not he has really understood what he " - " 515 Socket for all sizes 1.00 D 500 1500 . . $3 25 has just read. This is a second edition book, and in it has SENSITIVITY MEASUREMENT! been incorporated much new material that brings it up to date. In several cases the new material modifies the earlier conclusions. The Silver-Marshall Laboratories have perfected considerably a new and radical method of transformer measur- For example, the statement that audio frequency ing that insures an unbelievable degree of selec- amplification is used more extensively at present tivity and sensitivity to weak signals. All 210 than radio frequency amplification is now open wave and 211 tuned transformers long interstage to question, as the use of some form of radio are now measured by this remarkable system. frequency amplification is practically universal Price singly or in matched groups, $6.00 each. in commercial receivers. Likewise, soft tubes Specify for 199 or 201A type tubes. of the old type, requiring critical voltage adjust- For those experimenters desiring to avail them- ment, are no longer in general use, so that the selves of this special service, S-M transformers amount of space devoted to them in the first will be measured and matched at SOc. each. edition is now somewhat out of proportion to All other makes at $1. each, when returned ac- their importance. companied by remittance. It is perhaps unfortunate that the explanation given of the action of the three elec- See S-M Parts at your Dealer trode tube as a detector is so brief; a clear distinction between the detecting action and the repeating action of a tube is not easy to make to the beginner. Another thing that might well SILVER-MARSHALL Inc. have been included in the list of causes of how ling in audio-frequency amplifiers is acoustic feed- 846 W. Jackson Blvd., Chicago back, which is one of the commonest causes. There are also a few technical points on which the reviewer is in disagreement with the authors. The statement that when regeneration is carried not subscribe to Radio Broadcast? the or two Why By year only $4.00; years, $6.00, saving to the point of oscillation, signals will probably $2.40. Send direct to Doubleday, Page & Company, Garden City, New York. disappear, is not the case with ordinary tubes, though the quality of the signals will of course change. And the explanation of feedback coup- WHOLESALE EXCLUSIVELY ling due to tube capacity, given under the heading "Tuned Plate Regeneration," seems to indicate that the grid-filament and plate-filament capacities provide a coupling between circuits. 929 PENN AVENUE PITTSBURGH, PA. This is not so, and in other parts of the book where feedback through tube capacity is mentioned, the grid-plate capacity alone is specified, SATISFIED as the DEALERS quite properly, coupling capacity. BECAUSE The above points are of no importance to the general reader, and on the whole, the book is well WE HELP TJfES\~ written and its fund of useful information should make it a valuable addition to the radio library, is to not only of the beginner, but of the confirmed Catalog 466^3 free Dealers radio fan as well. WALTER VAN B. ROBERTS.

Tested and approved by RADIO BROADCAST RADIO BROADCAST ADVERTISER 177 A KEY TO RECENT RADIO ARTICLES OX-I01A UX-ioiA UX-isi MU-JO UX-zoiA UX-m By E. G. SHAULKHAUSER

You can

> Each periodicals. separate refei use should be cut out and pasted on cards for filing, any or pasted in a scrap book either alphabetically or numerically. An outline of the Dewey combina- Decimal System (employed here) appeared last in the May RADIO BROADCAST, and will be tion of tubes in an number. reprinted early in the same set with the

Ri 10. RADIO WAVES. RADIO WAVES. Radio News. March, 1926. pp. 1285 ff. H)R EVERY "Speech Currents in Radiophony," J. F. Bront. I he fundamental theory underlying the tiansmission of BALLASTING NEED radio waves .is given. Comparison is made between effects produced by pure induction at low and high frequencies, and radiation at various frequencies. At the high frequen- i ELKAY cies, a given amount of power at the transmitter will cause a greater disturbance at the receiver than at the low frequen- 'cies, says the writer. Diagiams illustrate the discussion.

R375- DETECTORS AND RECTIFIERS. ELIMINATORS, Radio News. March, 1926, pp. i2Qoff. B-Battery. "A B Eliminator from Matched Parts," George Ames. TUBE EQUALIZOR SYSTEM Construction of the Raytheon B eliminator, using Acme matched parts, is shown. Data is also given on the proper voltages for C battery, using various tubes on different plate voltages. A list of parts recommended, diagram, and photo- of Automatic Rheostats graph, give the necessary details.

R374. DETECTORS, CRYSTAL. CRYSTALS FOR 'T^HESE pre-adjusted cartridge rheostats (or Equalizers) deliver Radio News. March, 1926, pp. 1300 ff. DETECTORS. "The Crystal Classified and Analyzed," J. F. Corrigan. A. the correct amount of filament current to the tubes auto- A list of minerals which may be used for the purpose of rectifying high frequency currents, and giving the chemical matically. composition of each, is given. The crystals are classified in- to three groups, and each group discussed. The groups are: . . . control of volume without i. The elementary group of crystal rectifiers; 2. The sul- This system prevents overloading gives phide group; 3. The oxide group. distortion . . . eliminates several rheostat knobs . . . and makes the in-

R2OI-5. SHIELDING AND GROUNDING, SHIELDING. stallation of a filament meter unnecessary. QST. March, 1926, pp. 9-20. "The Problem," D. R. demons. Shielding retail for or It Complete shielding of coils is impossible because a shield The individual Equalizers but 50c. 75c. with mount. must then have zero resistance and an infinite states area, is cheaper to use them than rheostats. They take up less room, and, the writer. The degree of shielding depends upon the frequency, better results being obtained at higher frequencies, being on the base-board, they shorten the leads and make a neater since current sheets are limited to a very small depth of the be used in set so shield, and great thicknesses are not required. looking job. And any combination of tubes may a Experiments conducted with unshielded coils showed the Write for Equalizer folder. effect of increase in effective resistance when brought near equipped. complete System to a condenser. The method of measuring the high frequency resistance of coils is clearly indicated and described. The resistance increase varies considerably with change in JOBBERS, DEALERS MANUFACTURERS frequency. Placing the coil at least two inches from the condenser will result in practically no effect on the coil con- Look Well to Your Next Set Save lOc. to 20c. on Each Set stants. Shields placed near coils, or connected directly to one end of the coil, increase the effective resistance to nearly The modern radio set has this automatic The Elkay Tube Equalizer System en- 500 per cent., at the same time decreasing the inductance. filament control. Before getting behind ables you to omit several adjustments, Coils surrounded showed various completely by shielding set next season, look into this thor- needless wire, and an filament changes in constants, depending on the size of the coil and any expensive the shielding box. Curves presented, indicate the changes. oughly. Already a number of well known meter. Our low quantity prices will be Several circuit diagrams are one a tester presented, showing sets are Elkay equipped. We shall be sent you gladly ; also a sample set ofEqual- for the shield material. glad to give you the names of these. izers if you are a bona fide manufacturer. R4OO. DUPLEX AND MULTIPLEX SYSTEMS. MULTIPLEX QST. March, 1926, pp. 21-23. RECEPTION "Multiplex Short-Wave Reception." J. K. Clapp. THE LANGBEIN-KAUFMAN RADIO CO. A scheme whereby several receivers may be operated simultaneously from the same antenna, is shown. With this 511 New Conn. arrangement, an operator may listen to several wave bands Dept. R, Chapel St., Haven, at the same time, making observations relative to wave band best suited to traffic under varying weather conditions, day or night. He may also be able to check wavemeters using fundamental and harmonic notes at the time =l TUNERS that wwv sends out the standard frequency signals.

R342.5. POWER AMPLIFIER (TRANSMITTER). AMPLIFIER, QST. March, 1926, pp. 29-30. Power. "A Power Amplifier for the Low -Powered Transmitter," Now is the time to subscribe for RADIO BROADCAST R. P. Turner. Through your dealer or direct, by the year only $4.00 A power amplifier to be used in conjunction with a master oscillator on high frequency telegraph transmitters, is de- DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK scribed. It is said to be very effective in steadying the output frequency, and to add materially to better reception at the receiving end. This amplifier acts similarly to a r. f. amplifier in receivers. Circuit diagrams and constructional details are given. BAKELITE for Radio Parts R6i2. SHORT-WAVE STATIONS. NORTH POLE The use of Bakelite in the set QST. March, 1926, pp. 33-36. RADIO STATION. parts you "Amateur Radio to the North Pole Again," F. H. Schnell. buy or build, will insure you against in- A complete description of the apparatus used on the Detroit Arctic Expedition, is given. The receiver and ferior reception through defective insul- transmitter and both sets are en- employ C-JOI-A tubes, ation. Write for 29. closed in aluminum boxes. The transmitter operates on booklet two frequencies, 3750 and 7500 kc. (70 and 40 meters). The receiver covers ranges from 23,076 to 2776 kc. (13 to 108 meters). The whole outfit, including a 3o-foot bamboo pole, weighs only 45.5 Ibs.

R53I.2. STATION CALL LETTERS. CALL LETTERS. RADIO BROADCAST. April, 1926, p 708. "Short-Wave Stations of the World." BAKELITE CORPORATION A complete list of more than a hundred short-wave sta- 247 Park Ave., New York, N. Y. Chicago Office: 636 W. 22nd St. tions situated throughout the world is printed, including BAKELITE CORP. OF CANADA, LTD., 163 Dufferin Street, Toronto, Ontario, Canada call letter, location, frequency, and wavelength.

Tested and approved by RADIO BROADCAST 178 RADIO BROADCAST ADVERTISER

R230. INDUCTANCE MEASUREMENT. INDUCTANCE OF QST. March, 1926, I>D. 39-41. FILTER CHOKE. "Finding the Inductance of the Filter Choke," E. W. Berry. A method of determining the inductance of choke coils used in filter svstems after resistance and impedance have been obtained, is descrfbed. With the aid of the curve chart, the inductance is read off directly. The method of measuring the values needed, and sample calculations, clearly show the procedure used.

Rno.. RADIO WAVES.. RADIO WAVES. Popular Radio. March, 1926, pp. 207-212. "A New Theory of Wave Transmission," E. F. W. Alexanderson. The writer enters into a discussion on the relation between the electron, the ether, and magnetfsm, and proceeds to The supreme achievement show that all the theories of radio waves heretofore of 38 pro- years* experience pounded fail to explain certain radio phenomena. In the course of his researches into the mysteries of radio waves, the author developed a new theory which explains many of the old observations as characteristic behaviors of the Else horizontally polarized wave. This new theory, which ac- Nothing counts for fading and the erroneous results met with in direction finding, is studied with the aid of a mechanical Like It! model, as the several illustrations show.

ROTJ. TRAINING OF OPERATORS. TRAINING is a simple radio con- Popular Radio. March, 1926, pp. 213-219. OPERATORS. HEREtrol the Centralab Modu- "Radio as a Life Work." P. Boucheron. lator Plugthat is even The opportunities of the trairied radio man in this new unique in a field field of science and industry are outlined by the writer. where phenomenal Engineers are needed at high-powered transmitting stations developments are common. used in transoceanic work, 'i) as operators and supervisors of ship and other land stations, (2) as engineers for broad- Provides smooth, noiseless control of casting stations, and (3) for purposes of developing the new tone and volume direct at the plug science. The for the trained men with the set operating at full efficien- _ Model RS-1 opportunities properly $55. Beau- are great in all branches of radio, says the writer. cy. Without adjusting tuning dials Hei>htl57-Kin. or other tiful Mahopany finished cab- controls, you can regulate inet, oxidized silver grille. AmpHonsare R23O. INDUCTANCE. INDUCTANCE- volume from a whisper to maximum equipped with cords and panel plugs. Popular Radio. March, 1926, pp. 255-257. simply by turning the little knob on "A Measurement Chart," R. j. Hoffman. this plug. Clarifies tone. Replaces oA 'Revelation in A chart is presented making the construction of toroidal the ordinary loud-speaker plug. coils a matter of simple calculations. The inductance equation is given, and a sample calculation worked out. $2.50 at your dealer's, or mailed Faithful 'Reproduction direct on receipt of price louder, more sensitive R24O. RESISTANCE; DECREMENT; RESISTANCE, PHASE DIFFERENCE. R. F, of Condenser. CLEARER,and more realistic in tone, actual by Phil. Mae,. (London). Feb. 1926, pp. 428-432. CENTRAL RADIO LABORATORIES comparison.than anyother existingtype "Measurement of the Resistance of a Condenser at Radio * 22 Keefe Ave. D. ofradioreproducer.thisnewestaddition Frequency," Chas. Callis. ^^ Milwaukee, Wisconsin An attempt is made at the absolute measurement of resis- to the Amplion family the beautiful tance of a variable condenser at a frequency of one million of variable resistances Radiolux- Manufacturers Amplkm is, in every sense, second. The method of the r. f. re- cycles per measuring for all radio circuits a revelation.1 Outwardly resembling sistance of a circuit is described. Since the high frequency resistance of a coil alone cannot be measured, as stated, a the distinctive English bracket clock, in- method was employed whereby two like coils were used in wardly it is a radical, complete depar- the circuit simultaneously, placed in such relation to each ture in acoustic design. Price $55. other that their combined resistance was equal to the re- in the circuit. Hear the six sistance of one The equation evolved, and Gen it, and other popular the curve obtained, are presented. Sources of slight error, models of $12 to $42.50. Amplions, and effect of different coil forms, are considered. LATEST "COAST TO COAST" FUILY GUARANTEED Write for "Amplion Pedigree." THE AMPLION CORPORATION Ri 13. TRANSMISSION PHENOMENA. TRANSMISSION 5*" Poys. Review, Feb. 1926, pp. 189-215. PHENOMENA. RADIO**SAVE'/JTD'A OF AMERICA "The Propagation of Radio Waves Over the Earth," Uaera everywhere report Miraco Radii _ on A. H. and E. O. Hulburt. programs coast to coast loud speaker; Suite L. 280 Madison Ave.,NewYork City Taylor outperform Beta three timea aa costly. of hear countries. Radio a Chicago Branch: 27-29 No. Morgan St. Larmor's theory refraction due to the electrons of the Many foreign does most amazing values in unconditionally Amplion Corporation ofCanada, Ltd. Toronto Kennelly-Heaviside layer, not explain the "skip- guaranteed, factory-built long distance Alfred Graham&Co., London, Eny., Patentees distances" for short waves. The range as a function of sets let testimony of users convinceyou. wavelength shows a minimum for about 200 meters, which . PowerfutNewMulti- Itube Miraco gets suggests the introduction of a critical frequency term. If I long distance on scsssiiaBiw the effect of the magnetic field of the earth on the motion I loud speaker. Set, I ONLY . of the electron is taken into the modification of RADIO account, the I COCCI Literature on latest Larmor theory necessary to fit it to the facts rnCC. improved 1 to 6 tube mod- RADIO FANS, a to Radio experimental GETS'EM one-year's subscription Broadcast will cost I els, new low prices, testimony of four is secured. A quantitative theory is here developed. The you dollars, two years six dollars. Consider this expenditure COAST *> | users and SPECIAL OFFER. Write: aa a investment is assumed to contain N free electrons being necessary on your part for the future develop- upper atmosphere RADIO CORP'N ment of own of Radio. and is COAST MIDWEST your knowledge per cc., neglecting absorption, the dispersion worked Pioneer Builders of Seta out for various modes ot polarization of the radio waves. 4O6-W E.Sth St. Cincinnati.O. Then the skip distances are computed, making various as- sumptions as to the electron density distribution. Com- parison with the experimental skip distances shows good agreement, and indicates that the radio waves which just reach the edge of the zone beyond are refracted around a curved path, reaching in the daytime a maximum height of from 97 to 149 miles. At this height, the electron density FROST-RADIO B comes out close to IO electrons per cc. At night, the electron density gradient is less, and the height is greater. is the new fHOST-RADIO These conclusionsagree with physical conceptions from other Here evidence. From the dispersion equation a value for waves of 60 to Metal Frame 200 meters is obtained, which indicates total reflection from the electron layers at all angles of incidence. From this 50C result, combined with interference between various modes of Rheostat polarization of the radio rays, a detailed qualitative explanation of many fading phenomena is presented. Notonlynew Further conclusions obtained are that the ions in the at- and radical- have little effect in wth the mosphere comparison electrons; ly different, that for waves, the Larmor is that longer theory correct; infin- short waves are propagated long distances by refraction in but the upper atmosphere and reflection at the surface of the itely bet- not bound earth, by earth waves; that waves below 14 meter! Sturdy ters (21,426 kc.) cannot be efficiently used for long distance one transmission. nickelpiece Rooo. HISTORY. HISTORY. RADIO plated BROADCAST. April, 1926, pp. 643-646. frame in- REPRODUCING UNIT "How Radio Grew Up," R. H. Marriott. The writer traces the history of radio from the time of sures pre- M liny Receiving Set Manufacturers who supply Loomis in 1872 to the year 1897, when Marconi interested a cision oper- built-in speakers are now using this high grade group of Englishmen in his radio devices. This period in- ation and smooth, lustration cludes the of unit. experiments Hughes, Dolbear, Hertz, Branly, non-wearing action is actual size Lodge, Tes|a, Popoff and others. Following Marconi's frame cannot warp or bend, shaft alignment is perma- QUALITY AT A PRICE early work in radio, the public soon became aware of the nent. Bakelite pointer knob; tinned soldering lugs; 2, with a factory buck of it able to take care of any importance of this means of communication. 4, 6, 10, 15, 20, 25, 30 and 35 ohm types 50c. 20O quantity required is what Holtzer-Cabot has to 400 ohm potentiometer, 65c, A remarkable achieve- offer you. R386. FILTERS. WAVE ment. Ask your dealer about the new HOST-RADIO RADIO BROADCASTST. 686-688. TRAPS. f SPECIFIED DELIVERIES ASSURED April, 1926, pp. Bakelite Rheostat. "Cutting Out the Locals," H. E. Rhodes. Manufacturers write for full particulars A simple outline on the subject of interference elimination THE HOLTZER-CABOT CO. by means of tuned filter circuits, commonly known as wave- HERBERT H. FROST, Inc. * is of the traps, presented. The theory wave trap, just how 314-324 Manufacturers of signal apparatus for fifty years WEST SUPERIOR ST., CHICAGO, ILL. ana why it operates in eliminating or reducing interference, 125 New York City Cleveland Kansas City Amory St. 6161-65 S. State St. and data presented to explain the results obtained, are in- BOH ton, Mans. Chicago, Illinois cluded in this article. The radio-frequency amplifier is Los Angeles considered an effective wave trap when properly built. RADIO BROADCAST ADVERTISER 179

RIJI. ELECTRON TUBE CHARACTERISTIC VACUUM CURVES; GENERAL PROPERTIES. TUBES. RADIO BROADCAST. April, 1926, pp. 658-663. "The Tube and Its Best Uses," K. Henney. The general theory and operation of vacuum tubes as detectors and amplifiers, is discussed. The testing and the practical operation of tubes is obtained by inserting proper resistances in the input and output circuit, as shown. The importance of static and dynamic curves is explained. The relative merits of transformer, impedance, resistance, push- pull and parallel operation of tubes, is considered. Loud speakers should be coupled to a circuit of proper impedance, * either direct to the tube or through an impedance or transformer, in order to obtain true reproduction of signals. [Jiscussion on the use of high-mu tubes, and facts concerning tube rejuvenation, are presented.

R 544.4. SHORT-WAVE TRANSMITTING TRANSMITTER, SETS. Sbort-Wave. RADIO BROADCAST. April, 1926, pp. 678-681. "How a Portable B Battery Transmitter Works," RADIO BROADCAST Laboratory. The results obtained with the short-wave transmitter used at 2 GV employing dry B battery supply and small input power, is outlined. Ordinary receiving tubes of various makes were used in the portable set, which employed the simple Hartley circuit. The details of construction, and records of transmission, are described. Rii3. TRANSMISSION PHENOMENA. TELEPHONE RADIO TRANSMISSION BRACH Proc. I. R. E. Feb. 1926, pp. 7-56. PHENOMENA. "Transatlantic Radio Telephone Transmission," L. Espenschied, C. N. Anderson, and A. Bailey. The paper reports upon measurements of radio trans- LIGHTNING ARRESTERS mission which have been made during the past two years in a study of the possibilities of transatlantic telephony. These measurements cover several different frequencies in Now with Them the range below 60 kilocycles transmitted in both directions Carry across the Atlantic, and represent probably the most com- prehensive study yet made of any transmission path. An earlier paper described the special high power radio telephone system and the measurement methods employed in the tests, and gave certain preliminary measurement results. The re- $100 INSURANCE lation which exists between diurnal and seasonal variations of signal field, and the exposure of the transmission path to sunlight, is shown. The conformity of the measured results Against Damage to Any Standard Radio Set to the values determined by formulas, is indicated. Inter- esting correlation is shown between abnormal radio transmission and magnetic storms. The high efficiency of Brach Lightning Arresters enables The diurnal and seasonal characteristics of noise are shown to be generally similar to those of signal strength, and us to attach to every Brach Arrester a $100 guaranty indicate the noise to be of tropical origin. The average frequency distribution of static is shown for various re- against damage by lightning. This insurance covers ceiving stations. Signal to noise ratios are shown for both England and the United States for transmission on so-odd electrical parts in radio sets of standard makes. kilocycles, together with the improvement afforded by a directional receiving system of the wave-antenna type. Only Brach Arresters Give Rail- ATMOSPHERIC Ri 14. STRAYS (ATMOSPHERICS). Protection to Radio Proc. /. R, E. Feb. 1926. pp. 133-158. DISTURBANCES. way Signal "The Present Status of Radio Atmospheric Disturb- ances," L. W. Austin. We that all our arresters contain the same ele- The paper gives a resume of our present knowledge con- guarantee cerning atmospheric disturbances. In Europe it is found ments of Silicon or Vacuum that about 50 per cent, of these are due to thunderstorms, protection- -namely Carbide, while a considerably greater percentage are associated with which have been furnished the Brach for rain areas of some kind. !n the United States, near the by Company Atlantic Coast, disturbances in general come from the over 20 to and are southwest, while on the coast of California they come from years protect Railway Signal Systems; the permanent centers in the neighboring mountains. In free from of dis- the Middle West the direction is variable, depending on danger becoming grounded through thunderstorms, rain areas, etc. In England, cathode-ray and at the same time are sensitive to oscillograms have been taken of the atmospherics. The charges highly main disturbance is of audio frequency and usually induction. aperiodic. Some of the curves show high-frequency ripples lightning on the main waves. These may be real sources of atmos- troubles. pheric This is why Brach Arresters are Different! R43i. STRAYS (STATIC ELIMINATORS). McCAA ANTI-

Radio. March 1 1 ff. STATIC DEVICE. " 1926, pp. Refinements in the McCaa Anti-Static Devices," E. B. Patterson. L. S. BRACH MFG. CO. A detailed account of the operation of the McCaa static eliminator, is given. The theory of its operation, and the advantages derived from its use, are outlined. Construc- Newark, N. J. tional details are also presented, which the experimenter can follow in building one of these interference eliminators for Devices over his receiver. Circuit diagrams are explicit and complete. Makers of Electrical Protective for

R8oo (621.314.3). TRANSFORMERS. TRANSFORMERS, 20 years Radio. March 1926, 23-26. Design Data. " pp. Design of Small Power Transformers and Filter Induc- tances," J. B. Dow. Specifications, data, and formulas, for the construction of transformers and choke coils for use in B battery eliminators subscribe to Broadcast? the and amateur transmitters, are given. Typical examples Why not Radio By year illustration. A full- accompany the equations for purpose of direct page table gives design data for inductance coils with iron only $4.00; or two years, $6.00, saving $2.40. Send to cores, from 0.05-10 o.^o-ampere carrying capacity. A table giving measurements of copper wire and turns per square Doubleday, Page & Company, Garden City, New York. inch is included.

R344.4- SHORT-WAVE GENERATORS. TRANSMITTER, Radio. March, 1926, pp. 29 ff. Skort-Waut. "A Baby Radio Transmitter," W. H. Hoffman. The construction of a compact 75OO-kc. (4O-mcter) transmitter tube and cells for Radio using a uv-ipg dry power supply is, Battery Chargers outlined. The circuit employed is the modified Colpitts. The particular circuit arrangement was developed by the Best by Test Burgess Laboratories. The antenna system is adjusted to resonance by means of a flashlight lamp and battery, or a hot wire instrument. A |oop may also be used for the 50 7500 kc. (4O-meter) band, it having a single turn three feet minus bulb -on a side, a three-plate variable condenser and a three-inch coupling coil being in series. east of Rockies ANTENNAS. R32O. ANTENNAS. Your dealer can get it for you Kaaw.Radio. March, 1926.1920. pp. ^5-30._35~36. "Using the Right Transmitting Antenna," F. C. Jones. Several types of short-wave transmitting antennas are THE ACME ELECTRIC & MFG. CO. discussed, and their method of operation outlined. The type of antenna to use depends upon the surroundings and 1410 Hamilton Avenue Cleveland, O. local conditions, according to the writer. Photographs and diagrams of several types, are presented.

Tested and approved by RADIO BROADCAST 180 RADIO BROADCAST ADVERTISER

Rii3. TRANSMISSION PHENOMENA. BROADCAST Proc. I. R. E. Feb. 1926, pp. 57-131. TRANSMISSION PHENOMENA. "Some Studies in Radio Broadcast Transmission," R. Sown, D. K. Martin, and R. K. Potter. The paper is based on radio transmission tests from station 2 XB, in New York City, to two outlying field stations. It i? a detailed study of fading and distortion of radio signals under night-time conditions in a particular region, which may or may not be typical. Night-time fading tests, using constant signal frequencies and bands of frequencies in which the receiving observations were recorded by oscillo- show that is selective. selective is graph, fading By fading Product of nearly Ak 40 years' Experience meant that different frequencies do not fade together. From the regularity of the frequency relation between the frequencies which fade together, it is concluded that the selective fading is caused by wave interference. The signals appear to reach the receiving point by at least two paths of different lengths. The paths change slowly with reference to each other, so that at different times the component waves add or neutralize, going through these conditions progres- sively. The two major paths by which the interfering waves travel are calculated to have a difference in length of the order of 135 kilometers for the conditions of the tests. Since this difference is greater than the distance directly BD-1B includes !he NATIONAL Equicycle (straight from the transmitter to receiver, it is assumed that one path line wave length) Condenser and the genuine BROWN- at least must follow a circuitous ING-DRAKE Inductance Coil with the new Type B route, probably reaching Various the- Dial. Price $925. upward through higher atmospheric regions. ories to explain this are briefly reviewed. The territory The New about one of the receiving test stations in Connecticut, is Clear, natural tone, broad musical range and NATIONAL Tuning Units found, under daytime conditions, to be the seat of a gigantic supreme sensitivity distinguish the Am- fixed wave interference or diffraction pattern, caused in part plion from other loud speakers. Your set will Comprising the genuine by the shadowing of a group of high buildings in New York perform only as well as the loud speaker BROWNING-DRAKE City. The influence of this pattern on night time fading is will reproduce. Your good set deserves the SPACE WOUND discussed. It is considered a contributing but not the con- best loud speaker you can buy. Try an TRANSFORMER trolling factor. Tests using transmission from an ordinary- Amplion for an evening or two. You will and the type of broadcasting transmitter show that such trans- bear your set at its best with an Amplion. mitters have a dynamic frequency instability, or frequency NATIONAL Velvet Vernier Dials and Condensers modulation, combined with the amplitude modulation. At THE AMPLION CORPORATION the wave interference effects which selective Are now in the hands of your dealer. Their beauty and night, produce OF AMERICA fading, result in distortion of the signals when frequency efficiency will greatly surprise you. See them at your Suite L, 280 Madison Avenue, New York modulation is It is shown that the dealer's. Send for Bulletin 105 R. B. present. stabilizing Chicago Branch: 27-29 North Morgan St. transmitter frequency eliminates this distortion. A theory Amplion Corporation of Canada, Ltd, Toronto NATIONAL COMPANY, Inc. explaining the action is given. The distortions predicted by W. A. READY, President Cambridge, Mass. the theory check with the actual distortions observed.

i discussion of carrier BD-2B includes the NATIONAL Equicycle straight A ordinary modulated transmission, line wave length) Condenser and the genuine BROWN- carrier suppression, and single side band transmission in ING-DRAKE Transformer with the new Type B Dial. relation to selective fading is given. It is shown that the Price 312.75. use of a carrier suppression system should reduce fading.

R376-3. LOUD-SPEAKING REPRODUCERS. LOUD SPEAKER Kadio. March, 1926, pp. 32. CONSTRUCTION. "Construction of a Simple Cone Type Speaker," E. C. Nichols. The constructional details of a simple and effective loud speaker of the cone type, is given. The horn is made of paper, which is mounted in a chamois supporting ring and energized through contact with the of a regular diaphragm Send now for this valuable loud speaker unit. The whole arrangement is then mounted HOOK-UPS. FREE book. Full of advanced on a wooden frame. The method of adjusting the speaker hook-ups, parts and kits. for best results, is given. A real guide. Shows factory built seta and the new R344-3. TRANSMITTING SETS. TRANSMITTER, ideas in radio. Send at Radio. March, 1926, pp. 37-39. ^o-Wat\, 6 XAO once. No charge. No "The 5O-watt Transmitter at 6 XAO," G. M. Best. obligation. Please in- Constructional details of station 6 XAO'S 5O-watt trans- clude name of radio fan. mitter, operating on the high frequency band of 3750 to 30,000 kc. (80-10 meters), are given. The set is built in three parts, the aerial tuning circuit panel, the transmitting panel proper, and the power unit panel. The circuit diagram and arrangement of parts, including a list of material required, are presented. 1O2-1O9 S. Canal St., Chicago R35i. SIMPLE OSCILLATORS. OSCILLATORS, Radio. March, 1925, pp. 39 ff. Short-Waxc. RADIO FANS, a one-year's subscription to Radio Broadcast "Parallel Wire Snort-Wave Oscillators," F. C. Jones. will cost you four dollars, two years six dollars. Consider thit Experimental results on frequencies below 60,000 kc. expenditure as being a necessary investment on your part for (5 meters) using vacuum tube oscillators in standard cir- the future development of your own knowledge of Radio. cuits, are outlined by the writer. Several types of oscillators, including amplifiers for use in connection with oscilla- T/lil it a good lime to subscrike for tors, are used on waves of 75 cm. length although they are RADIO said to operate on waves still shorter. For work on the BROADCAST 75 cm. band, a parabolic reflector is shown and described. dealer or the . Through your direct, by year only $4.00 Rii3.5- METEOROLOGICAL PHENOMENA. WEATHER AND DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK Radio News. March, 1926, pp. 1256 ff. RADIO. "Radio Forecasting," E. B. Rideout. In the writer's opinion, the two most important things FOR "B" POWER that enter into the influence of weather on reception are CLEAR, QUIET temperature and barometric pressure variations. The crea- tion of electrical discharges, through mixture of hot and cold air, setting up static waves, together with developments of large storm areas, account for much of pur poor reception due to fading and atmospherics. Typical results, based upon actual observations, are related.

Ri3i. ELECTRON TUBES; GENERAL ELECTRON TUBES. PROPERTIES. Radio News. March, 1926, pp. 1255 ff . "What Happens in Vacuum Tubes," Dr. A. Katsch. Although theoretical formulas have been developed covering the actions taking place within vacuum tubes, such for- RADIO mulas contain many generalizations, and it is necessary to depend to a great extent upon actual research and experi- "B" mental work in order to determine what goes on within the Storage declares the writer. of Battery tubes, Photographs are shown the 2vci"J Lasts Indefinitely Pays for Itself discharge glow of electrons in a partial vacuum. RADIO PEP Economy and performan 'd of before. Recharged a ..-.,-- IT and Clble cost. that la clear, pure quiet. R8oo (533.85) VACUUM APPARATUS. VACUUM PUMPS. B-BATTERY ELIMINATOR an I lint.-rl UH Standard leading Ka-iioHa. i.. AuthoritiAuthorities, includ- Approved by J - Inff Radio Sci. Int. Standards, ".adioR; News Radio NttDS. 1282 ff. Pop- Laboratories. Pop. f March, 1926, pp Stops A.LL the hum by using EIGHT perfected elec- 1*1) Lefax, Inc.. and other Important Institutions. Equ.lipped with "How Radio Tubes Are Dr. C. B. Bazzoni. Solia Rubber COM. an insurance_ a(clnst_ acid and leaka:ae. Extra Evacuated," trolytic cells and NO TUBES. - - heavy jars, rieavy n plates. Order yours today! Methods of producing vacua are described. Simple and Plugged into the standard A. C. house lighting cir- effective are shown which be used the ex- a day order pumps may by cuit RADIO PEP gives silent, strong, dependable in his own tubes. Various icelved. Extra Offer: 4 batteries In eeriea (96 volts), *]u :,n. Pay perimenter evacuating types plate current that improves the performance of your after discount ror cash examining batteries. 6 . xp'canman percent of pumps are classified as follows: i Water or steam injector due to the effect of its condensers. with order. Mail your order now! set. huge WORLD BATTERY COMPANY air pumps; 2. Ordinary piston air pumps; 3. Oil-sealed pis- No more batteries to buy! ton air of the 4. Oil-sealed are for the modern 1219 So. Wabash Ave., 78 pumps Geryk pattern; rotary 135 VOLTS called by seta and Dept. air of the Trimount Makers of I fie famous World Kndto "A" Storage pumps pattern; 5. Stationary mercury tubes. RADIO PEP delivers 1 33 volts year after year FrkcK 0-volt, lOOAmv. tlt.25: ISO Amp. tlSM: 140.Amp. air pumps, of the Sprengel pattern; 6. Rotary mercury air without Ml cmiiwed wit* Solid ttubber due. weakening. pumps of the Gaede pattern; 7. Mercury jet diffusion air Money-back guarantee. Price $38.00. of the 8. mole- pumps, Langmuir pattern; Rotary cylinder Write for Circular! cular of the Hoiweek The of pumps pattern. principles of these is described. Particular details of Wo 1*1 d operation types PEP MFG. CO., Inc. the Guichard of are The TORAGE BATTERIES simple type Sprengel pump given. 33 West 42nd Street New York writer states that vacua of the highest degree be ob- * * may KHJ KGO> KFAFx_WJY3T2ffl tained with these of simple types pumps.

Tested and approved by RADIO BROADCAST RADIO BROADCAST ADVERTISER 181

Weather Forecast Trans- missions by Radio For Permanent Satisfaction following stations in the Illinois section THEsend out regular weather forecasts and re- radio. With the of and ports by exception NAJ COUNTERPHASE SIX in Amateurs WGO, all reports are telephony. who receive any of these transmissions are re- quested to write to the Weather Bureau Office, Springfield, Illinois, and report on the quality and service, and say how distinctly the stations are received.

NAJ, Great Lakes . . ijikc. 1988 meters 9.45 A. M. Morning Lake Forecasts. 4.00 p. M. Storm Warnings. 10.00 P. M. Evening Lake Forecasts.

woo, Chicago . . . 337 kc. 890 meters

i i.oo A. M. Local and Lake Forecasts. 4.00 P. M. Local and Lake Forecasts. 9.00 p. M. Evening Local and Lake Fore- casts.

. . . kc. meters WLS, Chicago 870 344.6 receiver 9.00 A. M. Morning Forecasts, Special Factory-built $165.00 Warnings. 12. 10 p. M. Same as 9 A. M. Primarily a radio receiver rather than Corn and Wheat Sum- Region merely a piece of furniture, its per- mary Wednesday. formance never fails to enlist the user 12.00 NOON Aviation Forecasts Except Sun- day. in the ranks of B-T Boosters.

KYW, Chicago . . . 560 kc. 535.4 meters 12.00 NOON| Morning Forecasts. Thousands of testimonial letters sup- 4.15 p. M.f Special Warnings. port our belief that the COUNTER- 10.00 p. M.f Except Monday Evening PHASE SIX is a wonderful Forecasts. truly receiver. It's built for sat- WAAF, Chicago . . 1080 kc. 278 meters permanent 10.30 A. M. Morning Forecasts. Weather- isfaction. Crop Summaries on Wednesday During Crop Season. See one at your dealers. P. M. and 12.30 Repeated; Saturday gives with the Weekly Forecast. Enjoy summer reception Except Sunday and Important COUNTERPHASE SIX. Holidays. WHT, Chicago . . . 1260 kc. 238 meters COMING New B-T 11.30 A. M.f Morning Forecasts. Corn and Offerings * Wheat Region Summary Wednesday. B Battery eliminators complete. 12.00 MIDN'T Forecasts. Evening Except eliminator Sunday. B Battery parts. WJBC, La Salle . . . 1280 kc. 234 meters Sockets New Push 12.30 p. M. Morning Forecast. Except Sun- type. k day. Non-Microphonic type woe, Davenport . . 620 kc. 483.6 meters 12.45 p. M. and 2.00 p. M. Except Saturday (i.oo p. M.) and Sunday. Circulars ready for distribution June 1st Morning Forecasts, General Weather Conditions. Weather- Crop Summaries on Wednes- BREMER-TULLY MFG. CO. day. Q.OO P. M. (Soon After) Except Sunday 532 So. Canal St. 111. (9.45 p. M.) and Monday. Chicago, Evening Forecasts; Special Cold Wave Warnings Sent as Flashes. Why not subscribe to Radio Broadcast? By the year only $4.00; or two years $6.00, saving

WEW, St. Louis. . . I2iokc. 248 meters $2.40. Send direct to Doubleday, Page & Company, Garden City, New York. 10.00 A. M. Morning Forecasts, General Weather Conditions. 5.00 p. M. Special Warnings. Except Sun- day. New Vitalitone Cone KSD, St. Louis . . . 550 kc. 545.1 meters Speaker 10.40 A. M. Morning Forecasts, General LIBERTY MODEL Weather Conditions, River Two cones 19" and 8" diameter high and low Stages. pitched. Free edge, full floating resona' 12.40 P. M. Special Warnings undamped tor, finished. tone 1.40 P. M. Repeated. beautifully Superior quality. Packed so no is 3.00 P. M. Repeated. breakage possible. 10.00 P. M. Evening Forecasts. Free from patent litigation. ~^- Except Sunday. , Powerful unit of large dimensions KMOX, St. Louis . . 1070 kc. 280.2 meters We are Pioneers Cones since 1918 10.00 p. M. Evening Forecasts. Except Sun- day. Mfd. and Guaranteed by " List fOne hour earlier during Chicago Daylight $10 VITALIS, HIMMER, N.Y., N.Y. Saving."

Tested and approved by RADIO BROADCAST 182 RADIO BROADCAST ADVERTISER

A of the Neglected Angle ACCUSTI-CONE Radiation Question By HAROLD JOLLIFFE SPEAKER*

RADIO receiver which is allowed to go PTROMFHCTORYTOYOV into a state of oscillation while a station Full floating 19 inch cone A is being tuned-in, is the cause of the most worth in a powerful unit, $25 store; potent and destructive of all forms of interference save by getting it directI fromIIUSIJ man-111CU1- experienced on the broadcast band of frequencies. ufacturer for only Better One can, as a rule, get away from the perni- cious roll and crackle of a severe static storm by Superior to any the of the local sta- f.50' Summer tuning-in powerful signals Speaker, at any price tions; and if any interference created by two MONEY HACK IF WE DO NOT PUOVE IT ON YOU II SET stations heterodyning each other is manifest, Reception one may always seek another station which Reproduces all high and low tones, with comes in at a point on the dial where this inter- true and natural. ference is not present. Beautiful cone, dust proof wall ELECTRAD But there is positively no surcease from the ' Lamp unit. Packed to go anywhere. demoralizing shrieks and squeals of an impro- Socket Antenna Remember you have a free trial. perly operated regenerative or oscillating radio all risk. don't. set. The warn- We take the You Just screw this simple, electrically cer- frequency attention-compelling of the fire is as soft music Fully guaranteed. tified device into any lamp socket in the ing engine compared to the siren-like whistles and house, and you will minimize annoyance shrill, groan-like Accusti-Gone crescendos frequently issuing from the loud * from squeals, howls and "canary birds." speaker. And, somehow or other, these destruc- Laboratories Brings in what you want volume, dis- tive agents always seem to have the knack of 96 New N. Y. tance, clarity. And ends lightning Church Street, York, on the scene at the critical moment worries. arriving just when the zealous soprano has reached high C, Consumes no current, Absolutely safe. or when the violinist is applying his best efforts certified At Tested and electrically. to the last few notes of his number. most radio stores, price, 75c. in good Many interesting articles have appeared from $1.10. JL Canada, time to time in the various journals devoted to radio, showing how unnecessary interference created an receiver be avoided by oscillating may Sets Parts Kits by^the proper handling of the controls when a Radio's Newest station is there is no doubt being tuned-in; and You need thii big FREE book. ELECTRAD A practical guide to success in that if these instructions were followed 1 ' carefully let building. Gives advanced Shows all newett by all, the ether would not be the bedlam that hook-ups. New York City parts and kits, built up set* it sometimes is. Other writers of constructional ready for use, battery eliminators, radio's newest creations. articles have gone a step further by pointing out Write for IVipy free, also lend name of radio fan. Send to-day. the desirability of so building a set that a transfer Thorola Receivers of energy from the oscillating circuit to the antenna is prevented. As an example of this, we * 103-109 S. Canal St. .Chicago and Speakers have the well-known Teledyne and Browning- Drake receivers, both these sets being equipped RADIO FANS, a one-year's subscription to Radio Broadcast with a single stage of non-oscillating radio- Must will cost you four dollars, two years six dollars. Consider thi* Outperform allows the de- frequency amplification. This expenditure as being a necessary investment on your part for Reichmann Company, 1725-39 W. 74th St., Chicago tector to be set into oscillation whenever desired, the future development of your own knowledge of Radio. but at the same time isolates these oscillations in the detector circuit so that they cannot be radiated from the antenna. Hence, both these receivers, and others designed along similar Voltmeter lines, are generally referred to as non-radiating, "Tip-In" which they are according to the present definition of the word. Then there is a comparatively recent development, a "capacity-bridge" arrangement, designed as a unit by itself, the purpose of which is also to eliminate radiation from the antenna

when it is connected between the antenna and the oscillating receiver. This method of preventing unnecessary interference is somewhat different from the one mentioned in the foregoing JVoiseless- paragraph and probably more efficient. But the main point to remember is that both prevent foll radio power radiation from the antenna. Note that 1 have the word "antenna." The reason for A new HOYT instrument, in a beautiful bronze- stressed from the with a finish case, equipped unique swiveling ar- this will become apparent in just a moment. rangement on the tips. This permits the meter to in be inclined at any angle between the vertical and Now, it is obvious that the theory involved which best harmonizes with the with horizontal, appear- both the above blocking arrangements is that so socket ance of the set and which allows the most easy light as oscillations are from reading. long prohibited reaching For instant attachment to the Radiolas Nos. ao, the antenna but are confined to the receiver it- 15 and 18, the Victor and Brunswick sets, and all 'BalkiteST&Balkite radiation is and there- other Radio sets equipped with tip-jacks in the self, entirely eliminated, filament circuit. fore no interference is caused to listeners in the Marked in red at \ volts, above which point dry- From it at its face Battery cell tubes must not be operated if maximum recep- neighborhood. this, taking Charger tion and life of tubes is desired. value, it would seem that the antenna with the FANSTEBL PRODUCTS CO., Inc. Send "HOTT Meters Radio." for catalogue for of course constitutes the North Illinois BURTON-ROGERS CO. ground connection, Chicago, only agency by which these oscillations may be 26 Brighton Ave. Boston, Mass. radiated. National Distributors But is this true? Can any receiver of the os-

jt Tested and approved by RADIO BROADCAST -Jf RADIO BROADCAST ADVERTISER 183

yimiiiiimiiiiimiimiMiiiiiimiMiiiuiimimimiiiimiimiiiimimiiiiimiimmiiiiiiiiiimim^ dilating type be rightfully considered non- radiating even though it be provided with a blocking arrangement? Granting that we do eliminate radiation from the antenna, does the Increases matter end there? Is the antenna system the sole medium through which a receiver may radiate? Range No, it is not!

And here I wish to step out of the beaten track long enough to state that the coils of any type of oscillating receiver must be reckoned with! This has long been known in theory and, if the space this phase of the radiation situation Clearer has been granted in the magazines may be taken as a criterion, then it would appear that this fact Tone has been known in theory only. I do not recall a single article wherein the writer made any mention of it. No one, apparently, seems to have thought it worthy of even passing consideration. Greater RADIATION FROM COILS IS POSSIBLE Volume made by the writer indicate quite TESTSconclusively that an oscillating receiver does Shown here exact ,ite not depend wholly upon the antenna system for njo. 25 Copper Web radiation, but that the coils in the oscillating circuits can and do radiate, and that this radiated BRAIDED RIBBON energy may carry for some distance, and cer- Indoor or Outdoor tainly create interference within a reasonable area, the extent of which can only be vaguely ANTENNA WIRE guessed at. -is made of 25 strands of copper wire braided Made in copper, tinned copper and enameled This is in the nature of quite logical; very into a strong flexible ribbon aerial three-eighths copper, and put up in coils of 50 ft., 100 ft., in 100 150ft. on of 500 ft. things it couldn't be otherwise. And those who inch wide, and containing each feet and spools one-half mile of single copper strands. I are to the but at the same nearly willing grant theory This gives greatest possible capacity and We also make round, braided and stranded time claim that the energy radiated by a small conducting surface. antenna wires all metals. i Litz Wires Cotton Covered Wires Springs coil, or coils, would be so infinitely little as to be = incapable of causing any appreciable interference, will have to give the subject more serious ROSS WIRE COMPANY consideration. 69 Bath Street Providence, R. I. We have only to remember the tremendous XlinmiuillH mimum iimimimmim iimmiimmiiimnimmimi iiinimimiimimimmiimii miiinii iiiiiinmiimimim iiiiniiimimiimfB distances being covered by members of the amateur transmitting fraternity to realize completely just what a vacuum tube is capable of. Only RADIO PANELS MORE PROFITS recently were we informed of the accomplish- OF GENUINE BAKELITE ments of an amateur in British Columbia. This Cut, drilled and engraved to order. Send rough sketch the PROFESSIONAL for estimate. OurNew Catalog on Panels, Tubes and for gentleman, using an ordinary receiving tube Rods all of genuine Bakelite mailed on request. and less than three-hundred volts of B battery STARRETT MFG. CO. if SET BUILDER for the plate voltage, actually succeeded in es- 521 S. Green Street Chicago, 111. VX7E have an unusually interesting tablishing communication with a brother ama- * * proposition to make to the man teur in Australia! who is now building (or has the ability Then again, one constantly hears of amateurs to build) radio receiving sets for resale. who, with receiving tubes and only ninety volts Read Radio Broadcast This is a real Write to- on the plate, get a range of from ten to twenty every month. You can't afford to miss an issue. Order opportunity. your from your Newsdealer or Radio Store. If for full information. miles, with good, strong signals at the receiving copy day you wish to subscribe direct send #4.00 for one year end. And bear in mind that this is with ordin- or $6.00 for two years. Gearhart-Schlueter Radio ary receiving tubes. DOUBLEDAY, PAGE & COMPANY Corp. Consider, then, is it not logical to suppose that Garden City, N. Y. 716 Voorman Ave. Fresno, California a small coil, perhaps four inches in diameter and wound with a large size wire, connected in the grid circuit of an oscillating tube, or three such LEARN THE CODE AT HOME with the OMNIGRAPH the Wlrelen and Morse Codes "Just Listen The Omni- THE OMNIGRAPH Automatic Transmitter will teach yon both right coils (as in a two-stage tuned radio-frequency and Connected with Buzzer and Phone will do the In your own home quickly, easily Inexpensively. Buzzer, teaching" at from 5 to 50 words a minute. amplifier), will also send out a certain amount of or to Sounder, it will send you unlimited messages any speed, THE OMNIGRAPH is not an experiment. For more than 15 years, it has been sold all over the world energy? Why not? They are, in effect, minia- with a money hack guarantee. The OMH1GRAPH is used by several Depts. of the U S. Govt. in fact, the Dept. of Commerce uses the OMNIGRAPH to test all applicants applying for a Radio license. The ture loop antennas, and it is a well-known fact OMNIGRAPH has been successfully adopted by the leading Universities, Colleges and Radio Schools. three models. DO IT TO-DAY. that it is possible to transmit over short dis- Send for FREE Catalogue describing 1 Hudson St. New York tances with a loop. A small coil, such as is THE OMNIGRAPH MFG. CO., 3K City If you own a Radio Phone set and don't know the code vou are misaing most of the fun generally used in present-day receivers, would send out a very weak wave, and although on the lowly crystal set it would probably make no impression, with most sets of to-day capable of extremely high amplification, the matter takes on a greater significance. The fact that it is not solely the power used at a transmitting station which determines the range of that transmitter ammarlund but also the degree of radio frequency amplifica- F> REC /S /ON tion at the receiving end, has been amply demonstrated in other branches of radio transmission. PRODUCTS RESULTS OF ACTUAL EXPERIMENTS Send 10 cents for illustrated booklet, "How to Build the IIammarlund-Roberts Receiver" HAMMARLUND MANUFACTURING CO. broadcasting commenced on a large 424-438 West 33rd Street New York City WHENscale a few years ago, and it was found that oscillating receivers became miniature trans- Tested and approved by RADIO BROADCAST 184 RADIO BROADCAST ADVERTISER

See That Screw^f mitters under certain conditions, and so caused A screw-driver adjusts interference to neighboring receiving sets, no an X-L in crowded one thought that these radiations could places possibly carry for any great distance. The writer recalls an article published over three years ago wherein X-L its author stated that "such a receiver may VARIO cause interference to other listeners-in within an area of several blocks." \^^^ If DENSER-a--'' - i 1. 1 K_7 JL-. A ^. it is a JVbJfoises! To-day, generally understood fact that in easier tuning, more distance, volume this is several no one knows Tones voices more RESULTSand clarity greater stability. Indorsed by leading range perhaps miles; clearer, distinct, and authorities. exactly. But we do know that it varies in direct volume greater with AMPERITE. No mov- It Model "N" A slight turn obtains correct tube oscilla- proportion to the efficiency of the radiating re- ing parts. brings the utmost out of each tion on all tuned radio circuits. frequency Neutrodyne, ceiver and the of the receiver individual tube. Specified in all Roberts two tube. Browning-Drake, McMurdo Silver's sensibility picking popular sets. Knockout, etc., capacity range 1.8 to 20 micro-m cro- up these radiations. construction Price $1.10. farads. Price $1.00 And so, when a sensitive receiver, such as a Model "G" With grid clips obtains the '^yZgdiall if proper grid super-heterodyne, a or a Roberts is Gotnpany on filter neutrodyne, capacity Cockaday circuits, and intermediate Dept. R. B.-6, 50 Franklin Street New York City frequency tuning in heterodyne and positive grid bias being employed at the receiving end, the matter in all sets. .00016 to Capacity range .00055 and .0003 of radiation direct from the coils of another set to .001 microfarads. Price $1.50 Write for in the neighborhood assumes a serious aspect. X-L Push Post Push it down with FREE And as the art and sets are your thumb, insert wire, remove progresses receiving Hook-ups pressure and wire is firmly held. continually improved upon and made more and Releases instantly. Price 15c. more efficient, likewise this side of the radiation Push Post Panel permanently mark- nuisance will become more acute. ed in white on black rubber. In box Reference including soldering lugs, raising bush- was made above to some tests made and screws for mounting, etc. ings pertaining to this class of radiation. Briefly, Price, $1.50 they were as follows. STATEMENT OF THE OWNERSHIP, MANAGE- Using an oscillating two-stage tuned radio MENT, CIRCULATION. ETC., required by the Act of Congress of August 24, 1912, of RADIO BROAD- frequency set with only forty-five volts on the CAST, published monthly at Garden City, New York of for plates all tubes, and employing neitner an April 1, 1926. State of New York, County of Nassau. antenna nor a|ground the equivalent of the most Before me, a Notary Public in and for the State efficient device the writer caused so and X-L RADIO LABORATORIES blocking County aforesaid, personally appeared John J. 2424 Lincoln Avenue Chicago, III. much interference to a friend with a five-tube Hessian, who, having been duly sworn according to law, deposes and says that he is the Assistant Treasurer of set located one hun- 22'/2 Volt neutrodyne approximately Doubleday, Page & Company, owners of Radio Broad- dred feet cast and that the is, to the best of his un-acid away, that it was an absolute impossi- following > f tl> P Mil knowledge and belief, a true statement of the owner- bility for him to a concert from a station everlasting enjoy ship, management (and if a daily paper, the circula- miles 'distant. This was also done with a tion), etc., of the aforesaid publication for the date rechargeable twenty shown in the above caption, required by the Act of four-tube Teledyne set, the only difference being "B" August 24, 1912, embodied in section 443, Postal that the shrieks and howls were not so loud. Laws and Regulations, on the reverse of this Storage Battery printed form, to wit: This, of course, was due to the fact that the 1. That the names and addresses of the $ detector alone was publisher, 2.95 responsible for the interfer- editor, managing editor, and business managers are: ence since the radio frequency tube was not Publisher. Doubleday, Page & Co Garden City includes N. Y.; Editor, Willis Wing, Garden City, N. Y.; whereas with the tuned radio fre- chemical oscillating, Bmintis Managers. Doubleday, Page & Co., Garden N. Y. - STOMK quency set, all three tubes were oscillating. City, HJWIH 2. That the 45 volts 90 owner is: (If the publication is owned $5.25, Pooh! you say, that's one hundred feet. ToltallO.OO. 112% only by an individual his name and address, or if owned volt* $12.50, 135 True enough. But the radiations, especially those by more than one individual the name and address of volts $14. 75. 157% each, should be given below: if the publication is v ol t B $16.80. from the r. f. set, were received the by neutrodyne owned by a corporation the name of the Truly the biggest buy today. Easily charged on any current includ- corporation with such that it is the ing 32 volt systems. Any special detector plate voltage had. Tested intensity safe to say that they and names and addresses of .the stockholders own- and approved by leading authorities etit-h as Popular Radio labora- ing or holding one cent, or more of the total carried for several blocks at the least. 1 1 is per tories. Over 3 sold on a non-red 30 quite years tape day trial offer with amount of stock should be given.) F. N. Doubleday complete refund if not thoroughly satisfied. Further guaranteed 2 possible that they carried all over the city. Garden City, N. Y.; Arthur W. Garden y*ars, Knock-down kiW at greater savings. Complete "Hawley" Page, City "B" 75. N. Y.: S. A. Garden Battery Charger $2. Sample cell y>c. Order direct send no It is, therefore, not a very difficult thing to Everitt. City, N. Y.; Russell money simply pay the expressman cost on delivery. Or write for Doubleday, Garden N. Y.: Nelson realize City, Doubleday, my fre literature, testimonials and guarantee. Same day shipments. just what this would mean in a con- Garden N. very City, Y. ; John J. Hessian, Garden City, B. Hawley Smith. 312 Washington Ave.. Danbury, Conn. gested district where every other house boasts an N. Y.: Dorothy D. Babcock, Oyster Bay N Y Alice De Graff, Oyster Bay, N. Y.; Florence Van antenna and where there are several receivers in Wyck Doubleday, Oyster Bay, N. Y.; F. N. Double- one apartment building. Even assuming that day, or Russell Doubleday, Trustee for Florence Van

Wyck Doubleday, Garden City, N. Y. ; Double- none of the receivers could radiate directly from Janet day, Glen Cove, N. Y.; W. Herbert Eaton Garden their those which could be to os- antennas, made City, N. Y.; W. F. Etherington, 50 E. 42nd St., C. cillate would still create sufficient interference to N. Y. ; S. A. Everitt or John J Hessian, Trustee for Josephine Everitt, Garden City, N. Y.: Henry L make the air unhealthy for, no one knows 285 Madison just lones, Ave., N. Y. C. ; Wm J. Neal how far. Garden City, N. Y.: Daniel W. Nye, Garden City N. Y.: Mollie H. Page. Syosset, N. Y.: E. French The whole boils down to the fact that thing Strother, Garden City, N. Y. the oscillating receiver is the bugaboo of good 3. That the known bondholders, mortgagees, and other security holders owning or 1 cent. reception. And as long as we have these re- holding per or more of total amount of bonds, mortgages, or ceivers, or no means of positively preventing all other securities are: (If there are none, so state) NONE. forms of radiation from them, radio broadcasting 4. That the two paragraphs next above, giving the is not to attain its of going highest pinnacle names of the owners, stockholders, and security hold- development. And while it would be difficult to ers, if any, contain not only the list of stockholders and security holders as they appear upon the books advocate the abolition of the re- EROVOX regenerative of the company but also, in cases where the stock- ceiver altogether, at the same time it is to be sin- holder or security holder appears upon the books of the company as trustee or in any other re- cerely hoped that a few of our great scientists fiduciary "Built Better" lation, the name of the person or corporation for will turn their attention to this subject with whom such trustee is acting, is given; also that the said two contain statements perhaps worth while results. paragraphs embracing RESISTOFORMERS affiant's full knowledge and belief as to the circumstances and conditions under which stockholders and Tested and approved by M.I.T., security holders who do not appear upon the books of the company as trustees, hold stock and securities Yale, Radio News, Popular (It is apparent from Mr. Jolliffe's remarks that in a capacity other than that of a bona fide owner; Science. the receivers which are sold with an almost Radio, and Popular many of and this affiant has no reason to believe that any Used by over 200 of Amer- iron-clad guarantee to the effect that they will not other person, association, or corporation has any interest direct or indirect in the said or ica's leading set manufacturers. radiate, are capable of doing so by means of their stock, bonds, other securities than as so stated by him. coils. On the strength such as the WIRELESS CORP. of guarantees 5. That the average number of copies of each issue AEROVOX above, many owners of receivers permit their sets to of this publication sold or distributed, through the mails or to subscribers 489-491-493 Broome St., New York squeal during the process of tuning-in, blissfully otherwise, paid during the six months preceding the date shown above is ignorant of the fact that they can be seriously an- Branch Offices: (This information is required from daily publications their It is that this article St. Louis, Mo.. Syndicate Trust Building noying neighbors. hoped Cincinnati, O., 304 Palace Theatre HI JB- has made clear to these listeners that even the so- (Signed) DOUBLE DAY, PAGE & COMPANY 53 Boulevard John J. Hessian, Ant. Treasurer. Chicago, III., W. Jackson called "non-radiating" receiver will cause interfer- By Boston, Mass. - - - 94 Portland Street Sworn to and subscribed before me this 1st day of ence not handled with meticulous care. The Los Angeles, Cal., 324 N.San Pedro St. if April, 1926. Editor.) [SEAL] (Signed) William W. Thornton (My commission expires March 30, 1927.) jr Tested and approved hv RADIO BROADCAST -f RADIO BROADCAST ADVERTISER 185

SEND THIS IN- | I Radio Institute of America

Broadway, New York City . 1328 Please send me full information about I

your Home Study Course of radio in- 1 I struction.

J - . I am interested in the complete course, ) AMPLIFIER | including code instruction, which qual- p for the U. S. Gov't Commercial or . Amateur Radio License. Iifies I am interested in the technicalcourse IDfor radio dealers, jobbers and salesmen. ] in I Name... Broadcasting Australia 1 Address. I N THE December issue of RADIO BROAD- * CAST appeared a list of Australian broadcasting stations as forwarded to this Your Chance magazine by Mr. A. W. Watt, editor of Australian Wireless Weekly. Apparently ASSURES PERFECT Is Here! there have been some slight alterations in REPRODUCTION the list since its publication, as the follow- You will receive the program exactly There is a dearth of radio ing letter will make clear. It is from Mr. op- as broadcasted, if you substitute a M chief of the erators and our graduates are J. alone, manager Wireless De Jur Resistance-Coupled Amplifier Branch of for the audio transformers in set. in greater demand than ever! the Postmaster-General's De- your partment of the Commonwealth of Aus- Voice and music will be reproduced Radio Institute of America of- with great volume and without tralia. It reads as follows: fers you a thorough radio course any distortion. that secures your Government Editor, RADIO BROADCAST. Equipped with De Jur Parts License leads right to your Doubleday, Page & Company, Garden City, New York. Sockets of Genuine Bakelite and take first job. Classroom or home standard or new UX tubes. Built study instruction. That means SIR: with .1 Bakelite Impregnated Mica I notice in December issue Condensers Resistors. you can study in your own home. your a reference to and Dejur our Broadcasting Stations' wavelengths which No bus bar in All metal contain some incorrect wiring. strip For full information particulars. The wave- connections are riveted. No screws, lengths and powers of the stations listed on page mail the coupon. nuts or bolts to work loose. 224 should read as follows: RADIO INSTITUTE WAVELENGTH Sold by all Dealers Get the Genuine OF AMERICA CALL SIGNAL !N METERS POWER IN WATTS Pormerlv Marconi Institute Established in 1909 Write for De Jur Catalog 2 FC 1 100 328 Broadway New York City 5000 2 BL 353 1500 (shortly to be increased ^DeiluR PRODUCTS World's to 5000) ^The ^larqMt Munufui'lui-ers of Idle 3 LO 371 5000 Make Good Receiver 3 AR 384 1 500 any* 5 CL 395 5000 * BETTER 6 WF 1250 5000 7ZL 417 3000 C.E.MFG.CO. 385 5000 Makelfour Own Providence I. We are at present considering the reallocation of the Cone wavelengths, and there are likely to be Speaker some slight modifications to permit of a wider - frequency band being employed. andSave f25 Trusting you do not mind my correcting these (All Parts Supplied) slight inaccuracies. $35 or more Very truly yours. Why pay for a cone speaker when J. MALONE, can assemble ELECTRAD Chief Manager, Telegraphs and Wireless you easily a Melbourne, Australia. splendid supersensitive one with the complete Don't Fool With Lightning! parts we send you and From an Old-Timer save $25? It doesn't pay to We include a special economize on a cone blue I I ERE is a letter from an old-timer in the unit, print and lightning arres- ' ' simplified directions for as- ter, or to "wireless" who was attracted game by sembling. Directions are use one you Mr. Baskerville's article of his experiences so clear anyone can easily aren't sure which appeared in the RADIO BROAD- set it up in a few hours. of. You May It's a big cone, eighteen can't col- CAST. inches high, complete in lect insur- tetrad Certified Lightning Arreitor every detail. Unmatched ance unless Editor, RADIO BROADCAST, for beauty, and reproduces you have an arrester capable of passing the National Doubleday, Page & Company, Board of Fire Underwriters. Put in music and voice with fault- an Electrad Cer- Garden City, New York. tified Arrester then less Lightning you're sure. SIR: accuracy. The ccst is amazingly low only $10 Air'gap type, exterior moulded porcelain, attractive I was carried back to old times by Mr. Basker- finish. sealed and lit- for the most Completely moisture proof. Cost ville's article in the current RADIO BROADCAST. complete ap- tle, simple and easy to attach. At all good radio stores, form of loud It recalled the in the service of the old proved speaker 5oc;in Canada 75C. Outdoor type $i.?o;in Canada $2.10 days known. Big saving is due tc elimination of labor in United Wireless, at 42 Broadway, when I worked assembling and packing and because we save jobbers' with Baskerville, Murphy, Hughes, and Gregg, and dealers' profits. for several years. I wonder where John Murphy is to-day? Send no For control of tone money perfect It was a great life in those days, equipping a and volume use the Electrad Simply send name and address for the complete 500,000 ohm compensator. ship one day, the roof of the Waldorf Astoria the outfit. When postman brings package, deposit only For free hookup write 428 next, and then off to Key West to install a sta- in full If not satisfied re- Broadway, New York City. $10.00 payment. entirely tion. I well recall being given the job of equip- turn parts within ten days and your money will be ping the Olivette and Mascotte when down at instantly refunded. Never before has a better radio Key West. These had been Sampson's dispatch bargain been offered. Write at once. boats during the Spanish-American war, were very fast, top heavy, and great rollers. It fell SCIENTIFIC RADIO LABORATORIES ELECTRAD to lot to these vessels while on the 254 my equip trip W. 34th St., Dept. 26, New York City

f Tested and approved by RADIO BROADCAST -j 186 RADIO BROADCAST ADVERTISER

between Key West and Havana, and it was the hardest job I ever tackled. The rolling of the ships necessitated frequent trips from the wireless room to the rail, while the dining room had

DIAMOND-WEAVE little attraction. . (TRADE-MARK REGISTERED Aug. 4, 1925) One morning, upon my arrival at 42 Broad- way, I was informed by Mr. Murphy that it was up to me to leave for Porto Rico on a steamer leaving New York in three hours, to install a SICKLES station there, and to from the Insular procure government permission and land to build it on. I left the office and, with a small handgrip as my COILS only baggage, caught the boat as she was casting off her lines. I never built the station at Porto " For the "Aristocrat," Rico, however, for shortly after, the old "United became a thing of the past. That little incident Browning-Drake, Roberts, helps to show what kind of a life we fellows led Sickles Coil Set No ISA for Roberts and Circuits though. Circuit, containing our new center- Craig, Hoyt Yes, it certainly was a great life, coming into tapped N-P Coil. Price $8.00. (Patented Aug. 21, 1923) intimate contact with governors, generals, ad- Our Coil Set No. 25 is specifically de- mirals, haughty captains, plain spiggotys, dock- Sickles Coils the "Aristocrat" and above a member of that for signed for the new "Aristocrat" Circuit, rats, all, being Circuit, new scientific bunch of good fellows the old United Wireless. designed upon already very popular. discoveries, set highest standards of And now, as 1 write, wjz is booming in. What of of con- efficiency. Compactness form, rigidity a contrast to the old days when a readable spark struction, and the supremely efficient from a lo-kilowatt transformer, sending from Diamond-Weave method of winding are Key West to Havana, was hailed with satisfac- COIL PRICES well-known characteristics of Sickles tion and which the operator generally received Coils. over an illicit electrolytic detector which Hughes No. ISA 8.00 set Roberts Circuit $ knew nothing about. These refinements of and con- No. 24 Browning-Drake 7.50 set design Very truly yours, struction result in low distributed ca- A. A. No. 20 Craig Circuit 4.50 set WEISS, pacity, low dielectric losses and large Copperhill, Tennessee. No. 19 Acme Reflex 4.50 set range of frequency with small variable No. 8 Knockout Reflex 4.00 set capacity. Our Laboratory Articles No. 21 Circuit 10.00 set Hoyt There are Sickles Diamond Weave No. 25 "Aristocrat" Circuit 8.00 set a letters into the Coils for all leading circuits. UITE few come ice following publication of Keith Send for descriptive catalog Henney's articles in this magazine, express- ing, as a rule, unqualified appreciation, and The F. W. Sickles Co. often offering suggestions for future sub- 132 Union Street jects. Here are two typical ones. The first is from the of while SPRINGFIELD, MASS. ex-operator CNRO, the second is from a prominent tube manufacturer.

A Two Year Saves You Two Dollars Editor, RADIO BROADCAST, Subscription Doubleday, Page & Company, Garden City, New York. It saves you the bother of renewing next year. It is the most economical way to subscribe. You simply write six dollars in- SIR: a line to that the last issue of "our stead of four when sending your check or money order. Try it for two years. Form Just say is a knockout. The the habit! magazine" expression "The Leading Radio Magazine" hardly covers RADIO BROADCAST Garden City, N. Y. it. I would very much like to see more of Keith Henney's work, such as that which appeared in the December RADIO BROADCAST. This is the finest way of holding interest in the radio game. I would like to see a department for the experimenter, covering coil resistance, capacity bridges, etc. Keep up the good work. Very truly yours, H. A. HARRIES (9 BG) Westmount, Province of Quebec.

Lowest Losses! PERRYMAN ELECTRIC COMPANY NORTH BERGEN, NEW JERSEY Low ^linimum ! Editor, RADIO BROADCAST, High. Maximum ! Doubleday, Page & Company, Garden City, New York. Permanent Calibration ! SIR: ! Everlasting I take this opportunity of complimenting you on Mr. Henney's article appearing in the Compact ! February RADIO BROADCAST under the heading "How to Judge and Use Vacuum Tubes." Ideal Curve ! Tuning Never before have I read an article that was so (Modified Straight Frequency) concise, precise, and simple in its technical detail. The ordinary layman can grasp its mean- Used all ! by experts ing and fully realize the importance stressed on the proper use of radio tubes. Very truly yours, The Finest Condenser Ever Made I A GEORGE H. FERRYMAN. Write for 36 page booklet ^^ arfctoell Confcensera 81 PROSPECT STREET BROOKLYN, N. Y. THE STANDARD O F COMPARISON

Tested and annroved bv RADIO BROADCAST RADIO BROADCAST ADVERTISER 191

remarkable improvement in audio amplification unit perfected by All-American Engineers gives you the natural tone full, pure, you have always sought

have always wanted the ideal result in audio pedance coupling coordinated to retain tne advantages YOUamplification pure, natural tone with good vol- of both and to eliminate their weaknesses. ume. The laboratories of All-American Radio Corpora- This new method consists of a Rauland-Lyric trans- a of audio tion have developed new method amplifi- former for the first stage, a Rauland-Trio Type R-3OO cation and to this ideal for now bring you long sought impedance the second stage, and a Rauland-Trio Type in 10 result the R-3 impedance for the third stage.

You know the Rauland-Lyric transformer. Its excep- This is a triple feature instrument containing an induc- tional tone perfection has made it the largest selling tance, a capacity and a resistance in one compact impe- transformer is dance unit. quality in the world. The Rauland-Lyric Through laboratory tests of utmost preci- now used in combination with the new Rauland-Trio sion, absolutely correct balance is maintained between (impedance units) to produce the Rauland-Lyric -Trio these important factors. You secure full advantage of amplifier the highest known perfection impedance amplification and overcome the in three stage audio amplification. common variance of commercial types of It is well known that any system of ampli- condensers and resistances. Rauland -Lyric - Trio is the last in fication using instruments of similar char- word audio amplification. acteristics has inherent disadvantages. Rau- A free book, "Modern Audio Amplification," tells land- combines the Lyric-Trio successfully more about this interesting new development. Write for two leading systems transformer and im- handbook B-c/o. ALL-AMERICAN RAD IO CORPORATION 4211 A. BELMONT AVE. , CHICAGO, U.S.

Station WENR 266 Meters is owned and operated by the All -American Radio Corporation

Tested and approved by RADIO BROADCAST