with whic is combined 1he Wive1css Aite JA 1926

How to tet t1e Most Out of Your LC26 Iceìver

www.americanradiohistory.com gimme your radio set more power with one new Radiotron, DRIVE a car uphill beyond its power -and the motor knocks. Drive a radio set beyond its power -and the last tube hokes. But change one single tube in he set-and you have the power you eed for greater volume and finer tone. The new RCA power tubes add about fifty per cent greater efficiency to any radio set. They cost but $2.50, and need only an inexpensive adapter and a little extra current. Change the tube of the las audio stage to a new power tube, as any dealer will show you -and in ten minutes you have a new s

RADIOTRON RADIOTRON Radiotron UX- I 12 UX -112 UX -120 The new storage The new dry bat- battery power tery power Radio - Radiotron UX -112 tron UX -120 may may be used in sets be used in sets that that use Radiotron use Radiotron UV- UV-201-A. 199. Radiotron UX-112-$6.50 Radiotron UX-120-$2.50

You would not use any but a Mazda lam in your lighting circuit. Why use any hut an RCA Radiotron in your radio set? They are liomade by the same skilled workers, backed by the same research laboratories. But the Radio - Iron is far more delicate to make. Radiotron UX-120

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TheTypeH a horn of graceful lines and antique green and black finish. The Brandes Cabinet of Great in volume - mahogany, finished in wal- The Brandes Cone -a true in tone. Ad- nut brown. The same unit, truly decorative bit of justable. quality of tone and even furniture that conceals greater volume than the a remarkable speaker. Type H Speaker.

The Adjustable Table -Talker. Gooseneck horn. Finished in brown -felt -padded base. The Superior Matched Adjustable. A most Tone Headset is now, as The Audio Transformer - always, ideal to tune in amplifies at an unusually satisfactory buy. listen undisturbed with -to high ratio - 1 to 5. Two and undisturbing. steps of amplification may be used without trans- former distortion.

Send for an interesting The new Brandes Speak- booklet describing ers- perfected now after Acoustics by Brandes. many busy years of ex- periment -give new clar- Brandes Products Corp. ified mellowness to the 200 Mt. Pleasant Ave. low tones, new rounded Newark, N. J. sweetness to the high. Be sure your set is in its best voice - always -with acoustics by Brandes. The Phonograph Attach- ment -a splendid speaker with any good phonograph. V Same unit as type H horn. Adjustable and furnished with a connection to fit all phonographs. o Copyrighted by Brandes Products Corp., 1926

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com POPULAR RADIO WITH WHICH IS COMBINED "THE WIRELESS AGE" EDITED by KENDALL BANNING

FOUNDED 1911 CONTENTS for JANUARY, 1926 (Cover design by Frank B. Masters) VOLUME IX NUMBER 1 The Modern Tower of Babel FRONTISPIECE The New Wave -Transmission Phonograph Henry C. Harrison..... Page 3 How to Get the Most Out of Your LC -26 Receiver L M. Cockaday and S. G. Taylor 10

Will Radio Kill the Small Newspapers' Paul Dupuy . 22 The Atom William Bragg 24 Article No. 4: The Nature of Crystals Some New and Useful Facts About Cols D. R. Clemons 30 When Your Set Won't Work Edgar H. Felix 40 A Measurement Chart Raoul J. Hoffman 45 No. 13: For Use When Selecting a Rheostat for a Multi -Tube Circuit Straight- Line -Frequency Condensers Herbert J. Harries 48 Simple "How -to- Build" Articles for Beginners. Laurence M. Cockaday 56 No. 14: How to Build a One -Tube Regenerative Receiver for Use With the New UX -199 Tube Handy Tools for Radio Fans The Technical Staff 60 No 9: The Hand Drill DEPARTMENTS In the World's Laboratories E E. Free 61 What's New in Radio Apparatus The Technical Staff 69 The Broadcast Listener Raymond Francis Yates.. 74 In the Experimenter's Laboratory Laurence M. Cockaday... 80 Some Methods for Determining the Distributed Capacity of Coils 80 How to Simplify Connections 83 A Milliammeter as an Aid in Preserving Batteries 83 Making the Tuned Radio - Frequency Receiver More Selective 83 The Old Reliable Single -Layer Solenoid Coil ß3 Pure DC Power Supply for a Five -Watt Transmitter ß4 Balancing the Single Control Superheterodyne 87 Broadcasts J Andrew White 89 With the Inventors William G. H. Finch. 96 Listening In Lloyd Jacquet 100

VOLUME IY JANUARY, 1926 NUMBER 1 Published monthly by Popular Radio, Inc., 627 West 43rd St., New York. N. Y., telephone num- ber, Chickering 1906; Douglas H. Cooke, President and Treasurer; Kendall Banning, Vice-Pres- ident; Laurer.:e M. Cockaday, Secretary; Joseph T. Cooney, Asst. Treasurer. Price 25 cents a copy; subscription $3.00 a year in the U. S., Canada and all countries within the domestic postal zone; elsewhere $3.50 a year, payable in advance. The International News Company, I.td., No. 5 Bream's Bldg., London, E. C. 4, sole distributors in England. Entered as second class mat- ter April 7. 1922, at the Post Office at New York. N. Y., under the act of March 3, 1879. Copy- right, 1926, and title registered as a trade -mark by Popular Radio, Inc. Copyright in Great B -stain by Popular Radio, Inc.. 6 Henrietta St., Covent Garden, W. C., London, England. Printed in U. S. A. LAURENCE M. COCKADAY. Technical Editor E. E. FREE, Ph.D., Contributing Editor JOHN V. L. HOGAN, Contributing Editor

For advertising rates address E. R. CRONE. & COMPANY. INC. New York: 25 Vanderbilt Avenue Chicago: 225 North Michigan Avenue 2

www.americanradiohistory.com The Best in Radio Equipment 3

240 meters \\\w1uuliiulua7,i A 50 g Ì%, \ á0 N2N .30 0

. Ói ó;..-

Can Your Set Receive All Stations?'

OVER 100 stations are broadcasting on less than 240 meters. How many are beyond the reach of your set? The Synchrophase can get them all. Grebe Low -Wave Extension Circuits make possible a range of from 550 down to 150 meters. This is accomplished by an auto- matic switch which enables one dial to cover two wave ranges. The first, from 550 to 240 meters, corresponds to the practical tuning range of the usual sét. The second overlaps this and extends down to 150 meters. To change from one range to the other is simplicity itself. Simply move the center dial past the 100 mark for the high range and beyond the zero mark for the low range. The Synchrophase is thus well -equipped to take care of future station assignments as well as all present ones. Ask your dealer to demonstrate this and other Grebe advances in radio development A. H. Grebe &. Co., Inc., 109 West 57th St., New York Factory: Richmond Hill, N. Y. Western Branch: 443 So. San Pedro Street, Los Angeles, Cal.

This company owns and operates stations WANG and WBOQ; also low wave rebroadcasting sta- tions, mobile WMU, and marine WRMU.

"The Gods cannot TRADE MARK. REG. U.S. PAT, OFFR, help one who loses opportunities." -Mencius The wise man will provide against the future by securing a Synchrophase. All Grebe appa- ratus is covered by patents grant- ed and pending.

The Synchrophase is also sap - plied with base for batteries and ill a de tusi Console Model.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com PAGES WITH THE EDITOR PERHAPS some day a scheme will be devised for checking of POPULAR RADIO probably has -based on their up on the actual number of read- personal observations. ers of each copy of POPULAR RADIO. * * * ON page 449 of POPULAR ORDINARILY RADIO for Novem- a magazine publisher assumes ber (in "Practical Pointers about Trans- that there is an average of five readers to every formers" by Frederick copy. The E. Nimmcke) the circulation of POPULAR RADIO among author gives formula No. 11 radio clubs, as follows : electrical laboratories, business of- S = H + a inches. fices, schools and colleges would indicate that The author writes that the formula should this average is at least maintained and prob- have appeared thus: ably exceeded. And reports like the following S tend to =H + 2 X a inches. confirm this impression : * * * * ON page 98 of this number of POPULAR Mr. Lloyd Jacquet RADIO "A COUSIN of mine in America," writes C. R. makes his first appearance Boydell of Manchester, as the conductor of the department England, "posts In." "Listening POPULAR RADIO to me, and when I've read it I * * * pass it around to all of my radio friends, who look forward to it THIS department will be made up as they look forward to communications entirely of their meals." from broadcast listeners and * * * experimenters who have discovered useful and helpful bits of THE Editor would like information that they are willing to get reports from to share with the Other Fellow. readers about the numbers of readers each copy (Continued on, page 6)

From a photogrpl, for POPULAR RADIO WHERE POPULAR RADIO'S EXPERIMENTAL WORK IS DONE In the POPULAR RADIO LABORATORY in experimental New York is conducted a large part of the and development work on which the Here, also, are articles in this magazine are based. tested all of the radio apparatus that is This laboratory is supplemented submitted for approval. by laboratories maintained by individual members of the Technical Staff. 4

www.americanradiohistory.com The Best in Radio Equipment 5

A vBllcq }osssoC MICADON TYPE 640 .02 MFD. PATENTS PENDING MICADONS Found in famous radio sets In radio sets that have earned fame and a reputation for quality, you will find Micadons the foremost fixed condensers of radio. Over 25 million in use More that 2 5 million Micadons are today giv- ing satisfactory service -they are found in 90'', of all the radio sets in use. The reason is Dubilier knows how to make efficient fixed condensers and their methods are fully pro- tected by basic patents. Micadons are the result of twenty years' intensive, scientific research. Dubilier CONDENSER AND RADIO CORPORATION

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com PAGES WITH THE EDITOR (Continued from page 4) ALL readers are invited to send in the suc- was appointed cessful results of their experiments to Committee No. 4 on "Oper- Jacquet. to Mr. ating Regulations." Mr. Wm. Make the letters short and to the point (who G. H. Finch -and enclose diagrams conducts our department "With the In- or photographs if they ventors") and Mr. add interest or value to the text. John V. L. Hogan, Con- * tributing Editor, were both appointed mittee to Com- NEXT month No. 1 on "Allocation of Frequency or POPULAR RADIO will present its Wavelength Bands." readers with another "how -to- And six more of POPULAR build" article on RADIO'S contributors were honored which its creator, Mr. R. J. Griffith, in collabo- ments. by appoint- ration with the staff of the POPULAR RADIO * * * LABORATORY has been long engaged. It has termed been A REPORT of the activities of the conference the Orthophase Receiver. and of the * committees will appear in the next issue of this magazine. THE distinguishing features of the Ortho- phase Receiver during the period * * * of its develop- "YOUR pleased ment, extending over a period of several months, readers have complimented have been ou on nearly everything summarized thus : in connection with the 1. Extremely good selectivity. :ontents of your magazine from your probity of 2. High sensitivity. purpose to the accuracy and lucidity of your 3. Good tone quality. articles and instructions upon things radio," 4. Simplicity of construction. writes Mr. P. W. A. Fitzsimmons, president of the * * * Michigan Mutual Liability Co., "but I have never seen Dr RING the experimental work the set in the a compliment paid to the de- POPULAR RADIO LABORATORY signer of your front outside in New York con- tions. cover illustra- sistently picked up Pacific Coast stations 15 -foot antenna. on a * * * * * * "Permit me to step into the breach enthusiastically and most FROM the Technical Editor comes this brief do this, because never before description of the new features !lave I seen such simple outlines of correspond- of the Ortho- ingly simple devices phase Receiver : become so artistic as under * * * the treatment which your artist accords The illustrations them. "TILE set comprises one stage of push -pull are distinctive, artistic and radio -frequency amplification well serve the purpose of prompt identification and one stage of of reflexed audio - frequency the various excellent issues of POPULAR amplification, the tubes RADIO. in this reflexed stage being in parallel. Long may you prosper, and may you flexed The re- have no 'interference!' radio -frequency current (which in most " reflex * * * sets is wasted) is built up and its phase reversed, after which it is applied THOSE radio fans who have of to the grids progressed in the push -pull stage, in phase with the incom- their experimental work to the point that they ing oscillations from the antenna, thereby have become interested in transmitting or reinforcing aiding as receiving as well the incoming signal. In the will find in next month's issue of present set one stage of transformer -coupled POPULAR RADIO an article of very particular audio- frequency amplification and value entitled "How to Build and resistance one stage of Low Operate a -coupled audio- frequency is added." -wave Transmitter." * * * * * * THE AMONG Fourth National Radio Conference that the virtues of this particular trans- was convened in Washington, mitting set are the following: retary D. C. by the Sec- of Commerce on November 9 has now * * * passed into history. It was a notable IT is simple of construction. of representatives gathering It has of the radio amateurs, of the a dependable daylight range of 500 broadcast listeners, of the broadcast miles. of the radio stations, It may manufacturers and dealers, and of be built at a cost for parts of only authors and composers whose literary about $25.00, exclusive of accessories. sical and mu- * * writings are now brought by radio before millions of people where before LIKE all of the "how -to- build" they were appear articles that brought before only thousands. in this magazine, the set was con- * * * structed in the POPULAR RADIO LABORATORY tests and and THE full significance of the gathering experiments were conducted upon it appear will not under varied conditions until the nine committees which were until the desired re- pointed ap- sults were attained. And not until to tackle the many problems that beset then was radio begin to function. the "how-to- build" description of it written. * * * POPULAR RADIO took an active conference, part in the not only through its accredited rep- Nara ---atilkkAA/ resentative, Mr. Laurence M. Technical Cockaday, the Editor, but also through some of its staff writers and contributors. Mr. Cockaday Editor, POPULAR RADIO 6

www.americanradiohistory.com The Best in Radio Equipment 7

"These Eveready Batteries are the correct size for your set. With average use they will last you a year or longer "

sets of one to three tubes the With sets of from 1 to 3 tubes use "You have been one of the Eveready No. 772. many who use 'B' batteries No. 772 Eveready "B" Bat- that are too small in capac- tery used with a "C" bat- With sets of 4 or more tubes use ity for their receivers. That tery will last a year or longer. either of the heavy duty batteries, On sets of four and five No. 770 or the even longer -lived makes you buy 'B' batteries Eveready Layerbilt No. 486. twice as often as necessary. tubes, the larger heavy duty size Evereadys Eveready batteries used with We have prepared a new book- Fit the right let, "Choosing and Using the to your set and add a 'C' bat - a "C" battery will last eight or Right Radio Batteries," which we tery,* if you haven't one, and months more. will be glad to send you upon re- you'll get maximum service at The secret of "B" battery quest. This booklet also tells satisfaction and economy is- about the proper battery equip- minimum cost." ment for use with the new power The life of your Eveready LEFT -Eter eady tubes. Layerbilt"B"Bat - Manufactured and guaranteed by "B" Battery depends on its tery No. 486. 45 volts, for maximum NATIONAL CARBON CO.,INc. capacity in relation to your on economy tour, New set and how much you listen five or more tubes. York San Francisco R r G H T- Eveready Canadian National Carbon in. know, through in- DryCell Radio "A" Co., We Battery, 1 % volts. Limited, Toronto, Ontario The battery built vestigation, that the aver- especially for dry age year -round use of a set cell tubes. EVEREADY HOUR EVERY TUESDAY AT 9 P. M is two hours a day. Tak- -Eastern Standard Time ing that average we have For real radio enjoyment, tune in the "Eveready Group." Broadcast through proved over and over on stations- EVEREADY WEAF -New York WCAE- Pittsburgh wa ea- Providence wsai- Cincinnati "Nora: In addition to the in- wEsi- Boston ww.r- Detroit creased life which an Eveready "C" Radio Batteries wTAG- Worcester woe- Davenport s, Battery gives to your "B" batteries, -they last longer wm- Philadelphia wcco ( Afiuneapoli it will add a quality of reception we a-Buffalo Paul unobtainable without it. Ksn -St. Louis 1st.

All a¢j'aratus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 8 The Best in Radio Equipment

Cleartone Five Tube Model 100 'NOT "how many can we make," but "how well can A Gift we make them," is the dominating thought where Cleartone sets are built. Each set is treated as an out of the individual creation rather than one of many. What wonder then that Cleartone sets reproduce with Ordinary unusual clarity of tone. That they possess remarkable selectivity, range and volume. That they are encased in cabinets of exquisite design. Everybody prefers the individual, distinctive, hand - wrought gift. For this reason the Cleartone Five Tube Set will bring more pleasure on Christmas morning than could any ordinary set. LAST MINUTE SHOPPERS If your dealer does not carry Cleartone, wire us for immediate delivery. Price, $85.00 with Radiotron Tubes. Tubes include either five UX 201A, or four UX 199 and one UX 120 power tube. Use with either dry cell or storage batteries. We also sell seven -tube loop sets, complete. Noth- ing additional to buy. THE CLEARTONE RADIO COMPANY 2427 Gilbert Avenue, Cincinnati, O.

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All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com A Unique Combination of Technical Information and Human Interest "THERE is no maga :inc like POPULAR RADIO for a happy balance between the technical news of progress in radio that one must read, and good `human interest' features that one may enjoy." aeD J PRESIDENT, SLEEPER RADIO CORPORATION.

www.americanradiohistory.com Kadel & Herbert The Modern Tower of Babel "I will lead them in paths that they have not known; I will make darkness light before them, and crooked things straight." -ISAIAH, 42 :16.

!A

www.americanradiohistory.com WITH WHICH IS COMBINED " THE WIRELESS AGE"

VOLUME Ix JANUARY, 1926 NUMBER 1

The New Wave- Transmission Phonograph

ONE of the most important advances made in the science of sound is the creation of the new talking machine that involves the use of mechanical apparatus and principles developed by radio engineers. This article, which has been prepared exclusively for POPULAR RADIO, reveals for the first time the scientific details of this invention.

By HENRY C. HARRISON

DEVELOPMENT of a new mechan- trical circuits were concerned. It then ical phonograph by electrical en- became possible to design telephone lines gineers working in Bell Telephone of any length so that they would have Laboratories is a natural result of their pre- computed qualities. recent applications of electrical theory In recent years these theoretical to mechanical problems. methods of designing electrical lines Since the inception of the telephone, have been made the basis of theoretical the development work on it has passed methods of designing the vibrating parts through a number of stages. In the of such mechanical systems as telephone pioneer days, the method was neces- receivers and transmitters. sarily that of guess- and -trial, guided by Still more recently, these methods of good judgment and such theory as was design have been applied to the phono- then available. graph. In the field of telephony these many It was recognition of the fact that a experiments led to satisfactory conver- phonograph is a mechanical system for sation over only moderate but constantly transmitting wave energy that led to increasing distances, even as great as the application of electrical wave- trans- between New York and Denver. During mission theory to it. With this method these years, however, the theory of elec- of design, it has been a fairly simple trical transmission was being developed matter to calculate just what require- gradually by various mathematical phys- ments each part of the phonograph must icists. A little more than ten years ago meet, and with these requirements it reached such a stage that the- mathe- known, it has been a matter of com- matical method of design replaced the paratively few experiments to obtain pioneer method of trial so far as elec- nearly perfect reproduction.

3

www.americanradiohistory.com `I POPULAR RADIO

The quality of reproduction given by of the rhythm. At the other end the new phonograph, as compared of the with scale the machine's reproduction of high that of previous construction, is more frequencies readily gives clarity and detail. demonstrated to the ear than They move the "master's described in words. voice" from a Some idea of the position hidden behind the horn improvement, however, may right be formed out into the room. They make all from the fact that a talking the machine instruments in an orchestra stand out that embodies this new principle repro- individually, duces each with its own peculiar five and one -half octaves, whereas quality of tone. the older type reproduces about three On the new phonograph, octaves, and not only is the phonograph of twenty the full range of frequencies years ago something reproduced of the order of one but it is reproduced without perceptible octave. Listening to the machine, one peaks or valleys; that is, hears the low- frequency without the tones as well as regions of exaggerated loudness the high ones. Its reproduction or weak- of these ness in different parts of the frequency low frequencies gives naturalness to range. An example of a peak is speech and music, makes it comfortable what one hears when one speaks with his head to the ear and carries over the full power in a barrel; an example of a valley is

The Newly Discovered Facts About Sound The fundamental thing about radio is the han- dling of wave energy, of vibrations. Two kinds of waves are involved. From the loudspeakers and telephones come the mechanical waves of sound. In the electrical parts of radio instru- ments, as well as in the ether, the wave§ are elec- tromagnetic ones. Many of the principles are the same. In this article Mr. Harrison describes the application of wave -energy principles to the acoustic problem of designing a high -quality phonograph. This involves "mechanical imped- ance," "mechanical transformers," other novel concepts which will interest every radio engi- neer. The research constitutes, POPULAR RADIO believes, one of the greatest recent advances in the science of sound. Facts uncovered by the telephone engineers were put at the disposal of the talking machine interests, whose researches have put them in position where the new tech- nique could be appreciated and applied. Thus radio, often accused of having damaged the phonograph industry, actually contributes one of the greatest advances which that industry has ever made.

www.americanradiohistory.com THE NEW WAVE-TRANSMISSION PHONOGRAPH 5

From a photograph made for POPULAR RADIO by the Bell Laboratories THE INVENTOR OF THE APPARATUS Mr. Henry C. Harrison with the acoustic system of the new orthophonic talking machine. Note how the internal partitions fold the horn so that a greater length can be contained in the case of the instrument.

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THIS CIRCUIT IS THE ELECTRICAL ANALOGUE OF THE NEW ACOUSTIC SYSTEM FIGURE 1: The alternator represents the input from the record; L1 is the mass of the needle arm; L2 that of the spider, and L3 that of the diaphragm. T is a transformer corresponding to the needle -arm leverage; Co the elasticity of the needlepoint, C1 that of the needle arm, C2 that of the spider arms, C3 that of the diaphragm edge and C4 that of the air chamber.

www.americanradiohistory.com 6 POPULAR RADIO

THE CONSTRUCTION OF THE SOUND REPRODUCER FIGURE 2: A section of the sound reproducer, showing the needle and needle -arm, the spider, and the aluminum -alloy diaphragm, the latter being indicated by the bent line. The tube at the right is the inner end of the horn.

The theory used in designing the new phonograph follows very closely the theory for electrical transmission. In electrical systems, the energy is in elec- trical form. In mechanical systems, like the phonograph, the energy is in mechanical form. Mathematical phys- icists have shown that wave -energy formulas what one hears in the voice of a person worked out in one field apply with a bad cold. to the other field with simply a change In scientific language, these changes in in nomenclature. The corresponding quality are expressed as changes in the terms in the two fields are as follows: distribution of sound intensity with fre- Mechanical Electrical quency. From this viewpoint, speech Displacement (total and music are made up of simple flute- movement) Charge Velocity of displacement Current like tones of various pitches and various Force Potential (voltage) intensities. For example, the different Mass Inductance vowels of speech are distinguished Elasticity Reciprocal of capacity from Mechanical resistance each other, not by their fundamental (frictional loss) Resistance frequency, but solely by the distribution of intensity among their overtones. Be- In designing high quality wave trans- cause elements of speech have this mission systems, either electrical or character, one may speak into a barrel mechanical, the important matter is of just the right size and find that when matching impedance throughout the he speaks one vowel a different one is system. heard. A phonograph with the same This means that each part of the sys- peak will make the same change. tem then offers to the wave energy a Similarly, a phonograph with "val- path of equal ease of flow, so that its leys" which rob the reproduction of the flow through the system proceeds without frequency range belonging to the re- any reflection. Thus there are no res- sonant cavities of the head which are onance peaks. Even structures which choked up during a cold makes a singer are apparently so different as needle or speaker sound as though he had a bad arms, diaphragms and horns can be cold. The phonographs of twenty years substantially matched in mechanical im- ago abounded in these peaks and pedance to the wave energy. valleys. The new phonograph is prac- In addition to preventing internal re- tically free from these defects. flection and consequent peaks, matching

www.americanradiohistory.com THE NEW WAVE- TRANSMISSION PHONOGRAPH 7 impedance gives a phonograph a sub- Figures 1 and 2 are sketches of an stantially uniform mechanical resistance. acoustic phonograph and of its mechan- Hence the power taken from the record ical impedance diagram. groove is proportional to the transverse In Figure 1, the same symbols are velocity of the groove squared. And used for mass, elasticity, and mechanical since this full energy is transmitted out resistance as are commonly used in elec- into the air, the result is faithful repro- trical impedance diagrams for induc- duction. The older phonographs are tance, capacity, and electrical resistance.* not matched in impedance. They neither These quantities are corresponding ones take correct amounts of power from the as respects the storage or dissipation of record nor transmit this power to the energy; hence they have corresponding air without reflection and resonance effects on the transmission of wave peaks. In addition to giving faithful energy. The system is shown with its reproduction, the matching of impedance shunt branches working into substan- reduces the wear on the records because tially free space. Actually, the branches the resonance points, with associated work into air, but because of their high pressure of the needle point against small size compared with the wave- eliminated. the record groove, are * In this diagram certain second -order effects are first step in designing a matched omitted for the sake of clearness. The complete diagram As the and a full description of the technical features will impedance phonograph, the diagram of appear in a paper to be presented at the Midwinter Convention of the American Institute of Electrical mechanical impedances is needed. Engineers.

MEASURING THE ELASTICITY OF THE NEEDLE -ARM Mr. Arthur Bates is making one of the fundamental measurements upon which the phono- gr-iph design depends. In mechanical wave systems elasticity is the equivalent of the re- ciprocal of capadity in electrical systems.

www.americanradiohistory.com 8 POPULAR RADIU

PIONEERS IN THE APPLICATION OF 2\ 1ATHEMArTCS TO THE PHONOGRAPH Mr. Harrison tut the left) is ho /din the sound reproducer Joseph P. which he is explaining to Mr. Maxfield, who developed the e.'ectri(ul methods by which high quality made for use ..'ith the records are ne«' machine. ln the foreground lies one of the aluminum -alloy dia- phragms.

lengths in air of speech frequencies, the have the same kinetic energy as the part. air acts like free space. In a mechanical Similarly, by the "elasticity" of a part system free space is analogous to an in- is meant the elasticity in dynes per finite capacity, or "ground," in an elec- centimeter which, trical located at the point system. of attachment, would The shunt store the same branches of the line are potential energy as the part. ones through which vibration velocity, It is evident from these diagrams that is, the mechanical that current, flows the first three sections of from the main line this network to space. The series constitute a transmission system elements in the line of the are ones through low -pass filter type and hence which all of the line mechanical will have current a high frequency cut -off. The series must pass. The symbol used for a elasticity, due to the diaphragm edge, mechanical transformer is the one usu- does not belong in a low -pass filter and ally used in electrical circuits and indi- interferes cates with the transmission of the merely a change in displacement lower voice frequencies velocities at this point. unless very small. The principles and formulas that The term "mechanical current" is govern transmission used as meaning networks such as the root mean square this one are worked of vibration velocity out for analogous in centimeters per electrical lines by J. second. The term "alternating A. Fleming, A. E. force" is Kennelly, and George A. Campbell. used as meaning the root mean square of Building forces, upon the foundation these in dynes, tending to set up or vary scientists have mechanical currents. laid, the telephone en- By the "mass of gineers were able to treat a part" is meant the mass the design of in grams an acoustic phonograph as an engineering which, located at the point at which the problem. Certain results were desired, part ties into the mechanical line, would certain limitations had to be met as to

www.americanradiohistory.com THE NEW WAVE -TRANSMISSION PHONOGRAPH `3 materials and dimensions, and certain of mechanical impedances over a range other factors might be varied practically of frequencies. at will. Calculations were made for the Thus it was possible for the mechanical various parts, and these were chéckéd by impedances of the 'different parts of the measurements of the characteristics of system to be carefully matched, just as the parts as vibrating elements. Here should be done to the electrical wa ve- an entirely new technique was developed, erìergy circuits used in telephony or in as for instance the direct measurement the parts of radio apparatus.

From a photograph made for POPULAR RADIO by Victor Talkin Machine Co. THE COMPLETED MACHINE In. the small diagram at the right is shown the arrangement of the gradually widening passages through which the sound waves travel. Note the great length (70 inches) of the new horn, as compared with the older and more familiar types. Above, Reinald Werrenrath, thè grand opera singer, is seen listening to a record of his own voice on one of the first machines to be completed.

IN POPULAR RADIO for next month- February-will appear the complete, detailed specifications for building one of the latest and 41 most efficient sets that have been developed -the Orthophase Receiver.

www.americanradiohistory.com HOW TO GET THE MUST By S. GORDON TAYLOR and L. M. COCKADAY

SO great has been the interest shown To test the capacities of this receiver on the part of readers of POPULAR the authors have taken it to a number of RADIO, and so keen has been the com- cities in the East and experimented with petition among radio fans and experi- actual receiving conditions for the pur- menters to be one of the first to build one pose of telling experimenters of the new LC who have -26 receivers and to get built this set exactly what to it in operation, do when that this article -which they install and operate it. takes the place of the "How to Get the First of all, let us start Most with a general Out of Your Ready -made Receiver" description of the receiver. article that would ordinarily appear in It uses a simple antenna circuit that this issue -follows by popular is demand. easily resonated over the whole band of 10

www.americanradiohistory.com OUT of YOUR LC-26 SET

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--TO /IO VOLT /1C L/6/;ir SOceCT CHECK UP YOUR INSTALLATION WITH THIS DIAGRAM FIGURE l: Pictured here are shown the rear view of the LC -26 Receiver, the (one loud- speaker, the filter unit, the three large "B" batteries, the small "B" battery, the charger, the charging switch and the storage battery. The connections between these units are shown in heavy lines to the exact binding posts and terminals that they should run to including the antenna and ground connections. If you use this simple diagram when installing your set you will find that it will give you perfect satisfaction. 11

www.americanradiohistory.com 12 POPULAR RADIO

broadcast wavelengths. This circuit is radio- frequency tube and coupled looser similar to that used in the old variometer- to the detector circuit, thus allowing re- tuned sets. What was a disadvantage in generation in the detector but preventing the old sets is, however, a great advantage oscillation in the radio -frequency stage. in this receiver. The tuning of this par- This is a much more simple method than ticular circuit is extremely broad. This the usual compensating condenser or neu- leaves the sharply -tuned trap circuit, tralizing scheme, as it is almost impos- which is the input to the detector, to do sible to properly neutralize a single stage the actual sharp selecting that is neces- radio - frequency amplifier throughout the sary to tune out local stations and bring whole wavelength band when used with in the distant ones. Therefore, the re- a regenerative detector. ceiver may be considered as essentially The audio - frequency amplification has a single -control device (in the case of been the subject of much experiment and local reception) as the input tuning accom- has been chosen for its straight- line -f re- plished by the variometer has very little quency amplification and particularly at effect. It may be used as a sort of vol- the low frequencies, so that the drum and ume control. For distance, however, it bass viol tones are brought out with helps considerably. The receiver cannot startling clarity. radiate on account of the use of the stage If the receiver is installed and operated of non- oscillating radio - frequency am- as described in this article it will bring to plification used ahead of the detector. the experimental listeners a new thrill Both circuits are controlled by the stabil- from broadcasting that comes from recep- izer (or intermediate circuit) which is tion of this broadcasting as it is really coupled closely to the plate circuit of the being transmitted.

/NSUL ATJRS . fiNTfNNA WIRE *' \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

WAL L OFHoasE \ ANTENNA CONNECT/ON LEAD- /N Whet - TO/et-CC/1R PORGELA/N POLE Oe OTHER BU5N/N6i ANTENNA SUPPORT

L/6HTN /N6IIRRESTOR

1 COLOWATERP/PE 6J//NO CONNECT; To,PECE/vER

OUTS/OE 6RJUNP CONNECT/ON --

AN EXCELLENT ANTENNA ARRANGEMENT FIGURE 2: The design of the antenna is necessarily governed, in most cases, by yard space available. the roof or However, many of the ideas suggested by this illustration may be used to advantage in any antenna installation. The best length for the antenna will depend in each case on the interference conditions.

www.americanradiohistory.com THE LC -26 RECEIVER i î

To'? "BA T TE P Y CONNECT/ O N5 OF RECOVER

HOUSECURRENTiIJPPLY-O /KECT CURRENT -01° ;q "BATTEiE'Y

/OO14/ATT TU/Y65TENLAMP5, OR Q 0 32CA/YPL EPOWER CAAWONL9MP5 (1 (4 CONNECTIONS FOR CHARGING "A" BATTERY FROM DC HOUSE SUPPLY current. FIGURE 3: The type of battery charger used depends on the, kind of house supply current, a regular AC charger is used. If the house supply is direct If it is alternating pre- current, however, a simple arrangement of electric lamps is used as shown here. If ferred a DC battery charging resistance may be used instead of the lamps. Theory of Operation coil B which is in series with the plate and The "B" battery. Coil C is closely coupled to this The antenna circuit of the LC -26 receiver is coil B, so closely that it absorbs much of the tuned to resonance with the incoming signal energy from the plate circuit of the first tube, from a broadcasting station by means of the thus preventing oscillation in the radio -fre- variometer A. (See diagram, pages 496 -7 of quency amplifier. Coil C with its tuning con- the December issue of POPULAR RADIO.) The denser E therefore serves as an absorption cir- fixed condenser G simply serves to adapt the cuit or stabilizer. The fact that the first ttihe receiver to the size of antenna used. This cannot oscillate prevents the receiver from method of tuning the antenna circuit is prob- radiating energy into the antenna system, a ably the most efficient known because of the condition which would cause annoyance to preponderance of inductance obtained in the cir- neighboring receivers. cuit in this way. The energy absorbed by the stabilizer circuit It will be noted that the variometer is also in is not lost, however, as this circuit is in series the grid or input circuit of the radio -frequency with the coil D and its tuning condenser F. amplifier tube. Thus the variometer serves not Both of these coils are in the grid circuit of the only to tune the antenna but only as an auto - detector tube Q2 ; therefore the energy absorbed transformer to transfer the antenna energy to from coil B is usefully transferred to the input the radio -frequency amplifier, the voltage drop of the second tube. In this circuit there is across the variometer being impressed across again a preponderance of inductance, consisting the grid -filament circuit of the tube. of the inductance of coil C plus that of coil B. For a small amount of energy impressed upon The use of so much inductance is made possible the grid of a vacuum tube a comparatively large by the fact that the two tuning condensers E amount of energy may be made to flow in the and F are connected in series ; therefore their plate circuit of the tube, due to the amplifying total capacity is only half that of either one action of the tube. This additional energy is not alone. Inasmuch as the frequency or wave- generated in the tube itself but is drawn from length of the circuit is governed by the product the high -voltage "B" battery which is connected of the capacity and inductance, it naturally fol- in the plate circuit of the tube. In other words, lows that the use of such small capacity calls the energy in the output circuit of the tube is for the use of large inductance. The stabilizer drawn from the "B" battery but the amount is tuned to a lower wavelength than the total drawn is regulated by the throttle action of the grid circuit. This use of a double condenser is grid circuit of the tube. not therefore the same as that of tuning two The energy in the plate circuit of the radio - stages of radio simultaneously. In this cage frequency amplifier tube Q1 flows through the it is a regeneration control. The energy input

www.americanradiohistory.com 14 POPULAR RADIO

to the detector tube is not only amplified by this flow in the secondary winding of this trans - tube, but it is rectified. Up to this point in the former by the process of electromagnetic induc- circuit all the energy has been in the forni of tion. The use of inductive coupling, as fur - alternating current of high frequency. The nished by the transformer, is necessary here to output of the detector tube, however, consists isolate the grid of the audio-amplifier tube from of pulsating direct current which really amounts the high voltage of the "B" battery in the de- to direct current with an a'ternating current tector plate circuit. By means of the secondary component. Both kinds of current are there - winding the energy is impressed on thegrid of fore present in the plate circuit of this tube. the tube Q3 and the amplified energy is taken The audio- frequency component of this en- out at the plate of this tube. The use of one orgy is lead through the primary of the audio stage of transformer- coupled, audio- frequency frequency amplifying transformer J, but the amplification produces high amplification radio- frequency current passes with difficulty. (through the voltage step-up action of the through the high inductance such as that of transformer) of excellent quality. this primary winding. \lor-eover, this radio- The LC -26 receiver makes use of resistance frequency component serves no useful purpose coupling in the second and third audio- frequency in the audio frequency amplifier. It could be amplifier stages. This type of coupling does not used to advantage, however, if fed hark to the produce such great amplification per stage, but input side of the detector tube because then it the reproduction is flawless over the whole would be amplified again by the amplifier action range of audible frequencies. In addition to of the tube. This is exactly what is done. A this, the current consumption from the "B" bat - wire is connected from the plate of the de- teries is much lower with resistance -coupled tector tube back to the coil C in the detector amplification than with "unbiased" transformer - input circuit. This produces the regenerative coupled amplification. action and results in the detector tube practi- There is no particular point in providing cally serving the purpose of two tubes, one use variable adjustment of filament heating voltage being a radio- frequency amplifier and the other for any of the tubes except the detector. For use a detector. this reason the automatic filament control re- Regeneration can only be obtained up to cer- sistances 01 02, 03 and 04 are used with the fain limits, of course. Carried beyond certain other tubes, and a rheostat is provided on the limits, the detector tube would break into oscil- Panel only for control of detector Filament cur - lation, thus distorting the signals. In most re- rent. generative receivers this is the practical limit The Antenna and the Ground to which regeneration may be carried. In the The antenna requirements of the LC -26 re- LC-26 receiver, however, it can be carried far ceiver are not at all beyond critical and for that reason this point because oscillation will stop satisfactory results may be when the radio -frequency obtain( 1 with the circuit is tuned to use of almost any kind of a wire strung up resonance with the input circuit to the detector wherever it is convenient. tube, as is the case when both circuits are tuned As an example of to a broadcasting, just how great the sensi- station's wavelength, and sig- tivity of this set is, plenty of volume pals will be heard clearly and from is obtained undistorted. all the New York City and nearby sta- This explains why this receiver tvith its five tions when operating the receiver in tubes gives the suburbs the results of a six-tube rrceivr,. of the city approximately twelve miles from the without any of the trouble usually encountered nearest station, without using any ill neutralizing antenna at such a receiver. all, by simply connecting the ground lead to the For ordinary reception it is not antenna binding post on the receiver, necessary to the ground with have detector oscillating. For longc disrynto binding post left disconnected. work, however, an oscillating condition of the It is, however, in general use advisable to detector tube makes the tuning of the receiver employ some sort of an antenna. As matter extremely simple, because it is of fact, where an outdoor and also merely neces- antenna an indoor sera to turn the large tuning- dial until a carrie r can conveniently be erected, it is worth - wave whistle is heard, then adjust the varier while to put up both. This is suggested be- meter knob until, when it reaches resonance cause during the summertime, when the is troublesome, static the detector circuit, oscillation will arid_ the indoor antenna can be used, withwith stop and thus eliminating the circuitsdistant station sci ll willion heard.- much of this form of inter - The amountsand df regenerative be can ference. During the cooler months when there be obtained by adjustment of the is better reception weather, the detector rheo- tenna outdoor ari- stat, P. The pulsating direct -current output of may be used. (Incident.11y, this sug- the detector is audible if a pair of headphones gestion applies not only to this receiver but is connected all receivers to in the circuit. From this point on which are sufficiently sensitive to in the circuit another t ape of operate satisfactorily on an indoor amplification is The antenna.) used. The purpose of the radio- frequency am- outdoor antenna has the advantage of plifìer was to build greater "pick -up" and up the alternating current (erred is there ore to be re- (radio- frequency) energy, when it is desired to tune in thus increasing the tions. distant sta- sensitivity of the receiver. The purpose An outdoor antenna consisting of the of single copper a audio- frequency amplification used after the wire somewhere between 60 and detector is to build up volume 100 feet, is amply large for this receiver. so as to make is Little possible the use of a loudspeaker. to be gained by making the antenna longer than 100 feet, The energy flowing through the primary but it is not advisable to have the audio of it less than 60 feet or thereabouts transformer J sets up a corresponding the because òf decreased "pick-up." These lengths include

www.americanradiohistory.com THE LC -26 RECEIVER 15 A Tuning Chart to Adjust to Your Own Set

WAVELENGTH 0/AL SETT/NG ME re Rs

5 FIGURE 4: 200 Cut out the chart at the left and paste it on a piece of thin stiff /0 white bristol paper. Then cut out the small chart at the right.

It should be pasted . in position on the blank /5 250 space on the left -hand side of the main chart underneath the head- 20 ing "wavelength" as shown in the Decem- ber issue on page 504. To get it in exactly 25 the right position tune 300 in a station of around 350 to 400 meters and find out what setting 30 it comes in on on your dial. For instance, a station on 405 meters `J 35 would come in some- 350 where near 46, 47 or h 48 on your dial ac- i. 40 cording to the varia- -t tion of the condenser ti in the set. If it comes 45 in at 47, say, paste the i wavelength part of the 400 chart in place so that 50 405 meters on the Lk, wavelength scale is `;".' 55 exactly opposite 47 on the dial setting scale. . Then all the other 60 stations will tune in '.Q exactly as indicated by 65 450 the completed chart.

70 75

80 500 85 90 95 /00 550

.

www.americanradiohistory.com 16 POPULAR RADIO

the entire length of the wire, from the antenna vanized iron guy wire of about No. 12 size is binding post on the receiver to the end must good for this use because of its strength. distant from the receiver. A good ground connection is also important. It is impossible to give exact instructions for I f the house is provided with a cold .. vater.. sup- erecting an outdoor antenna because practically ply, the ground wire may be fastened tò the every installation has its own peculiar condi- water pipe nearest the receiver by means of a tions and requirements. However, in Figure 2 ground clamp. Hot water pipes will also serve is illustrated an ideal antenna. Some of the in a pinch, but do not ground the receiver to ideas suggested in this illustration may be used a gas pipe ; this is against the rules of both the in all installations. The matter of insulation gas companies and of the Board of Fire Under- of the antenna and "lead in," for instance, may writers, and in addition is usually a poor ground

be used in almost every case. - Some general because of the insulating gaskets frequently in- suggestions for this may be offered: For in- stalled in the pipe line where it enters the stance, it is not advisable to have the antenna house. wire close to trees or buildings, but especially The Batteries trees. A distance of ten feet should be the minimum spacing from the latter obstacles. A 6 -volt storage "A" battery is required for 1 f necessary to use a tree to support the further lighting the filaments of the vacuum tubes and end of the wire, be sure that the insulator is for the high voltage plate supply a set of "B" placed at least ten feet from the foliage. In batteries of 157/ volts is used. such a case precautions must be taken to prevent The "A" battery should be one of not less the wire from being broken by the swaying of than 100 -ampere -hour capacity and should, of the tree in the wind. This is most easily accom- course, be one designed for radio use. When plished by running the wire through a pulley the receiver is in operation the current drain on fastened to the tree and suspending a weight on this battery is approximately 2% amperes -per- the free end of the wire, making ample allow- hour and a fully charged 100 -ampere -hour bat ance for the free play of the wire. tery will operate the receiver for about forfy The kind of wire used is not particularly im- hours without recharging. Batteries with portant so long as the wire is copper. It may greater capacity will, of course, operate the be plain wire not smaller than No. 14. Or it receiver a longer time on a single charge. may be the regular seven- strand aerial wire. A hydrometer shouldbe used to measure the Make the antenna proper and the lead -in all state of charge of the battery. This instru- one piece if this is possible. I f this cannot be ment measures the specific gravity of the elec- done solder the joint where they come together, trolyte in the battery and is equipped with a thus insuring a good electrical connection. scale which reads from 1,150 for a discharged The height of the antenna is important only battery to 1,300 when the battery is fully tip to a certain point. It is, of course, well to charged. The battery should never be allowed make it as high as conditions will permit. Put to run down to such an extent that the reading it as high as you can, but try to get it higher falls below 1,185. Many make a practice of re- than surrounding objects if that is possible. charging the battery when the reading falls to If the antenna is erected on the roof of an 1,200, and this is a good practice. apartment house which is already occupied by The "B" battery consumption of the LC -26 a number of other antennas, try to put it above receiver is lower than that of most five -tube re- and at a right angle to the others and see that ceivers, in spite of the fact that the voltage used it is clear of the pent houses and vent pipes. is somewhat higher than usual. In ordinary I f it is necessary to erect pules un the roof, use the dry -cell type of "B" batteries is there - don't be satisfied to tie the poles to vent pipes; fore entirely practicable. Using the full voltage drill a hole part way through a heavy wood specified above and with the receiver operating block, set the block on the roof (it need not be an average of two hours day, fastened down), a a set of the or- erect the pole with its base dinary large size "B" batteries will have a life resting in the hole in the block and then guy the of between five and six months. Dole with at least three wires. The other ends Using the "heavy duty" type of the guy of batteries the wires may be secured to bolts in the life will be increased to approximately ten walls, or to the bases of other vent pipes. Gal- months under the same conditions. The life

Hours of use daily 2 3 4 Large size batteries 166 days Heavy 105 days 72 days duty batteries ... 297 days 190 days 134 days

THE LIFE OF THE BATTERIES This table shows the approximate life of a set of "B" batteries with the LC -26 receiver. It will be noted that the "heavy duty" type of batteries give the service almost double of the usual "large" (five pound) type, although the cost of them is only about 50 percent greater. The above figures are based on the use of the total voltage specified (namely, 157% volts), but takes into consideration voltage the normal drop in as the batteries wear down. When the batteries drop from 45 volts each to 34 volts they are worn out and should be replaced.

www.americanradiohistory.com THE LC -26 RECEIVER 17

From a photograph made for POPULAR RADIO THE LC -26 INSTALLED WITH THE RAYTHEON PLATE -SUPPLY UNIT FIGURE 5: This picture shows the receiver working without "B" batteries. The Raytheon unit as described in the November issue of POPULAR RADIO may be seen on the shelf of the table with the cone loudspeaker at the right. of these two types of batteries under various to both the radio and audio- frequency amplifier conditions are shown in the table on page 16 tubes of the receiver. The connections are The use of the "heavy duty" type of batteries shown in Figure 1. Using such high voltage is recommended where dry -cell batteries are on the radio - frequency amplifier tubes would used because their increased life is greater than not prove satisfactory with most receivers be- their increase in cost over the usual "large" cause of the tendency of this portion of the cir- size batteries ; they are therefore cheaper in cuit to oscillate. In the case of the LC -26 re- the end. ceiver, however, the radio -frequency stage will If the receiver is to be used on an average not oscillate, regardless of the voltage applied. of more than two hours a day the use of stor- The detector "B" + post on the receiver is con- age "B" batteries is recommended. The first nected to the post on the Raytheon Unit bearing cost of such battery equipment is considerably the sanie designation. The knob of the variable higher than that of dry cells, of course, but the resistance in the Raytheon Unit is then adjusted first cost is about the only cost for perhaps sev- to a position where signal strength is greatest. eral years, as the cost of recharging the bat- This will 'provide the detector tube with the teries is so small as to be insignificant. proper plate voltage. The position of the knob In place of "B" batteries the Raytheon Plate will be almost all the way out. Supply Unit (described in the November issue) An "A" battery charger to operate from the may be used with results equal to those obtained electric house lighting line will be needed unless with either the dry -cell or storage "B" batteries. the owner wishes to go to the trouble of taking This unit has several advantages. There is his storage battery to a service station to be nothing to wear out and require replacement, charged. Some manufacturers are placing units as in the case of dry -cell "B" batteries, and on the market which consist of a storage "A" recharging is not required as in the case of battery and charger combined to operate from storage "B" batteries. In addition, this unit the alternating current house line and which takes up. less room than do batteries of either operate automatically so that no attention is type and the first cost is no greater than that required other than the occasional addition of of the storage type of "B" batteries. distilled water to make up for evaporation. In using the Raytheon unit with this receiver, There are also several types of alternating cur- the total output voltage of the unit is applied rent chargers on the market. When the charger

www.americanradiohistory.com 18 POPULAR RADIO

and battery are separate, a five- ampere charger the detector circuit and this circuit has been de- is recommended, and the particular type selected signed with the UV -200 type of tube in mind. will depend on the purchaser's judgment. The Other tubes will not provide the same sensi- . three main considerations in the case of a tiveness, nor as good tone quality. charger to operate on AC are constancy of For the radio- frequency amplifier a UV -201 -a operation, noiselessness and necessity for re- type of tube is used, as also in the first and placement of parts. The first two points may second stages of audio -frequency amplification. be determined by requesting a demonstration That is, the first, third and fourth sockets from before purchasing. In general the type of the left -hand end of the receiver, the detector chargers using a rectifier tube are to be pre- socket being the second. ferred as they require no adjustment, are fool- In the last socket, which is in the third stage proof and most nearly noiseless. of audio- frequency amplification a power tube When storage "B" batteries are used, some is used because the usual types of tubes such means must be provided for charging them. as the UV -201 -a cannot handle the great vol- "A" battery chargers may be obtained which ume in this stage. The set is designed to use Nvill also charge the "B" batteries, or attach- a Radio Corporation UX-112 power tube in the ments may be purchased to use in conjunction last stage with a No. 112 amperite to control with "A" battery chargers when it is desired the filament current. A UV -201 -a tube can to charge the "B" batteries. Then, of course, be used but will not produce the maximum in separate "B" battery chargers are on the mar- tone quality or volume but if it is used an am- ket and at comparatively low cost. perite cartridge of suitable resistance must be In Figure 1 will be found a convenient used with it. Builders of this receiver who method for connecting up the "A" battery happen to have a Western Electric VT -2 ór charger in such a way- that it is only necessary 216 -A tube on hand can use it in this:last stage. to throw the switches to put the battery on In that case a No. 1 amperite should be used.' charge. The use of UV -199, WD -12 or any other óf When the house- lighting supply is direct cur- the dry cell tubes in this circuit is not advised. rent, only a charging resistance is needed. This may he a bank of live 100 -watt lamps connected Tite Operation of the Receiver in parallel as shown in Figure 3. The connections to antenna, ground and bat- The Tubes to Use teries are clearly shown in Figure 1. Before making these connections, place the The UV -200 or C -300 tube has been found five vacuum tubes in their respective sockets. best for the detector tube in this receiver. The Starting with the first socket at the left, the extreme sensitiveness of this receiver is due tubes to be used are : UV- 201 -a, UV -200, UV- largely to the employment of regeneration in 201-a, UV -201 -a and UN -112. Now connect the

From a photograph made for POPULAR RADIO AN ALL -NIGHT SESSION IN CALIBRATING THE RECEIVER FIGURE 6: The authors are here shown obtaining the data on an Mr. Taylor's LC -26 installation at home laboratory, for the purpose of making up the tuning chart shown in Figure 4.

www.americanradiohistory.com THE LC -26 RECEIVER 19

From a photograph made for POPULAR RADIO AN LC -26 INSTALLATION WITH DRY ('ELL "B" BATTERIES AND A STORAGE "A" BATTERY FIGURE 7: An ideal installation of the receiver, with the batteries placed in a radio cabinet. The wire shown running from the upper right -hand corner of the set along up the wall is an extension cord to the cone loudspeaker which is placed on the other side of the room.

" " battery with its negative side to binding Next rotate the small left -hand knob until the post No. 3 and its positive side to binding post station is heard with nmaxinium volume. The No. 4. To be sure that the filament circuits switch R1 should be turned to the left for an are all intact, turn the battery switch on the outdoor antenna and to the right for the in- front of the receiver to the "on" position. All door antenna. As explained before, the pur- but the second tube should light up. Next pose of this switch is to adapt the antenna cire turn the small right -hand knob half way on, in cuit constants to the antenna in use. a clockwise direcion. This should light the de- Now that a station is tuned in, try different tector -tube filament. settings of the detector rheostat (the small If all of the tubes light up properly, remove right -hand knob on the panel front). One point all but the first and connect the "B" batteries will be found at which signals have the de- as shown in Figure 1. The four tubes should sired strength and clarity. This is the proper be removed first to avoid the possibility of burn- setting. The point of maximum reception, how- ing them out in case anything goes wrong in ever, will not be the same on nearby stations, the wiring which might permit the "B" battery as on distant stations, the latter repairing that voltage to be applied to the filaments. In such the rheostat knob be turned further in a clock- a case the single tube left in the set would light wise direction. Do not tune in stations with up very bright. I f everything is right up to more volume than is enjoyable. this point, connect the antenna and ground to After tuning in several local stations, and the receiver, replace the other four tubes, and becoming somewhat familiar with the opera- insert the loudspeaker plug in the jack S. tion of the receiver, try a more distant station. Signals from a broadcasting station can now Set the large dial for the station you wish to be tuned in. The tuning dial should be set tune in, then slowly rotate the left -hand knob for the station desired, the proper setting being tortil the station is picked up. When the station ol,tained from the tuning chart in Figure 4. is heard, adjust the tuning dial and the two

www.americanradiohistory.com POPULAR RADIO

S

r

t'

k

A REVISED DIAGRAM OF THE SHUNT -PLATE FEED UNIT P FIGURE 8: This is used to keep the direct current of the plate supply out of the loudspeaker, tt allowing only the alternating current of audible frequencies to pass through the loudspeaker.

www.americanradiohistory.com THE LC -26 RECEIVER 21

small knobs until suitable volume is obtained. Installation and Equipment Now the proper adjustment for the grid -leak I may be made. For the assistance of those who are contem- With the distant signals tuned in rotate the plating the installation of an LC -26 receiver, knob of I until the signals are at the maximum. brief descriptions of the installations in the It is best to move this knob a little at a time, homes of three of the members of the POPULAR and to remove your hand from the receiver RADIO organization are given below, with illus- while the effect of the change is being noted, trations. otherwise the presence of the hand on the grid- In all three cases the cone -type of loud - leak may have a slight detuning effect. The peaker is used. In one of the illustrations proper setting of the grid -leak will usually be the loudspeaker does not show, as it is sus- found to be with the knob screwed a little to the pended in a doorway between two rooms with right of the point where a clicking or rattling the object of keeping it as far from walls and sound is heard as the knob is rotated. Once other obstacles as possible, thus eliminating a the proper setting of this instrument has been certain amount of harshness which is present found it may be left indefinitely at that setting. when any loudspeaker is so placed that emitted The stunt sounds of large volume strike a flat, unbroken last to be tried is to change the three surface -a such as that of a bare wall, at close UV -201 tubes around until the best position range. for each is found. One of the three may be In two of the illustrations found to function better than the it will be noted other two that the receivers are placed as a radio - frequency amplifier tube (in close to the win- the left - dow where the antenna lead -in hand socket). Leave the tubes in the sockets wire is brought into the house. This aids the general efficiency in which the combination is found to be best. of the antenna. The ground leads in each case It is extremely easy to tune in distant sta- are kept as short as practicable also. tions if the heterodyne beat method is used. The diagrams given of these three installa- This is accomplished by turning the rheostat tions will show some differences in the (knob current far enough in a clockwise direction to supply for the receivers. In the photo and cause a hissing sound in the loudspeaker, in- diagram, Figure 5, for instance, dicating the high - that the detector circuit is in an os- voltage plate supply is obtained from the cillating condition. The tuning dial is then Raytheon Plate Supply Unit, which may he rotated until the whistle of a carrier wave is seen on the shelf under the table. A heard. con- Leaving the tuning dial set at this point structional description of this unit was given the left -hand small knob may be rotated until in the November issue. The filament supply in the whistle suddenly stops and at this point the this case is obtained from a six -volt storage speech of music from the station will be heard, battery. In Figure 7 the plate supply is from somewhat distorted. The distortion can be regular dry -cell type of "B" batteries. The cleared up by turning the rheostat knob back filaments are supplied by a combination storage (anti -clockwise). The tuning dial and the two "A" battery and charger (Gould Uni- Power). small knobs should then be slightly readjusted In Figure 6 storage "B" batteries are used to bring the station up to maximum volume. to provide the plate supply. A glimpse of When looking these for distant low -wave stations, may be had on the shelf under the table. The eep the left -hand small knob turned with the filaments are supplied by a six -volt storage bat- rrow in a horizontal position and pointing to tery installed with a charger and switching ar- he left. For high -wave stations the left -hand rangement so that in order to charge the bat- mall knob may be turned further in a clock - tery it is only necessary to throw the switch to ise direction. With a few minutes practice the "charge" side. ne can become proficient in this method of In the case of Figure using. 8 there is one piece of equipment used which does not show in the When this method of tuning is used with th- picture but is found helpful in producing the oudspeaker connected to the set the whistle of utmost in tone quality; it is a shunt -plate unit he carrier waves will, of course, be audible connected between the loudspeaker and the set, o listeners who may be in the room with it. the purpose of which is to keep the direct cur- rent from the batteries Do not be afraid of using this method as out of the loudspeaker windings, where it serves he receiver cannot radiate. So far as inter - no useful purpose, but to permit the erence with neighboring receivers is concerned, full modulated current of the signals to pass here need be no worry; even through the windings. In ad- when using the dition to eterodyne method of tuning the first improving the tone, this device pre- tube does vents any demagnetizing of oscillate, therefore the whistles are con - effect the direct -cur- rent flow might have ìned to the detector circuit and do not get to on the magnets of the he antenna where loudspeaker. This unit is somewhat similar to they might cause trouble to that he neighbors who have receivers. described on page 556 of the December is- sue. Slight changes in the To turn off the connections as receiver it is only necessary to shown there were made in adapting it hrow the switch R2 to the off position. to the This LC -26 receiver, however. The diagram of the reaks the "A" battery circuit and automatically filter, as used with the urns LC -26 receiver, is shown off the "B" batteries. If the "Raytheon below in Figure 8. late Supply Unit" is used instead of "B" bat - We are glad to give definite assurance ries, it be that will also necessary to withdraw the this receiver cannot, under any condition, lug in the line which supplies the house- radi- light- ate energy into the antenna circuit. It is truly g current to the Raytheon unit. a "golden rule" receiver.

www.americanradiohistory.com "RADIO M \V METROPOLITANIZE THE RURAL DISTRICTS" ". i but radio is destined to have a marked effect upon two widely different types f newspapers -the large metropolitan dailies an one hand and the smáll town newspapers on the other -is the conclusion of the author of this article. He is'the publisher of LE PEilt PAR1sIEN, and one of the best -known journalists of Frañce. Will Radio Kill the Small Newspapers?

Iii SENATOR PAUL DUPUY

ALÀ Rc; E grotty of newspaper owners, who have had the nerve to broadcast plays publishers and editors have decided or parts of plays report that the broad -i that radio is a serious menace to the news- casts increased the box office receipts.' paper world. And certainly there have been no reports Similar antagonism has been caused by of bankruptcy or of loss of circulation' former innovations. When the first pho- from those newspapers that have ,erected nographs appeared, theatrical people fore- broadcasting stations even though they cast the death of opera and concerts. They put upon the air some of the same news were wrong ; the phonographs helped mu- that later appears in their columns. sical productions. .The first movies were There is one possibility that may be re- denounced as an agent that would destroy garded as a danger. By the use of radio the legitimate drama. Yet today the stage we may eventually metropolitanize the thrives as never before and the prosperity rural districts and smaller towns. Their of the cinema is proverbial. interests may become identical with the Now it is radio's turn to receive the at- interests of the big communities. This tention of the gloom dispensers. Just as possibly will menace the life of the coun- labor has objected to each new mechanical try newspaper. device, so the stage, the screen, the 'Press It may be that the rural resident will, are wailing over the "ruin" to he visited eventually, prefer to read the suburban upon them by radio. Yet theater managers edition of the big daily, as he will there 22

www.americanradiohistory.com WILL RADIO KILL THE SMALL NEWSPAPERS? 23 get a wider scope of information about the and the diplomats but also by the man events of which he heard by radio the in the street. night before. In that day the little local paper will be But even this may prove less a matter of of such slight interest that it will die a regret than we should at first think. After natural death, unmourned even by its all, the individual is rapidly sinking into owner. Radio will have been more di- unimportance, and the community or the rectly responsible for this change than state is becoming the unit of human any one other element of our complex thought. As the world shrinks, as it is civilization. - It is one possibility of the made smaller by rapid means of communi- effect of radio on the publisher. The time cation, by ships, trains, airplanes, tele- may be coming when, because of radio, phones, telegraph and radio, the nation the big metropolitan dailies will have a may also gradually become secondary and greater rural influence and, as a corollary, the world will be one great unit, recog- some of the small local papers will be nized as such not only by the statesmen gradually killed off.

Pacific & Atlantic THE NEW UNDER -WATER TRANSMITTER To enable the crews of submarines to converse with each other while their vessels are submerged, the Navy Department has developed this special apparatus.

www.americanradiohistory.com TIt )W NATURE ARRANGES MOLECULES 7'l/is tvooden model illustrates the common pattern in which molecu.es are ar- ranged. Each atom resembles a wooden shoe; four shoes closely packed form a unit of structure that is repeated again and again. The ATOM

The Nature of Crystal's

Tremendous power is believed to lie within the minute and constantly moving particles of matter known as atoms. The entire universe, the scientists tell us, is made up of only',ninety different kinds of atoms. One of these -the thorium atom -furnishes the activating power for modern vacuum -tube filaments as used in modern radio transmission and reception; this is one instance in which the energy that lies within the atom has been harnessed. To extract the energy from atoms and to make it of service to civilization is one of the most important problems that now comes before the experimenters in science. By SIR WILLIAM BRAGG, K.B.E., D.Sc., F.R.S., M.R.I.

have seen that when the effects from its position. It is, let us say, tied WEof heat motion sufficiently over- to the next molecule at more than one power the forces of mutual attraction point, _so that the whole structure is between the molecules, the latter may rigid or solid; fastened together as the have an independent existence and form various parts of a bridge are riveted a gas; and, further, that when the together in a firm whole. forces have gained somewhat the upper The persistent tendency to form a hand the molecules may cling together crystal is very mysterious. Given time and still retain a considerable freedom enough, Nature will always succeed in of motion; the substance is then a arranging the molecules according to liquid. a pattern, and, -in general, a very simple We have now to consider a final stage pattern (Figure 1). The molecules may in which the molecules are so locked lie for a time in a higgledy- piggledy way, together that no molecule can move tied together so strongly that the sub- 24

www.americanradiohistory.com THE ATOM 25 stance behaves more or less like a may contain a regular arrangement of solid; this is the case in glass. But trees. The plan of an orchard may, of the molecules are always trying to course, be drawn on a piece of paper, creep into their places in a regular while the plan of a crystal could only be scheme, and often succeed in time. fully set out in space of three dimensions, Is every solid body a crystal therefore? but the analogy is sufficient. Our The answer to the question is that it object is to find out the plan. When tries to be, and is in general far more we stand in a regular planted orchard successful than usually appears. Some or hop -field, we see rows of trees and things are obviously crystalline, such as alleys between them running away quartz or, as it is sometimes called, from us in many directions. In a rock crystal. Krustallos is the Greek crystal there are lines of the pattern for both quartz and ice. Other sub- units running away in all directions stances are less obviously of crystal from any one of them; and, further, form. Such are thé metals which usu- many planes can be drawn through any ally show no regularity of outer form, one of these lines, each of which will be but do so under certain circumstances; studded with the units in regular fashion. in all cases, the crystalline structure Now, if we were told that in a certain can be proved by the use of X -rays. orchard there were alleys 12 feet wide And again, there are many cases where that ran in a north and south direc- X -rays alone can show the crystalline tion, and other alleys of other widths structure which otherwise would be that ran in other directions, we should overlooked, as, for example, in a film have enough knowledge to enable us of paraffin wax melted on to a plate. to make a plan of the orchard showing

I One or two experimental illustra- the positions of the trees. In the same tions of the process of crystallization way, if we could find the distances be- may be given. An old and well -known tween a few different sets of planes of example is shown in Figure 2. The the crystal, we could map out the posi- sodium acetate which is dissolved in tions in space of the units that lie on the liquid is very ready to crystallize; these planes. all the molecules are ready to set to This is exactly what the X -rays partners and are only waiting for some- enable us to do; they give us the one to begin. A little encouragement is given by dropping in a minute crystal of the substance, which sets an example to the rest, and the crystals are seen to grow quickly until the whole mass is really solid. Or, again, we spread a very saturated solution of a substance on a glass sheet in the lantern; the heat dries off the liquid and the crystals grow quickly under our eyes. This substance crystallizes easily and quickly, and for that reason gives us a convenient and ready illustration. Other things take long to form; the diamond, for example, takes so long or requires such special arrangements that the mode of A SIMPLE ILLUSTRATION OF its growth is very imperfectly under- CRYSTALLIZATION stood. FIGURE 2: The sodium acetate in the decanter is A is a regular of more than ready to crystallize. But the process does crystal arrangement not begin until a minute fragment of the crystal the units of pattern; just as an orchard itself is dropped into the solution.

www.americanradiohistory.com )f, l'OYI.'L AR 1:_All10

distances between the various sets of while the great bulk of the wave flows planes. The mode in which the on and meets successive sheets. The measurement is made is somewhat model is intended to show some of these difficult to understand without some reflected waves passing together out of knowledge of the physics of wave the crystal motions; on the right. It may be seen but perhaps the model shown from the in Figures model that these bundles of 3a and 3b will be of some reflected waves assistance. The may or may not be model consists, in the in step with each first place, of other as in Figures a table on which spots are 3a and 3b respectively. painted at regular In the former distances; they rep- case, there is a comparatively resent the arrangement of the strong pattern reflected wave formed by the com- units in the crystal. Stencils made of bination thin sheet of the weak reflected waves, lead are cut to represent of which waves. there may be hundreds of On the left of the picture the thousands. In waves are supposed the latter the waves to be rolling in on are out of step; the crystal, and and there is practi- the stencils are, of cally no wave motion course, arranged to as the result. be in step with each It all depends on other. The successive the relative adjust- sheets which can ment of three be drawn through factors -the length of the pattern units in the wave, the distance the crystal act like between the reflectors, each successive sheets, and the inclination sheet reflecting a very feeble of wave, the direction of the advancing waves

Model itlusfratinl, the (Fì03. fundamental principle of tfie analysis of crystals by x -rays.

HOW CRYSTALS ARE ANALYZED BY X -RAYS Fa.i ut.s 3A AND 3B: By means of these two models the fundamental principles of this phenomenon are illustrated as explained on pages 25 and 26.

www.americanradiohistory.com THE ATOM 27

Sensitive Flame Set of Sheets of Muslin

HOW SOUND IS REFLECTED reflection FIGURE 4: Lord Rayleigh's experiment, to demonstrate the phenomenon of the of sound, by means of a set of sheets of muslin; an illustration of the reflection of x -rays by a crystal. to the planes of the sheet. In practice, found within it. It is the hardest what happens is that the crystal is mineral that we know, and its brilliance slowly turned round while bathed in a makes it one of the most prized of all beam of X -rays; at certain angles the jewels. It is already possible to ex- reflections flash out. From the magni- plain many of the properties of the tude of the angles the distances between diamond from a consideration of the the sheets are calculated. way in which Nature has designed it. Many years ago the late Lord Ray- Every carbon atom has four neighbors leigh showed an analogous experiment placed round it in a perfectly symmetri- of acoustics. A high -pitched whistle cal manner. This is in perfect agree- (Figure 4) emitted sound -waves one ment with the long -established chemical or two inches long. A set of muslin fact that the carbon atom tends always sheets was held by a "lazy- tongs" to link itself with four other atoms and arrangement so that their distances no more. For example, methene is a apart could be varied; the sound went gas in which the molecule consists of a through all the sheets, losing a little of carbon atom linked to four hydrogen its intensity by reflection at each of atoms. This is the marsh gas which is them. The combined reflections acted generated in marshy ground, and some- upon a sensitive flame, making it flare times burns with a feeble light, the so- as shown; but only if the distances called will -of- the -wisp. between the sheets were properly ad- It is odd that the simple form in which carbon atoms group themselves justed. - The experiment of the X -ray and the should make so brilliant a gem, and that crystal is the fundamental experiment a form nearly as simple should be so of the new investigations into the opposite in character as graphite or structure of matter. It shows how the black lead. A single crystal of graphite pattern units are spaced in the crystal. is almost unobtainable and the X -ray The diamond is perhaps the most methods are somewhat hampered in interesting of all the crystals in the their application to the determination world. It is remarkable bor the beauty of its structure. and simplicity of its structure, and It is impossible to reduce it to powder important because it is the simplest of in a mortar. It becomes simply a mass the forms in which the atoms of carbon of fine flakes which slide over one join themselves together. The basis of another with the utmost ease. For structure of organic substances can be the same reason, it is easy to slip on a

www.americanradiohistory.com 28 POPULAR RADIO black- leaded hearthstone, because some the graphite sheet which we have of the flakes cling to the hearthstone formed by splitting the diamond in and some to the soles of one's shoes parallel planes; it is a hexagonal net - and the flakes slide readily over one work. We now cut through certain another. Graphite therefore makes one bonds and divide the whole up into of the best of lubricants. separate hexagons. Each carbon atom The diamond and graphite structures is now joined to two others; it has are the only two which are composed two idle bonds. To one of these we of carbon alone. Structures of carbon attach in each case a hydrogen atom, and hydrogen, or carbon, oxygen and and we have now the famous benzene hydrogen, or the same with a flavoring ring. of other atoms, are very numerous and Benzene was discovered by Faraday form a most important part of the sub- in 1825; a few drops of his original stances found in nature. Indeed, their liquid are preserved in the library of the study constitutes the bulk of the sub- Royal Institution. He did not know ject of organic chemistry. They are its form, only that six carbon and six found as the main constituents of living hydrogen atoms went to the making of organisms, whence their name; we meet it. It was Kekulé who first guessed them continually in industrial work, as that the carbon atoms formed a closed in the dye industry, the leather indus- .chain. try, the cotton industry, the manufac- The benzene ring is found in half of ture of explosives, and in many other the sum -total of organic substances, and places, so that their study is of the because some of the first to be studied highest importance. were the essences of the lemons, oranges, If we dissect the diamond structure, and the like, the whole class of sub- we arrive at combinations of carbon stances founded on the benzene ring atoms which we find are the basis of has been called the "aromatic." all these organic compounds. We take The placing of the hydrogen atoms

s

A THE HEXAGONAL FRAMEWORK OF THE DIAMOND FizUP.E 5: The graphite sheet that shows the division into the two kinds of chain molecules, AA and BB.

www.americanradiohistory.com THE ATOM 29 round the benzene ring has ' quite re- moved the strong attachment to other rings which it had when it formed part of the graphite sheet. Benzene is a liquid at ordinary temperature. All sorts of additions and substitutions can be made to the ring, and every new substance made in this way has its own special properties. The graphite sheet may be cut up in other ways : along the lines a a in Figure 5, or, again, along the lines b b. The chain may be of infinite length. Both these chains occur in Nature; they are the basis of the so- called chain compounds. They have been investi- gated in the Royal Institution. Dr. Muller and Dr. Shearer have found it possible to measure the length of the chain to a high degree of accuracy. Take for instance, the latter chain; every carbon has vacancies for two at- tachments except the end carbons, which have three. Let one of them be satis- fied with three hydrogens, and let the other end carry a special group formed of two oxygens and one hydrogen. Then we have a series of substances called the "fatty acids," all known to chemists and named by them. Thus we have palmitic, myristic, lauric acid, and others. When the chain is short, the substance is liquid at ordinary temperature. But the longer chains belong to solid substances, and the longer the chain the higher the melting point. THE RUBY MOLECULE a little of one of the solid mem- FIGURE 6: This model contains two atoms of When aluminum and three of oxygen. A shows one bers of the series is melted and poured side of a molecule and B the other side. on to a piece of glass or mica, layers of molecules are formed on which all the a molecule. It is the arrangement in molecules are perpendicular to the glass; layers which makes it possible to and the layers lie above one another, measure the lengths of the molecules by hundreds in succession, like a series of means of X -rays. carpets, each hair of which represents

Important Kinks in Wiring What wires to "bunch "; what wires to isolate; what wires to use spaghetti covering on -these are some of the useful bits of infor- mation in an article b Louis W. Hatry-in POPULAR RADIO for February.

www.americanradiohistory.com From a photograph made for POPULAR RADIO A PRACTICAL INVESTIGATOR OF COILS AND THEIR FUNCTIONS The author of this article, who is an instructor in radio, is an Associate Member of the American Institute of Electrical Engineers and of the Institute of Radio Engineers. His studies of coils have helped materially in the work of radio experimenters. SOME NEWcolts AND USEFUL FACTS ABOUT Many fallacies exist in the minds of experimenters about the "low- loss" feature of coils or inductances. Many of the so- called "low- loss" coils that are now popular in the radio field have lower efficiency than some of the older types. Just what constitutes a "low- loss" coil and how the characteristics of coils have been carefully studied is told in this article. By D. R. CLEMONS

DISTRIBUTED capacity of induc- in which C represents condenser capacity tance coils may be defined as the lumped in farads, L the pure self in- inherent constant Co which satisfies the duction and Co the distributed capacity equation for frequency, of the coil, units being in farads and henrys. f= 1 27r Ai LC. As both the self induction and dis- tributed capacity for the coil free and oscillating at its of coils follow directly the geometrical fundamental, and for the coil operating dimensions of the coil, in obtaining maximum in a tuned circuit, C. satisfies the equa- a self induction tion with a given length of wire, a large ca- f- pacity may result. Inherent coil capac- 2 7r ÿ L (C-1-Co) ity, which is undesirable, involves the 30

www.americanradiohistory.com USEFUL FACTS ABOUT COILS 31

losses coil dimensions And the inductive capac- From the literature dealing with ity of the dielectric through which the in inductor coils it seems that with ca- electric field acts, hence with a given self pacity a certain fault in coils, any addi- induction the variable is the constant K, tion whatever of varnish or insulation of the medium surrounding the coil. The which tends to increase capacity magni- most satisfactory formulas for evaluat- fies the defect directly as the constant ing coil capacity seem to have been of such added material. As a result of given by Mr. G. Breit, and for cylin- snap judgment one visualizes enormous drical windings of bare wire in air, with increase of capacity and this has led to the coil free and ungrounded, C. yields an over- estimation of its magnitude. well to the formula While application of varnishes does in- crease the coil capacity, it is impossible 0.06952 K 1 m -mfds. C.= in any coil for this increase to be di- the where 1 is the coil perimeter and K the rectly as the inductive constant of inductivity of the dielectric. The con- varnish used, and in most cases is en- stant K is usually doubtful, as dielectrics tirely removed f rota the constant. In about coils are largely influenced by com- fifteen coils successively treated with pound materials such as insulation, tub- various high class varnishes, every one ing, and possibly varnishes. showed an actual decrease of effective Interesting discussions have arisen due resistance. This was clue to the better to divergent opinions as to the exact insulating properties of varnish than for effect of foreign dielectrics such as var- raw cotton and silk insulation exposed nishes which tend to increase undesir- to atmospheric changes of humidity. To able capacity inherent to the coil. One show the actual improvement of . the prominent writer believes that "due to various coils, Table I is given. Not one the higher constant of insulating papers, showed an increase of resistance after the addition of papers between layers having been treated. (of multi -layer coils) will increase the It will be shown that capacity increases distributed capacity directly as the in- directly as the inductive constant only ductive constant of the paper." when the coil's electric field is entirely

/

THE ELECTROSTATIC FIELDS AROUND COILS FIGURE 1: At the left is shown a multi -layer coil with its accompanying electrostatic field; notice that it covers a greater area than the fields in either the spiral winding (in the center), or the solenoid winding (at the right). The wires are shown as in cross -section.

www.americanradiohistory.com 32 POPULAR RADIO occupied by the added dielectric material at very high frequencies which condition causes such ac- is never possible in fact; tion in the medium, and also, other factors we may con- which indirectly de- sider it a sudden and highly transient termine capacity increases include, or de- movement of electrical energy through pend upon the coil shape, nature of wire the medium. We may think of the insulation, penetrability and inductivity in- tensity of this movement as closely re- of the varnish or compound and so on. sembling the quotient of the strain di- Characteristic electric fields are shown vided for by the stress as in mechanics. the solenoid, spiral and compact While displacement windings, which is present, energy is embrace practically all stored in the medium, types of winding and as displaced now in use, sketches units can act through being given in Figure but a short dis- 1. While great- tance they have a velocity est flux density is found and distance, between adja- which gives the equivalent cent turns for the spiral of current and cylindrical for a short interval of windings, the density per time; so for high unit area is radio frequencies the period much greater in the compact of the po- windings tentials appearing on the wire due to the components of the many turns sections becomes more nearly equal to the in traverse layers acting through small free displacement period of the entire atomic distances. By observing the induction system effects of the dielectric, at which fre- between two circular areas one quencies may form the energy stored during tran- a mental picture of the ac- sient periods tion in is considerable. the entire field as applied to coils To represent of any shape. this action in space where it becomes necessary to observe In Figure 2, two wire cross -sections the represent equi- potential lines along which in- two areas on adjacent turns duction of is taking place, familiar lines of a winding, the wires having cotton electric insulation force may be obtained. Both the of normal thickness, the re- gradient maining distribution and apparent lines medium being air. Now, the may potential be observed by laying two smooth difference acting through space metal discs on an ebonite plate ; a poten- between the sections permits an atomic tial of several thousand volts is applied orientation or orbitary shifting of the tiny to the electrodes and fine mica dust is electrical components within atoms sifted occupying over the space occupied by the space and the dielectric about electrical the two surfaces, fields. The dust particles ar- which motion is equiva- range themselves lent to a movement as the solid lines shown of electrical energy in Figure 3. We and is large or find that such electric small according to the lines of force represent inductivity of the medium only lines along considered. which induction and displacement The potential of one section act, acting to- that they arise and return perpendicu- ward the potential of the second section larly from potential surfaces, and that B

THE ELECTROSTATIC FIELD BETWEEN TWO TURNS OF WIRE FIGURE 2: At A is shown the distribution wire in of the electrostatic field between two turns air and at B is shown the field of two turns of Notice that in this of wire wound on an insulating tube. case the electrostatic field is included through material thus slightly increasing part of the insulating the capacity between the two turns of wire.

www.americanradiohistory.com USEFUL FACTS ABOUT COILS 33

A THEORETICAL FIELD OF FORCE BETWEEN TWO TURNS OF WIRE FIGURE 3: Two black dots represent the two wires in cross- section and the dotted lines are the equi- potential lines. The solid lines show the apparent lines of force that have been given roughly for different types of coils in Figure 1.

a number of them from one electrified sidered. And were the two wires with- surface is related to more than one other out insulation other than air, we have a surface, or between numbers of other sur- uniform flux distribution in space as con- faces acting in the same medium in the sidered from the current axis at any in- case of inductance coils. Where a large stant ; hence under these conditions the number of turns are acting in a small coil capacity yields well to formula cal- volume of space the distribution of po- culations of distributed capacity for the tential causes displacement quite uniform air insulated coil in free space. near each surface, but in acting through Now; let us suppose that these two the dielectric, the entire displaced action wires are sections wound on a fiber tube, is formed by the component of the many M, or are near to some medium of points acting as in Figure 4. Methods higher permittance than air as shown in for calculation of component fields rep- Figure 2B. resented by such lines were given by We find that, due to the higher per - Maxwell and others. mittance of the medium at M, a high Referring to Figure 6D (assuming a gradient and approximately equal dis- uniform dielectric everywhere about the placement. is also present in M in addi- wire surfaces) the capacity is increased tion to that through the air or between according to the constant of the medium, the two wires, assuming that both wires and the flux in the medium at any region are separated from the tubing M and is the voltage gradient of that segment from each other only by their cotton divided by the flux resistance or elas- insulation. Obviously, then, we have in ticity of the medium in that segment, addition to the flux actually between which latter value is the reciprocal of the turns, another growth of flux through permittance in the dielectric segment con- the medium M, and the capacity is ac-

www.americanradiohistory.com 34- POPULAR RADIO

cordingly increased by the presence of very fine wire connected with the blocks this new sub- material. Though induc- are shown in Figure 5A. Now, one fa- tion acts through a much greater dis- miliar with condensers considers the sur- tance in the medium M than for the faces or area actually between the two space directly between the wires, it oc- plates, since the edge effect is negligible curs through a medium of considerable as compared with flux density in the di- permittivity, and if this is sufficiently electrics of high inductivity generally high the voltage division permits con- used. Between electrified bodies having siderable flux to be developed. plane surfaces, displacement may act To demonstrate the reappearance of through a medium not actually between flux in greater density even though act - the parallel surfaces forming the elec- ing through such greater distances, the trodes. This "edge effect" between following experiments were made : plates as computed by Maxwell is demon- Two hardwood cubes 1.25 inch on a strated at Figure 7. The two blocks sus- side were covered with lead foil glued pended in air gave 26.1 m -mfds. capac- to their surfaces; the blocks were se- ity. The blocks were lowered to touch the cured by screws to a bakelite strip, their surface of a quantity of olive oil and then separation being about 0.1 inch between raised to prevent cohesion and capillarity, parallel surfaces. Short terminals of the oil being shown in Figure 5A, for

THE DISPLACEMENT OF ELECTRIC LINES OF FORCE IN CROWDED COILS FIGURE 4: This drawing shows diagrammatically how the electric fields between adjacent turns in multi-layer coils may be crowded and distorted. Although the spacing at the sur- face of the wire is usually fairly uniform, the spacing in the less densed part of the field is usually non -uniform.

www.americanradiohistory.com USEFUL 'ACTS ABOUT COILS 33

B HOW THE TESTS WERE MADE FIGURE 5: These drawings show how two square fiber blocks and two cylinders covered with foil were used in tests in a tank containing oil to determine the effect of change in capacity when the blocks and cylinders were suspended in air or when thoí; touch the surface of the oil which had a higher dielectric constant than air ,:self. which position the capacity became 36.8 should increase the distributed capacity m -mfds. The increase of 40 percent is of the system. The increase is slight and due to the effects previously explained never becomes according to the constant and shown in Figure 2B. To represent of the material unless the entire electric the effect for round wires, two fiber field acts in the new medium. The blocks cylinders 1.25 inch diameter and 1 inch did not show an increase according to the long were covered by a cylinder of foil constant K for this reason, but sub- and adjacent surfaces were separated merged to a greater depth in a greater 0.06 inch as shown in Figure 5B. In air volume of oil, the constant was approxi- the capacity between these cylinders was mately the same as the ratio of the ca- 1.70 m-mfds., and when lowered to oil, pacities for the two positions. Figure the surfaces barely touching the surface 2B is equivalent to wire wound on in- as shown, the capacity increased 53 per- sulating material. cent to 2.61 m -mfds. Obviously the po- To show the actual increase of capacity tential redistributes itself in acting due to forms and tubing requires exact- through this new medium. At this time ing methods. The tubing must be re- the cubes were entirely submerged in the moved without any disturbance whatever oil which extenied a depth of 0.5 inch of the coil dimensions. To draw a tube on all sides of the blocks. The capacity from a coil without changing dimensions increased from 26.1 for the blocks in of the coil, hence its self inductance, is air to 66.5 m- mfds., giving an increase almost impossible; hence, simply to meas- of 2.55, which compares well with the ure the fundamentals of a coil with and inductivity of the oil, which was 3.08. without the tubing does not indicate '1 his illustrates experimentally that the whether it is capacitive, inductive, or a presence of new dielectrics about wires change of both constants. When meas-

A \M B M 0 C HOW TESTS WERE MADE ON COILS WITH WIRE COVERED WITH AN INSULATING VARNISH OR FILLER FIGURE 6: At the left are shown wires wound on an insulating cylinder and then varnished or dipped in an insulating compound. Notice that the compound makes a body that covers up the wires in greater or less degree.

www.americanradiohistory.com 36 POPULAR RADIO ured in terms of wavelength only, the stants were found to be again their first effects of tubing on coil capacity are re- value, showing that while the inductance ported much too large and lead to an remained constant the tubing increased over -estimation of this effect. the capacity only 11.8 percent although To show exactly the increase to expect the glass had a very high constant of from the addition of tubing the following 6.85. By sealing one end of the tube it experiments were performed: was then filled with oil, giving in effect A flint glass cylinder 0.08 inch an oil core inside the winding, for which thick and having a slight taper was the capacity increased 2.68 times becom- obtained and wound with No. 26 ing 7.76 m -mfds. double- cotton -covered wire into a coil Next, the tube was filled with distilled 18.5 cms. long and 7.0 cros. mean diam- water. The capacity became 23.92 eter; several thin strips of paper were in -mf ds., the inductance in both cases re- pasted along the outer surface forming maining the same (the constant of dis- spirals to securely hold the winding shape tilled water is about 80). The coil was constant during the experiment. The then removed from the tube and dipped coil was carefully measured and found in hot paraffin which was absorbed by to be of 824.8 mhys. pure inductance and the insulation and enclosed the wires of 2.889 m -mfds. distributed capacity. somewhat as shown in Figure 5 at A, its Then the glass tube was carefully re- depth being about 0.6 inch. The ca- moved and the coil, now a mere shell, pacity increased to 4.39 m- mfds., show- was measured and found to have 824.8 ing a tendency to increase according to mhys. pure inductance as before but a the constant when the material occupies smaller capacity of 2.580 m- infds. When the space subject to maximum flux den- the tube was again inserted both con- sity along the winding.

==MM.:_:=.. _-_-=_1__M-Aw- INIMMMININIY =__M_M--YSYYNINI Mi:

THE FIELD AT THE EDGE OF CONDENSER PLATES FIGURE 7: The curve of the equi- potential lines and the stressed lines at the ends of two parallel condenser plates. Notice how the field is bent around the edges of the plates.

www.americanradiohistory.com USEFUL I' A CT S ABOUT CU I I. S

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FIGURE 8: This drawing shows how a multi- layer coil impregnated really FiGtRE 9: This, diagram shows the action of a with liquid varnish has only the outer portion covered. The varnish few lavers of paper on the electrostatic fields be- seldom penetrates through the insulation except by tween layer turns of wire. long immersion. To show the increase of capacity for Owing to the difficulties encountered a dielectric of greater volume and which in removing Bakelite tubing from the is everywhere closely related to one sur- finished winding without altering the self face of the coil, the spiral was next low- induction of the coil, another method of ered with one surface resting on oil hav- measuring the effect of Bakelite material ing a constant of 2.11; then the capacity, was resorted to. We have elsewhere re- due to the action being illustrated in ferred to the similarity of constants and Figure 2B, was increased from 3.1 field distribution about solenoids and m -mfds. to 6.70 ni-mfds., which is about spirals of small winding depth, and we as before, 1.821 times the free coil ca- find by observation one plane surface of pacity. To provide a dielectric of high a perfectly flat spiral is equivalent to the permittance distilled water was again inner cylindrical surface of the solenoid; used and the coil lowered to the surface therefore, by laying a perfectly flat spiral gave 79.4 m -mfds. capacity which in- upon a sheet of material we have the creased from the normal 3.1 m-mfd. Al- equivalent of a tube having the sanie though the constant of distilled water is thickness as the sheet, and the effect on about 80 the increase is but 25.5 times the the capacity is identical. In this way free coil capacity. The inductance was there is no change of self induction or not altered by the presence of the water. of initial capacity while handling the coil. Obviously, then, the addition of tubing A flat spiral 17.4 ems. diameter wound will only slightly increase coil capacity; with 41 turns of No. 22 double- cotton- the increase will not be directly as the covered wire having 220.2 mhys. induc- constant of the tube or forni but is gov- tance and 3.10 ni -nt f ds. capacity for the erned somewhat by it, also the thickness free coil was first placed on a sheet of and nature of the material together with laminated Bakelite material 10 inches considerations of the insulation depth on square and 0.187 inch thick, the copper the wire. being separated from the material by- Insulating varnishes may be applied its cotton insulation only. The capacity to solenoids and spirals without increas- increased from 3.10 m -mfds. to 4.60 ing their resistance at normal f requen- m- mfds.. which is 1.48 times the free coil cies, nor does varnish or impregnations capacity ; then, when lain on a similar appreciably increase the capacity of the grade of material twice as thick or 0.376 coil if it is applied thinly. Referring to inch, the capacity became 5.6 m- mfds., Figure 6 at B we find that wires wound which is 1.81 times its free value. over the tube have a slight increase due Though this increase is considerable, it to the tubing being inserted or remaining is not proportional to the constant of this in the electric field ; then since varnish very satisfactory material having induc- seldom does more than penetrate the tivities of 2.6 to 3.07, depending on the fibers of cotton and silk, and probably grade. merely fills the cavities within the wind-

www.americanradiohistory.com 38 POPULAR RADIO

ing, a great quantity of material is not wire was submerged in olive oil as in added by a light application of varnish Figure 5D for which the capacity be- though it occupies a position of greatest came 69.0 m -mfd. for the oil dielectric; density about the wire. Hence the mere then, by drawing up the wires cohesion substitution of one dielectric for another of the oil gave a distribution of oil as does not cause a great increase of ca- at Figure 5C, which is about the shape R pacity. that applied and dried varnish would For example : have assumed, then the lumped capacity A solenoid of 23 double- cotton -cov- was but 57.0 m -mfd. Therefore, a light ered wire had a capacity of 7.245 m -mfd., application of varnish would resemble and after having applied three heavy B and C in Figure 5 for which the ca- coats of Redmanol, a phenol product, the pacity increased 2.25 times, while for capacity increased to 8.275, which is complete submersion the increase is ob- but 14 percent above normal for this ex- viously 3.02, which was found to be the tra heavy application of this varnish, and constant of the oil used. Such wetting though its constant is about 2.62 when of the winding gives the equivalent ef- properly dried under heat and pressure. fect of an applied varnish on the coil. Although cotton and silk have each an We have shown the coil capacity should inductivity of about 4.86 when it resem- increase according to the constant K only bles a solid dielectric, it is not an im- when the electric field is entirely con - portant detail where the insulation about tained within the added dielectric, but wires consists of cotton or silk as these this is never the case for coils used in are usually a complex non -solid nature radio circuits and of the solenoid and due to the complex position of the fibers spiral class, but since the field of the making up the dielectric ; therefore, cot- compact windings of square cross -section ton insulation absorbing varnish becomes is largely contained within its winding practically a compound solid dielectric. surfaces, the field of the latter type does For solenoids and spirals, since varnish act almost entirely through impregnation ordinarily occupies but a small part of material applied to coils of the compact the entire electric field the capacity in- type, and the increase is approximately

crease in them is small and is certainly as the constant. To illustrate this : 3 far from any direct relation to the con- coils of equal wire -lengths were designed stant of the varnish material, but with for best shapes in spiral, cylindrical and a given coil the increase will largely de- compact types of winding. By submerg- pend on the absorbing properties of the ing each coil below the surface of oil of wire insulation together with the amount known constant we have the equivalent of varnish applied and its inductivity effect of the electric field acting within when dried. a large dielectric about the entire coil, In Figure 6A, where A represents a while, by withdrawing them, the oil wet- greater quantity of varnish than at ting the insulation and adhering between B, the capacity at A should be larger turns is at once equivalent to an applica- than at B which is small, since at tion of varnish, which method applied A the flux acts through a greater to the three coils described gave the f ol- volume of dielectric material than at lowing results : B where a large part of the field Co Dry Coil in Air, Saturated, Submerged, Increase is through air only. To demonstrate m -mfd. m -mfd. m -mid. per cent. Solenoid : No. 22 3.566 4.18 4.44 17.3 this two double -cotton- covered Spiral. 2.520 2.972 4.04 18.0 wires having a length equal to one com- Compact 4.190 7.547 8.684 80.0 plete turn on the coil described were For the first two the gain is but 17 and lain parallel and twisted together ; their 18 percent of the free capacity, but for capacity was 22.80 m-mfd.; then the the compact winding the saturated ca-

www.americanradiohistory.com - ( ()1f.S 39

'. 11 .1 141re-4wrrlatrow K 14./ ',low 1/41s t:'r flit .; ./ i ::e I)enfare percent.

! 24 GottrM -14 S b ; (, 1 14 " A 4 4.4 In x 9 14 r) K/ " /, - i lacer hanked 7 ? ' I) S 2 h8rkr.I A 24 " i1 26 ellamet I (1 77 dnahb silk 14 )4 enamel

parity is 1.8 times the free c;Ip ;u. ((tent than for air between two turns, it while complete sullmt'r.o ii inrrt'a;('d the does not occupy such a relative position capacity 2.07 times, showing that the %sitll respect to the trav -rie layers or to (impact winding gives a capacity increase the entire field acting in the region of hear!%' as the inductive constant with per- the winding. Since the paper is prob- fect saturation or impregnation. The oil ably less than O.CX').i inch thick in most

In this case had a constant of 2.11. . \ir rases, any refraction of flux in it is I wkets and irn1cnetration prevented a negligible and the density is not appre- direct increase, therefore, a coil of the ciably increased, moreover, traverse lay- honeycotnb type of 1(X) trlrn, was suh- ers being further separated tends to re- merged. This permitted llen('trati1In to duce the flux and capacity of the svinding all parts of the coil and the In rra-r \vas for a given wire -length. The potentials from 11.27 to 23.61 m mfdl which is in a thin segment of a compound dielec- approximately as the constant 2.11 of tric are divided according to the thick - the dielectric. ness and inductiyih' of the medium. A. 'Rhin varnishes applied to coils tall potential i: acting between two such to entirely penetrate compact windiness. wires. and through the cotton insolation therefore it is improbable that increases in of thickness d,, and constant k,, devel- this type is greater than Ill percent above ops a potential l':, through the paper of the free coil capacity. ( hie coil being thickness d, and constant k., according wound no of square cross -section and to the formula. supposedly well impregnated with liquid 1: E, bakclite was found to have hot the fluter l portion impregnated as shown in I' igur-c l t ,I,Ii 8 which would he the case for most var- ( lhyinusly the comparativearative thinness of nishes applied with a common brush or the paper cannot permit ;t great potential by simple submersion. to operate through it except at a small The addition of thin paper insulation segment syhere the wires rest on the in milltidayer coils will not increase the paper hence the total increase of flux and capacity directly, or even approximately, capacity is slight and is certainly not di- as the constant of the paper. Referring rectly as the indnctiyity of the paper to Figure o we have several thicknesses would indicate. of paper between two successive layers. Apart from the effects of capacity. the While the paper is locate(i ill position of etTectiye resistance of in(luctallce coils Igreatest flux density it does not even also involves leakage and other dielectric approximately occupy the entire electric losses. it is certain that any varnish will field which in a large number of turns. improve the insulating properties of raw is a component of many potentials acting. cotton and silk exposed to moisture as Though it has a higher centimeter gra- we have shown in Table I.

www.americanradiohistory.com Frain a photograph made for POPULAR RADIO When Your Set Won't Work Irkere to Look for Trouble and How to Fix It By EDGAR H. FELIX, M.I.R.E.

WHEN your first automobile gave of trouble is to try every connection, trouble, it made some kind of a every control, every adjustment, one at snort, squeak, wheeze, or dying gasp a time, until you finally hit upon the which gave you a clue to the cause of part out of order or the incorrect ad- trouble. justment. But a radio set just simply stops There is, however, a sensible, logical, working. and direct process of analyzing faults The powers that operate it are in- in a radio set. In this article I will visible ; they do not cause response to give you an idea of what to do if your our sense of smell, taste or pressure. set suddenly stops working. They respond only to our sense of There are only three general symp- hearing. These forces are so elusive toms of trouble which can be detected that a detective cannot trace them. by the human senses. These three They slip out of the wrong door at the symptoms all appeal to the sense of least opportunity, and if you do not sound. First, you can easily tell if you treat them exactly as you should they are not receiving any signals at all; will not serve you. second, you know when you get an It is for this reason that radio receiv- unusually weak signal -much weaker ing troubles are so hard to analyze. than you are accustomed to hearing The only apparent way to find the cause from a given station; and, third, you 40

www.americanradiohistory.com WHEN YOUR SET WON'T WORK 41 can readily distinguish noisy reception. Where to Hunt for Vacuum Tube Trouble these three distinctions do Although The first thing to do is to examine be of particular help, they not seem to filaments. Do they light properly to at once eliminate a your do enable you and to full brilliancy? If they light at causes of trouble and good many possible all, the filaments are not burned out. upon those which are to concentrate If they do not light when a battery of be the cause. most likely to proper voltage is applied to them, they What to Do When You Hear No Signal are burned out. For this there is At All usually no remedy except to buy new The first of these symptoms of tubes. is the only possible cause trouble -when you hear no signal at But this not perhaps the least exasperating. of vacuum tube trouble. The filament all -is properly; the spring There is no question that something is may be burning to the prongs of the tube, wrong when you do not hear anything. contacts you set to work to solve on inspection, may show that a good Consequently prong, the mystery. contact is being made with each hear a sound. Some- If you have been receiving signals yet you may not then suddenly they stop times the new thoriated filament tubes nicely, and vitality without the filament without any apparent cause, look first lose their out. If this is the case try out to the adjustment of your detector. burning in a tube rejuvenator to restore If you use a crystal detector, monkey the tube the adjustment until you have the thorium to active condition. with which found a sensitive spot. In this lies the Look to your "B" battery, provides the high voltage for the plate cause of most of the troubles in crystal receiving. circuit. Are its connections complete? detector click in the phones excellent aid to adjusting a crystal Do you get a loud An the telephones from detector is the use of a high -pitched when you disconnect Connect with one side of your the plate circuit? If you do not there buzzer. the plate cir- the terminal of the buzzer where is something wrong with detector to end, the make and break of the connection cuit. Trace it from beginning from the plate as far as the filament. is made. You can easily identify which phone connections. Some- buzzer terminal this is by the little spark Try your off the head the set screw making the contact times one of the cords pulls at loudspeaker connections. with the movable arm of the buzzer. piece or plug does not make a This contact is connected directly with Sometimes th good contact with the jack. one of the two terminals of the buzzer. is a variometer the buzzer is thus connected With some sets there When This variometer operating it will set up magnetic in the plate circuit. and receiver. Occa- in the secondary circuit of makes it a regenerative waves to the rotor your receiver which will enable you to sionally the connection adjust your detector. At various de- becomes broken from continued use. tector adjustments the buzzer sound in Examine the leads carefully. the head telephones varies in strength. How to Test the Plate Circuit Leave the detector adjustment alone when you find a good loud point -you Touch one of the plate battery bind- are then ready to receive. ing posts with your wet finger. If your When a vacuum tube detector gives plate circuit is complete, your filaments no signal at all it is usually a sign that lit, your "B" battery at full strength something serious has happened. and the wiring correct, you should hear Vacuum tube detector troubles, how- a click when you touch the "B" battery ever, are not difficult to locate. binding post with a wet finger. There

www.americanradiohistory.com 42 POPULAR RADIO is something wrong in the plate circuit of the small sizes last anywhere from itself if you do not hear a click under one day to three months. You never these conditions. It may be with the know what to expect of a small battery. telephones or the loudspeaker. If the "B" battery has run down, you do not get a sharp click when the tele- How to Check Up Your Antenna phones or loudspeaker or the "B" The cause of trouble may lie in the battery are suddenly disconnected from antenna system. A loose antenna con- the plate circuit. Be sure the filaments nection sometimes makes it possible are lighted when you make your test. to hear faint signals, but when your With a home -made vacuum tube set, lightning switch grounds the antenna, where the binding posts for the storage the chances are that not a sound can be battery and the "B" battery are not heard in your telephone receivers. Look marked with plus and minus signs, you over the antenna system, trace it through may make the error of reversing the the tuning inductances to the ground battery connections. If you have done connection; trace the secondary cir- this, reverse them again so that they cuits of the receiver from the grid con- are as they should be. The positive nections on the tube bases to the fila- terminal of the "B" battery should ments, making sure there are no loose connect with the plates of the tubes connections with switches, binding posts either directly or through the phones or movable tuning elements such as and tickler coil. variometers and variable condensers. Another possible cause of trouble is If your set ever worked at all, a too great a degree of filament brilliancy search of the kind I have indicated will on the soft detector tube or too high locate the cause of trouble. plate voltage or a grid -leak of too high resistance. As you gradually increase What to Do When Your Signals Are the filament brilliancy beyond normal, Unusually Faint the first effect is a rapidly increasing A different kind of trouble may be the hiss. A still greater increase causes a cause NO en you hear only weak signals. louder hiss until you hear a click and Every station comes in evenly and signals stop altogether. Your tube is smoothly, but it is only half or one - now what is termed in technical parlance quarter as loud as usual. This usually "paralyzed." Under this condition you happens when you are trying to demon- may sometimes see a faint blue glow strate your radio set to friends. around the filament and near the plate. With a crystal receiver the first thing Oftentimes a strong signal from a near- to do is to get a better adjustment by station tips the balance and causes of the crystal. If a number of careful tube paralysis if the grid -leak is not attempts of adjustment produce no properly adjusted. improvement, look elsewhere for trouble. Too much plate voltage also causes With a larger set using radio frequency the same trouble. Reduce the plate amplification and a vacuum tube de- voltage to normal, and decrease the tector there are various possible causes. resistance of the grid -leak. First, be sure the filaments light to When using a regenerative receiver normal brilliancy. It may be that there is another possible cause for signals the filament storage battery has run dying out. If too much inductance is down and needs charging. In that used in the plate circuit the tube starts case you do not get proper filament oscillating which destroys the tone of all brilliancy. voice and spark signals. A readjust- Another possible cause is a run down ment of plate inductance is necessary "B" battery. Large capacity batteries to remedy this. last from six to twelve months. Some Weak signals are often received when

www.americanradiohistory.com WHEN YOUR SET WON'T WORK 41

When Your Receiver Won't Work- A -See that your lead -in and antenna wires are E -See that your condenser plates are spaced securely and electrically connected; equally and do not touch each other; B -See that your ground connection has per- F- Change the phone tips of your loudspeaker fect contact with the water pipe, radiator, terminals, to give best reception ; or other grounding means ; G-See that all the soldered connections of the C -See that your "A" battery wires are con- grid and plate circuits are all right. If nected to a clean surface of the lead you are not sure that the connection is terminals ; the negative terminal must go complete, test it by placing a pair of to the negative binding post of the set; headphones across the connection with a D -See if the filaments are lighted. If they "C" battery in series with the head- are not- phones; if there is a loud click the con- t. See if your socket prongs make contact; nection is perfect. (This test applies to if they do not, bend them up higher; all connections.) 2. See if your "A" battery connections are H -Test the primaries and secondaries of the poor; coils by the headphone- ; 3. See if the filament wiring in the set is battery method unsoldered or broken; I -Test your `B" batteries, which should meas- 4. See if a tube is bad; test it out in another ure at least 80 percent of original voltage. socket to find out if only prongs need Your "A" bending up: battery should show no less 5. See- if the rheostat winding is making a than 1175 on the hydrometer before re- complete connection with its terminals. charging.

www.americanradiohistory.com 44 POPULAR RADIO the antenna is disconnected, either by a broken connection. Shake the wire break in the lead -in or by leaving the which leads to the telephone head switch in the grounded position through piece or loudspeaker. If" that produces an oversight. Trace the entire antenna a series of clicks and wheezes you may system thrcugh your set. See that good find the copper wire has come loose from connections are made with the tuning the cord tip. elements. If there is a variometer used, Sometimes the trouble is not with your examine the connections. See that the set at all. It may be that there are ground lead is unbroken and makes variations in the strength of the in- good contact with your ground connec- coming signal, due either to transmitter tion. troubles or to an absorptive receiver in Go up on the roof and see if the your immediate vicinity. This is not antenna wire or the lead -in "grounds" difficult to diagnose. All you have to at any point. Trace the secondary cir- do is to tune to some other station, cuit of your set. You often get weak whether spark or telephone, it makes no signals although there is a break in the difference. If a loose connection is the grid connection to the secondary induc- cause of your trouble it will affect all tance. stations alike instead of only one par- If your trace of antenna and second- ticular station. ary circuits has shown them to be in If varying the controls and trying the good working order, the trouble must head receivers does not locate the lie in the tube circuits. Do not over- trouble, trace each circuit, beginning look the test for phone sensitiveness and with the plate circuit. See that the condition of "B" battery already men- connections at the base of the tube are tioned. Your diagnosis, if thoroughly good. Trace all the battery connections done, is bound to reveal the cause of and the plate circuits. Then trace the trouble. secondary circuits from the grid through the inductances How to Check Noisy and to the filaments. Finally Irregular Recep- trace tion the antenna circuit from one end through the tuning elements to the The final class of troubles accompany ground. noisy reception. You may for a moment A steady reception of noise, which get a good loud signal and then suddenly does not vary no matter what tuning it dies down ; later it comes back in full adjustment is used, is sometimes caused strength. This is the easiest kind of by a low "B" battery used with a reflex trouble to locate. But you can only receiver. It is often possible to get locate this if you keep your temperature additional service from such "B" bat- below 104 and refrain from getting ex- teries by using them on non -reflexed cited. tubes. With heavy current drain sets When great variation of signal extra large "B" batteries give the most strength attends reception there is a economical service in cost her hour of loose connection somewhere. Slowly use. Another cause of noise may be operate each control of your set, one at vibrating tubes caused by building vibra- a time. If there is a break in the vario- tion, typewriters or nearby machinery. meter leads or the connections to the There are other causes of trouble switches, you may readily find it by this but these which I mention constitute process. If the trouble lies in a loose the 99 percent of them all. The remedy connection, sit perfectly still in front of in each case is simple and obvious once the set for a moment without moving the cause is located. your head or hands and see if any varia- Once you have successfully discovered tion in signal strength takes place. If it a trouble, the next time it occurs you can does not, continue in your search for locate it in an instant.

www.americanradiohistory.com From a photograph rnad for POPULAR RADIO HOW TO SCALE OFF THE ANSWER TO YOUR RHEOSTAT PROBLEM First determine the positions on the charts where the known specifications are located; then connect these points with a ruler which will fall upon the reading you seek. A MEASUREMENT CHART FOR USE WHEN SELECTING A RHEOSTAT FOR A MULTI -TUBE CIRCUIT Article No. 13

By RAOUL HOFFMAN, A.M.E.

TO control more than one tube by a By connecting tubes in parallel,* the single rheostat simplifies not only resulting resistance will be inversely pro- the building of a radio set, but reduces portional to the number of tubes used; the contacts in the filament circuit ; and therefore equation (1) will be thus adds to the efficiency of a radio Voltage receiver. n X Amperes - 2 R-I-12T Difficulty is often encountered in the n selection of the proper rheostat. Applying Ohm's law to the filament or Voltage circuit, we have Amperes = n R 3 Voltage + RT Amperes - Resistance 1 wherein n denotes the number of tubes, where the resistance is equal to the sum R the resistance of the rheostat, RT the of the resistance of the rheostat and the resistance of a single tube. resulting resistance of the parallel-con- See January, 1925 issue of POPULAR RADIO, page nected tubes. 53. 45

www.americanradiohistory.com 46 POPULAR RADft t

2

-100 / 90 1- U V 200 .9= UU 201 i B4 .6= 70 .7 = 60 , 6- 50ui E .5- 401 .4 _ - 30 w w u cc .3 t L = 3 WET CELLS - U U 20114 -- WD 12 3 ORY CELLS -20E Q - 2 WET CELLS w .2 - 2 DRY CELLS u I WET CELL --

I PRY CELL f- IQ .1- - 5 -78 6 5 .05

411 MAKE YOUR CALCULATIONS ON THIS TABLE FIGURE 1: The text of this article tells you just sistance for how to figure out the proper re- the rheostat to employ in radio receiving circuits with various "A" battery voltages. To evaluate equation No. 3 we find (livide the remainder by the number of first, with the aid of equation No. 1, tubes to be used, then add 2 to 3 ohms the total resistance required, then sub- for control of the filament, to get the tract the resistance of a single tube and correct rheostat.

www.americanradiohistory.com A MEASUREMENT CHART FOR RHEOSTATS 47

leo

u0 REQUIRED RHE05TAT 30 40 60 100 1o T I 90 ìài C;RREIIT I 90 \ -7B0 10 - e I. B \-60 20 11111 UI) \ 5 !ME . RHE05TAT 199 \ E 70 -\4 30 \\ cc -3 i'1i1uI o5 UU 2á\ RIME MINI w fi0- 201H 40 cc UU e ó 10 \ WO 12 \s ¢ 50 0 0 "'NROME EMI tn 4- 6à 1",M1E,___ ¢ ó30_ ,,_1,1,,,,,__MINE_ 20 sEll -II= 10 111 1

100

THE SUPPLEMENTARY CHART FIGURE 2: This chart used in conjunction with that in Figure 1, indicates the proper resistances to use for a number of tubes. The text explains in detail just how these charts are used.

For ready calculations, the chart in Then draw a straight line through 110 Figure 1 will eliminate mathematical on scale No. 4 in Figure 2 and UV -199 operations as follows : on scale No. 5 intersecting 60 on scale We have a three -cell storage battery No. 6 ; following horizontally to "4 (6.6 volts) and want to know the rheos- tubes," then vertically to the scale No. 7, tat required for controlling four UV -199 you will find the required rheostat is of tubes connected in parallel. 15 ohms, and adding 3 ohms for control, Connect UV -199 on scale No. 1 with you will have a rheostat of 18 ohms to "3 wet -cells" on scale No. 3. You will suit conditions. find on scale No. 2 the resulting resist- To obtain best results the "character- ance of 110 ohms. istics" of the tubes should be the same.

Another Hoffman Measurement Chart- for the simple calculation of inductance of toroid coils- will appear in a near issue of POPULAR RADIO. Keep these charts for reference in your experiment work.

www.americanradiohistory.com . / / C P 3 S l " G = . c S5 S S S a 1111111111111G 6 5 .3é= ...:.SSS Gae a.i a S r.. a:GaG g . , 11 kijhÎr . a. l. S : : :=G' S_=GS. 1SLGGeaG.. : S. SSS:G9 G. f. l i G. ..:SS. S. .e... e..a:C:e ...e::::S: S . . s . eS a:ea: r l ;.. SS GiSi :0 : a:= C...SS.:G ï G :Si éi C Sa3a r , Ga. : h . . a . e : é:l n Q IIIiiiIIII GS GGrGSG S .G.:S8' i .G S ;S.E = ; : S=S = li SS »e a e SS. $S a = : Ge SG iS . :: .aa 1 : G G GS :a:r S : S? :. GS . . ' . :S S. GC:a..Ga =egC .-.ga. a 1 ::S:SG INN S. s.SS.GmC ...... :. ò zoo SaG Ge:G :S ::. SS. .. ::. S i 1119111111111111111111111 S ° .. 111SS:SS as S G G=:.S rG=B I. 1 S /oo : ...... aSSS S1SS.S 1SSe eSS.:r p . ...g :.::I aa. .::rrr::ir: :.:ra L S . rG 9SGSS=SeSeSGC:em.-..iia ...aa: .. ..p:a. G.a .aS.:.a..G .. G : . . GGGG SI : p: :G:: : :: :: :s z..i.G'C:G182:1104111/1 3S SS aSSa SS: a G 11111114411111111111:1GG.S000aEG' .ErSeSS:.:::=G.: Sa iSeaG. rG: eSee:S: :.:=C.. i:.rG:Ger r .e.i./0 ZO 40 50 %qp DIAL 5E7T/46 IDEAL CAPACITY CURVE FOR THE NEW SLF CONDENSER FIGURE 1: This diagram shows the necessary variation of frequency condenser capacity of a straight line - with the setting of the tuning dial. Notice that at the lower of increase is slow settings the rate but at the higher settings the rate of increase increases greatly.

THE PART THAT YOUR CONDENSER TUNINGPLAYS IN What is the difference between "straight line capacity," "straight line wave- length" and "straight line- frequency" condensers? Just tuning? What how do they affect system gives the best tuning facilities? The answers are this article. in By HERBERT J. HARRIES WHEN KDKA was the only broad- considerable "cussing" at one casting time or station working on a regu- another, mentally or orally, because lar schedule, and tuned he -radio - frequency found that his receiver tuned so broadly circuits were not as popular as they are on the higher frequencies today, (lower wave- a condenser was a condenser and lengths) that separating the it made little multitude of difference whether the plates stations concentrated on the were square first 30 or 40 or circular or what shape divisions of his dials was an impossibility. they were so long as the capacity was Everyone knows that variable. this situation ex- ists, but no one seems to have made In 1925, A.D., a however, with nearly careful analysis as to why it exists. six hundred broadcasting stations sharing Why must we be content with broad the relatively few frequency bands at the tuning on the higher frequencies when the disposal of the Department of Com- same coil and condenser tune "sharp as a merce, the situation is decidedly differ- needle" on 550 to 650 kilocycles ? Is it ent. Between the Atlantic and the Pa- not possible to build a condenser which cific there probably is not a single "BCL" will have more nearly (broadcast uniform tuning -listener) who has not done characteristics ? 48

www.americanradiohistory.com THE PART THAT YOUR CONDENSERS PLAY IN TUNING 49

And the dials most commonly used maximum, the full area of the rotor plates have the 180- degree tuning range cali- is in close relation to an equal area of the brated uniformly from 0 to 100. Is it not stator plates with nothing between them possible to shape the condenser plates so but some thin sheets of the best dielectric that one frequency band of 10 kilocycles known -air. The dielectric losses are ex- will correspond to one degree oh the tremely low, and the 550 kilocycle current dials? In other words, ifWCAE trans- has presented to it a path of very low mitting on 650 kilocycles tunes in at 90, resistance. why can we not make the condensers so As we reduce the capacity, however, that KSD on 550 kilocycles will tune in we reduce the area of the rotor plates that at 100, WHT on 750 kilocycles at 80, is close to the stator plates and likewise W W J on 850 kilocycles at 70 and so on ? reduce the area of the dielectric path Is it possible to do these things ? through the air. Finally, as we continue Let us consider first the matter of to reduce the capacity we reach a point broad tuning at the higher frequencies. where the path through the air consti- Obviously a circuit which tunes sharp- tutes a relatively small portion of the di- ly at one dial setting is not going to tune electric circuit. Consequently, most of broadly at another unless its resistance the current is forced to flow through the has been materially increased. Apparently solid dielectric used to support the plates then, as we reduce the capacity of the and the dielectric losses become exceed- condenser we increase the resistance of ingly high. The resistance at 0 dial set- the resonant circuit. ting may be as high as 10 to 20 times the Suppose we consider it from another resistance at full capacity. point of view. When the capacity is This increase in resistance does not take

.5571 .7571 /.05A /.4571 B / 50 __------. s== -=__: ------:: ., , __ __ _ .. 11111, 1,.1,11,;ï1;;,1== :--__-_o...a ::: : : 1.11111II.II11111111IIII____=á ..;,. __eéie:iw°liúeee= .. 40 __a-a---a- °ú__oa....í-á .i =UMW Ñ11.1AMON1 ... 1:Ì11'1. ÌÌ Ì:ÌÌÌ:ÌÌ ÌÏ ÌÌÌ1ÌÌ 1Í1Ì 11Ìe.1111e1eÌeÌ:M1H u MIN _ÓqÑ:tlp: 11111 IÌ ÌÌÌÌ11ÌÌÌI1111ÌÌ:ÌÌ ÌÌ11Ì110 MEN 1 dtMI111111/111 /--: 1 111 /1/111111111 m11 II 1IMIMf111am1qwnttt11:t i Ill li:iiiiiiiil i i iiiÑi:óúi:di:ÑililBó:ü ° Yll1_111111np11üióp::ñ: 1111111111111 III II lóílil: a..11110 111111111 ÌI .1III Ó:v11011111IN11. á:ióóú::i:Hilñ11oOlenl:li:uunllnunuunnnn1111 i,'i iü{iï;óiiiiliil iiñó:i°®ó:i::pilp OOIIIIIIIpIN11111Hl1u 11111111wE ii111l111111111111111111111111111111111 1 II IL 11111 11 111111 III IIII npNNiliil111d p npilillullu 11111111111111111111111111111 111111111111 u11111111111111111111111 I 1 III 11I.111 1UIIl A III M1.1niillu111u 1Ollnui1luuu lillil111111111111111 11111111111111 II III 1.'11 II 111111111:IIU I !nqluull 11amnnn1lullllu ism IlI u111111u11111111111111111111 II IIIII.1'11I111111I11 111111tnuuuu 1,im/ r T/.Yl ! II4111I I:IIII1111111111111111111111111111 11 I11,1111 9I111 III I II u nn=N1 n1!'S/'////J,,I1:Nt!A IIII11 11111111111111111111111 IIU:111111; IIIII'11111! II n-.Illr`71rr-:1uanI1n11111uu 111111111111111 11 ill n11111 : I III III II II 1111111111111111111111111111M1I nri/,,irSdu1L,IIImQIlluuulllumlH11I1111111 . III 111E11 1 IUNIIIIrnnullu =mme9nae:eemeoeea:a:::a:::u::::u111o1i11II1II1iI1IIIÜl1Ia,11111111111111. Ill uun::m m1e:uueeei ==-OCI:::mmss:rsa:emma:a=u:::::::::::11::::s111Ì1w1ÌÌÌÌÌeÌÌ1Ì:>tÌÌ mynmsa:apnna® n:=1uminu:::»::::I:se»:1a:a::::a1::11111111::il ran Ì1Ì pin Ì ei Ìm1::CECs:MM01:1ax1e11:1 1111111111 III :mé::á::::::::::: m:::::::::: óïi,iiiiii: : r1I::d: :N : { { {{6 :{{ 1 i{ 111111111,11H1 1 1 Iñ{l " unne.:un:1:::::. :::::me1ali61:I II 1i1i1sprsoo:g CU©U:al::n::::m ::::::::adio:::I:II:I:HIIi- iI I I illlli I II I : nnnn u lIIiII :mff::p ú: Ng:i: nCICNIn iiÌiiIiii1I 6111 {11111LII II IIlllIi11iI,nC: 3 __-______,_=_=__ _-=--__-_ - m----__-- - i ------N------_ : - - l._.- - T-e 70 aE.Ems /0 10 30 40 60 80 /00 O .D/AL .5ETT//VG' THIS CURVE SHOWS CAPACITY AGAINST DIAL SETTING FIGURE 2: The values are here plotted on logarithmic co- ordinates. If a simple relation were to exist between the dial setting and the capacity, curve I would be a straight line. This is a proof that the curve is not a simple hyperbolic.

www.americanradiohistory.com 50 POPULAR RADIO

place at a uniform rate by any means. was chosen for no particular reason ex- Down as low as 40. on the dial it may be cept that the scarcely writer is a firm believer in perceptible, but somewhere be- keeping the coil resistance tween down to a rea- 20 and 40, depending upon the sonable figure, and shape that does not, in of the plates and the excellence of general, permit the the use of coils of 300 condenser, it begins to rise quite rap- to 400 millihenries inductance. idly. It is interesting to note that of two The table gives the condensers numerical values of present day design and of the capacity needed equal at each tenth di- excellence of construction, the one vision on the dial to space with the stations uni- circular plates will show the lower formly around it. Perhaps resistance we can visu- at say 20 or 10 on the dial. alize these capacity requirements To maintain a little sharp tuning then, as the more easily by plotting them against capacity of the the condenser is reduced, it dial settings on rectangular co- ordinates, seems apparent that we need only to pro- as is done in Figure 1. It is a hyperbolic vide a low resistance path for the current curve, as the formula from which we at the lower dial settings. cal- That would culated the values for C told it not be so us would difficult if we could manage to be, but it is not a simple hyperbolic mount the plates curve. on air. We can prove this easily by plotting Now let us drop that the consideration un- same values on logarithmic co- ordinates, til later on and give some thought to the as is done in Figure 2. If a simple rela- question of using 100 percent of our dials tion existed between C and the dial set- and having the stations spaced uniformly ting D, curve I would be a straight line. around them. The data given in Table 1 The fact that we get a curve shows will be of assistance. that Assuming that our no such simple relation exists. This tuned circuit contains will a low -loss induc- be considered further later on. tance of 168 microhenries and a variable To digress for a moment, let us see condenser of 500 micro -microfarads ca- what results we would get by using either pacity, the actual tuning capacity needed one of the two types at of condensers most each 100 kilocycle step between 550 commonly used at present, and the circular 1,550 kilocycles has been calculated plate (straight- line -capacity) from the formula type and the square -law (straight -line -wavelength) 1592()0" type. f2 L First, for each type, we must plot a capacity -dial setting curve as in where C = capacity in micro -microfarads, Figure 3 where I, the straight line, is the curve f = frequency in kilocycles, and L = of the circular plate condenser and inductance in microhenries. A condenser II is the curve of the square -law condenser. with a maximum capacity of 500 mmfd. Then by plotting the capacities in Table

TABLE I TABLE II Frequency Inductance Capacity Dial Frequency Capacity kilocycles mh. mmfd. setting kc. mmfd. 8 550 168 500 (D) 650 100 550 500 0.55r 168 358 90 650 (100) 750 168 358 0.65r (90) 269 80 750 269 850 168 209 0.75r (80) 70 850 209 950 168 168 0.85r (70) 60 950 1+68 1050 168 137 0.95r 60) 50 1050 1,37 1150 168 114 1.05r 1250 40 1150 114 1.15r 168 97 30 1250 40) 1350 168 97 1.25r (30) 83 20 1350 83 1450 168 72 1.35r (20) 10 1450 72 1550 168 63 1.45r (10) 0 1550 63 1.55r )

www.americanradiohistory.com THE PART THAT YOUR CONDENSERS PLAY IN TUNING 51

'TM 7lry°1P .0 i úp MHNa.núp..NNNptJpfN. .Ntt..pNpp.LqY.NU.pNppp ; ..ihr; p. Apa !. / S \ / l%77..A..p./7p.NO..M.pp.p.pS'p Ñ...W C... .p.p.N.MMW.L..l%T. ppN.Y...ÑppV.p MÁpp1i mm::::0:.. pfÁÁ . pLL . M.p p....p!N-. yrup..p...... mfl.:I.pmaÄ.1Ñ.1.p....p.p.p. .0....21.::- pÄirÑiióñ Ñut C ...... ÁTNN..° N.uMpY -r w°iA...... p.vN..NpNN. f.N.Ñ1I.NupRi.rÓ.ñ Y ..Ml.ÑtNd Npt p..NÑ. .Npu i p y.p I: Y.p.pñ.p:p..M..Y.p.pÑ..p...r...p...p. NÖA..B..Ñ. : ü:R " Immis r..p:rV.:::..V.1.:Ö...... Ç:6: Ñ..pN.N.a.üpÑÑ WillÑ.p....pp.p.ií.., N...... N- .Vw.Á EH..pN.Npl...... pp.pW...H.,pp....l ..N..:ÑÑ...H Ipt1N1..nCN -A ..p...p..NA.. 0 N %r ...... p....p. .pNM.pp.pp.p...... p.W. .Ñ: ...... 7 ...... Np.p..I -r ri r.r...N.p...... N..p....pp..'..pÑ..N.p.upp...p.p...rrr..rr r ... ..r..fffr.frr..N.f..rrrf.fr...rf.f.f.rm /0 tO 30 40 50 60 70 60 90 /00 D/AL .SETT/NG THE CAPACITY CURVE FOR TWO TYPES OF CONDENSERS FIGURE 3: Curve I shows the capacity variation of a straight line -capacity condenser and curve II shows the capacity variation of a straight line- wavelength condenser.

I against the corresponding dial settings would be so great that the tuning would from Figure 3 we can determine where be broad. The net gain would probably the different stations will come in on the be negative, assuming that a low -loss in- dial. This is done in Figure 4, where curve ductance was used and the 500 mmfd. I is that of the circular plate condenser condenser would probably prove more and curve II is that of the square -law satisfactory, so far as selectivity and sen- condenser. Curve III is added to show sitivity were concerned, even though the what we would get if the frequency bands dial range would be 13 percent smaller. were uniformly .distributed over the 100 Let us make one more comparison be- divisions on the dial. fore we drop the circular plate and An analysis of Figure 4 is quite illumi- square -law condensers from the discus- nating. It shows us that, contrary to the sion. If we could straighten the circular generally accepted belief, the circular edges of the dials out and lay them side plate condenser is to be preferred for this by side we would get a very clear picture particular combination of capacity and of the relative amount of crowding we inductance. Only the lower 13 divi- would experience with each condenser. sions on its dial are unused in covering This has been done, theoretically, in Fig- the broadcasting frequency range whereas ure 5 where the 100 divisions are rep- the lower 35 divisions of the square -law resented as lying in a straight line. The condenser are of no service. number of 10 kilocycle frequency bands We could extend the usefulness of the included within each ten divisions is latter by doubling the inductance and clearly shown, and !the desirability of halving the maximum capacity, that is, the condenser which has the character- by using a 250 mmfd. condenser instead istics pictured in Figure 5 -C is very ap- of one with 500 mmfd. maximum ca- parent. pacity. But in doing so we would just Having satisfied ourselves that our about double the resistance of the coil. theoretical condenser will be much more Also, the resistance of the 250 mmfd. satisfactory than circular plate and condenser below about. 30 on the dial square -law condensers, we now have be-

www.americanradiohistory.com 52 POPULAR RADIO fore us the problem of shaping the plates to design condensers with as low mini- so as to provide those characteristics. mum capacity as could possibly be ob- Figure 1 gives us a picture of the con - tained with the exercise denser of the utmost we propose to design. The maxi- ingenuity. Careful designers mum capacity have will be 500 mmfd. and turned oùt condensers in which the mini- down to 70 or 60 on the dial it must de- mum capacity was less than two percent crease rapidly. As a matter of fact, the of the maximum. A fair figure for the formula tells us it must decrease in in- lowest possible minimum of our con- verse proportion to the square of the denser would be about 10 mmfd. But frequency corresponding to each dial set- Table I shows that our capacity at 0 ting, as given in Table I. dial setting is 63 mmfd. Where on the Now we have another point to con- dial can we put those sider. 53 mmfd. we are It has been customary heretofore "long" ? .N..N.N.N.INgl NN. N NNN._.-1.1Wap -=r. N..N....Y.N..... NNN%\I'W/ .u.T7u7Nr I i. Nq-wN !.NN....r;C.3... .íM\rW 660 Qv..: ii/NiwNif. íiñ '.ÓH NNi NP. N.N ro IN. d . - 4..i%;,..¡r, ..N.NN iN i--. .N. ,ï N\NW... 850 p\ NlNi.NN.NN.N..NN üi...iiúiiiN.N.mom N W.N %ENIUMMEMMIftimmINMOMM NNiaNiái N NNppWN..N NNÑtl 112.11=:12 SWUM ...... -.... YN - MAIM i °N..i MUMi NNiiiiMO . . .. . NmiWYi HÚN....MNUYN.N..NN\ - . . NNNy.N .. . N.ÑNW%.Nui.... /250 ú..af M NNN . ! ::.Ó N... .N...... rv;;raA.4IA.7'r.iNir;oti.i.Npp.N.N....0. a: ._ , frv N. .=N..... t eNáíNuq;i/NN.áiíä";.,^s-aNNNIV.or r7N.N ¡, I,, ARID ru.nnVs1 M.rM+- iN "A (,t ,a rr4 ;.;wrv.0 ranii_.rii =NNNNN /350 .NNNNNNNN NUMEÄLA Maim YWNNN1WNNNNWN/ N.m t.NO MM NN.N.Nw.NWNNN. . NN. N:..... 'AMMER . N.. NNN.. .N....INl.arl= ..%WMiNN MMMMM =MEN Ñ.N ./. YIN=Emma N MAaWWNdp.. r .-MÑIWH¡r¡. /4510 N..N..N\..NNN.\.W.\N.p....NNN.. N..... _ .. ..W..NN.W.W\...WNI.NN..N.... .N:N.N \ .N. Rau NW 11115. Ma ..NN..N. . ..N....pp \.WN...N.\N.NN..N.NNN. N.NN...Ñ.NÑ.uNM....N.. MpNiiiiN...... i/pp . .N7.m..N..yy...M.ui.NN.uI NuM.pNN\uN .ÑI.N .NN. N.NNN.N.N\.....\NN....N..M....N.Ä..Ó.. /550 NW..M',\...W N..N...... W.\..W.N..fWm ür . \\\\NM\.\\N\.N\\NBo.\.\\a O /0 40 50 60 49//7L SETT/NG A TUNING CURVE FOR THREE CONDENSERS FIGURE 4: Curve I is the frequency against dial- setting condenser. For curve for the straight line -capacity this combination of capacity and inductance, the denser is to be preferred straight line -capacity con- to the straight line- wavelength condenser as there are unused divisions on the dial setting as only thirteen against thirty -five divisions in the case of the latter.

www.americanradiohistory.com i THE PART THAT YOUR CONDENSERS PLAY IN TUNING 33 AAAÄÁÁÁÁÁÁ

III' I'l'l'I'l'I'I`I ` l 0 /0 20 30 40 50 60 70 d0 90 /00 FIGURE 5A: This drawing shows the number of ten kilocycle hands included in each ten degrees on the dial for curve I in Figure 4.

0 0 0 /7 29 /B /3 /I 7 5 AAAAAAAAAA

0 /0 ?0 30 40 50 60 70 60 .90 /00 FIGURE 5B: In this diagram is shown the number of ten kilocycle bands included in each ten divisions for curve II in Figure 4.

/0 10 /0 /0 /O /0 /0 /0 /0 /0 AAAAAAAAAA

0 /0 20 30 40 50 60 70 QO 90 /00 IDEAL TUNING DISTRIBUTION FIGURE 5C: Notice that the frequencies are evenly distributed over the entire dial setting, so that every ten division covers a frequency range of 100 kilocycles. This is true of the curve III which is shown in Figure 4, for a straight line frequency condenser.

Why put them on the dial at all ? Just Now let us take a look at Figure 6 -a because it has been customary for the which shows us the approximate shape range of a condenser to be from the our rotor plates will assume. \Vhat form maximum to the lowest possible mini- the stator plates take is immaterial so long mum is not a good reason for continuing as we can provide convenient mounting the custom. And since we do not need means. those 53 mmfd. as variable capacity for We have decided that a part of each tuning why not leave them in the con- rotor plate will be a circle. Consequently, denser as a fixed capacity. This may no matter what the dial setting, the pro- sound like rank heresy to those who have jection of the circle upon the stator plates, exerted every effort to get a low mini- shown shaded in Figure 6 -b, will be in- mum, but to the writer it sounds logical. variable and great enough to provide our And somewhere back there we needed 53 mmfd. All we have left to do now is a low resistance path at low dial settings to determine the exact shape of the rotor so the current would not be forced plates which will give us the capacity through the solid dielectric. Here is curve in Figure 1. The approximate where we get it. We just take those 53 shape is shown dotted in Figure 6 -a and mmfd., spread them out over some cir- Figure 6 -b. cular brass or aluminum plates, provide Determining the equation of the bound- some thin sheets of perfectly good air ary curve would not be difficult if a and there we are ! simple relation existed between any value

www.americanradiohistory.com 5`I POPULAR RADIO of capacity and the corresponding dial which do not check at all with setting. - But we proved by curve the values Figure I in we have listed in Table I. 2 that no simple relation exists. This We can discrepancy is due to the fact, as consider this in another way. we Our formula stated before, that no simple relation exists between C and the corresponding 159200" setting C D. But the boundary curve is a f=L hyperbolic spiral, from our original f or- can also be written mula, so the formula

C a f_ C = D2 where a, == 1592002/L. would Also, since we be true if D were properly ex- wish to distribute pressed. the frequency bands If, instead of D, we use uniformly over other an- the dial, we should be designation, o, for the dial setting able to write and in addition have the dial read back- wards f =a2D for purposes of calculation, we can give values to O where- a9 is some constant. for which the formula Then we will be true. We therefore could substitute a2D for f in the preced- prepare Table ing formula and get II and use it instead of Table I. We now al a find that whereas our previous 2 a1 formula a2D2 =D2 = / a2) f =aD But this is not true because the pre- ceding equation is not true. was true for only one value of D not and Suppose we check the latter against for any other, the corresponding for- Table I. When D - 100, C = 500, then mula f =k20 500= and a =5x106 is true for all values of 6 listed in Table Using II. Substituting other values of 1.) we get this expression for f we now have when D = 70, C = 1020 D =40, C =3125 k D = 10, C = 500000 C= 02

111 ooamroonooo/rIsúumnmogHyCCriC ri- moms om YYYN WrHNNrY rrorM/YHOro i-.-TL...._. nrNCÑgnHm/pnrnrC° VpHrn// _ I- amorHrMrrCNoNamHrrn n ://rCCl/:L on/orgrCrHC/r rr//YrrYYrJrrH1/41Wn/rrrH/ i 1CCC ÌF/p% rn/úCÑ ,--,; *`T onooCrMrooCrrH/oqro CCCCCCCHYCCCrr,rrr ' ' ' rm_ C//orHn r/rYr/n/CCrYO/HYOorHrIMFHr/l\rrn/ áCi/i,riúCCCV Vm iC/C/° MOM iüiC°CÚÜiHrCriCCCrrCHCCC oY //anY-r //o/MM// UWE roo%rr.cy/rrH\NrrNK.\rr`TNZ.u/UHn/NU/Nt,rOA rier N /m/rM íMr/Hrrr/rrrHUrn/Ì V-71o/NruWLH /N/HY HooamCHnorramroamooR/ÍoY1M.CjC\/\C-CrrrCCr.\CC\rRroHroronNroorJls-HMI-ori ViiiiCCi7/Crrr11 Ci iIa:/// r Nnr/lrNU.`.MYHrrr ..n'CCCCCCC :CCCCCCCCCO:CCCCCC: WNC Nrr/noNnrrorro/:-°ñ/:;rCC:CCCCnHOOtCI\MO Y'Ht or IMO /aV///Hlr/HrnY//nn.\HLI/n///%Yn/nM/rMr/rH nrflIRIVr \'rJr p nHor/rroNn/r 7/ooam\_ rHNOH/oHn\'.Vn\\M\ nI / 79i//HCCCCCnrr/n/ /r000o/HoooMror/oMnoonrrorCC MrH/! CRrrrHr/\Nrrrrr/HHorn\rNU_/H,N/I/7 tuoolA7 {yJH r/NMrp Mroororo 0000roCCorVJo/ramrMO//VHrÍ\\CC, , ffláú /MNr/p/r/Hr MUooNC:MN rNOr/! Slr./0000n/r///roNroamVoono/Hr//Mr/\nr//I.\/\/NrI/\/711dRHy rMtrC///N/ mg".nnrr /pprrnr\r`/\Ir1/r7'1 1 oo/rrnnNrti;/...N ]71 NNa :i:::CCq.i.Ci:ïúú H/ramamQ////YM///I mrr.irild/°i NYId.Ll jCC/rM/CCC //Y r á rrramr 1r//!1r//pl/" M//r/amrpn /CCra/IIp4 ' ////CHp::r.r..1..u..uLu.uu.u.u.w:::...m..uu..w NnrnooYCCHYnrCYrH N rNo o 000amoH\loY :r.i.ri:r.r.Lr_____rnr,ir//rrYY Y Y rn wúMírrrru7B/Mr/amOilo/ooHCr/o /No: AY M YYYYMYYMAY M __sum/ THE SHAPE OF THE FIGURE ROTOR SECTION 6A : The correct curve for the rotor plate shape for a straight line frequency condenser that will give the variation of capacity variable as shown in Figure 1 and that the tuning characteristics shown in will give curve III in Figure 4. _

www.americanradiohistory.com THE PART THAT YOUR CONDENSERS PLAY IN TUNING 35 and we find that this is true for any value '-.,, Q of O given in the table, for when values . of C are plotted on logarithmic co -ordi- . nates against the corresponding values of ` e we get the straight line marked curve ! \ II in Figure 2. \ I f we had not decided that part of each ` \ i rotor plate would he a circle, the outline i of the plate could now he expressed i i I I lz R , = r v fl But we have to take the circle into con- sideration, as well as the semi- circle cut- out of the stator plates to accommodate the shaft, so our final formula becomes ANOTHER DRAWING OF THE ROTOR SECTION R,° -Rz+Rs FIGURE 6B: The projection of the circular part of V the rotor plates upon the stator plates. This area will be invariable, as the condenser is rotated and where R, = the radius of the hyperbolic should be great enough to provide the 53 mmfd. shunt capacity that should be spread out over the section, R2 = the radius of the circular whole dial setting. section, and R., = the radius of the semi- circle cut out of the stator plates. line tuning characteristic but it would be We can now replace our specially -cali- inappreciable, in all probability, over a brated, backward- reading dial by a stand- range of plus or minus ten percent. ard one reading 0 to 100 and if our coil In conclusion, it should be noted that is of the proper inductance we will find a square -law condenser should be de- the stations between 550 and 1,550 kilo- signed to cover a pre -determined wave- cycles uni f ormly distributed over 10C length range, and an inverse- square -law percent of our dial, as shown by curve condenser should be designed to cover a III, Figure 4 and in Figure 5 -c. Also, pre -determined frequency range, which we have taken advantage of a fact inci- corresponds in each case to the broad- dent to the design of inverse -square -law cast range. I f this is not done, the broad- condensers, whereby they must be designed cast range, in which probably 95 percent with some pre -determined minimum ca- or more of the users of this class of ap- pacity, by making that minimum more paratus are interested, will be concen- than six times its customary value and trated on 60 to 85 percent of the dial and using it to provide a low resistance path the remainder will be useless. Keeping for the current at low dial settings. this in mind, it is obvious that if we de- In the foregoing we have not taken into sign the condenser so as to get the lowest consideration the capacity of the coil. minimum possible, in line with present This, of course, would affect the radius practice, the tuning range of the con- of the circular portion of the plate and denser will be much greater than is would have to be considered in determin- needed. To get the full benefit of the 100 ing suitable dimensions. Also, it will be divisions on our dials we must provide a apparent to the thoughtful reader that a pre- determined minimum which is greatly condenser of this type must be used with in excess of present practice! This is no a definite coil if absolutely straight - real disadvantage for the high minimum line characteristics are to be maintained. provides a low resistance path for the The writer has not determined to exactly current at low dial settings and thus re- what extent a certain percentage variation duces the resistance of the tuned circuit in inductance would affect the straight- by a very considerable amount.

www.americanradiohistory.com Ä42Y :54-45k '1'!IE TIIEC)RETICAL CIRCUIT DIAGRAM l' IGum:. 1: This drawing shows the general circuit connections for the various instruments that go to make up the receiver. Simple "How -to- Build" Articles for Beginners No. 14

-low to build a one -tube regenerative receiver for use with the new UX -199 tube By LAURENCE M. COCKADAY

COST OF PARTS : Not nt -ore than $19.00 APPROXIMATE RANGE : 1,000 miles HERE ARE TIIE ITEMS FROM WHICH THE LABORATORY MODEL WAS BUILT - A, B and primary, secondary C- and tickler H- Carter "Imp" rheostat, 25 ohms; coils of Aero coil three -circuit tuner; I- Sangamo mica Continental fixed condenser, .002 mid.; D- Separator (variable con- J--composition panel, 7 by 12 denser), .0005 mfd.; inches; K- hardwood baseboard, 7 by 10 inches; E- Sangamo fixed condenser, .00025 mfd.; Seven Eby binding posts; F- Electrad grid -leak, 3 megohms; Two large Century dials. G-- Pacent socket No. 82 for UX -199 tube;

THE latest addition to the series of nucleus of a receiver that may be added simple sets for the beginner is to from time to time to make a really fine more than just an ordinary dry -cell set. loudspeaker set. It operates directly It was especially designed to be used with from three dry -cell batteries for the "A" the new UX -199 for quality reception battery and one 22/ -volt or 45 -volt "B" combined with selectivity and long dis- battery. tance- getting ability. This receiver will The set is regenerative and the coupler be found to he an easily operated set and used gives a nice control of the regenera- will enable the beginner to tune out the tion. The secondary coupling to the an- local stations and bring in the distant tenna is controlled by a semi -variable ones on headphones. It uses finely de- coil A shown in Figure 4. signed and manufactured apparatus . The tickler coil is controlled by the dial throughout and may be considered the C which is attached to the coil C as shown 56

www.americanradiohistory.com SIMPLE "HOW -TO- BUILD" ARTICLES FOR BEGINNERS 57

t f i t Qa A[ !/1( ió° . ó

VIEW OF THE PANEL FROM THE FRONT FIGURE 2: This picture gives the general arrangement of the front panel with the two large dials, the small rheostat dial and the seven binding posts mounted in the correct positions.

fi /-

7' -

r 4., ..Í- //" . /2" THE DRILLING PLAN FOR THE PANEL FIGURE 3: In this drawing are shown the exact locations for the holes that are to be drilled in the panel for mounting the instruments and the binding posts. The holes outlined with a double circle should be countersunk.

www.americanradiohistory.com 58 POPULAR R_1llIO k in Figure 2, which is the front view of spacing for all of the holes that are used the set. to mount the instruments and the bind- The unit that is described here was ing posts. built and carefully tested in the POPULAR Then, mount the instruments in their RADIO LABORATORY. The construction of correct positions on the panel and base- the set is simple and the completed re- board as shown in Figures 4 and 5. ceiver, as stated before, is easy to operate. When this is done, wire up the instru- Take this issue of the magazine to a ments with standard, round bus wire, as radio store and ask the dealer to give you indicated in Figures 1 and 5. exactly the same parts as those that are When you have finished wiring up con- included in the list at the beginning of nect the antenna, ground and batteries this article. (see Figure 1) to the binding posts and Then take the parts home and drill the then you are ready to listen in. panel J (as shown in Figure 3) which To tune the receiver all that is neces- gives the ,ize of the panel and the correct sary is to revolve the dial D, with the

VIEW OF THE SET FROM THE REAR FIGURE 4: Here are shown the various instruments mounted on the back of the panel and on the sub -base with the connecting wires in place.

www.americanradiohistory.com SIMPLE "HOW -TO- BUILD" ARTICLES FOR BEGINNERS 59

02

THE PICTURE WIRING DIAGRAM FIGURE 5: In this diagram the exact way to run the wires is shown. The upper rectangle represents the panel and on it are shown the instruments which are drawn in about their relative positions. The lower rectangle represents the baseboard and on it are shown the socket and the grid -leak and condenser. dial C set at a rather low value and the The correct type of antenna to use small knob H turned so that the filament with this receiver is a single wire of of the vacuum -tube lights with the correct about 100 to 150 feet in length. brilliancy. If the set is built correctly as shown When a signal is tuned in, the dial C in the pictures and diagrams, the oper- may be adjusted so that the signal comes ator, after he becomes familiar with the in loudest and clearest. Some other small tuning, will find that he will get excep- adjustments may then be made by the tionally good reception on the headphones small dial H and the dial D for final from stations up to an average distance settings. of about 1,000 miles.

www.americanradiohistory.com Handy Tools for Radio Fans: No. 9

From a photograph wade tor POPULAR RADIO

THE HAND DRILL .4 useful tool for preparing panels THE radio experimenter who likes to build his own set will find a drill of this type nearly indispensable when he comes to the point of drilling the panel to mount his instruments. The drill is composed of a long handle frame to which is attached a large and small beveled gear. A crank is attached to the large gear while the smaller is fastened to a shaft that carries a chuck. The chuck is adjustable to fit a large number of different sized drills. The preceding suggestions in titis series were SIDE- CUTTING PLIERS, SCREW -DRIVERS, THE HYDROMETER, THE BATTERY - TESTING VOLTMETER, THE FILE, THE JACKKNIFE, nip ELECTRIC SOLDERING IRON and THE SOCKET WRENCH.

60

www.americanradiohistory.com IN THE WORLD'S LABORATORIES

CONDUCTED BY DR. E. E. FREE

Sun Spots May Bother Radio the low, except, of course, in the immediate vicinity of the station.* ' THE sun is growing spotted again. During These conclusions seem to have surprised the past fall as many as fifteen spots were some- many of the listeners, although there is no reason times visible at one time and some of these for such surprise. Both results are quite in spots were more than twenty thousand miles in accord with the best present -day theories of radio diameter. Such spots are believed to be evi- wave propagation. Fading is believed to be due dences of great storms on the sun. They are to atmospheric phenomena, mainly the existence invariably accompanied by vast magnetic and movement of areas of different ionization disturbances, which disturbances frequently in the upper air. Such effects ought to apply reach the earth and manifest themselves by equally to a wave of any power, so long as its alterations in the direction of the magnetic wavelength is unaltered. Similarly with inter- compass, by strong stray currents in telegraph ference, the intensity of any wave falls off so lines and the like. rapidly with increasing distance from the trans- The spottedness of the sun is known to vary mitter that a "blanketing" effect from a super- according to a more or less regular cycle with a power station would not be expected to extend period of approximately eleven years. The more than a very few miles from the antenna. minimum of this sun -spot cycle was passed in On the other hand, the distance range at which a 1923 and the number and activity of the spots station is audible above the static level ought to are now increasing. A recent newspaper inter- be approximately proportional to the power view with Dr. J. A. Fleming, of the Department used, and this seems to have been the case with of Terrestrial Magnetism of the Carnegie Insti- last summer's tests. The continued tests made tution of Washington,* warns the public to since then and which are still in progress will expect magnetic disturbances whenever the num- lead, doubtless, to still more exact information. ber of sun spots is great. It is probable that the effects of the sun spots on the earth include, also, a share in the creation of static, so we may Up and Down Movement of the perhaps expect more static this year than last. Heaviside Layer Possibly there will be a maximum of static, coinciding with the maximum of sun -spot THAT the famous Heaviside Layer, instead of activity which is due in 1929. being a part of the atmosphere lying at a reason- ably constant height above the earth's surface, is really located at an extremely variable height, much higher at night than in the daytime and Super -power and Fading much higher in winter than in summer, is the LAST summer's tests of super -power broadcast- interesting conclusion derived from the recent ing, culminating in the alternative transmissions high- frequency transmission tests conducted from WGY on fifty kilowatts and on ordinary co- operativelybythe Radio Division of the Naval power, have definitely established two conclu- Research Laboratory, at Bellevue, D. C., and sions. First, super -power does not cure fading; the American Radio Relay League. Prelimi- reporting that the fading was many observers * The results of the tests are reported in a statement quite as noticeable on the high power as on the from the United States Bureau of Standards, published low. Second, the degree of interference on the in the New York Times for September 13. 1925, and in on the General Electric Review (Schenectady, N. Y.), vol. 28. high power was not noticeably greater than page 720 (October, 1925). Some additional data re- leased by the engineers of WGY were published in the * Released through Science Service, Washington. D. C., Radio Section of the New York Herald- Tribune for Octo- October 20, 1925. ber 4. 1925. 1

www.americanradiohistory.com 62 POPULAR RADIO

nary results, together with a tentative theory of high- of the air, well up in the atmosphere, in which frequency wave propagation, are reported layer the number of ionizedair by Dr. A. Hoyt Taylor and Dr. atoms is unusually E. O. Hulburt, high. These ions, you remember, are merely of the Naval laboratory.* atoms of oxygen or Newspaper accounts, nitrogen or other gases which released by Secretary have lost one electron each, so Wilbur, of the Navy, on August 19, that the atom 1925, and comes to possess a positive electric charge. At printed in full in the New York Times of August the same time the lost electrons 20, 1925, as well as in other are set free, so newspapers, referred that the space in the Heaviside region contains to the experiments as proving the existence of a a relatively large number "radio roof" around of loose negative elec- the world. Of course, the trons as well as a relatively large number experiments prove nothing of the sort. In so far positive of as ions. These ions and electrons bend a "radio roof" exists it is merely another name the radio waves, so for the well -known that a wave ascending from a Heaviside Layer. The ex- transmitting station into the upper atmosphere periments are, however, of very real importance tends to be bent downward and, presumably, Dr. Taylor and when it enters the Dr. Huir art Heaviside region. If it is bent sufficiently it were not responsible for the newspaper accounts. may even return By "high- frequency" to the surface of the earth. waves Dr. Taylor and It is this bending, Dr. Taylor and Dr. Hulburt Dr. Hulburt mean the short -wavelength waves, believe, which accounts below 100 meters, for the phenomenon of which are now coming rapidly "skipped distance," the frequently-repeated into use. The tests involved waves from longer ob- than servation that short radio waves are perceptible this 100 -meter limit down to some as short close to the transmitter and as 18 meters. The theory developed also far away, but is essen- not in an intermediate zone. The waves per- tially an extension of the ionization hypotheses ceived far elaborated recently away are reflected waves, returned to by Appleton, Nichols and the earth's surface from the Heaviside Schelleng, Alexanderson and others.t The new In Layer. contributions certain instances it is possible, they think, of the present paper are essentially for a back- and -forth reflection between two. First is the evidence for the upward the earth and and the Heaviside Layer to be repeated several downward movement of the Heaviside Layer times, so that the transmitting from time to time. Second, there is station will be evidence surrounded by successive circular zones of recep- and an explanation concerning the interesting tion and of silence. phenomenon of "skipped distance" with these These shorter phenomena were already known, more waves. or less clearly, with the longer Radio experts no longer regard the Heaviside waves commonly used in broadcasting. By testing them with Layer as any mirror -like thing which actually shorter waves it has reflects the radio waves. been possible to formulate It is merely a layer mathematical relations between the width "skipped of the * "Wave Propagation at High Frequencies," by A. distance" band, the wavelength and the Hoyt Taylor and E. O. Hulburt. QST (Hartford, height and properties of the supposed ionized Conn.), vol. 9, number 10, pages 12-21 (October, 1925). zone in the Heaviside region. The substance of the paper was read before the Inter- Tests made on national Convention of the American Radio Relay different short wavelengths showed differences in League, at Chicago, last summer. A brief abstract of the width and position of the "skipped distance" the theoretical results, by Dr. Taylor and Dr. Hulburt, band. These results varied, appeared in Science (Lancaster, Pa.), vol. 62, pages also, with the hour 183 -184 (August 21, 1925). of the day and with the season. Hence possibility the f For a general account of these theories see "How of reaching conclusions as to the the Air Affects Radio," POPULAR RADIO, vol. 8, pages different heights of the ionized region at different 199 -206 (September, 1925). times.

A MAY/J/DE LA YfR Ar 200 MaEs J41MJM/IfAOM Ar 'AT MON FREgUEM(

NGr/siLeUrfRAr200NiLEs .'- JRItW41TgNMMOOERAELYN/lE{YEMï. \

' G NEAY/siOE 4YEg Ar.fDOIAlQ :RAAC%/4tpMAryErrR/(MrRLVUEACY-\ k\

Reproduced from QST REPEATED REFLECTIONS FROM THE HEAVISIDE LAYER Rays of radio waves from a short -wavelength transmitter may be reflected back and forth between the Heaviside Layer and the ground, thus producing successive and non -interference. bands of interference These bands vary with the average height of the Heaviside region.

www.americanradiohistory.com IN TILL WORLD'S LABOR \i ORIES 63

From a drawing for POPULAR RAmo by Arthur Merrick I- Itl \\' 'TIE HEAVISIDE LAYER CAN CAUSE ZtiNES OF SILENCE Close to the transmitter there is a zone in which the signal is heard by the direct path. At a little greater distance these direct waves are so absorbed as to be inaudible in ordinary re- ceivers. Ala still greater distance a wave reflected .from the Heaviside Laver is picked up. The transmission may be received cl early in this outer zone, shown by shading on the map, although no signal is detected in the intermediate zone of silence.

This height varies, Dr. Taylor and Dr. 1-101- vestigation the short waves below 100 meters hurt believe, between limits which may he as are proving, as predicted long ago by POPULAR wide as 500 miles and 100 miles above the earth's RADIO to be the most effective tool which surface. Sunlight increases ionization in the radio science has vet obtained. lower air, thus lowering the position of the Heavi- side region. This is why the Laver is lower in the daytime than at night. If information concerning the propagation of Using Two Antennas for radio waves in the upper and lower levels of the Directional Reception atmosphere continues to accumulate for a few months more as rapidly as it has during the past THERE can he little doubt that one of the year we will he in position soon to write a com- features of the perfect system of radio recep- plete theory of radio transmission for all wave- tion-if we ever obtain such a system -will be lengths, all hours and all seasons; a theory which the possibility of directional reception; a re- will take account of all our present mysteries of ceiver which will receive with full strength the fading, dead spots and the like. And in this in- waves arriving from one direction while not

www.americanradiohistory.com 64 POPULAR RADIO

receiving waves from any other direction. an ingenious system of attaching two loop anten- There would be two advantages in this. One nas to a movable frame, so that the plane con- is the easy elimination of interference from other taining the two loops could be rotated to ob- transmitting stations of nearly the same wave- tain a directional effect.t But the most ex- length. The other and more important advan- tensive experiments on the two -antenna system tage is the substantial elimination of static. also called the "spaced antenna" or "spaced- As was pointed out by Professor E. M. Terry aerial" system -that have come to light are over a year ago,* most of the static comes from those conducted by the Marconi Company, in certain limited points of the compass. If a England, under the direction of the well-known receiver can be directed to avoid these static radio engineer Mr. C. S. Franklin. With in- sources the reception will be substantially clearer. terruptions, these experiments have been in That certain types of antennas possess direc- progress since 1913. Certain features of the tional properties has been known since the very results, and especially a method of recording and beginnings of radio. It has long been known, evaluating them, are described in a recent article too, that a system of two antennas, connected by Mr. E. Green. $ to the same receiving circuit, may be made to A simple vertical antenna of the usual type take on a high degree of directional sensitivity. has almost no directional properties; waves But practical application has lagged. Professor from all directions are received almost equally Terry used two antennas in his directional static well. An ordinary closed loop antenna has a work just quoted. Also, Mr. H. T. Friis of the certain degree of directional response. Its sen- Bell Telephone Laboratories, reported recently sitivity is substantially higher for waves coming from either * "Tracing Static to Its Lair," by Earle M. Terry, of the two opposite directions in the POPULAR RADIO, vol. 6, pages 342 -349 (October, 1924). plane of the loop than for waves at right angles to these. A combination of a vertical antenna and a loop can be so arranged that the system as a whole has unidirectional properties; that is, it receives best from one of the directions in the xv plane of the loop and almost not at all from the opposite direction. It was such a combination which was used by Professor Terry. Instead of this combination of a vertical antenna and a loop, two loops may be used. The distance between these loops may be varied, being adjusted to a known fraction of the wave- length being received, usually one - sixth. The `iIlll- relative pick-up of the two loops may be varied, by altering the sizes 11 of the loops or otherwise. ro Receiver The position of the plane of the two loops may be varied by revolving them around a common center, as was done by Mr. Friis. The individual planes of the two loops may be altered by rotating them individually, as is done for the single receiving loop of the radio compass. Finally, the phase -angle of the re- ceived waves from the two antennas may be altered by a phase- changer, thus making the two waves any desired degree out of phase with each other. It is obvious that these manifold possibilities of varying the relation of the two antennas to each other put into the hands of the radio engineer a large number of different reception conditions. Many of these have been worked out in the English experiments. Some have been found quite useful in practice; especially, it appears, a combination of two loops each of which can be rotated independently about its own vertical axis. For any such system it is possible to con- struct what is called a polar diagram, which is a chart showing just how the reception character- istics of Reproduced from Experimental Wireless the antenna system vary with direction. Some of these diagrams are reproduced here- POLAR DIAGRAMS FOR RECEIVING with. They may be thought of as constructed ANTENNAS by drawing outward in each direction from the The top diagram shows that a vertical wire receives equally well from all directions. The middle dia- t "New Antenna System Reduces Static," this Depart- gram shows the two- direction reception of a loop. ment of POPULAR RADIO, September, 1925, pages 280 -281. bottom # "The Polar Curves of Reception for Spaced The diagram shows the combined reception Systems," Aerial of a loop and a wire, the heart- shaped by E. Green. Ex ersmenlal Wireless and The curve indi- Wireless Engineer (London), vol. 2, pages 828 -837 cating the combination of the other two. (October, 1925.).

www.americanradiohistory.com IN THE WORLD'S LABORATORIES 65

From a photograph made especially for POPULAR RADIO MEASURING THE SHORTEST ETHER WAVES FROM RADIUM With this apparatus, Professor Skobeltzyn, of Leningrad, has measured the effective wave- length of ether waves so short that over one hundred trillions of them are necessary to equal the length of one ordinary radio wave. The rays are used to set free electrons in the chamber just at Professor Skobeltzyn's left and the paths of these electrons in a magnetic field are photographed. point of reception, a line the length of which is San Francisco. You would have to take some proportional to the intensity of reception in that seven million steps. Now imagine an ant direction. The polar curves reproduced are walking the same distance. He would take then constructed by connecting the outer ends many more steps. But if one of the ant's steps of these directed lines. While the use of these corresponded to one of the shortest ether waves polar diagrams is by no means new in radio and if he had to walk the length of one ordinary engineering, the present paper of Mr. Green is broadcasting wave, his journey would last not the most comprehensive account which has merely from New York to San Francisco but appeared so far on the use and construction of fifty times around the earth. So tremendous is such diagrams for two -antenna reception sys- the difference between our familiar radio waves tems. and these shortest ether waves which scientists get from radium. The gamma rays are far too short to be Measuring the Shortest Ether measured by any of the methods used for Waves measuring the wavelengths of radio waves or of light. They are too short, even, to be measured THE shortest ether waves so far detected by by the çrystal methods used to measure X rays. any method are the so- called gamma rays given The gamma rays must be studied by indirect off by radium and other radioactive materials. methods. One of the most successful of these These rays are still shorter than the waves of methods has been described recently by Professor the X rays, although the two ranges overlap D. Skobeltzyn of the Department of Physics at somewhat; the shortest X rays produced from the Polytechnic Institute of Leningrad, Russia.* X -ray tubes being shorter than some of the As several investigators have done before him, longer gamma rays from radium. The shortest Professor Skobeltzyn makes use of the fact that gamma rays are, however, substantially shorter when the gamma rays strike against matter they than any other known form of radiation. They sometimes set free electrons, just as light rays are believed to have a wavelength of only one do in the photoelectric cell. five -hundred -billionth of a meter. The speed of these freed electrons depends, These waves are less than one hundred - it is believed, on the wavelength of the gamma thousandth of the wavelength of the shortest rays which called them forth. Accordingly, waves of visible light. As compared with radio Professor Skobeltzyn exposes these freed elec- waves the discrepancy is still greater. In the trons to a magnetic field and measures the degree length of one ordinary broadcasting wave 300 meters long, there would be approximately 150,000 * "The Effective Wavelength of Gamma Rays," by billions of these shortest gamma-ray waves. D. Skobeltzyn. Nature (London), vol. 116, pages 206. Imagine yourself walking from New York to 207 (August 8, 1925).

www.americanradiohistory.com 66 POPULAR RADIO

to which this field bends their paths. From this the voltage. Here, too, a ballast resistor will he deduces their speeds, and thence the wave- help. The device operates, in length of the fact, like an elec- gamma rays which freed them. tric governor, keeping the current in a circuit By this method he reaches the wavelength of constant much as an engine one five -hundred- governor keeps the billionth of a meter already flywheel at a constant speed even though the mentioned, a value which accords quite well steam pressure may vary. with estimates of the wavelength of these The ballast resistor consists of an iron wire in shortest waves made by other experimenters an atmosphere of hydrogen. using different methods. Its peculiar prop- erties depend on the relations of the iron and the hydrogen, respectively, to the temperature of the Hydrogen Atoms Operate wire. As current passes through the wire the wire becomes hotter, just as any conductor will Useful Accessory do. This change of temperature changes the electric resistance of the wire, which is also some- A SCIENTIFIC device which deserves more atten- thing that happens tion from radio experimenters than it has yet with the majority of conduc- received tors. In the case of iron wire, it happens that a is the "ballast resistor," an instrument rise of temperature which serves to hold an electric current approxi- increases the resistance (at mately constant in spite ordinary temperature ranges) so that relatively of a considerable varia- less current will tion of the impressed voltage. Suppose, for flow. All this is quite usual. example, Wires of most metals behave in the same way. that you wish to charge a storage bat - The cry at a constant rate from peculiarities come in with the hydrogen. a power main the A hot wire in an voltage of which is quite variable. A ballast atmosphere of any gas loses resistor heat to the gas. Gas atoms hit against the will help you to do it. Suppose that you acquire wire, wish to operate an electric some additional energy from it and move lamp at constant in- away. This cools tensity in spite of some up or down variations of the wire. The rate of this cooling depends on the nature of the gas atoms, on the gas pressure and on the difference of temperature between the wire and the gas. In the ballast resistor the hydrogen atoms behave in this same way. When current is passing the iron wire is hot. The hydrogen atoms cool it, removing the heat produced continually by the electric current. Now suppose that the voltage applied to the iron wire increases. Momentarily more current will flow. This will make the wire a little hotter. Two things then happen. First, the resistance of the wire increases, since it has become a little hotter. At the same time, the amount of heat lost from the wire to the hydrogen atoms in- creases, thus slightly cooling the wire. By a proper choice of the size and length of the iron wire and of the pressure of hydrogen in the tube, it is possible so to adjust these two changes that the increase in the resistance of the wire just compensates for the increase in the voltage, thus passing the same current as before. Ballast resistors must be designed, of course, for the particular current and voltage -range on which they are desired to operate. Mr. H. A. Jones, of the Research Laboratory of the General Electric Company, has computed recently the necessary formulas and tables. Experimenters desiring to make use of the device will find full and practical information in Mr. Jones' paper.* An Electrolytic Theory of Crystal Detectors THE action of the familiar crystal detector is still a good deal of a mystery. What happens is that the alternating current in the General Electric radio -frequency part of a receiver passes the crystal in one direction, TWO BALLAST RESISTORS but not in the other. The crystal acts as a one -way valve for the Both consist of iron wire in an atmosphere of hydrogen. In one the iron filament is coiled, in * "The Ballast Resistor in Practice," by H. A. Jones, the other it is merely crinkled. It dare not be General Electric Review (Schenectady, N. Y.), vol. 28, drawn tight because of its expansion and pages 329 -335 (May, 1925), and "The Theory and contrac- Design of Ballast Resistors," same author and publication, tion with temperature. pages 650 -659 (September, 1925).

www.americanradiohistory.com 1 IN THE WORLD'S LABORATORIES 67

General Electric THE CONSTANT -CURRENT BALLAST RESISTOR Mr. H. A. Jones is holding one of the ballast resistor tubes in his hand. Another is in- serted in the set -up on the table. One of these resistor tubes will hold the current through it at an approximately constant value in spite of considerable variations of the impressed voltage. electrons. Everyone knows this. What no The lead atoms accumulate, he believes, at one knows is why the crystal acts this way. the point where the cat -whisker touches the Why can electrons pass from cat-whisker to crystal. These atoms accumulate very quickly, crystal (or the reverse) but not in the opposite just as the bubbles of the gases appear instan- direction? taneously when the current is turned through There have been many theories for this recti- water. They may be accumulated, in fact, by fying action of the crystal. Some of them a single, one -direction pulse of the current. department. The latest During this one pulse more and more lead have been noted in this with -and in many ways the most plausible-has atoms continue to accumulate in contact by Mr. Alfred Clive the others. The spot of metallic lead thus been proposed recently an easy James of East London College, London, Eng- formed at the crystal surface makes .path for the electrons into or out of the crystal. land.* now, the direction of the cur- It is an electrolytic theory, which means that Suppose, that general kind of electro- rent changes. The lead atoms would then tend it involves the same lot lead action which happens when you charge to go in the other direction. But a of chemical atoms have become attached already to the a storage battery or when you pass an electric acidified water. When you cat -whisker. These must be removed. In a current through must be "dissolved" again in the thus "electrolyze" the water the water is sense, they atoms appear at one of main mass of the crystal, just as a part of broken up. Oxygen the material on the active plates of a storage the electric terminals ; hydrogen atoms appear crystal consists, battery is dissolved while the battery is being at the other terminal. Now a atoms sulphide, which is galena. discharged. This removal of the lead for example, of lead absorbs some of the energy of that pulse of It contains lead atoms and sulphur atoms. - some sulphur thinks, is that the the current. At the same time, What happens, Mr. James atoms are left at the point of contact. These current passing through the crystal drives the apart from are non -conducting. No current gets through. lead atoms and the sulphur atoms When the current reverses once more the each other, more or less. In a similar way, the the atoms of lead atoms again accumulate in contact with current in the water drives apart passes, and the oxygen. the cat -whisker, the current hydrogen and of cycle begins all over again. *"The Rectification of Alternating Currents by This theory involves the assumption that the Crystals," by Alfred Clive James. The Philosophical metal atoms in a crystal of galena are able Magazine (London), Series 6, vol. 49, Pages 681 -695 less freely, through (April, 1925). to move around, more or

www.americanradiohistory.com 68 POPL'l._NR RADI(l

the meshes of a fixed network of sulphur the same two stations. This has seemed very atoms. We do not know enough about the surprising. Radio waves are supposed to pass inside structure of galena crystals to say defi- through the ether. If at the same instant and nitely whether or not this is true, but there with the same power, a station in England can seems to be no important evidence against reach one in the United States but cannot hear it. Also, it provides, for the first time, a pos- the precisely similar signal moving in the oppo- sible mechanism to explain the mysterious oc- site direction, it looks as though the ether were currence of sensitive and insensitive spots on a one -way street, a supposition which the physi- the same crystal surface. cists have never been willing to entertain. In crystals of argentite, which is sulphide Yet many instances of such apparent one -way of silver instead of sulphite of lead, the mov- transmission have been observed in the past able atoms are those of silver. These silver five or six years. atoms accumulate and dissolve at the contact Captain T. L. Eckersley, of the British Mar- point, just as the lead atoms do in galena. coni Company, now comes to the rescue with a The sulphur atoms are fixed, as before. Other suggestion of two ways in which such a difference crystals, such as carborundum, are thought of between wave propagation in opposite directions as acting in the salve general way, some electro- might be produced.* Both ways depend on the lytic change inside the crystal being responsible assumption that there may exist in the atmos- for the rectifying action. phere more or less separate clouds of "slabs" of So far, all this has little practical importance. ionized air, an assumption already made, years But if it does prove that Mr. James has put ago, by Dr. Reginald A. Fessenden.t his finger on the vital clue to crystal rectifi- If these "slabs" of ions are in motion, either cation we will doubtless be able soon to im- vertically or in a direction parallel to the latitude, prove the utilization of crystals in practical there will be reactions on the passing radio waves, which radio. Even now, it is notorious that crystal reactions are unidirectional and may op- detection is more nearly distortionless pose either the east -to -west \Nave or the west -to- than east any other procedure which we know how to use. one, while at the sane time favoring the Perhaps a knowledge propagation in the reverse direction. Captain of how the atoms act Eckersley inside crystals will yet bring the crystal back analyzes briefly the mathematical to an honored place in radio. and physical conditions necessary for such a one -way barrier to the waves.

One -way Propagation of * "Non- Reversible Transmission," by T. L. Eckersley. Nature (London), vol. 116, pages 466 -467 (September Radio Waves 26, 1925). "Wireless Telegraphy," ONE t by Reginald A. Fessenden. of the puzzles of radio has long been the The Electrical Review (London), vol. 58, pages 744-746 apparent fact that transmission may be possible (May 11, 1906) and pages 788 -789 (May 18, 1906). in an east -to -west direction (or vice versa) when See Dr. Fessenden's article, "How Ether Waves Really Move," POPULAR RADIO, vol. 4, pages 337 -346 (Novem- it is not possible in the opposite direction between ber, 1923).

General E ectric HE FINDS SOMETHING INTERESTING IN MATTER One of the features of the meeting of the American Chemical Sociéty, at Los Angeles, last summer, was an address by Dr. Willis R. Whitney, of the General Electric Company on "Matter-Is There Anything in It ?" By a series of ingenious and spectacular demon - ctrations Dr. Whitney showed the chemists some of the remarkable properties of the tiny electrons and protons which make up the atoms of matter and which are so important in radio.

www.americanradiohistory.com s á' /7 %i /!%1', .mmr ' . Y/% 3/' /O x/% ,/' /%i/ 1 zf7 7.1/ rare :`a/' WHAT'S NEW IN RADIO APPARATUS

THIS department is conducted by POPULAR RADIO LABORATORY for the purpose of keeping the radio experimenter and the broadcast listener informed concerning the newest inventions and the approved developments in radio equipment. Only such apparatus as has been tested and endorsed by the Laboratory is noted in these columns.

equipped with a long extension cord for fastening to the 110 -volt 60 -cycle lighting lines. It will reactivate both the small and large thoriated filament tubes of the 199 or 201 -a type. It is equipped with a lever which changes connections in the interior for producing the high current for flashing the filament, the medium cur- rent for maximum reactivation of the filament and the normal current for light- ing the filament during test. When this lever is moved to the extreme left a react- ing on the meter is obtained that gives an indication of the filament emission, so that A neat binding post that is the operator may determine just when easy to operate. his tube is fully reactivated. Usage: As an accessory for radio set owners in getting their tubes in good condition. A SPRING BINI>ING POST Outstanding features: Compactness. Efficiency. Ease of operation. Equipped with a Name of instrument: Binding post. meter. Description: A small, neat binding post that (Further details furnished on. request.) contains a spring top, which when pushed in opens the hole in the side to which the wire may be inserted. Upon releas- ing the pressure of the spring by taking the finger off the binding post a firm solid connection is made. Equipped with circular name plates that designate what the binding post is to be used for. Neatly made and nickel plated. Usage: In combination with a home -built re- ceiving set for making connections to the batteries and the antenna and ground. Outstanding features: Ease of operation. Good contact. Neat appearance. (Further details furnished on request.)

A TUBE REJUVENATOR Name of instrument: Tube rejuvenator. Description: This piece of apparatus is con- tained in a metal cabinet with a black A compact device for making new tubes out crystalline finish. The apparatus is of old ones; it operates simply and efficiently. 69

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A TRANSFORMER FOR THE NEW RAYTHEON TUBE Name of instrument: Step -up transformer. Description: This transformer consists of a primary winding for operation on 110 volts 60 cycles alternating current with a split secondary winding which is statically shielded from the primary by means of a copper shield brought out to a separate binding post. This secondary supplies the high voltage alternating cur- rent to each side of the full -wave recti- fying tube, with which the transformer is designed to be used. The instrument is mounted in a black enamel case with an extension cord running to the light- ing socket. The case is so designed that a free circulation of air is obtained. Usage: As a transformer for supplying the necessary energy to the Raytheon Plate Supply Unit. Outstanding features: Neat in appearance. A well-made plate -supply transformer. Sturdy in construction. Easy to install. (Further details furnished on request.) A NEW RHEOSTAT Name of instrument: Rheostat. Description: A novel means of supporting the rheostat winding is used in this device; it is bent around a series of insulated plugs made in one piece with the Bake- lite base of the instrument. This gives the resistance element a large radiation of heat and prevents burning out the coil or damaging the insulation upon which the resistance wire is wound. A novel means of variable contact is made in which the flexible contactor runs around the outside of the element. The instrument is equipped with soldering lugs. Usage: In any receiver for controlling the filament current of vacuum tubes. Outstanding features: Accurate workmanship. Good contact. High radiation of heat. Smooth action. Neat appearance. (Further details furnished on request.) This rheostat will not get hot.

A TWIN VARIABLE CONDENSER Naine of instrument: Double variable con- denser. Description: This unit is unique in design by reason of the employment of two sets of rotor plates on a single shaft and two insulated sets of stators. It may be used for tuning two stages of radio - frequency amplification simultaneously by means of a single knob or for other uses where a tandem condenser is found. The work- manship of this unit is of the same high standard as other instruments by the same maker. Usage: Li any radio - frequency circuit for tuning. Outstanding features: High efficiency. Com- pactness. Dual operation. Easy to mount on panel. Single (Further details -control may be accomplished with this furnished on request.) condenser.

www.americanradiohistory.com WHAT'S NEW IN RADIO APPARATUS 71

A UNIVERSAL TUBE SOCKET Name of instrument: Vacuum -tube socket. Description: This new socket is available for use with all of the new UX type of tubes, new WD type of tubes and for the older UV -201 -a types. It is fitted with a new special contact that is one piece through- out and including the soldering lug. :A metal support is fastened with two screws to the top of the socket for holding some of the tubes in rigid upright position. Usage: In a radio receiver for mounting vacuum tubes. Outstanding features: Compactness. Fits all standard types of tubes except the old 199. Neat in appearance. Low capacity. Good contact. (Further details furnished on request.) A socket for all standard tubes.

A WELL INSULATED CONNECTOR Name of instrument: Connection block. Description: This device consists of a cylinder of glass supported by two metal clamps - one at each end. Two other metal ter- minals are provided- insulated from eách other and from the end clamps by means of the glass cylinder. These contain Fahnestock clips as well as soldering lugs to which the lead wires may be directly connected. Usage: In the experimental laboratory as ter- minals for batteries or generators. Outstanding features: Good insulation. Com- pactness. Ease of installation and at- 1 small connection block in which the i iiiiurls tachment. are well insulated from each other and front (Further details furnished on request.) everything else by means of a glass tube.

A NOVEL ANTENNA TER \IINAL Name of instrument: Antenna Connection. Description: This device is a small disc of metal of about the same diameter as the bot- tom of a telephone stand. It is equipped with a Fahnestock binding post and a length of wire which may be attached to the antenna post on the receiving set. By merely placing the telephone desk stand on it, the felt bottom of the tele- phone stand acts as an insulator and as the dielectric of a small condenser of which the metal plate is one terminal and the desk stand is the other terminal. In this way, the radio signals that are col- lected by the telephone wires may be transferred to the receiving set. The sig- nal strength obtained with an attachment of this kind is somewhat dependent upon the local telephone circuit, but a sensitive set should give results in nearly all cases. Usage: In connection with a telephone line and a radio receiving set as a pick -up device. Outstanding features: Simplicity. Compact- A novel device to connect the telephone wires ness. Easily installed. to the set as an antenna. (Further details furnished on request.)

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Three condensers harneJsed together to give you single -control with a dial calibrated in wavelength.

A UNIT CONTROL TRIPLE CONDENSER

Name of instrument: Triple Condenser Unit. wavelength may be Description: In tuned in by simply this novel unit three con- turning the single knob so that the read- densers are mounted and controlled by a ing appears at the indicator. single knob which acts through friction Usage: In a receiving set for tuning through the large solenoid a two - disc. The stage radio - frequency amplifier with a disc is set on, the rotor shaft of the single knob. middle condenser and a novel cam ar- Outstanding features: Single control. Uni- rangement turns the two outside rotor form capacity settings. units of Efficiency. Di- the condensers. The dial is rect wavelength calibration. Fine work- calibrated in wavelength and when the manship. unit is used with the proper coils any (Further details furnished on request.)

A STORAGE BATTERY THAT CIIARGES ITSELF

Name of instrument: Storage battery with self - contained trickle charger. Description: This "A" supply unit is made in two sizes for either 4 or 6 volts operation and contains either two or three cells respectively. It also contains a trickle charger that keeps the cells always in operating condition. It is equipped with binding posts for connection to the set and a switch that is used for connecting the batteries through either the charger or to the receiver. A plug is furnished for connecting to the socket of the ordi- nary alternating current lighting lines. By this arrangement a small switch may be thrown to either one of two positions which provide the set with filament cur- rent, or charge the batteries. In this way, the battery is being continuously charged at all times at a very slow rate except when it is furnishing power to the receiving set. Usage: In connection with a receiving set for supplying filament current. Outstanding features: Automatic in operation. Reliable. Keeps batteries always in good condition. Relieves the set owner from worries about keeping battery charged. Simply throw Neat in appearance. a switch to connect this battery to your receiving set; then throw it back (Further details furnished on request.) again and it becomes fully charged while not in use.

www.americanradiohistory.com WHAT'S NEW IN RADIO APPARATUS 73 Apparatus Approved by Popular Radio This list of apparatus approved by the POPULAR RADIO LABORA- TORY will be continued as a part of the WHAT'S NEW IN RADIO APPARATUS department until all instruments, parts and complete sets have been included. The listing is alpha- betical by manufacturer's name and the installment in this issue includes the letters U through Z.

-FREQUENCY AMPLIFIERS "Van -Le" reproducer; Van -Le Corporation AUDIO Professional reproducer; Voluma Products, Inc. l'eby complete 3 -stage resistance -coupled ampli- "Moon" loudspeaker; Wilson Utensil Co. fier; Veby Radio Co. "Windsor" loudspeaker; Windsor Furniture Co. AUDIO -FREQUENCY '.. RANSFORMERS MISCELLANEOUS ACCESSORIES "United" audio- fr'egdency trans( ormer; United Dial adjusters; Union Radio Corp. Mfg. & Distributing Co. Valley clip; Valley Electric Co. Audio -frequency transformer; Louis E. \Vents Solder flux and rosin core solder; Valley Forge Chemical Co. BATTERIES Var Flex tubing; Var Flex Corp. RB "B" battery; Universal Battery Co. Var Flex wire core: \'ar Flex Corp. U. S. L. radio "A" and "B" batteries; U. S. "Cross Country" r : "cuit (parts and instructions); Light & heat Corp. Vesco Radio Co. Waterbury "A" battery; Waterbury Battery Co. "Penetrola" (auxiliary unit); Walbert Mfg. Co. l i'estinghouse crystal case "A," "B" and 'C" Panelites; Walbert Mfg. Co. batteries; Westinghouse Union Battery Co. Adjuster; Walnart Electric Mfg. Co. "Willard" radio batteries; Willard Storage Bat- "Workrite" concertrcla; Workrite Mfg. Co. tery Co. Radio "B" battery; Winchester Repeating Arms PANELS Co. Hard rubber panels; United States Rubber Co. "Wizard" "A" and "B" batteries; Wizard Bat- tery Co. PHONE PLUGS "World" storage "A" and "B" batteries; World Battery Co. G. W. 5- circuit plug; G. E. Walker Co., Inc. Plug; Yaxley Mfg. Co. BAT'T'ERY CHARGERS AND RECTIFIERS "]'alley" battery charger; Valley Electric Co. I'I-TONOGRAPH ATTACHMENTS Ampl -tone loudspeaker unit; Union Fabric Co. BINDING POSTS Lettered binding posts; Walnart Electric Mfg. Co. POTENTIOMETERS Potentiometer; United Scientific Laboratory, Inc. CRYSTAL DETECTORS Potentiometer; Yaxley Mfg. Co. "Curnmings" union crystal; Union Radio Elec. Stores, Inc. RADIO CABINETS "Yellowtip" crystal detector; Wholesale Radio De Luxe radio cabinets; Utility Cabinet Co. Equip. Co. Radio cabinet; Whaling Wood Products Co. DIALS RADIO -FREQUENCY TRANSFORMERS Micrometer dial; U. S. Tool Co:, Inc. "United" radio- frequency transformer; United Knobs and dials; Walbert Mfg. Co. Mfg. & Distributing Co. Dial; Walnart Electric Mfg. Co. "Victory" 4- circuit transformer; Victory Radio "Workrite" E -Z -Tone dial; Workrite Mfg. Co. Co. Knobs and Dials; Yaxley Mfg. Co. "Werner" radio- frequency transformer; Werner Radio Mfg. Co. FIXED CONDENSERS Fired condenser; Walnart Electric Mfg. Co. RECEIVING SETS Fixed condenser; Yaxley Mfg. Co. . "Unidyne" receiver; United Mfg. & Distributing Co. GRID -LEAKS AND RESISTANCES U -S -L Broadcast receptor; U -S -L Radio, Inc. Variable grid resistances; Wálna'rt Electric. Mfg. "Radiodyne" receiver; Western Coil & Electrical Co. Co. Royalty variable grid-leak; Wireless Products "Elf" crystal receiver; Westwyre Co. Corp. Zenith receivers; Zenith Radio Corp. Royalty resistance units; Wireless Products Corp. Resistance unit; Yaxley Mfg. Co.. RHEOSTATS Rheostat; United Scientific Laboratory. Inc. HEADPHONES "Unity" vernier rheostat; Unity Mfg. Co. "Arnpl- tone" phones . Union Fabric Co. Rheostat; Wilcox Laboratories. "Warren" Phones; Warren Radio Phone Mfg. Co. " Workrite" vernier rheostat; Workrite Mfg. Co. "Workrite" concert headset; Workrite Mfg. Co. Rheostat; Yaxley Mfg. Co. JACKS . SOCKETS AND ADAPTERS Union tip jack; Union Radio Corp. V. T. Socket; Union Radio Corp. Jacks; Yaxley Mfg. Co. . iValbert safety rim socket; Walbert Mfg. Co. if'aluart sockets (bakelite insulation); Walnart

KITS - - Electric Mfg. Co. U -ni -dial kit; Unidial Radio Co: Super -heterodyne' kit; Victoreen Radio, Inc. SWITCHES Filament lock switch; Walbert Mfg. Cp. LOOPS - . Switch; Walnart Electric Mfg. Co.

:Variable radio loop antenna; Werner Radio Mfg. Midget - battery switch; Yaxley Mfg. Co. No. 210 Pilot light switch; Yaxley Mfg. Co. LOUDSPEAKERS TESTING INSTRUMENTS Black Beauty reproducer United Radio ,Corp. i1'eston panel voltmeter; Weston Electrical Instru- "Utah" phono-speaker; Utah Radio Products Co. ment Corp.

www.americanradiohistory.com Louisville Courier -Jour,, il DUPLICATING TIIE WORLD'S SERIES BY RADIO Replaying the innings of world's series baseball games on a field in Louisville, Kentucky, the games while were actually going on in Pittsburg or in Washington was the feat that radio made possible. Two Louisville teams took the part of the big leaguers and duplicated within a few every play minutes after it was made. The players all wore headphones. These were wired to their feet and a connection made through metal discs set in many parts The broadcast report of the field. was picked up by receivers and transmitted to the players who re- enacted what they heard. The BROADCAST LISTENER Comments on radio programs, methods and technique -from the point of view of the average fan By RAYMOND FRANCIS YATES

Some Grade -A Broadcasting avenue with a full cutaway, a topper and a fifty-cent straight. You say it with razzberries at Last one day and with a great big bunch of orchids the next. THE big -meter waves have washed up a few There is just one A- little fault that we have number -one radio -acts since the appear- found with the Atwater -Kent programs. ance of our smashing review in the Not November that we wish to put on the elegant air of the issue. As a matter of fact, it begins to look as snooty connoisseur, though for we are perhaps one .of we might have to take back what we the worst listeners that ever said about the small difference fell into applaud- between the ing with the rest of the pretenders at Carpegie summer and winter season. Here we have Hall. heard Josef Hoffmann, Olga Samaroff, May It seems to us that these air Peterson and Louise Homer and concerts would Toscha Siedle he immensely improved with a more brilliant all within the space of a single month! That's accompaniment for the singing a pretty heavy brand of entertainment artists. T'n the after concert hall, with its dazzling chandeliers, its you've grown accustomed to a musical diet con- smartly dressed sisting women and its gayly decorated chiefly of nothing but homeopathic walls, there is created an atmosphere doses of twenty- nine -cent phonograph records. that makes the piano sufficient, but that same piano is a It's getting so that you cannot tell what radio pretty drab background will in a radio recital. This do next. One day it is walking down admission may show us up as Sixth avenue in being one of the a crash suit smoking Cincos rawest radio critics in the business, but and the next day it is swanking just the down Fifth samey we feel that Mr. Atwater -Kent would 74

www.americanradiohistory.com T II is BROADCAST LISTENER 75

a full twelve -pound sound If we had the handling of the Atwater -Kent be giving his concerts with by adding a small symphony orchestra. A con- programs we should engage an announcer cert in Carnegie Hall and a concert in the home the training and background of -of -. 567 Plimpton avenue, the Just fancy that, we can't think of a soul! of J. k\ hoasis Smith, next Bronx, U. S. A., are two totally different Well, we'd save Mr. McNamee for the things. In Carnegie Hall it is not difficult to World's Series, anyway. make May Peterson sound like a $3,000 -a -night * voice with the piano as the only support, but when you lift that voice out of the Hall and A Hot Shot from Chicago place it in the average American home you taking JUST when we are beginning to take seriously haven't very much left. It's just like thousands of flattering letters off the stage mystic. the many, many the purple spot received, along comes a Chicago reader with is no good reason to say that Mr. There a mad on. McNamee is doing a line bit of announcing in connection with the Atwater -Kent programs, "Dear Sir : because he isn't. If Mr. McNamee is not flat- "Don't take this salutation seriously. tering the star he is flattering or patronizing "Beyond a doubt you are of the type that his audience, and if he isn't doing that he is would kick the crutches from under a cripple tossing out a literary garden of American in a traffic jam. I have been reading with grow- Beauties. Still Mr. McNamee is the star an- ing disgust and finally with pity your puny ef- nouncer of WEAF, and was rushed right from forts at mirth under the section The Broadcast the World's Series to the opening concert of Listener.' the Atwater -Kent programs. It does seem a "Now for a dose of your own literary effort. bit incongruous that a man should perform so Perhaps I can set your warped intellect right efficiently at baseball, at the ringside, at po- regarding broadcasting in the Chicago district. litical conventions, at football and at big league I refer especially to your paragraph 'The Chi- recitals. Either Mr. McNamee is a very keen cago Listeners Strike.' In the first place Chi- and widely learned gentleman or he is of just cago is still in the republic and neglecting the ordinary sophistication and is being badly over- 18th Amendment the Constitution is holding worked. sway. A petition from thousands of broad-

Kadel & Herbert THEATRICAL STARS ENTERTAIN HOSPITAL PATIENTS BY RADIO and furnished A program which was designed for the special benefit of hospital patients, Club in by many famous stars of the theater, was broadcast recently from the Friars Pew York. Burr Macintosh, actor, author and lecturer, is here shown before the microphone in the famous club's quarters.

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cast fans lias forced the Chicago broadcast- ing stations sweet time cutting off the dozens of to close one night a week. We've lengths on wave- a right to our opinion which some energy is being radi- here as well as you ated. Thirty -two local in the Empire State. In addition, the broadcasting stations Radio Mayor's are capable of blanketing the entire Comtmssion requested all local stations spectrum. broadcast to close on Monday evening. Many broad- "Believe me sincere, casters took advantage of this by reason of the fact that their stations were located "H. M. D." the corporation outside limits. After a good deal of We did effort, the Radio Broadcast Listener's feel a little mean and small after tion, Associa- reading H. M. D.'s letter, but of which I am not a member, succeeded out we walked right in closing all and tossed off a Coca -Cola and came these stations with one exception. feeling fine. back This station is negligible, because Part of the next three days we it is on too spent trying to think up high a frequency and cannot be heard a funny answer for the ordinary well on H. M: D.'s calling us a kicker receiver. from of crutches " \Ve'll admit under cripples in traffic jams, that broadcasting is not yet on the life of but for the hoity -toity plane you us we could not think of a thing are planning on putting that had the right kind it. There are as many people who of a ring to it. We music like dance might have told him, however, and popular songs as there are those stood that we once \\'lto for fifteen minutes on a enjoy highbrow music. I ant of the opinion nickel that a that there poor old lady had dropped in is room for every type of music and There's the post office. program. But really no telling what we were we to accept your recom- in a traffic might do mendation, we would degenerate jam. of to your type \Vhen we came to the spineless jellyfish, wanting only one part of Mr. H. M. utd to thing D.'s letter wherein he accuses hell with the others. I have listened lift broadcasting us of trying to to Art Linnick go from to a hoity-toity plane we one station to another, lost control of just singing the saute song six days ourself and guffawed só tliaf one a week f5r you could hear it all over whole summer. Certainly we are entitled the place. That is, hear the Hotel to perhaps, the funniest statement that Nicollet orchestra at Minne- been made has ever apolis or the Hotel Alexandria in this department. We had thought orchestra at tip until this time Los Angeles one night a week. As that "our puny efforts at concerned far as I'm mirth" was one of the most they could close every Chicago sta- substantial barrels tion seven nights of solid hoke mined in the western hemisphere. a week and I'd never miss Another letter 'em. But there are thousands like that and we shall go right who would. We up to Carnegie Hall are entitled to one night a week to hear and write a cruel and the other fellow what devastating critique on Mr. Walter is doing. You mmght reply, conducting. Damrosch's 'Get a good set.' Thank you, the I have one, but Mr. H. M. D. says "I most selective in the shadow of \V'IBO, am of the opinion that \VQJ, WBBM and there is room for every type of music \VI I;1í would have a gram." That and pro- either proves that Mr. H. M. D.

BROADCAST -LISTENERS SIT IN ON A BRIDGE Radio fans GAME WITH EXPERTS recently had a chance to learn the fine points best -known authorities of auction bridge from some of the when ganses played by E. V. Shepard, Work, and Sidney W. C. Whitehead, Milton. C. S. Lenz were broadcast play by play.

www.americanradiohistory.com THE BROADCAST LISTENER

Kadel & Herbert POLITICAL CAMPAIGNERS DISCARD THE "STUMP" FOR THE "MIKE" Instead of addressing the handful of listeners who can come within range of his voice, the politician of today addresses hundreds of thousands at a time by radio. The political con- tests of tomorrow will be largely contests for access to broadcasting stations. Here is a peep at the broadcast debate between Governor Smith of New York and Representative Ogder Mills on the eve of Election Day at Buffalo. is a member of the Kiwanis Club or that he has one broadcaster in the country that will be able really given serious thought to this business of to meet these demands and, except in isolated broadcasting. It invariably happens that a cases where broadcasters desire to use special man doing heavy thinking on the subject of programs, the Society's income from radio will programs eventually comes to the conclusion he small enough to carry around in the change that America is a racial vegetable stew and pocket of any overcoat. that, consequently, its broadcasting must be If the Society would ask a reasonable charge built upon the principle of a crazy -quilt or a of say $10.00 a day for each broadcaster using Beloochistan rug. its copyright music, its income would be in- If you meet us on the street some day mut- creased by some hundred thousand dollars a tering strangely and incoherently, you will year, which would be just so múch gravy. In- know that we succumbed to the mental strain stead of being satisfied with this the Society of trying to devise a hoity -toity program that is setting to the task of gathering in millions will please cosmopolitan America. from an industry that has been bankrupt since Seriously, we shall try to be more tolerant, the very day it was born. as Mr. H. M. D. wishes. You know the voice * * * with the smile wins, and we really should have more Kewpie dolls smiling at us from the An Atlantic City Fan Breaks mantelpiece. * * Loose "Dear Sir : The Demands of the Society of "When one does a good thing it is natural that one likes to know that others appreciate Authors and Composers it. Consequently, I am doing something very UP until a few months ago we had worked unusual for me- taking the time and trouble up quite a bit of sympathy for the Society of in a very lazy life to congratulate you on Authors, Composers and Publishers, but sub- your strong editorials. I refer especially to sequent action of the Society in attempting to `Studio Sheiks' and `Some Pretty Bad Sta- extort what would amount to a fee of from tions.' $100.00 to $200.00 a day from each broadcaster "In your next editorial, - please comment on in the United States, has left us a bit cold and these lady -like announcers who try to put such prejudiced. The demands are exorbitant and pathos in their voices. It is plainly evident ridiculous, and they show that the officers of that they are listening to themselves. I refer the organization have a very poor head for especially to Clarence Bowden of WOO and "figgers." At the rate mentioned, there is not .Major Bowes of the Capitol. Major Bowes

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certainly does 'love his little family' -my God! fur the world's best broadcasting "You must listen station should to Clarence tell about the Le just aLu.tt as easy as an improvement in composers of the organ compositions he pas. circus lemonade. It is certainly amusing to listen to these fellows Rule No. 1. Announcers with their broad A's and their must refrain from giv- totally affected ing even a hint pronunciations of various sorts and styles. concerning their "And while identification. I'm all het up and mad, I want Rule No. 2. to damn this Any announcer caught using the word ensemble, which seems to broad A or making have just been discovered. Orchestra and band other effort to are sound ritzy, will arrange his own good old -fashioned words and they are appointment exact in their meaning. with the cashier. Rule No. 3. Announcers must not "The writer of 'The Broadcast Listener' cer- use the phrase tainly has courage. "and now at this time." Now usu- ally means "at this time." (WJZ- "C. S. D." W J Y staff please (Will Mr. II. M. D. please note?) note.) Rule No. 4. One soprano will be permitted to sing two selections from this studio How to Run a Broadcasting every third Friday. Rule No. 5. The equipment of this station is not Studio available to the clergy unless they can relieve their voices of IF anybody should ever ask us to manage a every broadcasting trace of sanctimonious moaning in studio we should immediately post the lower register. a set of rules and regulations, which, if fol- Rule No. 6. No HAND CLAPPING IN THIS lowed out, would make it the best station in Rule STUDIO. this great big world No. 7. All boys under twenty years of age of ours. After you stop who to carefully weigh this boast, play Hohner harmonicas are re- it really isn't say- ferred to ing a lot. I f you the program manager of set out to make a better \ \"L. Woolworth Building or a \F and WJZ. better radio magazine Rule No. 8. No artist than Porli.Alt R.vDIO (advt.) (especially female) will you'd have a be permitted pretty hard job on your hands, but the formula to tell the audience that he or she was "thrilled" or that it was a "perfectly wonderful ex- perience." Rule No.9. If Major Bowes broadcasts from this studio, will he please refrain from calling his troupe his "happy little family." That is obvious ap- plesauce. Rule No. 10. Song pluggers will please apply to Mr. N. T. Granlund, seventh floor (third office to the right), Loew's State Theater Building, Broadway and Forty -fifth street, New York City, U. S. A. Of course, we could go on writing these rules until the cows came home. What we really wanted to do was to show you that we are a big, bright -eyed boy, conscious of and alert to all of the sad little mistakes that our large - minded impresarios are making. The chances are that we might he wrong, too, but if we are as wrong as our impresarios, we will, on Thursday morning, March 25, rain or shine, take a nose dive from the top of the Columbus statue at the Fifty -ninth street entrance to tral Park. Cen-

Dramatic Reading and Other Whatsis MRS. GLORIA WATKINS JONES, patron of the Kadel & Herbert arts, and wife of the wealthy local cigar manu- A FLYING facturer was one of the first to discover radio as BROADCAST STUDIO a means of lifting the literary The cabin tastes of the of the giant Sikorsky airship was con- masses above the level of the confession maga- verted into a studio when Maxine Brown broad- zines and the illustrated cast her tabloids. Mrs. Jones part of the program from a spot a thousand is a big, indignant person when it comes feet or so above the earth. to the The program was sent subject of appreciating the greater things in out "n a 40 -meter wave, was picked up at WGBS literature and she recounts, and rebroadcast with not a little on the station's regular wavelength. feeling, the slovenly tendencies of the modern

www.americanradiohistory.com TILE BROADCAST LISTENER 79 reader who could easily be lead to believe that EXHIBIT NO. 1 Oscar Wilde was a great ball pitcher of the 90's, "You are sitting all alone. The cat is asleep that Newton invented the Fig- Newton or that in front of the fireplace and it is six o'clock Captain Dingle is the world's greatest writer of in the morning. You hear a gay whistle and sea stories. you run out to see who it is and it happens to Now Mrs. Jones can practice her sophistica- be the ice man. `Lonesome.' " tion at her bridge parties with no objection on the EXHIBIT NO. 2 some sup- part of this department but when "Some say it xvas the joke you heard in your posedly intelligent studio manager knowingly rattle. `Pal of My Cradle minutes and one thou- cradle, others the presents her with twenty Days.' " sand watts of power something should be done EXHIBIT NO. 3 in about it. Permit any Mrs. Jones to heave logs and stone. The boys find wherein there is much "A pile of the throes of a recitation, a number. A pile of logs and of subtle literary this very hard tragedy and loads and loads stone indicate a home." perfection, and you commit one of the worst and most disgusting broadcasting crimes that One could not truthfully say that 1\Ir. Carlin can be committed in this or any other country. is verbose, for it is evident that he has some Here is one vote against dramatic reading on definite thought in mind. He does not seem the air. to be able to concoct a combination of words to convey that thought. It may be -and we just happened to think of this -that his thought Negro Spirituals is so weak that all of the words in the dic- not help it. A LOT of broadcast singers have lately gone tionary would in for the moaning of negro spirituals, and it's * getting so that you cannot turn to the radio The Roxy Formula without hearing the white man's version of the colored man's prayer. There is nothing more ALL of our studio managers must have taken easily overdone (that may not be strictly true, to their various cellars for the purpose of mut- but let's assume that it is) than the sanctimo- tering to themselves on the day after Roxy's nious wailing of darky hymns, and we must return to the air. A special messenger, dust - request that our studio managers consult this covered and breathless, has just placed a com- department before engaging any more quar- munication from 195 Broadway on our desk tettes all filled tip with spirituals. By the time which states that all WEAF mail records were the second or third hymn is reached that broken on Saturday, October 31, 1925, the day gloomy, Alice -is- dead -in- the -next -room atmos- after Roxy's broadcast. We also have it on phere is created, and you feel like going right mighty good authority that all Eastern stations out to the corner drug store where they wrap were broadcasting only to the immediate fami- it up to look like laundry. lies of their performers on the night Roxy * made his return to WEAF. It has always puzzled us how Roxy's for- Some Extraordinary mula has so successfully kept all of our great studio 'managers baffled. Roxy is perhaps the Announcements easiest man in the world to follow because his EITHER Mr. Phillips Carlin (one of the methods are so simple. Of course, simplicity is WEAF boys) is a very subtle humorist and a a hard thing to fathom after all, and it would thirty- third -degree announcer or we are just not be fair to be too harsh with the studio plainly and hopelessly dull. Perhaps you have boys for their having permitted Roxy's very had better luck with Mr. Carlin, but it has simple tricks to elude them. ' been our experience to completely fumble the If you've got any ear for music at all (we meaning of nine of every ten announcements are quite sure that you have an ear for music, that this gentleman makes. It is more than but we sometimes have our doubts about all the barely possible that his reflections are a bit too rest of the listeners in America) you know that esoteric for us but we are inclined to doubt Roxy does not go to the booking offices of the this, for it was only the other day that our Sterling Vaudeville Circuit to find his musical Research Department handed us a report on talent. Trick No. t is to get good performers. Carlin which seemed to indicate that his gen- Trick No. 2 (and this is simple) is that of eral registration record was low. maintaining variety by permitting his artists to \Ve copied a few of his announcements re- sing or play but one or two numbers at a time. cently just for the purpose of examining them Now that Roxy is exposed, we shall expect at our leisure, but so far all efforts at transla- all of our great studio managers to follow him. tion have failed. Our Psychology Department Not that we would for a single moment under- offers a prize of two full United Cigar Store rate these hard- thinking fellows, but anyone coupons to any reader discovering a meaning, wishing to place a little five to one bet on the however vague, in the following Carlin an- outcome will please communicate with our third nouncements : secretary, 627 West 43d street, New York, N. Y.

On page 98 of this issue a new department is inaugurated under 411 the direction of Mr. Lloyd Jacquet.

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY CONDUCTED BY LAUR I \ C E M. COCKADAY

Some Methods for the field, Determining minimizing the amount of it and de- the Distributed creasing conduction (decrease Capacity tween resistance) be- turns. Spacing the turns decreases of Coils latter considerably. the Variable BEFORE going into the methods condensers have been improved to ing of determin- the point where they have the distributed capacity of coils it may only one percent, or well to briefly be less, the resistance of the average outline the advantages to be ing coil. Work- derived from decreasing- on coils is, therefore, well worth this capacity. To measure while. This capacity arises from the existence the distributed capacity of coils series of of a a variable standard of nearly parallel wires in a coil. Any capacity and a wave - two adjacent wires meter are necessary. For rough work are roughly analogous to able condenser a vari- two small plates of a condenser. No of the General Radio type No. therefore, coil is, 247 can be used. This should a pure inductance, but it may be have a calibration considered a pure inductance curve.* with the summa- For the tion of all the inter -turn capacities man who dklikes mathematics the capacity. as a shunt graphical method of determining Most of this capacity is between two distributed ca- adjacent turns pacity is best although this is less because the capacity from one the other accurate than turn to the second from it decreases systems to be given. proportional at a rate to the distance between them raised to X=1.885 / L a power greater than unity. That is, (C+Co) (1) the capacity does not decrease directly as the Where A is wavelength in distance between the conductors is L meters as increased, the pure inductance of the circuit is the case in a condenser of the usual type henries in micro - where the stray field is negligible, greater but at a C the value of the shunt capacity rate. micro- microfarads used in The main objection to this capacity and the lies in Co the distributed capacity of fact that this series of small con- micro -micro the coil in densers is usually farads. of a high -loss type. This is Squaring both sides due to the fact that the wire insulation and some of the supporting A.2=3.553 material are in the L (C -1- Ca) (2) electrostatic field and cause dielectric and re- As L is sistance losses. Both of these constant the relation between X2 decrease with and C is linear increase in frequency, but when it is and the plot will be a straight bered remem- line as Yshown in Figure that the power dissipation in a 1. The slope of this denser con- line (x in Figure 1) increases directly with increase in fre- is equal to 3.553 times quency, the other L where L is the inductance factors remaining constant, distance of the coil. The it is evident they are still important. from the origin (the point marked factors Other to the point where O) remaining constant (i.e., frequency, ca- the linear curve crosses the pacity and power factor) abscissa (Z in this case) determines the power loss is tributed capacity. the dis- proportional to the .square of the voltage, This follows from the fact this so that when A2 is made should be kept low. This can be best ac- equal to O in equation complished by using_ a straight (2) C Co solenoid type The value of winding. In a coil of this typè it is evident of the inductance can be deter- that if there is a potential mined from this curve by dividing difference of X the the slope of across the coil, the potential difference (voltage) curve by 3.553 Or between two successive turns is 4 where N Y is the number of turns. I, = 3.553 (3) The distributed capacity can be decreased X by slightly spacing the turns. The losses can he minimized by *See article by the improving the dielectric in October, author on page 386 of the 1925, issue of POPULAR RADIO. 80

www.americanradiohistory.com IN THE EXPERIMENTER'S LABORATORY 81

. For X, or the value of capacity to be used ".be accurate within a fraction of a mmfd. which choose some convenient value. In Figure 1 X is ample. If then another determination of a is 100 or the difference between 280 and 180 is made (i.e., the resonant wavelength of the mmfds. ( micro-micro farads). The - corre- parallel resonant circuit composed of the ca- sponding value of Y, which is the increase of pacity C and the coil to be measured) at a A2 between these capacity values, is in this low setting of C, Co then becomes a large per- case 102,500 or substituting in (3) - centage 'Of the total shunt capacity to L. Know-

ing the approximate value of L and - 103,000 1030 the value = = 289 micro -henries (4) of C these can be substituted in (2) and the 3.56 x 100 3.56 value of Co determined. The following procedure should The value of L is in micro- henries be used to since this get Co. Connect the coil, the distributed ca- used in . " was the unit equation (1) In this pacity of which is wanted, across the variable case it should be noted that only three signili- standard of capacity. figures were used. Set this conderser at a cant Actually with a small high settint, giving a high value of size only first of capacity C. chart this the two ligures This shou be about 1,000 mmfd. The wave- should be used in the computations since because length of phis circuit should of size of the then be deter- the chart and the accuracy in mined with a wavemeter.* A "set up" of this measurement only the first two will be reliable. type is shown in Figure 2. The oscillator is If in equation (1) C is as very large com- shown at O, and C is the variable standard pared with C. the latter can be neglected for capacity. The approximate determinations coil is shown at L for which Ca of L or A. If, is wanted (it is placed on a small box shown for example, C is about 1,000 mmfd. (.001 in the foreground to mfd.) and measurement shorten the leads to C) the of L is made for and W is the standard wavemeter. In this an average coil designed for broadcasting fre- rase the wavemeter had no resonance quencies the error introduced indicator by neglecting in the circuit. The condenser C was set to Co is only of the order of 2 percent, assuming a the determination of A is accurate. If this *See "An Oscillating is then used to determine Co, which is wavemeter," by S. Gordon what we Taylor, page 267, September, 1925, issue of POPULAR are primarily interested in, the value gotten will RADIO.

:C ::11: :::G.G'=: : :: G =_ ' _ G : : ::::1111: : : : : i!la::: :: ... .1 :.. ::::::::é::..: .Ï :::::;1.=é;.:: : ...::: .;..._..._.... i :rG =11a:=i:i11G11:11i11.1111=:1=11..._ inn :n 3X,ÁXÌ C: ...... : 1:.. :. .: . G.. r 11:::G:::::ai:::i::G::::::::::r1::::::X . .: p 111. 1. ::1::'C:..P : E 11=.a:11aa=1°a'==':::1::l:.. i : : 111CG.::GG:1:::a:E::::.::1:.:=rrar 1:a:..G:r1/:r.:r:.::i,í/.. . Ali :::::::. : ::: : T.. .. G = 1" :G:G7 : G!. :: ..:: .. GG GG/:EG::r-..:gG:r/G hEI=3..G..:: G: C:::..::11 r 1:::1a?Sa:r : . 11rG .1::. =:11 a : :::: r : . G:r :::: =G.:a: .:/ .ir1a1=1=.::::3G:1:a': :.r r.G/..GGr.1r : : : 1/'Grral' 1...G..... pi G:::: ==r r1G=....,: ::a::: : : f : GG:13:G : rr G _ .. //G ..:..: `'a:::: 1 Ga 11 ::::::CG: :: ::"'C G G' : 1 :.ra.: a Gi:éGGG:: G../p.. : a ... :. 1 ' ::::G::1::: :_r =G.::G: ::C;=;a!11i=E=:G:::':::::=a1111é:[email protected]:i1'G _:: r. . .::.r11 I/S : . :::::lG' .r.=°: ::: 1111 : : G:11:. r 1//Y:l:.:1:ga1 6"1". .:. . .:...::: "i'1 ..:iii:r. :: :::::1.:. 1:G::G'G r... ..:.1...1 1:G=''°::111$°a1p=1=G:::= ::i G : _! :111.:Grr:G i1:1='Cl:Z:.. r. Grr.==..:=r..0 ::::p4111111111:: C:::r=.../ , :1...:G'.=r:GaCG::C=a:::'1.GrG r r 11 1r1.rG1::1::. r r G :G1::G:G=_::::a::::i.::.1lGir i .. .. :1: . : . a. .::. 1r: :. '._: ...... :_:::::1G:a:a:rG1rGG ..C:.r.:G.a.or:G1G 1:G::::ri:a:1::Gi::°_

:.::G1 G:CC::.:G;aGG::: .:::==r: ; ...... ::GG:::.:.:.=a1. :

G .,11n .i :_°_.:._:...... :um ! C:!!l:..C.ë,:.: 2::::111.81:1 =e G -4 0 /00 P019 300 C /N /M/CA'0-41/Ci1764.0703 THE GRAPHICAL METHOD OF DETERMINING DISTRIBUTED CAPACITY FIGURE 1: Several wavelength measurements of a coil and condenser circuit are made ana the wavelength- squared plotted against the capacity at each point. It is shown that the dis- tance OZ represents the distributed capacity of the coil used.

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From a photograph made for POPULAR RADIO THE LABORATORY >\IEASURE \IENT OF DISTRIBUTED CAPACITY FIGURE 2: The coil of which distributed capacity is to be measured is lettered L and its tuning condenser is called C. The oscillator O supplies the radio - frequency current to the tuned circuit LC and a wavemeter 1V shows the wavelength of the radio frequency current. Results of these measurements are plotted as the curve of Figure 1.

high value. Then O was tuned until there substituted in (6) which gives the distributed was a sharp deflection in the plate current meter. capacity Co in micro -microfarads. The coupling between O and the circuit LC was decreased until the deflection was very X2,- 3.553 L C2 sharp indicating the latter was in resonance Co _ (6) with O. The standard wavemeter was then 3.553 L tuned until there was again a sharp deflection in the plate meter of O. The wavelength read- If A can be measured accurately and a more ing of \V then gave the wavelength to which precise value of Co is wanted L should be LC was tuned. Then Co was neglected and the gotten by substituting C,, gotten by direct read- readings of C, and X, were substituted in ing, and Co, from (6) in equation (2) and solving for L. This more precise value of (5) giving L within 1 or 2 percent depending L on the relative values of C and Co as gotten by can then be substituted in (6). In the com- putations given more figures subsequent calculations. The subscript 1 is significant have been used than the used to indicate values of C and A for the theory of precision would first or high wavelength setting and the sub- warrant, but this has been done to provide an equation which is script 2 for the second values of C and A more valuable for accurate taken at a low wavelength. determinations. An equation can easily be worked out which will give Co directly in one ñt operation but this involves involution, or the L= ' (5) extraction of roots, and is therefore somewhat 3.553 Ci more involved. If the experimenter is interested only in where L is in micro -henries and C in micro - the value of C. the so- called " harmonic" method microfarads. of determining it can be used. In this system Condenser C is then set at a low value (50 intregal multiples of some given frequency are mmfd. or less if C is accurately calibrated) used. These can most easily be obtained by which is called C2. The wavelength reading using some harmonic, say the second, of the of this setting is called AI. These values are oscillator. The value of the resonant fre-

www.americanradiohistory.com IN TILT: EXPERIMENTER'S LABORATORY 83 quency will vary inversely as the square root A Milliammeter as an Aid in of the capacity since the inductance is constant. Hence the value of C plus C0 (the total ca- Preserving Batteries pacity in shunt to the theoretically pure in- ductance I.) will he one -quarter of that used IF the experimenter will connect a milli- for the fundamental when the second harmonic ammeter in series with his "B" batteries he (or double the frequency) is used. Or mathe- will be able to tell just what plate current matically his set is drawing and by the use of "C" bat- teries he can reduce the total current neces- (Cr -I- Co) = 4 (C',r -{-- C) (7) sary to operate the receiver to a low value that will permit of great saving in the life of where Cr is the value of the variable standard the "B" battery. at the fundamental, (',r is the setting of the Every experimenter should own a milli - standard for resonance at the second harmonic ammeter for direct current with a scale frequency and C. is the distributed capacity reading of zero to 25 milliamperes that will as before. Solving for C,0 we get take care of nearly all types of receiver.

Cr -4 C'2r Co = (8) 3 Making the Tuned-radio-fre- quency Receiver More Selective where Co is given in the same units that are used for Cr and Cyr. IN some locations close to broadcasting sta- Since the resonance point for the second tions, the ordinary tuned -radio -frequency set harmonic is somewhat difficult to determine, that employs two stages of radio - frequency particularly with a low -power oscillator, the amplification, vacuum -tube detector and two oscillator frequency can be doubled by adjust- stages of audio -frequency amplification some- ment and the values of Cr and C2r deter- times will not give tuning sharp enough, with mined. This increases the possibility of error the ordinary 100 to 150 foot outdoor antenna, but makes computations simpler and is accurate to enable the user to choose between the local enough for all ordinary work. stations or to receive distance while the local To facilitate this and numerous other meas- stations are on the air. To eliminate this urements the experimenter's wavemeter should trouble it is suggested that the antenna be have both a wavelength and frequency calibra- cut down to about 50 feet in length. This tion chart. The latter can he made by taking will enable much sharper tuning and although enough values of X from the present curve it may cut down the volume of signals from ;uid obtaining their frequency equivalents to the distant stations somewhat, it will enable 1)1,41 a new curve. The relation is expressed them to be received without interference from in (9) where f is expressed in x.c. (kilo- the locals. cycles)

300,000 (9) The Old Reliable Single -layer Solenoid Coil -HUGit S. KNOwi.ES RECENT investigations have proven the single - layer coils to be the best type that has yet been developed. The considerations of length over diameter should be very carefully gone into. How to Simplify Connections To get the maximum inductances in a single - layer coil the limits should be kept somewhere A HANDY and useful accessory has recently about an equal value for the length and di- been placed on the market by a number of ameter. manufacturers ; it consists of a battery cable Coils in other shapes than cylindrical all will which usually comprises five leads of dif- need a longer length of wire for a given in- ferent colors bound into a single cable. The ductance and therefore the ratio of inductance to colored leads make it easy to tell which resistance will be smaller with a corresponding should be used for the "A" battery positive reduction in the overall efficiency of the coils. and negative wires and the "B" battery posi- The distributed capacity can be considerably tive and negative wires. lowered by spacing the turns slightly on the The use of such cable will go a long way tube upon which the coil is to be wound. to eliminate mistakes in connecting up as well Sizes of wire should lie between No. 18 and as making a much neater job in hooking up No. 30 inclusive, to hold the resistance at radio - to the battery. frequencies used in broadcasting and other The antenna wire should never be con- short -wave work, down to a lów value. There nected in the same cable as the battery wires, is not much difference between any of these however, as this would make too high a sizes. capacity between the antenna and ground The coils may be wound with either double parts of the circuit with a corresponding loss silk covered copper wire or with copper wire in signal strength with one layer of cotton and one layer of silk.

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Pure DC Power Supply for a The Rectifier Five -watt Transmitter In making up a rectifier for use with an ama- Too many teur transmitting set the usual practice is to amateur transmitting stations use a miscellaneous in operation today have an alternating cur- collection of jelly glasses rent note that produces inter- for the jars, and strip lead and aluminum for considerable the metallic elements. is ference. It is true that many of these There no question have but that such a combination will work -prob- rectifiers and filters in the power sup- ably ply circuit, but still the as well as any other materials -but at best signals transmitted such a rectifier is carry the unmistakable hum of AC an unsightly mess. A recti- an fier which is much more pleasing in appearance modulation. Probably not more than ten or and which fifteen percent of the amateur stations have does not become crusted all over a really with crystallized solution can be made as easily, pure, steady DC output, in spite of and with the fact that the great majority of owners have little more expense. It is such a recti- gone to the trouble and expense of equipping fier that is to be described here. their stations with rectifiers and filters. In The parts needed are: many of these cases the rectifier is not func- 24 half pint "salt mouth" bottles, and cork tioning properly, although, of course, there are stoppers to fit. See Figure 3 for dimen- numerous cases where the filter does not have sions ; sufficient inductance, or capacity. 9 feet of aluminum rod, 5/16 inch in di- Many amateurs blame their trouble on the ameter ; use of short waves, claiming that it is impos- 9 feet of lead rod, 5/16 inch in diameter; 2 feet sible to obtain a good DC note on short wave- of glass tubing, % inch in diameter ; lengths. Others are laboring under the im- 48 round head brass 6 -32 machine screws, pression that a pure DC note is so sharp in / inch long ; tuning that slight swinging or unsteadiness 1 package "20 Mule Team" borax ; makes it unreadable. 1 can lye; The tone quality of the note is not in itself 6 quarts distilled water. important, but when the air is full of static Before starting with a description of the con- there is no question but that the high "birdie" structional details, a word of warning should be note of DC gets out at distances that cannot given regarding the metals used. It is essential be approached by AC or poor DC notes. that both the lead and the aluminum be chemi- In tests macle at one of POPULAR RADIO'S cally pure. It is wise to purchase the metal experimental stations it has been proved con- rods from a chemical supply house, because they clusively that a pure DC note is easily ob- usually carry only the purest of metals. It is tainable; that it can be made steady so that its also necessary to exercise the utmost care in sharp tuning qualities are not a drawback, and cleaning the metals and in absolute cleanliness. that it is more easily read through static or Use distilled water, which can be purchased other interference. Following is the equip- from the druggist, or from a storage battery ment used for supplying the pure DC to the service station. transmitter, using the 110 -volt AC house light- The first operation in the construction of ing line as the source of power. the rectifier is to cut the lead and aluminum The power- supply equipment to be described rods into 4 -inch lengths, making twenty -four lengths is for use with a transmitter using a single 5 or of each. Two holes should be drilled 71/2-watt tube. When larger tubes are used in each of these lengths, one down from the top the only change required is to provide suitable which should be threaded to accommodate the equipment to supply the higher voltage re- 6 -32 screws, and the other at right angles to quired and to increase the number of rectifier the first but not threaded as it is used only to jars. The reader may easily make these adapta- slip the connecting wires through. See Figure tions himself. 3 for the necessary dimensions and the posi- tion of the holes. Parts for Power Supply Unit for Set the Fire-watt Transmitter metal elements aside for the time being. Then prepare the cork stoppers as shown 1 Dongan type 01, 200 -watt power trans- in Figure 3. Three holes are drilled in each, former, voltage output 550 each side of the outer holes for the metal rods and the center tap ; center hole for a one -inch piece of the glass 1 Dongan type D7, 80 -watt filament supply tubing. This latter serves as a vent pipe anr'. transformer, voltage output 8, with center also permits the addition of distilled water from tap ; time to time to make up for evaporation. To 1 Acme 30 henry choke, 0.15 ampere current cut the glass tubing into 1 -inch lengths a carrying capacity ; three- cornered file is used. File a small niche 2 National Condenser Co.'s paper condensers, in the glass at every inch and then break the 2 mfd. capacity, tested for 1,000 volts; tubing at these points with the fingers. It will 1 Chemical rectifier (See below for con- be found that the break will be clean cut and structional data) ; square. 1 Double pole, single throw snap switch, 110 - The solution may now be prepared, or, it volt ; may be advisable to prepare the solution before 1 Allen -Bradley Radiostat (For use with the work described above is done, because the VT -2, UV -202 or C -302 tubes; not needed solution must settle for about twenty -four with the new UX -210 tube). hours before it can be poured into the rectifier

www.americanradiohistory.com IN THE EXPERI:IIENTER'S LABORATORY s.z

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2/, D/HMETER"OF R' THE FINISHED RECTIFIER JAR FIGURE 3: All the necessary dimensions are given here for the assembly of a rectifier jar. Complete constructional data are given in the accompanying text.

jars. The vessel used for mixing the solution rectifier jars which is decidedly messy and un- may be an earthenware crock or an enamel attractive in appearance. pot. In making the solution for the model Now comes the cleaning process. The jars rectifier constructed in the laboratory two glass and corks should be washed in warm water with bottles, each of a gallon capacity, were used. soap, then thoroughly rinsed in clean cold These are convenient because the bottles can be water. Then they may be set aside. picked up bodily and shaken, thus mixing the The cleaning of the metal elements is per- solution thoroughly, and can be corked up while haps the most important job of all. In an the solution is settling, thus keeping the dust earthenware, china, glass or enamel vessel, out. mix one -quarter of a can of lye in about two The solution used is made up of six quarts quarts of boiling water. Do not use a metal of distilled water and the entire package of pot for this purpose and do not use enamel- borax. If the water is heated in a clean vessel ware if the enamel is chipped. Also be very before adding the borax it will be found that careful not to get any of the lye solution on the borax will dissolve more rapidly. How- the clothes or hands, as it will eat almost any- ever, it is not necessary to heat the water. thing it comes in contact with. Treat it with Mix the solution thoroughly until all of the as much respect as you would a powerful acid. borax has dissolved (if the water is hot) or un- Do not use it indoors if this can be avoided,

til no more will dissolve. Then set the solution as there are some fumes from the mixture r aside for twenty -four hours, during which time which are unpleasant to breathe and will tarnish the excess borax will settle to the bottom, or silver and other metals which may be in the crystallize on the bottom and sides of the vessel. Clean the metal elements one at a time, finish-. It is only the clear liquid that is used in the ing all the aluminum pieces before starting rectifier, so in dipping or pouring the solution with the lead. Hook a wire through the hole from the vessel try not to disturb the settlings. in one end of an aluminum element and lay Do not become impatient and use the solution it in the lye solution until it froths violently. in less than twenty -four hours, because this will Then remove it and rinse in cold running water. result in a creeping crystal formation in the Rinse it thoroughly, and lay it out on a clean

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Piece of cloth or paper. It is important not When the alternating current input to the to let the cleaned aluminum come in contact transformer is turned on with with the rectifier con - the hands or anything which will permit nected.across the transformer secondary, there it to collect grease or dirt. When the aluminum, will he a momentary rush of current through has been cleaned with lye it should he a light the rectifier circuit. This silver color, current will be re- almost white. If it is not, it is duced to practically zero within a few sec- an indication that the is aluminum not pure and onds, however ; an indication that the rectifier is unlit for use in a rectifier. is starting to form. Next clean the lead elements in the same It is well to leave the rectifier way, connected in using the same solution. The lead will this way for a few hours, as an aid to not froth as the form- did the aluminum. There will be ing process. Then it may be connected up to no visible indication of the cleaning process on the transmitter. The fortning the process will con- lead. Simply let each piece rest in the tinue in the ordinary operation of the trans- solution for about twenty seconds; then remove, mitter thereafter. wash and lay out on paper as with the alumi- It may be found that one or perhaps more of num. I)o not let the lead come in contact with the rectifier jars does the aluminum, not function as it however. should. One test for this is to measure the Everything is now ready for assembly of voltage drop across each jar the jars. To insert with an ordinary the elements in the corks, 1)C voltmeter. Measure one cell at a time. wrap a piece of clean paper around the lower If any of them show no voltage end of the element they are de- to protect it from the lin- fective and should be removed from the cir- gers and force the top end through one of cuit. It will be found the holes that the voltage across in the cork. An aluminum element some jars may be only half that across others, goes in one outside hole and a lead element in but these may he the left in the circuit. Any that other. The glass tube is placed in the are lower than half the voltage of the highest middle hole, as explained above. When the should be removed. two These may either be made elements and glass tube have been placed over with new solution and new in the cork the whole aluminum cork is inserted in the electrodes, or they may be left out entirely, as neck of one of the bottles, which lias been filled eighteen or twenty jars are almost to the sufficient where neck with the borax solution. the transformer voltage rating is between The jar is 500 then completed and should look as and 600 on each side of the center tap. shown in Figure 3. The lower ends of the The above description metal elements covers a rectifier suit- should he at least % -inch from able for an input of 600 volts to the hot1 mi of each half of the bottles. the rectifier. For use with a transformer hav- When the twenty -four rectifier jars have been ing an output completed of 1,000 to 1,200 volts each side thus far, they must he formed. This of the center tap a minimum of is most conveniently thirty -six recti- accomplished by simply fier jars should be used, eighteen in each half. connecting them up in the circuit in which they in any case it is well to are to be used, make up a few extra as shown in Figure 4. jars so that defective ones may be weeded out F/LTEP fECT/F/ER- -

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TO f/LAMENT 1--J THE DIAGRAM OF THE POWER SUPPLY UNITS FIGURE 4: The transformers, rectifier and filter are required to furnish a pure to the DC input transmitter, where the alternating current house lighting lines are used as the source of power. In "forming" the rectifier jars this circuit may be used without output connecting the filler terminals to the transmitter, or "forming" may be accomplished with the output con- nected to the transmitter. In the, rectifier portion of the diagram only eight jars are shown. This, of course, is not the number actually used.

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Then attach a small dial to the sha ft of the after- each movement of the vernier condenser. rear condenser. As in the case of all condensers, zero set- Next set the small vernier condenser so that ting is obtained in those its of the straight -line- rotor plates are about one -third meshed. irequency type when the plates are unmeshed. Now tune in a broadcasting station the same With the condensers specified for 'use in this way as with any two -control superheterodyne. superheterodyne receiver, however, It will be noted that when the loop is capacity tuned should he increased by turning the rotor in to the incoming signal it will be possible to a clockwise direction, as shown in Figure 1. hear the station at two different settings of the Never turn the rotor oscillator condenser (rear). in an anti- clockwise di- The lower of these rection from the zero point when using two points is the one that should be used. these particular condensers because then it will When the station has been tuned in with be found that the low -wave stations all fall within maximum signal strength, tighten the set screws a very small band in the connecting on the dial scale. If operated collar and the receiver will be properly, that is, in a clockwise direction, ready for operation with the single it will control. he found that the low -wave stations spread out It is advisable to balance the condensers on a over a goodly portion low -wave of the dial scale. This station. A good check may then be is simply another way of obtained by tuning in saying that the another station at the straight- line - frequency effect is obtained other end of the scale. If is only this found possible when capacity is increased by turning the rotors (it will probably he necessary to adjust the in a clockwise direction. vernier condenser slightly) the receiver is prop- erly balanced. It is also essential in balancing the condensers that both be turned somewhat If, however, it is found that stations at the clockwise from other end of the the zero point. Unless the rotors are both waveband cannot be tuned in meshed on the properly, even with the use of the same side of the condensers, the vernier con- capacity of one condenser will denser, try rebalancing the condensers with a be increased medium wave while that of the other is decreased, after the station, say around 380 meters. two have The leeway allowed in been coupled together to be operated the capacity of the ver- by the single dial. In that nier condenser should he sufficient then to case, of course, the permit tuning condensers will not be balanced on any wave- in high or low wave stations. length except When it is necessary to the one on which the balancing use the vernier con- process was carried out. denser to tune in a station with maximum vol- ume the main tuning dial should he readjusted -S. GORDON TAYLOR

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Kadel & Herbert "WITH MUSIC BY THE HOTEL SAVOY ORCHESTRA" By the simple but ingenious idea of installing a receiving set on his coffee stand, this humble restaurateur furnishes his guests with the same music as is enjoyed by the patrons of London's swagger hostelry.

www.americanradiohistory.com CONDUCTED BY I. Axi)RE\Y WHITE l this department the Dean of Broadcasters a hosc voice is known to millions of broadcast listeners-records stems of intcrcst and ,'alnc to all radio jans ("Very-Where.

Will Wavebands Supplant duc home. The operator \\as the son of Fred I ramlec, Secretary ticneral of the Council of Street Bands? th Trade Union Congress. it appears that the thrill that come; once in a lifetime to the small boy is to become even "Rag Chewing " -by Radio more rare in occurrence, with the possibility in sight that the brass hands which have since Tice ability to carry on a successful liali- time immemorial headed street parades arc to hour's conversation appears to he the sole re- disappear from the leading position of these quirement for membership in the novel organi- processions. Such a fell hlnw at tradition zation known as the "Rag C hewer's Club," but landed in Chicago recently, it is reported, when when it is added that this must he accomplished W transmitted hand music so successfully to by radio and the friendly confab over the ether the open air parade which opened the 1925 waves directed to and maintained with one who National Radio Exposition that the marchers is already a qualified number, then it is under- completed their procession along Michigan Ave- stood why tho;, who have accomplished the nue to the home grounds without the aid of the feat compose an honorary group of the nicm- customary marching musicians. The parade bership of the American Radin Relay League. carried with it a number of radio receivers and The unique fraternity of amateur radio Bien powerful amplifiers which supplied the full vol- has already enrolled several thousand enthusi- ume of brass so clearly that another pioneering asts in the few months of its existence, and the achievement in a new field for radin was voted roster shows that there arc friendly conver- a complete success. sationalists of the requisite ability in every state in the Union. in every province in Canada, and that six countries in Europe and , \sia are A Princely Tribute to a represented. Radiornan IN the reports of the rousing welcome \which Heat, Light and Power was extended to the Prince of Wales when he via the Ether? arrived home after his 5.0(X) mile voyage to South Africa and South America, considerable Co1x('IDENT with the announcement of the space was devoted to the manner in which the amateur half -hour air talkers organizing them- heir to the British throne recognized per- selves, comes word from London that science sonal services of the officers and others in the is scheduled so to improve things that the very official party and the distribution of numerous foundation of this particular organization is gifts and souvenirs. Yet that \which was prob- threatened. That is, if we are to take seriously ably the most considerate act of all received the prediction of Professor A. M.- Low, who is scarcely any notice. it was the speeding up quoted in the daily press as saying: "The de- of the battle cruiser Whit/se so that she would mand for speed and yet more speed will shorten arrive at Spithead earlier than originally in- business conversations to a matter of seconds tended, in order that a young radio operator or fractions of seconds.. A few rapid facial on board the vessel would he enabled to attend expressions and some thought waves will serve the funeral of his father, who died at London the purpose of the present day thirty- minute several days before the returning voyagers were conversation." 89

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Professor Low pre'd'icts a lot of other: things, . the -ban went -ifíto effect, arid, even the smallest including the transmission. of power by radio, Vefiezùelan- villages; it is said, have community because radio waves and light waves are tl ;e listening -in - parties. same; it is only a question of the length of tthe * * * wave. It is confidently to be expected therefore that some day scientists will shorten the radio The Effect of Radio on Home Life wave to the length of .light waves, and then WC will have radio light. And.'since._heat is IN a conference on modern parenthood held also a type of wavelength, he sees nothing im- under the auspices of the Child Study Associa- probable in science converting the heat at the - tion of America at New York, radio was held Equator into radio waves and broadcasting to be an unínixed blessing to family life, though

them to the poles, where, of course, the,process - the automobile and the motion picture were would be reversed with reconversion into -heat thought to be disturbers of hearthside -unity. waves. He concludes that this power "will be This viewpoint was presented by Dr. John M. free like water." . _ Cooper, associate professor of sociology at the All of which was current and snappy conver- Catholic University, Washington, D. C., whose sation when I entered the radio held more-than. subject was the effect of- machine made recrea- fifteen years ago -that is, all except the part tion on family life. The topic followed a which predicts the furnishing of power free. lengthy discussion of whether religion tended That is new, so the item stands. to unite or separate family, groups into factions because of the serious problem presented to many - conscientious parents, who, themselves How Broadcasting Settles the subscribing to no given faith, yet felt that their children should receive religious training. Labor Problem in Venezuela 'k * * A STORY worthy of an O. Henry setting is contained somewhere within the dispatch from Bangkok Takes to the Air Venezuela, that the Government has tempo- rarily, banned radio receiving sets because they BANGKOK is now broadcasting. The first keep people there from working. It appears important program in Siam, it is reported, was that Venezuela has a large number of listeners, arranged by the Signal Corps of the army, considering its population, and many of them with the assistance of the cavalry band, the give up their afternoons to enjoyment of broad- musical selections and some news items pro- casting instead of going back to work after vided by the local newspaper being received lunch. An official ban was put on afternoon at five installations located at Hua Hin, Ayud- programs, therefore, several months ago, but huz, Korat and at two of the official palaces. operators on ships entering Venezuelan harbors Satisfactory reception continued throughout the and in private broadcasting stations in the oil three hours scheduled for the program. belt, over whom the Government had no con- * trol, continued to send out daytime programs A "Minister of Communications" and to cope with the situation the Government was forced to the expedient of barring the im- CUBA may be establishing a precedent that portation of receiving sets. This has resulted the United States may follow in unifying its in a marked increase of popularity of the own- communication activities under one head. The ers of sets which reached the interior before Cuban Director of Telegraphs appears to be

Kadel & Herbert FIFTY -FIVE WORDS A MINUTE WINS THE CONTEST FOR CODE RECEPTION Fifty-five words a minute were received and recorded without an error by Joseph Chaplin in (

smiling operator seated third from the left. .

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Fotograms THE FIRST RADIOPHONE BOOTH ON AN OCEAN LINER , Telephone booths from which the passengers can ring up and converse with shore stations or other ships within a few hundred miles radius, have been installed for the first time on the ocean liner Berlin. The phone is connected directly with the ship's radio room where all the transmitting and receiving apparatus is located. the administrative head of radio activities, in a Canadian amateur as the first recognition of the new order which has created a deiiartnrcnt a suggested improvement in the reception of pic- to handle matters pertaining to radio, teleg- tures by radio. G. J. Shadick, of Regina, Sas- raphy, posts, railway, ship and air lines. The katchewan, was the radio enthusiast to will Government of Cuba, a member of the interna- the first award, his recommendation being to tional convention, controls eight commercial use a blank sheet of paper on the recording or stations and all radio except broadcasting, which receiving cylinder of the radio apparatus, being operated for entertainment and not for around which he proposed to wrap a sheet of gain, is permitted to be carried on in private ordinary carbon paper, the movements of a hands. Thirty -six broadcasting stations arc in metal stylus over this sheet of carbon paper operation: among the larger is that owned by reproducing the writing or drawing transmitted the telephone company, PWX. Another is from the sending set. The plan is an obvious operated by the tobacco monopoly. Only ten improvement on the pen and ink method now of the broadcasters operate with one kilowatt in use. Two additional awards are to be made or more power incidentally, although Cuban call prblic later by C. Francis Jenkins, the Wash- letters áre familiar to American fans all over ington inventor. who has announced that prizes the country. aggregating $175.00 every two months will he presented to fans who offer practical sugges- Cash Prizes for Radio Fans tions which can be adopted for improving the Jenkins method of transmitting pictures . by A PRIZE of fifty dollars has been awarded to

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Fanatical Censors Now Seek to Standardization _there looks impossible. \Ve Ban all have individualisms of pronunciation, and "Indecent" Music that seems to be a good thing. After all, ALMOST any radio fan will agree that there whether we agree or disagree with the way the is a lot of "crazy" music on the air these nights, other fellow says it, what does it matter? but few would undertake to say that any of it Houston in Texas and the street of the same is "indecent." The problem of determining that name in New York sound entirely different cry difficult difference, however, came up re- when spoken by natives of the two cities, and cently in the capitol city of our fair land, when Greenwich and Haverhill and Los Angeles are from a musty file of police regulations some others it is immediately apparent it would be one dug up an order forbidding "indecent hard to get together on. Personally, it is music" and put it up to the Washington guardi- rather a pleasant shock to me to hear someone ans of law and order to enforce the official on the air who happens to live in another part "don't " -if they can agree on what it pro- of the country pronounce a name a little dif- hibits. The difficulty seems to rest with de- ferently from the way I do. I figure. that he ciding whether swaying intonations are to be is right, and so am I, for that matter; we both blamed for men forgetting home and babies, understand each other, anyhow, and, after all, temporarily, or %yhether the important thing is that is all that matters.- that the torn- tummy sort of Oriental music * * * should be confined to its. point of origin, some- where in the deserts, where, as one of the 96 Hours of Continuous policewomen said, "the desert natives have sel f- Listening In respect enough to dance by themselves." At Last reports the authorities were wide apart in ENTHUSIASTIC fans have made all manner de!ining a standard. of boastful claims as to the number of continu- ous listening hours they have put in at a radio Will Radio "Standardize" receiver, but the most ardent dial manipulator will certainly have to sing low in the face of Our Speech? the claim of Mike Newman, veteran showman, who recently drove from Los Angeles in the liko:\D(.\sTING; is suggested as one means interests of a movie film and announced of standardizing speech by on his none other than arrival that there was no such thing as Poet Laureate Bridges, in a tract of the "silent So- hour" on the trip across country with a radio ciety for Pure English. That seems to be a receiver mounted good thought, hack of the driver's head so far as it goes, for radio may going practically all the ninety -six \yell be called a monitor of enunciation. hours and But fifteen minutes running time required to travel pronunciation -that is quite another thing. 3,370 miles of the journey.

G. Crowther. England A SHORT -WAVE TRANSMITTER THAT HAS COVERED OVER 5,400 MILES Communication in daytime with a Rio -de- Janeiro amateur, M. Fresin, is the accomplish- ment of this English amateur, Herbert Hiley (G21.H.) of Keighly, Yorkshire, England. The transmission was made with a Hartley loose -coupled circuit on a wavelength of 42 meters with 15 watts on the aerial.

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Kadel & Herbert CHIMES THAT PEAL ACROSS A CONTINENT By the simple expedient of bringing the microphone into the belfry of the Park Avenue Baptist Church in New York, the music of the famous carillon presented by John D. Rocke- feller is now broadcast as a regular feature from Station TYJZ.

a Station would like to enroll in this new auxiliary serv- Only One State Without ice are invited to get in touch with the Corps NEVADA is the only state in the Union which Signal Officer of their own area, Corps headquarters being located in Boston, New now has no broadcasting station. Wyoming .. was out, but the licensing of the new station, KFBU, York, Baltimore, Atlanta, Columbus, Chicago, at Laramie, brings the state of large plains back Omaha, San Antonio and Presidio, Cal. to the fold.

The World Buys American 16 Percent of American Homes Radio Apparatus Have Radio ONE of the latest estimates of TWENTY -NINE countries of the world are now the extent of radio equipment, and the radio is that there are approximately sixteen importing American receiving sets to every one hundred American estimated total for the year hás' been seta at _ record. In the first eight homes, compared with fifty -two automobiles $8,334,000, a new and thirty -six talking machines. months of 1925, the orders ran nearly three Figuring on dollars more than for the same period that basis the conclusion is reached that seven million years more will be required for the number of pointing to Japan . last year, with the indications radio sets to pass the number becoming our largest customer, with Canada of phonographs. and Great Britain respectively second and third. * * * * All Wavelength Limitations Are An Amateur Radio Net to Cover Off-in Esthonia the Country ALL wavelength limitations in broadcasting AN amateur radio network covering practi- have been removed in Esthonia, a matter which cally the entire nation is being prepared by the will be of some interest to designers of radio Signal Corps with a view to securing the aid of receiving equipment who have been handi- some 3,000 amateurs for the establishment of capped in building sets for foreign markets additional communication channels which could which, as in the case of Esthonia, have up to be used in national emergencies and for the now so restricted the operable band of wave- communication of the national guard and the lengths that the ordinary type of broadcast re- reserve and civil units of the army' Those who ceiver could not be used.

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Hotel Has Radio Rental Service regulations are made and call letters assigned to the various subscribing nations. RADIO service for guests has been started at * * une ut Nrw l ark's leading hotels. A six - tube purtable receiver is placed in one's room Radio on on a reasonable renting basis. The sets are Gondolas kept iu the electrician's utlice and may be rented IT is reported from Venice that radio ama- by notifying him. teurs there have hit on a particularly bright * * * idea to attract tourists to their particular crafts. Many of them, fortunate possessors of gon- Radio As a Dramatic Plot dolas, have fitted them up with receiving sets, and go floating along the canals of a moonlit RADIO plays a leading r 1e in a rollicking eight. The effect is surprisingly romantic German comedy entitled when "1

Kadrl X Herbert srimmunr A GLASS -INCLOSED RECEIVER The noted doctor and X -ray specialist. Dr. F. L. Satterlee, demonstrates using his circuit that is claimed to work without a set operation an antenna. The theory of is based upon a tuned-ground system.

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I uv ni .cioual BROADCASTING "SIDE- LINE" REPORTS OF BOAT RACES One of the features of this summer's regattas was the running account of the progress of the boat races, made by "radio reporters." This picture shows J. Andrew White talking into the microphone on the yacht "Elco," broadcasting through Ir1Z.

authorities that radio broadcasting is of defi- Long Distance Receptio_ on nite value in classroom instruction. Dr. Virgil Crystal Sets E. Dickson, head of the department for "re- search and guidance" in the Oakland public LISTENING to programs broadcast from schools, who is carrying on this experiment London through the long winter nights is the finds that the subjects best suited to broad- engaging prospect held out for owners of casting are penmanship and drawing; in draw- simple crystal sets, according to announcements ing, particularly, radio has stimulated greater made by the Radio Corporation that all ar- originality on the part of the pupil than has rangements have been completed for an ex- instruction that is given by the teacher in per- change of British and American programs, at son. Entirely new fields of possibility have least several times a week and perhaps nightly. been opened by the experiments, and a new era The music and speech will come from the new of educational methods may result. seventy -five miles from station at Daventry, * London, be picked up at Belfast, Me., and re- * transmitted through the new WJZ station-at New Brunswick,, N. J. which is. to be oiie The Patron Saint of Radio Fans hundred times as powerful as.the present WJZ. THE autmobilists have already chosen their patron saint, who is St. Christopher. But the Californian Schools Use Broad- radio enthusiasts have not yet designated theirs. The new French publication, "La T. S. F. casting Regularly pour Tous," is organizing a referendum carried on among its readers in order to learn their EXPERIMENTS that have been The first results of eight months at Oakland, opinion on this subject. over a period be in favor of Joan of Arc. California, have convinced the local educational seem to

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CONDUCTED BY WW'ILLIAM G. I I. FINCH Titis department «ill keep you, in touch rcit /t the latest inventions of interest on which ratent rights have been granted. and which are significant contributions to radio art.

A Novel Cone Loudspeaker tially parallel with its normal position. This should result in improving the quality and quan- DR. HANS SCHARF of Berlin was granted tity of the reproduced sound. patent No. 1,540, 2'9 for a cone-shape loud- The soft material, speaker. i.e., rubber used for holding the diaphragm, is preferably stretched over the In loudspeakers that employ the usual type of whole surface telephone of the diaphragm or it may be receiver in combination with a horn, solidly connected therewith around its one drawback lies in periphery. the fact that not the entire Due to this provision the vibration of the dia- surface of the diaphragm is exposed to the air. phragm will be materially damped. Furthermore, during its movement the dia- In Figures 1 and 2 these phragm produces features will be noted; objectionable noises because also that the diaphragm is cone -shaped of metal; it is rigidly held around its periphery. it is entirely covered In this invention with a piece of rubber cloth. these drawbacks are avoided This is a feature that is not found in domestic by holding the diaphragm around its periphery cone -type speakers. in a manner that the diaphragm contacts only with sonic soft material, preferably rubber, and the whole surface of the diaphragm is exposed to A New Radio Receiving the air. System The diaphragm disclosed in this invention THE Commissioner of Patents recently allowed moves practically freely in the air and substan- 56 claims to Oscar C. Roos of Boston, in letters patent No. 1,545,697 covering a very novel electrical acoustic method of reducing inter- ference and static disturbances in radio phone receiver; which possesses considerable merit. The invention relates to broadcast receiving systems and more especially to such systems whereby the effect on the signal- indicating device of electrical vibrations created in the system by abrupt or impulsive electrical forces (such, for example, as "static disturbances" or electrical vibrations created in the system by interfering signal waves), is eliminated or reduced to a minimum so that the signal -interference ratio is a maximum. Mr. Roos has discovered that the in- egular non -musical noises or non -harmonious vibrations produced by a signal- indicating device, such as a telephone receiver when the receiving system is acted upon by abrupt or impulsive electrical forces, may be converted into spatialized periodic vibrations. In carrying out the invention, he provides means for converting the electrical vibrations e developed in the receiving system by abrupt or impulsive electrical FIGURE 1: Top forces. The electrical vibra- view of Scharf loudspeaker in tions developed therein by which a few details of construction the electromagnetic are shown. waves, the energy of which is to be received into 96

www.americanradiohistory.com WITH THE INVENTORS 97 dephased specialized non -electrical vibrations, such, for example, as sonorous vibrations pro- duced in an air column, and an apparatus so associated with such means that the amplitude B therein of the non -electrical vibrations resulting from the waves, the energy of which is to be received is large compared to the amplitude therein of the non -electrical vibrations resulting from the abrupt or impulsive electrical forces, FIGURE 2: Cross section view of the new Scharf and a signal- indicating device associated with cone -type of loudspeaker. said apparatus. The non - electrical vibrations which páss into the apparat us may be converted sound waves produced by the signal waves at a into electrical vibrations by any suitable means, point where the amplitude thereof is large com- and in such case a signal -indicating device is pared to the amplitude of the stationary sound operatively connected with such means. wave formed by the electrical disturbance; for The invention comprises means for converting example, at a pressure loop of the former and a the irregular complex noises produced by a signal - pressure node of the latter. indicating device (such as a telephone receiver) Having separated two sets of sound waves when the receiving system is acted upon by and picked up a portion of the energy of the abrupt or impulsive electri cal forces into well stationary sound wave formed by the signal defined steady acoustic vib rations of any con- vibrations, use may be made of it for producing venient pitch. This means consists, for example, the signal or one may employ apparatus such of a resonant air chamber so designed that when as a radic transmitter for reconverting such sound the confined body of air therein is shockcd into waves into electrical vibrations, and transmit vibration at its own period, an acoustic vibration the latter to a radio broadcast receiver. By different in pitch from that of the signal will be transmission through several stationary -wave produced, the pitch of which signal is under separating devices in succession, further separa- complete control of the operator by means of tion of the signal and interference vibrations may the heterodyne. The complex sound, consisting be affected. of the acoustic vibration produced by the signal It is also contemplated to use a sound reflec- waves and the non -musical noise produced by the tion or refraction device whereby the sonorous electrical disturbance, which is introduced into vibrations produced by the signal waves after the air chamber, will produce a resultant complex separation from the sonorous vibrations pro- vibration which is the sum of its components, duced by the electrical disturbances may be but which, when of audible pitch, is different in concentrated on the apparatus which reconverts sound from either. them into electrical vibrations. The invention also comprisses a means for It will be obvious that the principle underlying spatializing the two sound waves that make up the invention may be embodied in a great variety the resultant acoustic vibration, such means of apparatus and that various circuit arrange- being, for example, a resonant air -chamber of ments may be employed in connection therewith such dimensions that the two sets of vibrations for converting the energy of electromagnetic will produce stationary sound waves. These, waves into sonorous vibrations at one end of being of different frequencies, will be dephased. the apparatus and for converting sonorous vibra- Means are provided for picking up the stationary tions into readable signals at the other; and

FIGURE 3: A schematic diagram of the Roos radio receiving system. It is a very novel electrical acoustic means for reducing interference and static disturbances and possesses considerable merit.

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A New Crystal Detector FERDINAND SCHNEIDER was recently granted U. S. Patent No. 1,549,926 for a new crystal detector. His invention relates to that class of receiving devices for damped or undamped electric waves, on which a gap between electrodes is bridged over by means of a preferably spherical mem- ber of wave- reactive material, i.e., a crystalline substance which is responsive or sensitive to electric waves ; for example, silicon, molyb- denum glance, pyrites, carborundum or the like, said wave reactive member being subjected to pressure. He has found that members composed of such wave- reactive material have not a uniform sen- sitiveness throughout, and therefore make these members movable along the electrode gap, pref- erably by means of rotation around their cen- ters ; this insures that the most sensitive points of the wave -reactive member or members can be brought in contact with the electrodes. Another feature of the invention is that the

FIGURE 4: This shows a cross section view of the Sandell radio frequency transformer; the movable _feature of the iron core may be seen in the above diagram.

therefore, it will be understood that the several embodiments of the invention described are illustrative merely and not restrictive.

A Radio Frequency Transformer A NEW design in radio frequency transformers is shown in patent No. 1,541,398, issued to Henry Ií. Sandell of Chicago, Ill. It is particularly -._ adapted to be used for radio frequency amplifica- tion in radio receiving sets. A feature of this invention is the design (see Figures 4, 5 and 6) the construction of which provides a radio frequency transformer in which the iron core is movable and the de- saturation time of the iron is varied. By properly choosing the values this time may be brought into step or resonance with the natural period of induc- tance of the secondary coil. The primary is aperiodic and the secondary is periodic or resonant for the present broadcasting frequency band. In other words, varying the iron in the core varies the frequency of the secondary coil so that by this means the res- onance of the circuit in which the secondary coil is placed may be tuned. When this occurs the strength of current that flows in this coil is 1 greatly increased. The relation between the soft iron core and the secondary is very sensitive to small changes in either, while relatively large changes in the primary are permissible without materially altering the operation of the trans- former. If desired short pieces of the soft iron wire may be embedded in a non -magnetic substance Il11l1,. to form the movable core and by properly pro- FIGURE 5: Is another view of the Sandell portioning this the wires 12 (Figure 6) may trans- omitted be former, completely assembled; in this diagram can altogether from the final design or as- be noted an important s: mbly. detail-the means for ad- justing the iron core.

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70

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FIGURE 6: This shows the iron co e assembly. pressure exerted on the wave -reactive member urinal plugs .on the tube. In order to adapt a or members is made adjustable so that the socket for use only with oneetype of tube, this effect may be increased. By roughening the invention comprises the provision of a plate of edges of the electrodes in contact with the insulating material which is interposed in a wave- reactive member, or by bending elec- plane between the terminal springs and the trodes of sheet metal, the inventor increases the plane of the base of the tube when in position number of points of contact and finally forms in the socket. This plate is provided with suit- the wave- reactive member or members from the able apertures which are definitely placed angu- most wave -sensitive parts of the reactive sub- larly with respect to the bayonet slot of the stance, which he ascertained by previous ex- particular socket to which it is adapted, so that periment. By this means the specific resistance the terminal plugs only of the tube which is to is considerably reduced, so that weak- current be used with this socket will properly fit the relays connected up can be used without the aperture in the above -mentioned insulating plate hitherto necessary intensifiers or extra sources and thereby pass therethrough to make contact of current, because speeches or sounds are re- with the terminal springs. ,eived with a more powerful clear tone. A New Vacuum Tube Socket A New Inductance Coil and Tuning Methods IN patent No. 1,547,729 issued to William T. Booth of Brooklyn, N. Y., is disclosed a new FRANCIS DE WILLY of Los Angeles, Cal., was and improved form of tube socket structure recently issued Letters patent No. 1,549,247 for to be used in vacuum tube sets and telegraphy improvement in "Inductance Coil and Tuning and telephony. Methods." One of the objects of the inven- An object is to provide an improved socket tion is to provide a transformer for an elec- structure so that a socket in use with one form trical circuit or radio apparatus which is ex- of set and adapted to be used with one type of ceptionally efficient in operation in comparison tube, cannot be used with any other type of tube with the present type of transformers. while in that particular use. Other objects of the invention, as set forth Another object is to so construct the socket in the patent, are to provide a transformer oper- structure that the new element added which ating to prevent re- radiation of energy from the constitues the invention, may be readily adapted receiving apparatus ; operative to absorb or to or removed from the socket structure. take up a maximum signal strength ; operative In the ordinary vacuum tube socket the tube to reduce the outside magnetic field around the fits by means of .a bayonet and lock -joint into transformer and thus eliminate undesired the socket, the terminal plugs at its lower end coupling with other units of the receiving sys- slightly contacting with a plurality of terminal tem ; and operative to provide a coupling for a springs. the ordinary tube these terminal radio apparatus tending to stabilize the action plugs on the base of the tube are definitely po- of the apparatus and to increase the range and sitioned angularly with respect to the bayonet signal strength. pin also on the base, and similarly the terminal Another object is to provide a simple form springs on the socket are definitely positioned of detecting circuit for a wireless receiving set,

angularly .with respect to the bayonet lock so operative to . efficiently amplify signals receivei that when the tube is in position definite ter- while providing a sharp tune and stable ap- minal springs will contact with definite ter- paratus which may be constructed at a low cost. A Cardinal's Impression of Radio "BY common consent, radio is a force of immeasurable potency. It will unquestionably affect the history of humanity as electricity and steam and the printing press have affected it. We may say, in a certain sense, that radio surpasses these and other agencies, for it is able to influence millions of people scattered over the earth profoundly, instantaneously. It is one of the greatest powers that man has ever had in his hand." -CARDINAL HAYES

www.americanradiohistory.com LISTENING IN PRACTICAL pointers from experimenters and broadcast listeners. What helpful hints can YOU offer to your fellow fan? Readers are invited to address their letters to the editor of this Department.

CONDUCTED BY LLOYD JACQUET

How to Avoid an Uneven or so. But a mistake is made when 45 volts are fed the detector tube, for the drain increases Battery Drain one hundred percent. If you want to make the first "B" battery last I NOTICE that when my `B" batteries have as long as your reached the other batteries, reduce the extra point of recharge, it is usually the drain on it as much as you first 45 -volt battery can by using mini- that is discharged first. mum voltage of the detector tube, consistent A little curiosity enabled me to find out why with good results. this was. By studying the diagram of con- It might, in fact, be a good idea to change \\/

DETEC7AP O iF O O-ot O O

nection, I noticed that the drain on this bat- tery was greater than on any other therefore and that 01111110-- its energy would be used up in a smaller unit of time, as compared with the other batteries. % ES EZ 4oL TS AE E 5/pPL OFTyE/ñST4/tTB9T7EprfLeEFT EOBY A HOAL Indeed, I can see that besides supplying en- Y . J`U P p y Y/N4 90 ,Voi Tp THE ergy for the detector tube, through the tapping r AAl PL /F/E. PS. of the first 22% volts, and being connected in the plate circuits of the amplifying tubes, this battery is being overloaded this much more. If the voltage is only 22% perhaps the current drain is low, of the order of V milliampere 100

www.americanradiohistory.com LISTENING IN 101

the position of the first and second sets of I bought one dozen of them, assorted in batteries occasionally. sizes. I tried every one of them, but with little -ED DOWNING, Brooklyn, N. Y. difference in efficiency than the original one in my set. I found three or four of them, how- a ever, that really made a big difference in my Short Waves On Crystal Set receiver. THERE are many short -wave broadcasting It has been my experience that grid -leaks are stations now operating which have programs not always uniform, either in resistance reading, just as interesting as the longer -wave stations. or in performance. Unless an excellent make In fact, some of these short -wave programs is used, you can never be sure of the resistance are repetitions of the original broadcasts. value. This, however, has little to do actually Most broadcast receivers are so designed that with the actual performance of the unit. they will not tune below 250 meters: For those Have a variety of grid -leaks on hand and who ai`p curious yet who do not .feel as though experiment to find the best one. Not any old they want to invest much money in the recep- grid -léak will do. It is sometimes necessary to tion of short -wavelengths, the crystal set offers go through a bunch of them to get a few good great possibilities. ones. Buy only the best you can afford. A crystal receiver can be built with odds and -C. STEVENS, Trenton, N. J. ends about the house. Get a variable condenser, * * x a discarded coil, and a crystal detector. The Fieldless Coils circuit can be completed by means of a few small fixed condensers. The hook -up is sim- I HAVE already seen diagrams and articles plicity itself. One of them was given in referring to the use of the new types of coils, POPULAR RADIO for May, 1922. known as the "toroid," "doughnut," and other Wind only 30 to 40 turns of wire on the coil. similar names, in which the constructor was Use your present antenna if you so desire, shown to place these coils at right angles to although a shorter one would be better. Then, each other. some evening when it is getting late, turn off In the old days of cardboard coils, inefficient your regular set for the crystal outfit and listen condensers and leaky transformers, such pre - in. With the big stations using super- power, cautions were imperative. But since these coils crystal reception is a possible thing within are supposed to be built to do away with the fifty to one hundred miles of the station. very nuisance that the writer of the article -HARRY BRANDE. San Francisco, Cal. warns against, it isn't necessary to locate these * * * coils at right angles to each other. Such construction proves bulky and difficult What I Found About Grid -leaks in many cases, and nothing is achieved by it. RECENTLY I had occasion to try out a friend's It is of far more importance to remove from grid -leak for him, while he was building his own any winding the metallic masses of transform- set, a one -tube affair. I noticed how much bet- ers, condensers and other units, which would Í ter his grid -leak operated than my own. I pro- create a real loss if placed too prominently in cured a new one, but it didn't function as well the electromagnetic field of a coil. as that of my friend. -JOHN L. SAWYER, Kansas City, Mo. /ST/9Mf'/f7fJ' 2P/944'PL /F/6t"

i- T

AN EXAMPLE OF AN UNEVEN BATTERY DRAIN Besides carrying the drain of the amplifier tubes, the first "B" battery also must take care of the de- lector tube. This imposes a greater drain upon it than the other batteries. Change the batteries around occasionally, and even up the drain. TM CS AMOUN TO0{/O L T5J /5 5UP P L/ t O BY TN'O Q5VaT6Z9TTER/t5TO fire H/HPL/F/ER5.

www.americanradiohistory.com POPULAR RADIO

of sealing wax or cement, the horns are fast- ened to the earpieces. If the horns are big, like the ones shown in the illustration, the effect when the set is turned on will be most pleasing. To add a touch of artistry, the interiors of the horns may be gilded, and a decorative rim placed on each. The horns work very well on this five -tube set. -LOUIS PASSEN, Chicago, Ill.

How to Handle Glass in Your Set GLASS is being used to a large extent by COW HORNS AS LOUDSPEAKERS experimenters who build radio sets. Because glass These cow horns, fifteen inches in length, is such a good insulating material, it make up the londspeaking part probably would be even more extensively used of this radio were it set. Even if they do look like periscopes, they not for the fact that it is hard to work. add an odd tone to any radio installation. How to drill glass has already been told in POPULAR RADIO, but many set builders have had the experience of cracking a finished glass * * * panel in the assembly of instruments. Glass will not stand as much strain as other A Novel Home -made Horn materials used in radio work, such as hard rub- ber, bakelite, fiber and others. But if the from the Farm strain is eliminated or relieved there is less danger of breakage. One way to relieve ALTHOUGH nearly every possibility for the strain this design of radio loudspeakers is by using care (when two or more has been thought mounting screws or nuts are located of, here is a new idea that has many merits on a piece beside originality. of apparatus) that one screw is not brought down tight first, and the others pulled up The cow horn, because of its very substance, ward. after- is clear- toned, and solid. The making of a When two good loudspeaker unit for or more screws or nuts are re- radio use out of a quired for mounting a piece pair of cow horns is simplicity itself. of radio apparatus, tighten up slightly on each screw or nut First secure a pair of horns; this will not secutively con- be difficult if you until all are brought up tight. This live on a farm. Cut the tips hint is good not only of the horns off with a when working glass, but mel hack saw and at a point is advisable in any case where where the it is necessary to MC opening thus provided will fit into eliminate the possibility the hole of a telephone earpiece. of strain or breakage. By means -W. A. FRICKE, Chicago, Ill,

eel

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Stat 0 bed Rea Att 0

A HOME -MADE SET ENCLOSED IN A GLASS CASE Glass is particularly attractive when it serves to enclose the components of a radio - set. Here is the work of a Chicago firm, who can drill with bushings glass and prepare the holes for mounting the instrument withOnt breakage.

www.americanradiohistory.com 1'. what an enthu,At, \1.. r. Thal lhala ,It,l foe this 1,r.aska.t Iitentt. A wrote u. after ht. hew night's erett he t.4.1 tt t.t us ow? his wn tRnaturt. And ht. bother wa. %1 N111)\ \t rttt fog. .itr t.L.irt. "l our [hai. 11t*thrr Ilk n. he had The tr hear.! befit _.,.e \Ie I die the 110-11 ' We will send iv en heard t,f' 'tatian. that tame in s. rwratsi to an ad.lrr..._ that he hadn't nwtm foe them all in Netter atll.gtrt the folder from %,t,r It ett 1e gar* he had left to ht. log Pot ' 1*rakr Reed it tin the epos and take tour at«rn. that kept ',wrong long after ht. %It. ro- [Vial home. You an install thin, /ttnw hair had rdb..e.l' s.ur+eFf without drilling or cawing, Anil t+'1 the atmrle .hav of what \1.. r- torn= n.. t.io1 but a .rtwdrrrr. ItAI)k) fr l'll1I`1t1NAI'N t ()\11'Atih ItN'VTfi r,:. st .+: t.t tlsti111 ttit .:natH , . A Ì a% ',wt.. tlepw. VI titimetr. 1`041t w %4., fa " .a P.Imparromke to V.. ! . r... . +.. . ^L. F .,d ."` F .111 W.-_° I rJ yYN w f.rs i t/ Ow d-.w .wii 1 \rr.. /*. eh tot tt

Micro.M w t'....-t+ w tt. ` -Dial

, , r., k - ,a 4 t., AS %tIt+ MN+o. 44 rH r,. so.. :,t ..-. «ww .t

www.americanradiohistory.com The Best in Radio Equipment What a Definite Policy Proved It is the policy of the Daven Radio Corporation to manufacture precision products which permit of no deviation. Daven Resistors and Grid -Leaks are guaranteed within 10% of rated value - Sleeper says we do better.

M. B. SLEEPER, Inc. TECHNICAL PUBLISHER St VANDERBILT AVE. NEW YORE

R.tho Engineering Book. of Teehold Accuracy Maw.. for Experimenten

July 14th, 1 9 2 5 .

Daven Radio Corp., 158 Summitt 3treet,. NewLrk, N.J.

Dear Mr. Frasse:

I gave myself a very pleasant sur- prise last evening. After reading Ghirardi's story about the method you employ in the manu- facture of gridleaka, I thought just for fun that I would check up on you. Accordingly, I measured about fifteen Daven gridleaks of var- ious sizes and found, much to my surprise, that every one that I tested was within 5% of the rated value.

It is very encouraging to think that, slowly, we are getting production on some parts, at least, to a point of perfec- tion where it is possible to put the device in a circuit and know that it will do what the label saya it should do.

Cordially,

M.B. Sleeper -MGM

* In March, 1925 issue THE RESISTOR of Radio Engineering MANUA 1. is the hand. book of Resistance Coupled Amplifies. tion. At dealers' 23e, By mail, postpaid 30e.

DAVEN PRODUCTS ARE SOLD ONLY BY GOOD DEALERS -CLIP THIS COUPON- - r - - - DAVEN RADIO CORPORATION, 1 73 Summit Stmt, Newark, New Jersey I Please send me the following on Resistance Coupled Amplification: fine SJrterite' Check one ID Resistor 30e enclosed. Manual. is o Completecatalog (free). I Name lA I o cjOgNAMAr Address Per r %r .5;oecial:scs' For dealers: Send your letterhead or card, or this coupon and Reg. U. Pat. Off. we will hare our nearest distributor communicate with you. Newark New Jersey THE BIG LITTLE THINGS OF RADIO

Alt apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

NO DIALS NO PANEL BUILT-IN or the `reell appointed dome LOUDSPEAKER PEOPLE of taste will instantly recognize in the ULTRADYNE, Model L -3, the long - awaited perfection in radio -musical instruments. This new receiver offers complete mastery of the air's riches; effortless operation -as simple as playing a phonograph; and a new artistic form with its environment. $13500 that blends harmoniously duo -toned West of the Rockies The ULTRADYNE, Model fully duco finished, -tube receiver panelled mahogany cabinet. $140.00 L -3, is a six Mr. employing the fundamental To protect the public, of the best circuits Lacault's personal monogram principles the greatly refined and marvel- seal (R.E.L.) is placed on No dials -no assembly lock bolts of all genuine ously simplified. Re- panel; just two inconspicuous ULTRADYNE Model L -3 levers which constitute a station - ceivers. All Ultradyne Receivers as these selector. Volume adjustment, are guaranteed so long the only other control. Beauti- seals remain unbroken.

Write for illustrated descriptive folder .}----...!

f I i

_ " _ , :_ J ,.- ULTPIWPE ...

l tr i. ?.. -f .sN - , ' PHENIX RADIO CORP., 116 E. 25th St., New York

RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved by POPULAR

www.americanradiohistory.com 102 POPULAR RADIO

of sealing wax or cement, the horns are fast- ened to the earpieces. If the horns are big, like the ones shown in the illustration, the effect when the set is turned on will be most pleasing. To add a touch of artistry, the interiors of the horns may be gilded, and a decorative rim placed on each. The horns work very well on this five -tube set. -Louis YASSEN, Chicago, Ill.

* * * How to Handle Glass in Your Set GLASS is being used to a large extent by COW HORNS AS LOUDSPEAKERS experimenters who build radio sets. glass Because These cow horns, fifteen inches in length, is such a good insulating material, it make up the londspeaking part probably would be even more extensively of this radio were used set. Even if they do look like periscopes, they it not for the fact that it is hard to work. add an odd tone to any radio installation. How to drill glass has already been told in POPULAR RADIO, but many set builders have had the experience of cracking a finished glass * panel in the assembly of instruments. Glass will not stand as much strain as other A Novel Home -made Horn materials used in radio work, such as hard rub- ber, bakelite, fiber and others. from strain But if the the Farm is eliminated or relieved there is less danger of breakage. One way ALTHOUGH nearly every possibility for the strain to relieve this design of radio loudspeakers is by using care (when two or more has been thought mounting screws or nuts are of, here is a new idea that has many merits located on a piece beside originality. of apparatus) that one screw is not brought The down tight first, and the others pulled cow horn, because of its very substance, ward. up after- is clear -toned, and solid. The making of a When two or more screws good loudspeaker unit for radio use out or nuts are re- pair of a quired for mounting a piece of radio of cow horns is simplicity itself. tighten apparatus, First secure a up slightly on each screw or nut con- pair of horns ; this will not secutively be difficult if you live until all are brought up tight. This '1 on a farm. Cut the tips hint is good not of the horns only when working glass, u off with a hack saw and at a point is advisable but where the opening in any case where it is necessary to thus provided will fit into eliminate the possibility the hole of a telephone earpiece. By of strain or breakage. means -W. A. FRICKE, Chicago, Ill. S

h

tf !Si Ts.

R

A HOME -MADE SET ENCLOSED IN A GLASS CASE Glass is particularly attractive. when it serves set. Here to enclose the components of a radio is the work of a Chicago firm, who can with bushings drill glass and prepare the holes for mounting the instrument withóut breakage.

www.americanradiohistory.com The Best in Radio Equipment

óair Dhib Boller Me Like the 1DkevDl99 That's what an enthusiastic Micro-Dial Dials did for this broadcast listener, as user wrote us after his first night's experi- he told it to us, over his own signature. his was STATIONS. ence. And bother Write for our folder, "Y our Dials Bother Stations he had never heard before -or Me Like The Devil." We will send it even heard of! Stations that came in so postpaid to any address. fast that he hadn't room for them all in Better still, get the folder from your Jewett the gaps he had left in his log book ! Dealer. Read it on the spot and take your Stations that kept coming long after his Micro -Dials home. You can install them bedtime hour had passed! yourself without drilling or sawing, and Read the simple story of what Micro- using no tool but a screwdriver. JEWETT RADIO & PHONOGRAPH COMPANY 5668 TELEGRAPH aOAD PONTIAC, MICHIGAN Factories: Allegan, Michigan - Pontiac, Michigan In Canada "Quality Broadcasting to Match Export Sales Office: Jewett Radio - Phonographs, Ltd. Quality Products -Station WJR" 116 Broad Street, New York City Walkerville, Ontario Jewett Mie Micro-Dial® 1925 Jew_in Radio and Phonozraph Co. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 12 The Best in Radio Equipment

Wonderful Volume with Clearness AMPL -TON i

REG. U.S.PATOFF.. $300 MODEL

Phonograph makers have spent years perfecting the u acoustic properties of their phonographs. Use an., AM PL -TONE Unit and make a real Loud Speaker in an.'I,t instant or use it in your horn and get better results. After all, speakers are as good as their unit. We a real unit at a real price. Money gladly make are not entirely satisfied. returned if you FOR WE SELL UNITS TO MFRS. Late at night when the family has retired, don't disturb then:. Use AMPL =CONE HEADSETS. They produce the and best results SET BUILDERS are un-urpasse I as a distance getter Price $5.00. FARADON MICA CONDENSERS, If since the advent of radio broadcast- P

ing, have been used extensively by el

the great broadcasting stations o throughout the country, and are now available for receiving sets, in the Model T. n

REG. U.S. PAT. OFF. You can buy direct from us also The UNION FABRIC CO. DERBY, CON MODEL Q T F F A A R R A A D The Model T brings distinctive ap- D O pearance to the set and permanent- O ly improves reception. For superior results use Model T's. Your dealer now has them or can get them for you. For quality at low cost.

No. 248 E -5841 REG. U.S. PAT.OFF. Underwriters ADP.

MODEL (4.I» T "Little Joe" Lightning Arrester Especially designed for Radio Work. fY.it.out with czracñ Made of Porcelain, small, neat, rugged and serviceable. Can be suspended on antenna or fastened to wall. Wireless Specialty Apparatus Co. Ask Your Dealer JAMAICA PLAIN, BOSTON, MASS., U. S. A. ELECTROSTATIC CONDENSERS for all PURPOSES M'f'd by CIRCLE F MFG. CO. Trenton, New Jersey Faradon

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATO

www.americanradiohistory.com The Best in Radio Equipment 13 continuous, unfailing "A" Power in a single compact unit ..that automatically replenishes itself

asks for a place A unique feature of Unipower is the single THE new Gould Unipower the opera- 1 in your set on this basis - that it will con - master control switch that governs conveni- tion of your entire set. When the switch is ON, ribute more than anything else to the with nce, perfection and economy of operating your Unipower feeds your set rich, quiet power you the most that your neither hum nor noise. When the switch is OFF, et - that it will give itself on a 'Loney can buy -that it will banish "A" battery Unipower automatically replenishes tilure, the most frequent cause of poor radio low trickle charge and with a minimum con- eception. sumption of current -a few cents a month. Here are the facts about Unipower. The first cost of Unipower is moderate -and the first cost is the last. When you also consider Unipower is a single compact "A" power unit that Unipower banishes dry "A" battery re- zat fits inside most radio cabinets. It takes the charging a storage storage newals, or the bother of lace of dry "A" batteries or of separate battery, and increases the life of your tubes, you attery and charging units. It is not a battery really is. You'll with any see how economical Unipower liminator and should not be confused find that it pays for itself over and over again. ther radio power device. today. The easily installed. Just Decide to see the new Unipower Unipower is quickly and nearest radio dealer has it. Ask him for a dem- onnect two wires to your set, plug in on your Battery Co., Inc., done! Unipower is onstration. The Gould Storage .ght current, and the job's Park Avenue, New York. quipped with an exclusive Balkite charger of 250 for years, pecial design. Unipower will last you booklet, "Unipower, no tubes, bulbs, lamps or working FREE! Write for interesting nd there are power" )arts that require frequent replacement. a triumph in radio

Unipower fits comfortably in- Unipower operates from alter - It is quickly natingcurrent,110 -126 V -60 cycle. sidemostsetcabinets. It is supplied in two types. The and easily installed. Connect two 4 Volt type is for sets using ÚV- wires to your set, plug in on your 199 tubes or equivalent and retails house current and you have con- for $36.00. The 6 Volt type is for tinuous, unfailing "A" power of sets using UV -201 -A tubes or hipoweTRADE MARK r and refine- the highest quality equivalent and retails for $40.00. command. West of the Rockies, prices are ment instantly at your slightly higher. (Special models, 25-50 cycle, are available.) On when it's off Off when it's on

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 1,1

14 The Best in Radio Equipment

MAGNATRONS in your set will give sweet purity of tone --. clear and complete rendition of all the wealth of overtones. Music and speech come from the loudspeaker of the equipped Magnatron set with rich fidelity and generous volume, recreating in your home the actual performance itself, whether it be ten or a thousand miles away. Magnatrons are the product of the oldest exclusive makers of vacuum tubes. That, in a large measure, explains their excellence. There's a Magnatron for every purpose. The DC-201A, the Dc-199 [large or small base], the DC -I20 [for super volume], and the Rex [for B now we'll Eliminators]. All list for only $2.5o each. Write for your FREE copy of "POT Pouiuu " -a snappyreviewofmirthand music toDepartment P. R. have clear CONNEWEY ELECTRIC LABS. Magnatron Building music Hoboken, N.J.

Complete factory stock for Pacific Coast carried at Pacific Radio Labs., 056 So. Los Angeles St., Los Angeles, Cal. 111 ,-1....1 )-.11.

Where you see these signs Replaces -II- in circuits-use a-- Dry Cells Cuts radio operating costs in half Allows constant, steady PcirtterBY-PASS power. New patented storage cell. Smaller than dry cells. More CO.desers powerful. Many times They prevent "B" voltage fluctuation as long -lived. Can be -Allow undistorted recharged from house amplification lighting current. The -Make possible full bass tones at all s most welcome radio ac- frequencies cessory of all times. -Improve reception with "B" Sup. Ask your dealer for Wonder ply Units Cells. If he is without them -Essential for building the new for the moment write direct Autoformer Amplifier to us and we will see that you are supplied. Send for FREE As easily attached as the "B" battery circular. Made in 1 /10, N, %, 1, 2, 3 and 4 Microfarad sizes THE HELIOS BATTERY CO. e.4t your Dealer's 71 Chestnut St., Boston, Mass. POTTER MANUFACTURING COMPANY North Chicago, Illinois

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORYJ www.americanradiohistory.com i i The Best in Radio Equipment 15

Ill 1

, 1- , , ( Jr, II - " IIII _,- 1'\: i ti?1/' G uYI ,, . _'I ... ,, Witi B radlleek Braabrometer PE tt8±In! A 4l 4 : 1 .s...,1.- . ::: . : : .. __ :

r:t= 13RuDjrswitch Bradnie tr $rachi y A r v III \ \M \I\I\INNpM1 \INIININI anmm IIIIIIItl111NNI1111NNIN /N \ \NIN\MK! _.MW Radio Parts t/iafworì4 ZDs HE keen, crisp winter nights are here! It is the open season for "long distance" -and more excit- ing, this year, with super -power on the air. New thrills await you if your set is adjusted for high- est receiving efficiency, and you are especially fortunate if Allen -Bradley Radio Devices are used for delicate tuning in the vital parts of your circuit. With the Magic of Graphite Discs at your command, you have new fields to conquer - new DX records to make. Allen- Bradley Radio Devices have stood the test of time and service, and the popular demand for them continues unabated. Have you noticed that the best known writers in radio publications invariably recommend Allen- Bradley Ì Radio Devices? They always work! Send for The Magic of Graphite Discs" .:... lsc USE THE COUPON ráp('tè RADIO aT L TO MV0-11x NTRT.HUTION. ALLEN -BRADLEY CO., ó 276 Greenfield Ave., Milwaukee, Wis. Please send me new illustrated circu- lar -"The Magic of Graphite Discs."

° Name s *=<._. nc>

and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested

www.americanradiohistory.com 16 The Best in Radio Equipment

QUALITY RODUCTS GENUINE BAKELITE Sensation of Season B- Eliminators Using New RAYTHEON Tubes with

We cut, drill and engrave for you Operating a radio set is now a Radio Panels of genuine Bakelite. source of keen delight to every mem- Send rough sketch for estimate. ber of the family. Consistent A properly drilled and engraved per- panel ready for formance every night is mounting is half assured with the job of construction. Plain pan- the new B- Eliminators using the els shipped C. O. D. same day order remarkable new Tubes and Dongan is received. Write for New Catalog Transformers and Chokes. And any on Radio Panels,Tubes and Rods - one can build this B- Eliminator at all of genuine Bakelite. small cost. Indorsed by leading radio engineers and well - STARRETT MFG. CO. known magazine editors, every radio lover can 522 S. GREEN ST., CHICAGO now possess the simplicity and 100 per cent. reception possible with the new Raytheon "Tube B- Eliminators. CARTER Type New "IMP" Rheostat No. Transformers 509 Full wave For RAYTHEON All Resistances 537 Tubes Full wave For R.C.A. U X 213 Tubes 537 Full wave For Cunningham C 538 X 313 Tubes Half wave For R.C.A. U X 216 -B Tubes 538 Half wave For Cunningham C X 316-B Tubes List $7.00 Chokes Type No. 514 20 henry 506 30 henry 539 50 henry (Pat. Pend.) List $5.00 $1.00. Half Size. (Complete Full instructions and description mailed on request- with Knob) Ask your dealer or send check or money order to factory. Sold under guarantee. Smallest rheostat made, yet most For Set Manufacturers efficient. A Carter designed con- Dongan tact arm that assures is the standard maker of transformers and positive, even chokes for the leading manufacturers of B- Eliminators. contact. No jerking or noises. Engineering data and quotations furnished on request. One hole mounting. Potentio- More than 42 of the country's leading sets use Audio Transformer's. Dongan meter same size. Any type you require. Your re- quirements can be handled promptly in our big plant. c sc Prices on request Any dealer can supply DONGAN ELECTRIC MANUFACTURING CO. In Canada -Carter Radio Co., Limited, Toronto 2983 -3001 Franklin St. Detroit, Mich. TRANSFORMERS of MERIT for FIFTEEN V EARS

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 1: What I would do if I wanted more money-By J. Matheson Bell After all he is the one who is going of .11 I'd make up my mind Vacuum Sweeper 1ST to operate it, so why wouldn't it be 'finitely that I was gtdng to Not so much in- better and best if all he had to do was t. terest to the man not much and I don't see just aril himself. I'll admit I'm h't believe any man living can get I find a radio that withod,t firmly how I'd show up d salesman, so if p worth while dust st night. will sell itself illcs,ns that then I'll not only he can. Deter - Radio - minatlon will whi competition conquer failure Why. the Sam Hill but l'Ildoiteasily. anytime, any- didn't I think of Best of all, I'll where. that before. but make that extra let's see if it will do money I want. I'll work harder --let's see what its on my present -\ -- i good points are at Who knows, I job the so suc- to make How C.. t Male Mere/ will as its bad ones. may be bawled that he cessful at it that owes me more. Tole -i don't know anything about I can give up my radio, but I have lots of friends who won't stop present job and But I have learned something about it. so give all mytirne t here. good to it a sw.d. ..I aaim I think I could. What sounds Gets An Idea- -Gee that sounds my *pare time to work. me is, that I can demonstrate in the be but other men iput in the evening. the very time too good to true, borne done so why can't I can kiuit losing Inuney by making my of the day for me. and that s just have it -I tinge pay. when all the music is being broad- and I will. . nuldn't give up my present job casted. But what radio can I sell that will do I'd make more money by working I'll have competition. I expect what I want and yet sell at a er hours. it. l'll have to know just what reasonable price -I don't want one my demonstration will do that the so high that my people can't buy - And something that could be sold one. nine, either in my home or some otherfcllow'swont, but it must be a good an lets see what want r else's home. would make the Then when I do sell it. they will me to fix anything that goes wrong so It something would have to be a biggest appeal. how because it somebody must teach me to to out of the ordinary something I. sld have to he of special interest in Of course, they service radio-that's would be impress- can't afford to overlook. p - evening. ed with music from Where is such a radio? lilt would be the t roe of day when our nearby stations -h the man and his wife are at but I feel sure that Where is a manufacturer who will el* so I'd find something hat if I bring in grcrt teach me how to old be of interest to both of them. distances they will sell and how to be c I feel sure that more impressed. demonstrate - such an article Think, Heed¡ It will have to where I can learn would have to bring in music loud' enough so they this business, both he something can sit away hack in the room and selling and servic- for the home, enjoy it. It must have volume. ing radio - there must be someone. something they .They may be satisfied with music would both use from nearby stations, but they'll ask There is- Ozarka and enjoy. me for distance, so I must be able to Incorporated of So far an good get "by" our powerful nearby station. Chicago -the sign what w i l l The radio I want must be selective so longdistancc but station If of the that something I can tune out our nearby goose-they have j I desire. writei le Mr. RA be. a 64 -page book "The Ozarks/ sonic pros - Piano? I can picture myself in Plan" which they will send walks to Work Maras. pect's home with a radio that will do me if I tell them about my -/ 1 1 e, but come to think of it canot that, but I wonder if that is enough - out. will be there self and mention the name" tn play one myself so that's maybe my competitor IAA also -- -maybe he can do all those of my county. Where 1 tonuobile- things as well as I can. is my pen and some / learn paper 1 going Use .uu is better, guess I could where ant I? I'm a, but ',ribs ta me that everybody Then make more / Thishis now has orle. At an rate the auto I've got it -I'll tell you what my radio money and I'm ends good -let's sec if there is any- must do- -1 want one that my pros- going to start COU P On! ' ng better. pect can do all the tuning, so that Ae will get the thrill of bringing in the i g hl now by / J Matheson He B. wri ti ( or t'ret. OZARKA, ln4 enogr s ph -- music froth a distance clear and food 121 Austin Arenue C. good as t he auto. and with atone that will please. tills boong k. / Chicago, Illinois on't pound near so r tarn rrreatl interested in the FREE Rook, Ozarks Flan No. 1.teilingCK how I can establish myself in the radio business and / my present income. Increase AUKA /Nam P ono' ! /Adams at. C 1 :4 Austin Avenue C 11 Austin Avenue Soo Chicago, Illinois Chicago, Illinois /Came

-"111 app-trains adrerlised in this magazine has been lrsied and apprnl'ed by POPULAR RADIO LABORATORY

www.americanradiohistory.com 18 The Best in Radio Equipment Separates Those Crowded Stations No matter how crowded the low wave stations - perfect separation is easily effected with the Tune -rite dial's convenient motion; low wave stations as easy to tune in, as clear and as perfect in tone, as high wave stations. So scientifically thought out that it's really a revelation in tuning. Gives your present set every advantage of the straight line frequency receiver, but without the necessity and expense of rewiring. Gradually changing ratios from 24 to 1 at low wave lengths to 2 2/3 to 1 at high wave lengths does the trick. Instantly attached to any set. Convert your set to straight line frequency. Send for instructions. Price RADIALL COMPANY No $3.50 Drilling Dept. T. P. R. -1, 50 Franklin St., New York Tu E The Straight Line Frequency Dial Made by the makers of Amperite, the "Self- Adjusting" Rheostat ~ Tei% / "Super " -Control Meter

Same device winds both spider web or sol- enoid coils in different sizes. Coils easily removed in perfect shape. All metal brass and aluminum. Approved by Popular Radio. For sale only by FRANKLIN COIL WINDER 81 Irving Place New York City

For ins ant attachment to the Radiola Superheterodynes No. 25 and No. 28. A precision type moving coil volt- meter, with bronze rim, rubbed mahogany cloth- covered base, complete case and the with cord. The scale of meter is marked in red at 3 volts. With users the ex ct filament for clearest lreceptione longest life of the tubes. and Price $8.50 BURTON -ROGERS 26 Brighton CO. Ave. Boston, Mass. National Distributors

All apparatus advertised in this magazine has been totted and aptroved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 19

1 McLaughlin LC-26-Hammarlund-Roberts All Approved By the Fan ! Here are the circuits that the radio fans of the country have taken for their own. Each of them represents the best in simplicity, efficiency, and most of all- results.

multi -tube set fan 1 Mahogany Finished Cabinet $9.60 AMONTH ago L. M. FOR the 1 D.T.W. Loop 25.00 Cockaday gave the ex- the McLaughlin Receiver 8 True -Blue Tubes 3 50 ea. 28.00 perimenter the LC -26. The with its single control is Total $166.40 basis of this new single- control offered. It is one of the year's Blueprints for McLaughlin Receiver .. $1.00 set is the famous Four -Circuit favorites. THE thousands who have Tuner! This means much to followed experimentally the man who must have the McLaughlin the development of the Roberts utmost efficiency ' from the One -Control Receiver Circuit know the possibilities fewest number of tubes. of this set. Here it is in a kit 2 Precise No. 750 Syncrodensers 4.50 ea. $9.00 which is easy to build and con- .60 1 Precise No. 744 Connector LC -26 2.50 taining parts of a grade which Cockaday I Marco 4 in. Vernier Dial .. 1.80 I Hammarlund Midget Condenser. I General Radio Type 269 Vario-n- insure success. 2 Carter "Imp." Jacks with plugs eter with knob $5.30 50 ea. 1.00 Type for loop wires 1 General Radio Rheostat Shelf 11.00 2.25 Benjamin 8 -Gang Socket ... 2I4A, 7 Ohms Drilled Bakelite Panel 10 in. x Set 5.50 Hammarlund- Roberts 1 Precision Octoform Coil in 4.35 6.25 14 % in. x 6 1 Amsco Double Condenser No. 1814 Pr. Precise Aluminum Brackets 2.00 1 Special Foundation Unit (Drilled .00015 mfd .35 1 Micamold Condenser Weston Voltmeter 0 to 7 volts 8.00 and Engraved Panel and Sub - Condenser .00025 mfd .35 1 Micamold Weston Milliammeter 0 to 25 M.A. 8.00 Panel, Metal Brackets and Wire) $9.40 2 Daven Resisto-Couplers with 1 .35 2 Rauland Lyric Transformers 18.00 3.00 Benjamin Battery Switch. mfd. condensers N. Y. Coil Condenser .006 mfd .75 I Hanunarlund Midget Condenser 1.80 Amertran DeLuxe 1st Stage Trans- 1 Condensers 1.25 ea. 2.50 2 Hammarlund .0005 S. L. F. Con- 10.00 2 Dubilier mfd. former Dubilier No. 640G .00025 mfd .55 densers 10.00 10 Megs 1.85 1 Bradleyleak M to Grid -Leak .50 I Set Hammarlund- Roberts Coils 6.00 2.25 Daven 2 megohm 3 Bradleyunits M meg Coupler No. 260 1.85 2 Naald Super DeLuxe 4 in. Dials 1.50 .75 Precision Inducto I Bradleyunit % meg. Filtoformer 4.50 5 Naald DeLuxe Sockets 3.75 3.30 Precise No. 1900 3 Amperites IA No. 1700 Super- Multi- 1 Naald K3843 1.4 in. Dial .25 1.10 Precise 1 Amperite No. 112 20.00 Amperites IA 4.40 5.00 former 4 5 Benjamin Standard Sockets Gen. Radio Rheostat, Type 214 -A, 5 Prs. Union Phone Tip Jacks 1.25 Single Circuit Jack . .70 Carter 2 ohm, 2A amp 2.25 1 Carter 25 Ohm Imp. Rheostat 1.00 2 Jack Switches 2.00 2 Carter No. Potentiometer. Type 1 Carter Imp. Battery Switch .65 1.20 Gen. Radio 8 Eby Binding Posts 400 ohm 3.00 I Carter Single Circuit Jack, No. 101 .70 3.50 214 -A, 1 Fynur Vernier Dial...... Precise Audio -Freq. Transformer Dubilier Type 640G .00025 Con- Panel 7.50 1 Drilled and Engraved No. 480, 234-1 ratio 7.50 denser .50 or Walnut I Cabinet. Mahogany Audio -Freq. Transformer I Dubilier Type 640.002 Condenser. .45 14.50 Precise Finish 480, 5 -I ratio 7.50 I Type 640 .006 Condenser. .80 .50 No. Dubilier 1 Hardwood Baseboard Circuit Jack 1.00 1 .40 .20 Carter Double Durham Resistor 4 Small Brass Brackets Carter Single Circuit Jack .70 Brackets .15 2 Large Brass 18 in. Stranded Wire for Oscillator $60.85 I 2 Block x . 10 1 Antenna Connection Circuit Inches .15 mfd. .35 1 N. Y. Coil Condenser .00025 Hammarlund-Roberts Cabinet especially Block I x 9 1 Battery Connection Celatsite Wire 1.40 the Hammarlund-Roberts Re- 25 28 ft. designed for Inches.. Bus -bar, Screws and Luis .75 ceiver. Finished in mahogany. Artistically decorated -well -built. A pleasing addition $77.90 to the furniture in your home. Price $10. Blueprints for LC -26. $1.00 As Used! The exact parts for the RAYTHEON PLATE SUPPLY UNIT ... $41.10 Mail orders filled promptly RETAIL. Our service to Dealers and fans con- WHOLESALE A postcard will bring the list of sists not alone in shipping material. parts and full information on these It is our aim to have new material or any other circuits in which you first, to ship you promptly and, most o1$sO are interested. If you are an ex- of all, to send you the exact parts perimenter and find special appara- called for by you. Substitutions are Electrical SupplYGlnc tus hard to get, utilize our connec- costly -when the set won't work. tions with most of the radio manu- facturers in this country and abroad. 15 East 40th Street, New York City

by POPULAR RADIO LABORATORY AU apparatus advertised in this magazine has been tested and approved

www.americanradiohistory.com 20 The Best in Radio Equipment ?he KODEL On to Success MICROPHONE in RADIO! Loud Speaker

Two Models Mr. R. L. Duncan Director of the Radio Institute ßl5 of America 211:1)

loud speaker that has the THEwhole country talking. An ex- RADIO is a profession well worth act replica of the microphone used fol- in lowing. The work is interesting-fas - broadcasting. Tremendous vol- cinating. The pay is high. The demand ume - - rich clear tone - - Hand- for somely finished in Roman Gold. new men -skilled men -is strong. At any radio dealer. You can embark, right now, on a successful Irrite for descriptive literature career in radio. With a few months study THE KODEL RADIO CORP. under the expert instruction of the Radio 504 E. Pearl St. Cincinnati, O. Institute of America you can pass your Owners of Broadcasting Station W K R C U. S. Government Commercial or Amateur Radio License Examination and be ready for your first real radio job. Study in spare time 5tøu/%itø LOSS There's no need to give up your present Interference work. Study at home in spare time. If Eliminator you really want to make a success in radio, No Radio Set Complete Without It fill in and mail the coupon to the Radio In- Now you can select stations at will, cut stitute of America for information on the interference out finest and undesired stations -tune in theoretical and practical radio courses loud and clear. offered today. Wonderful results with any tube or crystal set using any kind of aerial except loop antenna. Partially ab- RADIO INSTITUTE sorbs static. OF AMERICA Formerly Marconi Institute Amazing Results, Established in 1909 Better Reception Guaranteed 322 -A Broadway New York City or We Refund Your Dol- lar. Send Radio Institute Order of America Today. 322 -A Broadway, New York City ci Please send me full information about your Hom.ome Study Course of radio instruction. Select Stations At Will I am interested in the complete course, ing code includ- Try this Interference Eliminator on your set -no tools instruction, which qualifies for theU S. -nothing to add Gov't. Commercial or Amateur -attached in `2 minutes to aerial. Radio License Doesn't disturb present log. Directions easy to fol- Name low. Two big hanks testify to our reliability. Order today -dollar bill will do -we take the risk -money Address back if you say so. STEINITE LABORATORIES 301 Radio Building, ATCHISON, KANSAS Write for complete Steinite Radio literature -it's FREE. Most beautiful and least expensive radio sets in America.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment Balkite Radio Power Units the ideal power supplyforanyradioset

Balkite Radio Power Units are the ideal CIaLUIT power supply for any radio set. They sim- plify and improve radio reception. They U.e. Patent reduce the amount of attention you must U.S. Stay 2T . Patent 1.124 May 27, give your set. With their use your current 1924 supply is always exactly what is required for each circuit. The popular Balkite Battery Charger is entirely noiseless and can be used while the set is in operation. Balkite VB" The Balkite Trickle Charger converts Eliminates "B" batteries. Balkite Supplies plate current your "A" battery into a permanent "A" from the light socket. Op- Battery Charger erates with either storage Entirely noiseless. Can be power unit that supplies full "A" current battery or dry cell tubes. usedwhile the set is in op- at all times from the light socket. Keeps "B" circuit always eration. Charging rate operating at maximum ef. 2.5 amperes. Operates Balkite "B" eliminates "B" batteries en- ficiency. Requires no at- from 110.120 AC 60 from the tention otherthan adding cycle current. Special tirely and supplies plate current water twice a year. model for 50 cycles. Also light socket.Balkite "B"for sets of 6 tubes or Designed for sets of 6 for 25-40 cycles with 1.5 tubes or less. Occupies ampere charging rate. less. Balkite"B"II for sets of 6 tubes or more. about same space as 45 Price $19.50 An ideal installation is a Trickle Char- volt dry B"battery.Op- West of Rockies, $20 erates from 110.120 AC In Canada, $27.50 ger and "A" battery, and Balkite `B." This 60 cycle current. Special enables you to operate your set entirely model for 50 cycles. Price $35 U.S. from the light socket. In Canada, $49.50 Patent m1924 `Noiseless -No bulbs -Permanent All Balkite Radio Power Units are entirely noiseless in operation. They have no mov- ing parts, no bulbs, and nothing to adjust, Balkite break or get out of order. Each is a perma- Trickle Charger nent piece of equipment with nothing to Can be connected to the wear out or replace. They require no other usual 6.volt battery and left on permanent (or attention than the infrequent addition of trickles charge. Automat- water. They require no changes or additions ically charges the "A" battery and supplies "A" to your set. Balkite 'IB" II current from the light Manufactured by socket. Same as the new Balkite With smaller batteries FANSTEEL PRODUCTS COMPANY, Inc. "B" but will fit any set can be used as an inter- North Chicago, Illinois including those of 8 mittent charger, or trickle tubes or more. Operates charger if a resistance is FAN TEFL from 110 -120 AC 60 cy- used. cle current. Special model Charging rate .4 to .5 for 50 cycles. amperes. Size 5% x 2s/s x Price $55 5 inches. Operates from In Canada, $75 110 -120 AC 60 cycle cur. rent. Special model for 50 alkite cycles. 'Price $10 The Gould Unipower is West of Rockies, $10.50 equipped with a special In Canada, $15 gdioowerUn its Balkite Radio Power Unit BALKITE BATTERY CHARGER BALKITE TRICKLE CHARGER BALKITE a8" BALKITE "B'U ALL BALRITE RADIO POWER UNITS ARE TESTED AND LISTED AS STANDARD BV THE UNDERWRITERS LABORATORIES

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

YOU wouldn't have an auto without a self starter. THEN why a radio set without a Multi -Plug?

'l'yl-e B\1 BUY BUILD EQUIP YOUR RADIO with a MULTI -PLUG Affording a plug and socket connection Typ: BP between the radio set and all outside connections, Jones Multi -Plug is as es- sential to the radio as a cord and socket to the electric iron. Type BM -For Set Building-$4.50. Type BP- Adaptable to any set $5.00. -

Jones HOWARD B. JONES, CHICAGO, ILL. MULT1IiPLUG 618 S. Canal Street THE STAND D S P CONNECTOR Premier B Battery Cabinet NOW! Build a Real Set!

Our Premier B Battery Cabinet is a beautiful piece of furniture. The B battery compartment will take any Ltild type B battery. The space of each B battery compart- ntent is d' wide. S high and 10' deep. For Genuine No. Panel Deep N"alnut 71S -10 7x1S 10' SIS .0 721 -10 7x21 10' 19.00 AERO COILS 721 -10 7x2'1 10' 72(i -10 7 x 36 10' 20.00 Build a 5 Tube T. R. F. Receiver using the new Aero- 72S -10 7x2S 10' 21.00 Dyne circuit and the new notched Aero Coils! 730 -10 7 x 30 10' You will have a receiver, which because of the lower high 22.00 iswinc F.O. B. Waukesha. Wis. eres ecutrighhtrthroouughasttrrong ference. locaÌ nter- The tops of these cabinets are figured walnut. the ends It Is the patented construction and 13 battery panels of Aero Coils-their 95 " are select %valant. all 5 ply veneer. air dielectric and their dopeless airsppaaced windings which The bases are built up of massive molding. Nickel make them capable of a degree of selecartty and of colonic platedplated piano hinges and lid holders. The material and and tone far exceeding the commercial standard. ln these cabinets will equal the best furniture For any set there is a kit of Aero Coils. Buy them at your obtainable. dealers. Full instructions are in every package. for the free aoo Booklet. Write WE MAKE 9 STYLES OF 1' 11IINETS FOR No. CT80 Circuit OF PANELS. Send 14 SIZES -3 Tuner S 8.00 for our 1925 -26 line of cabinets at. No. RFR110-R.F. Regenerative Kit $11.00 "Factory to User" prices. No. WT40 -Wave Trap LTnit $ 4.00 No. 0855 -- - )scillator . ti 5.50 No. A \45 -- Antennae Coupler.... t 4.50 Utility Cabinet Company AERO PRODUCTS, Inc. 217 No. Desplaines Phone 721 Waukesha, Wisconsin St. Chicago All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 23

IN every industry there is some one product that by sheer merit and out- standing quality and performance is accepted as the standard by which other products may be judged. In the Radio Industry it is the Mu- Rad Transcontinental Receiver. Only One Dial to Tune Write Dept. F. 5 for Literature MU-RAD RADIO CORPORATION

-Transcontinental Receiver

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment There's economy and GetThisBjr satisfaction in these Valley Radio units You will find both economy and satisfaction WeSterillelai00 in the use of the Valley B- Eliminator and .9\CE lY the Valley Battery Charger. Economy in the B- Eliminator because it rqz3-rg?G stops forever the expense of buying new B batteries. . . EDITION Economy in the charger because it recharges your own storage battery at home over- DEALERS, send for our night at one -tenth the cost of service sta- big live catalog. Contains tion charging. . . nationally advertised high And satisfaction in both because, by using quality sets, kits and parts. them, you need never miss a program on Use your letterhead. account of low or worn -out batteries. ._ _ : . I I I\h I

I'WsternRI - Com I.y WesternRàdjo 134.W.Lake St.Chìca$o,i l l

THE VALLEY B- ELIMINATOR operates from any ordi. nary light socket and provides a steady, noiseless '71111111 - , "111111111: flow of B current at a constant voltage all the time. ,a" !III i For receiving sets of from one to eight tubes. Costs less at the start than wet B batteries. Costs less in OILS*/ LO1LS the long run than - dry cells. Much more satisfactory than both.

111

111 ' lllllllllli /0/1f // SUPER -SOLENOID. EFFICIENT RADIO COILS Require A Specialized Organization for Economical Production THE VALLEY BATTERY CHARGER iS the only charger We make Coils only. Cur entire needed for all radio storage batteries. Its correct 6- resources are devoted to Radio Coils. ampere charging rate makes overnight charging a For that reason we are able to render possibility. Radio Set Manufacturers an un- Most radio dealers handle the Valley B- Eliminator equalled coil service. and Valley Charger. Any of them will glad Regardless of your own facilities you be to will undoubtedly find this service show you these units and explain their advantages. profitable to you. Ask us for esti- Radio Division mates and samples. VALLEY ELECTRIC CO. ST. Louis, u. S. A. Branches in Principal Cities i Valley Electric o 107W. Contort St. Boston.Mass. itf apparatus advertised in this magazine All has been tested and approved by POPULAR RADIO LABORATORY www.americanradiohistory.com The Best in Radio Equipment 25 Do You Want to Read the Truth Abort Nyariable Condensers?

Type 334 SLW Variable Condenser Type 247 -H SI,,W Geared Variable Condenser

The question of what type of condenser to use is still uncertain in the minds of many set builders. In order that the amateur may have reliable information to guide him in the selection of the proper condenser for his specific needs we have prepared a booklet which con- tains a complete discussion Of all types of variable con- Type 374 S.L. F. densers. This booklet does not go into deep technical Condenser Variable detail on the subject but it covers in a complete, yet com- prehensive manner everything pertaining to "low-loss" condensers, laboratory condensers, straight line wave- length vs. straight line frequency condensers-in fact nothing is omitted that is of vital concern to everyone who is interested in radio construction and operation. This booklet is not a prejudiced discussion of the merits of one particular type of condenser, because the General Radio Company manufactures many types of condensers, each designed to meet its own respective requirements. Type 248 Tandem Condenser If you want Gospel and not gossip on the subject of variable condensers write for our 20 page FREE illus- trated booklet, "The Truth About Variable Condensers." Address Dept. P. GENERAL RADIO 'COMPANY Type 368 Cambridge 39, Mass. Micro Condenser iQ " Behind the Panels of Better Built Sets"

RADIO LABORATORY All apparatus advertised in this magazine has been tested and approved by POPULAR

www.americanradiohistory.com Rl;lil l.11ii¡,url ul the New Trartsfòrmer

MODERN -SYMPHONY Covers the Entire Range of Musical Frequencies The new Modern -Symphony Transformer has been especially designed to repro- duce and amplify the range of sound frequencies of any great orchestra. It will bring to you with equal faithfulness the basso profundo or the high treble. The new Modern -Symphony Transformer will delight you. Besides, it is built by a manufacturer of Standard Equipment. MODERN ELECTRIC MANUFACTURING CO., Toledo, Ohio

TONE ANNOUNCING Full, sweet, mellow and natural, without A COMPLETE NEW LINE OF the slightest indication of distortion, is another achievement that is making the APEX SUPER FIVE the most popular of ADJUSTABLE CONSOLES, all receiving sets. VOLUME TABLES AND ENCLOSURES That supplies dance music or entertainment without any loss, is a feature for which the APEX Many new designs and Patent Pending SUPER FIVE is world famed. features. A standardized size. Panels DISTANCE Lends added enjoyment to radio with an inde- are adjustable to length, depth, width, scribable fascination of tuning -in faraway stations, location, tilted or upright. which is always possible with the APEX SUPER FIVE. All in one enclosure, with deep panel Ask your dealer for a demon - stration. Your eyes and your beveling, beautiful woodcraft decora- ears will tell you that APEX tive effects, built -in loops, inside an- stands at the high point of per- fection in both performance and tenna and other new features. appearance. Large production at factory -to -you $80 without accessories. prices. SUPER 5 Watch for them! (Next issue.) Wait for them! Better still, write for literature. e Factory and Sales Department i y Q Illllmíä'l: Detroit Woodcraft Corp. ! li ñliuldb, N,W.I1.Nllllllllllllixiliollf 1 The Original The Adjustable 2262 -4 Hendrie St. Detroit, Mich. APEX ELECTRIC MANUFACTURING CO. Makes any radio look like a A R- A -D -I -0 1410 W. 59th St. Dept. 102 CHICAGO

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 27

=1 ":)rn;r.,11nw., -m Mil II Product of over 30 years' &xperience

O hear an Amplion reproduction and supreme in comparison with clarity on all notes give elo- any or all other loud quent testimony to Graham's speakers is to appre- more than thirty years' experi- ciate at once why Amplions ence in sound reproduction. are the largest selling radio re- Bring out the full musical producers throughout the quality of your set with an world- favorites of music Amplion loud speaker or con- lovers in all lands. sole unit. The prices are $12 The actual originators and old- to $42.50. All Amplions are est makers of loud speakers, completely equipped with cord Alfred Graham 3 Co., Lon- and panel plugs. Write for the don, England, evolved The "Amplion Pedigree" and deal- Amplion. Its superbly life -like er's address. THE AMPLION CORPORATION OF AMERICA Executive Offices: Suite X, 280 Madison Ave., New York City Canadian Distributors: Burndept of Canada, Ltd., Toronto Alfred Graham & Co., London, England, Patentees; Associated Companies and Agents: Amplion, Amplion Corporation of Canada, Limited, Toronto; Compagnie Francaise Continentale Amplion, Brussels, Belgium; Amalgamated Wire- Paris, France; Compagnie Electric Company, Ltd., less (Australasia), Ltd., Sydney and Melbourne; British General Indian States and Eastern Agency, Bombay and Calcutta; Johannesburg and Branches; Mestre & Blatge, C C. J. Christie E. Hijo, Buenos Ayres; David Wallace & Co., Valparaiso; Rio de Janeiro; F. W. Hammond & Company, London and Tokio.

M.°-w1°ilUüIUIIIhIIUIIIUUIIII0I11IIIII11I111I0IIIII11U1II110 'IIIIIIIIIIIIIIIIUIIIIIIIIIIIIIIIIIIIIInIIIIIIIIIIIIIIIIIIIIIIUIIIDm1°" . ....,...,.:_..

_... .._ .. - . mpr nt.r- ir- ,.,.nlunnullllllllllllllllllllllllllllllllo-:i\' l' ''-:,.c:n''Ti ñIIIIIIIIIIIIIIIIIIIIIIIIIOImmlm l

tested and approved by POPULAR RADIO LABORATORY t All apparatus advertised in this magazine has been

www.americanradiohistory.com 28 The Best in Radio Equipment barges AorB Batteries 3 Times qs Fast

%// 4 4 4 4...... 40 4..0...... ,. , ,,, ...... STANDARD CLCARTIROO IfI TYPES ...... ,,,,,,.,..

GUARANTEED 2 50 5, j RADIO TUBES = Being unequalled for their long life and an easy drain on batteries, Cleartrons are the most economical tubes you can buy. Use them for better tone and more volume. Perfect service or instant re- = placement guaranteed. At all Reliable Dealers Write for Free six page tube folder C -T 101A. A Hi -Mu Tube. Price 83.00. E CLEARTRON VACUUM TUBE CO. 28 West 44th St. New York City Factories: ?he New 5 Ampere West New York, N. J. l irmingham, Eng. FOR. BETTER. RECEPTION HDMCHARGER Illlllllll111111fafa111Nfaefafa1111fa1111!l111111 NOW you don't have ro wait for days while your ANOTHER RADIO TRIUMPH batteries charge. The new 5- ampere GOLD SEAL HOM- CHARGER charges A or B batteries three times as fast as old -fashioned 2- ampere chargers - - It fully charges °Q°`UD a the average radio battery OVERNIGHT! AUDIO COUPLER For Improved Resistance There are no bulbs to break, no acids to Attains Maximum spill, no extras to buy - - - It is trouble - Results' proof, shock -proof, fire -proof. Any radio Pur -A -Tone Audio Coup- dealer can show you the new 5- ampere ling supersedes trans- GOLD SEAL HOMCHARGER. former coupling. Fewer parts required. Con- struction simplified. Write for FREE booklet "The Secret of Distance More compact. and Volume in Radio" - Pur -A -Tone l6 pages of helpful radio is standard- information. ized, interchangeable for all stagesand withstands high voltages. Manufactured Only By The Kodel Radio Corporation BRACH-STAT Automatic Owners Filament of Broadcasting Station W K RC Controls eliminate the need of hand 504 EAST PEARL ST. CINCINNATI, O. rheostats on all amplified circuits. Give : longer life Also manufacturers of KODEL RADIO to your radio tubes. the KODEL MÌCROPHONE SPEAKER. L. S. BRACH MFG. CO. Newark, N. J.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY I

www.americanradiohistory.com The Best in Radio Equipment 29

Be a RADIO T EXPERT

Train At Home For A Big -Pay

RADIO JOB Given Radio today is ureei.tly in need of trained men -Radio Instruments Experts. Astonishing opportunities- thousands of them With Course -have been opened up by enormous strides of the Radio Receiving sets, from simplest industry. That's why it's easy to make big money in kind to thousand mile receiver is teem- included without extra charge Radio -$50 to $250 a week. Here's a field that course. Other ap- with opportunities and room for expansion -a in your ing Industry if paratus given to help you brand -new. wide awake. and uncrowded learn. An UNEQUAL - you're earning a penny lffos than $50 a week Ell OFFER. Many other clip coupon now for Free Book and proof. big features for limited Your Satisfaction Famous Course time only. Guaranteed That "Pays Get This Book Master Radio Enid- for itself' nears will elbow how to "Rich Rewards in Radio" - qualify quickly and Ras Spare time earnings most amazing b.okconcern- fly at home for Radio's are easiest in Radio - ing Radio ever written, one lobs. We - receiving sets every - will be sent to you prompt- tea to train you suet where nowadays. In ly when you send the cessfully. You don't every neighborhood coupon. ACT NOW. Isk a penny, for we there are scores of jobs will gladly return every you can turn your hand cent paid in tuition if to in an hour or so after upon completion of supper. Right at the course you aren't abso- start of your course we lately satisfied. Back of give you practical this guarantee stands money -making lessons all the resources of which teach you how to National Radio Insti- do this work, then how Lute, U.S Government to get it -so by our recognized and the old- practical plan you can Government Spending Radio make your course pay est and largest while Millions on Radio home-study school iu you're U. S. Government now emends tthe worl studying. flhons develo Ing. using Radio. Lack of x- Postmaster eneral Hays Raid: Age or Get All the Facts Probably the latest part in the Experience No future of the postal service will he Drawback At Once played by Radio. Photo aboye- need ex- Astonishing facts on sending out time signals at Arling- You don't marvelous new in- station perience before taking the ton great Government Radio this course, and corn- dustry of golden re- at We ehington -Radio Is fitting new is wards- Radio -the fast - You Can Do uIes filling new needs never dream - mon schooling est- moving, live -wire Experts are In enough. Our tested, 7 71 What Cthera ed of before. Radio Free k Have Done greater demand than ever. learning clear and all the before yyou Send Coupon Now easy -the most natural obligation. Send Radio Why go along at $15 thing on earth. No o or $25 or $36 a week. Get o" of the low -pay rut, get fascinating, easiest when then oughly- train- into the most earth. RADIO INSTITUTE Needs ed Radio Experts earn big -pay profession on NATIONAL a hundred or more in Free Book how. Dept. AT8 Washington, D. C the same six days? ND FOR TODAY Trained What this train- ing has done for hundreds of Men others, it can do BIG for you. Send N.R.I.TRAINED MEN ARE SUCCEEDING coupon at once. "Your "My charges o course to for consulta- completely tion now 12.50 cover o per hour. The Radio it Is course is MAIL TH IS COUPON. worth $40a worth to me week more at least $60 Radio Institute, 000." R. Ni. National to anyone in Black hill. Dept. AT8, Washington, D.C. the electri- N.Y. cal line B'klyn, tinco graduation have me in any way, send averaged $6,0 to $80 Without obligating week more. Preston your Free Book, ' Rich Rewards in Radio' - Operates WMAQ Gets Big Job Fowler, Gordon, Neb. also full information on your practical. home- 'A rerr tad s position with "Just been made Sales study Radio course. Manager of this Radio Chlcago Nally News-sta- In tion VIMAQ. My Income concern-a big raise worth $2600 a yeti tctically doubled, Day. Regret I did not "Your course Name thr anks to our fine take course sooner." R. mine dl myrs Jones. Bay Clty, rest, Rdio to old I Course.'' Keith Kimball. E. A. R. Herkc, Winnipeg. Canada hlcago, Ill. Mich. .lddress LARGEST RADIO SCHOOL'' Town State TRAINING ORIGINATORS Of RADIO HOME-.STUDY

and approved by POPULAR RADIO LABORATORY All apparatus advertised tw this magazine lias been tested l www.americanradiohistory.com The Best in Radio Equipment SICKLES DIAMOND -WEAVE COILS (Trade Mark registered Aug. 4, 1925) For Browning -Drake, Roberts, Craig, and Hoyt Circuits (Patented Aug. 21, 1923) Sickles Coil Set No. 24 for Browning -Drake Circuit. Price $7.50. Compactness of form, rigidity of construction, and the supremely efficient Diamond -Weave method of winding are well -known character- istics of Sickles Coils. These refinements of design and construction COIL PRICES result in low distributed capacity, low dielectric losses and large range of frequency with small No. 18A Roberts Circuit $ 8.00 set variable capacity. No. 24 Browning-Drake 7.50 set There are Sickles Diamond -Weave Coils for all leading circuits. No. 20 Craig Circuit 4.50 set Send for descriptive catalog No. 19 Acme Reflex 4.50 set No. 8 Knockout Reflex 4.00 set The F. W. Sickles Co. No. 21 Hoyt Circuit 10.00 set 134 Union Street SPRINGFIELD, MASS.

World's TREGOTheLowest Priced FREE 5-Tube Tuned Radio Frequency Set Radio Stamps 168 beautiful copper etched American, Canadian, and European stamps '(8 different colors), each with the call letters of a station, FREE with Ideal 48 -page Radio Stamp Album and Log. As you hear new stations, just put proper stamps in your album. Coast to Coast Range An interesting game -a fas- cinating hobby. Makes your HERE'S the set that radio a real pleasure. Album sells and satisfies! and stamps become a perma- nent and interesting record of It's the TREGO stations you receive. You 5 -Tube Tuned Radio and your children will enjoy Frequency lt. You will be proud to Set -high- show this to your friends. est quality at a price Also contains complete list of within the stations both alphabetically reach of all. and by call letters. Hundreds Retails at only $45.00. Gives you Big Profits. of hours of pleasure for a few Sells lO to 1 over higher priced sets. Millions want cents. Worth many times it! Storage or dry -cell operation. Backed by our small cost. Complete album. Iron -Clad Guarantee. Sold only 8 "x11 ", heavy board, two through dealers. colored covers, $1 plus pos- Send for Monthly Catalog and exclusive tage. dealer plan. This TREGO TRF5 is only one of the hundreds of profitable quick -selling items listed -just off the press. Get your copy now - Send No Money cash in on the fall and winter radio demand. Just pay postman after album TREGO prepay and FREE stamps arrive. We RADIO MFG. COMPANY postage if you prefer to pay with order. MONEY RE- Manufacturers FUNDED if not DELIGHTED. Enjoy this album. and Wholesale Distributors order today -NOW. Postal will do. Send 1431 Chestnut St., Kansas City, IDEAL CO., Dept. 6931, 366 Wrigley Bldg., Chicago Mo. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 72,1 RADIO 'KITH M ETI C QUESTION: What's the Difference Between Good and Poor Radio Reception? ANSWER: A RECTIGON!

NO storage- battery radio is complete without a RECTIGON.

rO recharge one or two -cell radio "A' batteries with a Rectigon, onerely adjust "snap" terminals as 'blown above Takes but a moment

110 recharge three or six -cell radio jj "A" or automobile batteries merely '.trdjust "snap" terminals as shown above Westinghouse manufac- © 1926, rtery simple. tures, also, a complete line W. E. & . Co. of Miearta radio panels, Micarta tubes and instru- ments.

THE Rectigon offers a real solution to the oft -repeated eleven to forty -eight -T O recharge Ask any 1 cell "B" batteries merely adjust question, "What's the matter with my set ?" 'snap" terminals as shown here. (An owner of a Westinghouse Rectigon. There are radio fans by sheet packed with every Instruction way to keep Rectigon.) the thousands to tell you there's no better, surer your batteries full of pep than with a Rectigon. HERE'S no muss or fuss with a Rectigon. No acids, no chemicals, WESTINGHOUSE ELECTRIC & MANUFACTURING CO. t oo moving parts and no noise. SOUTH BEND, INDIANA e i estinghouse Rectigon Battery Charger

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 32 Tite Best in Radio Equipment

A GUARANTEE OF GOOD RADIO Thousands of Arborphone owners know they are certain of excellent reception to -night and every night. For Arborphone Receivers are built upon thoroughly proved prin- ciples-of the newest, improved parts and materials. Keeping dad's 55oo Tuning is highly selective and simple. Distance -you can satisfy all reasonable demands. Cabinet work is in excellent taste. radio going From any standpoint you wili be proud of your Arborphone, appearance and per- formance. Ask your dealer to demonstrate Many a son is the family radio expert, but few have as or write to factory for beautiful catalog. fine an opportunity to keep posted as the man who $60.00 in Rocky Mt. and Pacific Coast States wrote the letter printed MACHINE SPECIALTY CO. below. He is a radio mechanic Ann Arbor Michigan with one of the biggest electrical supply firms inWash- ington, D. C. -and just about everything new in radio parts comes to him for a practical test. ARBORPHONE He writes us: ,: 1 P', "My father lives in the mountains of Pennsyl- ,.,'. ,. vania and, of course, has a radio receiver to ;i;' keep in touch with the business world. "For some time he has had trouble tuning in stations, so when I went up to make him a visit I took along one of your .00025 mfd. Sangamo fixed condensers with grid leak terminals. "I tested the set and found that the grid con- denser had changed its capacity, due to damp- ness, as it had been kept near an open window. I installed the .00025 mfd. Sangamo fixed con- 1 denser and the set changed completely; tuning 12 -Cell - 24 Volt Storage 'B' Battery became easier, and quality of reception was Positive) gives free with each purchase of a WORLD A' Storage Battery. improved 100 per cent." You must send this ad. with your order. WORLD Batteries are famous for their guaranteed quality and service. Backed by years of successful manufacture "Yours very truly, thousands of satisfied and with users. Equipped Solid Rubber Case, an insuran e against acid and leakage. You save (Signed) E. L. Maschmeyer" per cent and get a 60 2 -Year Guarantee Bond in Writing WORLD Battery friends." owners "tell their That's our best proof of per- formance. Send your order in today. JSANGAMO SANGAMO Solid Rubber Case Radio Batteries 6 -Volt, 100 -Amperes . $1 By -Pass Condensers now available. 6 -Volt. 120 -Amperes .. 1.25 Accurate 6-Volt, . . . . 13.25 1 mfd. $1.25 140- Amperes . Radio Parts 14.00 1/2 mfd. .90 SoUd Rubber Case Auto Batteries 6 -Volt. 11 -Plate . $11.25 Approved and Listed 6 -Volt, 13 -Plato 13.25 as Standard by Leading 12 -Volt, 7-elate . . Authorities . . 16.00 includingRadioNewsLab- SEND NO MONEY Just state battery wanted and oratories Popular Sci- we will ship day order is re- ence ceived. by Express C. O. D. aub 'et Institute of Stand- amination on arrival. to your ex- ards, Popular Radio Lab- Sangamo cluded. FREE: B" Battery in- oratories, Radio Broad- Electric Company Extra Offer: 5 cash in full per cent discount for cast Laboratories. Radio t42t-5 with order. Buy now and get a in Springfield, Illinois guaranteed battery at 60 per cent the Home. and Lefax, RADIO DIVISION, 50 Church Street, WORLD BATTERY COMPANY New York 1219 So. Wabash Ave., Dept. 3 CHICAGO, ILL. SALES OFFICES -PRINCIPAL CITIES Fr For Canada- Sangamo Electric Co. d of Canada, Ltd.. l AUoTO Toronto. For Europe- British Sangamo Co., Ponders End, Middlesex, Eng. ® and For Far East- Ashida Engineering CchsbOsaka, Japan STORAGE BATTERIES RAD IO

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment

Make Your Radio Gift A Gift of Practical Service

Other STERLING "Gifts of Service" Home Tube Testers for small tubes $10.00 for large tubes 8.50 Battery Chargers $16.00 to $25.00 Pocket and Panel Meters $1.00 to $6.00

What could be more appropriate than the gift which insures renewed and continuous vitality to radio tubes- for without good tubes the best broadcasting is poorly received. What gift could be more practical than a tube reactivator which shows when to renew tube life and shows how good each and every tube is after treatment. Make your radio Christmas gift a Sterling metered tube reactivator a gift that friends and family will appreciate most -because it prolongs the joy of radio throughout the year. Ask your dealer for the tube reactivator that renews your tubes and tests them too-that's the Price : $12.50 (50 -60 cycle) $14.00 (25 -40 cycle) TUBE REACTIVATOR Mention cycle THE STERLING MFG. COMPANY when ordering 2831 -53 Prospect Ave., Dept. G., Cleveland, OhiJ (World's largest manufacturer of small meters)

All apparatus advertised in this magazine has been tested and approved bÿ POPULAR RADIO LABORAIORI

www.americanradiohistory.com 34 The Best in Radio Equipment

INDUSTRIAL. RESEARCH EN NEERS

"RESEARCH IS THE KEY TO THE FUTURE OF RADIO" says R. E. Renaud in "Popular Radio" Radio manufacturers, radio investors and the buying public are be- ginning to realize the tremendous importance of research work based on science and method. Large manufacturers maintaining research departments of their own find our services of great value for the solution of problems which arise from time to time outside the more specialized field of their own research departments. Smaller manufacturers may now have their necessary research work done without the financial burden of maintaining research departments of their own. A descriptive booklet will be furnished on request. KALMUS. COMSTOCKvWESCOTT Inc. Industrial Research CHAMBER OF COMMERCE BLOC. Engineers. BOSTON. MASSACHUSETTS

lll auuununuuuui 1. W

ELKAY 5 -TUBE SUPER -SELECTOR Compares favorably in appearance, selectivity, volume, distance and tone quality with sets at twice its price. Has one stage R. F., detec- tor, one stage of transformer 80 coupled amplification and two resistance coupled amplifiers. Only two dials. A radio frequency choke permits same smooth operation on low or high wave lengths. Control over selectivity a distinct departure- an ELKAY invention. Also made with 4 tui.es at $70. Blue prints, $1.00. See the ELKAY at your dealer's. (Dealers, write for exclusive agency.) THE LANGBEIN- KAUFMAN RADIO CO. 511 h i¢inamrs and-Nald'..- LtircrérUunu:-;::>: Chapel St., Dept. P., New Haven, Conn. ruuera J. u( Self Fy,.,,;ug S"1(11::. An LK Product uE51LE1ì lAV SUPPLY )ll `Imsposmoostrono ÍÍÍÍüï,: üÌüürÌü:':: TUNERS I ELIKAY SETS, KITS

All apparatus advertised in this magazine has been tested and afiroved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 35

\\

Al - 1 .460 (...;v 4$l it r str \

Made under IToean Patent No. 1,014.1)02 Jan. 9. 1912 Reduces Interference The most vexing problem you have to face with your radio set is INTERFERENCE. U. S. Tool Engineers have perfected a Straight Line Frequency Condenser that distributes the stations uniformly over your dial and makes possible a degree of selectivity you never thought possible. No more crowding--minimum inter- ference when you use U. S. Tool Straight Line Frequency Con- densers. 1 Write for Booklet U. S. TOOL COMPANY '// INC.

AMPERE, N. J. - I/

0 . \,0,_____) 4.4

tr

All apparatus advertised in this magazine lias been tested and approved by POPULAR RADIO LABORATOR1

www.americanradiohistory.com The Best in Radio Equipment

11,tng ín tlje betu dear! Listen to the clear tinkling bells on the Heath frost..' midnight air -at the .stroke of 12. WHY NOT USE THE Straight Line "B" RECTIFIER ?

Rhamsline* <

.4;1 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 37

KURZ -KASCH Aristocrat E--TO ON Group Control

For the set you have For the set you build

Kit containing complete parts, nothing End complicated tuning by else to buy. Simple to install. You can equipping your set with an change over your present set in half an hour. Aristocrat E -Z-TOON Group Control. One Master Vernier dial (or vernier pointer Knob) controls all tuning units, at the same time providing Vernier adjustment for each separate tuning unit. Rotating the master dial lo- Group Control comes either with Center cates the station, and by tuning Master Control Dial or for sets with gradu- ation on panel, a Master control pointer the correcting vernier on each Knob is provided. unit, perfect tuning can be ob- tained. Simple to install, no extra parts to buy. No panel to drill. Can be installed in half an hour. Complete with instructions, Ask your dealer. Write Rear View $7.50. us for illustrated folder.

by THE KURZManufactured KASCH C OMPANY Exclusive Moulders of Bakelite Largest Dayton, Ohio. Factory & Main Office

and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine has been tested

www.americanradiohistory.com The Best in Radio Equipment TOBE "A BETTER CONDENSER" The Perfect Filter Condenser for "B" Eliminators Tobe condensers were specified in "How to Build" articles on B battery supply units in the November issues of Radio News, Popular Radio, Radio Broadcast and Radio. FIRST -Because of their uniformity .less than S' t variation from rated capa- cities. SECOND -Because of their permanence their rigid construction assures per- manence of rated capacities taroug.i variatio. of temperature). THIRD -Because of their high megohm resistance (indicating extreme low CONNECT BATTERY= loss and higa insulation). TO CONDENSER FOURTH -Because of their capacity to withstand overload (can operate at voltages up to 700 D.C. without breakdown). TOBE CONDENSERS are made in sizes from .00025 Mfd. to 4.0 Mfd. Compare Tobe Condensers I I IIIIII with e others by this simple ------h`a. test - Charge your condenser from your battery, then remove the connections from the condenser and wait fifteen minutes. Then discharge the condenser by shunting a wire from one terminal to the other. If a spark appears it is proof that the condenser is capable of holding its charge for quarter of an hour. DISCONNECT AN WAIT IS MINUTES. Any condenser which fails in this test is not suitable for by -pass or filter work. Insist on Tobe condensers for by -pass B battery or B eliminator use. They are distinguishable by their silvered -aluminum cases and their easily identified cartons of new a.T i distinctive design. Tobe Deutschmann Co. CORNHILL BOSTON, MASS.

Technical Booklets Worth Reading FOR CLEAR, QUIET tB" POWER Cardwell Quality Radio Parts are stand- ard. Write for Bulletins on any or all of the following. They give a liberal education on radio theory and practice: 51 Variable Condensers 52 Special Condenser Types RADIO 85 Straight -Line Condensers Storage "B" Battery 55 Cordweve Coils on press) 12 Cell 56 Transmitting Condensers 2avol te Las LS Indefinitely-Pays for Itself Economy and performance unheard of before. Recharged at a negli- gible cost. Delivers unfailing power that la clear. pure and quiet. 71 Equitrol Dials Approved and listed as Standard by leading Radio Authorities includ- ing Po . Radio Laboratories. Pop. Sci. Inst. Standards Radio News 36 Engineering Service 4b efax, Inc., and other Important institutions. _Iquipped with Solid tabor Cep. n insurance against acid and leakage. Extra 37 Audio Transformers heavy Criss. ;are. heavy rugged plates. Order yours today) SEND NO MONEY site n®ber of batteries is received. '°'twanted and we will able day order 82 Professional Set Builders Plan Extra offer: 4 batteries in series (96e 110.00, pay exp easman after examining batteries. 6 per cent 60 Dealer Electrotypes with order. Mall your order nowt discount for cash WORLD BATTERY COM 72 1219 So. Wabash A,sNy Exclusive Dealer Agencies Mature Ave., Dept. 77 l,hicago, IIL of tAa Famous World Radio "A" Storage Battery /irises: 6 -pout. RAO Amp. tit 25; 1spAmp$ 11.25; AU equipped iai-h 1{OAn $044". PLEASE! Be sure to check ONLY Solid At I, WV (as. bulletins in which you are interested. Set your Radio Dials at 210 meter. for the new 1000 watt World Storage Battery Won l ra000 Chicago.cements. ALLEN D. CARDWELL STORAGE BATTERIESSuuio Watch [Or SBC. Manufacturing Corporation El MWcAr-'i W5N'W.1StKtt1nv0s}0W 81 Prospect St. - - Brooklyn, N. Y.

All apparatus advertised in this magazine Izas been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com i The Best in Radio Equipment 39

RIETONE, REG U 5 PAT. OFF.

List $20.00 List $30.00

Pronounced by experts to be the most wonderful toned Radio Speaker they have ever heard. An improved four pole unit with non - metallic diaphragm results in the hearer wanting to own one. It is a real musical instrument.

Duco Mahogany finish -all wood .

For Sale By SANFORD BROTHERS Chicago, Ill. Seattle, Wash. Chattanooga, Tenn. San Francisco, Cal. 30 W. Walton Place Am. Bank Bldg. 615 Broad St. 311 Minna St.

FACTORY: TIMBRETONE MFG. CO. Hoosick Falls, N. Y.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 40 77.e Lesi in Radio Equipment

Clarity

Radien Panels in black Volume and Mahoganite come cut in all standard sises. Beauty The double advantage of RADION THERE are two important requirements PRICES for any set: Three Finishes (1) Efficient reception and (2) Good appearance $22.50 $25.00 The selection of RADION goes far toa and ful- filling both these requirements. RADION $30.00 Panels possess sure - rior insulating qual- FOR REAL ENJOYMENT ities not excelled in Use the BURNS Loud Speaker on your receiving set. any other panel Produces utmost in volume and clarity of tone. made. RADION Reaches full range of musical scale -equal to hearing has such a beau -t the original production. tiful surface finish At your dealers or direct that it noticeably merlam ( enhances the ap- ¢kdi awleyq pearance of any set. New No.l0 4-inch Radian Dial, State and 64th Streets, Chicago This double built to conform to the fingers, advantage of helping you to get close tuning. RADION is due to the fact that it is the only insulation that was made to order for radio purposes exclusively. The high- resistant characteristics possessed by RADION Panels mark all RADION low - loss parts- Sockets, Dials, Insulators, Tubing, etc. Adopted by leading manufacturers and sold universally by radio dealers. Send for booklet, "Building Your Own Set." Mailed for 10 cents. Manufacturers -Our facilities and equip- ment for the manufac- ture of molded parts are second to none. Write us for prices on quantities. No. 2 Radion Socket for new UX tubes with collar AMERICAN HARD adapter, for old type tubes. RUBBER COMPANY No. I same as No. 2, with- out collar adapter, for (Dept. B 13) 11 Mercer St. new UX tubes exclusively. New York City

. ANJ) THE AD I ON 4RAGAIN RfiDIO DECEIVER Ike Sitprerne Insulation fIUTOMET'AL CORPORATION Made to Order for Radio Purposes Exclusively NIAGARA FALLS ill apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 41

Rau Am..A C TRACE MARK AUDIO FREQUENCY TRANSFORMER TYPE R -500 SERIAL N9 ALL-AMERICAN RADIO CORP. CHICAGO, U.S. A.

When a Finer Transformer Is Made It Will Bear This Name -Plate

Radio moves rapidly. Perhaps some time there may be seen a better transformer than what we now know as Rauland- Lyric. It may sell at $9, or $10, or $15, or $7. But the careful observer of the past year's developments will entertain not a moment's doubt of one thing: when the better transformer comes it will come beneath the famous Rauland -Lyric name -plate. Behind this as a pledge rests the entire organization and resources of the All -American Radio Corporation

Rauland -Lyra is easily obtain- Rauland -Lyric tone quality is able from better -class dealers now available in a complete everywhere. The price is nine receiver: the new All -American dollars. Descriptive circular Model R (a five -tube tuned- with technical data maybe had radio-frequency set) now being on request to All- American shown. If your preferred dealer Radio Corporation, 4201 does not display it. send to us Belmont Avenue, Chicago for descriptive booklet

L

RADIO All apparatus advertised in this magazine has been tested and approved by POPULAR LABORATORY

www.americanradiohistory.com 4? The Best in Radio Equipment How to Get the Most LOMBARDI Out of Your Set Straight Line Frequency Condensers

Are real precision instruments, fit for the highest grade of Radio Sets. Their substantial and careful design is immediately apparent to anyone who knows Radio. Patented ball and Learn taper- bearing shaft and watch spring pig tail the principles of radio from insure permanent accuracy. Made in both this remarkable book single and multiple units. Multiple units 514 PAGES licensed under Hogan patents. Compiled by HARRY F. DART, E.E. Manufacturers and home set builders Formerly with the Western Electric Co., and write for full descriptive matter. U. S. Army Instructor of Radio Technically edited by F. H. DOANE LOMBARDI RADIO MFG. CO. 67 Minerva St., Derby, Conn. STOP turning the dials blindly. Learn what happens when you turn them and why. Then you will get greater S distance, greater volume, most enjoy- able quality. The I. C. S. Radio Handbook will help you to get more enjoyment out of radio. It clears up the mysterious - tells you lust what you want to know. Written by nationally I.nown radio authorities in language that you can understand. An absolute necessity for every radio fan. A wonderful bargain at $1. Note this partial last of contents - Electrical terms and circuits, antennas, batteries, generators and motors, elec- tron (vacuum CHELTE tubes), many receiving f ELEZRIC CO hook -ups, radio and audio frequency Q.. pHka, amplification, broadcast and commercial og. transmitters and receivers, super- regen- eration, licenses, etc. Send only $1 with the coupon today and get this 514 -page I. C. S. Radio Handbook. The Chelten Money Back if Not Satisfied Straight -Line Frequency Condenser (Modified) INTERNATIONAL CORRESPONDENCE SCHOOLS A real Condenser scientifically designed from Box 8250 -G, Scranton, Penna. practical operating standpoint. Dependable I enclose $1. Please send me- post -paid -the 514 - page I. C. S. Radio Handbook. It is understood that it in every way. Spreads low wave stations. I am not entirely satisfied I may return this book within Provides five days and you uniform separation over tuning will refund my money. range. Standard frame -soldered brass plates. Name Send for our booklet, "Straight-Line Frequency Tuning," Address an authoritative study on this vital subject. its free. Check here O and enclose $1.50 instead of $1 it you wish the De Luxe Leatheroid Edition. CHELTEN ELECTRIC CO. 4859-65 Stenton Ave., - Philadelphia

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 43

Distance with Volume THREE stages of perfectly matched audio enable you not only to hear, but to enjoy even the distant stations with loud speaker volume and absolute tone fidelity. l-ergu.on "Sig." -Tito tuning controls In the acid test of comparative perform- IA six tube Tuned R. F. Receiver) Cabinet Model.______.$180 ance, the Ferguson wins every time, be- Console Model .$290 cause it is fundamentally correct in design Ferguson "Eight " - One tuning con troc and precision -built in its super- crafts- (A six tube Tuned R. F. Receiver) manship. `Cabinet Model $226 Console Model $348 The graceful dignity of Ferguson cabinet )Above prit rs are less accessories) work is the crowning touch that has won a permanent place for the Fer- guson in so many of the better homes throughout the country. Go to your Authorized Ferguson Dealer -hear the Ferguson in comparison with others and you will learn why it has been popu- larly acclaimed :"The Gold Stand- 1 ard of Radio Receivers." -480 -490 I - 500 J. B. FERGUSON, INc. 41 East 42nd Street New York, N.Y.

One Tuníng'Cantrol- OCulibrated in Meters! Simply choose your program, usort turn up its wavelength and in arses your station -right on INCORPOR.t1TED the line: 7/I( Gold Standard fJ¡RaCiC1 /erí.'ivCY

.411 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment .. "A.... 1 7beWilson' Í "rte An Inside Aerial 1,004 Feet Long!

Pate. Pend.

ANTENNAEarsee REG U.S TRADE MARK In Walnut Case PATENT PENDING Gives Longer Range -More This new unit will enable you to get Volume- Vreater Selectivity the most out of your receiver .Provides uniform -Less Static! "B" voltage at minimum cost. Operates from The New EFFARSEE (Type IXL) light socket. Will not set up the slightest hum. gives you the equivalent of a thou- Hook it to your sand feet of copper wire. Increases set and forget it except to volume tremendously, minimizes switch it on and off. Nothing to adjust. static, makes any set more selective. Nothing to get out of order. No acid to spill. No expensive replacements. The most Equipped with Fixed Con- dependable, convenient and economical plate densers Gives Greatly Im- current supply. Price complete $35. proved Reception! Write for complete information EFFARSEE is scientifically de- signed to give local and distance ?heAndrews reception at its very best. Can be used inside or out -covered kith Paddiewheelfeil parchment, it rolls up-can be Type IXL Pate. Pend. This coil can be used in hung on walls, in closets, hidden (Large)....$4.00 any hookup tinder rugs. Has coast to coast re- Type BXL requiring a ception records. Write for book- (Small). , . . high grade inductance. let of $2.50 testimonials and distance re- At any radio dealer You will be pleased with ports. ,or write direct. results because of its negligible losses, mini- THE FISHWICK RADIO CO. mum distributed capa- 137 Central Parkway Cincinnati, O. city and exceptionally Price $3.00 high ratio of inductance to resistance. It greatly improves tone quality, making pos- sible any desired volume without distortion. Used in_ such well -known receivers as the i0 Dealers Deresnadyne and Buckingham. Ask your dealer 1"- forconstructional blueprints of tested circuits employing this superior coil. .ANTED,) If you Our Technical Dept. will are the type of dealer who hustles answer inquiries. after business, who isn't content to wait for trade to come in but who takes sets DRUO0SPEW out to demonstrate, can talk and sell quality merchandise, and knows Radio Wilding fop values, we have a big proposition for you. Handsomely finished Are you that dealer ? in silver and mahog- 50% DISCOUNT TO DEALERS anyto harmonize with We manufacture a complete line of high grade the finest home receivers and sell to dealers at 50% discount. We are authorized distributors for more than 225 Nationally furnishings. advertised lines. Write today for amazing offers new 112 -page catalog and regular monthly catalogs quoting below - the- market prices on latest mer- chandise -all free. Everything in Radio for less. Just fill in Pate. coupon, pin to your letter head Pend. and mail today, NOW. Folds neatly and compactly. Has graduated AMERICAN silvered RADIO MFG. CO. dial and insulated handle. Use a 1416 -18 McGee Street, Dept. P., Kansas City, Mo. Duo -Spiral for selectivity and to reduce \tele static. A special model for every circuit. s AMERICAN RADIO MFG. ('O., 1416 -18 McGee St., If your dealer cannot supply these Dept. P, Kansas City, Mo. standard products, write direct. Gentlemen: Mail me your new 112 -page catalog. Also put me on list for regular monthly mailings.

Maio Mate Lae. 1 Name 1301 First Avenue Maywood, Illinois Perkins Elect. Ltd., Montreal, Toronto, Winnipeg Address 1 City State x..,.,as.,...,....,...... ,-...,. SC - Ea - sa ass All apparatus advertised in this magazine has been tested and approved_by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 45

tr) [ ci'

Separate All Stations Evenly T is not necessary to tear dawn and rebuild your present I set in order to separate the stations evenly on' the dials. By merely substituting Rathbun Straight Line Frequency Converters for your present dials -you will be able to se- cure real S. L. F. tuning. of Here is a variable vernier control that provides a ratio gradually 50 to 1 down where the stations are crowded - smoothly decreasing in uniform ratio over the full and around 360° of the dial. The stations are evenly separated the entire circle. There are only two moving parts -a cam and a lever. The action is dependable and accurate -with- a particle of backlash. Easier tuning and immeasur- out line capac- ably better logging are obtainable from straight ity condensers with these nëw converters. we build the Rathbun Single Hole Mounting Condenser Remember that enclosed with' with genuine Bakelite ends. This year's models are pyralin dustbands which preserve their high efficiency transparent always reasonably priced. for life. They are small, light and rugged- Frequency Converters Ask your dealer for Rathbun Straight Line He has them in stock or will get them for you promptly PRICE $3.50 RATHBUN MANUFACTURING CO., INC. JAMESTOWN, N. Y.

has been tested and approved by POPULAR RADIO LABORATORY All apparatus advertised in this magazine

www.americanradiohistory.com 46 The Best in Radio Equipment HEADQUARTERS The For LC -26 Parts R.,. L )1i RJ.ramm arlund General Radio Parts E.I.S. Apparatus oberts Dubilier Condensers Foundation Weston Meters Unit Formica Panels Contains All Special Parts Premier Jacks Cunningham Tubes General Electric Tungars Mahogany Cabinets t9.40 Needed for the Flammarlund- Special Engraving Roberts Receiver Special Condensers, Coils, Shielding, Etc. No General Catalog Issued Write for Quotation on any Radio Apparatus or Material Required. NORDEN- HAUCK, Inc. ENGINEERS 1617 Chestnut Street, Philadelphia, Pa.

G -K SPRING BINDING POSTS The interest in this new wonder circuit is nation- wide and justly so. Here is a five -tube receiver with the sensitivity and selectivity of a super- heterodyne, representing the composite ideal of ten famo.:s radio engineers. You can easily build it yourself with the Ham - marlund-Roherts Foundation Unit and the parts listed below. 2 Hammarlund 2 Rauland -Lyric S -L -F Condensers Transformers 1 Hammarlund 1 Carter Rheostat, Jack Midget Condenser and Battery Switch 1 set Hammarlund- I Durham Resistor Roberts Coils 4 Amperites 5 Na -aid "Deluxe" 3 Dubilier Condensers Sockets 5 Pairs Union Phone 2 Na -aid Dials Tip Jacks Send 25 cents for illustrated booklet giving complete details on assembling, wiring and operating the Hammarlund- Roberts Receiver. HAMMARLUND MFG. CO. 424 -438 W. 33rd St., New York 3oc., I3.ottec, Radio-

Built for the RADIO FREC/S/ON Leading INDUSTRY. Choice of 1JammarIund Engineers. Genuine Bakelite Knob- Spring PRODUCTS Contact and Release- Patented. List 15c Each Inquiries Solicited from the Trade N!r GANIO- KRAMER COMPANY, INC. 238 -40 West 53rd Street New York City All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY www.americanradiohistory.com The Best in Radio Equipment 47

-IMP' " :- - .

' ç/ 11 ' ' Q 1

THERE are no better meth - SYLVANIA tubes are made - ods or processes known slowly, with infinite care. than those used in the mak- Step by step, under the crit- ing of Sylvania tubes. The ical eyes of a corps of inspec- "' guarantee `` ) l of complete satis- tors, they pass from one faction, without reservation, 1 skilled workman to another. ? to every user of Sylvania And into each piece and part tubes is substantial proof of k`

is , put only the finest mate- , it. If you have not experi- i rials and the best workman- ! enced Sylvania performance, ship that is within the reach ?' if you have not discovered of the radio industry. Then for yourself their greater vol- 1 there is test after test to estab- ume, keener sensitivity, better lish beyond any question of tone, and longer life -you doubt that each tube is the have an almost unbelievable exact counterpart of every radio performance before you. other tube. is Thus it that To Radio Dealers : Behind each you can try set after set of ` Sylvania tube' stands a thoroughly \ Sylvanias in your receiver and responsible organization, well known get from each the same un- and respected. It will be worth your ii while to write us regardless of any varying degree of quality per- present connections. You are invited formance. to investigate the Company's respon- sibility through any of the commer- cial agencies. d

t'`'kr QN v.- r .mtiì" v . -°-A4f0.d ...... 0 + 4c + it$ ......

A size and type 1 Ito for every need, $2.50 !

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SYLVANIA PRODUCTS COMPANY 1 EMPORIUM o o PENNSYLVANIA

has been tested and approved by POPULAR RADIO LABORATORY 411 apparatus advertised in this magazineó www.americanradiohistory.com 48 The Best in Radio Equipment

Many valuable pages of the latest, approved hook -ups and information are contained in the new big Barawik Radio Guide and Catalog. This valuable book is sent free to radio fans. Shows thousands of new standard radio parts, sets and kits at tremendous savings. Set Builders Headquarters We r. uurantee savings to you of 10 to '>'; , and as high as 50 %, so be sure to get this book before you spend another cent for anything in radio. We are the oldest mail -order institu- tion specializing in radio supplies. It will pay you to do business with a house that knows the goods and assures you a square deal. Send us your name and address - dll postal or letter -(also please include name of radio friend) and well send free copy at once.

Here Are a Few Sample Bargains from the Barawik Catalog Guaranteed 201A type Tubes $1.15 Guaranteed 45 -v. large B batteries 2.55 Complete parts for kemler-Best 8 -tube Super 48.45 :rea Complete parts for B -T Counterphase -6 63.50 Complete parts for Silver Super Autodyne . 62.50 jllSl Complete parts for Hazeltine Neutrodyne 29.25 Complete parts for Browning -Drake circuit 32.25 Complete parts for McLaughlin 8 -tube Super 82.50 !110L Urger direct from this au or gc' tree copy of our complete &14' catalog of everything in radio IIaIlE Jirne has. \\

with ih Only _r Wa//aDial.? FREE BLUEPRINTS

In UNIQUE design of Wade Condensers spreads stations over the entire 360 depiee dial. The Wade is a complete tuning untt built with specially designed vernier dial. Thus means twice as much space between sta- tions for close tuning adjustment; even wider separation of stations than the rotor plate types of straight line frequency condensers using W-1 standard 180 degree dials. None of the annoy- THE ance of overlapping stations and jumbled recep- / tion. The Wade Condenser gives the lowest RL?dioFan minimum capacity and wider tuning range. Is one who finds he cannot get selectivity Covers and distance because he has used cheap the whole broadcast range and down transformers. To prove the selective and below 200 meters. sensitive combinations obtainable with- Wade Tuning Unit Including Condenser WERNER and Dial Radio The Wade Tuning Unit consists of a Wade Con- Frequency denser geared to a four -inch 360 degree vernier TRANSFORMERS, dial of 16 to 1 ratio. Finest which cover the entire broadcasting wave possible control range and have been with no backlash. Prices below are for the used by the best complete unit. radio Engineers for the past 2 years, we will furnish a full size Blue Print of a Capacity .000125 selective loop receiver FREE mfd. $6.00 from if you order Capacity .00025 mfd. 6.25 us direct. Capacity .00035 Audio teed mfd. 6.35 and tested 'on actual broadcast reproduction; Capacity .0005 mfd.. 6.50 Freq. guaranteed damp and moisture perfect reception proof and will Mt-4 $6. in any climate. THE VIKING TOOL AND MACHINE WERNER LOOP ANTENNA CO., INC. Used with any type of loop Licensee R. F. a fine degree receiver. Adjustable t4 cf clearness, can be folded or extended 745 -B 65th Street $4. without tools. Brooklyn, N. Y. Price Postpaid $14.00, Send Ask for free circuit diagram and descriptive liters. tore. Book containing 9 up to date practical Your circuit diagrams and treatise R. F. Dealer. postpaid, 25c. on R. F. Ampli[lcntit,n, Werner Products Approved by -Popular Radio." WERNER RADIO MFG. CO. 204 -206 NINTH STREET BROOKLYN, All apparatus N. Y. advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY www.americanradiohistory.com The Best in Radio Equipment 49 The Best Panel Is Also The Most Handsome

Because of its structural strength, fine lsulating qualities and splendid finish For - iica has been preferred as a panel material y the great majority of makers of quality idio sets. Complete Formica Panels supplied with ecorations by the Veri- Chrome process ave an attractiveness that makes them reat favorites with set buyers. In numer- us instances where manufacturers making different Models have used \Teri- Chrome decoration on one lanel and not on others, the Veri- Chromed panel las proved to be a large sales maker. When you select your radio set ask to see one v ith a Formica panel decorated by Veri- Chrome -and form your own conclusions. Complete panels decorated with Veri- Chrome re available for some of the better known kits. n some instances the Veri- Chromed panel is ncluded in the kit package by the manufacturer. Formica panels in standard sizes are sold in neat ndividual envelopes by leading parts dealers :verywhere. THE FORMICA INSULATION COMPANY 4641 Spring Grove Avenue, Cincinnati, Ohio SALES OFFICES New York, 50 Church Street Philadelphia, 725 Bulletin Bldg. Chicago, 9 6. Clinton Street Baltimore, 709 Title Bldg. Cleveland, 516 Caxton Bldg. Havanna, Cuba, 55 Calle Obispo Rochester, 327 Cutler Bldg. Boston, 6 Beacon Street Toledo, 419 Ohio Bldg. Denver, 1420 16th Street Minneapolis, 1026 Second Avenue St. Louis, 1362 Syndicate Trust Bldg. New Orleans, Whitney Central Bldg. Kansas City, 308 E. 17th Street Pittsburg, 422 First Avenue ORM I CA. Made from Anhydrous Bakelite Resins SHEETS TUBES RODS

RADIO LABORATnRY All apparatus advertised in this magazine has been tested and approved by POPULAR

www.americanradiohistory.com 50 The Best in Radio Equipment 1 OrtrecoaconteenrOWililint

FIXED RESISTORS

ACME WI RE FIXED RADIO PRODUCTS CONDENSERS "Made of Mica and Moulded in genuine Bakelite" Capacity of Resistors and Flexible Celatsite Condensers guaranteed Flexible stranded wire for within 5% and constant "point to point" and sub - in value. panel wiring- latest method of wiring sets. 5 colors; They are indestructible black, yellow, green, red and moisture proof. and brown, one for each circuit. 25 ft. coils. At all good Radio Stores. MICAMOLD RADIO CORP. FLUSHING AND PORTER AVES. BROOKLYN, N. Y.

The Original Celatsite Wire Celatsite is a tinned copper bus ACCURACY GUARANTEED bar wire with a non -inflammable -VAL UESREMA /N CONSTANT "spaghetti" insulation in five colors. Supplied in 30 inch lengths. MOULDED UNDER PRESSURE Flexible Varnished OF 50 "Spaghetti" TONS A perfect insulation tube for all danger points in set wiring. Costs little more and is worth a lot more than the cheaper substi- tutes offered. Black, yellow, red, green, brown; for wires No. 10 to No. 18. 30 inch lengths. ATTENTION w Stranded Enemele d DEALERS ACME Antenna The best outdoor anten:a you can i . put up. 7 strands Send for our 200 page catalog ,, of enameled copper wire; max mum surfa.,e for recep- tion. Enameling prevents cor- consequent weak signals. 100, 150 oro200 ft. coils, oxed. Loop Antenna Wire You can make a good loop with Acme wire made of 65 strands of fine copper wire, green silk covered. Flexible; non -stretching, neat. Celatsite Battery Cable For connecting A and B Batteries (or current sup - ply) to radio set. Silk braid covering 5 flexible Celatsite wires -5 feet The finest and largest long -a different color exclusive each) ter- for minal. Pre- Radio Catalog in the vents messy wiring"blown" and United States tubes. Adds greatly to the appearance of your set. Send for folder THE ACME WIRE CO., Dept. P Schneitter New Haven, Conn. Radio Company Dept. G. St. Joseph, Missouri

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 51

THE beautiful simplicity of the Hammarlund- Roberts is Send for one of the many stirring features that have made this This Book receiver the talk of the country. Gives you step -by -step t directions for assem- The creative genius that conceived the idea of a masterly bling, wiring and oper- five -tube receiver, ating the Hammar- and the engineering skill that brought the lund- Roberts receiver. idea to reality, kept always in mind the limited mechanical Fully illustrated. ability of the inexperienced builder. The result is a plan of 2 5c. assembly so complete, so detailed, that a man or boy, following the step -by -step directions in the instruction book, may con- Associate struct the Hammarlund- Roberts in the course of an evening. Manufacturers The masterpiece of leading All- American Radio ten engineers -equal in perform- Corp. ance to a standard eight -tube set -backed by some of the Alden Mfg. Co. Radiall Company best -known parts manufacturers in the radio field -this is (Amperites) the Hammarlund- Roberts. Today it is the one Carter Radio Co. radio receiver Union Radio Corp. talked about above all others. International Resis- tance Co., Inc. (Durham Resistors) Complete assembly, less cabinet, $62.30 Westinghouse Micarta Hammarlund Mfg. Co., Inc. HAMMARLUND -ROBERTS, 1182 -B Broadway, New York

- may Ì} Ott Here are some of the famous parts used in the Hammarlund -Roberts f4MPIIRIPi

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com J? The Best in Radio Equipment

Z1151lZ71--LOWL0S5

Volume with True Quality! THE value of radio as an entertainer in- creasesonly with the realism andquality of reception. This requires good broad- casting-reception and amplification equal to, or better than, the broadcast range of audio frequencies -and a loud- úícl{,posiiive tuning speaker of uniform response over the same range. Heretofore one of the weak SPEED, ability to turn directly to links in this chain has been the audio any station, to tune in instantly and amplifier. get your station on any wavelength and But it is now possible with AMERTRAN De to eliminate crowding of stations at the Luxe audio transformers to obtain faithful, lower end of the dial, is the outstanding strong reproduction over a range of frequencies feature of the Ultra-Lowloss Condenser. down to the lowest pitched audible sound. This is nearly three octaves lower than that previously With one station of known wave- obtained. The deep boom of the drum, the length located on the dial, all others thrum of the base viol, and the thunder of the pipe organ are reproduced with startling,real- can be found instantly. Special de- ism -and at no sacrifice of the highest notes sign of Cutlass stator plates distributes within the audible range. Once tried, the stations evenly over dial AMERTRAN De Luxe will be recognized as set- the -each ting a new high standard of excellence in audio degree on a 100 degree dial represents amplification. approximately 3% meters difference in wavelength. AMERTRAN DeLuxe requires no special circuit other than the use of a large tube in the last stage to pret ent overloading at the low frequencies In addition, losses common in other bought out. It is made in two types. condensers are reduced in the Ultra - Price, Lowloss to a minimum by use of only either type, $10.00 one small strip of insulation, by the AMERICAN TRANSFORMER COMPANY small amount of high resistance metal 178 Emmet Street, Newark, N. J. in the field and frame, and by a special "Transformer builders for over twenty-four years" monoblock mounting of fixed and SOLD ONLY AT AUTHORIZED AMERTRAN DEALERS movable plates.

Designed by R. E. Lacault, E.E., originator of the famous Ultradyne receiver and Ultra -Vernier tuning controls. The Cutlass Stator Plate (illus- AMERTRAN Audio trated above) is exclusively an Ultra -Lowloss Transformers type AF6 feature. (turn ratio 5) and AF7 (turn ratio 3%) have Mr. Lacault's personal monogram seal been substantially (R. E. L., also shown above) is your guarantee of reduced in price. As before, satisfaction they are today the leaders in their class. No and Lacault design. changes have been made in the electrical char- At your dealers; otherwise acteristics since they were first sold. Either send purchase price and you type now $5.00. be supplied postpaid. We have prepared a booklet describ- ing these and other A nterTran products, together with recommen- tthTR71-bOÙJbO$ dations for their use. We shall be glad to send you a copy upon request. CONDENSER Be sure to see other AmerTran ad on page 58 PHENIX RADIO CORPORATION 116 East 25th St. New York, N. Y.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 53 AROUND THE WORLD -*

2L0 London 40 m., 5MA Ade- 365 m., 2FC Syd- 1 a i d e 850 m., ney 1100 m., RH CYX Mexico City Vienna 600 m., 350 b., FL Eiffel BAV Haeran 1100 Tower 2600 m., m., DKP Kbely 2BD Aberdeen 495 1150 m., KOM- m., PRG Prague AROV 1800 m., 1000 m., PCGG OXE Lyngby, The Hague 1070 2400 m., BER- m., 2FL Sydney LIN 430 m., PAS 770 m., STOCK- Amsterdam 1050 HOLM 440 m., m., EBX Carta- HBI Geneva 1100 i gena 1200 m., m., WGY Sche- ROME 470 m., nectady 1660 m., LP, Konigswus- BRESLAU 415 terhausen 680 m., m., KG0 Oak- WGY Schenecta- land 361.2 m., dy 109 m., 3L0 C K A C Montreal Melbourne 1720 425 m., CHAC m., KOA Denver Halifax 400 m., 322.4 m., BUDA- PWX Havana 400 PEST 2000 m., m., KDKA Pitts- SBR Brussels 270 burgh 64 m. m., WEAF New FRANKFORT York, 491.5 m., 467 m., WO4Z HAMBURG 392 San Antonio-, 394.5 m., WMBF Mi- m., NAA Arling- ami Beach 384.4 ton 2500 m. m., CFAC Cal- CHXC Ottawa 435 gary 430 m., m., WOC Daven- WGY Schenectady port 483.6.

Traveling around the World A yacht equipped with a Universal Plio -6, traveling around the world, would hear broadcasting programs every night regardless of its location, because the Universal Plio -6 tunes all wave- lengths from 35 meters to 3600 meters. An American owner of this Golden -Leutz Receiver can listen for all European stations as it tunes to the different wave -lengths used by foreign broadcastes. In addition, for reception of American broadcasting stations from foreign countries this wonderful receiver, designed by Chas. R. Leutz, is already breaking distance records. Cable, wire, write or phone for literature today Manufactured by GOLDEN - LEUTZ, INC. (With which has been incorporated Experimenters Information Service and L.11 S., Inc.) 476 Broadway - - New York City CABLES "EXPERINFO," NEW YORK

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment if A RADIO CABINET OF BEAUTY AND ELEGANCE DIRECT TO YOU AT LOWEST COST Lid splined both ends to prevent warping. Nickeled piano hinge -Full length. Nickeled lid support of artistic design. Anti -vibration cushion feet (not visible in cut). Edg: s of lid moulded to match bottom. Shipped securely packed in strong cart )11. Prompt shipment. Big stock for holidays. Hardwood. Rubbed Solid Black Mahogany American Elms, Walnut 7 x18 x or 10 in. deep $3.50 $5.00 7x21 x 10 in. deep 3.75 5.25 7x24 x7% or 10 in. deep 4.00 5.50 7x26x712 or 10 in. deep 4.75 6.25 7 x 28 x 7 or 10 in. deep 5.50 7.00 7 x 30 x 7 or 10 in. deep 6.00 8.00 Add 25e. for "E -Z" Fone plug. CASH WITH ORDER or C. O. D. if '.t of price is sent with order. Prices F. O. B. Hickory, N. C. Order express shipment, often cheaper than mail and much safer from damage. FREE WITH EACH CABINET a glued -up stock non -warping 32- inch BASEBOARD. Free Catalogue. THE SOUTHERN TOY COMPANY, INC. Dept. N. HICKORY, NORTH CAROLINA

The HeIiotor FAHNESTOCK A Trite CONNECTORS Popular Whereve Toroid Radio Is Used! FAHNESTOCK Perfect Radio Connectors are used by Manufacturers of Standard Sets and Parts -and Makers of Wet Have you noticed the increased use of toroid- Batteries and Dry Batteries. Their Sure al coils in the finer sets? Here is an oppor- Patented Grip is Recog- tunity to have a real toroidal coil. nized Universally by En- HELIOTOR center weave construction thusiastic Users. forms maximum induction section with small coil diameter and low interturn capacity. ANTENNA CONNECTOR Resulting compactness of Eliminates splicing and solder- turns with improved ing of wires. Snap larger con- position of toroidal primary gives greater power nector over antenna wire; insert and selectivity. You can use HELIOTORS lead -ln wire into smaller clip and a perfect connection is the result. in all types of radio frequency sets. SIzes for Made of the finest quality .00025. .0003. .00035. and .0005 condensers. Phosphor Bronze. Range front 200-570 meters. Our bulletin on "BETTER AMPLIFICA- TION" gives complete description of HEL1- OTORS with hookups and methods of in- stallation. Yours for the asking. May we send you one? GEO. A. FREEBURG CO. 165 Lovell St. Elgin, Illinois

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment On Wings they ride the ether waves

J

Patented July 25. 1925: May 2, 19:1 Patented July 25, 1925: May 2, 19U

BL. BNJkM.LN CLE RA-TON .Shaped fir E greater separation Shock Absorbing Radio Socket n short wate Rations Stops tube noises.

C Assures clear reception. Patents Four delicately adjusted Pending springs support the socket and absorb all jars and shocks. Benjamin Low Loss, The Cle-Ra -Tone Socket "floats" above its Long Range Condensers base. First of all a wonderful low loss condenser. The Bakelite, used wherever possible, insures shape of the rotor blades eliminates bunching of sturdiness, long life and high insulation. stations on the lower side of the dial and makes tuning very easy. Unpolished silver plate finish. Flexibility of springs is not affected by stiff bus Friction disc on rotor shaft adjusts turning ten- wiring. sion without loosening or throwing plates out of alignment. Made in three sizes: 13 plate for Handy lugs make soldering easy. .00025 Mfd., 17 plate for .00035 Mfd.. and 25 Benjamin Cle- Ra-Tone Sockets prevent the plate for .0005 Mfd. Drilling template fur- transmission of outside vibrations into micro- nished with each condenser. phonic disturbances., "Push" Type Cle - Ida -Tone Socket

Patents Pending A socket made with the precision of a jeweled watch. It embodies all of the wonderful shock Benjamin Tuned Radio absorbing features and qualities of the regu- Frequency Transformers lar Cle-Ra -Tone Socket. Even in what has been considered an excellent The "Push" Type Socket is designed to ac- set, it is astounding what an improvement in commodate the new standard UX "push" type tone, quality, volume and selectivity the intro- base radio tube. It will also take tubes with duction ofthese coils produces. Low Resistance. Low Distributed Capacity. Space wound, air the ordinary bases, excepting the UV -199. core; double green silk insulation - the nearest approach to an al! -air dielectric construction and the highest type of inductance possible. Sold through Radio Jobbers and Dealers everywhere Benjamin Electric Mfg. Co. 120.128 S. Sangamon Street, Chicago 247 W. 17th Street, New York 448 Bryant Street, San Francisco Manufactured in Canada by the Benjamin Electric Mfg. Co. of Canada, Ltd.. Toronto, Ontario

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY www.americanradiohistory.com The Best in Radio Equipment 221 Volt un -acid everlasting rechargeable"B" Storage Battery $2.95 _.'. :rµ- NRWLEYBST01t+'fF includes d'.iTTRY chemical 45 volts $5.25, 90 volts $10.00, 112:¡ volts $12.50, 135 volts $14.75, 157íz volts $16.80. Truly the Used in the biggest buy today. Easily charged on any current including 32 volt systems. Any special detector Cockaday L C-26 plate voltage had. Tested and approved by lead- I he Precision Octaform Coil shown above ing authorities such as POPULAR RADIO laboratories. i, the coil used in \lr. Cockaday's new LC- Over 3 years sold on a non -red tape 30 day 2o trial Receiver. Price $5.50. offer with complete refund if not thoroughly satis- fied. Further guaranteed 2 years. Knock -down The Cockaday LC -26 Receiver kits at greater savings. Complete "Hawley" "B" Kit Battery charger $2.75. Sample cell 35c. Order For the convenience of those consumers direct -send no money -simply pay the express- and dealers who wish to buy the Cockaday man cost on delivery. Or write for my free litera- LC -26 in complete kit form we offer the ture, testimonials and guarantee. Same day ship- following parts exactly as used in Mr. Cocka- ments. day's laboratory model. B. HAWLEY SMITH, 315 Washington Ave., I General Radio variometer, type 269, Danbury, Conn. equipped with rheostat knob $5 30 i General Radio rheostat, type 214 -a, 7 ohms, equipped with rheostat knob 2.25 I Precision Octaforin coil set 5.50 I Amsco special double unit condenser RADIO MANUAL No. 1814 each section .0003 mfd. 6.25 WITH FREE I Micamold fixed condenser, .000r5 mfd .35 i Micamold fixed condenser, .00025 mfd .35 2 Daven resisto- couplers (new type which incorporates .1 mfd. condenser con- POPULAR RADIO cealed in base). 3.00 Kendall Banning, Editor, and Laurence M. Cockaday, 1 Amertran DeLuxe transformer, first stage 10.00 Technical Editor of POPULAR RADIO, have compiled a book Bradleyleak, % to 10 meg. 1.85 that will prove to any one that he can build a set which will 3 Bradleyunits, 3. megohm 2.2$ give distance, selectivity and tone volume, and at the same I . time Bradleyunit, _ megohm .75 a very definite basic knowledge of radio. 3 Ainperites No. la 3.3o BUILD 1 YOUR OWN SET AND Amperite No. 112 1 .10 SAVE MONEY g Benjamin standard "Cle -ra- tone" sockets 5.00 In "How to Build Your Radio Receiver," you will find I Carter single- circuit jack, No. tot .7o complete specifications, constructional diagrams, photographs 2 ('arter Jack switches, No. 2 2.00 and instructions for building all of the following 8 Eby sets: binding posts I .20 A $5 Crystal Set 1 Fynur vernier control knob and dial 3.50 The Haynes Single -Tube 1 Universal decorated panel, 22 Receiver Blueprints 8 x inches 7.5o A Two -Stage Audio -frequency Amplifier 1.00 The Cockaday 4- Circuit Tuner 4 Small brass brackets A 5-Tube Tuned Radio -frequency 1 Antenna connection Receiver block, s X 2 inches The "Improved" Cockaday 4- Circuit Tuner 1 Battery connection block, 1 x g inches The Regenerative 2 Large brass brackets 1.75 Super- Heterodyne Receiver Screws and buss wire ADVISORY SERVICE ALSO Solid Walnut FREE Cabinet 17.00 POPULAR RADIO maintains a big modern trained staff laboratory with a Total of investigators under the personal supervision $81.go of Mr. Cockaday. This Laboratory is always available through our Technical Service Bureau to answer, free of charge, Parts for the Cockaday "B" Eliminator by personal letter any problems you encounter which are not answered in either the "Handbook" or the magazine. (Raytheon Plate Supply Unit) In POPULAR Ranio each news month you will find the very latest This kit contains all the of the radio field as well as helpful suggestions and in- parts exactly as structive and entertaining articles on radio and allied used by Mr. Cockaday in designing his lab- phenomena. scientific oratory model which was described in the SPECIAL BOOK OFFER November issue of POPULAR RADIO. You can secure a copy of "How to Build Your Radio Re- ceiver" FREE, and have all the privileges Service Bureau of the Technical Dealers -Write for without additional expense, if you will send a information on remittance of $3.00 in full payment of 12 months' for POPULAR RADIO. (Or subscription Coils and Kits. book as an alternative, you may have the and privileges of the Technical Service Bureau with POPULAR RADIO for 7 months only bill will do.) -for $2.00. A two dollar Remember you take no chance -we will refund your money Precision Coil Company, Inc. in full if you are not more than satisfied. 209 Centre St. New POPULAR RADIO York, N. Y. Dept. 15 627 West 43d Street New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 57

The Six Point A Pressure Condenser Certified Check THE "Electrad" Certi- Against fied Fixed Mica Con- Distortion denser is a revelation in accu- As clear and mellow as chime sounds -Let the racy and design. Ingenious, "Electrad" Audiohm banish that stuttering, sputter- ing reception forever. rigid binding and firm riveting If you want pure tones, clear and mellow, whether fastens securely Six highs low or medium pitch, improve your set with the parts at Audiohm. Insure reproduction that will equal in different points, insuring posi- smoothness and richness the original tones of the artist. tive electrical contact. Im- Build or improve your set with "Electrad" Radio Essentials- Certified Grid Leaks. Variohms, Lamp pervious to temperature and Socket Antenna, Resistance Coupled Amplifier Kits, and many others. At your dealer's. If he can't climatic variations. Exerts supply, write. even "ELECTRAD" AUDIOHM -Price $1.50. Elimi- pressure upon the largest nates distortion. Easily attached to possible surface work secondary of first audio transformer. -can't Once set it's permanent. loose. Binding strap and soldering lug in one piece. Accuracy and quietness as- sured always. Value guaran- teed to remain within 10% of calibration. Standard ca- pacities, 3 types. Licensed 1,181,623, "ELECTRAD" LEAD - under Pat. No. IN-Price 40e. May 2, 1916, and applications Fits under locked win- dows. No holes to bore. pending. Price 30c to 75c in Extra waterproofing. Meets the quality stand- sealed dust and moisture - ard set by "Electrad " - there is a difference. proof packages.

ELECTRAD INC. 428 Broadway, New York City

I I

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 58 The Best in Radio Equipment

`erw 'z, Are You the Man to be first in your town to sell and demonstrate POWEROLA, the fa- mous 5 tube, no- battery electric light socket radio receiver (not an attach- ment), universal for D. C. or A. C. A Real (100-115 v., 40 -60 cycle), now sold THE NEW t and demonstrated by Power Transformer YORK EDISON CO., public utility companies and radio, electric and The modern home may now utilize its music dealers everywhere. Abso- electric service for the operation of a lutely dependable, fully guaranteed, Radio Receiver. Reception is greatly im- powerful, practical, perfect in per- proved when efficient B and A eliminators formance. are employed to use this steady power. Are You the Man The AmerTran Power Transformer Who Sees Opportunities Ahead Type PF -45, 65 VA -60 cycles 110 volts for Real Money Making primary, 450- 8/4 -8/4 secondary, is in- Write for literature, terms and prices tended for use in converting the standard at once. 110 volt, 60 cycle alternating house light- Sig ing current to a higher voltage for the plate and low voltages for filament sup- POWEROLA RADIO CORP. ply. It can be depended upon to give Dep't. P. R. 1845 Broadway, N.Y. City good results when used in connection with the different tubes now available tlo: and is designed with the usual margin of Or( safety. It is a real power transformer, in design, construction and usefulness. ha The AmerTran Power Transformer Type PF -52 DON'T sa is another transformer of the AC Power Type similar to Type PF -45 except that it has a plate ber winding for 525 volts ACand a metal ground shield between the primary and secondary windings. WAIT! to i TYPE $150u PEP UP THAT SET NOW WITH Price: F-45 ~ TYPE $I800 me' X - L RADIO PRODUCTS AMERICAN TRANSFORMER COMPANY Just install them in your receiver and Sta 178 Emmet Street, Newark, N. J. hear them speak for themselves Auc "Transformer builders for over twenty -four years" Endorsed by POPULAR RADIO LABORATORY Tht SOLD ONLY AT AUTHORIZED AMERTRAN DEALERS.. and other leading radio authorities in all the latest circuits 2,0( Model "N" Vario Denser trot, Capacity range 1.8 to 20 micro -micro- farads, for balance -n in Roberts two tube, Browning- Drake, McMurdo Silver's Knockout, Neutrodyne and tuned radio frequency circuits. Price $1.00 Model "G" Vario Denser For the Cockaday circuits, filter and intermediate fre- quency tuning In super -heterodyne and positive grid bias in all sets. G- 1- .00002 to .0001 MF. G- 5- .0001 to .0005 MF. The AmerChoke Type 854 is a choke coil or G -10- .0003 to .001 M F. impedance of general utility designed primarily Price Each With Grid for use in filter circuits. It has a current ca- Leak Clips, $1.50 pacity up to 60 milliamps. and a no load induc- tance of approximately 100 henrys at 60 cycles. X -L Push Post Price $6.00 each. A binding post that really does excel In looks, action, service and convenience. We have prepared a booklet describ- Just push it down- insert wire - cannot ing these and other AmerTran jar loose from vibration. No screw- products, together with recommen- ing or danger of shearing off wires. dations for there use. We shall be Furnished attractively plated with glad to send you a copy upon request. soldering lug and necessary markings. Be sure to see other AmerTran Price Each 15 Cents ad on page 52 X -L RADIO LABORATORIES 2422 Lincoln Ave. CHICAGO

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 59 This Transforms Your Radio

DOLLARS NOW CONFIRM IT

Signal . strength multiplied 188 times in possible shorter aerials. It stabilizes any ;cientific test by the marvelous Penetrola set ; prevents radiation ; keeps you far A; as an astonishing announcement. Ques- from oscillation. Nothing else can do it. :ions swamped us. But proof was positive. Quickly, easily, any set can be transformed Drders, cash, rush requests followed. Never with Penetrola, amplifying ahead of detec- has there been such a radio sweep. The tion, where weakest signals can be saved. Same features responsible for supreme Wal- The highest priced receiver alone might not bert Isofarad radio showed Penetrola able approach your present set, plus Penetrola 'Lo improve any radio set beyond all known at $35 complete in stunning black Crystalite nethods. case, for instant attachment, no wiring or Station WCBD, for example at 29 on the changes needed. Penetrola kit with full Audibility Meter, was spoiling WCAL at 35. instructions $15. Fans everywhere have Then on comes Penetrola -WCAL now avoided delay by remitting cash direct to .2,000 and WCBD now zero! That's Pene- factory for prompt shipment. State whether trola selectivity, intensification, and volume you use aerial or loop and make of set - -normally every time ! It even makes mention dealer's name. Walbert Isofarad is the only complete receiver with Penetrola results built in. The Isofarad kit gives you most advanced radio with greatest economy. Send 25c for the Isofarad booklet, explaining how elusive radio principles are now applied prac- tically by Walbert. PENETROLAWAL.BERT MFG. CO., 947 Wrightwood Ave., Chicago All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 60 The Best in Radio Equipment

DEPENDABLE RADIO PRODUCTS Lightning Arresters - ADIO CAB! N ETS by D N N approved by Fire Under- writers. Retail .. Soc Complete Aerial Kits - every- thing for complete installation with instructions. Retail .... $3.50 Resistance Amplifiers- all assembled and I'IFj ready for use. Retail . . $8.00 Audio Frequency Transformers - tests have proven the quality. Retail ...... $2.25 Automatic Shock Proof Phone Plugs -a real value at this price ..... SOc Mfd. by LESLIE F. MUTER CO. 76th & Greenwood Ave., Chicago Sold by All Leading Radio Dealers those* who know r ecommencd

Fixed eondenSerS *Tested and approved by M. I. T., Yale, Radio News, Pop- ular Radio and Popular Sci- ence. Used by 200 of IllY Transform your present radio set into a hero - over tif.rl cons.>le msdel. Your panel assembly America's leading set manu- drops right into the AD APTO Cabinet without facturers. changing a N ire or disturbing a part. Storage I attery drawer that permits refilling and re- Made in ail capacities. Also manu- charging without lifting battery out or disturb- facturers of Grid Leaks, Resistors, i ing a wire. Load speaker horn, built right Resistoformers and Rheostats. into cabinet. Three models in mahogany or walnut. Write for illustrated folder. another reason whyjou should insie on them..

Chicago Office: 53 W. Jackson Boulevard Cincinnati: 304 Palace Theatre Building

Iii AEROVOX WIRELESS CORPORATION 491 Broome Street New York City All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 1 The Best in Radio Equipment

Powel Crosley, Jr., has always done the unexpected. His announcement Dec. 26th is no exception to that rule.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 62 The Best in Radio Equipment

mml 1,nn,nnnnmu.nniinii,, niinrnnmiiiiiinunmmIIiniimm,c rnnuuuuumunumnmmMmnunw And Now- The Carborundum Stabilizing Detector Unit BUILT around the Carborundum FixedDetec.. tor is this simple, highly efficient stabilizing device. By adjusting the detector resistance to match the circuit it absolutely controls self os- ciliation in the radio frequency tubes. $3.50 It permits operation at peak of regeneration. \ It gives N U. S. greater sensitivity- increased selectivity - BATTERY)\ (WITHOUT clearer tones. The Carborundum Stabilizing Detector Unit gives a potentiometer controlled booster voltage to the Carborundum Fixed Detector. A small sized flash -light battery is all it needs and of course it comes to you equipped with the genuine Carborundum Detector. Send for Descriptive Circular Showing Hook -Ups. From your Dealer or Direct MADE BY THE CARBORUNDUM COMPANY, NIAGARA FALLS, N.Y. New York : Chicago : : : : Boston Philadelphia Cleveland Detroit : Cincinnati : Pittsburgh : Milwaukee : Grand Rapids BANISHES DETECTOR TROUBLES Backlash in this ATewDial

Used in Cockaday's new LC -26 RECEIVER The Fynur dial operates by traction (not gears) so that no backlash or lost motion is possible. With Fynur dials you can get greater distance, and separate the low wave- length stations perfectly. Dual control. A quality dial for those who want the best - beautiful, mechanically per- fect, and durable. So simple in con- struction that a child can take it apart VERNIER and reassemble it. Manufactured by August Goertz & Co., Inc., 270 -286 $3.50 CONTROL Morris Ave., Newark, N. J.

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All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

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PACENT TRUE STRAIGHT-I I N1. FREQUENCY CONIANSIK

Pacent Electric C.nlmip" 91 Seventh Ave., Now Wabhinrl.9n Jst,k.tkx, Birmingham UP ifY'1 Ikuuít 13044," Cliurra C,asb-

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www.americanradiohistory.com 64 The Best in Radio Equipment Why WEBTON Popularity? Continuous and long -life depend- ability! Assurance in use! Beauty Result s of design! These are the reasons for the great popularity of these two of the famous Weston Radio Line. The Weston Instant-Change Radio Plug, the pioneer automatic device of its kind, gives fast, positive and most satisfactory contact between headset and loudspeaker. The Weston Model 489 Radio Table Voltmeter supplies a portable instrument of great value ln checking all voltage conditions of radio sets and has given thousands of radio enthusiasts more economical reception, longer t"be life, better battery service, more resonance in tone, greater volume and distance. To get the best from your receiving set use a reliable and dependable volt- meter. Write for the complete Information contained in our new free edition of "Weston Radio Instruments."

WESTON ELECTRICAL INSTRUMENT CORPORATION 115 Weston Avenue Newark, N. J. WEBTONSTANDARD THE WORLD OVER t/`'ion eers since 1888

YOUR RADIO QUESTIONS ANSWERED POPULAR RADIO, with which is combined The Wirrlt. 8 Age, subject, writing on one side of the paper only, and enclose maintains for the benefit of its readers a Technical Service self -addressed and stamped envelope. Bureau and Laboratory, under the personal supervision of It is possible Laurence M. that your individual problem has been covered Cockaday which will, without charge, answer in an issue of POPULAR RADIO, and so as an by personal letter any question, problem or re quest for endeavor aid to you we information to keep a supply of back numbers in stock. The submitted by a subscriber. This service is, condensed index below gives a few of the subjects however, also available to readers, other than subcri.Jers, at appeared recently, that have the very nominal look this list over and if the information rate of 50 cents the inquiry. you want is covered, we will be pleased to supply back In writing please confine your questions to one general numbers at 35c. a copy. March, 1925 June, 1925 -Call Letters That Have a Past. -How to Build the Improved DX Regenera- -New Development In Vac:nrn Ti',es. -Broadcasts. tive Receiver. -How to Build a Five -tune A -C Receiver. -Factors that Govern the Capacity of -How to Draw Up Your own Tuning October, 1925 Condensers. Chart. -How Earth Magnetism Affects Radio -What "Induction" Means to Your Set. -Watt's Law in a Nutshell. Waves. -A Five Meter Vacuum -tube Transmitter -'What Set Shall I Buy?" -How to Improve Broadcast Reception. and Receiver. First Installment. -What Makes a Low -loss Coil? -How tc Build the New 8 -Tube Super- April, 1925 July, 1925 heterodyne with a Single Control. -Single Control Receivers. -The Best 101 Hook -ups. November, -"What Set Shall I Buy?" 1925 -How to Improve Broadcast Reception, I: Second -Radio's Newest Instrument Photo- Increasing the Selecting Power of Your Installment. -the Broadcast Stations in the United electric Cell. Receiver. - States. -How to Build the Raytheon Plate Supply -How to get the Most out of Your Ready- - What's New in Radio Apparatus. Unit. made Receiver. -New Methods of Calibrating Your Re- -Quartz Crystal as a New Wavelength August, 1925 ceiver. Standard. -"Motion Pictures" by Ether Waves. Pra -tical Pointers About Transformers. -A New Type of Hornless Loudspeaker. -Multi- -layer Coils. - How to Build a 5 -Tube Radio- Frequency May, 1925 Set with Simplified Control. December, -Factors That Affect Antenna Capacity. -Trouble Shooting. 1925 -How to Wire Your Home to Have Radio -Hints for Amateurs. -flow to Build The New LC -28 Receiver. in Every Room. -How to Improve Broadcast Reception. -Handy Tools for Radio Fans, The Hydrom- September, 1925 -What Every Radio Experimenter Should eter. -How the Air Affects Radio. Know About Condensers. -How to Build the "Portable -" Truthful Reproduction," How to Get Town and -Mien You Turn Your Dials. It from Your Set. Country Receiver." - - Useful Charts or Amateurs. -Radin that Runs on a Beam. rl

627 West 43d Street Dept. 18 New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY www.americanradiohistory.com The Pest in Radio Equipment h5

THIS HANDSOME CABINET, MASSIVE AND ARTISTIC IN DESIGN, WILL GRACE WITH BEAUTY THE RICHEST SURROUNDINGS. BEAUTIFUL HAND RUBBED FINISH IN RICH ADAM BROWN. EVERY PIECE OF FINEST QUALITY KILN -DRIED MAHOGANY.

There is no higher (lass workmanship The Raised Panel or Iietter nuslerinl Ends and Grace used in making the ful Ogee (beveled) richest and I est edge Running furniturr than Ihnt Completely embodied in Baker Around Cover to- ('u inets Our gether with the products are not 10 Beautiful Grain of lie elnssed %%ith Wood Contribute "Iladi Boxes" hut in Making Baker are exquisitely- di- Cabinets Superior si{;ned and beauti- in Design and fully finished Itadio Finish. Furniture that Will dignify any atmos- phere.

There are generous rubber feet on base, heavy felt rests for cover and stay -joint to hold cover when open. All hardware is heavily nickeled. Standard panels fit perfectly in rabbeted grooves (not slots. Space is provided for Dry Cell "A" and "B" batteries which may be placed behind instruments and wiring of set.

"BUILT WITH THE GRACE AND BEAUTY OF A YACHT" BAKER CABINETS are carefully wrapped in wax paper to protect their beautiful finish and packed in heavy fibre cartons. Shipped Knocked -down, in but four pieces, they may be as- sembled in a few minutes. Screws are furnished and holes already drilled. No baseboard is required. The cabinet's base is used for mounting instruments. Sides and top may be re- moved quickly when changing hook -up or making repairs. Accuracy in panel sizes and perfect fit of all parts absolutely guaranteed. PRICE LIST, TYPE A -65 PRI('E LIST, TYI'E B -s'I1 Inside Depth Ten Inches Behind Panel Inside Depth 8 Inches, Behind Panel Cover. sides and base are built of mahogany Built of mnht.ranv which finishes line -half one inch in thickness. inch in thickness. 7x14, *10.50 7x14. *12.30 7x1. ti14.50 7x1á. $8.75 7s14, 50.50 7x18, $10.50 7x41, 7x44. $18.511 7xLG, 7x-21, *1l.311 7x-24, 7x6, $13..i11 ti 7x38, $20..50 7x30, $á1.50 7x28, I I.uU 7x:311, $I3.1111 IF DEALER CANNOT !-I'PI.Y. ORDER DIRECT BY NI 111, 1NI) WE «"ILI, ;IIII' Pll1M1Yi'LY, CHARGES PREP.IID .\ \\ HERE IN THE UNITED .;1'.1"II:,. I pi r, RI:1 I:IIYI' I Il PRICE. 5.1TI5F.11'TION GUARANTEED. BAKER YACHT BASIN, INC., Quincy Point, Mass. Jobbers and Dealers Write for Trade Discounts to QUINCY QUALITY PRODUCTS COMPANY, INC. DISTRIBUTORS Queens Village, L. I. New York

All apparatus advertised in this magazine lias been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 66 The Besi in Radio Equipment Separate those crowded This is the low -wave stations by D only Dial D where no the smooth, hair -line backlash tuning D can ever of the D develop D t D Try them on your Q set Read our Micrometer D guarantee `uninq D t DII AL D We also Guarantee: GISCHO`M D This dial will abso- NEW YORK Ratio 100 to 1 lutely tune in from sren In price the 20 to 25% more sta- cheapest D tions, than any other PROVEN BY TEST for the No Backlash dial-Try Them ! SUPREME MASTER work it does. D FOR SHARP TUNING and none can ever develop OUR D If the GUARANTEE use of the GEE HAW DIAL does not materia improve the selectivity set on which it is installed, it may be returned of any radio D dealer) and purchase to us (accompanied by bill of sale from manufacturer price refunded without question or argument. Does any other i of dials dare duplicate this offer? Price $3.00. D i Knobs made of Bakelite, scales D reading 0 to 100 -Black or Silver finish, 100 to 0- Black or Silver, 200 to 1 -360 0 Black. D SI517- S1 D OHO R.GISCHOW Co INC. I25West M. SIMONS D & SONS CO , Export Div., 220 B'way, N. Y.

1 D D D D D D D D D D D D D D D D D D D D D D D i H GET YOUR SET OF BANK WOUND SIMPLIFIED LOOP BLUE PRINTS FREE "Remarkable Efficiency Combined with Unusual Beauty" You know how helpful, interesting Has your receiver the and practical POPULAR RADIO selectivity, is. You fully appreciate volume, clarity that at $3.00 a year it is a real bargain. and range that it should Consequently You should find have? it easy to convince one, two or more of your friends who The FIAT are not now subscribers, of the unusual value will fulfill and when any one even surpass expectations in ,7i these eight sets of Simplified Blueprints (described the on page 84) attainment of greatly is offered free with their twelve months' subscription improved reception. for Contrary to a pop- POPULAR RADIO at the regular price of $3.00. ular belief the FIAT In addition to the Blueprints given loop can be used on to your friends we will allow you such sets one set free for each new as the Neu- subscription you send us with a $3.00 re- trodyne and Brown- mittance. Five new subscriptions ing -Drake by a slight and remittance of $15.00 would circuit change. The entitle you to five sets free. resulting reduction in Only one set of Blueprints static interference free with a renewal subscription whether and improved tone your own or a friend's. quality are amazing. A Browning -Drake e Ima ae ims set built for test and POPULAR es used with the FIAT RADIO, INC., Dept. 13 has consistently 627 West 43d Street, New York City brought in K.F.I. Los Enclosed is my Angeles on the loud remittance of S covering annual sub- scriptions for POPULAR RADIO (names on sheet speaker at Chicago. me set attached). Send Diagrams showing the neces- (s) checked below. sary circuit modifications will Set No. 4 be sent on request. \\\\ Set No. 11 In efficiency and appear- Set No. 6 ance, the FIAT loop surpasses Set No. 12 all others. Set No. 7 Set Furnished No. 13 in genuine WAL- Set No. 9 NUT or MAHOGANY, highly Set No. 14 polished. Arranged to tune (See page 84 for description of Sets) with .0005 M.F. condenser. Provided with center -tap. Name.... Patd. Oct 27. 1925 PRICE $12.50 Address RADIO APPLIANCE LABORATORY Foreign postage 50c. extra. No extra for Canada. Dept. "P" 4884 -90 North Clark Street, Chicago, Ill.

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment o7 f/ìw4t ffQ aefîr 11ff. à ief Marks a new era in Radio progress- Sweeping country like a tornado - Fans welcome it with open arms - Irresistible demand growing by leaps and bounds -- KARAS Started It- and KARAS Is Carrying On!! When we sprung the Karas Orthometric Condenser bucket. Buyers pleaded -cajoled -even threatened.. on a restless, hungry radio public -we knew we had Our plans were doubled, trebled, quadrupled. started something. But we scarcely expected to be But it all took time. snowed under with such a literal avalanche of orders. KARAS Orthometric Condensers could not be We inaugurated Straight Frequency Line Tuning thrown together. It took months to train gangs to at the psychological moment. Radio Fandom was build them with the absolute precision KARAS de- waiting hungrily for something new. And here mands. So tens of thousands had to wait or buy was something -not only new -but so perfectly other makes, hurriedly assembled to supply the simple -so thoroughly scientific -so downright demand we had created. sensible, that everyone wanted KARAS Ortho- NOW -after months of preparation we are able to metric Condensers at once. produce enough KARAS Orthometric Condensers Our scheduled production was like a drop in the to take care of at least a fair share of the demand. How KARAS Orthometric Condensers Simplify the Tuning of Any Radio Set o !O '° w^ *o 'ß ,9 inn w-AV,Lr ítWr,lyrfr :6 j.S p50 .r, 2 o V READ/ÑC 3e ,gyp áplRfs4DINC° .742 ° Ó o r" ? Of MW s 3 \': W KARAS oaTHOMETRI000NOENsER Arngement Ordinary Condenser Arrangement of Wavelengths Straight Wavelength CondenserArrangement of Wavelengths on Dial Ordinary straight capacity condensers With straight- line -wavelength cönden- Karas Orthometric Condensers insure crowd 70 of the 100 wavelengths sers57ofthe100wa %zlengthsarecrowd- absolutely equal dial separation of all into the first 30 points of the dial. ed into the first 30 points on the dial. wavelengths, 200 to 600 meters. U. S. Gov't. separates all stations 10 kilocycles apart. Old type Karas Orthometrics are both theoretically and mechanically condensers - straight line capacity and straight line wave- perfect. Made entirely of brass - plates patent leveled and length- crowded the low wavelength stations into the first securely bridged to insure permanent alignment. Every few degrees on the dial. Difficulty in tuning- confused hetero- dyning interference- garbling of programs-these were the joint soldered. Grounded frame and rotor. Adjustable cone results. KARAS Orthometrics give low wavelength stations bearings. Spring copper pigtail. In short, so beautiful a the same equal separation as high ones. It is the last word in job that one engineer, on seeing the condenser for the first making real selectivity possible. time, smilingly inquired, "How many jewels?" If your dealer hasn't secured a stockof Karas Condensers KARAS ELECTRIC COMPANY 4037 North Rockwell Street, Chicago, Ill. For more than JO years makers of PRECISION Electrical Apparatus. Note the Order on this Coupon! long Most good dealers everywhere, sell ccntrrc Karas Orthometric Condensers. If your Raras Electric Co., p lates ////' dealer happens to be one who hasn't se- 4037 N. Rockwell St., Chicago cured them, we will supply you di- Please send me Karas Orthometric Con- rect on our 30 -day -Back Guar - densers, size at$ each. Money I will pay the postman the list price, plus postage, on deliv- antee.Just fill in and ery. It is understood that I have the privilege of returning mail this coupon these condensers any time within 30 days if they do not prove - NQgr:: at once. Send no entirely satisfactory, and you will refund my money at once. Or IIIIIIIIIIIWIIIIIIIIIIIIIIII 111 11/0 money. Pay your \`...ÌWUstLoCwnloto ® PATAFPL' ÓN, postman on de- livery. Name Prices Sizes and - Address Ea " 23 plate, .0005 Mid. 47.00 17 plate, .00037 Mfd., 6.75 11 plate, .00025 Mfd., 6.50 Dealer's Name 5 plate, .0000972 Mfd., 6.50 If you send cash with order,we'II send package postpaid

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 6 The Best in Radio Equipment

LEADER -Loud Speakers -Units Beauty Beauty in in Appear- Tone ance The The LEADER LEADER SENIOR JUNIOR, (as illus- exactly the trated) 22 same except inches high, in size, 18 13% inch inches high, bell. List 12 inch bell. Price List Price $18.00 $14.00

PATENTS PENDING LEADER Speakers combine a wide range of volume with clarity and faithful reproduction of tone. The heavy cast aluminum gooseneck eliminates all metallic and vibration distortion. The bell is beautiful mahogany or walnut finish -the base and gooseneck in wine-gold. THE LEADER UNIT An adjustable horn unit for any horn. Console or phonograph List Price, $5.00. - Sample horn sent to any reliable jobber on approval at our expense. VICTOR RADIO CORPORATION The First 4319 N. Western Avenue, Chicago radical improvement in radio SLF condensers AT LAST! A new era in variable condensers. Professionals recognize in the new FUR - NELL Condenser -based on an entirely new and simplified principle-the most practical and efficient condenser ever designed for Straightline Frequency tuning. It is the only condenser of its type on the market and experts agree that: "It's the most important step forward that has yet been made in its field." The FURNELL replaces open multiple plates with two shielded plates, each coiled in the form of an evolute. Assures clean -cut separation of stations, tone clarity and scientific precision heretofore impossible. Dust - proof, moisture -proof, damage-proof. Each condenser complete with special 4 inch Bakelite 360° Dial and enclosed in transparent dust -proof case. Exclusive Sales Franchises Available to Reputable Jobbers in Locations Still Open. -it's ¡ii heTubè Write for Literature Your receiving set can be no better than its tubes. CECO Tubes give maximum results in clarity of tone, rich volume Furnell Manufacturing and long life. Corp. Our charted tests (results confirmed by laboratories of na- 24F St. tional reputation) PROVE CECO TUBES SUPERIORITY Scott Newark, N. J. -as detectors, as amplifiers. Buy CeCo Tubes whether your set takes one tube or eight. Now ready! CeCo Tubes with new type Long PRONG BASES. Also, power amplifier tubes, E (Dry Cell Type), F (Storage Battery), for last stage of Audio Frequency. Ask your radio dealer. C. E. Mfg. Co., Inc. F 702 Eddy St., Provilence, R. I. 360° TAPER COIL CONDENSERS

AU apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 69

Most - Demonstrated Set of the Season From radio as you have known it, to Thorola Islodyne is as great a change as

could happen, even in radio ! Here is so much of an advance that it seems to put final highest development into view. Thorola Islodyne now brings you radio safe from being surpassed. Only the Thorola Islodyne principle of Isolated Power makes it all possible. Based on the epochal discovery of Thorola Low - Loss Doughnut Coils, Islodyne action literally isolates the radio impulses -keeps them from interfering with each other - from tangling up -from weakening them- selves -gives you closest tuning always. Sharpest selectivity is certain, wherever you are. Tone is unbelievably pure, since interference is defeated. Superabundant volume is available at extreme distances Illustrated: 5 -tube Thorola Islodyne in Burled Walnut because power, instead of being wasted, with Circassian $100 is top neutralized, or damped, put fully be- New Model 51, Genuine hind one chosen station only. Mahogany $85 Cabinet These amazing results, free from mysteri- ous, unmanageable, disappointing old ele- Console Model .. $225 ments of radio reception, are the regular 5 -Tube Thorola Islodyne in of Thorola Islodyne receivers. smart Thorocco performance Finish $85 Excellence is uniform in all Thorola sets, Thorola 4 Thorola Jr. and throughout the range of reception. Speaker Speaker C2, Your radio parties proceed as scheduled. $25 $15 Stations come in as logged. Words and Islodyne action is based on come in as broadcast! Thorola Low -Loss Dough- music nut Coils. They bring many Thorola advantages to other It is the latest proof of Thorola eminence, receivers first established by the matchless tonal cilose 3$12 coil $4 accuracy of Thorola Loud Speakers. Now Thorola Low -Loss Straight there is a complete receiver, Thorola Line Frequency Condensers can also be bought separately Islodyne, even further ahead. Go to the $550 and $6 nearest Thorola store and listen to the most radio set. Thorola Golden Audio Re- -demonstrated producing Trans- $450 former 4.-- REICHMANN COMPANY, CHICAGO c./`iPfioCz

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 7 The Best in Radio Equipment Two food "Signal" Loops

Table Take Your Choice- Type A bracket type that attaches w Bracket Complete right onto $8.50 the end of your radio Type cabinet or a table type -you i Complete can't miss it on either one. When $8.50 you buy a Signal Loop you're buying more than just good looks. You're buying an aerial backed by thirty years of ex- perience in the manufacturing of electrical equipment. Where quarters are close, remem- ber the bracket type loop at- taches right onto the end of your set and does away with that "extra piece of apparatus." It turns a complete 3600 in the width of the standard cabinet. Both aerials are beautifully constructed. The bracket type is of solid walnut. All metal parts The table type is mahogany finished. are heavily nickel plated. A third tap is provided for sets requiring it. Ask your favorite dealer to show you the Signal Loops- either type $8.50. You will surely want one. Jobbers and Dealers. If you are not fully acquainted with Signal Radio Products, we will be pleased to send you complete information. Write us at once for literature. Signal Electric Manufacturing Co. Pr nca All Dept. 10 -A Pri ncippe! Citiesities Menominee, Mich.

J screw- machine " products Price y . A2 -ó0 4.00 ' - Set of brass Each ` Three For plugs, jacks, clips, con- denser and transformer parts, etc., BRASS assures 4 o 4 economy in quantity produc- Toroidal Transformers tion. It Seven Points of Superiority also gives the right I. Correctly distributed external primary. 2. Absence of usual secondary eddy- current losses. electrical conductivity and 3. Maximum magnetic coupling with minimum capacity coupling. the mechanical accuracy es- 4. Sturdy construction without coil housings to absorb energy. sential to proper operation 5. Spaced low -resistance windings. 6. Silver plated primary reduces skin losses. 7. Each turn a perfect toroid. No trick -style wind- of radio sets and parts. ings with losses at every angular bend. RADIO FANS -If your dealer cannot supply you, get the facts -write us! DEALERS -Practically all the jobbers recognize COPPER BRASS NAXON superiority and stock a supply. If your RESEARCH ASSOCIATION jobber cannot supply you now write us direct. 25 Broadway, New York Naxon Electrical Laboratories Inductance Research Division 4524 -26 Cottage Grove Avenue, Chicago

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment il

ZONE - 1 KFOT to 200 meters

A Separate Circuit for Each Meter Wavelength Band! WAVE - MASTERS 40 Standard Model $125.00 KELLOGG - for 28 years makers of precision tele- phone instruments - producers of quality parts since radio began - Kellogg has perfected a radio receiver worthy to bear the Kellogg name. In the new WAVE - MASTER range of 540 degrees - over three there are nine separate circuits - times the range of any other set. wavelength one for each 40 meter All other radio frequency sets max- band. Each circuit gives that have variable capacity which must imum efficiency heretofore found be tuned, usually with three dif- only in one short section of the ferent dials, to balance with their dials of ordinary radio frequency inductance coils. sets. Each circuit brings within the range of the tuning dial a dif- The WAVE-MASTER'S in- ferent group of stations. ductance is not fixed but variable and is easily and quickly tuned, Merely set the pointer to the wave with the one dial, to balance tha zone in which you are interested fixed capacities and tune in with the one dial. WAVE- MASTER Write for full description. Please Brown Wutnut Console This dial actually ha3 a tuning mention your radio dealer's name. with inbuilt horn $ 275.00 Ask for Folder No. 6 -A. Kellogg Switchboard & Supply Company 1066 W. Adams St., Chicago, Ill. Radio Dealers and Jobbers The WAVE.MASTER franchise, backed by Kellogg resources and our powerful advertising campaign, is most valuable. Wire, or get into Chicago, quick, and SWITCHBOARD & SUPPLY CO. see us. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 72 The Best in Radio Equipment ff "Take No Chances -Use Como COMO DUPLEX The World's Standard Push Pull Transformer

Patented Noy. 18, 1924

oiu/penl tr Tonsole PRICE $11.00 per pair For maximum volume without distortion What Prominent Writers on Radio Subjects say About Como. Lewis B. Hagerman, Technical Editor, Chicago For EVERY Post: "Actual Tests show this transformer to be far superior to any others of similar makes." R. J. Robbins, New York Sun: "After consideration of several well -known makes of push pull transformers Radio Set which are available 'COMO DUPLEX' was selected as most satisfactory." A stunning piece of furniture that restores or- C. White, Radio World: 'COMO DUPLEX' is infi- der in the room where you have your Radio! nitely superior - most other push pull transformers seem to be ordinary tra nsformers with a center tap No more cluttered table -tops, nor litter of brought out as a makeshift." equipment under -foot. E. P. Gordon, Open Road: "A system of audio- ampli- fication which is becoming increasingly popular. No unsightly Its use horn in evidence, .. . will give surprising results in both quality and volume, either! This console has its and is thoroughly recommended by this department." own loudspeaker, in- built. It's out of sight, but with very NEED WE SAY MORE ? apparent tonal superiorities. For it has the highest -developed COMO APPARATUS COMPANY type of unit. With horn built Manchester, New Hampshire of special non -vibrating, extra - For Sale at Leading Dealers hard material. Produces clear, non -vibrant tone. There's ample room for every- thing; space for A and B wet batteries -or battery eliminator -and for a charging outfit, too. Finished in mahogany, or wal- nut color. Dainty design of Non parqueterie on two front panels. -Vibrant Horn Top, 38 in. x 18 in. The clearest tone pro- Additional pattern No. 128 ducer on the market. (Special for Radiola No. 125) in Made of special com- "a new 5 -Tube Set two-tone finish. Top, 21 in. x position which defeats with all 31 in. Fitted with the power doors for vibration. and none of the access to control switches of grief of the Supers" combination eliminator- charger. - so wrote Henry The price, forty dollars, is for the complete console and in- M. Neely, Editor of cludes the loudspeaker horn and unit. Thousands of Radio in the Home, dealers are showing this artistic addition to home radio Philadelphia. equipment.

Rear View -Set Hooked UP Get This Book Write today for this big fascinating 32 -page booklet which tells how you can build the truly amazing new QUADRAFORMER receiver. Based on a new radio principle, five tubes Price, $10 give remarkable West of Rocky Mts., $42.50 results. Enclose 10c and you'll have it by return mail Windsor Furniture Co. 1430 Carroll Ave. Gearhart- Chicago. Ill. Schlueter Radio Corp'n 714 Voorman Avenue, Fresno, California

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 73

Enchanting Radio Nights for Everyone Each night, when a myriad flash- sulating properties made it ideal for ing lights make fairylands of the tube bases and sockets, trans - cities, a million folks tune in. Play- formers, rheostats and many other weary youngsters hear wonderful parts and accessories. That its bedtime tales; light- footed boys and strength and permanently beautiful girls dance to the rhythmic music of color and finish made it superior for fine orchestras, and their elders panels, dials and knobs. listen to great musicians and world- Make sure that the radio equip - famous men. Winter nights no ment you buy is Bakelite Insulated. longer drag in Radio Homes. 95% of the radio set and parts Bakelite played no small role in manufacturers use Bakelite. bringing radio within reach of all. Write for Booklet 28. Makers of radio sets and parts quickly found that the use of Bake- BAKELITE CORPORATION lite improved both performance and 247 Park Avenue, New York, N. Y. appearance. That its splendid in- Chicago Office: 636 West 22nd Street. "The registered Trade Mark and Symbol shown below may be used only on products made from materials manufactured by Bakelite Corporation. Under the capital "B" is the numerical sign for infinity, or unlimited BAKLTEquantity. It symbolizes the infinite number of present and future uses of Bakelite Corporation's products." THE MATF,RIA A 'CHOUSA USES REG. II. S. PAT. OFF.

Bell Mfg. Co. Shaw Insul. Co. Polymet Mfg. Co. Airgap Products Co. O. R. Gischow Co. Vernier Dial. Dial. E. Z. Stat. Socket. Gee Haw Dial. All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 74 The Best in Radio Equipment r Standard Parts Mr. Laurence Cockaday's L. C. 26 Broadcast Receiver RAYTHEON

Improved tour circuit tuner, single dial control, one stage of radio Irecuency, amplification, cannot oscillate or radiate. BLUE PRINTS FURNISHED Parts sold in kit form or separately Parts Used by Mr. Cockaday in Building his Laboratory Set List Price I General Radio variometer, type 269, equipped with rheostat knob $5.30 r General Radio rheostat, type 214-a, 7 ohms, equipped with rheostat knob 2.25 I Precision Octaform coil set 5.5o I Ameco special double unit condenser No. 1814, each section .0003 mfd. 6.25 I Micamold fixed condenser, .000xs mfd. .35 I Micamold fixed condenser, .00025 mid ,35 2 Daven resisto- couplers (new type which incor- porates .1 mfd. condenser in base) 3 .00 I Amertran DeLuxe transformer, first stage 10.00 Bradleyleak 4, to ro meg 1.85 3 Bradleyunits, y megohm 2.25 1 Bradleyunit / megohm .75 Progress comes not a 3 Amperites 1So. Ia. 3 .30 through happy hit I Amperite No. 112 x .10 or miss process. In each link of the broad- 5 Benjamin standard "Cle-ra-tone' sockets s .00 i Carter single circuit jack, No. rot .70 cast chain -from microphone to loud 2 Carter Jack switches, No. 2 2.00 8 Eby binding posts 1.20 speaker -we realize the results of years I Fynur vernier control knob and dial 3.50 4 Small brass brackets of unremitting effort for something I Antenna connection block 1 x 2 inches I Battery connection block, i x g inches .80 better. Today attention is focused on the 2 large brass brackets elimination of the battery, that most un- 1 Bakelite Complete Parts (including $59.75 reliable and expensive source of electric p drilled and engraved Panel 8 x 22) power now in commercial use. That this IMM IMP should come about as a result of scien- IVo Alao Carry Comp!, te Part.. For tific research was to be expected. That it HAMMARLUND should make possible an added beauty R OBERTS- RECEIVER of tonal reproduction gives further Endorsed by Ten Leading Radio Engineers Engineers of the leading manufacturers who make these parts endorse the assurance of the permanency of the operation of the Hammarlund- Roberts Receiver only when it is constructed with these specified units which the designers have found to coordinate most RAYTHEON rectifier in this field. efficiently with one another. Order from this list and we guarantee you prompt delivery. Unit No. 1. 2 Rauland -Lyric Transformers at $9.00 $18.00 RAYTHEON, the result of five years of research Unit No. 8. 2 Hammarlund .0005 mfd. Model "C" or and experiment, and the work goes on to main- S.L.F. Condensers at 6.00 10.00 tain Unit No. 2. 1 Hammarlund "Midget" Condenser 5 plate, 16 the standard already set. Ask your dealer mmfd at 1.80 1.80 to explain the meaning of Full Wave Recti- Unit No. 4. 1 Set Hammarlund- Roberts Coils at 6.00 6.00 Unit No. 6. 2 Na -aid Super DeLuxe" 4 in. Bakelite at .75 1.60 fication, No Filament, Reserve Power, and Unit No. 6. 6 Na -ald "DeLuxe" Sockets at .75 8.76 a sixty milliampere ratifier for six dollars. Unit No. 7. 1 Na -aid K8844 -1f' in Dial at .20 .20 Unit No. 10. 1 Carter 26 -ohm "Imp" Rheostat at 1.00 1.00 Unit No. 11. 1 Carter Single Circuit No. 101 "Hold -Tte" RAYTHEON 's -eliminators or specially designed parts for home -built Jack at .70 .70 Unit No. 12. 1 Carter "Imp" Battery Switch at .65 .66 units are made and sold by these and other well-known manufacturers: Unit No. 16. 1 Durham Metallized Resistor at .40 .40 Unit No. 8. 4 Amperites No. 1-A at 1.10 4.40 Acme Apparatus Co. Unit N. 18. 1 Dubilier Type 640 -G .00025 mfd. Grid Condenser at .50 .60 All -American Radio Corp. Unit No. 14. 1 Dubilier Typo 640 .002 mfd. Fixed Con- Dongan Electric Mfg. Co. denser .45 .45 Unit No. 15. 1 Dubilier Typo 640 .006 mfd. Fixed Con- General Radio Co. denser at 80 .80 Jefferson Electric Mfg. Co. Unit No. 9. 6 Prs. Union Phone Tip Jacks. qer pair at .25 1.25 Unit No. 17. 1 Hammarlund- Roberts Foundation Unit (con- Mayolian Radio Mfg. Co. tains engraved bakelite Westinghouse Mi- Thordarson Electric Mfg. carta panel, drilled bakelite sub- panel, Co. metal brackets and wire at 9.40 9.40 Tobe Deutschmann Co. Complete Parts as specified $60.80 Cabinet $10 Extra V RAYTHEON MANUFACTURING Booklet "How to Build the Hammarlund- Roberts Receiver" with Com- COMPANY plete diagram and illustrations -Postpaid 25c CAMBRIDGE, MASSACHUSETTS hhHEINS & BOLET 44 PARK PLACE, NEW YORK

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment î:5 only usa a s G ht turn of the dials with Chicago localand stations broadcasting /get everywhere outside.

IOWESr RADIO STATION clçiornna. , SELECTOR 2 ,

. .0

COUNTER BALANCER JL'ONE QUALITY

-wí/ :: 4°°, I.:-;,F ' nimwuullnw IIH ïuuuuwunu IñEú- lamiuunuuuew

Built Tike -looks like- performs like a $200 sot. 27 In. long. ewe mske to líscrs echo will demonstrate Get Amazing Offer our set to friends. e ciwerful.lew Notice! Enormous demand for the cele- brated Miraco 't'Ultra -5 (resulting from its many enthusiastic users so highly recommending their it to friends) enabled us to add co hosts of costly new features, lat- Guaranteed by Tested and Approved est refinements and up- to -the- One of the Oldest minute improvements such as you by Radio's might expect to find only on the Radio Builders Highest Authorities newest sets selling at much high- er- prices. So the Improved Ultra -5 better set more for 1926 is even a -a beautiful set -a m Ire selective and ULTRA SELECTIVEFIVE TUBE SET IN MAHOGANY CABINET] more powerful set -inc- edible as this may soundl -f.,r less money than ever before. You can either save or make a lot of money J COAST TO COAST RECEPTION by sending coupon today for our Amaz- Reporti VERIFIED BY USERS ing Special from users of the Pow, rful New Miraco Ultra -5 Offer. It will astonish yon. Just say you'll let your friends listen to everywhere leave little for us to add. powerful of the thousands These are only afew the new Miraco Ultra -5 in your home and we ship it to you ON APPROVAL in our files and which we receive daily; at the wholesale price CALIFORNIA THE FIRST NIGHT TUNES OUT POWERFUL NEARBY -satisfaction unconditionally guaranteed. The wonderful selec- ßeeaired KFl Los ASgelea,CaI. and STATION AND 'GETS DISTANCE tivity, long distance range, clarity of ?elegise City the ant sight, besides We are surely having fine lack tone, power and volume of this famous set abort twenty mora on my Ultra -6. the set. with plus its beauty of appearance and splendid - Ray K We get everywhere with construction -will sell it to your friends. Big profits .... Eaton. Oblo. Chiens stations broadeaating. for you -accepting their orders. No salesmanship required easy CANADA W11 e now live about -no agreement to sign. You can TO THE GULF AND one mile from accessories at wholesale from us', also buy COAST TO COAST WIN. the Drake Hotel, it has s Even at its retail price this latest improved big beautiful 1926 model I sure do Ilke the Miraco Ultra-5. I wavelength of 870 meters and on all Miraco Ultra -5 is an astonishing bargain, in the opinion of radio authorities. got from CET. Winnipeg,Canada, ohreets around here they are not Remember, too, that each ble to qqet out or any Miraco conies completely built, thornughty tested fully to WOMB, New Orleans d from get other ep- and guaranteed by the great Midwest Radio Cor Yoittnight. tign witiioutalso heerion't ay. Bat poratiun -one of America's oldest reliable and most successful makers Ma, cloys. MbCaator with our Miraco 6 we don't haveh any of quality sets. Send coupon now. Bi. trouble. Just a slight Ora of the dtale and it isnt there. We can get Compare its colts -- CUTS THROUGH THE LOCALS outside any night better than our Struction with Below -rear view o9 Mt. Sal er;goli 4 tree: tM neighbors. Here are some outside highest priced sets eeiebrated ÌI made eeb apd on a we heardWJo fournl hoe Isere -e mood workmanshipthere I. Capin be best. the loudspeaker: WJJD WOÏtD, the neat. amrdy. IIIIIIIBIIIIIIIIIIn knosy t then le anything ri t, WCBD WLIB WSMB ,Hew Or- gggh- phyl t y'I1 II (I bring Imusl'rkAI, í70C WSM, WEAF Alih wiring, concealed 41' % II ÍIIII IIIIIII --__ inI . J.H A Pittsburg. New York City) erased Ousel. "I NÍ .... ::,1 Í II IIL._.IIIIIIIIIUIIIINIIIIIU Neb.) under nemmne Formica (f , (III PRAISES ITS CLEAR KOA ,i)enven KFNF rl TONE Á ( (A). ' WRAS, WLW; base panel Wir- -- t1 Received the Ultra- 6, It WAF Wb. Everyone is outtli in ing flexible to pre- I I\ I(I feetistheave thatdeanthetilers -6to in vent broken or noisy G ortmol ever . 1 ud gotten e040 end a is nois. Herman or more enalif.stations including cmnect!ons: Genuine I:jC, ACFI, Lee C ... ,Chicago, NIA i oe Calif. W. A. C Formica panel (B f t CCALIFORNIA PENNSYLVANIA NEARSHEARS - CALIFORNIA vCUBA handsomely gold- AGFHEIFIREARSENININNATI Your works s,eevir; from etched on front. THE FIRST Los Angeles to eras, everything Oscillations are I wish to thank you for a r. in floe. H L Roy oehea easily controlled on all nee shin pwp perfecttastier. con Pa. i wave -lengths and "B" battery con- which thethe Ultra6 fir- . rndlUonlábe I have rovep your SOLD IT THE DAY RECEIVED sumption is minimized while selectivity, distance range, to be andt.i e tone, i received m Miraco Ultra-6 a few elanty and volume are amazingly increased by the Thlame, and dbpvice dáye ego an Id it the very same patented are excellent. Counter -Balancer" (C) and "Duoformer" ultra low lose inductance e fiat oveping I en))oyyed a eon- ght. The buyer i ry (D, E and coils cart from Cincinnati ulab w a foe. Jacob F). Adjustment for different length aerials (G). Shielded Et E. S eaebrated make, transformers, of - Eon Francisco. Cal. . KlC .. Beulah, N.N, Dak. amplify without distortion (H and f Lowest dielectric loss base panel. Low loss plate condensers type sockets -riveted into NEW YORK GETS 'EM COAST 67 STATIONS IN FIRST -and other latest features of costliest sets. Literature describes fully -send TO COAST FEW DAYS for it! I have one of your Mimeo Ultra-6 Our untra-6 anted fine shops, radios and It working fine. I get Had no trouble at all hooki aRsht uo. alaptiovs from core[ t. seas[ and Set it- abnut 11:00 s3 would Ilk to be one of your agent.. h lg éo e I ptiona, ln

All apparatus advertised in this magazine has been tested and approved by POPULAR RABIO LABORATORY

www.americanradiohistory.com 76 The Best in Radio Equipment

Better Tone! Build Your LC -26 -with dry cells and UX 120 than with storage batteries With the Aid of Note: The UX 120 is a new three volt dry battery power Popular Radio Blue Prints tube. Used for audio fre- quency amplification, this tube will produce better quality and greater loud It is Easy speaker volume than regular storage battery tubes. Quick and Accurate Any set owner can easily install a UX 120 The LC -26 is the ideal all-around receiver, com- tube in his set in a few bining unusually fine tone qùality, selectivity and minutes by using the distance- getting ability, with simplicity of con- new Na -Ald Number 120 struction and operation. It operates on any antenna Connectorald. It is a from 10 feet to 200 feet long, indoors or out. simple, efficient means of introducing the necessary additional "B" In tests at Washington, D. C. the LC -26 brought and "C" voltage required for this tube into in over 40 stations in one night, the farthest away the plate and grid circuit without rewiring being KGW, Portland, Oregon. the set. As easy to use as an adapter. Just slip the Connectorald onto the UX 120 tube At Chicago, Ill. the LC -26 brought in KFI, Los and put the tube in the socket. Connect the bat- Angeles, every night for a week, and over 60 other teries- and -well, that's all there is to it. Except stations. WEAF, New York, was heard clearly at to enjoy a quality and volume you would not have believed possible. No need to fuss with charging eleven o'clock in the morning. batteries. The simplicity, -economy and freedom from attention characteristic of dry cells is now At New Haven, Conn. it brought in WMBF at combined with the real volume and quality previously Miami Beach, Florida, at 4:00 P.M., as well as New obtainable only with storage battery tubes. York stations for which New Haven is a dead spot. The No. 120 Connectorald is suitable for all sockets -metal neck as well as insulated. For sale at radio, electrical and hardware stores. Price, $1.25. All reception on the LC -26 is on the loudspeaker, as it has no phone connection. Na -Ald Adapters By using POPULAR RADIO Blue Prints in building Na -Ald Adapter 419 -X your LC -26, you can save time, eliminate the possi- bility of error, and make your set exactly like the With this adapter the Na -Ald de Luxe Socket will take the new UX 199 laboratory models. small base tube. Price, 419 -X, 35 cents. The Panel Layout is' exact size. It can be used as a template for marking off the location of all Na -Ald 420 Connectorald screws and holes. No. 420, equipped with cables, enables owners of Radi- The Instrument Layout is also exact size and can be ola Super-Het to get the great increase in volume and clarity used as a template for locating all instruments, the new 11X -120 tube develops. and screw holes. Price, 420, $1.25. The Wiring Diagram is approximately exact size Na -Ald Adapter 421 -X and shows clearly the location of every wire and No. 421 -X makes possible the shift connection. It also carries a list of all parts used from WD -11 to UX tubes. Especially in building the laboratory set. designed to enable owners of Radiola III, and III -A to enjoy the improved local operation the new tubes provide. If your dealer cannot supply you with Blue Price, 75c. Prints of the LC -26, they will be sent postpaid on All Na -Ald products are for sale at radio, elec- receipt of $1.00 per set. trical and hardware stores, everywhere. Send for complete data on adapters for new tubes. A full description of the LC -26, with detailed direc- tions as to how to build it, was published in December ALDEN MANUFACTURING COMPANY POPULAR RADIO. Also Makers of the Famous Na-Md Sockets and Dials DEPT. C12 SPRINGFIELD, MASS. I\ Alden Processed POPULAR RADIO Service Bureau 14 -A 627 West 43d Street NA-ALO New York Sockets and Dials

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com Ti.e Pest in Radio ent 77

Whether You Buy or Build Insist on EBY Cushion Sockets The most important elements in any set are the tubes. There's no getting around that ! And what else but the sockets are re- sponsible for the life and efficiency of those tubes? Whether you build or buy see to it that the tubes in your set are mounted on EBY Cushion Sockets. The design of this revolutionary socket provides a three -point wiping contact on each of the four tube prongs. Each spring clip acts as a shock -absorbing cushion for the tube and is securely riveted to the base eliminating all microphonic noises and protecting the tube against damage from vibration. Furthermore, EBY Cushion Sockets, which are now ready for delivery, fit all standard tubes including the new UX. Here is the socket that many of the Manufacturers, jobbers and dealers foremost manufacturers and set write for complete information buil -'ers depend on for 100% tube efficiency and protection. You can get H. H. EBY MFG. COMPANY them at most good dealers 60c 4710 Stenton Ave., Philadelphia, Pa. for each Makers of EBY Quality Binding Posts

apparatus advertised in this magazine has been All tested and approved by POPULAR RABID LABORATORY

www.americanradiohistory.com 78 The Best in Radio Equipment

THE TUBE WITH A SENSIBLE GUARANTEE QUAM b ff L

< ; Condensers- \\VV\0 with the Pyrex end plate are !' lowest loss and )0+ highest quality. Used as labora- tory standard in Depeility all parts of the Içijj world. Out- are the factors which made Supertron standing fea- tures include:- the foremost Tube in c/lmcrica I I 1 1 %" leakage paths on Pyrex end plate. 2 to The Public buy and enjoy because Supertrons they I helical gears for sharp tuning. are assured of satisfaction a No back by serial numbered guar- lash. Brass antee on each tube for their protection -at their own frame with brass plates soldered price; the public demand price -two dollars. in place. Furnished straight -line wavelength The best dealers sell Supertrons because they give and straight -line frequency. Quam condens- the most satisfaction; the best profit and a permanent ers will improve your set. $6 and up. With good will. 360 degree bakelite dial, add $1. The jobbers who practice their purposes sincerely carry Supertrons to serve their dealers better because Quam audio transformers for better am- Supertron facts are beyond dispute. plification -$S. Backed by a rigid policy; substantial organization and dean merchandising. QUAM RADIO CORPORATION 1925 ALL $ .00 EACH S. Western Ave., Chicago, Ill. Canada S2.75 TYPES + DISTRIBUTORS C. E. Niehoff & Co. Chicago KORACH Fireside Radio Set Co. Chicago Yahr & Lange Milwaukee Tuned Loop The Roycraft Co. Minneapolis Multiple Switch Board Tuner Hippee- States Auto Sup.....Des Moines Sorenson Lamp Co Des Moines Directional Orr Bros Cedar Rapids Base Compass for Radio Dealers Sup. Co, San Francisco Logging Franklin Electric Supply Co.Philadelphia Collapsible Keystone Radio Dist. Co.... Philadelphia Swanson Electric Co Evansville M. H. Johnson Electric Co Utica Hinsdlll Electric Co.. Troy Iroquois Sales Co. Buffalo Hamburg Bros Pittsburgh For those who demand Radio Stores, Inc... Denver Reynolds Radio Co Denver Burr - Fowler Syracuse Superior Results American Radio & Supply Co. . Cincinnati Ed. J. Goetz Co Cincinnati Elgin Radio Corp Elgin Turner Lippee Co Newark, N. J. Leads the march toward perfect radio reception Herbrick- Lawrence Nashville under all conditions. Not Banner Accessories Co. St. Louis merely a "loop" but Witte Hardware Co St. Louis an ingenuous arrangement of mechanical skill de- J. W. Jenkins Sons Music Co. Kansas City E. S. Cowie Electric Co. Kansas City signed for superior results. L. M. Cockaday, using Specialty Service Brooklyn this loop, reached out across the Atlantic G. J. Seedman Brooklyn to audibly Hermann- Brownlow.... Springfield, Mo. hear many trans- continental Stations. Hillman's Inc. Augusta. Me. Alberta Radio Co ...... Alberta, Canada Selectivity Plus Distance Imperial Radio Co.. Sault Ste. Marie, Can. F. X. Gulllevin Montreal, Can. unheard of with common loop aerials. The Korach BRANCH OFFICES excels on all sets designed for loop reception. ATLANTA MINNEAPOLIS OMAHA, NEB. Priced at $16 50 and for sale by all good dealers. DALLAS KANSAS CITY LOS ANGELES Full particulars for PHILADELPHIA DENVER PORTLAND sent 2c stamp and name of PITTSBURGH BUFFALO TOLEDO local dealer. CHICAGO BOSTON ST. LOUIS DETROIT KORACH RADIO CO. SUPERTRON MFG. CO., Inc. 20 E. JACKSON BLVD. Dept. 10 CHICAGO, ILL. HOBOKEN, NEW JERSEY Dealers and Jobbers: Write today for attractive proposition Export Department 220 Broadway, N. Y. C...... SUPERTRON. THE KORACH JUNIOR A modification of the A S E R I A L N U M B E R GUARANTEE "Senior" but possessing all its important features - - - $12.50 advertised All apparatus in this maggAine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipn:ent 79

Tested Parts All parts offered in our Our Latest 1926 Blueprints catalog including those combined in knock- Complete BLUE- down KITS have been PRINTS and easy -to- carefully tested and ap- understand IN- FREE STRUCTION BOOK proved by our gradu- ate Radio Engineers. included with each of Satisfactory results RADIO CATALOG our KITS. No techni- are guaranteed. cal knowledge required BEFORE you build be sure to to build your own set. consult our latest 100 page radio catalog. A dependable guide for set -builders. Knock -down sets and Save Money kits for all the latest circuits. No finer Our enormous buying Panels for Kits or more complete assortment to be power permits us to found anywhere. Latest designed pay spot cash and get A completely drilled parts. And the prices every one rock- bottom prices. and engraved panel - Be quoted means a big saving for you! sure to see our catalog is included with each before you buy - save of our kits. Makes set Write for money. building easy and sure. Write for your FREE your free copy today. copy today! CHICAGO SALVAGE STOCK STORES 509 South State Street CHICAGO, U. S. A. Dept. PR6

Write for Your -- DTs° FREE Copy Today!

All alobaratus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 80 The Best in Radio Equipmen4 Real Fine Tuning! RASLA JUST consider the prestige of the Rasta name, the fame of John Clyde Davidson, Rasla chief engineer. Both are behind the - LYNE Rasla Strate -Lyne. That's why the Strate - STRATE Lyne is a better condenser, a condenser that Straight Line Frequency Condenser really separates stations. The RASLA STRATE -LYNE is built to stand- ards usually adhered to only for laboratory `N1V1\1n\unuun11r,1\Irur. precision instruments. The plates are heavier than on any other condenser, the spacing and alignment is more accurate. Split bushings are provided at both ends. The plates are acid dipped," the end plates nickelled and highly polished. f1 \11,. Transparent bakelite in- a sures true low loss.

111111I1111111111i1111111\1111\\\1\1

:__ - ! ----° 5T11ÄTE -ttYPt The Rasla Fixed Detector is sensi- ßASlt1 ,,...1rt I r, tive-and remains so. Best for re- 1 flex or any circuit. At yol:r dealer's $1.25. LIST PRICES .00035 . . . FREE -Write for the complete Rasta hook-up .00025 . . . 3.1.60 $5.00 .0003 . . 4.75 .0005 5 .25 ,.lu1 Davidson Radio Corp., 222 Fulton St., N.Y. At your dealer's or direct if he can't supply you

Fit for the home of a king - built for the home of AD moderate means. $60 Receiver for $zs

The Gold Medal 5 -tube tuned radio frequency receiver "that stormed the ,,J4% country !" Manufactured to sell at $60, y',. now $25. 7" x 18" Solid Distance, volume, and good tone Mahogany Cabinet quality. Guaranteed to operate or money refunded. Send $25 ONLY by money -order or certified check and this fine receiver will be sent express prepaid. Tubes, batteries and speaker extra. EUREKA OUTLET CORP. X25 1038 Longwood Ave. New York City

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment g 1 The Book To Go By -When You Go To BUY!

The Biggest and most complete included: Sets, radio guide book parts, equipment, published. Com- apparatus, cabinets piled by experts-- - of every descrip- 96 pages crammed tion: 1 tube sets to full of exceptional the finest, multi - radio values and tube outfits. Your Interesting data for radio library is not radio enthusiasts. complete until you From first to last have this book. page, it's an illus- Write for your copy trated review of the today-NOW. It's newest and finest in FREE! A postal radio. Everything brings it.

Cockadays FACTORY BUILT LC-26 Recevev

Another COCKADAY winner and The House of WRS Is now ready to serve Cockaday Fans by IMMEDIATE DELIVERY on all parts used in this circuit. Our customary iron- bound satisfaction guarantee is part of every sale! FACTORY BUILT-MMs EXACTLY AS USED BY MR. COCKADAY 1 General Radio Variometer, type 269, equipped LC -26 This set is a FACTORY BUILT with rheostat knob RECEIVER! Built by the most 1 General Radio Rheostat, type 214-a, 7 ohms, PRICE KITS capable, expert radio techni- equipped with rheostat knob 1 Precision Octaform coil set Immediate cians. Every major part enter- 1 Amsco special double unit condenser No. 1814, Delivery ing into its construction con- each section .0003 mfd. An entire page is forms exactly to Mr. Laurence 1 Micamold fixed condenser, .00015 mfd. 7750 1 Micamold fixed condenser, .00025 mfd. devoted exclu- Cockaday's laboratory model. 2 Daven resisto-couplers (new type which in- sively to this The receiver is completely corporated 1 mfd. condenser concealed in as- base) new circuit to sembled -ready to use! 1 AmerTran DeLuxe transformer, first stage flash across the 1 Bradleyleak h. to 10 meg. Every receiver is 3 Bradleyunits iá megohm radio horizon. Your Guarantee 1 Bradleyunit y megohm thoroughly in- You will find 3 Amperites No. la spected and sub- complete general A COCKADAY CIRCUIT 1 Amperite No. 112 5 Benjamin standard "Cle -ra -tone' sockets jected to a rigid and technical de- SOLD BY THE 1 Carter single- circuit jack, No. 101 test and must tails about it. 2 Carter Jack switches, No. 2 meet high stand- HOUSE OF WRS! 8 Eby binding posts WRITE FOR 1 Fynur vernier control knob and dial ards before leav- YOUR COPY 1 Universal decorated panel, 8 x 22 inches ing the factory! NOW!

WE ARE Voammarlund HEADQUARTERS FOR ALL berts Standard Kits B -T Counterphase RECEIVER New Silver Marshall THE SEASON'S SENSATION! Orig- 8ö«ó! inated and endorsed by 10 of the fore- McLaughlin most radio engineers! Superhet All Specified Parts In Stock Described in full detail in our Completely described in our catalog. catalog. A postal brings you Write for a copy now-it's the book to your copy. Costs you noth- go by, when you go to _ buy! ing I WHOLESALE RADIO SERVICE CO. Dept. 1025 6 Church St., N. Y. Cv ElEICETTIM 0 a 1 CIC1C-11:J[=7f 7 DOTE]

All aPParatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 82 The Best in Radio Equipment

First in the Field 03 Ave. sing in Atkins Cockaday Kite S. HAMMER RADIO CO.,., Brooklyn, New York Cockaday Sets Now Made Easier to Build by Our New "Ready -to -Wire" (Plan 50% of Your Time, Work and Worry SAVED ! All you need do is to connect bus -bar according to diagram, solder and your set is finished. These Kits are sent to you completely mounted, and assembled on a Veneered Mahogany baseboard and genuine bakelite panel, drilled and engraved; in a solid Mahogany Cabinet. Genuine parts used as listed below; exactly as used in Mr. Cockaday's Laboratory Model. COMPARE OUR OFFER! TUBE NEW SINGLE DIAL CONTROL Cockaday's New LC -26 Receiver

1 General Radio Variometer 3 Bradleyunit . ', megohm... $2.25 8 1 Bradlevunit ', megohm.... 75 SUPERHETERODYNE type 269 with rheostat knob $5.30 .3 Amperites No. la 3 30 1. 10 2 Precise No. 750 Syncrodensers I N. Y. Coil fixed condenser 1 General Radio Rheostat type 1 Ainperite No.112

- 75 .0005 $9 00 .006...... $ 214 -a, 7 ohms, with rheo- 5 Benjamin standard "Cle -ra- 5 00 1 Precke N. 744 Coupler .60 1 N V. ( oil fixed c.,mn -er stat knob...... 2.25 tone" sockets... 2 Precie Aluminum Brackets l,r.2 00 .00025. 35 1 Precision Octaform coil set 5.50 1 Carter single- circuit jack 1 Preci-tilli.riumcter 8.00 Wire, scrrtt f In Genuine Mahogany 80 00 6 WIRED COMPLETE Specified Cabinet V READY-TO -WIRE KIT, PRICE, . $101. UNASSEMBLED KITS IN STOCK WIRED COMPLETE hogany Cabinet . $115.(° UNASSEMBLED KITS IN STOCK HAMMARLUND ROBERTS, D. T. W. LOOP IN STOCK KITS IN STOCK WRITE FOR BOOKLET about these Parts and Kits. Also for Free Radio Catalog; Transportation Prepaid. One -third must accompany all C. O. D. orders. Not insured unless insurance charges included

Cockaday "B" BROADCAST LISTENERS The POPULAR RADIO ATLAS and LOG will give you a list of all the NEW Broad- Eliminator casting Stations with wavelengths and other necessary information (Raytheon Plate Supply Unit) A Complete Atlas and Station Log ob- The "POPULAR RADIO International Radio Atlas and Log" .\ really dependable method for will supply you with full information regarding broadcasting taining a "B" source of supply from stations of the United States and Canada. This most useful and practical Atlas consists of r6 pages, the electric light wires in your home. size 12'X 15', printed on good paper. from dear type in two Humless life (over 10,000 ho !its colors and contains a complete series of double page maps, in- -long cluding -The World -The United States- Canada -North and on tests). Parts for the Cockaday South America, showing location of principal broadcasting, leading "B" Battery Eliminator may he ob- commercial and governmental radio stations. tained exactly as described in No- SPECIAL FREE OFFER RADIO Price You may have a copy of the "POPULAR RADIO International vember POPULAR - Radio Atlas and Log" free, with POPULAR RADIO for (8) eight $12.05. months For Only $2.00 Pin $2.00 in bills to the coupon below. If you are a subscriber to either POPULAR RADIO or The Wireless A Substitute for Age, your subscription will be extended eight months. POPULAR RADIO a Loop Aerial 627 West 43d Street New York City Date. Now you can build the McLa'lghlin PoPrrt.AR RAmo. Dept. 12A 8 -tube One Control Receiver without 627 %l'est 43d St., New York City. use a loop aerial. The Pre- Enclosed is my remittance of $2.00 for which you are to enter my sub- having to scription (extend my subscription) for (8) eight months for POPULAR cision Antenna Coupler makes your RA,no and send FREE a copy of the "POPULAR RADIO International ORDER outdoor aerial serve just as well. Radio Atlas and Log." FROM US Name TODAY Price $3.50. Address PRECISION COIL CO., Inc. City State ...... 209 Centre Street New York, N. Y. All apparatus advertised in this.magazine has been tes.ed and approved by.POPULAR RADIO LABORATOR1

www.americanradiohistory.com The Best in Radio ûquipment 83

To our old friends of Popular Radio a little "tip' [ i Cabinet Model L $35.00 j have probably seen a dozen slow pokes but it's taken us exactly yoUloud- speaker advertisements in the 5 years, thousands on thousands of last month. Horns, cones, what not. dollars and 256 experimental models to You've read all sorts of claims. make it right -to give exact reproduc- Now just between us -as old timers, tion of the human voice and all musical here's a tip. instruments. Frankly, it relates. to Acme, but you Perhaps we need scarcely tell you what don't care do you, as long as you get you can expect from speakers hastily what you're looking for? conceived and hastily manufactured. Well to make it quick. Acme has a If it has taken us 5 years with all our new "double free -edge cone" loud experience specializing on "amplifica- speaker. We have no reputation as tion without distortion" what must be the answer? So hear the new Acme -we know you'll know. Meanwhile, if you haven't already a copy, be sure to send for the new 10th Edition of "Amplification without Dis- tortion."

CLAUDE F. CAIRNS Pres. Acme Apparatus Co. Send for your copy

-OWN ® .o ® APPARATUS COMPANY, Acme "double free -edge ACME cone" Loud Speaker - Dept. C7, Cambridge, Mass. Round Model, $25.00 Enclosed find ten cents (etamps or coin) for my copy of the new 10th Edition of "Amplification without Distortion." ACME Name -for amplification Street City State

has been tested and approved by POPULAR RADIO LABORATORY All abbaralus advertised in this magazine

www.americanradiohistory.com 84 The Best in Radio Equipment

For CORBETT' For Quality A B I NETS Quality

CABINET For LC -26 Receiver Built exactly to specifications with piano hinge, lid stay, and splined mounting board. List prices: YOUR L. C. 26 Receiver will be easier to GENUINE AMERICAN WALNUT... $17.00 build Ind look better if you use these GENUINE MAHOGANY 17.00 Special Alloy Brackets. Approved MAHOGANY OR WALNUT FINISH 14.50 by Popu- lar Radio Laboratory. Made especially for the New Popular Radio Standard Cabinet described in the December issue of Popular Radio. Sent postpaid anywhere in the world upon receipt of price. Your dealer will carry them if you ask him. Mail order houses carry them or order direct. Price, $2.00 per pair Made to save you time and trouble TAIT, 161st Street and Brook Ave. New York City Simplified Blueprints LAURENCE M. COCKADAY has personally super- vised the preparation of Simplified Blueprints of eight of POPULAR RADIO'S most popular circuits. Each set consists of three or more Actual Size Blueprints; first a Panel Pattern; second, an Instrument Layout; and third, a Picture Wiring Diagram all simplified in McLaughlin the fullest sense of the word. Priced at $1.00 per Set Super- Heterodyne Set No. 4- "Cockaday 4- Circuit Tuner with Resistance- To specifications in October. 1925, issue with piano hinge Coupled Amplifier" (five tubes, distortionless, two dials, and lid stay. automatic vacuum tube control, as described in the October List prices: 1924 issue of POPULAR RADIO). GENUINE AMERICAN WALNUT. $12.00 Set No. 6 -"The Cockaday 8 -Tube Super -heterodyne Reflex GENUINE MAHOGANY 12.00 Receiver" (eight tubes, two tuning dials, loop, non -radiating, MAHOGANY FINISH 9.60 distortionless, as described in January 1925 issue of POPULAR RADIO). Standard Cabinets in Stock (Specify model "T. ") Set No. 7 Craig Of the same -"The 4-Tube Reflex Receiver with the New design as the McLaughlin cabinet above ex- Sodion Detector" (four tubes, two tuning dials, cept having rabbetted instead of grooved front. Piano non short antenna, hinge and lid stay. -radiating as described in February 1925 issue of POPULAR RADIO) . Mahog- Walnut Mahog- Walnut Mahog- Walnut Set No. 9- "Portable Town and Country any or Ma- any or Ma- any or Ma- Receiver" (six tubes, Size finish hogany Size finish hogany Size three stages of transformer coupled radio-frequency 7x18 -8 $8.65 finish hogany ampli- $9.60 7x28 -8 $11.80 $14.70 7x21 -10 $10.90 fication, loop antenna, 7x21 -8 9.30 11.60 7x.10 -8 $13.26 tuned by variable condenser as de- 12.75 16.86 7x24 -10 11.70 14.65 scribed 7x24 -8 10.10 12.60 8x30 -8 13.70 17.10 7x26 in May 1925 issue of POPULAR RADIO). 7x26 -8 10.70 13.35 -10 12.65 16.80 7x18 -10 10.20 11.55 7x..0 -10 13.30 16.65 Set No. 11-"5-Tube Tuned Radio -Frequency SPECIAL Receiver with CABINETS TO ORDER Simplified Control" (as described in August 1925 issue of SHIPPING CHARGES POPULAR RI.DIO). PREPAID Set No. 12 -"8 -Tube Super CORBETT'S CABINETS -heterodyne with Single Control" have been preferred for (as described in October 1925 issue of POPULAR several years by quality set builders and are unquestionably Set No. 13- "Raytheon RADIO). superior in design and Plate Supply Unit" (a really depend- finish. They are backed by our able method for obtaining a "B" source of supply guarantee to please you. Carefully hand rubbed piano scribed in November as de- Well packed for shipment. finish. 1925 issue of POPULAR RADIO). Set No. 14 -"The LC-26 Broadcast Receiver" (as described in WRITE FOR CATALOG showing attractive models for December 1925 issue of POPULAR RADIO). all sizes of radio cabinets, consoles and tables. Full constructional and parts details for these Receiving Sets Jobbers and will be Dealers write for discounts. Back ssuesnof POPULAR eRADIO rate Pwil beRfurnished l at the CORBETT CABINET MFG. COMPANY of 35c a copy. St. Marys, Penna. POPULAR RADIO Department 14 627 West 43d Street, New York

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 85 The Best in Radio Equipment eye it A msco No. 1814 -a siam. ese pair,each.00032 mfd. for the single control. L. C. -26 Receiver. Described in the Decem ber issue of POPULAR RADIO.

AMSCO 14 Plate Special for the single control radio receiver designed by L. M. Cockaday. This condenser is exactly right for the "L. C. -26" circuit-each unit being electrically paired for straight line capacity and mechanically matched for synchronization. It is practi- cally zero loss-with a minimum cap acity that admits of tuning in the low wave bands you can't afford to miss. You will find it free of body capacity effects-and absolutely noiseless during adjustment. Ask your dealer for Amsco No. 1814 Special. If you can't get it, write us, at Dept. D AMSCO PRODUCTS Broome and Lafayette Streets New York City Write for interesting booklet The Heart of The Hook -up"

111 apparatus advertised in this magasine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 86 The Best in Radio Equipment McLaughlin uses PRECISE

PRECISE SYNCRODENSER .0005 mfd $1.50 .00035 mfd $4.00 (with or without lug) Do You Know? `THAT Precise Syncrodensers are the ORIGI- NAL and ONLY straight - line frequency condensers combining straight -line capacity at the higher end thus assuring uniform station separation. DO YOU KNOW that Precise Syncrodensers will make your receiver easier to tune, due to the characteristics of design and construction. Select Precise when building your receiver and be assured of maximum tuning efficiency regardless of what type of set you are constructing. They are rigid and compact and can be mounted either on panel or sub -panel requiring a minimum of space. Ask your dealer to show you the PRECISE line, or write for literature. PRECISE MFG. CORP. ROCHESTER, NEW' YORK Branch Offices: 126 Liberty St., New York City 454 Builders' Exchange, Minneapolis, zo5 West Harrison St.. Chicago, III. 5127 Pine St., Minn. 821 Market St., San Francisco. St. Louis, Mo. Cal. 701 A. O. U. W. Bldg., Little Rock, Ark. Canadian Distributors: PERKINS ELECTRIC, Ltd., Toronto, Montreal, Winnipeg

PRECISE PRECISE PRECISE No. 480 No. 285 Transformer. Comet Transformer. Sugersize PRECISE Audio Filtoformer. Ratio 411 to 1. Ratio 312 to 1. Transformers. Price, $5.00 Ratios 5 to 1, 21,2' to I. Price, $4.50 Price, $3.25 Price, $7.50 each

Every Precise Instrument Is a Laboratory Product

All apparatus advertised in this magazine has been Tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 87

An overnight charge with a Tungar costs about a nickel. It peps up both "A" and "B" batteries and keeps your radio set at its full -toned best. Tungar - the original bulb charger - is noise- less. It contains no substance which will spoil furnishings. Just clip it to your set and plug it into the house current. It can't blow out Radio - trons if the battery is left hooked to the set while charging. Use a Tungar -the charger that needs no attention.

The Tungar is a G -E product, developed in the Research Labora- tories of General Elec- tric. unøarREG. U.S. PAT. OFF. The new Tungar char- ges any make and size CHARGER of storage battery : ra- BATTERY did "A" and auto bat- teries, and `'B" batter - NW/ ies'as high as 96 volts in series. Tungar -a registered trademark -is found only East of Rockies on the genuine. Look for it on the name plate. Two ampere size $18.00 Five ampere size $28.00 Merchandise Division 60 cycles . . 110 volts General Electric Company, Bridgeport, Conn. GENERAL ELECT 7

apparatus advertised-in this'-magazine has-bed'!3'tó9ted flfl wild POPULAR " R ADIO 'LABORATORY

www.americanradiohistory.com 88 The Best in Radio Equipment

The World's Largest Exclusive Radio Mail Order House Will Send You This Wonderful Book FREE 64 illustrated pages containing thousands of bargains in radio sets, semi -finished sets and radio all kits of styles, sizes and approved circuits. 5 -tube sets as low as $29.50. Beautiful ceivof the very latest designs and models cabinets types. Elaborate console models with loudspeakers built ing genuine mahogany and guaranteed. e. lsog g in radio supplies, chargers, speakers, transformers, condensers, rheostats and any other partsici teries loud your set or building a new one. you may want for improving Guaranteed saving to you of y toy . The Biggest 5 -Tube Value on the Market Positively the world's greatest 5 -tube $75.00 radio bargains. Regular value. Our large quantity production enables us to sell this set for only $29.50, fully built and wired in beautiful mahogany cabinet of latest design with sloping handsomely Bakelite panel of Satin finish, etched and engraved as illustrated. Constructed of the finest low-loss condensers, coils and sockets. Bakelite baseboard panel and dials. Price for set only. $2 Transportation charges extra, shipping weight 25 lbs. This set with all accessories, including the Bell loud speaker with adjustable famous American one guaranteed unit, 2-45 volt "B" batteries, connection, 100 Ampere Hour, storage "A" battery, cable for battery 5 -20M tubes, Aerial and ground equipment, thing complete ready to set up and every- else to buy. and operate. Nothing @ Transportation Price&A W5975 charges extra. Shipping weight 100 lbs. Order Direct from This Page! Save About ; Order direct from this page. Save One- Write your order and '/3 to r/2. Our guarantee protects you. Money prices plainly. Send post office money order cheerfully refunded if you are not satisfied. Commercial agency regarding our reliability. or bank draft for full amount to insure safety.Ì Refer to any bank or SEMI- FINISHED 5 -TUBE RADIO FREQUENCY SET SEMI- FINISHED 8 -TUBE SUPER -HETERODYNE

s1875 $4375

World's Famous offer 8 -tube reception on ud speakerd.inLow Coast superheterodyne. Complete Parts for Best Highest quality transformers. loss condense and tsockets Fully mounted on panel and 45 Kilocycle cealed under Bakelite rheostats. All wiring con- baseboard. Comes Super -Het. Bakelite baseboard. 7x18 panel -fits into any standard complete- erodyne Genuine Remler cabinet. Complete operating. Guaranteed ly assembled ready to wire Parts you o 5.00.Prceof set all and operate. We have t of same model as American $18.75. Caine testi- Radynola pictured above $5.65 extra. monials from thousands of $495° builders of this set. Some You must have our catalog no matter what have received want. Our line is set or kit you foreign stations complete and includes all popular sets, such on loop as Superheterodyne, Neutrodyne, Ultradyne, Reinartz, loss straight lline Low- erative, Radio Frequency, Regen- frequency condensers, vernier dials, finest Browning- Drake, Super -Heterodyne quality rheostats. Matched Columbia, Reflex and all other latest circuits. Kits, sets and Requires long waved transfor- factured by all well known manufacturers parts manu- only for attaching Baldwin, Brandes, Western such as Frost, Howard, d and set is ready to operate. Electric, Columbia ebaseboa Our and others. of set only $43.75. Price dyrwirnDo Requires following accessories to complete Rememberbaar -we ahfoeigenoltsentfooclo are the largest t falo ndr our catalog. inet,8- 201Atubes for this set: 7x30cab- exclusive radio mail order dealers In storage battery operation or No.199 the world and carry the best of everything in radio. We for dry cell operation. 100 tubes 3á toy on the following save you Ampere hour storage battery, kits. Detailed descriptions appear in our "B" batteries, loud speaker, center 2-45V catalog. items are listed tapped loop aerial. All thesp in our catalog at a tremendous saving. Catalog includes NEUTRODYNE COCKADAY Genuine FOUR Complete Parts list of broadcast- kit of ts, coomeefully 3-tube assemb kit of TUBE BROWNING for Coc' a - assembled parts, fully assbmeled DRAKE AND and Resistance Coupled ing stations, on the panel and baseboard with on COCKADAY'S complete and baseboard, NEW LC 26 and 5 -tube set at prices general radio in- instructions, panel o wire CIRCUIT PARTS formation and ready to wire. Price, $29 75 Price. $15 85 ARE IN OUR CATALOG. that will astoLnd you. Also facts about our templets pais for AC Kit. tree service divis- ion. Write for it RANDOLPH RADIO CORPORATION today. 159 N. Union Ave. Dept. 225 Chicago, Illinois 1 All apparatus advertised in this magazine has been tested and approved by POPÙLAR RADIO LABORATORY

www.americanradiohistory.com The Best in Radio Equipment 89

977-e Neu' CULIGUM TUBE _ _ RADIO ______,_.__ --1-r"_ The New McCullough AC Tube is now being manufactured, for the McCullough Sales Co., by KELLOGG SWITCHBOARD & SUPPLY COMPANY, CHICAGO. An assurance of standard of quality and uniformity -and of sufficient production to meet the tremendous nation -wide demand for this greatest -of -all advances in Radio develop- ment. An ALTERNATING C RRENT Tube, operated by simply plugging into the AC lighting socket (through small step -down transformer). Developed to perfec- tion -the fulfillment of radio's long felt and greatest The Tube That requirement. A Tube with greater electron emission and increased Eliminates signal response. A Tube of more rugged construction and LONGER LIFE. "A" Batteries List Price $ 6 RADIO SET MANUFACTURERS AND JOBBERS OF RADIO TUBES ARE from Radio URGED TO GET IN LINE WITH THIS IMPORTANT DEVELOPMENT Tubes Ready for Prompt Delivery McCULLOUGH SALES CO. Distributors McCullough AC Tubes PITTSBURGH, PA., 963 Liberty Avenue NEW YORK, 25 W. Broadway CHICAGO, 533 Wabash Avenue

_ill apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com 90 The Best it Raatu Equipment

4 The Heart of the Bradley - Amplifier

The Bradley -Amplifier is equipped with sockets that will accommodate the new UX tubes as well as the old tubes. No adapters are required for using ar.y type of UX tube. Retail Price in U. S. A. - $15.00 Retail Price in Canada . $21.00 MUCKED away within the pol- ished bakelite base of the Bradley -Am- plifier are six incon- spicuous, solid mold- ed resistance units known as Bradley - Surprise Your Friends units. The Bradleyunit is With The Improved Tone Quality of Your Set the heart of the T IS Bradley - Amplifier NOT ENOUGH that a good radio receiver is selective or is because it alone can able to bring in distant stations. Quality of reproduction amplify is now considered the incom- as important as selectivity and sensitivity. ing tone frequencies Fortunately, without the tone quality of your radio set can be quickly distortion. proved and im- It replaces the ordi- perfected without disturbing the existing wiring of the set. All that is necessary nary bulky audio - is to replace your present audio - transformer amplifier with a Bradley- Amplifier. frequency trans- This compact former unit employs no transformers and amplifies all tone frequencies and elimi- with faithfulness and clarity, and without distortion. nates the most frequent cause of It is a mark of distinction to bave a radio receiver of fine tone distortion in a radio quality and you will surprise your friends with the remarkable receiver. The Brad - improvement in your set that follows the use of a Bradley -Am- leyunit cannot de- plifier. It is as easy to install as a B- Battery and usually can be teriorate or change installed within the receiver cabinet. with age. Be sure to try one, tonight. oAsk Your Nearest Radio Dealer for a ALLEN- BRADLEY CO. 276 Greenfield Ave. Milwaukee, Wiscdnsin Please send me, by return mail, litera =.ire 13 on the new Bradley -Amplifier. Resistance - Coupled Name PERFECT AUDIO AMPLIFIER Address 4

All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

www.americanradiohistory.com ¶1'bese wonciellúl new tubes are matched -every one must pass an exacting test for uniformity as well as the supreme quality which has made Gold Seal Tubes famous. Put a full set of these wonder tubes in your radio and enjoy a revela- tion in receptiori- clear, rich tones, full resonant volume, and thrilling dis- tance. They cost no more -yet the life of Gold Seal ¡Pubes is two times that of or dinary tubes, by actual test. Gold Seal Products Co. 250 Park Avenue, - New York City

NOTE : If not obtainable from your local dealer, write direct to us. GOLD SEAL Radio githe.,

13everywhere 2 50

www.americanradiohistory.com The new C -H Socket for

In jadio especially "it's the little things that count" WHEN your radio set goes wrong, just as you are comfortably settled before the fireplace ex- A list of some of the pecting prominent radio manu- to spend a great evening, it is annoying. facturers using C -H products And ten to one, it's only some little wire or part Acme Apparatus Co. that in itself is insignificant. Really, though, there's American Bosch Magneto Co. no excuse for such things happening. Astral Radio Corp. Boissier Radio Corp. GOOD parts of good material and carefully built Chelsea Radio Co. Crosley Radio Corp are insurance against such annoyances. Dayton Fan & Motor Co. While C -H Rheostats are DubilierCondenser& Radio built to engineers' speci Corp. Cutler-Hammer radio products are GOOD parts. ca- Electraa Inc. Both tions, they are designed for Freed -Eisemann Radio amateur builder and set manufacturer can attest the use of the novice. They Corp that fact. are are built as a unit and are not Garod Corporation They designed by radio control experts, dismantled for mounting. Gilflllan Bros., Inc. backed by 25 Howard Radio Co. years' experience, built of the highest The closely wound, fine re- Allen T. Hamscomb quality material and sold a sistance wire is prevented The Keyport Laboratories at price you are glad to pay. from slipping or wearing King Electric Mfg. Co. out true by a bronze LeMor Radio, Inc. Whether you buy or build, insist on C -H radio of Magnus Electric & Radio spring. Thus smooth, quiet Co. parts, for it's these good little parts that count and control is assured either ad- Malone - Lemmon Labora- vancing or decreasing the tories assure constant, efficient service from your set. potential. Wm. J. Murdock Newport Radio Co. There is no jumping, no The Radio Compak Co. THE CUTLER back lash; and no sticking. R. B. Radio Co. -HAMMER MFG. CO. .Robbins Rodio Co. Member Radio Section, Associated Manufacturers of Only one hole for mount- Simplex Radio Co. Electrical Supplies ing. Self-centering in over- R. E. Thompson Co., loo. size holes and adjustable to Workrite Mfg. Co. Milwaukee, Wisconsin any panel thickness. CUTLER - HAMMER Radio Parts I3r Performance]

www.americanradiohistory.com '