September, 1924 25 Cents

SEPTEMBER, 1924 25 CENTS

RAD (Keg. U. S. Put. Off.)

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RADIO TUBES GHAM AMPLIFIER 0299 TED Bring World Events to Far- Distant Vacation Lands

D 4CK- COUNTRY isolation melts into world contact as you tune -in on music, D drama, and the final battles of the Presidential Campaign. CUNNINGHAM TUBE PRICES Make your camp, your cottage, your yacht the center of hospitality and enter- C- 301A -5 Volts 3 Ampere filament $4.00 tainment. C -299 -3 Volts .06 amp. Dry Battery Det. and Perfected Radio will Amp $4.00 do it, and Perfected Radio means the use of Cunningham C -300 -5 Volts Gas Con- Radio Tubes. The Cunningham dry battery detector and amplifier tube, tent Detector $4.00 C- I1 -1.1 Volts .25 amp. type C -299, makes it possible for you to treble your vacation pleasure by use Dry Battery Det. and of a portable receiving set. The special filament in this tube, using a current Amp. Special Base . $4.00 C- 12- Similar to C -I1 with so low that it may receive its supply from standard No. 6 standard dry batteries or even base $4.00 from ordinary flashlight batteries, makes possible this far -reaching application PATENT NOTICE of Radio. Cunningham tubes are covered by patents dated 2- 18-08, 2- 18-12, 12-30-13, The receiving set you now have can be readily adjusted to use this tube and 10- 23.17, 10- 23-17, and be a source of use others issued and pending. and pleasure on your vacation trip. Your dealer can give Licensed only for amateur, you useful suggestions for the purchase or construction of a highly efficient experimental and entertainment use in radio com- portable set. munication. Any other use will be an infringement. DATA BOOK Cunningham 40-page Data Book fully explaining care and operation of Radio Tubes now available by sending 10c in stamps to Branch Branch San Francisco office. CHICAGO 182 Second Street, San Francisco NEW YORK

www.americanradiohistory.com Orl/tiLetilit Cotto Tone t Headset

TOWER'S GIFT TO THE WORLD! Reproduction of All Radio in Cello -tones

40) For years Frank S. Tower played the cello, the richest -toned instrument in the world, giving concerts and recitals throughout Europe and America. With the soft, sweet "cello- tone" clearly in mind, he has successfully manufactured the TOWER'S scientific headset, which accurately reproduces all radio in the same liquid tones.

TOWER'S scientific, lightest of all in weight, offers higher resistance, with elimination of distortion. Longer cord (full 5 ft.). Every set tested and approved by licensed radio operators. Every set covered with our money - back guarantee. Order today by post card and we will ship immediately by Parcel Post C. O. D. Our $200,000.00 company stands squarely back of every headset.

TIIETOWUZIMG. CO. 98 Dept. E Brookline Ave., Boston, Mass.

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www.americanradiohistory.com Forecast of Contributions RADIO for October Issue Established 1917 cv.9 Published Monthly by the Pacific Radio Publishing Co. G. M. Best will have two articles in addition to his "Queries and Replies" which are ARTHUR H. HALLORAN, Editor universally recognized as containing reliable LAWRENCE MOTT, GERALD M. BEST H. W. DICKOW Associate Editor Technical Adviser Advertising Manager information. One article will deal with the construction of a two -stage choke coil amplifier Branch Offices: Correct Addresses: set costing less than $40.00 and giving distortion - New York City -r7 West 42nd St. Instructions for change of address should be less reception at Chicago -157 E. Ontario St. sent to the publisher two weeks before the high efficiency. The other will Boston -52 Irving Street. date Kansas they are to go into effect. Both old give the characteristics of audio -frequency City, Mo. -11o2 Republic Bldg. and new addresses must always be given. transformers at various frequencies. Rates: Advertising: Issued Monthly, 25c a copy. Subscription Advertising Forms Close on the First of the 6`N price $2.50 per year in the U. S., $3.00 per Month Preceding year elsewhere. Date of Issue. C. M. Jansky Jr. will continue his valuable Entered as second -class matter at the Post Office at San Francisco, Calif. series of articles on radio communication with Copyright 2924, by the Pacific Radio Publishing Co. some specific application of principles already developed. During the summer months, Prof. Address all communications to Jansky, as assistant consulting radio engineer for Pacific Radio Publishing the Signal Corps, has been devoting his time to Co. research work at Camp Alfred Vail, N. J. Pacific Building, San Francisco, California 6'4%3 VOLUME VI SEPTEMBER, 1924 NUMBER 9 1.41 Constructors of home -made sets will be interested in O. B. Scott's details of the design and construction of the regenerative reflex, as well CONTENTS as in E. F. Kierman's directions for winding duo -spiderweb coils for use in the simplified RADIOTORIAL COMMENT 9 Reinartz circuit.

THE BRASS POUNDERS OF NIPPON 10 By Volney G. Mathison Bernard Steinmetz explains' several methods RADIO- FREQUENCY WITH THE SINGLE -CIRCUIT for obtaining negative potentials for grids of REGENERATIVE RECEIVER 13 By E. E. Griffin vacuum tubes. THE VACUUM TUBE AS A DETECTOR 15 cap By C. M. Jansky, Jr. Jerome Snyder has a helpful article on the AN IMPROVED REINARTZ RECEIVER 17 theory and use of the hot wire ammeter. By Cessf ord Kerr cva IMPEDANCE VALUES OF AUDIO FREQUENCY TRANSFORMERS 19 The transmitting amateur will find some un- By Gerald M. Best usually good suggestions in several articles. F. Dawson Bliley A SINGLE CONTROL REGENERATIVE RECEIVER 20 tells how to get down to the By Paul Oard lower wavelengths now available for amateur A VARIABLE B BATTERY 21 use. L. W. Hatry discusses the design of the By David P. Gibbons reversed feed -back transmitter. M. Wolf de- RADIO CONSTRUCTION POINTERS 23 scribes a simple method for determining per- By Paul Oard centage modulation in radio telephone sets. PROPER CARE OF STORAGE A BATTERIES 24 F. Bowman passes on some good By H. A. Fischer stuff about a successful loose -coupled transmitting circuit. A HOME MADE SYNCHRONOUS RECTIFIER 25 By Geo. Becker, Jr. William Jackson describes an ideal chemical rectifier. A GOOD FILTER FOR THE AMATEUR TRANSMITTER 27 By C. W. Rados SECRETS ON SUCCESSFUL OPERATION OF TRANSMITTING Harry Diamond analyzes the nature of static TUBES 29 and its elimination. By Don C. Wallace ADJUSTING YOUR SUPER -HETERODYNE 30 By L. H. La Montagne Edward W. Smith presents a simple discussion THE SECOND HARMONIC SUPER -HETERODYNE 31 of the essentials of a good audio -transformer and By L. R. Felder circuit arrangement whereby the output can be IMPROVEMENTS IN THE 45,000 -CYCLE SUPER -HETERODYNE 33 improved in quality. THE GRID LEAK 34 cva By H. Bunch A TRANSMITTER THAT SOLVES THE LOCAL Q R M F. L. Ulrich has an interesting article on a PROBLEM 35 short wave DX receiver oscillating as low as By Franklyn S. Huddy 50 meters. DIGEST OF RECENT RADIO PATENTS 36 C4.9 QUERIES AND REPLIES ON C. W. PRACTICE 37 The fiction feature will be "A Royal Hiatus," By Gerald M. Best a story with a hundred chuckles. You will also WITH THE AMATEUR OPERATORS 40 get a good laugh out of "A Jazzed Up History FROM THE RADIO MANUFACTURERS 42 of Radio."

2 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com THE

«1\CHRO PnAS TRADE MARK

BROADCAST Receiver that marks "It is only When the cold in season cornes that we know another long step forward the pine and cypress to be radio design and establishes a new set evergreens." -Confucius of standards in craftsmanship. In the coming cold season literature be not surpassed by thy Write for neigh bor -set the pace with your Grebe Synchrophase. A. H. GREBE & COMPANY, INC. Van Wyck Blvd., Richmond Hill, N.Y. Western Brunch: 451 East 3rd St., Los Angeles, Cal.

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www.americanradiohistory.com 11111111 I I I I I I I I =, I I I 1 11111 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 111 I I I I 1 11111 I I I I 1 L=' `

=Ç= For Long Distance Rec,,...__.__=,_-

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.___-=,.. All Crosley Regenerative Receivers licensed under The Crosley Radio Armstrong U. S. Pat. 0/3.149 Corporation owns and operates Broadcasting Station W L W 111111IIIII111111 ¡¡ II IIIIIll1 1IIIIIIIIII1111 1 111111111 1111111111111 111111 1111111111111111111111111111111 IIIIIIIIIIII11I Better-Cost Less III IIIIIIII IIIIIIIIIII IIII III11111II UII IIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIUIIIIh,. Radio Products Tuned Radio Frequency Receivers

Crosley A two -tube receiver Model VI with a reputation for Crosley Model X -J The famous Crosley long distance with pronounced clearness. It con- four -tube receiver sists of one stage of Crosley tuned radio frequency consisting of one stage of radio frequency ampli- amplification and a detector. This Crosley com- fication, detector and two stages of audio frequency bination multiplies the receiving range amplification. Probably the greatest single feature of the set of this receiver is its remarkable selectivity. It will tune through powerful local broadcasting stations Crosley Super This two -tube receiver and bring in distant stations VI is so coupled up as to clearly and with great combine volume. One of the most popular re- both the Tuned Radio Frequency and ceivers on the market today $55.00 the regenerative detector. Perfect regeneration, control of tuned radio frequency amplification with minimum reradiation and increased range $2 9.00

Crosley Model X -L This beautiful Con - solette Model is an Crosley Type 3 -C This receiver consists addition to any home. It is the same receiver as the of an Armstrong re- Model X -J except as to arrangement of panel and generative detector and two stages of audio fre- the consolette cabinet with its built -in loud speaker quency amplification, making it suitable for long and separate compartment for dry cell "A" distance reception on a loud speaker. (This set does and "B" .....,batteries a..and ....other ac- not contain Tuned Radio Frequency Amplification.) cessories 120.00 It is built in the same style as to cabinet, etc. as the Model X -L described $110.00 A beautiful stand to match this X -L is supplied at It matches perfectlÿ the floor stand described an extra cost of only for $25.00 the Model X -L costing only $25.00 For Sale by Good Dealers Everywhere Write for Complete Catalog THE CROSLEY RADIO CORPORATION POWEL CROSLEY, JR., President 919 Alfred Street Cincinnati, Ohio 10% WEST OF ROCKIES. PRICES QUOTED ARE WITHOUT ACCESSORIES,

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www.americanradiohistory.com Ihé PAUL REVERE o TODAY TWENTY miles in a single night. That was the won - derful broadcasting achievement of Paul Revere as he galloped from village to village, waking the countryside with the cry "the British are coming." Just one -hundred and fifty years ago he made that broadcasting record. Today news flashed in any part of the country is heard almost instantly, not a mere twenty miles but thousands of miles away. In every part of the United States Crosley Radio Receivers are bringing in far distant stations clearly and distinctly. Up to the minute news, concerts, music, lectures, are yours to enjoy right in your home when and from where you choose if you own a Crosley. . Keeping always at the head of the procession in improvements and innovations, the Crosley Radio Corporation has made it possible for every one to possess the maximum efficiency in radio reception at the minimum cost. The Crosley Trirdyn 3R3 illustrated below is, in the opinion of many experts, the best radio receiver ever offered to the public at any price. The experiments of over 200 experts have shown that in ease of tuning, sharpness of signals and nicety of calibration, the Trirdyn cannot be excelled. Local stations may be easily tuned out even if very close to you, and far distant reception almost instantly brought in. incor- ALI Crosley Regenerative Receivers I,censed udp The Trirdyn 3R3 illustrated below is a 3 tube set Armstrong U. S Pot. 1.113,149 porating tuned radio frequency amplification, regeneration and reflex. It has been proven to give the efficiency of a 4 or 5 tube set. And yet it is priced at only $65 without batteries, tubes and headphones. The Trirdyn Special, set in a special solid mahogany cabinet which is made to Better -Cost Less house all the necessary accessories may be had for only $75. Radio Products Before you purchase a radio receiver listen in Tne Crosley Radto Corporation owns and operstesJ on a Crosley Trirdyn. Broodcesang SteSon W L W For Sale by Good Dealers Everywhere

Crosley Trirdyn 3R3 $65.00 Other Crosley Models CROSLEY 50 A one tube Armstrong Regenerative Receiver. Price, less accessories $ I4.00. A two stage amplifier Crosley 50 -A may be added to it for only $18.00 thus making a three tube set. CROSLEY 51 The two tube Armstrong Regenerative set that became the biggest selling receiver in the world in just 24 days. Price, less accessories, $18.50. By adding the Crosley 51 -A a one stage amplifier at $14.00 a three tube set may be formed. CROSLEY 50-P The Crosley 50 in neat strong portable quartered oak cabinet for only $18.00. CROSLEY 51-P The Crosley 51 in compact leatherette portable case completely self containing at $25.00. CROSLEY 52 A new Armstrong Regenerative 3 tube set assuring loud speaker volume on distant stations under almost any conditions. Price. without accessories $30.00. CROSLEY X-J One of the best known and most popular 4 tube receivers on the market. A radio frequency set at $55.00 without accessories. CROSLEY X-L A rearrangement of the 4 -tube Crosley X -J set in a beautiful mahogany console cabinet. Price, without accessories $ I 20.00 MAIL THIS COUPON TODAY The Crosley Radio Corporation, The Crosley Radio Corporation 91 9 Alfred St., Cincinnati, O. Powel Crosley, Jr., President Gentlemen: Please mail me free of charge your complete catalog of instruments and parts together with booklet 919 Alfred St. Cincinnati, O. Crosley entitled "The Simplicity of Radio ". Prices west of the Rockies 10% higher

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www.americanradiohistory.com ow a AGNAVOX Tube

HE engineers who developed the famous Magnavox line of radio reproducing and amplifying equipment have now produced a vacuum tube equally distinctive and successful in its own field. One trial convinces the most exacting user that the Magnavox will replace ordinary tubes to great advantage in any receiving set. Magnavox Products

Reproducers of electro- dynamic Power Amplifiers for audio - and semi -dynamic type, for all frequency amplification, one, vacuum tube receiving sets; two, and three -stage; $25.00 to $50.00 $27.50 to $60.00 Combination Sets combining a Vacuum Tubes: A storage bat- Reproducer and Power Am- tery tube of new and approv- C__MAGNAVOX RADIO VACUUM plifier in one unit; ed design for all standard cir- TUBE TYPE A is a storage battery tube $59.00, $85.00 cuits . $5.00 for use as audio frequency and radio frequency amplifier in all standard circuits. Highly recommended also for detector use. This tube is not Magnavox Radio Products are sold by reliable dealers every- critical of adjustment either as to plate or fila- where. If unacquainted with the Magnavox store in your ment. Filament consumption one quarter of an ampere. vicinity, write us for information. The most notable feature of the new Magnavox Radio Tube consists in eliminating the grid. The name Magnavox is your assurance of quality and efficiency. Unlike the ordinary storage battery tube, Mag- navox Tubes give the electrons an unobstructed passage between filament and plate, with the THE MAGNAVOX CO., OAKLAND, CALIF. result that the Magnavox has less than one half NEW YORK SAN FRANCISCO the internal capacity of other tubes of similar type. Canadian Distributors: Perkins Electric Limited,Toronto, Montreal,Winnipeg 9R

6 Tell them that you saw it in RADIO

www.americanradiohistory.com ANNOUNCES THEIR NEW POWERFUL NEUTRODYNE MODELS THE GEORGIAN AND THE Y

Power -to produce great volume. Power - to bring in distant stations. Power -to work through local stations. Power -to moderate or intensify volume.

The Garod Georgian Power-to render the original quality of Rich brown burled walnut, with door - tone transmitted. panel borders of inlaid ebony and holly -5 tube model- buik-in loud sj sker- battery compartments and accessory Power -to select programs. drawer. Will grace the finest drawing room -provide the best in radio reception. Size 351/2" long -165/e" deep -421/2" Power -to get the best out of the program. high. $400(13 -0)

The Garod V These models have power plus -and then more are full voiced tonal quality Genuine mahogany highly finished power. They -with cabinet -graceful i5. sloped genuine of exquisite timbre. They can be controlled to mahogany panel -- carved feet -five inch dials -double reading Weston meet the capacity of the small living room, or volt - meter -5 tube model. Size full advantage of the 308.' ¡oilg- 133/4" deep- z I3/e" high. manipulated to take $195oó acoustic possibilities of the large hall. In every respect, they are worthy of bearing the name GAROD.

The Garod RAF We are now ready to enter orders, and grant The receiver that made GAROD jobbers of standing, exclusive non - conflicting famous. Added mechanical improvements - 4 tube model - with territories, where open. which you are familiar. Size 191/2" long -73/8" deep-so" high. NEuGrarzóo:. .mo $135.22 TRÖD A/r' `0.LTMOLMRRRL4LLS"TCOIf

SEE OUR EXHIBITS AT First Radio World's Fair Third Annual Chicago Radio Show CT& GF1RGB Corp. York Coliseum, Chicago, Ill. Madison Square Garden, New 120 Pacific Street, Newark, N. J. September 22 to 28, 1924 `T(ovember 18 to 23, 1924

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www.americanradiohistory.com Radiotron WD-11 Don't BuyJust Tubes! Ifyou go into a reliable store and ask for a vacuum tube, you will probably get a genuine Radiotron, because most reputable dealers carry nothing else. And most buyers mean "Radiotron" This symbol when say of quality is they "tube." But the wise man says your protection. "Radiotron." And he takes the precaution to look for the name on the base, and the RCA mark on the glass. Those names have a history It isn't a genuine WD -11 unless it's a Radiotron. of invention, research and development back of It isn't a genuine WD -12 them unless it's a Radiotron. that has resulted in the production of the It isn't a genuine UV -199 finest tubes possible today. And they have a unless it's a Radiotron. It isn't a genuine UV-200 history of best performance right within every unless it's a Radiotron. fan's experience. That's why knowing fans It isn't a genuineUV -201 -a buy unless it's a Radiotron. by the name: Radiotron. Radio Corporation of America Sales Offices : Dept. 59 233 Broadway, NewYork 10 So. LaSalle St., Chicago, M. 433 California St., San Francisco, Cal.

adiotronREG. U. S. PAT. OFF.

8 Tell them that you saw it in RADIO

www.americanradiohistory.com RADIO °-" Established 1917

Number 9 Volume 6 SEPTEMBER, 1924

Radiotorial Comment editor TO amateur and novice alike should be sounded a SEVERAL letters have been written to the warning to be careful in buying from the gyp objecting to statements regarding the wasteful- ampli- radio dealers. The gyp was originally a gypsy ness and inefficiency of resistance-coupled issue. Some horse -trader, here today and gone tomorrow, ever in fiers as published on this page in the July of deliberate mis- state- search of new victims. Radio, like other new industries, of the writers even accuse us manufacturers has attracted many such sharpers and swindlers ever ment of fact so as to favor transformer amplifier. ready to capitalize public ignorance or carelessness. by "knocking" the resistance -coupled in question fails They are but one step removed from the street peddler A careful reading of the editorial as it was stated of cheap fountain pens and near -silk socks. to reveal any basis for such accusation, satisfactory to those They have a big bag of tricks, all intended to de- that resistance coupling will be reproduction of local music ceive and to bring profit to none but themselves. By content with more perfect further improve means of extravagant claims, low prices, and selling until such time as the radio engineers on appearance rather than performance, their primary the amplifying transformer. favor of no advertiser has appeal is to curiosity and gullibility. Much of their Furthermore, the fear or in these columns. The stock consists of seconds and obsolete material. When ever influenced what appears facts which will asked for standard articles they generally try to sell endeavor has always been to present as to the perfec- something "just as good." help the reader. That no brief is held may Unquestionably, bargains in radio equipment are tion of the present audio-frequency transformers else- frequently to be found, especially in lines whose manu- be gleaned from the report of the tests ptkblished facture is to be discontinued. Many legitimate dealers where in this issue. wonder is that have clearance sales so as not to carry over slow - They are far from perfect, and yet the that moving goods. But these are not sold under false such excellent results are secured with apparatus The pretenses. has been developed while the radio art is so young. improvements Generally it's his own fault if a victim is caught.. next few years will witness remarkable will be He lets his cupidity override his caution. He forgets in transformer design, not the least of which that the "caveat emptor" of the ancient Romans applies the use of permalloy as a core material, enabling one to do the work of three. to the modern gyp. So we repeat : "let the buyer transformer and tube beware. The admittedly improved quality of reproduction 64...904.9 secured with resistance coupling is obtainable only at HE opening up of several bands of shorter wave- the expense of considerable increase in B battery volt- of lengths for C. W. transmission comes as a most age so as to deliver sufficient current for operation welcome surprise to the radio amateurs. The tubes at their point of highest efficiency. A large part complete text of Commissioner D. B. Carson's letter of this energy is consumed as heat in the resistors, so of authorization appears elsewhere in this issue. It is that, to equal the volume of sound from a two -tube to be noted that the restrictions of silent hours on these transformer -coupled amplifier, it is necessary to employ bands below 80 meters is no longer to be enforced. three stages of resistance coupling. This is due not Recent experiments have shown that these short only to the loss in the effective plate potential, but also of one waves are far more desirable than the longer wave- to the large reflection losses between the plate lengths hitherto assigned to the amateurs. Their use tube and the grid circuit of the next tube. with will give an added interest and impetus to amateur We are therefore forced to the conclusion that, im- transmission and help to encourage more to enter the the available tubes having a relatively low plate game. pedance and amplification constant, resistance-coupled These concessions should be regarded as a reward amplifiers are uneconomical and inefficient. for the praiseworthy manner in which the amateurs Until sucth time as pending improvements are made have acquiesced to previous restrictions. They indicate in transformers, a properly designed choke coil coupled that the government officials are fully alive to the value amplifier will be found more efficient and fully as dis- of amateur experimentation: Even virtue sometimes is tortionless as resistance coupling. Directions for con- thus additionally recompensed. struction will appear in an early issue. RADIO FOR SEPTEMBER, 1924 9

www.americanradiohistory.com The Brasspounders of Nippon An Explanation of the Japanese Telegraph Code ' and An Account of the Operators' Difficulties By Volney G. Mathison THOMAS Brown, Jr., radio op- hmptyz ?klgst zzystvwlpzokman5jp2totq characters the meaning of the madden- erator of the good ship Aunt jwxgmzweptgsopm " ing jumble of dots and dashes which are Columbia, is away out in mid - "Blank the blank blank blank Pacific. of a so infuriating to his Occidental brother. He has sat up all night and far blankety- blanked son of a blank into blank To the layman, the transmission of the wee hours waiting for his Jap!" raves Thomas Brown, wrenching chance telegrams in an apparently letterless or to slip a message across a. two- his sweaty phones off his aching ears thousand-mile and non -alphabetic language like Japanese bulge of the earth to the slamming them down on his gummy desk coastal station appears almost an impossibility. How- at San Francisco, telling with such a bang that he breaks a piece ever, the home as every naval and commercial office about, the cargo in the off one of the hard rubber ear caps. radio capacious hold operator who has ever sailed on of the Aunt Columbia, "How in hellsbells is a guy gonna do the Pacific number of passengers has found out to his sorrow on board, probable any work with them low -down rotten, and anger, date of it can certainly be done. The arrival, and much other impor- yellow, slant -eyed son of a sea-cooks method tant information. used does not seem to be under- burnin' up th' air with that blasted dash - stood by one American radio man out At last, after hours of, weary calling dash -dotta -dash- dot -dot junk, night an' of a thousand. Like Thomas Brown of and waiting on the part of Thomas day, day an' night, from Yokohama to Brown, Jr., the Aunt Columbia, the average per- KFS or KPH comes in 'Frisco, an' back ! again They do it for spiring key -puncher, sitting in his two - with a "Q- R -V -go ahead." a With pure cussed meanness; I wish we'd have by -four coop on a hot tropical night heart -felt sigh of relief, . our .brass - a war ; I'd grab a gun an' go after 'em listening with bad grace to the compli- pounder. eagerly reaches for his key and tomorrow !" -and so forth and so cated combinations of hammers out his shrill dots and message. But, alas, and forth. dashes emanating from also, alack, upon throwing the Jap ships, his aerial, What Thomas Brown Jr. of the good assumes that the infernal yellow switch back onto his three -step receiver devils ship Aunt Columbia doesn't realize is have got up an ungenerous secret code to get the hoped -for "Received all OK" that some poor sweating devil of a Jap, by which they are enabled somehow to from the distant land station, he now whom nature intended to run wild in communicate among themselves and with finds his head phones filled with the high a rice field with a breech -cloth and a which they can jam the ether with shrill note of a powerful nearby trans- straw hat, is sitting cooped up just like senseless signals the moment they hear mitter making a noise something like Thomas Brown in a hot radio shack this: an American code slinger trying to somewhere on the Pacific, cursing no slip a couple of messages through edge- "JAB, JAB, JAB, JAB, de JOK, less fervently in his own Nipponese way wise. JOK, JOK : Zokgwg5l ?mzyspznb ---st as he strives with a brush and a bowl of It is my aim to try to present in an yz93yzpwwerpzgk! Oggwetyhkagdryic ink to put down in difficult Japanese interesting manner something of what Mr. Takomoto Nogo, the Japanese "Sparks" of the Nippon Maru, is up against ; and, in order to do so, it is first necessary for me to tell a little about the Japanese language. I have already sort of insinuated that Japanese writing is letterless. This, however, is not strictly correct. Unlike Chinese, upon which much of modern Japanese has been built, the language of Nippon has been systematized into a phonetic syllabary represented by forty - seven symbols. In addition to these, there are twenty -six diacritical marks, which, with the exception of one very important one, are dispensed with in telegraphing. We do not have here a true alphabet, but a system of grouping syllables together. By use of the symbols and marks, all Japanese sounds, and hence all words in the language, can be reproduced. Since the Japanese characters are taken from the Chinese, all Japanese writing is highly mystifying to a China- man, who at once recognizes the symbols, but can make nothing whatever of their combination. This is not by any means the only One of the berated "Teishinshos." A section of the radio room on the Toyo Kisen Kaisha liner system of writing used in Japan, but it "Tenyo Maru," showing powerful 7- kilowatt quenched spark transmitter is the only one that can be telegraphed. 10 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com ee 7 wah wee sah row kah NO kee

Oh you has 3 yo z nee tah koo Zay

yah mee - .. hoe ray

hay so n/ah shee aye toe tsv kay

tchee neigh too Thee

ree nah hrwo Moire - zet new 7 da each ach roo MOO tay 7- soo wawk vgh __.__ ah n

The Japanese syllabary, with corresponding telegraphic code groups and approximate pronunciation that can be done by it has always been despised by eighteen of them containing five dots and about all the loving Though without the operator or the scholars and high- brows, it is widely dashes each. radio in Japan, to jail ; because kissing used by the common people and nowa- In the illustration, I have represented somebody going all mention of kissing is considered days appears in almost all Japanese pub- the forty -eight Japanese phonetic sym- and height of immodesty. lications. It gives the sounds of the bols, their dot -and -dash groups, by which as almost the of the Japanese unfamiliar Chinese characters which they are telegraphed, and their pronun- A brief inspection convince anyone that the have been immensely absorbed by the ciation -this last only approximately. syllabary will of Japanese radio operator is not Japanese, and it is the only practicable Two of the symbols have exactly the lot the Where the American op- medium for the expression of foreign same sound, but are written and used to be envied. it no small feat to learn to scientific terms and meanings. differently. These forty -eight charac- erator deems our twenty - The other Japanese writing, which ters have no equivalents in English. handle at commercial speeds code, the Japanese has to learn the radio operator is expected to under- I have also given the Japanese trans- six- letter forty -eight dot -and -dash stand, and which he may be called upon lation and dot -and -dash groups of a a code of groups, and has to copy these down to translate into the phonetic system, is short radiogram. The "love and kisses" into Japa- rapidly in separate unconnected symbols, purely ideographic ; that is, it employs part of it is tamely translated as may be seen in the il- symbols for ideas. It is necessary, as in nese as "friendly compliments." This is some of which, Chinese, to learn from three to six N thousand root symbols in order to use H/ome Friday. Love and kisses . Mary this system. This writing is absolutely unintelligible when spoken ; it can be understood on paper only. Ho`r, e Friday When telegraphy was first introduced into Japan, the main problem was to tsu - Roo /reehyo devise dot and dash combinations for the forty -seven symbols and one essential diacritical mark of the phonetic system. tY3 This code was originally worked out by Japanese and European wire- telegraph experts before the year 1900, but after the Russo -Japanese war it underwent some alterations. It is a highly perfected but difficult Love and kisses Mary code-difficult because, while in English and other Aryan tongues we had only Yo- ro - shee -koo Hannah -ko from twenty -three to twenty -six letters to set into dots and dashes, in Japanese these are forty- eight. There were, of Iz course, insufficient short combinations of dots and dashes to go around ; so, in would write the Oriental symbols order to complete the code, it was 21 radio message translated into Japanese. fi Japanese necessary to use some long groups, vertically instead of horizontally RADIO FOR SEPTEMBER, 1924 11

www.americanradiohistory.com lustration, are rather difficult. Further- to pass the tests for a first -class certifi- more, turnips behind certain of our American the large influx of new words and cate. The obtaining of this document steamship thought into payrolls are so fond of making Japan, requiring more ac- requires successful sending and receiving out. curate means of expressing ideas, is caus- in the Japanese syllabic system at a Furthermore, to a native Japanese in ing a steady increase in the number of speed of 100 symbols a minute, sending Japan ( not to a foreigner!), a yen is symbols and marks in use, and may and receiving in English in the conti- virtually equivalent to a dollar to us in eventually compel an expansion of the nental code at twenty words a minute, America-except in the case of imported telegraph code. and much radio law and theory. luxuries. Looking at the matter from In addition to learning to telegraph in The first -class license is permanent ; this angle, the Japanese radio operators the straight syllabic system, the Japanese the Japanese radio operator never has are somewhat higher paid than are student is expected to translate all other to renew his certificate or take another American. Japanese writings into this system, before examination; and, considering what he In comparing the conditions he can telegraph. surround- He must be familiar has been through, it would appear super- ing the Japanese and American wireless with the common spoken tongue, the fluous ever to require him to do so. In- operator, the observer cannot miss polite tongue, the and the ideographic sys- cidentally, the Japanese operator never fact that the Japanese commands a much tem of four or five thousand symbols, posts his license in the radio room, which higher rating on board ship. This is which are too much for even a Chink, procedure is required by law under most especially true in the case of the and many chief of which may be read three flags, but, as one light- hearted Nipponese operator. While the second and or four third different ways, according to cir- brasspounder rather quaintly explained operators are messed with engineroom cumstances. Add further that all these to me, "I carry it around in my poahkee and deck officers, as is done on almost all kinds of written symbols are likely to until I walk into my coffee." American vessels, the chief operator is be encountered on one page, and that The average salary of the Japanese a pretty highly privileged person and there are four or five kinds of script, and sea -going radio man, if he holds a first - eats his meals among the passengers in it will be seen that the task of manipu- class license, is about 120 yen for third the first -cabin saloon, in company with lating Japanese is excruciating. operator, 140 for second, and from 200 the captain, chief engineer, and chief Just sort of incidentally, as it were, to 250 for the chief operator. A yen is mate. He is a genuine officer and his the Japanese radio operator is further about fifty cents; so, in cold dollars, the salary is usùally higher than that of any required to read, write, and speak Japanese operators' pay is distinctly man on the deck outside of the chief English, and to be able to telegraph in lower than the Americans' ; but nothing mate. The American radio operator, on English in the usual continental code. like so much as some of the bloodless Continued on page 46 This all appears formidable to the American, and it is hardly less so to the young Japanese radio student. The reader will vividly realize this when I state that Japanese students sometimes become despondent under the strain of trying to accomplish so much and com- mit spectacular suicide by leaping from lofty cliffs or casting themselves down into steaming volcanic craters. These tragedies of Japanese technical student life are not the result of insanity, as we usually employ that word, for the despairing ones almost invariably leave behind intensely human farewell letters showing them to have been in full pos- session of their reason up to the last moment ; nor is it the outcome of anything inherent in Japanese nature or in Buddhist teachings, as is imagined by some ; but is simply due to the killing stress of endeavoring to emulate the Oc cident, of struggling to reach the standards of western acquirement hin- dered by a fundamentally different language and handicapped by sadly poor equipment, opportunities, and resources. Unless the student is in a naval or mili- tary school, he has tó fall into the ranks of the poorly -paid physical laborers during a large part of the day or night, in order to earn his living and pay for his college tuition. Hungry, overworked, and often disappointed, he finds the struggle intolerable and so passes out into the darkness. The successful Japanese radio student is usually granted a second -class commercial license, which is issued by the government, under a strict examination. After two years or more of sea service, the intelligent operator is usually ready A Navajo Family Listening to Radio on the Brink of the Grand Canyon of Arizona 12 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com Radio -Frequency with the Single Circuit Regenerative Receiver Detailed Instructions for Adding One Step of Efficient Tuned Radio -Frequency Amplification to a Regenerative Receiver By E. E. Griffin balancing condenser may be gained. A WHEN adding radio -frequency the tube socket, as shown in Fig. 2. sets are small board about 8 in. square, with the to a set, naturally the first Some standard regenerative in two condensers mounted at the back and question of general interest is already connected in this manner, will the tube and coil at the front, is suffi- "What will it cost ?" In the following which case no change at this point oper- cient. method, since all the parts of the regen- be necessary. The difference in is so r --- A erative set are made use of, the cost of ation between the two methods However, additional parts necessary should not slight it is unnoticeable. type 7b vi/O.v6s total over ten dollars, if bought, and using tuned radio- frequency of the the latter method is OR AdOM most fans can even reduce this ; plus, of herein described, grid of the ,-- course, a small amount of labor, which necessary, as otherwise the AMAL/R/ER the average fan enjoys. detector tube will have a high positive The additional parts necessary are: potential, which would completely block its action as a detector. I condenser, vernier type, i 43 -plate variable step is to convert the open with dial (.001 mfd., marked C2). The next - ' + circuit of the regenerative set into the 1 50 -turn honeycomb coil. G 111111111111}-. 1 variable condenser, non- vernier, with knob. tuning device for the radio -frequency 2. Modification Preparatory to Adding 11 plate (.00025 mfd., marked C3). C1, is of Fig. tube. Ascertain if condenser, R. F. Amplifier 1 tube and socket. the 23 -plate or 43 -plate type. Next, The .001 vernier condenser can be of count the number of turns on coil D. First connect the .001 mfd. condenser any standard make. The 50 -turn honey- If condenser is of the 23 -plate type, G2 in series with the honeycomb coil, comb coil is recommended, but almost there should be 55 turns of wire on placing the coil so that it will be at right equal results can be obtained with a coil D, with a tap taken off at the 50th angles to the tapped coil D and tickler for testing. homemade, straight -wound coil of 45 turn ; if of the 43 -plate type, there coil when in the final position turns on a 21/2-inch tube. The I1 -plate should be 33 turns on coil D, with a Then mount the tube socket, connecting condenser should be fitted with some tap taken off at the 30th turn. It will the negative filament to the free end of sort of adjusting knob, but a dial is not probably be found necessary to take this the honeycomb coil. A binding post at necessary, as this condenser, once set, is coil out of the set in order to remove this point will also serve as a ground not needed for general tuning. The the turns to leave the proper number. connection. Next connect the tube grid and additional tube should, of course, be the If Cl is of a capacity between .0005 to the point of junction of the coil same as the tubes used in the set. and .001 mfd., the proper number of condenser C2 ; also connect the 11 -plate turns for coil D can be determined by balancing condenser Cs to the grid. between these rough interpolation ; the greater the About 11/2 in. spacing number of plates in C17 above 23, the less units will help. the turns on coil D, up to 43 plates, Make sure that all connections are which has only 33 turns. The exact tight, preferably soldered, as any undue total number is not critical, the two resistance in this circuit greatly affects extremes given being sufficient to cover its sensitiveness. Connect the positive the broadcasting band. and negative filament posts of the socket The relation of the number of turns to the corresponding posts on the detec- on either side of the tap, however, is tor tube of the set. In this manner the quite important, the number from the filament rheostat of the detector tube tube. tap to the end should be always 1 /11th also controls the radio -frequency 1. Single- Circuit Regenerative Hookup. Fig. of the total number, when using a Referring to Fig. 2, lead marked G, mfd. condenser for balancing. which was formerly connected to coil D, Fig. 1 is a single- circuit regenerative .00025 will serve as one of these leads. hookup. Only detector and Replace coil connecting upper end as detector Here it may be stated that the fila- shown in this diagram, as it originally was and connect condenser phones are ment control of this radio -frequency of audio -frequency ampli- C1 around coil as shown by dotted lines, the addition as in the case of the the addition of Fig. 2, leaving tap free. The tickler, tube is not critical, fication does not affect method of control. Con- There are probably or movable coil, is left unchanged, and potentiometer radio -frequency. nect the plate of the radio- frequency receivers in this country using this serves the same purpose as before. The more tube to the junction of condenser C1 circuit than all other types of receivers lower or tapped end of coil D is not connected to ground and filament lead. and coil D, as shown in Fig. 3. Con- combined. nect the free side of condenser C3 to end first change necessary in the con- To assemble the radio -frequency unit, The of coil D. Connect the tap on D to ventional regenerative set is the grid it is advisable to use a small test board separate 671/2-volt positive B battery. If your leak, which is generally connected outside of the set, wiring the to the set uses 45 -volt B battery, this will be around the grid condenser, as in Fig. 1. parts complete, then connecting with the found sufficient, al t h o u g h slightly One side is disconnected, and connected set. In this manner familiarity of the use of the greater amplification will be found at to the positive side of the filament at circuit and knowledge RADIO FOR SEPTEMBER, 1924 13

www.americanradiohistory.com the higher voltage. Last, connect an- radio -frequency tube and place the small and each must be tuned tenna to separately to free side of 43 -plate con- piece of paper under the opposite fila- the wave of the station denser C2 desired. A cer- ment contact and repeat the operation. tain setting on C1 will always call for Keep in mind that C2 is adjusted for a certain setting of C2. To this end, a NOW we come to the most inter- loudest signal and Cs for faintest. Note tuning chart will prove helpful. esting operation, that of balancing again the position of C87 and set it at a The sensitiveness of the -set is sur- the capacity of the tube. Place the position about half way between the two prising, a single wire placed along the radio -frequency tube in its socket and points. Remove the small piece of paper moulding of one side of a room being see that it lights with the detector tube. from under the tube contact and set is quite sufficient antenna for reception of Set the condenser Cs so that about one - ready for operation. all stations formerly received on a large third of the rotary plate area is in mesh One setting of Cs will be found suf- outdoor aerial. with It will at once be seen the stationary plates. This is an ficient for the average broadcasting that such a set, with approximate dry cell tubes, setting and will be changed wavelengths. However, if it is desired makes an ideal set for later. that camping trip. to tune to lower or longer waves, the The radio-frequency control Pick out has obvi- some nearby broadcasting tube will break into oscillation and C8 ously many advantages over the poten- station, one good of signal strength, and must be slightly readjusted to stop it. tiometer and reversed feedback methods, tune it in loudest by varying condensers The tube must be balanced for a certain and is nowhere near so critical of ad- C1 and C2. It will be found that these antenna. Whenever the set is used on justment in general use. two condensers independently tune of a, different antenna, a slightly different The complete circuit diagram of a eac1i other, similar to a very loose - balance will be necessary. four-tube set built from a standard re- coupled set. During this adjustment After becoming familiar with the generative receiver is shown in the Fig. 3. tickler coil should be set at a position operation of the radio -frequency unit on For use on a small loop, the honeycomb about half way between the oscillation a test board, it should be incorporated coil is . disconnected and the loop con- point and zero. as a part of a complete set, or a separate nected in its place, condenser C2 being With the two condensers C1 and C2 unit built to match the original set, but, placed across the loop for tuning. set at maximum The signal strength, remove as single- circuit regenerative receivers results obtained on a two -ft. loop are the radio -frequency tube and place a differ widely in construction and ar- most gratifying. small piece of paper under one of the rangement, it is left to the reader's filament terminals, replacing the tube. preference. The tube filament will not now light, The main points to be remembered but the signals will still be heard faintly, are that all wiring of the radio -frequency through the capacity of the tube. Now unit must be good, leads as direct and slowly adjust the balancing condenser short as possible, ` the honeycomb coil C8 until a point is found where the sig- must be placed at right angles to the D nal entirely disappears or is at its faint- coil and tickler coil, or else balancing est, then adjust C2 until maximum will be difficult. ' Make sure that the strength is obtained ; likewise adjust Cs balancing condenser C8 has no tendency for minimum. Do this several times to shortcircuit between the plates, as ac- until a point is found where the signal cidental shorting of these plates puts the is entirely tuned out by C8i_ but the high voltage B battery across the tube open circuit is in tune with the incoming filaments, as will be seen by tracing out wave through C2. This tuning of Cs the circuits. Also remember that, each and then C2f by the seesaw method, is time the wiring is changed, the balance quite necessary, as changing the capacity of C8 against the tube is thrown of C8 slightly affects the period of the slightly off. antenna circuit. The object is to get For those who have had no experience the least amount of energy through the in the tuning of two -circuit sets, a word capacity of the tube and at the same will not be amiss. The tuning control time have the open circuit exactly in C1 and tickler coil will bear practically tune with the incoming wave. the same relation as the original regen- When this point is approximately erative set, but the tuning of C2 and C, found, note the position of C8, remove are entirely independent of each other,

Fig. 3. One Stage R. F., Detector and Two Stages of Audio 14 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com The Vacuum Tube as a Detector How a Grid Bias Battery or a Grid Condenser and Grid Leak Enable a Detector Tube to Function By C. M. Jansky, Jr.

THE principles underlying t h e while Fig. 3 (C) shows the component oscillatory groups per second produced operation of a vacuum tube as a which would flow through the head set. by the transmitter. detector are very different from Rapid radio -frequency pulses as shown The principles involved in the detec- those under which the tube operates as in Fig. 3 (A) and (B) can produce no tion of radio telephone signals are the an amplifier, as discussed in August same ; the receiver diaphragm's following RADIO. There are two ways in which Time the envelope of the incoming radio -frequency wave. This envelope, in a prop- a tube may be used as a detector : (1) wave, should correspond by using a bias battery ; (2) by using erly modulated and to the modulations of the speech or music the so- called stopping condenser (A) grid leak. As the first method is easier actuating the microphone at the transmitting station. to understand, although less used, it will Damped wore siyna/ be discussed first. The usual method of using a tube as a Consideration of the tube characteris- detector is with a grid condenser and grid leak as in Fig. 4. The space be- tic curves of Fig. 1 shows that for un- distorted amplification with a grid C battery permitting operation from a (B) point P near the center of the curve, the Disfor/ed p /ate cre.'/ plate current should rise as far as it falls. due to bias haffere But for operation as a detector the C battery voltage is adjusted so as to give the maximum difference between the amount of rise and fall. Thus for the detector circuit of Fig. 2 employing a tube with the characteristics of Fig. 1, (c) Phone current with 22.5 volts on the plate, the negative grid should be Fig. 3. Detection in Tube Circuit Using voltage applied to the Grid Bias Battery Fig. 4. Tube Detector Circuit With Grid about 1 volt. Condenser and Grid Leak The principle of detection can be best on the receiving diaphragms be- effect tween the grid and filament will pass explained by considering a damped wave cause (1) the inductance in the re- Fig. 3 (A) is a current only from grid to filament and radio telegraph signal. ceiver coils is too great ; (2) the inertia not from filament to grid. That is, elec- plot of such an incoming wave as a func- of the diaphragms will not permit them trons will pass from filament to grid but tion of time. Fig. 3 (B) shows the respond to such rapid pulsations. to not from grid to filament. total plate current which would flow The receiving diaphragms can, however, This explanation of detec- respond to the grouped effect of each (NOTE: tion by the use of a grid condenser will spark as shown by Fig. 3 (C) and the not stand ultra -scientific criticism as de- is an audible note. The frequency result under othcr conditions heard will correspond to the number of tection does occur but the author fears that a more tech- -7 nical discussion would tend to confuse the reader rather than to give him a clear understanding of this particular phe- nomenon which is less understood than almost any other taking place in the operation of a radio circuit.) Fig. 2. Receiving Set Using Detector Tube -S For the purpose of discussion let us Grid Bias With assume that the incoming signal is identical with the damped wave signal shown in Fig. 3 (A) . Fig. 5 (A) is a graph of the voltage across L as a func- P tion of time. During the half cycle -3 4p0 when the top of L is positive with respect to the bottom the voltage across various parts of the circuit will be as shown by Fig. 6. The left side of C will be charged + and the right side -. a -{- e This will leave the grid with charge with respect to the filament. As a + grid will attract electrons some of the + charge will be neutralized by _g -.3 -2 -/ o t / electrons which come from the filament. GR/0 VOLTAGE During the next half cycle, voltage Fig. 1. Vacuum Tube Characteristic Curves relations will be as shown by Fig. 7. RADIO FOR SEPTEMBER, 1924 15

www.americanradiohistory.com Grid current will flow during each half called, is sometimes connected directly In time t = RC seconds the voltage cycle as shown by Fig. 5 (B). will It across the grid condenser, in which case of the condenser will have dropped to be seen that the grid is with respect - the electrons pass through the tuning in- 1/E 1/2.7 36% of its initial to the filament. However, the = = value. - ductance. The constant R X C is called the time The circuit containing the grid re- constant of a circuit containing a con- sistance should always be connected to denser of C farads in series with a re- (A) the + side of the filament as indicated sistance of R ohms. A circuit with a in Figs. 4, 6, and 7. When a tube is stopping condenser of 100 micro micro used as an amplifier /ltonling Jigno/ the grid return farads with a 1,000,000 ohm grid leak should be connected to the - side of the has a time constant of .0001 second, filament. This difference is due to the that is, a charged condenser with a fact that grid current is undesirable capacitance of 100 micro micro farads (8) when a tube is used as an amplifier but it will discharge Grid cvtirnt through a resistance of is necessary to the operation of a tube as 1,000,000 ohms to 36% of the voltage a detector with a stopping condenser. originally across it in .0001 second. The correct values for the capacitance This is about the correct value for the (c) n of the grid condenser and the resistance time constant which should be used in of the grid leak are of importance. In the grid circuit of an ordinary receiving ordinary receiving circuits the grid con- set. If the time constant of the grid 6rid ro/tor. denser should have a capacitance large circuit is too small distortion will result compared with the apparent input from loss of the higher audible fre- capacitance of the tube; that is, from 100 quencies. If the time constant is too to 500 micro micro farads. The grid large the signals received will be weak. (o) P/dr. Ob/i.nt leak should have such a resistance as will Good mica grid condensers can be permit the grid condenser to discharge purchased at low cost. Grid leaks of rapidly enough to follow the highest fixed values are also on the market. Fig. 5. Detection in Tube Circuit Using Grid Condenser and Grid Leak Grid leaks can be easily made with a soft pencil and a small piece of smooth potential will be more pronounced than cardboard about 1 in. wide and 2 in. would have been the case if electrons long. Put small bolts with washers had not passed from filament to plate through the cardboard near the ends. during the previous half cycle. Before tightening bolts blacken card- During the next positive half cycle board under bolt head thoroughly. The electrons will again pass from filament bolts may be used to fasten the grid leak to grid. The result of the variation of to a small piece of fiber or to the receiv- grid voltage from -}- to - is an accumu- ing set panel. The correct value of grid lation of electrons on the grid and on resistance is obtained by drawing lines the right side of C, that is, the accumu- with the soft pencil between the black- lation of a negative charge. This ac- ened areas which are connected with the cumulation will continue until the grid Fig. 7 bolts and which extend under the bolt assumes such a - charge that no posi- heads. tive half cycle can make it + with re- audible frequencies met with in radio spect to the filament. Fig. 5 (C) is a telephony, yet it should be sufficiently "LOGGING" STATIONS graph showing how this - charge is high to prevent the grid condenser from HEARD accumulated by the grid. Fig. 5 (D) discharging appreciably between radio - By HARRY A. NICKERSON shows the current through the phones frequency pulses. Correct values run Keeping a record of dial as a function of time. The receiver dia- from 1 to 5 million ohms. settings is phragms will vibrate to correspond. a great help in relocating stations heard. ( NOTE : It is evident that the re- This is especially true of neutrodyne Without R connected from grid to quirements are quite different for the sets. A simple method is to mark a filament the electrons which have ac- tube used as the first detector in a super- white line on the panel just below the cumulated on the grid and right side of heterodyne where the rectified frequency lowest point on the circumference of the C would remain indefinitely and the grid is of the order of 50,000 cycles per sec- usual tuning dial, and vertically below would hold the - charge thus secured. ond from the requirements in a simple the usual mark that appears above the However, between one train of oscilla- receiving set where the rectified fre- dial as an indicator on manufactured tions and the next the excess electrons quency does not exceed 5000 cycles. sets. Paste a strip of thin, good -quality leak off to the filament through R and This point will be discussed further white paper on the front surface of the the grid returns to its normal potential. when we consider superheterodyne or The "grid leak," as the resistance R is dial along its edge where there are no intermediate frequency amplifier cir- graduation cuits.) marks. This paper should be of width sufficient to mark thereon The rate of discharge of a condenser call letters of stations heard. through a resistance as a function of Where the dial comes to rest opposite time is given by the equation : the white line marked by you on the panel, mark on the dial paper the call e=E0 E RC t letters for the particular stations then in 'which "tuned in." e = voltage across C at any instant. It will probably be found that, owing t = time in seconds. to the larger number of stations oper- Eo = original voltage across C. ating at 360 meters, special care will E = Naperion base 2.7. have to be exercised to mark their call C = capacitance in farads. letters in exceedingly small type to avoid Fig. 6 R= resistance in ohms. crowding. 16 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com An Improved Reinartz Receiver A Cheap Set that is Efficient, Selective and Flexible for Both Amateur and B C L Waves By Cessford Kerr, 6 BHG THE Reinartz circuit employed in tions necessarily introduces a switch with has a maximum capacity of .0005 mfd. this receiver makes possible a its attendant disadvantages. However, and is connected with the rotary plates low -loss tuner that operates ef- this loss may be largely overcome by us- to the antenna. Likewise, the rotary ficiently from 80 to 300 meters, and by ing a good switch, being careful that no plates of the tuning condenser should a simple substitution of coils will receive long parallel leads are used in the wir- connect to earth. the broadcast and commercial wave- ing, and making sure that all connections lengths. An antenna de- tuning device are real electrical connections. is introduced to minimize radiation from The short wave primary and second- the set. ary coils are of the "basket weave" type. A short wave, low -loss tuner is of To still further reduce the losses, the especial interest to the transmitting coils are mounted so that they are 11/2 amateur, but it should also be of interest in. from the base board and fully 2 in. to the broadcast listener since some of from any apparatus. the foremost broadcast stations now transmit on waves in the vicinity of 100 meters. It is possible with this set, at Panel View Salt Lake City, to tune the 94 meter -;wave from KDKA or the 110 meter The form for winding the "basket wave from WGY, and receive them weave" coils is made as follows : with comfortable audibility on one step On a heavy board, inscribe a circle of a.f. amplification, when they are 3/ in. in diameter. At equal distances totally inaudible on their regular broad- about the circumference drive nine large cast waves. nails into the board. The nails should To tune the very short waves without Rear View protrude about 1Y2 in. on the other making the adjustment unduly fine re- side. quires an 11 -plate secondary tuning con- Since it is not so important that the The coils are wound by weaving the denser, having a maximum capacity of high frequency resistance of the plate wire alternately outside and inside the .00025 mfd. It is extremely important circuit. be kept low, the plate coil is nails. Before removing the coil from that this condenser should have very low wound with No. 24 D. C. C. wire on a the form it should be bound with thread losses and a low tílinimum capacity. 3 in. cardboard tube. Larger wire might at the points where the wires cross be- However, with this small condenser, be better but space does not permit its tween the nails. it is not possible to cover the entire band use. The coil consists of 60 turns The primary and secondary coils are

from 80 to 300 . meters with one coil. taped every 15 turns, although. 45 wound with No. 18 D. C. C. wire. No. Since it became necessary, therefore, to should be enough. This coil is wound 14 or 16 would be even better. The tap the secon4ry it was made in two so as to leave about 11/2 in. of unused primary is wound in the same direction sections, placed at right angles to each tubing at one end. This portion of the as the plate coil, and consists of 7 turns other as shown in the rear view. This tube ' is practically all cut away, leaving tapped at every turn. The tap at the arrangement eliminates the chance for only enough cardboard to form a solid seventh turn connects to the filament dead -end losses at this point. support for the primary and first section and ground. From this point the wind- Dividing the secondary into two sec- of the secondary. The plate condenser ing is continued for 16 turns to form the first section of the secondary. This v coil is mounted on the protruding end of the plate coil form with the primary R.FC. next to the plate coil. The second secondary section consists of 20 turns of LL No. 18 D. C. C. wire. The short wave range should be from 80 to about 160 meters, and the long wave range from 140 to nearly 300 meters. If difficulty is experienced in making the set oscillate throughout its wavelength range without operating the detector tube filament at an excessive brilliancy a choke coil should be inserted, as shown in Fig. 1, between the phones (or primary of the first amplifier transformer) and the plate. This choke may take various forms. A single layer or honeycomb coil of about 75 to 250 turns, a small air core choke such as the Kel- blogg No. 501, or a doorbell magnet Fig. 1. Circuit Diagram wound with 1000 turns of No. 32 enam- RADIO FOR SEPTEMBER, 1924 17

www.americanradiohistory.com eled wire may be used. It is best to This coil is built into a separate 'unit type- tapped at approximately one -third experiment until the best choke is found. and is so mounted as to have no induc- of its turns. The smallest part, or In this particular set, the last named tive relation with the secondary coils. primary, is connected between binding choke is used in conjunction with West- The adjustment of the switch on the posts A and B, and the secondary be- ern Electric phones or a Thordarson primary has no effect on the tuning. It tween posts B and C. These three bind- transformer. is used merely to vary the coupling being posts are those shown along the top When working properly, the tube tween primary and secondary. of the panel. From 10 to 15 turns in should oscillate steadily throughout the The value of grid leak resistance need the primary and 50 in the secondary will wavelength range with little or no ad- not be constantly variable, but should be cover the broadcast band. Proportion- justment of the plate condenser. carefully adjusted at first and then left ately larger coils will cover all the higher If, at some setting of the tuning con- alone as long as the same detector tube waves. In localities where local inter- denser, a point is found where the tube is used. When the tube starts and stops ference is slight the ratio of primary to stops oscillating or requires considerably oscillating quite abruptly with variations secondary turns may be reduced with a more capacity in the plate condenser to of the plate condenser, the correct grid corresponding increase in signal strength. maintain oscillation than at points on leak resistance is being used. If too However, this broadens the tuning con- either side, it is reasonably certain that high, the tube breaks into oscillation too siderably and may bring the antenna into at this point the secondary circuit is res- sharply, thus. making broadcast tuning resonance with the secondary if carried onant with the antenna. Such a condi- difficult; if too low, the action is slug- too far. tion is undesirable in this receiver since gish and unreliable. The second method, due originally to the antenna circuit is semi -aperiodic. It The reader might be confused by the Mr. E. L. Lester, 5NK, is much super- would be more correct to say that the extra switch points shown on the panel. ior to the first in all respects, and should antenna functions as though it were This receiver was originally built for be used especially when QRM is bad. aperiodic. In order that this condition another set of coils but at present only 8 It employs variable coupling between the may be attained, the antenna must be points are used on the primary, and 3 primary and secondary. The variable adjusted to a wavelength considerably on the secondary switch. feature allows fine adjustment of the outside the range of secondary tuning. primary coupling, whereas in the other waves above 300 It is for this purpose that the special FOR tuning to method the coupling is variable only in meters an external set of coils is antenna coil L ( Fig. 1) is provided. steps by changing the ratio of primary *n coil system may take either This coil is wound with 50 turns of used. This secondary turns. To use this hook -up, a forms as shown in Figs. 2 and 3. No. 20 D. C. C. wire on a 3 in. tube of two two coil honeycomb mounting with the with taps taken at the beginning, 5, 10, The first and simplest of these is that necessary honeycomb coils may be used. 20, 30, 40 and 50 turns. This number originally described by Mr. Reinartz. It If it is desired to tune only the com- layer, of turns should serve to keep the aver- consists of a single coil -single paratively short waves, say to about any age antenna detuned throughout the spider web, honeycomb, or other 1000 meters, a homemade mounting for amateur and broadcast range. spider web coils may be devised. This The coil switch is set at that point is shown in Fig. 4. It consists of a To Giva which will allow the set to oscillate freely and steadily throughout the range of the secondary condenser. When this adjustment is realized, the antenna will ro have no effect on the tuning, and the sec- Gro.vo ondary wavelengths settings will always remain constant. Furthermore, the radiation from the receiver is very much To Pc A TE reduced when the antenna is detuned in CONOeNself this manner. Fig. 3. Alternative Long Wave Scheine Fig. 4. Spiderweb Coil Mounting small insulating panel arranged to Aux , CawooNSEQ mount on top of the tuner cabinet. It is fitted with the three binding posts to connect with those along the top of the tuner panel. Four pieces of No. 4 or 6 brass rod about 11/2 in. long are bent and mounted as shown, two being used to mount each coil. The separation between coils should be about / in. (or less, if the coils are not too thick). The separation between the two rods of each coil mount will depend on the size of coils used. The coils connect to the large Fahenstock clips mounted on them, and the connection is carried through the mounting to the binding posts. The coils should be marked in some way so that they will always be mounted with the same polarity. A larger number of primary turns can generally be used with this arrangement than with the single coil system. furé As shown in Figs. 2 and 3, an auxili- Coi ary condenser may be connected across Fig. 2. Usual Long Wave Scheme Continued on page 62

1 8 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com Impedance Values ofAudio- Frequency Transformers A Report of Tests on Twenty -seven Available Transformers to Determine With What Vacuum Tubes They May Best Be Associated By Gerald M. Best FOR the best results in audio -fre- described at the end of the article. From Table II gives the output impedance quency amplification the input, or this table it is possible to select a trans- under several different conditions of the primary, impedance of a transformer which has a primary impedance tubes usually available. former should be at least as great as at least equal to or greater than the im- As the transformer impedance varies that of the output impedance of the pedance of the vacuum tube to be used with the conditions under which the vacuum tube with which it is associated with it. transformer is used, these tests were purpose TABLE II in an amplifying circuit. The OUTPUT IMPEDANCE OF VACUUM TUBES made with the transformer connected in of amplifying transformer is to step the Output Output output the plate circuit of a vacuum tube under up the alternating voltage in the plate Imped- Imped- Imped- working conditions of a two -stage am- the ance with ance with ance with circuit of one tube and apply it to MANUFACTURER Code 45V Plate, 90V Plate, 120V plifier. A frequency of 1000 cycles was grid circuit of the next tube. Due to No. 1M V 4M V Plate, 9V Negative Negative Negative used in each case. Fig. 1 shows the resistance of the vacuum Grid Grid Grid the effective circuit used in the tests. tube itself, it is impossible for any prac- -199 or will be noted that two sets of values tical transformer to deliver all of the 3eneral Electric Co. UV It C-299 21,000 17,000 are given in Table I, one when the -available voltage. 3encral Electric Co. UV -201-A or transformer secondary was terminated But, as may be proven mathematically, C-301-A 20,000 15,000 12,000 Westinghouse Mf. only with a vacuum tube, and the other whose impedance is equal C11, C-12 a transformer Co with the addition of a terminating of the tube working into it ob- orWD -11, to that WD -12 20,000 17,000 shunted resistance of megohm. By tains from 50 to 70 per cent of the Deforest DV -2 20,000 13,000 / Deforest DV -3 21,000 17,000 this latter expedient the primary im- voltage, while one whose im- Western Electric... 216 -A 17,000 12,000 6,000 available pedance (and therefore the secondary is twice of the tube obtains pedance that sovrce of from 66 to 90 per cent. However, if Sinq/o Frsyirencz Trons>lornlatr the transformer impedance is less than C vrrg n f under 1'6ls e that of the tube, the useful voltage falls off rapidly. On the other hand, there are several practical limitations which make it undesirable to use too high a transformer impedance, particularly at the higher frequencies where losses are caused by the shunting effect of the capacities of the winding and tube. Table I gives the impedance values 1 Illlllllllllll of various makes and types of trans- -;4 +- 8- + formers as obtained by the bridge method 1. Diagram of Connections for Impedance Tests by Bridge Method

TABLE 1 impedance) will be much reduced, as IMPEDANCE VALUES OF INTERTUBE TRANSFORMERS shown by the measured values given in Primary Impedance with Primary Impedance with the table. Secondary Shunted by Secondary Terminated cases where the addition of this MAKE OF Turns 500.000 Ohms by Vacuum Tube Only In TRANSFORMER Code No. Ratio resistance reduces the value of Effective Effective shunted Resistance Reactance Impedance Resistance Reactance Impedance the impedance to approximately that of X Z R X Z R the tube to be employed, its use will be

24500 44900 18500 87700 89800 found to give a marked improvement in Federal i 65 37700 Stromberg-Carlson 3 -A 45800 8530 46500 124600 139000 187000 quality. But, when the resulting pri- Radio Corp 17V-712 5610 4260 7050 3450 11850 11400 Sampson 6-1 8950 5350 10420 4950 21200 21800 mary impedance is less than the tube, it Jefferson 44000 14380 45300 59700 135500 148000 Jefferson Star 30600 32400 44600 10650 61300 70000 should not be employed. General Radio 231-A A470 19600 21700 4890 25200 25600 B of Fig. 2 shows the fre- Rillark 48500 19900 52500 40500 25100 47700 Curve Kellogg 501 434:1 31100 17750 35800 12600 83600 86000 quency characteristic of a typical very Sterling R-301 4:1 8560 14720 17000 4740 18500 19100 35400 149500 153600 Marie A -9 - 9:1 32600 8900 33700 high impedance transformer when termi- Marie A -6 5:1 18200 11920 21800 16300 33600 37400 tube only, and Marie A-4 3 %:1 6470 19130 20200 9270 15850 18400 nated by the vacuum New York 20900 11200 23700 25500 30100 39500 Curve C that of the same transformer Dongan 3M:1 14550 9800 17600 10200 29000 30800 Dongan 6:1 15650 23600 28300 7070 32000 32700 terminated by the 72-megohm resistance. United 5:1 14700 13780 20200 7150 28400 29200 Premier Hedgehog 5850 22400 23100 10700 17300 20400 The improvement in quality is apparent. Cotoco 4000 25200 10950 27500 25300 57700 63000 A subsequent article will give the results Cotoco Special 15800 28800 32900 5750 36400 37000 Supertran 30000 6270 30700 94200 13200 150000 of tests on all these transformers at three Thordarson 3M:1 40500 23100 46700 28300 84600 88200 Thordarson 6:1 31600 18900 36800 18000 69000 71200 different frequencies showing the vari- Amertran AF -7 34:1 47200 28600 55200 18750 113000 127000 in Amertran AF -6 5:1 12250 29800 32200 20000 92700 95000 ation of amplification with variation Precise 285 -A 34200 9530 35400 73300 113600 135000 frequency. Modern 110 8870 18800 20700 125000 163000 206000 Continued on page 68 RADIO FOR SEPTEMBER, 1924 19

www.americanradiohistory.com A Single Control Regenerative Receiver A Selective Set for Broadcast Wavelengths, as Simple in Construction as in Operation By Paul Oard

THERE has been a growing tend- a type that will function over a broad If amplification is to be used, the ency upon the part of radio band of filament brilliancy, as their bril- rheostat should be heavy enough to carry technicians to stress the impor- liancy is dependent upon whatever volt- the current for three tubes. With the tance of the development of a receiving age the detector rheostat is set. The use of one UV -200 and two UV -201A instrument which would incorporate but UV-201A and C -301A tubes are tubes, 11/2 amperes are drawn. The one tuning control, yet which would highly satisfactory for this purpose, as average rheostat will just about handle function as satisfactorily as those types they seem to work at all voltages be- this amount, while one with a heavier which make use of from three to five tween four and six equally well. The winding will allow some margin of controls in effecting changes of wave- safety. length. The writer offers the circuit Fig. 1 shows the circuit with detector diagram of an instrument which meets .00025 tube only, and Fig. 2 the circuit with such requirements to a satisfactory ex- two stages of amplification. The pri- tent. But one tuning control is re- mary of the first amplifying transformer quired, both changes of wavelength and should be shunted with a small con - regeneration grid condenser is O.K. In being taken care of by the STANOARD TYPE denser-a tuning control dial. Only one rheostat VAR/OME TCR Fig. 2 an "off- and -on" sñap switch may is used, whether or not amplification is be placed in each amplifier filament cir- used. With two stages of amplification, cuit, or filament jacks may be substituted the circuit gives satisfactory results with .0002r to allow the current to be switched off regulation loud speakers, and, tube for when the amplifiers are not in use. tube, the circuit will afford results com- Once that an instrument making use parable to any of the standard single or of the circuit has been constructed, three- circuit regenerative receivers now tuning offers little difficulty. The vari- in use. By no means least in value is ometer dial is rotated, with detector the sharpness of tuning and the ease with brilliancy set fairly high, until the which interfering stations may be separ- -I1I1I1I1I1I carrier wave is picked up at its loudest ated. The circuit is equally effective on point. The detector is then cut down voice or on còntinuous wave. until signals are clear. Caution should 1. Hookup Fig. for Single Control be observed, however, as circuit is One thing should be borne in mind, Detector this this circuit is not for use on waves be- a persistent oscillator, and will radiate low 300 meters. Below this band, the detector in this case should be a UV-200 strongly to neighborhood receiving in- filament of the detector tube must be or C -300. The WD11 "peanut," ÚV- struments. As before stated, the sharp- burned at excessive brilliancy, the value 199 and C -299 tubes may also be used, ness with which the circuit tunes is re- of inductance in the circuit being insuf- both for detection and for amplification, markable, and it will be found possible ficient to allow of regeneration. but, in the latter instances, with some- to tune in one station after another, The tuning element consists of a sin- what decreased volume. once the detector is set, with only this gle variometer, of the type used in many The antenna series condenser is of one dial. three -circuit tuners, any one of a num- very small capacitance, in the nature of The circuit diagrams are self- explana- ber of which now on the market will .00025 mfd. The standard type of grid tory. A single -wire antenna of not more prove satisfactory. On average anten- condenser is just the thing for this pur- than 100 ft. in length will be found nae, the circuit will tune between 300 pose. Nothing is gained by using a right for reception, and a height of from and 600 meters, sufficient to pick up the larger capacitance. 30 to 40 ft. will give gratifying results. majority of broadcasting stations. No design of instrument arrangement is given, this being left to the constructor. No particular difficulties are present here, however, and the average material to be found in the radio workshop may be used. It is important that the finished instrument be well shielded, as it will be found very sensitive to body capacity if it is not. Leads should of course be short, and it is important that the rheostat should be one allowing of smooth, even variation. I' I' I' 11' 1' 1' 1' 1 - (' + If amplification is to be used, it is important that the amplifying tubes be of Fig. 2 Hookut' for Single Control Detector and Two Stage Amilifier 20 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com A Variable "B" Battery

By David P. Gibbons As Denny gathered up his bundles and all real estate men are optimistic, he didn't particularly relish the hike to IF to go, the stranger asked "How then the Los Angeles realtor can the little shack a half mile above Miller's started soon the train to Los Angeles he come ?" only be described as a super-op- Camp, where he and his friend Joe - His pronunciation of "Los Angeles" timist. Certainly the gentleman who Knapp were spending a month's well added one more to the sixteen different founded Citrolia was one. A flat, bar- earned vacation after two years of con- a wrong ways of pronouncing that name. ren stretch of rocky soil near the foot tinuous wireless operating over many deep. "There's one that stops here that of Mount Baldy, about twenty miles mile of the well -known billowy be along in a few minutes," city, was to him "the ideal Stepping into the gloom of the little ought to from the Denny. The other muttered suburban development," and, with the waiting room, he began rolling a cigar- answered his thanks and Denny set out on his up- object of making the desert boom, he ette, laying beside him on the bench the hill hike towards Miller's Camp, idly staked it off into lots and plots, marked few packages he carried and which day speculating on the identity of the foreign - them off with gaudy flags and bunting, represented his purchases during the looking stranger and his business at Ci- and then tried to pass them off on a in Los Angeles, -two new radio maga- a trolia, as he was personally acquainted gullible public through the liberal use zines, a supply of smoking materials, every member of Miller's Camp newspaper half pages and superlative couple of newspapers, and a new 45 -volt with of and there were no other houses nearer adjectives. He built a two -by -four sta- B battery. Pomona, five miles away. The tion on the electric line that ran nearby As he struck a match, he was startled than at the Camp and from there and surmounted it with a triumph of the by a movement beside him and a sharp, road ended a rough trail that led to signpainter's art that proclaimed that high -pitched voice asking "Vili you pliss he followed two -room bungalow where he and here was "Citrolia-the suburb superb." gif me a light ?" He had not noticed the taking life easy. When he ar- The flags fluttered fruitlessly for a the other occupant of the bench and, as Joe were rived Joe had a cheerful fire glowing in forlornly ; the few feeble the match flared up he glanced curiously time and faded engaged around the wooden plat- at him while he held the flame to the the sheetmetal stove, and was flowers planted but unavoidable task form by the track faded dejectedly, and stranger's cigarette and then lit his own. in the unwelcome dishes, concluding which, the florid advertising faded suddenly The single quick glance did not reveal of washing the his companion the two partners settled themselves and completely ; leaving nothing of much of - were soon im- Citrolia but the tiny waiting room which a dark soft hat concealing comfortably and little depot. the upper features, a mersed in the new magazines. comprised the - method up the slope of the heavy jaw with a thick (//// Like all radiobugs, their A mile further radio mountain was Miller's Camp, a cluster black mustache, and a /¡ of reading a v / was thor- of miniature bungalows whose occupants large white hand, with magazine ¡ ¡ h and exhaustive, gave the interurban trains their sole ex- one of the fingers missing, oughou line nor a dia- cuse for an occasional pause of a few which held a cigarette with a nor an "ad" seconds at Citrolia. Usually they didn't a long paper mouthpiece. gram even hesitate, and the one from Dwyer ,swung him- I which Denny I self early one winter evening il barely slowed down sufficiently to allow him to hop clear, before rapidly disappearing in the gather- ing darkness. A chill breeze was blowing and

"Denny was pointing at it in open- mouthed astonishment." RADIO FOR SEPTEMBER, 1924 21

www.americanradiohistory.com escaping a critical scrutiny, and their from the university at about five o'clock Couldn't be any mistake comments were both about that frequent and that evening to find his Chinese servant voice, could there ?" caustic. lying unconscious on the library floor "Hardly," agreed Joe, "It's what you "Here's a bird," remarked Denny, and the package with the precious ele- might call a highly individual voice al- "who claims there's no such thing as a ment missing from a small wall safe right." noisy B battery ! Can you beat that ?" which had been broken open. The an- Denny swung the dials back to KH J's "Yes," answered Joe, "a goof here nouncer continued : wavelength and a canary trilled as Uncle says he brought a dead B battery to life "So far there is no clue to the identity John announced : further particu- by heating it in the oven !" of the criminal, "- as the Chinaman, whose lars of the Pomona radium robbery. "Well," said Denny judiciously, skull is believed to have been fractured, The Chinaman, recovering in the hos- "there might be something has not yet regained in that idea. consciousness. The pital, told the police he had been clean- 'Spose we try it with old value of the radium is placed that one in at $20,000, ing up in the library when the door was the set ?" and the glass vial containing it was en- cautiously opened and a heavily closed in built, The "set" referred to represented a small hardwood box, lined well dressed man entered and with several without their combined junk piles and was scat- layers of shet lead. And warning rushed towards him now, Friends and hit him tered in apparent disorder on a large of Radioland, our good' a crushing blow on the head with table friend Senor some in a corner. The different parts Matamoros Chihuahua heavy weapon which he drew from will give you his were wired together in a maze that the news of the day in pocket. The injured man's description would have Spanish." wrung a cry of anguish from of his assailant is fairly complete and in- any of the embryo This the sonorous Marconis, whose senor proceeded to cludes the fact that the robber had a superhumanly neat receivers do in a resounding adorn the cascade of vowels rather sallow complexion and a thick and picture pages of our popular periodicals. consonants that must have put quite black mustache. Fingerprint experts Disconnecting a severe the old B battery, Denny strain on the microphone in who have examined the safe declare that gave it the studio, the heat treatment as directed while Denny turned the the burglar had the middle finger of the and knobs to see was rather surprised when replacing what else was on the air. right hand bandaged or missing, and the it to find it had recovered at least some The Catalina radiophone was still in police are confident that his capture and of its original pep. operation and could usually be relied on identification will be swift and sure. "Guess we'll save this new one for a for a few minutes entertainment when- The University authorities, nevertheless, couple of days," he said, as he placed it ever a broadcaster's program fell flat, so have offered a reward of $10,000.00 for under the table. "I scratched the date tuning it in they heard the operator get- the recovery of thé missing radium." on the wax when I bought it today, and ting a connection to the St. Catherine After a forecast of the next evening's I want to see how long it will last." Hotel on the island, and give the parties program, the announcer concluded He his tuned in KHJ just as a song -plug- the signal to go ahead and talk. day's work with an emphatically cheer- ging tenor was tearfully bemoaning his "Hallo! iss dat Mister Pedersen ?" ful "Goodnight, everybody !" utter lack of bananas. This seemingly came a high -pitched male voice, and an- "Goodnight !" repeated Denny, and world -wide stoppage of the banana indus- other voice, slightly weaker, answered then addressing Joe, who had again be- try had long since lost its news value to from the island, "Yes. That you, Ivan ? come absorbed. in his reading, "Hey! did both Joe and Denny. Five months previ- How you did make out ?" you get that ? Ten thousand dollars re- ously Denny had been apprised of the On hearing the first. speaker Denny ward and we know the robber ! All shortage by a group of Pierrots at Manly became suddenly alert and distracting we've got to do is hunt up that fellow I Beach in Sydney, and a month later at Joe's attention from the reading in met at the station, turn him in and col- Zamboanga a couple of callous young which he was absorbed, he said in a lect the cash!" Moros repeated the sad tidings with evi- rapid whisper : Joe was more skeptical and less liable dent relish while they paddled their ca- "Say, that's the guy I told you about to be stampeded by the enthusiasm of his noes round his ship and dived after the that was waiting for a train into town as partner. "ha'pennies" and "thruppeny bits" which I came up." "Oh ! that's all, is it ?" he countered, the crew had been unable to get rid of at Joe, unimpressed, said "Think so ?" "Well, that's all about twenty thousand the last moment in Australia. Joe was "I know it," asserted Denny. "You other listeners-in have to do, too. Be- in London at a music 'all when the news don't hear two voices like that in one sides, where do you get that `we' stuff ? of the disaster leaked out through the day. Listen !" I'm not personally acquainted with your carelessness of a solemn English come- A slight interruption on the line -they criminal friend, you know !" dian, and a week later, in a beer hall on did occur occasionally- caused the man "Don't you want some of that wad of the Scheedam -Scheedijk in Rotterdam, addressed as Pedersen to repeat the ques- easy money ?" Denny demanded re- he listened once more to an account of tion : proachfully. "If you and I grab this the universal famine in the succulent "How did you make out ?" and both fellow we'll go fifty -fifty !" fruit of the tropics as rendered by a Joe and Denny were listening closely as "I'll take fifty centavos for my share group of heavyweight Dutch ladies who "Ivan" with the odd foreign accent re- right now," said Joe, failing to get ex- composed the local orchestra. plied : cited. He proceeded to throw more cold The singer, at least, seemed to be en- "Yess. I got id, but I haf some trub- water on the other's ardor by telling him, joying himself and was piling on the bil ven I -" "You may be an Al wireless operator, agony by repeating the chorus, when he "Never mind that !" sharply cut in but you were never cut out to be a was interrupted by the hearty voice of Mr. Pedersen. "Don't talk over this Sherlock Holmes or a Craig Kennedy. the announcer saying: phone. People can hear you. Come Better leave that kind of monkey busi- "Friends of Radioland, we have just right over on the first boat in the morn- ness to the people the Lord created and received a startling news item of local ing and bring it with you. The money the city pays for that particular purpose." interest," and he then proceeded to give is waiting. Understand ?" Denny subsided, but was unconvinced. the details of a sensational robbery of a Ivan signified his agreement, and a He felt positive that the man who had quantity of radium from the home of moment later both hung up their re- asked him for a light in the little wait- the well known scientist, Professor ceivers. ing room at Citrolia was the thief who Mayora of Pomona. The professor, "Kinda funny," remarked Denny, had assaulted the Chinese servant in the who was a specialist in the medicinal hearing that fellow on the air after talk- home of Professor Mayora and stolen use of radium, returned to his home ing about him a few minutes ago. Continued on page 50 22 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com Radio Construction Pointers A Series of Practical Suggestions for Applying Scrap Material to Useful Purposes By Paul Oard Making Insulated Wire tip and remove the broken piece of tinsel, when adjustments are at a critical set- put a drop of solder in the tip, and place ting. wire may be so in- BARE copper the newly -wound cord end in the tip A form of contact most commonly as to serve the same pur- sulated while the solder is still melted. This is used to offset this is the familiar pigtail wire in the con- pose as enamelled the method used on most factory jobs connection, but while this is effective, it through a simple structor's workshop, and, if properly done, is as good as new. is open to the objection that stops must process. The bare wire is laid out and be used to prevent rotation beyond a stretched to remove kinks. A small Terminals for Flexible Cord certain point. of shellac, well thinned with amount STRANDED lamp cord finds an im- A contact that permits constant rota- alcohol, is placed in a tin or earthen- self clean- portant place in many wiring jobs, tion and which is thoroughly ware dish. A small piece of cotton is ing, is illustrated in Fig. 1. A few as in portable sets, and for A and B bat- used to press the wire down in the dish, or hardened copper tery connections and for pigtails. As a inches of spring brass the constructor walking slowly along the 18 gauge; is wound rule, however, a neat job of soldering wire, of about No. length of wire until the entire length has tightly around the rotor shaft for about is difficult as the insulation frays at the been coated. By regulating the pressure end is left straight for an ends, and the strands of fine wire refuse in. One of the cotton wad against the wire, the spring coil is removed to take the solder well due to slight cor- inch or so. The thickness of the coating, as well as the with a pair of round rosion from the sulphur in the rubber from the shaft and smoothness of application may be regu- is somewhat smaller coating. nosed pliers made lated to a nicety. After allowing to dry, of the shaft. It is A neat and effective method of finish- than the diameter a second coating may. be applied for back on the shaft, the ing the ends of such wire is to wind then forced heavier insulation. being so fastened that some from 4 to 6 in. of No. 22 bare copper straight end While such a job will hardly be the wire, soft drawn, around each terminal. resistance is offered. equal of the factory made product, it the convolutions Start in. from the point where the Due to the fact that will prove satisfactory for experimental / of the spring form a screw thread, there insulation is removed, wind first over the work. If one can secure a small amount wiping action as the insulation, and continue, over the bare will be a constant of lacquer, such as is used to coat brass is that will tend to stranded wire. The finished job is given rotor shaft turned and silver to prevent tarnishing, and ap- keep the shaft bright and clean. Only a coat of solder. The frayed end is now plies it carefully to bright shining wire, plenty of spring and covered over, and the job looks much wire that possesses a really neat and effective job may be tension should be used. On condensers like a standard cord tip. Furthermore, accomplished, the bright copper showing do not have sufficient projection of such a terminal will last much longer that through the lacquer, which will afford shaft at the back, the spring may oft - than if the ordinary connection had been insulation sufficient for receiving induct- times be secured at the front between the made, as the wire can not bend sharply ances, or wherever low voltages are used. and the condenser end plate. at the point where the insulation had main panel The use of such insulation in radio re- been removed, as the jacket extends back ceiving circuits is open to the same ob- ß Substitute for Spaghetti the insulation itself, gripping it se- jections that apply to enamelled wire, over OPTICAL houses handle a small The solder serves to make a but for many circuits it will suffice. curely. white rubber tubing that is used to metal binding the turns Likewise, copper or tin foil may be solid terminal, slip over the frames of eyeglasses. This effectively. coated with shellac instead of using mica together material, which is not costly, makes a or paper as a dielectric in small fixed A Self- Cleaning Contact good substitute for spaghetti or empire condensers, as in grid or by -pass jobs. PRACTICALLY every constructor tubing. area of plate The capacitance for a given knows that a spring contact on a A Swab for Removing Solder- high in such an in- surface will be very rotating shaft, as the rotor of a con- ing Flux This is not suitable for high stance. denser or variometer, will sooner or later HEN using a soldering flux of voltages. give trouble due to dirt working in be- W the grease type, which contains Soldering Tinsel Cord tween the point of contact, or to cor- a certain percentage of acid that will in point. Espe- course of time, telephone rosion of the metal at this due course of time cause corrosion of IN THE in regenerative circuits receiver cord tips let go and the ex- cially is this so metal parts behind the panel, it is ad- be removed. perimenter is faced with the necessity of To connectióna visable that all excess flux soldering them back into their rightful A package of "pipe cleaners" sold by , »g for place. This looks easy, but is not. The Sp tobacco shops, make excellent swabs visible cords are composed of tinsel, which this purpose. After removing all brush stands neither the heat of the iron or flux, dip the swab in alcohol and soldering fluxes. the soldered joint vigorously. This will Push the cord back about an inch and take care of corrosion. i111111FlitIllillrf ¡I SAfaft carefully wind the tinsel with a short Níiiñ! Home -Made Insulators No. 36 bare copper wire. length of THE construction of insulators, both from a Ford spark coil is That removed for receiving and transmitting ap- enamelled or insulated, 111- satisfactory -if 1111111 nnnnnt; paratus, offers little difficulty. It is may be removed by passing through this not generally known that locust wood an open flame. Apply a mild soldering h4P../ is used by one of the largest commercial flux to the completed job, heat the cord A Self-Cleaning Contact RADIO FOR SEPTEMBER, 1924 23

www.americanradiohistory.com radio transmitting companies in the guy cables of their antenna masts. Dry wood Proper Care of Storage "A" Batteries is for the most part a fair insulator, the only problem being to keep it dry dur- By H. A. Fischer ing wet or foggy weather. Wooden in- The average radio fan . sulators that will render efficient service thinks of a The top of the plate should storage battery as an awful always may be constructed on the following monster that be covered with about ip, of should be kept in a cage with / water, plan. wild ani- this being added before rather than after mals. He believes that it will eat A strong screw eye is secured in each rugs, charging, so as to get a correct gnaw holes in the floor, and hy- end of a piece of hardwood 6 in. long inconveni- drometer reading as to the state ence everybody. Yet, if properly of the and about 1 in. in diameter. Hoe, rake in- battery. stalled, it is his best friend, and shovel handles furnish excellent for storage The hydrometer is a glass syringe battery tubes give louder hav- round stock for this purpose. After and clearer ing a rubber suction bulb on signals without the inconvenience the upper making up the necessary number, they or ex- end and a small rubber tube on the other pense of changing wornout dry cells. are boiled in linseed oil for a half hour A end. Inside the syringe is a glass float Saturday afternoon spent in arranging or so. Suçh a treated insulator will weighted with shot at its lower end. battery equipment is time well spent. The upper part of the float is calibrated The most necessary accessory is a and marked for reading. To take a read- charger for changing the house alter- ing, draw enough of the solution into nating current to direct current for the the hydrometer so that the float floats storage battery. It is not only less ex- freely. The reading shown gives the pensive than charging at a battery sta- state of the charge, which is somewhat tion, but also the battery can be charged as follows in the case of a lead battery: intermittently so that interesting pro- 1275, fully grams charged ; 1250, 80% may not be missed. charged ; /2 1225, 60% charged ; 1200, If the radio set is installed on .ba// >` the first 40% charged; 1175, .SYrips of .64.4-ehi,! i¢ av floor, 20% charged; 4 W/a.t by 72" wide the battery and charger can be 1150, exhausted. placed directly underneath B and feed When the test shows a reading below wires run through the floor. Erect a 1175 it is time to give the battery a re- swinging shelf from the cellar 10 --- o. d.7// beams charge, until, by successive readings 72 underneath the set, mounting of an upright the hydrometer, it shows full charge. board to hold the change -over switch 4-0/.°Z Test each cell separately and be sure to C Dovb /e - Po/e Dovb /e -Throw S'w/fch ¡` . -`J/////// ,w r `L ooaece and .dr'dmd To house wiry w,/ñ D or'. ends fine To see Horne-Made Insulators s 4- A, Hardwood Strain Insulator. B, Bakelite Antenna Insulator. 0, Receiving Antenna Ft/se Insulator. D, Rope Insulator. B/oCif Cha take care of itself nicely in rainy wet weather. This is preferably used as. a Storage Bari/Pry str insulator in the guy wires of transmitting equipment. The screw eyes - should have deep long threads and be Fig. 1. Battery Charger Hook -up firmly set in the wood, otherwise' grief and fuse -block, unless it is will result. decided to return the acid withdrawn into the hy- have this close to the set. A strain insulator, suitable for instal- drometer into the cell from which it was Fig. 1 shows a circuit lation in transmitting antennas, diagram with taken. may be a double- throw, double -pole made from two strips of N. in. bakelite, switch The vent plugs on top of the cells whereby the battery may be either in %2 in. by 12 in., should be removed while charging, fastened together as use or on charge. to illustrated. Such an insulator possesses allow the gases generated within the A well -kept battery needs excellent insulating properties and only cells to escape freely. will charging and a monthly addition stand a strong pull. The of dis- Batteries should not be allowed to constructor tilled water. This may may elaborate on this idea be purchased freeze, as this may do permanent internal to meet vary- from a battery- charging ing conditions. station or may injury to the cells. The following table be made with improvised equipment gives Strips of in. bakelite Y8 by the freezing points at various states / 6 in., found around the kitchen. A teakettle with an 8/32 hole bored at each end of the. electrolyte: of boiling water, a length of clean gar- make excellent insulators for light single den hose, a clean can and a pan of cold 1100 freezes at 18 degrees above zero wire receiving antennas. Usé % in. 1125 freezes at 13 water constitute the "laboratory equip- degrees above zero bakelite for heavier wire and long spans. 1150 freezes at 6 degrees above zero ment" necessary to produce distilled 1175 The bakelite should be polished on a freezes at 3 degrees below zero water. Assemble this outfit 1200 freezes at 16 buffing wheel if possible. as in Fig. 2. degrees below zero One large 1225 freezes at 34 degrees below zero commercial company tnakes use of con- 1250 freezes at 60 degrees below zero siderable of their scrap bakelite in this 1275 freezes at 83 degrees below zero manner. Keep lighted matches away from cells Rope clothesline, of the quarter inch while charging, as the gases may ignite. variety, in 1 to 2 ft. lengths, boiled in Keep the battery in a dry place and wipe paraffine wax or linseed oil, makes a away moisture which collects on top .good insulator for receiving antennas. during charging. If the terminals cor- The ends are looped and bound tightly rode or bluish-green deposits collect on with wire. Fig. 2. Distilled ¡Vater Plant Continued on page 64 24 RADIO FOR, SEPTEMBER,. 192-41.

www.americanradiohistory.com A Homemade Synchronous Rectifier This Gives High Voltage Direct Current from 6o Cycle, i i o Volt Alternating Current By Geo. Becker, Jr., 6BIP

THIS "sink" was constructed by The stator can be built up to any WOOOEN 13Ox M04/LO the writer two years ago and has design, but, if the builder has the field rio given good service since. The of an induction motor, the job is simpli- motor is simple and can be made with fied greatly. For best results, the tunnel few tools if the constructor has access to should be as close a fit as possible. Only a lathe. The cost of the motor will two field coils are used ; see Fig. 3. depend on the amount of "junk" the Under the assumption that the builder ham has in the old box. It should not has such a field, we proceed to saw out exceed $10. all the poles, or teeth ; but four on op- COrVNEcT/ON 7'0 COMM v TATOR

Cf/EvROL E r

F /LL TAR.? ., Ac/ W/ Tee Mgt TOO LLAC ARMA TuRE Fig. 4 and through the middle slot of the pole \ pieces. R/MG Bearings and base can be made of BA 86A!//V6 pine, though oak or other hard wood is preferable. Fig. 5 shows an optional Fig. 1 design of the bearings, but the builder First get a Chevrolet generator arma- posite sides of the frame. See Fig. 3. can use his own ideas about these, as the ture, which is ideal because it has an The field coils should next be form - only requirement is that they be rigid. even number of segments in the commu- wound and taped before putting on the (.346/6 RIP FOR tator, the shaft on the commutator end projecting poles; 250 turns on each coil BEAR /NO is fairly long, and the other end has a .T 1w APART 7/16-in. hole in which the disc can be easily mounted. Standard Ford or Chevrolet ballbearings can be used to make it run easier. Then turn up a piece of Formica / in. thick, 1% in. in diameter, and bore if- it for a press fit to the commutator end of Fig. 5 the shaft. Get an old bronze bearing with an inside diameter slightly less Mount them to the base with through bolts so there will be no danger of than 1 / in. and a wall thickness of about 3/16 in. Bore it out in a lathe, shifting when the power is applied. making it a press fit for the Formica The disc for the high voltage will be core. Press the ring on the core and, SAW OUT THESE POLEJ next considered. Get a piece of Formica before pressing ring and core on the Fig. 3 6 in. in diameter, / in. thick, and roughly saw it round and mark the ap- shaft, solder a short piece of wire on of No. coils are 22 D.C.C. The two proximate center. Next chuck a piece any one segment of the commutator and connected in series and the terminals to of cold -rolled stock about 13A in. in ground it on the shaft. The reason for the 110 -volt supply. be press diameter and long enough to allow about this will seen presently. Now If the field has no base, one can be the ring assembly on core, up to a 4 in. to project. Turn up a shaft as per the made easily as per Fig. 4. A box is point in. from the commutator. Fig. 6, 7/16 in. in diameter and 3 in. 3/16 made as deep as the stator is thick, with Set up the between centers in armature a snug fit on the sides. Molten lead can a lathe and - turn the ring down care then be poured in the space between the SL /P R,,ve COMM(, TA ro R stator and the side of the box. See Fig. 4. After the lead has cooled, the box EXACT TyE OPPOJ/TE SEG^ICNT can be knocked away and the stator and 9r0g/.VOCO casting removed. is Tb SMAFr This makes a very D/SC SHAFT solid mounting for the is H41-7 stator and to Fig. 6 be preferred to wood blocks. The whole cSOLOEA' NERE field assembly can then be held firmly to long, with a flange 7 in. thick and 172 FORM /C64 the base by a strip of metal passed over in. in diameter. Do this very carefully, Fig. 2 the top and screwed down on each side. as the face of the disc must run perfectly fully. Connect the segment exactly op- The coils should be mounted on the true. Drill three holes for the mounting posite the grounded one to this ring. projecting poles and held in place with screws on a radius of / in., using No. See Figs. 1 and 2. small dowel rods passed over the coils 19 drill for 8 -32 machine screw. Drill RADIO FOR SEPTEMBER, 1924 25

www.americanradiohistory.com three holes to correspond in the Formica a diameter. Connect the slip rings to tery to exciter. You'll be the one that's disc and bolt the disc to the flange. the bronze ring' on the disc, one ring to excited.. There are voltages induced in Chuck the shaft and roughly turn the each segment. This may be done by the armature that'll make your tubes go Formica disc true, being careful not to soldering the connecting wires to the west at a rapid pace. Don't use the bend the shaft. The hard bronze ring screws that hold the bronze ring on. same voltage as you did with the old that acts as the commutator can be cut Selection of the brushes is left to the "slop" rectifier. from a sheet, or, better yet, turned from builder and the contents of his "junk" Shift the d.c. brushes around till you a large -cored piece of bearing bronze. It box. The pictures will give an idea. get a position that delivers the high volt- should be / in. thick and about / in. Their purpose is as follows: Two age without sparking. This rectifier wide. It must be faced off on both sides brushes ride on the armature commu- does not look like a pin -wheel. After arid, when finished, should be 5Y2 in. tator and are shorted together perma- everything is adjusted, only a little oil outside diameter and / in. x / in. nently. They must be 5/16 in. x / in., and an occasional adjustment of the high Mount it on the Formica disc by means or even wider. Two / in. x 7 in. voltage collector brushes is necessary. of six 8 -32 machine screws passed carbon brushes feed the high voltage to through the disc and screwed into the the slip rings on the disc shaft. Two strip brushes collect the d.c. from the disc. One / in. x / in. carbon brush feeds the d.c. exciting current to one i segment on the motor commutator ; the other side coming out through the shaft.

\Machine very corefa //y a// over Saw 'Wee ye; s /ifs offer o// n/ochminy /s finished Fig. 7 bronze ring. The screws should be spaced as per Fig. 7 and countersunk on back of the disc. the Assembled Kiew of Synchronous Rectifier Next, get a piece of Formica in rod The Assembled Rotor form in. by 2 in., or use three or four For operation, 110 -volt a.c. 60 -cycle Y I will be glad to furnish any addi- %-in. pieces, bore it out to a press fit is connected to the field coils. The tional information that anyone wishes. for the shaft 7/16 in., and turn the out- brushes on the commutator being Write me care of RADIO. side and face the ends. Make two rings shorted, the motor acts as a repulsion of bronze / in. wide, / in. thick, and induction motor and comes up to speed inside diameter a press fit for the For- rapidly, the speed being limited only by HANDY HINTS ON RADIO mica core. See Fig. 8. Press the rings friction. When the speed reaches 3600 By D. B. McGowN. r.p.m., the exciting current is connected A common, but little suspected source Bronn o -inys to the shaft and slip ring and thence to of noise in a receiving set can often be opposite segments of the commutator, traced to "microphonic" contacts in the where it divides and flows through the filament rheostats. Be sure that all the armature by two paths, producing two moving parts of these instruments are magnetic poles, a north and a south, at clean. Wine hole opposite sides of the armature. This If the landlord will not let you bore Fig. 8 rotating magnet falls into step with the holes in the wall for a leadin, and a a.c. and the motor acts sychronously. window is handy, paste a sheet of tin- on the core, one on each end, and press A.c. fed in at the two slip rings on the foil on the outside of the window, and the assembly on the disc shaft. Don't disc shaft can be taken off as pulsating another on the inside. This will form bend the shaft. Press it on to within d.c. at the disc. a perfectly insulated series condenser, 1/4 in. of the flange. Bore a hole through This motor always starts right side and a leadin as well, without damaging the core so a wire can be run through to up, no voltmeter and change -over switch anything in the slightest. the second ring. Press the shaft in the being necessary. To find the approxi- If you are using a detector tube for 7 /16 -in. hole in the end of the armature, mate position for the commutator reception, and after a while the signals after first putting on the ballbearing. brushes, set them at right angles to the get weaker, in spite of a good tube and Pin the disc shaft in the armature shaft field coils and then either shift the new batteries, remember that the mag- with a through pin and set the whole brushes or the field assembly until the nets of the headset may be getting weak, thing up in a lathe. shorted brushes do not spark. The and if they are this will reduce the The commutator end can be gripped brushes lag slightly. To find the ap- volume considerably. in a chuck or placed on the live center proximate position for the disc brushes, Interference from battery- chargers, and driven with a dog. The bearing connect both the exciter and fields in motor -generators, and similar apparatus on the disc end should be clamped in a parallel to a 6 -volt battery and the arm- often carries along the power lines for steady rest as near on line with the ature will turn so that the poles in it considerable distances, and sometimes centers as possible. Proceed to turn and those of the field line up. Set the causes trouble in places considerably re- everything to a finished surface, es- d.c. collector brushes about 5 degrees mote from the source of trouble. pecially the disc and bronze ring. Turn ahead of the center of each segment on When using an oxide filament detector the whole disc so as to balance it. After the disc. Hook it up and press the key tube, such as a WD -11 or.WD -12, or everything is turned to a whisker, re- (low power) if the milliameter says, and a Western Electric tube, after the tube move the disc and armature from the reverse the d.c. leads to the plate and gets very old, even though the filament lathe and saw the / -in. slots in the try again. It should work FB now. looks pretty good, it may lose a good bronze ring at exact opposite points on Two cautions : Don't use an A bat- deal of its sensitivity, due to age and use. 26 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com A Good Filter for the Amateur Transmitter Practical Details Regarding the Selection of Con- densers and Inductances and their Proper Hook -up Cassimer William Rados series have to be used for 800 to 1000 THERE is a great deal of uncer- The glass plate is easily made, never a capacity of from tainty and argument about filters "blows" but is too big for the required volts. As this gives is a desirable condenser. to smooth out rectified a.c. into capacity. It is also apt to have high 10 -15 mfd. it is not These condensers if punctured can be pure d.c. The more it is studied and losses if made incorrectly. It and so used over and over. experimented with, the nearer we come used to any considerable extent for these formed again article in RADIO gives com- to the day when all amateur stations will reasons. A recent in plete details on construction of an elec- use pure d.c. The filter question is not The paper condensers are the ones One made up in the to settle and it is hoped that this greatest use today. They are compact trolytic condenser. easy manner was used at 1BEL article will help the average operator to and cheap but "blow" at awkward mo- following 5 (50 watts, 1500 volts rectified a.c.) for get a good filter. With a little hard ments. For transmitters using watters and worked very sat- work and patience many so- called filters with not more than 1000 or 1100 volts, a considerable time isfactorily, giving no trouble and needing now in use would give real d.c. instead the R. C. A. 1 mfd. 1750 volt d.c. con- account of surges it no attention. Six aluminum plates about ? ?. To the real amateur the biggest denser is ideal. On of were stacked, separated argument in favor of pure d.c. is that is best not to use this or any other con- 6 in. diameter buy- by glass rods. In between they were this kind of note is easier to copy when denser at its rated voltage. When a saturated solution of qrz, and will cut through qrn and qrm ing a condenser get the one with the filled with The plates were con- better than other notes. A transmitter highest voltage rating and do nr t expect sodium phosphate. up very long nected one to another (in series) and 5 watters with a pure d.c. note a paper condenser to hold using top and bottom be reported and worked at if more than three quarters rated volt- leads brought out from will often was then greater distances than a 50 watter with age is used. If the voltage of the trans- plates. The whole arrangement they immersed in oil. an ordinary note. mitter is too high for the condensers To build a good filter knowledge of will have to be put in series. This is an is safe. It has the parts is necessary. The two parts expensive method but conden- are the condenser and the inductance. been my experience that paper sers that have been "blown" can be put a is put across in series and used on same voltage, or WHEN condenser Inductance. "A" is be across line directly if Fig. 2. Effect of the line it smooths out humps they can put the curve; "B" the inductance curve and holds up the voltage by storing up lower voltage is used. Condensers used energy in electrostatic form. A con- in spark coils will also work well. The On all filter condensers it is well to denser across the rectified a.c. before it disadvantage of the paper condenser is put a small fuse in series with the con- goes through the inductance will almost that it is expensive for large capacities. denser. If the condenser "blows" the double the voltage on the plate. (Fig. To get 'a large capacity we must use high voltage will not be short circuited 1.) an electrolytic condenser. However, they long enough to damage anything. A don't st'and high voltage so that two in fuse of about / ampere is satisfactory. /o1 THE inductance coil stores up energy in electromagnetic form which by the property of self induction fills in the Fig. 1. Effect of Condenser. "A" is the curve gaps between bumps of a rectified a.c. of rectified a.c. and "B" the curve. (Fig. 2.) As can be seen, using condenser curve 8 inductance alone, the effective voltage is less This is the reason that the antenna cut down considerably but we have tubes when a more uniform current goes up when ' we put a con- strain on the get enough denser across the rectified a.c. This 6 voltage is applied. To alone would be reason enough for using energy stored in electromagnetic form, it. But besides that, if the capacity is at a large value of inductance is necessary, least 5 mfd. it smooths out the curve at least 10 henrys. considerably. This gives us a wave At a well -known Eastern college sta- which approaches d.c. A condenser alone tion the voltage from the mercury arc if from 50 to 100 mfd. will give almost rectifier was passed through 100 henrys d.c. but this much capacity is too ex- in the positive lead, with 0.25 mfd. at pensive. We must use a cheap condenser. L In order to be of value as a filter condenser it must stand high voltage and have a large value of capacity. There are many different types of condensers 20 40 60 BO /00 /20 /10 used today, but we will consider only Curren e In Mi/l/CYrn,copres the cheapest ones. Fig.3. Inductance Values of 1.5 henry Choke RADIO FOR SEPTEMBER, 1924 27

www.americanradiohistory.com each end. This gave a pure d.c. note. In building inductances, use electrical you can afford. A good Good chokes up to 30 henrys are easily value is 30 sheet steel for cores, the thinner the mfd. at ends and available now and it is much the a 30- henry choke better to better. Paint each piece with japan and in buy one than to attempt thé middle. If you have several to make a choke tape core before winding the choke. small of that size. The values chokes, connect them in series and of homemade The thinner the insulation on the wire place between chokes are very apt to be the two condensers. If 500% off from the more wire can go into a given space; you the "calculated" value. Everything have only one condenser, place it that so use enameled wire if available. before the inductance. is associated with the choke (Fig. 6.) -the size of The air gap, if too large, is very air gap, the kind of core iron, the cur- wasteful, and, if too small, the filter rent through the coil, the insulation, etc. does not work very well. So make it -all affect the value of the choke. variable (remember the old Thor To show spark Load how widely the inductance transformers ?) and vary it while varies testing tobe) look at Fig. 3. This is the induct- until best results are obtained. ance curve Use of a well -known single coil, fibre end flanges on the coils and wind (a) Correc 1.5 henry choke of Eastern. manufacture. full. Don't the holes The rating forget in the of the choke was 1.5 henrys flanges for the inside and outside wires. at 100 ma. With practically no current Solder lamp cord leads to the ends as shown in the sketch and tape the coil well. ( Fig. 4.) Give the whole choke Lead (6) Incorrect Fig. 6. Correct and Incorrect Placing of One Condenser with Inductance Co.;:;) The it filter is the best all around At ;9", ha"r wires and 7./..ber //anyP Topa and can be used to smooth Solder toya7tife th %we, earn out a com- /f down ort coi/ oral mutator ripple or to smooth out recti- At 8; so /der eo farad' coi /. fied a.c. Dr. Banks in July, 1923, /amp cord. Fig. 4. Details of Inductance Construction RADIO also shows how it can be used with a synchronous rectifier. through it the choke measured 2 henrys. a coat of japan and dry thoroughly in The "modulascope," as invented by Then came the big surprise. As current an oven. It is best to get acquainted Mr. John L. Reinartz of 1QP, is a up to 20 ma was passed through it the with a shop electrician or armature very simple device to determine the inductance value rose rapidly until at 20 winder, as they are skilled at this kind filtering. See Fig. 7 for sketch and ma it was 10 henrys ! As the of choke work. diagram, details in QST. The "scope" approached its normal current rating its When choke is the finished, the best will work almost at once when it is inductance fell off until from 70 to 120 way to find out its inductance is to take connected, but, if any difficulty is met ma it was 1.5 henrys. it to some college laboratory. They will with, crowd on the voltage and use When such a variation exists in a probably be glad to do it for you and good variable condensers as recom- choke designed by a radio engineer, you may not charge you anything. This is mended by "kewpie." If you have a can see that the "calculated" values of the only reliable way, because, if 60 powerful transmitter, the "scope" homemade will chokes are not very accurate. hams took the same specifications and work by induction However, by merely placing the following information is built 60 chokes, there would probably it inside the helix. given so that a rough idea can be be 60 different had of values of inductance! After the "scope" is going, vary your the inductance value of chokes. air gaps, condensers, and chokes until (a) Acme 5 henry choke THE good old standby is the 7r cir- (special) the "scope" indicates pure d.c. Then core 5 in. by 5 in. and 1 in. cuit, a condenser at each end and square 6000 test with neighboring stations on phone turns gave 5 henrys at 500 ma. the inductance in between. ( Fig. 5.) . for any slight adjustments which may (b) 3 open Use as much inductance and capacity as core chokes, 4 in. long, be necessary. Remember, while in. testing, 3/2 dia., 500 turns No. 24 dcc gave to discharge the condensers respectively by a screw- 0.3, 0.4, and 0.5 henrys at driver, etc., before handling 100 ma. them, or Joao' one of them might send you to the land (c) A honeycomb 1500 -coil a with of temporary sleep. After your filter is closed core built around it gave 1.4 adjusted, lay in a supply of QSL cards henrys at 100 ma. - Fig. 5. ,r Circuit you'll need them. To calculate inductance L= 4,r2 N2r2m 1091 L-- inductance in henrys, number of turns, R.F.C. N. I.002 f- m = permeability of core, 7r = 3.1416, r = average radius of coil, 1= length of core. 000.5 For a solenoid, m = 1. Example -what is inductance of a coil 2000 turns on iron ring m = 1000, circumference is 150 cm. and radius 8 cm. L = (4) (3.1416)2 (2,000)2 (8)2 (1,000) (109) (150) = 67.3 henrys. Fig. 7. Reinartz Modulascope 28 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com Secrets on Successful Operation of Transmitting Tubes Impressions as to Why a One -tube Station Gets out Better than a; Multi -tube Transmitter By Don C. Ida lla ce needed. Take out who has done assume each to last one year. Supposing that which is actually MANY an amateur and gear of all work with one 50 he runs them in parallel, and they do extra switches, wiring, wonderful the inductance, meters, watt tube has been practically last one year. Under our plan he would kinds. Space wiring, keep it all clear of the panel he increased power. With this be just as loud by using one at a time, - lost since don't even use a panel, but build a a close check has been kept for thus getting two years' use from these in mind wooden framework upon which to years with the ultimate aim of help- two tubes. two us mount the part. If this type of con- ing transmitting amateurs improve their But he doesn't care about this -let one struction is good for a receiving set it sets. This article is to be a collection of say that he will) be content with most certainly must be good for a trans- created by experiences which year's operation. The thing to do then, impressions mitter where the voltages are high and been .gained in five years of is to overload the tube, singly, so it will have output the currents likewise very high. A good C. W. operation, even back to the large last but six months. Then the combined place for all this extra stuff is the attic. 3 kw. tube set aboard the U. S. S. will be greater and the total same. Have it around, have extra condensers, George Washington. The impressions, life of the two tubes will be the his station has worked tube, and anything else that has ac- only the last - two years In the meantime however, cover but keep it in the attic. The become the prevailing better and has become well known as cumulated, since CW has be clear, the connec- communication. one of the "big" stations. A few dis- radio table should method of amateur firm and solid and increased re- -How many have noticed that the man cerning amateurs have found this to be tions rest. sults will sure come to this type of sta- with one tube is as loud or possibly true -we want to pass it on to the the man with two tubes. The whole thing in a nutshell is just tion. louder than Practically all of the preceding ma- the record holders, the stations this -use one tube, whether it be a 5, 50 Notice has been general. Now we will made the great distances, and or 250 watter. Then load that tube all terial that have the 250 watt tube in particular. the stations that are best known for their you dare and all your pocketbook will discuss . The author has been asked by many consistent signals. Practically all of stand (the life reduces with overload) - what is the secret of the 250 watt tube? them are one tube stations. True some A safe plan is to build your transmit- are built. Many good 50 watt stations dropped out so- called 100 watt stations will also enter as the new low loss tuners ter upon the list. Some night ask one of Take everything out of circuit except Continued on page 66 these 100 watt operators to take out one of his tubes. Nine times out of ten he gets no weaker. Some times he actually gets louder. Possibly,more of the radiated energy goes out on one wave, possibly a greater proportion of the energy is going out on the main wave with less in the harmonics. We also find the one tube sets are sharper locally. 9ZT caused much more interference locally with 100 watts than with the present single 250 watt tube. This will also tend to support our statement that more of the actual output goes out on one wave and that one wave only. At 9ZT using two 250 watt tubes, the locals complain of QRM and every ninth district station can apparently be raised with a short call and other districts with difficulty. With one tube in circuit the locals seldom even notice the station on the air, and all districts are equally easy to raise. Others have found the same thing true. Tests with 5ZA, 6KA, 5EK, 9BAF (day time) all Radio Guiding New Mail Planes tube is distinctly as other on the indicate that one H. L. Swart, Radio Engineer at the Radio meters, these stations call each good as many, and usually the one tube Mail headquarters in the Post Office Depart- 3998 -meter wave, but shut down to listen minutes, for emergency calls. is louder. ment in the National Capital, with his 5 -k.w. every fifteen This chain of radio stations acts as an aerial If one tube is better, why not overload arc transmitter sei which is on duty twenty - a day. The flying field relay train dispatching system. It furnishes quick second tube as a spare ? four hours it and use the stations along the route, with headquarters at service for planes, transmitting advance In other words let us assume that the are all equipped with radio weather reports and orders to stations where Washington, their owner of a station has two good 50 watt telegraph transmission stations. Operating planes and pilots relieve each other on flight. tubes. Under ordinary operation let us on a working wave between 3500 and 3800 cross- country RADIO FOR SEPTEMBER, 1924 29

www.americanradiohistory.com Adjusting Your Super - Heterodyne How to Find and Remedy Possible Trouble in the Homemade Instrument By L. M. La Montagne

AFTER you have carefully wired tube in a socket, and see if it lights. If a number of whistles should also be up your super -het, as per speci- so, try this tube in each of the other heard as it is turned through its various fications, you may find that it sockets. values. will not "perk" at first. Such troubles Next connect the B battery, without The commonest faults of the oscillator can usually be remedied if you know the meter for the moment, and short the are : two few turns on the plate feed- what to look for. filament leads momentarily by inserting back (follow directions carefully) ; re- First be sure that your sockets and a screw -driver between the socket con- versed plate leads ; shorted or open coils, intermediate frequency transformers are tacts. If a large or unusual spark is or poor contacts ; or poor by -pass con- all right. Test out each instrument for produced, trace out the trouble. Make densers. With an open plate coil, no shorts, open circuits, or grounds with a contact for an instant only or the bat- space current will be shown on the .3Y. teries will be run down quickly. If the meter. Lack of oscillations is shown proper size voltmeter is available, it by little or no change in the meter when Pr ter. .-A" Sic. would be better to use it. If these dr- the grid of the tube is touched. The alt cuits test all right, place tubes in the filament adjustment, while not critical, sockets, leaving out the audio -frequency must be above a certain value for oscilla- CONTACT ones for the time being. tions to take place. I have found that Now plug the 'fones in Fig. I. Testing Secondary of I. F. Trans- the detector nine -tenths of the troubles in a super - formers. Primary Tested in circuit, and connect the meter in the het occur in the wiring of the oscillator Same Manner. plus B battery lead to the set. Take circuit. readings for each tube, and if there is Now if the oscillator and r.f. tubes pair of phones and battery as in Fig. 1 one that seems to give unusual values, are working properly, or 2. The transformers should give tune in signals, a discard that one for the time being. The and try out the loud and distinct click when the circuit tubes in various positions. tubes should all be tested in the same Some tubes are good r.f. is made and broken through both the amplifiers, some socket, as the position in the circuit will good a.f. amplifiers, primary and secondary circuits. If some good detectors, give varying space currents. and some distinctly shielded, test for grounds to the shield. no good. Test the potentiometer, if one is used Don't overlook your grid leak or con- ,3v. by turning the arm until a click or hiss denser or any by -pass condenser. They is heard in the 'fones, and noting the may be way off capacity, shorted or action of the meter as the tubes go in otherwise defective. and out of oscillation, for future refer - Cut out the by -pass condensers and ance. If no click or meter kick is ob- then connect them one by one until the served, check the r.f. wiring, and if ok is found. COO/TACT TO JN/Z o trouble The only test for these check the contacts on the potentiometer. condensers is a comparative one made by Fig. 2. Testing Secondary for Grounds. Test Primary in Same Manner. There should be a circuit between its listening to the strength of signals. Any three posts regardless where the arm is decrease in signals will show a defective See that the condenser terminals make placed. This is tested out by the means condenser, wrong capacity or incorrect good contact. A rubbing contact, if of battery and 'fones, Fig. 3. A grating position. Your meter will generally dirty, may not be good. In soldering, show up a defective leak, especially if its be sure that the wire isn't held mechani- value is low, for then a positive poten- cally but makes an excellent contact as tial is put on the grid of the detector well. Stray noises, very difficult to lo- tubes, and an abnormal plate (space) cate, frequently come from this source, current results. A little testing will especially if in the detector or oscillator show just what to expect. A reversed C circuits. Polish up all socket contacts battery will also cause a tube to show with an ink eraser. Rub the tube ter- an excessive plate current. minals on a clean piece of paper or Fig. - Testing Bristol board. The lead oxide film isn't 3. Potentiometer very deep and is easily removed. The noise as the potentiometer arm is turned --- {III IIIIIIIII1l iI- thoroughness with which the various in- indicates poor contacts on the wire, struments are tested may mean the dif- which should be cleaned by sanding ference between success and failure. lightly. If the r.f. tubes are oscillating, Now let us suppose that you have as- a distinct click will be heard in the 'fones sembled the set, and are ready for a try if the grid of any tube is touched with out. The writer has found that a meter the finger, and the meter will give an in the positive B battery lead to all the upward kick when the oscillations are tubes is one of the most helpful things stopped. M6TBIf for testing any set. The meter need not The next circuit to test is that of the Fig. 4. Method of Connecting Meter be calibrated, but may be a high voltage oscillator. If the grid of the oscillator voltmeter minus the series resistance, as is touched a distinct click should be The actual tuning in is greatly sim- only comparative readings need be made. heard, and the meter should act in the plified by the use of a meter. By noting The first thing to test is whether the same way as with the r.f. tubes, when the action of the meters as the loop (or I battery circuit is right. Place one oscillating. If the condenser is varied, Continued on page 64 30 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com Second Harmonic Super-Heterodyne A Simple and Helpful Explanation of the Principles Underlying this Non -interfering Circuit By L. R. Felder sets amplifier) we have a signal having a fre- oscillate at about the same frequency as UPERHETERODYNE anyone in the working on the "second harmonic" quency of 50,000 cycles which is a simple the received signal. If have been the cause of wonder as matter to amplify efficiently. The fre- immediate vicinity of a superheterodyne in- to what is the underlying mystery. The quency transformation does not itself set is receiving signals of nearly the same second harmonic superheterodyne works volve any change in the characteristics frequency as the oscillator in the super- re- on the same broad principle as all other of the original signal. That is, the heterodyne sets generates, and the loop types of superheterodyne sets. This sultant 50,000 -cycle signal has all the radiates these oscillations, the possibility principle was explained in June RADIO characteristics of the original 950,000 - of audible beats with consequent inter- by the writer. Briefly, the incoming low cycle signal which it is desired to hear. ference being developed is considerably wave (high frequency) signal is trans- It is thus apparent that the radio - enhanced. There is no doubt that such formed into a high wave (lower fre- frequency oscillations generated by the interference does take place. However, quency) signal, which is then more local oscillator must have approximately the superheterodyne set is not sufficiently easily amplified by efficient high wave the same frequency as the received widely distributed for it to be noticed, amplifiers. signal. In the above case the received and many supers use a radio -frequency The method by which the frequency signal has a frequency of 950,000 cycles, blocking tube which helps cut down the is changed from low wave to high wave, while the locally- generated oscillations interference. or from high frequency to low fre- have frequency of 1,000,000 cycles, only To avoid possibility of such inter- quency, involves the use of a radio -fre- 50,000 cycles apart. Some receivers are ference, the second harmonic principle quency oscillator and the principle of built so that the difference in frequency was invoked. If a set could be made in which the radio -frequency oscillator generated frequencies far removed from the frequencies of incoming signals, then, even though the oscillations were radiated from the loop, no audible interference would be produced in other receivers because the frequencies were so far apart that the beat note was well outside the audio -frequency range. This Oltei//aéor could be done by making use of the second harmonic of the generated oscillations. 1W-46'6'11-4r6bTh A vacuum tube oscillator does not ordinarily generate a single frequency /CY+ for a given setting of the circuit con- Fig. 1. Superheterodyne Tuner and stants. Thus suppose that the constants Oscillator are so fixed that the oscillating circuit tunes to 600 meters, 500,000 cycles per cycles. It second. Then the vacuum tube oscil- beats. In Fig. 1 we have a typical loop is even less, say about 30,000 oscil- circuit tuned to an incoming signal of will be seen that this difference in fre- lator will generate radio -frequency high frequency, let us say 950,000 cycles, quency is perilously near the audio -fre- lations of this frequency, but at the same of which corresponds to a wavelength quency range and this introduces audible time it. will generate oscillations slightly higher than 300 meters. There radiation from the receiver. double this frequency, namely 1,000,000 this frequency, is also shown a radio -frequency oscillator Interference due to receiver radiation million cycles, three times so on. The lowest which is tuned to a frequency of is caused by so much regeneration that 1,500,000 cycles, and to 1,000,000 cycles let us say, and these the receiver acts as an oscillator and frequency which it generates is that in oscillations are coupled to the loop cir- radiates these generated oscillations. which the oscillating circuit is tuned, this fre- cuit by means of the coupling coil L. Nearby receivers working on approxi- this case 500,000 cycles, and or first The incoming signal oscillations and the mately the same wavelength pick up quency is called the fundamental of double the locally -generated oscillations are there- these oscillations and beats are set up harmonic. The oscillation it gener- fore present in the same circuit and ap- between the incoming signal and the fundamental frequency which Inasmuch plied grid of the tube D. oscillations due to the regenerating re- ates is the second harmonic. to the to the These two oscillations, according to ceiver. The squeals and other inter- as the oscillating circuit is tuned expected that the fundamental principle of beats, com- fering noises are the beats set up between fundamental it is to be of the oscillator is bine to form another oscillation having a these two oscillations. most of the energy The succeeding har- frequency which is equal to the differ- In the superheterodyne circuit we in this frequency. have less energy in ence. Thus we have a resultant oscil- have a somewhat more aggravated case monics generally vacuum lation having a frequency equal to of the same type. In place of the oscil- them.. Thus a radio -frequency 1,000,000 minus 950,000, or 50,000 lating regenerative receiver we have a tube oscillator generates oscillations of which bear a certain cycles. In place of a signal having a radio -frequency oscillator which is a various frequencies frequency of 950,000 cycles (which is miniature transmitter whose oscillations ratio to the fundamental frequency, and very difficult to amplify due to impossi- are radiated by the loop circuit. what is most important to this discus- gen- bility of building a good low wave The usual types of superheterodynes sion, the second harmonic oscillation RADIO FOR SEPTEMBER, 1924 31

www.americanradiohistory.com erated by such an oscillator has a fre- lator dial, sometimes three, four or even FILAMENT SUPPLY FROM quency of twice the fundamental. more. The reason is that transmitting 110 V. A.C. Consequently it is possible to make stations likewise may be radiating, not By RAYMOND A. SMITH the superheterodyne oscillator tune to a a pure wave, but one with harmonics. The ideal radio receiver must be in- frequency far removed from the range As a result, when the oscillator of the - its range expensive, simple to operate ' and eco- of frequencies being received, and superheterodyne is tuned over still secure our intermediate beat fre- a number of settings may be found nomical to keep up. The Harkness re- is picked up, for quency of 30,000 to 50,000 cycles, where the same station flex circuit is both simple to operate and each of the oscillator control and this without creating any inter- at setting inexpensive to either buy or build, and, between the new oscil- ference. Let us consider the nu- a beat is produced a harmonic fre- by using a.c. current supply on the fila- merical illustration above. Suppose lator frequency and station. The ment, becomes economical to keep up. that we are receiving a broadcast signal quency of the transmitting has heard a given station on as to step of frequency of 950,000 cycles,. which writer By using a filament transformer many as six different points of the oscil- corresponds to a wavelength somewhat down the 110 volts to 6 volts for C -201 is not usual, but occurs greater than 300 meters. And let us lator scale. This A tubes, the cost of either storage bat- with transmitters which radiate a very assume that we desire to transform this teries or dry cells can be eliminated. high frequency down to an intermediate impu# wave. Le work on the second harmonic There are several types of transform - frequency of 50,000 cycles. If we design principle the oscillator must be designed ,. ....erg on the market, costing about $5 re- the oscillator so that it tunes to a fre- to ;oscillate at twice the wavelength of quency of 500,000 cycles, corresponding tail, the preferable type being that which received signal over the entire wave- to a wavelength of 600 meters, the oscil- the has a middle tap. length range of the tuner. Thus suppose lations will be sufficiently far removed The primary is connected direct to the is intended to cover a from the broadcast range to avoid any that the receiver rheostats and range from 300 meters to 110 -volt a.c. line without interference due to direct radiation of wavelength oscillator should then 'Elie two main secondary taps connected these oscillations from the loop antenna 500 meters. The cover the range from through 30 -ohm rheostats to the fila- or other antenna. However, 500,000 be designed to meters to 1000 meters, the ments of the tubes. The middle tap is cycles cannot combine with the received about 600 secor. harmonics of which will then connected to the grid return through 950,000 -cycle signal to give us an inter- i cover same range of frequencies and the C battery. It is essential that there mediate beat frequency of 50,000 cycles the wavelengths as is covered by the tuner be a 30 -ohm rheostat in each leg of the which may be efficiently amplified. itself. The circuit arrangements and supply, as, by balancing these However, this is the fundamental fre- filament connections are exactly the same as for quency of the oscillations generated by rheostats, the a.c. hum is eliminated, the more standard type of superhetero- the oscillator. The second harmonic of which will be very noticeable unless dyne circuit. the oscillator has a frequency of two these two rheostats are carefully ad- music is off between times the fundamental, or 1,000,000 Remember that an amplifier without a justed. When the can be faintly heard. cycles. The 1,000,000 cycles second C battery is not an amplifier at all, but selections, the hum harmonic . can beat with- the received simply a distortion producer, if more This device cannot be used on a set with signal of 950,000 cycles and form the than 40 or 50 volts plate potential is a tube detector but only with a set using required 50,000 -cycle beat frequency. used. a crystal detector. And this is exactly what the second har- yo4A 40 IHSIDe The monic superheterodyne accomplishes. vztz-Z Grr-r Jet To se. whit 11P-f- Awh -Oo/ nothtn$ should be observed that the funda- WroT$ n Is wrong -Ant, -- It 134/Z2, 2-2,' mental of the oscillator also beats with the received 950,000 -cycle signal. How- ever, the beat frequency is so high that it is inaudible and so creates no interference. The whole idea is to make the oscillator so that, if it does radiate oscil- whenYou Have ° Been II earinc lations, their frequency is so far removed -Jrv,p Like This More Than 3 from received frequencies that no audible MonFor t/ Arw- interference is created. At the same time provision must be made for enabling the Na! eact Gettlnv,lt " romatcYeerl intermediate beat frequency to be se- etosel ewer !íe by cured, and this is made possible the t you Ger A man presence of harmonics in the generated Pre,, Tke Power co. To Put new oscillations. Darn These Ra ínsw.ators on lo glut's Any The HtchTension It is possible with a superheterodyne way y 4LI44 Line AcrossTAe to find two positions of the oscillator Hlaktnc Trou Street- ATID- (AL !e For, Me may be Ddrn setting at which any given station nett rod/ Takt A.artn'-S vnt!' received, because the oscillator may be $vJth a LOOP Arlo Tletnk you Have set 50,000 cycles above or below the re- Fount, The Troubt.e. -AnD- ceived signal frequency and still a 50,000 -cycle frequency will be obtained. Thus, suppose a 950,000 -cycle signal is 'IA being received. If the oscillator is tuned ,« NOU7e s to 1,000,000 cycles a beat frequency of Then Yov TrY sewn TuL aao set Af71h L eavec TAe > is // The Then tu- Get 50,000 cycles will be secured, since it e inn The DOC- Teo114 Base- d .1aLl JtIrOJ , Gone noise OV 1.0011i *VT OP TOW Wit,- %h. the difference of 1,000,000 and 950,000. 1 íJ hem. Ano if Ththe! tATe,tLljlt MYSTertovs Also the same result will be secured / -TriuOLt IN Ann RIGHT TeeAc1' the oscillator is tuned to 900,000 cycles. DOeJNT iT/41AKR oú 111 O,// REp!! It often happens that a station is heard , sHW.ALLtN. oscil- i' at more than two settings of the 1924 32 RADIO FOR SEPTEMBER,

www.americanradiohistory.com Improvements in the 45,000 Cycle Super - Heterodyne By G. M. Best LARGE number of suggestions meter, is to measure the current flowing through the resistances, with a milliam- for the improvement of the AUGUST PRIZE WINNERS 45,000 -cycle Super- Heterodyne, meter, and compute the voltage by the originally described in May RADIO, In Contest for Improving Best's well known formula E = IR, where have been received during the past Super- Heterodyne E is the unknown voltage, I is the meas- month. It is unfortunate that most of 1st prize -$25.00 -J. R. Balsley, 299 ured current, and R is the known re- South Park Ave., Fond du Lac, sistance. these suggestions call for the use of the Wis. UV -201A or C -301A tubes, which re- 2nd prize -$15.00 -D. B. Mc Gown, ANOTHER suggestion of merit, pri- a storage battery. The set was quire 1247 47th Ave., San Francisco, Calif. marily intended for those who originally designed as a dry battery re- Clair Foster, 3rd prize - $10.00 - desire a large volume out of their audio- ceiver, and the addition of a storage bat- Carmel, Calif. frequency amplifier, is the addition of a tery, with its associated rectifier or other Similar prizes are to be awarded power amplifier, partly operated from charger, does not constitute an improve- each month and additional final a.c., in place of the last dry cell tube in ment, in the opinion of the judges of best ideas submitted prizes for the the audio- frequency stages. The circuit the contest. during a six -months' period. for this amplifier is shown in Fig. 2. While there is no doubt that the use The amplifier consists of a UV -201A or larger tubes, with their higher of the C-301A vacuum tube and associated amplification constant and mutual con- the jack, the voltmeter is disconnected socket, a choke coil of 25 henrys or more ductance, will increase the amplification from the filaments, and can be used for (a G. E. Wayne Bell Ringing trans- per stage in the intermediate frequency any other purpose, up to its maximum. winding will do), . a 2- not enough gain will be ob- scale. former primary amplifier, a small bell ring- warrant the extra expense of This voltmeter cannot be used for microfarad condenser, tained to transformer, two Cutler- Hammer the battery and charger. Of course, many measuring the voltage drop across the ing already have a storage battery, and 2a,{ probably would prefer to use it instead in of dry cells. In that case, great care 2s constructing the set will be necessary, /sí. Henrys and a considerable amount of shielding Stage will be required, due to the larger amplification obtained. It would be advisable to shield the back of the panel, the baseboard section containing the oscillator coupler, oscillator tube and oscillator air condenser, and the inside of the zi1111111 1111111 11111,1,1t111, cabinet. B" + +90 4-/2O The best suggestion of the month, for improvement of the dry cell set, is the addition of a four -spring telephone jack, To oflser on the panel, for the purpose of bring- ta,Ge's i» set - ing out the voltmeter terminals in a Fig. 2. Power Amplifier Hook -up manner so that a plug, with flexible cord resistances, and a 200 - and clips attached, may be inserted in biasing resistances suggested in the 25 -ohm variable the jack, and the voltmeter, which is dis- August issue of RADIO, as the volt- ohm potentiometer. connected from the filament circuit, may meter is a low resistance affair, and will The plate voltage applied to this stage be used for measuring C batteries, or give an erroneous reading if so used. should be at least 120, for 9 volts nega- any other battery desired. This jack, The only way to measure the voltage tive grid potential. As there are several and its connections, is shown in Fig. 1. drop across such resistances, without the makes of bell ringing transformers on The jack may be a Federal 1423 -W, use of an expensive high resistance volt - the market, with secondary voltages or any other jack of similar number of + ranging from 6 to 10 volts, it is neces- springs, and contact arrangement. The I To //o'er ent sary to provide sufficient resistance, in jack go to the clec' ulf two main springs of the series with the filament circuit to reduce voltmeter terminals, and the two con- the voltage at the filament to 5 volts. tacts are connected to the main filament If a 10 -volt bell ringing transformer is leads in the set, so that normally the used, with i1 tubes, these resistances voltmeter is connected to the filament should be 8 ohms each, and, as the circuit. When the plug is inserted in Cutler- Hammer resistances are easily adjustable, this can be done very quickly. The 200 -ohm potentiometer should be varied until no noise is heard in the output of the tube. The above arrangement will enable the user to handle levels considerably in excess of Fig. 1. Voltmeter Jack Connections power RADIO FOR SEPTEMBER, 1924 33

www.americanradiohistory.com that ,permissible with the dry cell tubes, THE GRID LEAK which have only 90 volts on the plate, and 472 volts negative grid, without the By H. Bunch addition of a storage battery. It would be interesting to know just than the grid, which has only the slight- FIG. 3 shows the rearrangement of how many radio fans really understand est fraction of a volt positive impressed apparatus on the panel, as sug- the precise function of a grid leak, the upon it. We must remember, however, gested by Mr. Clair Foster, and will no correct values to use, and the correct that the grid is at a positive potential, doubt be of interest to everyone. Mr. way of connecting it into circuit. however small, and it is due to this fact Foster suggests that,, inasmuch as many At first sight, the grid leak seems to that some electrons must be attracted to do not like the binding post terminals have no use, although we know that it and held on the grid. brought ,out on the rear of the baseboard, would not be found in every detector cir- The electrons drawn to the plate have it would be well to mount them on the cuit unless it had some important func- a very easy path to traverse. They pass panel, and he has accordingly lengthened tion to perform. Suppose we take it through the B battery and the phones the panel by 1 in., and the baseboard by out ; what will happen ? At first nothing back to the filament ; but what of those the same amount. He has placed the seems to happen. The electron tube electrons that were attracted to the grid ? Cutler -Hammer battery switch at the continues to rectify as well as before, There is no path for them, for, as men- right hand end of the panel, where it but in a short time signals begin to lose tioned previously, the grid condenser is close to the battery binding post their original strength and gradually die presents an impassable barrier to steady currents. Without a grid leak, these electrons have to stay where they are, and, after the detector has been working for a short time, there is an excess of electrons accumulated on it, and, as these can find no way of escape, the tube is paralyzed ; which accounts for our signals fading away. Now, if we touch the grid terminal with the finger, the signals revive. What is happening now ? The answer is sim- Fig. 3. Suggested Re- Arrangement of Parts ple. The stored -up electrons have now found a passage back to ground through terminals. Three jacks have been pro- away. Suppose we put the grid leak back ; the body, which is now acting as a high vided in a convenient manner, so that or, if you like, simply touch the grid resistance leak. It would be very incon- the audio- frequency amplifier, in whole terminal with your finger; and it will be venient, however, to have to keep our or in part, .may be cut out of the circuit. found that the signals will return im- finger on the grid terminal all the time In the original set, the phone jacks were mediately at their original strength. we are receiving, so the grid leak is inter- placed one above the other, at the ex- This should be proof enough of the posed with excellent results. hand end of the panel, but high value of the grid leak in your re- treme right Gr.d Leak in this case they have been arranged be- ceiver, so let us now consider what is its tween the detector and the audio -fre- part in the operation of a radio set. quency amplifier tubes, where the wiring Incoming radio waves are impressed will be very short and convenient of at very high frequency on our receiving access. antenna, which is connected in series Several readers have complained that, with the aerial tuning inductance. This after constructing the antenna adapter radio- frequency current is induced in the described in July RADIO, they could secondary circuit, one side of which is not use it due to lack of selectivity and connected to the grid condenser. This This trouble Fie,. 1. Grid Leak Connection in noise on distant stations. condenser offers very little resistance to Single -Tube Circuit is probably due to the use of too much radio-frequency currents, but will block amplification in the intermediate stages, all steady direct currents. This con- In a single -tube circuit, the grid leak lack of loose coupling of the rotor with denser will allow the radio -frequency should be connected across the grid con- the stator of the variocoupler, and lack currents to :pass ; so these are next im- denser, as shown in Fig 1, and this of shielding of the cabinet in which the pressed on the grid. should also be done when radio -fre- tuner is mounted. If the antenna tuner The grid really controls the whole quency amplifiers are magnetically con- is to be used exclusively, sufficient ampli- action of the tube. When the grid is fication may be obtained by using only at a negative potential, it does not allow two intermediate stages of amplification, the passage of any electrons between the and, if extremely loose coupling is em- filament and the plate. Rather, it has ployed, no trouble from noise or inter- a tendency to push any free electrons ference from nearby stations should back to the filament, but, when the result. It would be best to shield the grid is at a positive potential, it gives inside of the tuner cabinet with sheet assistance to the plate in attracting elec- brass or tinplate, grounding the shield trons from the filament. at the ground binding post. When both the plate and filament are receivers is at a positive potential, by far the greatest A good pair of telephone Fig. 2. Grid Leak Connection in Tuned one of the most sensitive electrical re- number of electrons are attracted to the Plate Circuit cording devices known to science. Con- plate. This is due to the high tension, sider, then, how much more sensitive a or B battery, which may be anywhere nected to the detector tube, as is the case good vacuum tube is when it operates from 20 to 60 volts in its circuit. This when transformers are used. When a these receivers satisfactorily. gives the plate a much higher potential Continued on page ya

34 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com A Transmitter that Solves the Local QRM Problem How to Build a Small One Tube Transmitter Suitable fcí Local Work .va By Franklyn S. Huddy, 1 II-1 ZS

OST of us have at some time diameter. In its periphery, drill 17 -and it will be if you have connected it wished for a small, low -pow- holes 3/16 in. in diameter, in. deep rightly-you will hear the wave of the M ered transmitter with which and /8 in. apart. The holes should be transmitter as it crosses that of the .re- it would be possible to work local sta- equally spaced. Obtain some 3/16 -in. ceiver. If Your receiver is calibrated, tions on C. W. or phone without causing dowel and cut 17 pieces 2 in. long. you can set the, transmitter at any desired interference either to other amateur sta- These pegs are inserted in the wooden wave by listening on the wave you wish tions or to members of the broadcast fac- disk, and should fit just tight enough so and tuning in the transmitter. O tion. The use of such a transmitter that they may be pulled out easily when For phone work, either a loop or a. would be a distinct economy, as it would the coil is done. Some of the 5- and -10- microphone in series with the antenna save our large tubes for long distance cent stores sell these forms already made may be used. work. Aside from this, and the fact up and, if it is possible to purchase them The interferente caused by these sets that it would reduce interference, such already made, it will save time. is practically nil. The author transmits a transmitter would enable many sta- When the form is made, select any on an antenna which is directly over the tions to comply with the Federal law peg as a starting point and fasten one receiving antenna of a B. C. L. The requiring all stations to use the least end of the wire to it. Then wind on signals from the small set are inaudible possible amount of power necessary to 18 turns of No. 16 or 18 d.c.c. magnet in the B. C. L. receiver and do not inter- carry on communication over a given wire, crossing over and under two pegs fere in any way. distance. each time. This is the tickler winding. As for distance which may be covered, To be practical, such a transmitter Start again and wind on 20 turns of that will vary with the power, the an- should enable the operator to change the the same wire and in the same direction. tenna, and the location. Using a single - wavelength quickly and with as few ad- This finishes the winding. wire receiving. antenna 60 ft. high and justments as possible. The transmitter 100 ft. long, and with 22/ volts on the to be described will tune from 220 to tube, the author, worked a station in the /IM7P.vNA second 180 120 meters by the turning of one dial, s+ie, Cewo,..vs, district about miles away. and will give quite an even output over That does not mean that 180 miles can Ovrt,O( f.vo , COIL the whole band. be expected as the range of the set: for Furthermore, this transmitter will the transmission was a freak. However, work with a ground, thereby enabling Our,/o, CO, the little set will easily do local work, 20 TURNS those who cannot erect counterpoises to which, after all, is the purpose for which use C. W. where it might not otherwise it is designed. be possible. .002 Sr00,,Nc CONOCNSCR 6 A' $Ar HANDY HINTS IN RADIO The materials needed to construct this .loo v. They /Cc', set are few and easily obtained. /Nilor Cois In using oxide filament tubes, their are as follows: /8 r&' ws AlCNdrf filaments should be burned at as low 'a The plate supply consists of a 45- / temperature is possible, even though it volt B battery. For greater distance, /NS /OE ENO OO COIL may be lower than the normal current voltages up to 300 may be used, but for rating as stated by the manufacturer. all ordinary purposes 45 volts is perfectly Obtain some collodion at a drug store Tubes abused by being given too much satisfactory. and put it where the wires cross in the filament current will last only a short The best tube to use is the UV -201A coil. This will make the coil self sup- while, and after a short period of abuse or C-301A. This will give more output porting. The pegs should then be must be operated at the higher value to than the usual hard tube, although the slipped out and the disk removed. The get them to operate at all. latter functions very well. inductance is done and should be al- A first class insulating paint for coil The condenser should be of the 11 lowed to dry in a warm place. winding, panel finishing, etc., can be or 23 -plate type. Almost any condenser The radio -frequency choke is made found in the pyroxlin lacquers which are will do, but the better condenser you by winding 250 turns of No. 28 d.c.c. attaining such popularity in auto finish- use the more output you will get, and, wire on a 3 -inch cardboard tube. When ing. If such substances are used, how- since the total amount of energy avail- this is done the set is ready to assemble ever, care should be taken to use them able is small, it is advisable not to waste and connect. under conditions where they will be' kept any of it. A fixed condenser of .002 Connections are shown in Fig. 1. away from all fire as they are extremely mfd. is also necessary. This may be a The main thing to remember is that the inflammable. micadon or any condenser that will plate connection goes to the innermost Those of you who wish for "one knob remember stand the plate voltage. - end of the tickler, and the grid to the tuners" should that while they The inductance is the only part of outside end of the outer coil. may be perfectly possible, that it is im- the set which it is necessary to make Operation is started by lighting the possible to get something for nthing, yourself. The form upon which it is tube and closing the key. Listen in your and if you reduce the controls of :a set wound is made as follows : Cut a receiving set while you turn the antenna you are bound to lose out in something wooden disk % in. thick and 2/ in. in series condenser. If the set is oscillating else. RADIO FOR SEPTEMBER, 1924 33

www.americanradiohistory.com DIGES T OF RECENT RADI _.. PATENTS -. : .. MIuni : , . C t ii-c,

Prepared by White, Prost & Evans, patent attorneys, San Francisco, who have been particularly active in the radio field for many years, from whom may be obtained and further information regarding any of the patents listed below. These patents are selected especially with reference to their possible application and use by the radio amateur.

H. G. Saal, Pat. No. 1,497,384. Radi- sharp by this method, but the e.m.f ant Energy Receiver. across the grid circuit includes a coil 8 inductively condenser 29 is amplified by a very large coupled to the antenna. The grid circuit The crystal detector described in this factor -of the order of one hundred, as may also includes the grid condenser 9 and high be patent is designed to provide ready and sim- verified from theoretical considerations. resistance leak 10. Use is made of the well - ple adjustment of the catwhisker 14, which is The induction motor of course acts as a gen- known fact that, if the oscillator 1 is to be fixed to a rod 13. This rod in turn is in erator of the desired frequency, and its selec- maintained in operation, an opportunity must frictional engagement with a bore in the ball tivity of course is due to the fact that such be given for the negative charge that collects a generator, when rotated at the right speed, on the grid 4 to leak off. If, for example, is ineffective to reduce the antenna resistance the circuit of resistor 10 be interrupted, the for frequencies differing even slightly from tube will stop functioning, because the nega- that which carries the desired signals. tive charge would accumulate. In this manner signals could be started and stopped, by H. H. Pickron, Pat No. 1,485,524. simply controlling the circuit for the resistor Crystal Detector for Radio Instruments. 10. Another way would be to provide an This patent describes a crystal detector additional condenser 11 in the grid circuit, that has a special form of explorer electrode which may be shorted by a sending key 12. This condenser, when not shorted, blocks the leakage of the charge from the grid 4, through the grid circuit, and thereby para- 9, so that axial adjustment may be thereby lyzes the tube until key 12 is operated. The secured. The ball 9 is seated on top of the source of oscillations is thus active only while hollow post 6, and is urged firmly into con- signaling is in progress. tact with its seat by the aid of spring 10. In // /z this manner the ball 9 may be angularly ad- LETTERS TO THE EDITOR justed, and the rod 13 may be axially adjusted during the process of exploration. Canada Has Quiet Hours Sir: An erroneous statement was made in the August M. I. Pupin, Pat. No. 1,494,803. Elec- /9 issue of RADIO by Mr. Laizure trical Tuning. /7 of Kansas City concerning quiet hours in Canada. He stated that no quiet hours This patent discloses highly interesting /S were a observed. I wish to say that quiet hours are scheme for making an absorbing circuit much 3 compulsory and have been more by observed in selective than ordinary tuning Canada for the last year. Please correct methods. is based recog- this This upon the well- statement in your next issue. nized fact that, the less the effective resistance Edmonton, Can. J. E. SACKER. is of the circuit, the sharper is the tuning; render or " catwhisker" 14. This is in the form of a and Pupin proposes to the effective telescoping Screw Thread Detector resistance of a very low value for only a spring made from a flat strip of frequency. Thus, in the antenna metal, the active end being almost a complete Sir: Permit me to quote an experience selected cir- circle. mounting cuit 25- 31- 32 -26, he purposely inserts a high The is such that the elec- which may be of interest to radio fans and trode may be pressed against the crystal 9 by may stimulate investigation. rotating the supporting stud Il, which is in Recently, while listening on a crystal set, threaded engagement with the casing 2. Ro- the crystal dropped out of the crystal holder tation also serves to scrape the crystal sur- and fell to the floor; the reception of music face and thereby to renew the sensitivity. continued, although slightly fainter. On in- vestigating the cause, I found the cat W. C. White, Pat. No. 1,491,450. High whiskers (of which there were five) were Frequency Signaling System. resting on the points of the threads of the This patent describes a constant wave screw in the cup of the crystal holder. transmission system using an audion 1 having I placed the cat whiskers on various parts of the crystal holder, but detection resulted only when the whiskers were in contact with screw threads. This was done repeatedly, and the fact developed that a screw thread is ohmic resistance 30, whereby, if nothing fur- a detector of radio. ther is done, the circuit is substantially inef- This you may publish or use to stimulate fective- for all frequencies. Shunting this re- investigation. sistance, however, is a circuit 27 -29 in- Ferry Bldg., cluding inductance 27 which may be the San Francisco. OLIVER W. JONES. primary or stator of an induction motor type of dynamo-electric machine. By ro- Due to the difficulty in soldering a wire to tating the rotor 28 of this machine at the a water pipe for ground, a better joint can proper rate, the effective resistance of the be made by wrapping a strip of tin foil entire circuit may be reduced, and this re- around a brightened circumference of the pipe duction exists only for a definite frequency. and then wrapping several turns of your The translating device 33 may be in the form ground wire tightly around the tin foil. The of phones or the like, and may be bridged tin foil will not oxidize and prevents both the across a condenser 29 that neutralizes the in- coupled grid and plate circuits, for generating pipe and the under side of the wire from ductance 27. the oscillations. The plate circuit includes doing so. C. L. TICE. Not only is the tuning rendered extremely the coil 6 that is in the antenna circuit, and Yakima, Wash.

36 RADIO FOR SEPTEMBER. 1924

www.americanradiohistory.com QUERIES REAP cw. cTPrE BY Gerald M.Best TECHNICAL ADVI SOR

Questions submitted for answer in this department should be typewritten or in ink, written on one side of of interest will be published. Readers are invited to use this service with- the paper. All answers general is wanted. out charge, except that 25c per question should be forwarded when personal answer by mail a simple "A" battery degree coupler should be employed, with not I would like to use a number of WD -11 Please print hand in a Radiola Super - charger for use with alternating current. over 10 turns in the rotor, which is placed tubes I have on W., Utica, N. Y. in the antenna circuit. A 75 -turn honey- Heterodyne. Will any special changes -J. be in the set, besides adapters, A circuit diagram for a single -jar electro- necessary in for it to work properly ? A. lytic rectifier was shown in Fig. 1, Page 36, order -F. issue of RADIO. A., Joliet, Ill. of the August The Radiola Super- Heterodyne is equipped I have drawn a sketch of an Inverse with volume and filament rheostats designed Reflex Circuit, adapted from the circuit for UV -199 tubes. The WD -11 tube draws published in an article by Paul Oard, in .25 ampere per tube, and 6 tubes would con- July RADIO. Are the connections cor- sume 1/ amperes, a total entirely too great rect? Would this circuit be an improve- for the rheostats provided in the set. I doubt ment for all- around reception? If three very much whether the set would function stages of audio- frequency amplification at its best with tubes other than those for are too much, would it not be preferable which it was intended. to eliminate the last stage? Is there a so- called Grimes Inverse Duplex Circuit? What is the purpose of the transformer -F. G. F., Los Angeles, Calif. in the base of the Western Electric 10 -D Your circuit diagram is O.K. except that loud speaker? None of their other loud three stages of audio -frequency amplification speakers have such a transformer. -J. H. is too much with only 90 -volt plate and 4/ J., Los Angeles, Calif. negative grid potential. It would be better The transformer prevents a large loss of to eliminate one stage. Your circuit would energy due to the difference in impedance be- amplification, but tween the output of the vacuum tube am- have more audio -frequency Fig. 2. Super- Heterodyne .1ntenna ildapter I doubt if it would receive more distant sta- plifier and the loud speaking receiver. The vacuum tube in tions. The circuit is practically the dupli- comb coil makes a good load coil. Be sure impedance of the average cate of the Grimes Inverse Duplex receiver, disconnect the loop antenna inside of the the last stage of an audio- frequency ampli- to of the which was described by M. B. Sleeper re- set before using the antenna adapter. fier is around 15,000 ohms, and that cently in a series of articles in RADIO. loud speaker is only 2000. Hence, it is neces- Which is the best receiver for general sary to provide a transformer with a pri- Kindly publish the circuit diagram of reception, the Reflex Neutrodyne or the mary impedance of 15,000 ohms and a second- the new Radiola VII -B, made by the Grimes Inverse Duplex? What is the ary impedance of 2000 ohms, so that the maxi- Wireless Specialty Co. -J. C. L., Bridge- right size of loop antenna for the above mum transfer of power can be obtained. port, Conn. receivers ? -C. M. S., Jr., Steubenville, Other Western Electric loud speakers are This circuit is shown in schematic form Ohio. wound to a high impedance, the average in Fig. 1. Both receivers are good for long distance being 14,000 ohms, and hence no transformer The Inverse Duplex set has fewer Please show how I may use a small reception. is required with them. . controls than the Neutrodyne, but uses about outdoor antenna in connection with my In tuning my honeycomb coil receiver An indoor the same number of tubes. A loop antenna Radiola Super -Heterodyne. a to the long waves, what would be the antenna connected as shown by the manu- made up of 12 turns of wire wound on frame at least 24 inches square, with wires best set of coils to buy, for wavelengths facturer does not give me sufficient ? R., spaced in. apart, will give you good re- from 5000 to 12,500 meters -H. C. volume on account of the steel frame of / Poughkeepsie, N. Y. H. A., Seattle, sults up to perhaps 250 miles. I would not the building I live in. -W. with the For an ordinary short wave antenna, the Wash. expect you to get as good reception loop as you will with a good antenna. primary coil should be 500 turns, with the A circuit diagram for an antenna adapter antenna condenser in parallel with the pri- is shown in Fig. 2. A good make of 180- mary. The secondary coil should be 750 turns, and the size of the tickler will depend upon the tube, some requiring as much as 750 turns and others only 500 turns.

o Loud Speake o tgS V

Fig. 1. Schematic Diagram of Radiola PH B RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com .St`at'or , Rot`or

J'tat

o +zo v Lovc/ S./beaker Please furnish me with a circuit diagram of the Westinghouse Regenoflex Receiver. -F. L. P., Gardinier, Me. "I'he circuit of the Radiola +80V X, known as 1 the Radiola Regenoflex, is shown in Fig. 3. T Kindly show me how to install "C" bat- Fig. 3. Lircu't Diagram of Regcnoflex teries in my Haynes 7 -tube Super- Heter- odyne so as to so it can be operated without form a square window i/ in. high, 4/ -volt C battery should be inserted positive will be the in the grid potential. -E. C. S., Ar- right size. On this core wind 360 grid circuit of the last tube. If the A buckle, turns of No. battery Calif. 18 DCC wire for the primary. is kept up to 6 volts, the drop across Over this the fila- 76 Ge7d To winding, place 27 turns of No. 14 ment rheostat will provide sufficient fi%aineaf DCC wire for C volt- Cie-c vi es Circuit`s the filament secondary. A age for the other two tubes. center tap should be provided at the 13V2 '4 A A turn. For the high voltage secondary, wind Kindly publish a good circuit for a 3270 turns of No. 30 DCC or enameled wire, portable set. I would like to have this with a center tap at the 1635th turn. If you set work either from a loop antenna or wish taps at 350 and 750 volts, take out leads an outdoor antenna. -R. C., Aurora, Ill. at 1145th and 2453rd turns. The 3 -tube Reflex circuit shown in Fig. 6 will make a good portable set, as it is the Please show a circuit diagram of the equivalent of four tubes and a crystal, in re- Erla 3 -tube Reflex set, giving the proper sults, and does not require a great amount value of "C" battery required. -A. S. V., of apparatus. For PoteNfioA7ette/! Dayton, use with a loop antenna, Ohio. it will be necessary to disconnect the antenna The Erla 3 -tube Reflex circuit is shown in coupler and insert the loop connections across Fig. 6. If the plate potential is 90 volts, a the secondary air 4ÍV condenser.

11111

Fig. 4. "C" Battery Substitution for Poten- tiometer in Super- Heterodyne

Fig. 4 shows the potentiometer in dotted lines, and the method of connecting the C battery. The potential given depends upon your using 90 volts on the plates. If only 45 volts is used then the C battery should be only 1/ volts. Please publish the circuit of a 5 -watt transmitter using the Meissner circuit, and with which I can use either phone or straight C. W. Please show how the rectifier is connected. Kindly give me the data on building a 1000 -watt transformer, tapped at 350, 500 and 750 volts.. Also give data for a separate step -down transformer for the filament of the 5 -watt tube. -F. M. H., Brea, Calif. A circuit diagram for a 5 -watt transmitter, using the Meissner circuit, is shown in Fig. 5. You did not state what kind of a rectifier you wished to use, so I have shown an "S" tube rectifier. The proper power transformer for a 5 -watt set with "S" tube rectification would be one wound to 1000 volts, with center tap at 500 volts. A core made up of silicon steel pieces in. wide 5 in. 5. 1/ and long, piled Fig. Meissner Circuit Diagram for 5 -Watt .Transmitter with 5 -Tube Rectifier

38 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com WITH THE AMATEUR OPERATORS 1BOM, D. L. DARLING, two -step A. F. amplifier. Separate receiving NEW WAVELENGTHS FOR aerial, with break -in system. Only one 50- AMATEUR TRANS- Greenfield, Mass. watt tube was ever used at once, as power MISSION Aerial -wire cone, 35 ft. long, of 71/2 to was low. -6 of 1923 -24, 3 ft. diameter; supported by 75 -ft. tree and Transmitting-During winter The following letter addressed to all Su- 44 states 60 -ft. pole; 60 -ft. lead -in of 9 -in. diameter. 1BOM has been reported from pervisors of Radio will bring joy to the Counterpoise -Composed of 8 wires, each (every American district), 4 Canadian dis- of 2600 amateur ranks: 65 ft. long, suspended directly under the tricts, and Porto Rico. A distance reports were re- aerial and 8 ft. above the ground. miles worked. 11 west coast Sirs: Effective this date, you are author- Insulation -14 Electrose insulators 10/ in. ceived during March. Am usually on be- ized to issue general and restricted amateur (because unable to get Ohio brass). Both tween 3 and 7 A.M., which may explain ab- reports. Visitors and sug- radio station licenses to permit the use of any lead -ins enter shack as half -inch copper sence of European quarter -inch plate glass and gestions are most welcome. Cards are highly all of the following bands of short tubes through one or run directly (without touching anything) to appreciated and I have tried to Q.S.L. same. wavelengths: 75 to 80 meters, 40 to 43 the set. Reports of 1BOM have also been received meters, 20 to 22 meters, 4 to 5 meters, in addi- Transmitter-Usually two 5 -watt tubes are from England and New Zealand. tion to the band 150 to 200 meters, provided JALO application is made by the owner of the station, which station must be prepared to use the wavelength, or wavelengths, requested. The use of continuous wave telegraphy only will be permitted on wavelengths other than 150 to 200 meters, and the antenna circuit must not be directly coupled to the transmitting circuit. Silent hours will not be required of amateurs while using the wavelengths within the above bands below 80 meters, except where the transmitting station is so situated as to produce objectionable interference with other services. Hereafter special amateur stations will not use wavelengths above 200 meters. They may be authorized to use the band of wavelengths from 105 to 110 meters in addition to the wavelengths within the bands authorized for general and restricted amateur use, where the special amateurs are engaged in conducting tests with government or commercial stations. General, restricted and special amateur will be permitted to use the entire stations Radio Station 1BOM band of wavelengths from 150 to 200 meters '. pure C. W., spark and modulated employing have. been tried, AMATEURS forms of transmission. used. (Two 50 -watt tubes NEWS OF THE ' -to operate It should be made clear to the amateurs but the voltage was insufficient Probably more amateur stations have been that the authority granted above is necessarily satisfactorily.) Hartley circuit is used, operating this summer than during any previ- 2.4 tentative because of the rapid development which, with the two 5 -watt tubes, puts ous summer in history. The use of shorter taking place in radio communication and the amps. in the antenna at 175 meters. 700 -v. waves and more efficient receivers has en- bands of wavelengths authorized may be C.R. a.c. filtered through 4- mfd. and double many of the amateurs to do consistent about abled changed whenever in the opinion of the 11/2 Hy. choke supply the plates, giving work in spite of the severe static. Even trans- Secretary of Commerce such change is neces- 85% d.c. reports. continental and trans -oceanic work has been sary. Respectfully, Receiver -Zenith receiver used last winter on. CBS, an amateur station in Ar- of carried D. B. CARSON, until "Q.S.T." published a description gentine, succeeded in communicating with proved more effi- Approved: Commissioner. "low -loss tuners." This New Zealand, thus establishing a new world's waveleng , ringtog WALTER DRAKE, cient, going lower in record for amateur work. J. phones, with Assistant Secretary of Commerce. 90 to 230 m. W. E. and Baldy's Amateur interest in the foreign countries is growing with leaps and bounds. New stations are springing up in both European and the South American countries. It will not be long before the amateurs of this country will be able to communicate regularly with fellow amateurs of the most distant lands. 7AEB of ALASKA works on schedule with 7NO of Aberdeen, Wash. A goodly number of messages have been exchanged between Alaska and the States. 7PZ and 7RY are two of the most consistent stations in the state of Washington. 7AGF, F. W. Prince of Troy, Mont., has established a record for consistency. He hasn't missed a night on the air for two years. 7KV of Ilwaco, Wash., is erecting a new 75 -ft. mast and hopes to establish some new records this winter. 7DM now has a 150 -watt transmitter in operation. He uses storage B batteries for plate supply. This gives a pure d.c. note that carries extremely well. A" 1-9ov Call 6KB has been assigned to L. E. Mar- Fresno, Calif. Fig. 6. Erla Three -Tube Reflex tin, 100 Olive Ave., RADIO FOR SEPTEMBER, 1924 39

www.americanradiohistory.com Oregon has a few reliable amateur stations. Among those heard most often are 7ABY, 7MF, 7AJQ, 7ALD and 7JU. The call letters 7SI have been issued to Miss Harriet Elsworth of Boise, Idaho. She is one of the few young ladies west of the Rocky Mountains to secure an amateur license. 7LN, L. Martin of Nampa, Idaho, has lowered his wave to 170 meters and finds that he can work much farther than he could on a wave of 200 meters. Call 6BBV has been assigned to Jack Barsby, 518 W. 50th St., Los Angeles, Calif.. Call 3UQ has been assigned to Albert Kump, 31 W. Commerce St., Bridgeton, N. J. All cards appreciated and QSLed. Station 6ATN has received verification of the reception of F. D. Bell, New Zealand,

4AA, on March 18, . 1924, on a Grebe CR-3 and one step of audio -frequency. 6ATN has been reported by J. H. Worthington, Auck- land, New Zealand, Roy Buclz, Kodiak, Alaska, and seven districts. Power: Two S- watters and 400 -v. d.c. from a battery dyna- motor. Would appreciate report of anyone having verification of hearing a New Zealand New Differential Recorder for Automatic Reception station prior to March 18, 1924. of Morse or Printing Telegraph Messages, As Devised by A. Hoyt Taylor, U. S. Navy Physicist 6ZD, Allen H. Babcock, has returned to -Henry Miller News Picture Service, Inc. San Francisco from the first Inter -American Conference at Mexico City, where he was the RADIO STATION 9VK lead -in. The counterpoise is 60 ft. long by only American delegate to 30 ft. wide by 10 ft. remain during the Radio Station 9VK is owned and operated high, fanned. There is ,entire conference, as Ambassador some 1500 ft. of No. 14 Warren and by F. H. Lester, 1155 Wisconsin Ave., Oak solid copper wire in Whitehite were compelled re- the counterpoise, is to Park, Ill., and is devoted exclusively to ex- which constructed in turn to the United States before the deliber- perimental work. screen fashion and connected directly to the ations were concluded. Because transmitter, no grounds the agree- The transmitter consists of four being used except for ments signed by the representatives of 50 -watt the receiving sets. Porcelain the tubes in "Sure Fire Ckt." somewhat modified, bar insulators other countries provided for the formation of are used exclusively. radiating 10 amperes on C. W., I. C. a union to promote government ownership of W., and The entire station has been designed and fone 3 communication amperes. The entire set is panel - built by the operator. facilities and to unduly regu- mounted with the The short time the late private systems, Mr. exception of the plate set has been in operation the Babcock has recom- transformer and the rectifier signals have mended to Secretary Hughes jars. The been reported in every district in the United that the United meters on the panel are filament voltmeter States should not sign the agreements as States, Hawaii, Canada, WNP, and at sea. 0 -15 -v. a.c., plate voltmeter 0- 2000 -v. d.c., they are in conflict with our national policies The operator is a member of the A. R. R. milliammeter 0 -1000 milliamperes, and ther- L for the encouragement of private initiative. and also the A. R. R. L. Oak Park cor- mocouple ammeter 0 -15 a. The switches on Mr. Babcock believes that one result of this respondent. the panel are to change from low to high It would be appreciated conference will be to bring the government power. very much to hear departments into closer relations with the from all stations hearing 9VK's C. W., The plate voltage is rectified a.c. The amateur, whose activities are to be greatly I.C.W. and fone signal. All correspondence encouraged. rectifier consists of 48 jars, especially con- will be answered. structed for this purpose, filtered through a 9BAB, Carl Teten, 3931 4th Street, Des filter designed and built by the owner. Moines, Iowa, will answer all QSL's. RADIO -8XBH The receiving sets consist of a short 8UF wave By 7NX has been re- assigned to Arthur set 95 -200 meters, a three -circuit tuner, and a F. BUCK Chapelle, Woodburn, Oregon. Any one hear- "honeycomb coil" set, and a two-stage ampli- 8UF -8XBH is located at Clarkson College ing his 10 -watt battery plate -supply trans - fier which can be used on any of the sets. of Technology, Potsdam, New York. The mitteer please QSL All cards answered. Western Electric and Brandes fones and antenna consists of a vertical cone 6 -wire SANE has been issued to W. W. Merkle, Magnavox complete the receiving equipment. cage S , ft. in diameter at the top and tapering 804 Parkman Ave., Selma, Ala. QSL wanted The antenna is a four -wire, flat top, 70 ft. on his 10 -watt C. W. long by 50 ft. high, "T" type with fanned

250 -Watt Transmitter at 8UF -8XBH

to 6 in. at the bottom, with a 4 -in. cage lead - in. The stick that does her stuff is 50 ft. high and stands on top of a 25 -ft. support, so that this here scandal slinger resides 75 ft. up into God's clean air. The counterpoise is composed of 11 wires 50 ft. long and directly under the bird cage. The lit ole 250 -wafter you see in the picture shoves 4.5 amps. up the stack on 110 Radio Station 917K meters (8XBH) and 14 amps. on 180 meters

40 RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com 3zm, (8zs), 8abj, 3abw, 8acq, 8acr, (8adp), (8UF). The circuit is Hartley all the way 3afs, Saha, 3ahp, (3aoj), Sapi (8apv), 3auv , from the antenna to the counterpoise. The Bbdo, 3bdr, (3bmn), (3bno), 3bnu, 3boa, (8bof , plate supply is obtained from a line trans- (8bqp), 8bsb, 8btu, (8buy), 8bva, (8bvu), CALLS 8bwt, (8cbx), (8cdk), (3cdn), Begs, (ache), former which delivers 3000 a.c.; the plate (8cjn), (Belch), 8cvc, 3xan, (4af), 4ai, 4bx, current at this voltage is .25 amps. The 4dx, 4dy, 4ea, 4e1, (4fs), (4ft), 41t, 4jk, 4jr, plate and antenna meters may be seen above (4js), 4k1, 4pk, 4pv, 4rr, 4sy, 4tn, 4ut, 4un, 4xg, bad, (5bj), 5in, 5us, 5oq, 5pr, 5qk, 5uk, the inductance and the filament transformer 5wo, 5aiy, 5akn, 5amh, 5apc, 5xaw, 6cgw, to the right of the tube with the power rheo- Ocge, 8bf, 8bg, 8bq, 8bt, 8ci, 8ef, Bej Bfj, 8fm, stat on the wall above. 8fu, 8gp, 8gz, (8jq), (8ku), 8mc, (8rh), 8rj, (8sr), (8vq), 8xs, (8zw), (8aaj), Baer, Baas, The receivers are a Westinghouse RC, two (8ago), Baig, (Sail), (8aip), (8ajn), Bald, three -circuit tuners and a low loss tuner. 8amd, 8apw, 8apy, (8avd), Bavl, (8aws), With this tuner and one step, F8AB has been (8axd), (8ayb), 8bfe, (8bir), 8bit, (8bkh), (8bkm), (8b1p), (8bnh), 8bos, 8bow, Sboy, heard 20 ft. from a loud speaker. To the (8bp1), 8brc, 8brg, 8bvd, (8bvr), (8byk), right of the two three -circuit tuners is a 50- Readers are invited to send in lists of call, (8byq), (8cdc), 8cdx, Scei, Schp, Behr, 8chv, watter in the IDH circuit. The plate volt- heard from statións distant 250 miles or mere 8cip, 8ckm, 8cmh, (8cmu), (boon), 8cnw, (8cwp), (8cwr), (8cyi), (8dae), (8db1), age is furnished by an 800 -volt M. G. and from their own station. (8dbs), 8dec, 8dem, 8dfm, Bdgo, 8dgv, (8dha), (Sdnf), well filtered. The antenna current is 4 amps. By 5KC, V. Rosso, Plaquemine, La. 8dhd, 8dim, (8dki), 8dme, (8dmt gra4), on 150 meters. This set is used for short 8doe, (8dsc), (8dsn), 8dtc, .9ck, 9gp, (9gs), (4dx), 4fs, 4k1, 5es, 5fm, 5in, 5ka, 5mo, 5nw, 9hw, 9kd, 9mf, 9pq, 9ta, (9uc) (9zt), (9aau), distance ham work, and also to broadcast (5oq), 5qh, 5qk, 5ro, 5sk, 5vo, 5xv, 5aam, 5aen, 9abt, 9ado, gall, 9afz, 9alb, 9amb, (9auc), 9aud, the college basketball games. 5ag1, 5aiy, 5ajh, 5amo, 5aom, 5xab, 6cgw, Scy, 9azx, (9baz), (9bcb), (9bed), 9bpd, (9bvn), A wave meter and a spare 250 -watter Bfj, 8azh, 8da1, 91e, 9qw, 9x1, 9zt, 9acq, 9alb, (9bwf), 9bye, 9byj, 9caa, 9cco, (9ccw), 9cee, 9amb, 9ayx, 9bkk, 9ccw, 9cip, 9der, 9dou, 9dpx, 9cfi, 9cfk, 9cfs, 9cfv, (9cgr), (9cho), 9cip, complete the equipment. 8UF -8XBH has 9dwx, 9eht. Mexican: lf, bx. 9ckr, 9cmr, 9csa, 9csg, (9ctf), (9cvf), (9exx), worked every district as well as France and 9cze, 9cz1, 9dbm, 9dct, 9dfz, 9dga, 9dhz, (9djz), F8AB and G2KF having been By 6ANY-6AOF, Box 98, Hilo, Hawaii, T. H. 9d1n, 9dma 9dmj, 9dms, 9dpx, (9dqu), 9dre, England, 9dsz, 9dtk, 9dtt, 9dvw, 9ebh, most. 4jj, 5cn, 5ga, 5gg, 6as, 6aak, 6aao, 6adt, Oafs, 9dsa, (9ds1), worked the 6afm, 6agk, 6aic, 6ajf, 6akq, 6akw, 6a1g, 6alu, (9efz), 9elb, (9e1d), (9eli) 9xbb, nfk, (kftu). 6a1v, 6atf, 6atk, Oavj, 6awt, 6bw, 6bdb, Obfw, I. C. W.- (lck), lkv, (ixu), (lanx), lbbo, 6bqa, 6bou, 6bvg, 6bwl, 6cbb, Ocbe, 6cdg, 6cdp, (lbpz), 8hd, (3gc), 31g, 8zo, (8edk), 5wo, THE SIX- HUNDRED GETS IT 6ce, 6cde, 6cgs, 6cgw, 6chx, 6cmi, ócge, 6cto, (8ku), Baer, 9arf, (nrg), vdm. IN THE NECK 6cul, 6gt, Ogu, 6ko, 6kw, 61i, 6mg, 6ne, 6nb, Fone- (lalj), 4dx, 8brc. 6nk, 6nr, Orn, 6ti, 6wp, 6zp, Ide, 7iw, 7akh, 7mf. Spark -lash, 4fg, Sty. By L. W. HATRY Would appreciate reports on mi sigs. All cor- Canada C. W.- (lar), (lbo gra4), lbq, ldd, respondence ans'd. Qtc fer Hawaii should be ldj, leb, lef, (lei), laar, 2be, 2cg, 2fo, 8bq, Sfo, a a switch 9:00 p.m. 3gg, (She), 31e, (3kg), Skq, 31y, 8ms, Sni, Half switch, half routed via 6agk. Hawaiian quiet hour 4cn, 4cr, to 11:30 p.m. pst. (3oh), 3uj, (3yh), (3yh), Sze, saes, Half a switch retarded 4hh, 5cp, 5gu, gal, 9bc, 9hc. any From my four tubes TALI, James Wallace, Mt. Vernon, Wash. Please qrk 2wz 50 watts. Will qel to By who ask. The rampant six- hundred. ibbo, 5ns, 5aaq, 51r, 5qy, Oadb, 6agk, 6alc, (6alw), 6amm, 6atn, 6avj, 6avm, 6awt, 6bbh, Astoria, Ore. Over the light blockade, 6bcp, Obdt, (6bls), 6bwl, 6ccb, 6cek, (6cg1), At 7AIX, by Sam Spittle, Plumb through six lamps turned red 6cgw, 6chl, 6cjj, 6cka, 6cgo, 6orr, (Ocre), Ogu, C. W. -5ux, 6abo, Gaga, 6agk, 8akz, half, 6bc1, 6bcp, Obea, Blowed out six fuses fast (61i qra?), 6nk, 6p1, 6pu, (6rf), firm, 6ry, Oti, 6a1g, 6amo, Oasv, 6awt, 6bcf, (6ub), (6xad), 6zco, (7aeb), 7mn, 8cwu, 8zwp, 6bff, 6bgh, Objx, 6bmu, Obgr, 6cej, 6cfz, 6cgw, Did the six-hundred. 9amb, 9caa, 9cil, 9ckd, 9cpu, 9dnh, 9dpx, 9mo, Oche, 6cjj, 6cmi, 6cmu, 6cng, Oji, 6jj, (6jp), 9mf, 9zt, boh, Opi, 6xad, 7ahs, 7pj, lob, 7s1, 8det, 8xs, 9cee, "Forward ! Be not dismayed, Can.: 4av, 4br. Fone -6ry. 5 -Watts CRAC- 9ag1, 9amb, 9auu, 9ayo, Obis, 9bmu, 9bgy, Copper won't melt," I said; CW hr pse QSL if u hr me. Cards to above on Oeii, gent, 9dct, 9dug, geld, 988, waf. request es gld to hr fm them. Spark -7jm, ione (7akk), 7qc, kdka, Can. I closed the switch and knew, 4bu, 4dq, 4gt, 4hf, 4hh, (San), 5bf, 5bj, 5gf, Someone had blundered. By 6ALV, Alameda, Calif. (5gg), (5go), (5hh). Will gal on Four tubes made no reply 4yy, c4ab, c4dq, 5dw, 51r, Pse qs1 if you hr my 5 watter. lxam, 3ccu, 4oh, any of above. Theirs not to reason why 5me, 5rg, 5ov, 5ajj, 5xt, 5xat, 5amo, 6ceu, Ser, do or fry 8tj, 8p1, 9mc, 9q1, 9aap, 9aau, 9abc, 9adp, 9ahz, Theirs but to 9aim, 9bdf, 9bkf, 9boz, (9caa), 9cju, 9cwj, 9cxp, By BRY, Sullivan, Ohio, during July, 1924 As through all obstacles 9d1m, 9dpr, 9drw, 9dte, 9dww, 9dwn, 9eae, 9eky, lei, lka, lmy, lqr, labs, laic, lalj, lany, Came the six -hundred. 9cjy. All hrd on detector and low loss Haynes laos, lare, larf, laur, laxa, laww, lbdx, lbes, DX receiver. ibie, lbjg, lblb, lboa, lbvr, lbvv lbwj, lbzp, Chokes to the right of them lcmx, lccz, lcjm, 2bm, 2ev, 2pd, 2mo, 2mu, At 3APV, B. J. Kroger, 205 Taylor St.,. 2rb, 2sy, 2wz, 2auf, 2bqq, 2bsc, 2cac, 2chg, Chokes to the left of them Chevy Chase, Md. 2cvu, 2cyq, Say, 3bm, 3du, 3fr, 3hs, 3mf, 8oe, Svh, Chokes in front of them 6aao, 6aaq, 6aay, 6abk, 6acm, 6adt, Oafs, 6afq, 3pq, 3qj, 3qt, 3aap, 8acr, 3aoj, Sapi, sape, 6ajh, Oajj, Scdk, Sauv, 3auw, 8bay, 8bva, 8cbx, 8chh, 8cjn, Chattered and hummed; Gage, 6agk, 6ahc, 6ahp, 6ahu, 6ajf, 5gp, 6ajp, 6ajt, Oak, 6akw, 6akz, balk, halo, Oame, 4dv, 4eq, 4fg, 4ft, 4js, 41j, 4si, 4sy, 4tj, bin, Warmed up as hot as hell 6arf, 5ka, 5qh, 5ua, 5uk, 5wi, 5wk, 5aiu, 5ajh, 5amh, Gams, 6amw, 6aoi, Oaos, 6aou, Gape, barb, 9ado, 9agl, Boldly they glowed and well, 6asb, fisso, 6asr, 6aur, 6auu, bava, Oavr, Oavv, 5apc, 61v, 6bcl. 6cgw, 9pq, 9tg, gem, tubes, as volts, 6bcl, 6bcp, Oahu, 9aks, 9alx, 9aub, 9aud, 9bcx, 9beb, 9bew, Did the four 6awq, 6awt, 6bbc, 6bbu, (6bbw), 9cpu, 9cuh, 9dhs, And much amps as well 6bcs, 6bdi, 6beo, 6bfg, 6bh, Obit, 6bih, 6bjc, 9bkq, 9bmk, 9bnu, 9bwf, 9ccw, 6bjj, 6bjq, 6bjx, 6bjy, 6bkl, 6blw, 6bm, Obmx, 9drr, 9eka, 9ela, geld, geli. Charged by six-hundred; 6bgl, fibra, Special -lxu, lxae, lxak, lxay, 2xab, 2xi, 6bnc, 6bnt, 6bnu, 6bpz, 6bqb, 6bge, 5xab, 5xaw, 5zas, Sxaq, 8xbp, 6brf, 6brk, Obru, Obsg, (6bui), 6bum, Obuo, 6bur, 3zm, 4xi, 4xz, Flashed all the wires bare 6bwz, 9xbb, 9xbd, ak5, nkf, whu. 6buw, 6buy, 6bva, 6bve, 6bvg, 6bvr, 6bwe, Clbq, Clef, C2be, C2cg, in air Ocbg, 6cbi, 6cbu, Ocbw, Ecc, Ecco, Canadian - Clar, Insulation burned 6cbb, Ocbd, C3bi, C3co, C8fc, C3gg, C3gk, C3kg, 6ccy, 6cdg, 6cdn, 6cek, 6cfi, 6cfm, Ocfy, 6cfz, C3bd, Gassing the fambly, where Ochv, Ocix, 6ejb, C31y, C3m1, C3ni, CBph, CBsp, C9al, C9bc, C9bg, while 6cgd, 6cgg, (6cgw), Oche, fichu, vdm. West coast pse note tt BRY is wkg pure They stood awestricken, 6ejc, 6ckp, dekr, 6ckw, 6clr, 6cmr, 6cmt, 6cng, Meissner. 6eb, (ten, Ofh, DC note on 155 meters with Four Coil I stood and wondered; 6cnh, fieni, 6cse, Otte, 6cu, bea, QRV between 0680.0930 GMT. Plunged in the battery smoke, 6fp, 6gh, 6gr, 6gt, 6ja, 6js, 6ka, 6km, 61i, 61u, 6nx, 6of, 6pe, 6p1, firm, 6ry, my newest choke, 61v, 6mg, 6mh, 6nb, Parkman Ave., Right through Otc, btu, Otv, 6vd, 6wt, 6xh, 6xp, 6xs, 6zag, By 5ANE, Walter W. Merkle, 804 Spark gap and safety fuse, 6zah, Ozar, 6zau, 6zba, 6zbk, 6zbl, 6zg, 6zh, Selma, Ala. Unfazed by plate like coke, (6zp), 6zw, 6zz, 7abb, 7aby, 7adg, 7adq, 7adr, lees, lbdx, lajp, lgv, 2ayp, 2cee, 2crq, 2kx, sundered; 7aea, 7af, 7afe, 7afn, 7agr, 7agv, 7agx, 7ahi, 2nz, 3sh, 3oe, 3dop, 8zo, 8cd, 3be, 3bha, 3abw, Shattered and 7ahv, 7aif, 7aim, 7aiy, 7ajd, 7ajt, 7ald, 7alk, 3bmn, 3anj, 31g, 3mo, 3bua, Soh, 3aow, 3cdk, Sparkled on as ever was, (7bj), 7co, 7dc, 7du, 7fd, 7fq, 7fs, Igo, 7gq, 3er; 4's and 5's too numerous; 8bh, Bwy, 8bp, The lively six -hundred. 7gr, 7hg, 7if, 7ih, zio, lip, 7it, 7iy, 7ks, 7kv, 8aip, 8vq, 8bkh, 8dec, 8dpp, 8kc, 8aap, 8bvr, 71r, 71u, 71y, 7mp, 7mx, 7nt, lot, 7qd, 7qc, 7qj, 8apw, 8cpk, 8bks, 8dd, 8zz, Berne, 8brc, 8wa, Sparks to the right of them 7sc, 7sf, 7sh, 7to, 7tq, 7uk, 7we, 7wm, 7wp, 8bmt, 8avx, 8doe, 8bit, 8rj, 8dem, 8dhe, 8dwt, 7xae, 7xba, 7ya, 7y1, 7zd, 7zu, 7zv, 7zx. 8cy, 8bv, 9brc, 9chg, 9eld, Scud, 9cco, 9cvs, Sparks to the left of them 9dbf, 9brp, 9bvq, 9cdo, 9bkk, 9auc, 9acq, 9bka, inside of them 9dkk, Obit, 9rd, gum, gads, 9ao. Sparks right N. Y. 9ako, 9cfi, Volley'd and thundre'd: By 2WZ, 654 East 23 Street, Brooklyn, All crds from above answered. Hy u hrd mi C. W. (lah), (leg), (ici), (ida), ldb, 10 watt ACCW? QSL pse. Warmer than hot as hell, (lde), (les),- lgb, lgv, lka, (lmy), (loa), low, While clips and wire fell, (lpa), lpl lpy, lqr, lrb, (irh), lvk, lxw, lul, By 6OLP, Box 64, Empire, Calif. Th' transformer had gone as well, lum, (lzd;, (lzg), (lzp), (lzt), (lzw), (lzz), 5ajh, laac, (laal); (labf), (labs), laea, (laeg), labf, lnr, lxae, lxz, 2xi, 8xi, Sail, Came through the jaws of death (laei), (laeo), (lait), (lagt), (laid), (lajo), Same, 5dw, 5in, 5js, 5q1, 5qr, 5vo, 6bnf, 6cjb The four tubes, clear as a bell, (larf), (tone), 6crs,6ejy, Oadh, (7abb), 7agf, (7agz), lakz, lamw, (lanh), (lanx), (lare), (7gv), (7jp), 71g, Though not much was left of it, (laur), lavj, lavi, lawl, (lawy), (laxa), (7av), leo, 7fc, (7fs), (7gr), (laye), lazr, (lbbe), lbbo, (lbcc), (lbcu), (71e), (7mf), 7mx, ltd, (7no), lox, 7wp, (7zw), Left of the six -hundred. (lbdx), (lbgt), (lbip), lbjg, (lbjo), (lbkk), 8brc, 8cei, 8daa, Ser, 8fm, 8ug, 8xbp, Bxe, Syn, (lblb), lblx, (lboa), lbpp, lbpz, lbqk, lbgi, 8yv, 9aci, 9aed, 9aem, 9aii, 9aim, 9amb, 9ami, I'll use a rusty spade (lbvb), (lbvl), lbvv, (lbwd), lbwj, (lbzc), 9apz, 9azx, 9bdq, 9bkf, 9bob, 9bri, 9bsp, 9bw, Bury the transformer I made, (lbzp), (leak), loba, (lccx), lccz, (lcjc), lcjd, 9caa, 9cai, 9caj, 9cbf, 9cee, 9cjm, 9cjt, 9cju, When all the gang wondered; lcjg, (lcjm), lcjq, (lckk), lcmp, (lcmx), 9ckj, 9ctr, 9dem, 9dhy, 9dqu, 9dvw, 9dwk, 9dxq, (lcpc), 1cpf, lcpo, lcqk, (lctw), loue, (ixax), 9dxy, 9ebh, 9edc, 9eld, 9eli, 9xax, 9sb, gas, 9su, I couldn't do it right (2bm), Bay, (3bm), 3bq, (3bz), (8dk) 3ek, 9yy, 9zt. Can. -3aa, 3bk, 3er, 4aw, 4bk, 4dq, And use the city's light 3fr, (3gc), 3hj, 3hs, 3mb, 3me, (3mf), 3mo), 4fz, 4gt, 5ct. Porto Rico -4je. All crds an- To furnish six- hundred. (3oe), 3oq, 3ph, (3qj), 3tp, 3ts, 3uq, 3xx, 3zg, swered. Pse QSL my 5 watts. RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com FROM THE Rt1DIC1 M; VFACTURE RS

Filkostat compression type rheostats are now provided with a small nickel -plated s w i t c h whereby the A battery may be turned on or off without disturbing The Volt -X ball -bear- screw. the adjustment of the The best oper- resistance. ing variable grid leak ating point in conjunc- This switch tion is attached to the regu- is a protected unit with any tube lar Filkostat mounting may be found by trial whose resistance may once and for all. It is screws on the front of be varied from % to the and requires smooth in operation panel 15 megohms by turn- and no extra holes. claimed to not ing an adjusting wear out.

The Super -radio audio - frequency unit consists The new General Ra- of a transformer, rheo- dio variocoupler is de- stat and socket all signed for compact- ready for panel ness, lightness and effi- mounting. Only two ciency. Yet it has screws are necessary ample turns on both for mounting. Rheo- primary and secondary stats are supplied for to cover the band of either 8 or 30 ohms. broadcast wavelengths All socket parts are from 150 to 600 meters. properly marked to fa- It has but two taps, cilitate connection. The one at the center and trar?sformers have a the other at the end of turns ratio of 4 to 1. the primary coil, thus The unit is designed minimizing losses to save time, trouble when used with a and space in the as- good condenser f o r sembly of any home- tuning. made set.

The Remler Variable Capacity Unit is a new condenser consist- The Low Loss Tuner, for use in regener- ing of two sets of ative circuits with square b r ass plates, or without radio- both sets being rotated frequency amplification, has been de- about a common center signedwithminimum so as to interleave losses in the coils and mountings. The ama- through a 90- degree teur type covers the arc. A spur gear driv- band from 80 to 225 ing shaft gives vernier meters, and, by tap- ping the secondary control of the twin - coil, will cover the gear rotors and 360 - range from 45 to 110 degree dial motion. meters. The broad- S111 I '+*IjI-'I,d?.!. cast type tunes from The maximum setting 250 to 550 meters. gives a capacity of Together with appro- .0005 mfd. and the RADIO 5NOINEERINO LAB. priate low-loss con- n'EW YORK CITY, densers, this tuner minimum .000003 mfd., -s' 'r gives greatly in- a ratio of 165 :1. The creased sensitivity and selectivity. wavelength cur v e is practically a straight line between dial set - Continued on page 72

}? RADIO FOR SEPTEMBER, 1924

www.americanradiohistory.com What ACME means by a guarantee

THERE are no ACME seconds. All and insurance on the future. ACME has ACME transformers are rigidly in- grown by making a superior product and spected. Take the coils on audio -frequency making good should a defect in material or transformers, for instance, thousands of workmanship develop. Frankly, we can not turns of small wire -one short circuited afford to put out a single inferior article. turn, and out they go. Take the radio -frequency transformers, Acme Engineering Service each one of them tested in a radio -frequency YOU think you are not getting the amplifier and if they don't give a standard IFproper results with Acme Apparatus, amount of amplification at three different write to the Acme Engineering Service, 360 -550 meters) out they wave lengths (250- Cambridge, Mass. Send 10 cents for 36- go. page book -"Amplification without Distor- You may say, "Why the rigid inspection? tion," which contains many diagrams and The user can't make these tests," and we'll valuable hints on how to build a set and how say "Insurance." Insurance on the product to get the most out of it. ACME APPARATUS COMPANY Transformer and Radio Engineers and Manufacturers Dept. 80, Cambridge, Mass.

ACME APPARATUS CO. Dept. 80, Cambridge, Mass. I enclose 10 cents (U. S. stamps or coin) for copy of new edition of "Amplification without Distortion," containing many wiring diagrams and valuable hints on how to build a set and how to get the most out of it. Name AC Street ^ for amplification City State

Tell them that you saw it in R_\DIO 43

www.americanradiohistory.com A non- inductive Potentiometer that insures noiseless tuning

The Centralab Non - Inductive Potenti- ometer for panel mounting has no sliding contacts or wire wound resistor. Contact is made upon a resistor consisting of a graphite strip, by a patented rolling circular disc. This potentiometer makes tuning noiseless. It permits the free flow of high - MIEILCO-SUPREACE frequency radio current without choking or retarding waves. It makes possible the adjustment of the resistance, without steps, for the finest gradations. It does VOLUME ECEIVIER away with the need for a shunting condenser. Single hole mounting. CLARITY Tuned -Frequency No. Radio 110 -400 ohms (for ordinary use) . . . $1.50 No. 111 -2000 ohms (for special applications) 1.75 BEAUTY Centralab Centralab Centralab Just as bridges link neighbor- RHEOSTAT ADJUSTABLE GRID BATTERY DISTANCE ing cities so does No. 206- LEAK SWITCH the Melco 6 ohms,$I.25 No. 106 -$1.25 Supreme link the happenings of No. 230-30 No.107(with.00025 No. 300 - SIMPLICITY even the most distant towns ohms, $1.25 condenser), $1.60 soc with your own fireside. TO JOBBERS AND DEALERS: The trade SELECTIVITY mark of products of the Central Radio Laboratories has been changed from CRL "Satisfies Every Radio Wish" to Centralab. Write for literature.

Complete descriptive literature on request

CENTRAL RADIO LABORATORIES 295 Sixteenth St. Milwaukee, Wis. AMSCO 1IWJNJCTS INC FAIRBANKS BUILDING .$roome &Lafayette Sirs New York WESTERN BRANCH 447 PACIFIC BUILDING, SAN FRANCISCO

Registered U.S Patent Office AN IMPROVED AUDIO Mica Insulated Core laminations eliminate howling and squealing so prevalent in ordinary trans- RADIO MAP OF THE formers. The SUPERTRAN, therefore, assures U. S. 3 unusually long distance reception with pleasing For Sale by clarity. !!/rile for instructive literature 35c FORD MICA COMPANY, Inc. Pacific Radio Pub. Co., Inc., San Francisco 33 E. 8th Street New York

44 Tell them that you saw it in RADIO

www.americanradiohistory.com G Plug the little leaks and save the DX stations YOU EXPERIMENT with circuits ... you study ence your results. Every place where there's a the design of your transformers ... you select your connection offers radio energy a chance to escape. to tuning instruments with care ... you keep your bat- And every small part offers you an opportunity DX list teries fresh ... and still you just miss DX stations make your results better ... to make your you particularly want to get! longer! -CO small parts will help you -if you'll use Why do you miss them? Why must others, using MAR them wherever you can -and insist on getting the same circuit, continue to make records you can't -CO when you buy. Skilled craftsmen make equal? MAR MAR -CO small parts ... and they make them with Is it because there are unexpected leaks in your the precision of scientific instruments. They make equipment? Are some of the smaller parts -the "little them to stop the little energy leaks ... to add miles things" you don't pay misch attention to -are they to your range. draining energy away? It will cost you no more, frequently less, to say Why man, there's not the slightest little switch, the MAR -CO -and you'll know you're getting leak -proof most unimportant little accessory, that doesn't influ- service!

PLUGS JACKS RHEOSTATS SOCKETS SWITCHES NEUTRALIZING CONDENSERS

F A B E

?all...;,:.. ,,.:.,; `>;\ .`;\1. : '

Illl 199 sockets, amen control must b,. not Snap -and all is silen Snap MAR-CO U.V s EliminateNad shor circuits wi h Fi Ni h ig adds the pro essional name. sums up MAR CO h pressure contacts, ical, but steady And again-and recep ion contin w. with home -made set SHUR -GRIP p ug. No tools MARCO SHUR-GGRIP jacks on y cr ouch u the ues instantly. Make your set Bakelite base, with single Formica - insulation, sterling it is -when you use compact ike the striking beauty of needed to change tips instant- tonight with mounting screw and heavy leak -proof con- silver contacts, hooked termi- MAR-CO ARMOR CLAD go convenient- - MARCO gold-plated betels ly-to make filament battery felt cushion supplied -give In nals for quick, leak-proof con- ohm rheostats -a big one a MARCO J5 cents. Black finish al cents nections permanently. your REAL tube protection for nections no cents to $t.00 dollar's worth. switch, only so cents at Nickel 20 cents. Bashing black and nickel for cents. it. dealers '75 75 cents. and well worth

Tell them that you saw it in RADIO 45

www.americanradiohistory.com BRASS -POUNDERS OF NIPPON Continued from page to the other hand, even though he is a chief on one of our largest passenger liners, is paid and rated below the third mate. The status of the Japanese operator appears to be at once a cause and a result of his dignified and officer-like con- duct aboard ship. The American operator is rushed through school in eight months or a year and goes aboard ship with a total lack of experience of the sea and its customs; whereas the Jap has been through the mill; he is pretty Why thousands of thoroughly educated, both from an Ori- ental and a Western viewpoint ; and he radio fans enjoy him has had to put in his time as junior, third, and second operator, covering a Because thousands of storage bat- period of seldom less than five years, before he finally gets the prized and teries are on the job, brimful of highly responsible chief brasspounder's energy, gaining clear, satisfying berth. radio reception for every word and It is enlightening to walk aboard a inflection. Japanese liner in port and find all three With a Tungar, the carefree bat- operators in the radio room sitting up to their necks in a litter of dismantled tery charger, in your home you spark gaps and machinery, buckets of can keep your battery tuned up to gasoline, coal oil, brass polish, and heaps get every single note of music, of sandpaper, chamois and tools, putting every recitation, speech or song. their set into shape for the next trip. Tungar charges the battery over- About the only way to catch us Ameri- night from the house current. can key shakers on board is to meet our Tungar is one of ships at the outer harbor with a speed the many scientific Sold by Electrical, Auto -accessory boat. Once! the American ship gets achievements con- alongside tributed by the G -E and Radio dealers. -particularly if in a foreign Research Laborato- port -you have about as much chance ries toward the won- of finding the brasspounder on board as derful development of you have of catching whales in electricity in America. -_ Sahara. The radio equipment on most of the Tungar Battery Charger op. - ____ REG U S. PAT OFF erates on A lternating Current. unar Japanese ships is getting obsolete ; but Prices, east of the Rockies (6o cycle Outfits) -2 ampere - BATTERY CHARGE R such exceeding pains are taken with it, complete, $18.00; 5 ampere at least on the larger vessels, that ap- complete, $28.00. Special Tungar -a registered trade mark -is found only attachment for charging 72 or on the genuine. Look for it on the name plate. paratus fifteen years old looks like new 24 cell "13" Storage Battery and works better. You can see your $3.00 Special attachment for Merchandise Department charging 2 or 4 volt A" face in every piece Storage Battery $1.25. Both General Electric Company of metal and hard attachments fit either Tungar, Bridgeport, Connecticut rubber. The standard Japanese shipboard transmitter is a seven -kilowatt, direct -coupled, quenched -spark set, of massive construction and fitted with a GENERAL ELECTRIC magnificent twenty -unit spark gap-all very closely copied from the most efficient German Telefunken equipment of 48 E-io fifteen years ago, -and, in view of the way it is kept up, there is small wonder r that the Jap signals fairly jar the enamel j ELECTRAD LEAD-IN off our receiver diaphragms every night : Fits right under closed window. Can be bent to lit ledges. Covered with 011 the Pacific. First- O V; Last" 11 fireproof insulating material, preventing grounding of circuits on The name "Teishinsho," often applied ' wet window sills. Takes place of INSIST ON THE SILVER 11 ungainly porcelain tubes and to Japanese radio equipment, is not a holes in the window sash. At 1 PLATED AIR CONDENSER `1 your dealers'. or order direct. name of the system ; it literally means FOR ELECTRAD, Inc. Dept. E YOUR RADIO SET. 11 428 Broadway Now Vnrk "communication department," nothing 11/ more nor less. In Japan, all radio apparatus is built, installed, and used under CRESCENT LAVITE RESISTANCES Distance! The Only Absolutely Non -inductive AUTHORIZED COCKADAY COIL extremely strict government supervision. 12,000 O -j Gets distant stations easily and clearly. Among the common folk no 48,000 Made in strict accordance with specifications amateur 50,000 by L. M. Cockaday, inventor of the famous transmitters are allowed of any kind 100,000 Cockaday Four Circuit Tuner. Greater volume. sharper tuning, maximum selectivity. whatever ; receiving is no less unlawful; Guaranteed. At your dealers- otherwise but lately permits have been issued to Special Sizes to Order write us direct. Price $5.50. Used in all Circuits. Dealers write for discounts PRECISION COIL COMPANY some powerful Japanese newspapers to CRESCENT RADIO SUPPLY CO., 5Liberty St.. Ja naies N.Y_ ?nn -r. (!pntrn Street New York* Continued on page 48

.l6 Tell them that you saw it in RADIO

www.americanradiohistory.com You'll find YOUR SET among the FADA Neutrodynes FADA, the pace -setter of Neutrodynes, leads again, presenting a new 5 -tube FADA Neu - trodyne in de luxe cabinets, thus supplement- ing the famous FADA "One Sixty." There is also a new 5 -tube FADA Neutrodyne at a FADA NEUTROLA GRAND Model 185/90 -A -This is the beautiful new price that is within reach of all. 5 -tube Neutrola, Model 185 -A, mahogany inlaid cabinet, with self- contained loud speaker, Whatever your radio wants may be, you can mounted on the FADA Neutrodyne Cabinet Table, Model 190 -A, making a de luxe radio fill with FADA radio. Appear- unit. Desk lid conceals panel when set is now them not in use. FADA Neutrola Grand. Price 4 5 price is a FADA (less tubes, batteries, etc.) $295. FADA ance, 3, or tubes, -there Neutrola. Price (less tubes, batteries, etc.) Neutrodyne to meet your desires. $220. In the de luxe models all connections are at the rear and there is plenty of cabinet space for dry batteries. The FADA Neutrola and Neutrola Grand have self- contained loud speaker. Woodwork is handsomely inlaid mahogany. FADA Neutrodynes give you the results selectivity, volume. They you want -distance, FADA NEUTROCEIVER produce natural tone quality. A child can Model 175 -A- Handsome mahogany cabinet, inclined panel and roomy dry battery shelf. operate them. 5 tubes -2 radio, detector, 2 audio. Price See the complete FADA line before you (less tubes, batteries, etc.) $160. make any radio purchase. FADA Line First public showing, Pacific Coast Expo- The Complete In addition to the models illustrated, the new sition, San Francisco, August 16th to 21st. FADA line includes the following: FADA 160 -A -"The receiver that has taken the country by storm." Four tubes. Price F. A. D. ANDREA, INC. (less tubes, batteries, etc.) $120. 1581 JEROME AVENUE, NEW YORK FADA NEUTRODYNE CABINET TABLE. Globe Commercial Co., Pacific Coast Representative Model 190 -A handsome mahogany base unit for either the FADA Neutroceiver or Neu - trola. Price $75. FADA NEUTRO- JUNIOR. Model 195 -A- A 3 -tube Neutrodyne with special circuit arrangement, one radio, detector, two audio stages. Price (less tubes, batteries, etc.) $75. 11..ANEO FADA RADIO PANEL. A panel- mounted FADA Neutrodyne, adapted for installation Ra ci i o in prominent makes of talking machines. f AD ANDREA INC. LICENSED BY D RADIO MANUrAC,

Tell them that you saw it in RADIO 47

www.americanradiohistory.com Continued from page 46 install broadcast stations, and the government is arranging "soon" to permit the general installation of broadcast receivers- though with strict limitations as to type of apparatus to be used, which presumably will have to be so designed as to confine it to broadcast waves only. A rather striking feature of the Japanese radio operator's position on shipboard is his unusual authority, which under certain conditions cannot be con- tradicted by the captain or even by the owner of the vessel. Every Japanese operator appears to be a naval reservist, When you sto for the nighti or he is at any rate a government agent p as well as a ship officer. He has nothing whatever to do with any commercial Throw up an aerial and tune in wireless company, but keeps all his records and accounts directly with the just as if you were at home Japanese government and cannot be much interfered with by anyone else. THERE is no reason why you should de- You can drill it, saw it, tap it, and bore it- Numerous reports of the control ex- prive yourself of radio entertainment and it never buckles, warps, or cracks. It is when you are away on a vacation. If your practically indestructible. ercised by Japan over many of her sub- home set is too jects in civil life, as in the case of these large and bulky, you can Celoron panels have been approved by build a small easily vacation set you can the U. S. Navy and the U. S. Signal Corps. radio operators, have been a factor in carry anywhere. They are used by the best radio manufac- bringing about our present drastic anti - The cost of your vacation set will be turers and by thousands of radio fans. Japanese immigration laws. The Japa- comparatively small. The battery of your You can buy Celoron Radio Panels in nese people must always be foreigners car will furnish the necessary electrical three beautiful finishes -black, oak, and among us, simply because of the fact current, and if you have a home set you mahogany. These never lose their lustre that the meeting of East and West in can take a tube and the "B" batteries or become discolored. from that. marriage is not acceptable to us, and Practically all good dealers handle never can be, if the white race is to sur- You should use the same care in select- Celoron Radio Panels. ing parts of your vacation set as you used vive. Mix yellow and white, and you when you built your home set. Buy de- get yellow -not white. The law is vital pendable instruments and then mount Send for free booklet and just ; but feeling about it in Japan them on a first -class panel. If you will clip out the coupon below and is intense, and will be for a long time to Use a Celoron panel and you help your mail it to us, we will send you an interesting come ; therefore, unless we wish deliber- instruments do their best work. booklet entitled, "` Getting the Right Hook- ately to build for a disastrous conflict Celoron, a bakelite material, is one of the up with Celoron." This little book is full upon the Pacific, it behooves us to con- finest insulating mate- of helpful suggestions rials known. It has tinue to act decently, not belligerently. forbuilding and operat- The American radio operator on the high dielectric strength ing a radio set. Send CELO RON western ocean, through his myriad con- and great resistance for your copypy now. It to atmospheric attacks. A BAKELI PANEL is free. tacts with the Japanese over the air, has a part to play in this, to an extent not generally realized by either himself or Diamond State Fibre Company the public ; and we can play our parts BRIDGEPORT, PA., and CHICAGO, ILLS. best by trying not to forget that the Offices in Principal Cities Toronto, Canada -London, England Japanese radio operator is just a plain ff you want to build a beautiful cabinet use Diamond State Fibre Co., Dept. R, Bridgeport, Pa. human being like ourselves. Please send me without charge a copy of the Vulcawood-the new cabinet material. If booklet, " Getting the Right Hook -up with Remember that Mr. Takomoto Nogo your dealer has not stocked Vulcawood, Celoron." My radio dealer's name is: write us. We will send you a pamphlet tell- on the Nippon Maru has troubles of his ing you how to make a Vulcawood cabinet own ; he is almost sure to be married, and will give you the address of the nearest Name dealer, who Vulcawood. with three or four hungry little Nogos sells Address to think about ; he has his income tax and his indigestion ; he pays outrageously high fire insurance on his paper house, especially since the Yokohama earth- quake; and maybe he wouldn't go to sea at all if it weren't for the mortgage SUPER- on his rice patch. Then pile on his desk a bunch of fifty or a hundred messages to send an abstract, some in English, HETERODYNE some in French, and the rest in any one Reprints from "RADIO" by G. M. 25c of a dozen kinds of Japanese ; and the BEST. Sent to any address for captain is a jumpy little fool who wants a lot of weather reports and compass 25 cents. a Few bearings and everything; and -well Mr. PACIFIC RADIO PUB. CO. Only Left Nogo has got to hit the ball. Pacific Building -S. F., Cal. "JAB, JAB, JAB de JOK, JOK, JOK : xxytoyw,yfs35damnstwpytrst !"

48 Tell them that you saw it in RADIO

www.americanradiohistory.com All Aboard! [For the biggest Fall and Winter Radio [Business in the history of the Industry

T IS generally conceded that the Radio business during the fall and winter of 1924- 25 will be the greatest in the history of the industry. The Chicago Evening American interviewed a number of leading manufacturers and jobbers and in almost every case received statements like those reproduced below: "Reports reaching us every week from our district offices throughout the country indicate that the coming Radio season will be the largest thus far experienced." Herbert H. Frost, Inc. "Everything is in favor of a very early fall business. The presidential campaign will do much to stimulate interest and result in early installation of sets." Music Master Corporation Chicago, second greatest Radio market in America, offers manufacturers a golden opportunity. And the Chicago Evening American, the newspaper that publishes more Radio advertising than any other Chicago daily, is the medium that reaches the greatest number of prospects. CHICAGO EVENING AMERICAN First in Radio

Tell them that you saw it in RADIO 49

www.americanradiohistory.com A VARIABLE "B" BATTERY Continued from page 22 the box of radium, and he was equally positive that it was the self-same party The World whom he had later overheard talking to an accomplice in Catalina over the radiophone. The robbery had occurred be- Oit Your Dial fore five in the evening and it was about 10,000 miles on a single Myers Tube -2 L.O., London, England, heard in Calgary, Canada -30 stations in one seven when Denny had returned from hour picked up with one Myers Tube -a few of the verified London Los records made by amateur operators. What results are Angeles. This would have allowed you getting? Put the world on your dial with París the robber ample time to cover the dis- New York tance from Pomona to Citrolia, and he Montreal had probably chosen the latter as being Myers Tubes so much less open to observation. San Francisco The Practically description fitted his man exactly and Unbreakable Hawaii both the voice and the snatch of conver- They banish noise, tube hiss and interference because Sydney the leads are not bunched as in ordinary types. They sation which they had received over the function in any position -as Detectors, Amplifiers and Havana air his Oscillators -and you can't break Myers Tubes unless you strengthened conviction to a cer- deliberately try. Porto Rico tainty. If he could get over to Catalina Two types: Dry Battery and Universal for storage batteries. (4 volts) in the morning and locate his suspect, he Demand Myers Tubes at your could easily make sure if the voice of the dealers or send price and be supplied postpaid. See words phone belonged to the foreigner of the "Made in Canada" on each tube. Others not guaranteed. B. Myers Co.ltd. waiting room and if the latter fitted the Complete with clips ready to E.radio ?/acuum 7bes police description, he mount. No extra equipment would merely required. 240 CRAIG STREET, W. notify the local police and collect the MONTREAL, CANADA reward. It all sounded smooth and easy and Denny, resolving to carry it into effect, if possible, went to bed and dreamed of a wonderful combination chicken planta- tion and coconut farm to be purchased with the reward, which he felt was as good as his already. JOE refused to turn sleuth, deciding to go fishing instead and remarked significantly : "I expect to catch plenty, too, everything seems to be biting pretty freely up %i'teforyour this way today !" Denny ignored the implication, and after arguing vainly to persuade Joe to free copy accompany him he went off alone, telling Joe as he left : "When I buy my new yacht if I need a brass pounder I'll look you up." "You'll have to look up a long way then," Joe shouted after him, "I'll be tuning a harp when you buy a yacht." The first train with an all full sign Ward's Radio Catalogue flashed past Citrolia at high speed, the motorman, as he shot by, waving a friendly bye -bye in response to Denny's emphatic semaphoring for a stop. After of Radio Equipment at a saving. We a fifteen minute wait he caught the next, sell direct toyou only merchandise of high- but was too late to catch the train from A Valuable 68 -Page Reference est quality. Everything you buy from us, the Pacific Electric Depot that connected Place carries our 52 -year -old guarantee-"Your Book on Radio-a Market money back if you are not with the first morning boat to Avalon, for the Best in Sets and Parts satisfied." Enjoy the Long Winter Evenings and he pondered regretfully on the lost We want you to have a copy of Ward's Every form of entertainment can be opportunity of accompanying "Ivan" new Radio Catalogue. You will find it brought and of following his subsequent move- to be an encyclopedia of information on into your home by Radio. Keep in touch with the world- Sports -Elec- ments. Radio, the livest topic of the day. It con- tion Returns a new Radio map -diagrams of the -Dance Music-Speeches Arriving at the Catalina terminal at tains -Sermons- Current Events -you can best hook -ups-descriptions of complete enjoy them Wilmington he was wandering idly sets, and standard parts for building sets. all by Radio. Write today for your copy of this com- about when he observed the glass en- Headquarters for Radio plete Radio Catalogue. Address our closed operating room of the new com- Montgomery Ward offers you all types house nearest you: Dept. 39 -R. mercial station which had recently been installed in the immense waiting room. MontgomejyWardss &CQ He recognized the operator inside as an old shipmate of his, and was about to The Oldest Mail House is Today the Most Progressive Order enter when he saw that he was engaged Chicago Kansas City St. Paul Portland, Ore. Oakland, Cal. Ft. Worth in sending a message. Not wishing to Continued on page 52

50 Tell them that you saw it in RADIO

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Tell them that you saw it in RADIO 51

www.americanradiohistory.com Continued from page 50 "the superior tone quality interrupt, he waited outside the glass partition until the message was finished. Unconsciously he listened to the sharp of Erla Duo -Reflex circuits, snap of the signals, his brain mechani- cally recording the dots and .dashes and as well as their forming them into letters and words unmatched without any effort or volition on his part. His conscious mind was following range and volume, stamp "Ivan" across to Catalina Island when suddenly there seemed to leap from his them subconscious mind the very word "Ivan" as the most advanced and after a moment's startled pause he realized that it was the signature to the types yet developed "-----.-- message which the operator had just completed. He had some difficulty in concentrating his memory on the signals which the brain had automatically recorded, but finally succeeded in recon- structing the entire message. It ran - "Hr nr 1 ck 14 Wilmington fld 10.15 pm date -To Pedro Legaspi, SS Hondagua- Gained object meet you on arrival accompany you Mazatlan -Sig Ivan." He entered the operating room and greeeting the operator inquired casually Erla reflex transformers Complete Factory Sealed Parts for alone amplify at maximum when the Hondagua was due. The both received and refiexed Famous radio frequency currerts, Erla Circuits operator answered : "She gets in here to- without distortion. List, $5 FACTORY sealed cartons of complete parts now morrow morning and leaves for South make child's play of assembling Erla Duo -Reflex America and way ports tomorrow night. circuits, tube for tube, the most powerful built. Just gave her a message," he continued, Synchronizing reflex and audio transformers, tested "handed in by a funny looking bird." capacity condensers, balanced crystals, these and "What kind of a looking fellow ? other factory packaged units remove all doubt as Spigotty ?" Denny asked, trying hard to to selection of proper materials, while correct con- appear unconcerned. struction is made equally certain through a sten- "No, this guy was no spig," replied ciled baseboard, drilled and lettered panel, and the operator. "Looked more like a Rus- full -size blueprints giving the exact location of sian. Big heavy chap with a thick black Unique ability to amplify three stages without trace every nut, screw and wire. Soldering is eliminated mustache. Spoke bum English." of distortion proves con- by Erla solderless connectors. clusively the superiority of That was all the information Denny Erla audios. List price, $5 Examine a complete Erla demonstrating receiver required just then and he soon made an at your nearest dealer's. See how easy it is to build. excuse and left his friend. He was now Then make yourself a duplicate in a few hours' more firmly convinced than ever that he time. Your dealer will gladly co- operate. Or get was on the trail of the radium thief and in touch with us direct, giving your dealer's name. decided that any action in the matter Manufactured by Coast Representative must be taken promptly if he was to earn The words 'tested capacity,' Electrical Research Laboratories Globe Commercial Co, that $10,000.00 reward, as the culprit found exclusively on Erla Dept. H 709 Mission Street was evidently about to lose no time in fixed condensers, guarantee 2500 Cottage Grove Ave., Chicago San Francisco accuracy unapproached. getting as far away from the scene as Made in 11 sizes, 30c to 75cea. possible. Dealers and Jobbers -High turnover of Erla dependable When the boat returned from the is- radio products conserves land Denny invested capital while yield- stationed himself by the ing maximum rate of profit RIA gangplank and kept a sharp watch on the descending passengers but failed to see anyone remotely resembling "Ivan." He accordingly purchased a ticket and on the trip across concluded it would be advisable to have some expert assistance RADIO INSTITUTE OF AMERICA before proceeding further. As the donor of this assistance he selected his ex -army TRAINING IN ALL COMMERCIAL BRANCHES OF RADIO friend, Captain Watt, who in addition to being the uncrowned king of amateur If you cannot attend the Radio Institute of America in person the same instruction can come radio DX hounds, was also the sole cus- to you through our recently inaugurated "HOME STUDY COURSE " -Investigate. todian of the dignity and majesty of Uncle Sam on Catalina Island in his Detailed information free on request. capacities of marshal, justice of the Conducted by peace, game warden, forest ranger, etc., etc. THE RADIO CORPORATION OF AMERICA Denny knew that the Captain was at 331 Call Bldg. Phone Douglas 3030 San Francisco, Calif. his home on the island, having heard his

98 Worth St. Phone Franklin 1144 New York City Continued on page 54

5? 'tell them that you saw it in RADIO

www.americanradiohistory.com r a Ca i rats r _ . L a ,! -- for be iésûli . Yptt tpaa hè f-isTA resistance and adjustii Yòú Set it for à specified peep -hole ins the panel. (It'd terms of the megohm through a ltbrated._. tance in exact -KO.1 for. table mounting.) Each FIL equipped is cons t and, a curs éu n4c the laboratóry. Resistancence element i4óthcrr «1 èt a. wear. atmospheric conditions or tát ,Qw cld i You will gget both FIL KOand local `lct`çtt) Control of resistance. the negative bias ott the. Fir et the volume than ever before, for when "spills and right the tube neither "chokes" nor oe tube is precisely on the wectk&,t státia The improvement will be most noticeable and n e is guaranteed to be perfect electrically X2.0 Every F1L -KO -LEAK the operating xäïig and to be accurately calibrated over chanically, This calih>;átiou.is dsu y for all tubes (N to 5 megohms). before the instrument is shipped,

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Carries the usual FIL KO. PARTS A single -hole mounttñ T`- 7Datt y 'unconditional switch that's easy to attach. Suarantee. 'Bakelite Wiping contacts assure clean, posi Insulation tive connection when the switch is Hermetically in the "On" position. When the Sealed The oîil}, compression type rheostat switch is "Off ", the contacts have a with a battery switch attachment. positive break and are separated by 'Combines the advantages of infinite highest quality insulating material. control of filament current with the The end terminals of the switch can Absolutely warranted to protect your, simplicity of an ordinary battery set from lightning, with a guarantee be used for solder connections, or switch. And at no extra cost! If connecting wires can be held it to pay you $100 or to repair your set, you want perfect control of any should it be damaged through faulty place by the screws provided for type tube in any hook -up -if you that purpose. operation of the arrester. want freedom from tube noises- The "umbrella" shield keeps dust, hif you want DX stations you never The nickel knob and the entire house moisture, etc., from the insulation, heard before - maximum signal ing are insulated from the terminals,, preventing leakage losses from aerial 'strength -longer tube and battery so that any wires accidentally com- to ground. This makes certain that life- -then you must use FIL -KO -STAT. ing in contact with any part of the all radio impulses reaching the an- Battery switch attaches to regular switch outside of the terminale them - tenna pass through your set, which FIL-KO-STAT mounting screws. No selves can cause no damage, assures maximum reception. extra holes to drill. FI LKOR FI L KO -sTaT FI L-KO-SW ITC SCI ENTIFICALLY CORRECT SCIENTIFICALLY CORRECT RADIO LIGHTNING ARRESTER 'A' BATTERY SWITCH \11 rr//J Flr

Representatives MADE AND GUARANTEED BY For Descriptive Literature Foreign Address Dept. R 924 at the FACTORY RADIO STORES CORP. York City INSTRUMENT () HARRISBURG, PA New St. (Adds$$ niLMail to the Factoryt New York Office: 220 West 34th Tell them that you saw it in RADIO 53

www.americanradiohistory.com Continued from page 5= powerful transmitting set in operation on several nights previously, and on arriving at Avalon he went directly to the Captain's house. After a cordial welcome he gave the Captain all the details of the robbery and then told him of his conclusions regarding the suspect. He was much relieved to find that Captain Watt was quite impressed with his story, and when the latter suggested that they proceed at once to the St. Catherine Hotel to hunt for Ivan and his partner, Denny felt an unwonted thrill of ex- citement and elation. To the desk clerk at the hotel, the Captain repeated Denny's description of the fugitive and was informed that a Nine Out of Ten Sets man whose appearance he recalled, corresponding closely to the one described, had arrived earlier in the day and had Use Micadons ! taken a room on the fifth floor adjoining that of a Mr. Peterson, who had registered a few days before and had reserved both the rooms. Nine out of every ten sets made use Micadons the - Declining the clerk's offer to phone standard fixed radio condenser. Set builders choose them up and see if they were in, the Captain for many reasons. led Denny to the elevator and getting off at the fifth floor they walked quietly They know that the Micadon is a Dubilier product, hence along the corridor looking for the room supreme in quality and efficiency. numbers which the clerk had given them. "I'll ask to see his passport first," They know that Micadons can be obtained in accurately said the Captain, pulling a shiny badge matched capacities and that the capacity is permanent. from his pocket and pinning it on his lapel. "Those foreigners are used to They know that Micadons are easily installed, equipped that, and when we get inside we can question him a bit." as they are with extension tabs for soldering and screw - As they paused outside they heard eyes for set an screw assembly. indistinct muttering of voices within. The Captain They know that Micadons are knocked sharply on the made with type variations door of Ivan's room, but received no to meet every possible requirement. answer. The voices had ceased abruptly and after waiting a tense moment he For the best results use Micadons rapped again and receiving no response he tried the knob. The door was un- locked and he swung it open. They both stepped quickly inside only to find that the room was vacant, but muffled noises in the adjoining room indicated that the recent occupant had just vacated through the communicating door to Dubilier which the Captain rushed. CONDENSER AND RADIO CORPORATION He found it firmly locked and turned to dash out into the corridor when his at- N tention was attracted by an exclamation of amazement from Denny. The latter was standing by a little table in the center of the room on which lay a brand We Repair new 45 volt B battery, which had evi- RADIO TUBES dently just been removed from its card- WD -11, WD -12, UV- FROST-RADIO 200, UV -201, C -300, board container, and with the brown C -301, DV -6, DV -1, diC paper, outside wrapper crumpled on the DV -2, DV -6A, UV -199, THE name FROSTRADIO on a C -299, UV -201A, C- floor. Denny was pointing to it in open- 301A, Marconi Moor- piece of apparatus, whether mouthed astonishment head. FROST-fONES, Plugs, Jacks, and to the Cap- 6v. plain Detector, 6v. tain's curt, "Well, what's the matter ?" plain Amplifier Sockets, Rheostats, etc., means highest quality. Your dealer he replied : $2.50 for any type carries corn - "Say, Cap., this is my B battery. The Dealers' and Agents' Special Discount plete stocks. one I bought yesterday in Los Angeles. solicited and See him to- Mail orders Lookit here ! Here's where I scratched promptly attended to day. H. & H. RADIO CO. the date on it when I bought it!" P. O. Box 22 -M, Clinton Hill Sta., Newark, N. J. HERBERT H. FROST, 154 W. Lake St., Chicago They gazed at each other blankly. Continued on page 56

54 Tell them that you saw it in RADIO

www.americanradiohistory.com , r - Ì. l ey said it be couldn't I I J., ti_ 'Ir The requirements of a perfect reproducer are but three: I. Tone -quality 2. Volume 3. Sensitivity But for years engineers have failed to obtain ll these three qualities in a single instrument. Tone -quality? Exquisite tone -quality was obtained, but without adequate volume.

Volume? "Loud " - speakers were blatant without tone -quality and usually insensitive. Sensitivity? Sensitive reproducers chattered hopelessly on loud- reproduction. Acoustic engineers finally said it couldn't be done. ---- but Rola did it! For here at last is a reproducer that has all of these essential qualities. And it marks a new era in Radio reproduction. Here is a loud -speaker of such tonal perfection that comparisons are astounding. Of such sensitivity that any signal that can be amplified will be reproduced adding many miles to radio reception. And yet capable of tremendous volume on power inputs for it cannot chatter! There's absolute prooflin a demonstration. Hear it at your dealer's. Price complete with i4 -inch horn and cord, $360,0

s c,4 Product of THE ROLA COMPANY SEATïLE,WASHINGTON ' U S A Distributed nationally to the jobbing trade by rThe ROLA RI '(TREATOR horn is ex- aitivity exceeds that obtained In best headset ponential in taper and non resonant stony construction- anunparall edachtevement BAKER - SMITH COMPANY The unit can be audible frequency. The reproducer mech- in loud speaker design. Building San Francisco anism rnpondsovera frequency range from purchased separate from the horn and base, Call r,' tso, o ,cwhichispreaterthanthatachieved together with the necessary adapter for -with offices in the by present broadcasting stations. Die *en. attachment to any phonograph. :. pnncspal cities _- ,L - - 7- _ BAKER- SMITH COMPANY L. C. Smith Building Dept. A Seattle,Washington Çrnde+nen Please send complete information regarding the new Rola Re'Creatot.

Street City

L'sfy dealers name

Tell them that yo'u saw it in RADIO 55

www.americanradiohistory.com Continued from page 54 "But I brought it home with me to the camp last night, and how did it get here ?" he continued. "You're sure it's the same?" barked the Captain. "Certain," answered Denny, then as another thought flashed to his mind he grabbed the brown paper from the floor, "and I remember scribbling my name and address on this cover on the way home in the train!" Quickly he smoothed out the heavy PLUS CLEARNESS paper and found that a piece about six inches square had been roughly torn L,CCNSCD is a new receiving - -- all BF HERE set designed as fine from one corner. pOLYOYNe sets, to give volume, selectivity, distance and sim- EGST[NCo plicity of operation - -- But PLUS one feature that marks "That was where I wrote my name its superiority - -- `ORPORAn°" CLEARNESS OF RECEPTION. and -" he began to shout excitedly when The A -C Dayton POLYDNE XL -5 is a super, five tube the sharp slam of the door behind them Priced at 115.00, receiver that will enable you less tubes and acces- to honestly enjoy your favor- through which they had sories,the XL -5 repre- ite programs, Without annoyance of interference and dis- entered caused sents a wonderful value In a fine receiv- tortion. The XL -5 receives the finest orchestral and vocal them both to spin hastily around. ing set. (West of the music exactly as played Rocklos--á 120.00) with perfect clarity of modulation. Someone was turning the key in the True radio enjoyment will Reputable radio lob - be yours with this new receiver. lock. bars and dealers will Its mechanical refinements have resulted in a beautiful set, be Interested In a de- With a jump the Captain grabbed the tailed description of one that will fit the arrangement and decorative scheme the A-C- Dayton XL -5. of any room in the home. knob, but was too late. They were se- Our sales plan Is an attractive one. Write Your radio or music dealer curely locked in Ivan's room while the for complete Infor- will gladly demonstrate the . . mation. A -C Dayton XL -5 for you. Ask to see it - --to hear its re- latter and his accomplice slipped quietly GUARANTEED WITHOUT markable clearness of reception. Write for name of from the hotel to safety. RESERVATION the nearest dealer. For a moment both were dumbfounded THE A -C ELECTRICAL MFG. COMPANY, DAYTON, OHIO Makers of Electrical Devices for over Twenty- Years. by the unexpected turn of events. "The telephone," exclaimed Denny, rushing toward it. "No use," said the Captain. "Those birds are too quick. They'd be well away before we could explain things downstairs. They can't leave the island, though, before tomorrow, and then they can't get, away without our knowing it. But call the office anyway and tell them to send up a bell boy to let us out of here." Denny did so and then he and Captain Watt resumed their inspection of the B battery on the table. "I don't get you on this yarn," said the puzzled Captain, "you say you took the battery up to your place last night and left it there unopened. Then how in the name of all that's foolish does this duck get hold of it, and why ?" "That's exactly what I'd like to know Bedtime Morning too, "wailed Denny, as he racked his Stories Exercises brain for an explanation of the mystery. "Maybe you gave it to him as a pres- WHEN you own a Radiodyne the world's foremost entertainers and ent," sarcastically ventured the Captain, educators serve you. With this efficient receiving set you can bring "when you met him in the railroad wait- operas, sermons, lectures, dance music, etc., right into your home clear and ing room. Maybe you -" distinct on loud speaker no matter where broadcasted or where you live. "That's it!" Denny shouted. "That

must be it ! He must have picked up Uses Light VBW Outside or my package off the bench in the darkness, Socket for i N E Inside Aerial and I must have picked up a package be- o d longing to him by mistake. I wonder -, Antenna cl for Daytime do you think -could it be possible ?" 1 C "That's it !" it was the Captain's turn "I have no outside antenna. I just plug "Received Cuba, Canada, New York and to fill in the blanks. "Sure as you're a into the light socket. Picked up Omaha California on loud speaker with 70 foot foot high, you picked up the package of last Sunday morning at ten o'clock when ribbon antenna in attic. Also have a single 75 foot wire outside for radium and took it along home with the temperature was 95 and the sun daytime, volume you ! And say ! shining." Frank Williams, Winona, Minn. and distance." L. G. George, those two fellows must Fairmount, Ill. have figured it out that way too. That's Write for illustrated folder which describes the RADIODYNE in detail. Every radio fan will be interested in this new type receiver. why they've taken your name and address from the paper cover!" Western Coil & Electrical Co., 311 Fifth St., Racine, Wis. Continued on page 58

56 Tell them that Nu saw it in RADIO

www.americanradiohistory.com "THE AIR IS FULL OF THINGS YOU SHOULDN'T MISS"

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772 No. No. 767 Vertical Horizontal 45 -volt 45 -volt large size large size "B" Battery "B" Battery Formerly Illanufactured and guaranteed by Formerly $5.00 NATIONAL CARBON COMPANY, INC. $5.00 Now $3.75 Headquarters for Radio Battery Information Now $3.75 New York San Francisco

NEwf No . 770 Vertical 45 -volt extra large size "B" Battery for heavy duty on multi -tube sets and power amplifiers New low price $4.75

Tell them that you saw it in RADIO 57

www.americanradiohistory.com Continued from page 56 As they speculated intently on the possibilities of this discovery they were interrupted by the bell boy unlocking the door. "Let's get your partner on the phone BAKELITRADE MARn REG. D. 5. PAT. Orr. right away," said the Captain, "and have him examine that package and put it in safe keeping." "Can't do it," retorted Denny, "there's no phone line out that way !" For a moment both were silent. Then the Captain demanded eagerly, "Any ham stations out there ?" "Sure is!" Denny answered jubilantly. "Joe and I just helped a. young chap in Millers Camp rig up a five watter last Standard Insulation week. I know his call. Let's try and raise him on your set !" "Let's go!" said the Captain, and -wherever Dials turn they hurried to the elevator. With every facility for testing materials used in radio As they emerged to the hotel veranda work, the United States Signal Corps chose Bakelite for they were startled by the loud drone of the potentiometer base here shown. We also illustrate a an airplane and looking towards the Rogers Radiometer, Kellogg Condenser and Fil- Ko -Stat, beach they saw a hydroplane skimming all of which are Bakelite Insulated. with increasing speed away from the shore, and as they watched it lifted These critical radio experts, as well as the most inexpe- gracefully from water and headed have come the rienced amateur, to recognize the phrase "Made directly towards the mainland. The of Bakelite" as a guaranty of excellence in radio insulation. Captain turned and quickly entered a Bakelite enhances the value of any radio set. Its high telephone booth in the lobby. He called electrical resistance, stability and beauty of finish have the office of the airplane company, and led to its adoption as standard insulation by the large the answers to his rapid questions con- majority of radio manufacturers. firmed his suspicions. The fugitives had paid three times the a copy of our Radio Send for Booklet S regular fare for the trip across, with the privilege of landing wherever they di- Send for our Radio Map rected the pilot. "They're bound for your shack," the The Bakelite Radio Map lists the call letters, wave Captain told Denny, as they hurried BAKELITE length and location of every broadcasting station in from the hotel. "If we can't get word Condensite the world. Enclose 10 cents to cover the cost and we to Joe before they get there he's liable &D1MANOL will send you this map. Address Map Department. to be in a dangerous position. These are the registered Trade Marks for the crooks wouldn't stop at murder to get Phenol Resin Products manufactured under BAKELITE CORPORATION hold of that box of radium again. Let's patents owned by run to my place!" BAKELITE 247 Park Avenue, New York, N. Y. CORPORATION Chicago Office: 636 West 22d Street They arrived a bit out of breath, and in about ten seconds the motor -generator was humming, the big bottles glowing, the receiving set switched on, and the THE MATERIAL OF A THOUSAND USES Captain's well known fist snapped out the call letters which Denny jotted down on a pad in front of him. They held their breaths while the To Manufacturers of Captain slowly moved a dial on the re- 1r114oQ o ceiver, and then both gave vent to a Radio Receivers - RADIO TUBES- I oT9 "0 long "Ahh !" of satisfaction as the Cap- We will make horns or concealed loud speakers and -3-6- 4- B V. %Q Al7P. DETECTOR. 1. It sounding boxes to order, using Madera die-cast FIT cSTRAIDRRD SOCtiE WORK tain's call was repeated in a fist that be- wood in any size, shape, or quantity. r-¢' ON AfJY C/Qcu/T -('IAIL YOUR To trayed its newness in a slight hesitation Or, we will supply our regular Madera "Clear - anal 2. Speakers," in quantities, to be offered by you as HAY®ENSALESC®. and unsteadiness. standard equipment. This will insure the 100% JERSEY CITY - 3.J. performance of your sets and protect you from "Got him first pop out of the box!" being blamed for the "frightfulness" of metal loud speakers. crowed the Captain, as he waited for the AMERICAN ART MACHE COMPANY other to finish his call. Then he sent 357 West Austin Avenue Chicago, Illinois slowly and distinctly: "Can you get a Learn D10At Homei message to Joe Knapp?" "Joe is here now," came the reply. 2650 MILES Earn $70 to $200 a Week "Do you want him on the key ?" -with ONE TUBE. Broadcasting from Atlantic Coast and Become a recognized radio expert. Trained men in urgent Cuba heard in California by users of the CROSS COUNTRY demand as broadcasting and ship operators, radio salesmen, "Yes, yes," the Captain shot back, and CIRCUIT. This range is due to simplicity of set and engineers, demonstrators, etc. Hundreds of big pay positions operation as only one control is used for tuning. Easily now open. No previous training necessary. We train you in motioning to Denny to take his place, and cheaply built. Dry cell tubes may be used. Complete theory and practice. Instruments for practical work at home "You tell him!" he said. instructions, with panel layout, assembly views, etc., post- furnished free. First school to teach radio by mail. Thousands paid for 25c. Or further information for red stamp. of successful graduates. Get facts from Free Book "Rich Smoothly and rapidly and in the few- VESCO RADIO CO., Box R117 -Oakland, Calif. Rewards in Radio." Write today. State age. National Radio Institute, Dept. 10HA, Washington, D. C. Continued on tage 60

58 Tell them that you saw it in RADIO

www.americanradiohistory.com "ROLLS -ROYCE" TÚSES Like their name, significant of quality. Durable and powerful. Bring in distance with a maximum of volume and clearness. Type 200....5 Volts, 1 Ampere Detector Tube Type 201A 5 Volts, .25 Ampere Amplifier and Detector. Type 199..3 -4 Volts, .06 Ampere Amplifier and Detector. Type 199..3 -4 Volts, .O6 Ampere With Standard Base. Type 12..1 %Volts, .25 Ampere Filament. SATURN Platinum The New Amplifier and Detector "The Rolls-Royce of Radio Tubes." ALL Improved Automatic Radio Plug TYPES $2.50 Type 202....5 Watt, Transmitters, $3.00 better SATURN Plug- handier, ALL TUBES GUARANTEED value than to work in Radio Frequency. Especially adapted for Astillmore durable and greater Neutrodyne, Reflex and Super -Heterodyne Sets. Genuine Shipped Parcel Post C. O. D. ever at the new reduced price. When Ordering Mention Type (DN t. Rl Bakelite, no metal parts projecting to pro- ROLLS-ROYCE TUBE CO. N E W A R K, duce capacity effects or short circuits. Con- nected without a screwdriver or any other tool - just by inserting cord terminals. Strong automatic grip- instantly released by pressure on small release lug. Absolute- ly fool -proof. Efficiency unconditionally guaranteed. Reduced price 75c.

PERMANENT OFF The SATURN SATURN Battery Switch DETECTOR Perfect Jacks Product, built of the Easy soldering A new SATURN -, $150 terminals with same high grade materials and on the crowfoot offset, as tinned with non- same standards of perfection the corrosive solder Plug and Jacks. Perfectly flux compound. SATURN Rounded corner balanced because of exclusive blade brass brackets, nickel plated. construction. Switch pulled out makes German s i l v e r connection, pushed in, breaks connec- blades with sterling silver contact tion. Fits any thickness of panel. one part of your set points. List price 75c THEin which there can be no ON trouble; the one part that How to Buy SATURN Products majority of radio dealers. If your requires no attention. Attach SATURN Products are sold by the great dealer has none, send us your order, mentioning his name. Your satis- it- forget it! The most prac- faction with every order absolutely guaranteed. Write for our new circular. tical fixed, crystal detector - and the most attractive. The SATURN Mfg. & Sales Co. ..A Dept. B Slight Ì t: Sold by Good Dealers Every- Touch 48 Beekman Street Releases or Direct Upon Receipt ., ^. . where the Tips NEW YORK CITY of Dealer's Name and $1.50 ..

Patented May 15, 1923 Serial No. 1454997 THOS. L. KENNON C. E. THOMPSON Cable Address "KENNON" Infringement subject to CONSULTING 988 MARKET ST. REPAIRING prosecution. REWIRING Super- Heterodyne Authorities 804 -06 Loew Building ASSEMBLING All Work Unconditionally Guaranteed SAN FRANCISCO SCIENTIFIC APPARATUS Kennon Radio Laboratories CALIF. GREWOL DEVELOPED RADIO RESEARCH ENGINEERS 2 in One Crystal

Two surfaces instead of 9IIUIIIIIIIIIIIIIIIIIIIIOI only one. Double life, double value. The Romance of the Sea 50c each Read the Story of the Life of a Sea -going Radio Operator- "THE RADIOBUSTER" SENT POSTPAID ANYWHERE 1.00 .00 PACIFIC RADIO PUB. CO. Per $1 Copy PACIFIC BLDG., SAN FRANCISCO, CAL. Copy

Tell them that you saw it in RADIO 59

www.americanradiohistory.com CHARGE YOUR BATTERY Continued from page FOR 53 A NICKEL Crune in. est possible abbreviated words, Denny The Gold Seal Momcharger explained the situation to Joe and ad- Charges Radio and Auto Batteries vised him to go at home overnight for a nickel With up to their shack im- Your dealer has it. Write for ea se mediately, examine the package and if FREE booklet and list of broadcasting stations. their surmises were correct to get to- The Automatic Electrical Devices Co. 117 West Third St., Cincinnati, Ohio gether some of the menfolk of the camp to act as a reception committee for Ivan and his friend, in case they showed up THE there. "QRX, om," he finished. WORLD'S "QSU," snapped Joe. STANDARD Ten minutes later Denny flashed a LOUD SPEAKER "Go ahead" signal in response to Joe's call. "It's the radium, alrite, otn," came Now you can the message. "We are all set for Ivan's arrival. Two shotguns, two air rifles, and an automatic. We'll take care of UNDERSTAND them." RADIO! And they did. When a furiously driven9taxi con- Take the mystery out of it- taining Ivan and Mr. Peterson halted in build and repair sets- explain Millers Camp with screeching brakes, a the vacuum tube- operate a willing bystander directed them towards transmitter a radio -be expert! the operators' shack, and with no pretense at concealment the two passengers 1 VOLUME N D jumped out and scrambled up the trail 514 PAGES to the little building. No lights were showing and the place looked deserted, Compiled by Super DeLuxe Dials HARRY F. DART so throwing caution to the winds, the E.E. Where eye and hand are pair boldly approached and finding the Formerly with the in scientific,balance door open, walked in. Western Electric As Co., and U. S. they stepped inside they were Army Instructor Test these dials with any fumbling in their pockets for matches Radio. other and see how much of more quickly you can turn when the door was banged shut, lights to any degree or fraction of a degree. Shorter intermedi- flashed up and before they could collect ate lines, numerals on the Technically Edited by F. H. Doane bevel and a generous knob their scattered wits, they were over - are the reasons. 100,000 ALREADY SOLD powered and bound hand and foot. This practical and authoritative Handbook is considered the biggest dollar's worth in radio AND that is really about all there is to -day. Over 100,000 homes rely on the I. C. S. These are truly beautiful creations which give that to the story itself, because, of Radio Handbook to take the mystery out of radio. final touch of dignity and Why experiment in the dark when you can attractiveness to the quality course, Ivan (his last name turned out quickly learn the things that insure success: set. On the set you buy look to be "Offalkoff ") was convicted and Hundreds of illustrations and diagrams explain for the minute Na -ald trade- everything mark as you would for "Ster- sent to jail, and so was Mr. Peterson, so you can get the most out of what- ling" on silver. ever receiver you build or buy. as his accomplice, and naturally Denny It contains: Electrical terms and cir- collected the $10,000.00 reward when cuits, antennas, batteries, generators 75c. Other prices of Na- he the radium to the Univer- and motors, electron (vacuum) tubes, ald Dials are: 3 %' 50c. 3 returned 35c and 2' (rheostat) many receiving hook -ups, radio and audio 35c. sity. frequency amplification, broadcast and ALDEN MFG. CO. But I suppose you want to know what Dept. H. Springfield ,Mass. commercial transmitters and receivers, he did with all that money, and how he wave meters, super -regeneration, codes, license rules. Many other features. spent it, or what did he buy first. is he and A practical book. Written and edited by ex- Well, all that I know that perienced engineers, in plain language. Some- Joe - yes, he forced half of the thing useful on every one of its 514 pages. The on his -have not authority that covers every phase of radio, all $10,000.00 partner under one cover in one book for one dollar. Don't been seen much lately outside of the spend another cent for parts, turn a dial or touch laboratory which they added to the a tool until you have mailed $1 for this I. C. S. Radio Handbook. shack, but odd shaped boxes are arriving there quite frequently, and none of the Send $1 at once and get this 514 -page boxes look as if they contained B bat- I.C.S. Radio Handbook-the biggest value in they are on the radio to -day. Money back if not satisfied. At dealers, or postpaid teries. It may be that Durham & Co.. 1936 Market St.. Phila. of a genuine television machine, as TEAR OUT HERE 1 trail - - - - on the air INTERNATIONAL CORRESPONDENCE SCHOOLS when I last talked to Denny - Box 8260 -B, Scranton, Penna. Ask Your Dealer For a the modulation on his new set was aw- I enclose One Dollar. Please send me -post- MONTROSE reference paid -the 514 -page I. C. S. Radio Handbook. VERNIER ful-he made some indistinct It is understood that if I am not entirely satisfied CONDENSER I may return this book within five days and you The condenser with genuine Bake- to "seeing things nobody else can see." will refund my money. lite end pieces. Has positive contact between the vernier plate and main Of course it may be as you perhaps shaft. Will get the results where Name others fail, guaranteed to give entire suspect,-that- satisfaction. But, anyhow, that's none of our Address MONTROSE MFG. CO. 1333 Fulton St. Brooklyn, N. Y. business.

60 Tell them that you saw it in RADIO

www.americanradiohistory.com It Pays to Sell the Genuine!

For three years we have consist- ently advertised the advantages of quality binding posts with tops which don't come off. We have been pioneers in the development and sale of well designed and beautifully finished posts which were scientifically made, conveniently packaged and sold at a reasonable price. We have spent a considerable sum of money in telling the world about EBY quality and service. This consistent policy has made it new possible for us to lift binding posts out of the ruck of price competi- tion and has given you an opportunity to sell EBY posts profitably as quality merchandise which does Variable Capacity not deteriorate or go "out of style." The public recognizes the superior workmanship and materials which go into EBY Posts. Unit built by EBY HAS SHOWN THE WAY TO BETTER BINDING POST BUSINESS REMLER Imitations and coun- For Use in Any Circuit terfeits are usually Designed Not merely New -but so improved in design and construction that competing equipment be- short lived. It al- comes obsolete. ways pays to sell the Replace your old condenser with the New 1925 Remler Unit - and notice the genuine and get the improvement. These features are the answer : Minimum Dielectric Loss-Twin Rotors with no full benefit and ad- Stator Plates-Close Tuning aided by insulation of both sets of plates- Complete vantage of a well- Shielding- Lowest Minimum or capacity insuring unequalled tuning range - established name. Maximum to Minimum Ratio L65:1. No wonder this Remler Unit increases your rango and selectivity l Rotation of 360° gives exceptional tuning on short wave lengths-Vernier Tuning over entire capacity through no- back-lash Bakelite Gears-- Bearings 11/2 in. long eliminate ad- ENSIGN ENSIGN justments- Gearing meshes to permit mounting in gangs of two or more 90° limit Rotor Sections allows pigtail connections throughout. plain INSIST ON Gen- engraved of uine EBY Posts. A PERMANENT RECORD of Dial Settings is easily kept by writing call letters or wave lengths on the renewable paper charts. Molded Bakelite knob screws over four inch dial. No. 630-Remler Capacity Unit; Minimum .000003, Maximum .00035, Complete with dial $5.00 No. 631 -Remler Capacity Unit, Minimum .000003, Maximum .0005, Complete with Dial $5.00 Dial Stop and Indicator are included, also drilling template. H. H. EBY. Mfg. Co. Phila., Pa. Leading Radio Dealers throughout the United States are now ready to show you this Remler Quality Unit. REMLER RADIO MFG. COMPANY Home Office-182 Second Street, San Francisco Branch -Chicago Branch -New York Maké Money as a

Write for complete illustrated FREE Catalog of RADIO "B" BATTERIES PARAGON Reg. U. S. Pat. Off. AN RADIO PRODUCTS Demonstrator Adams- Morgan Co., 2 Alvin PL, N. Big Opportunity now to everyone who knows EVEREADY Upper Montclair, J. how to set up and operate a radio set -also to PRODUCT Pacific Coast Representative-Paul Sutcliffe, Rm. 400, San Fernando Bldg., Los Angeles take orders on a price and term basis more At Standard Prices favorable than regular dealers can offer. Your chance to get into the Radio business. Own a 43V. Batteries, tapped set or not, as you choose. Give all or part time 221/2V. Batteries, Navy Type Type to this work. 222V. Batteries, Commercial Beat These Wet "B" Batteries Latter two types especially adapted to Cunningham and Radiotron Tubes. Rabat Junior (12 cells 24 volts) capacity Write at Once Postage Prepaid Anywhere in U. S. 800 mil -amps, only, $3.96; Rabat Senior (2800 Give us this information: Age; Business; Do mil -amps), $9.60. Prices F.O.B. Cleveland, you own a Radio Set ?; What k ind ?; How much Ohio. If your dealer cannot supply you send time do you want to spend in this work? ETS -HOKIN & GALVIN direct. Wireless Engineers The Radio Rabat Company Marshall Radio Products, Inc. 10 Mission Street San Francisco 814 Bangor Bldg. Cleveland, Ohio Marshall Blvd.& 19th St.,Dept 99-36Chicago , Ill.

Tell them that you saw it in RADIO 61

www.americanradiohistory.com IMPROVED REINARTZ Continued from page 18 The NEW Heath the secondary when tuning long waves. This additional capacity makes it possible to cover a larger band of wavelengths NON- DIELECTRIC Condensers with a given coil. A 23 or 43 plate condenser should be used. OLD fashioned dielectric end plates (insulating When using the external coils, the material) which waste condenser efficiency primary and secondary switches are set so as to disconnect the short wave coils just as leaky piston rings waste gasoline, completely and connect the antenna, plate conden- discarded in the new HEATH CONDENSERS. ser, and grid with the binding posts A Grounded end plates of aluminum entirely does and C. As much of the regular plate away with the old difficulties of dielectric loss and coil as necessary to secure good regenera- warping of plates. No shielding necessary. Min- tion or oscillation should be used. Al- though the plate coil is not in inductive imum Loss, all metal, except for the small pieces relation to the external coils, its use of hard rubber in the end plates which separate the sometimes helps to make the set oscillate rotor from the stator plates. Therefore extra- freely. ordinarily rigid. A few notes on tuning music should not be amiss. The secondary and plate Permanently FLAT Plates Micrometer Geared Vernier condensers should be varied simultane- The well -known Heath process of Ordinary adjustments reduced by ously, keeping the plate condenser in stamping and tempering plates rotor separate geared adjustment to hair's such a position that the tube is just over -makes the new HEATH an in- breadth distinction. The most highly strument of lasting accuracy. perfected vernier so far developed. the "edge" into the oscillating state. When the . desired carrier wave is located, the capacity of the plate condenser HEATH SOCKETS is decreased until the tube stops oscil- With the Exclusive Shock Absorber Feature lating, and then both condensers are Cushioning device entirely eliminates vibration. carefully readjusted through a few de- Bakelite base into which re- inforced phosper grees. In this way the maximum bronze, self cleaning contacts are securely em- bedded. Binding posts are slotted hexagon audibility can be obtained without al- nuts. HEATH Standards of material and lowing the set to oscillate more than workmanship. a second or two when the carrier wave is Price 75c Each first located. Obviously, this method òf tuning reduces the QRM from receiver radiation to a. minimum. High power /II IIIIIII!ppr,' , HEATH ,; -72---,1 BAKELITE DIAL broadcasting stations within a radius of several hundred miles can be tuned in

i Specially designed easy grip -knob, beau- without allowing the set to oscillate at tifully proportioned, highly polished and all after they have once been located on clearly incised. Brass bushing centered the secondary condenser dial. by precision machinery to positive, accuracy for perfect balance. Made in 2- inch, 3 -inch and 4 -inch diameters. A typical HEATH product. Write today for Literature The Heath Radio & Electric Mfg. Co. BATTERY 208 First Street, Newark, N. J. F1'1- Charges 120 Volts of "B" Battery IN SERIES _, 1-1-1-1131 ND Another Great Invention by an r7fle raffic C_ Up to 120 Volts "B" battery in series, 6 Volt Radio Amateur Radio Engineer! "A," and automobile batteries can be economically It is now possible for every home to have a ea, of the Jilt. charged with the F.-F. Battery Charger. Simple and Egg"" Super eight tube set at a cost not greater ar. Add a Ferbend Wave Trap durable. No costly bulbs used. There are many other set. Or a five to your set and olice" our f:1:4 than a common radio tube reception. Regulate the Traf- interesting features you should know. coast to coast receiver complbte for $150.00. -'- Rd Guaranteed to tune out any I In- interfering station. Sent post - The public is invited, dealers included. paid on receipt of $5.50, or PRICES: Typo AB, $21.00; Type 6 for "A" or Auto quiries promptly answered'. C. O. D. plus postage. Senrf for free booklet. Batteries, $16.50; each slightly higher west of the THE STANLEY RADIO COMPANY Ferbend Electric Co. 2947 Lorain Avenue Cleveland, Ohio 17 E. South Water St.. Chicago Rockies.

THE PROGRESSIVE DEALERS FRANCE Everywhere MFG. CO. buy RADIO SUPPLIES from When better crystals can be 10323 BEREA RD. made wo sill make them. Cleveland, Ohio dealer ahoui CLARK & TILSON, Inc. SeeJ your 75 FREMONT ST. B- METALS. 554 -A Seventh Ave., New York City San Francisco B -Metal Refining Co. the nationally known house. Send for price 53 FOURTH ST. 12th floor 525 Woodward Ave. list and discount sheet. Wholesale radio supplies Portland, Ore. Detroit. M eh of national reputation since 1921.

'fell them that you saw it in RADIO

www.americanradiohistory.com The Last Word The Best Word In Condensers The

RO U D FO P 01 TRADE MARK Nothing like them on the market for accurate logging of stations! Group plate adjustment and finer vernier plate tuning are accomplished with one knob. Exact RAD I O \REPR DUCTI N readings show on two distinctly separate scales. Once you find a station, you can always "tune in" in the future. Losses Cannot Be Measured! Stator plates are mounted on two rods instead of the customary three -this cuts inefficient capacities and losses to a negligible quantity. The vernier on the Proudfoot sp;t1 8r One -Knob Condenser turns a full 360 °. Three spring wiping contracts insure positive connection. This eliminates the inefficient and easily broken pigtail. For best results, install a Proudfoot today! 13 plate (M. F. C. 000251 -$3.75; 25 plate (M. F. C. .0005)- $4.50; 43 plate (M. F. C. .000-$5.75. Accept no substitute if you want real results. If your dealer cannot supply you, write us. LAS floods t e CRUVER MANUFACTURING CO. CA 2456 W. Jackson Blvd. Chicago. Ill. rom with the be t that's in your s t. THE rite for the int r- POLLARD sting booklet ou LOOP ought to read before buying any spe ker.

ultiple Electric Product Co., Inc. 36 Spring St., Newark, N ., Dept. F New York, Boston, Philad phia, Baltimore, Pittsburgh, Detroit, C.I icago, St. Louis, Denver, 550 Howard ,Street, San Francisco.

Marconi Wireless egraph co. of Canada. Ltd. Dept. E Sole C *dim Distributors /i

Distance and Clarity of Reception Elimination of Interference Convenience in Transportation Operates on all Broadcasting Wave Lengths Braided Pure Copper Wire Gives Maximum Efficiency With Super Heterodyne -Reflex and Radio Frequency Amplification Some POLLARD Points Solidly constructed brass hinge with slip joint held in place by automatic latch to insure proper tension of wire when in use and relieve strain when folding for transportation or setting up. Wires pass through hard rubber-no contact with the wood; consequently perfect insulation and no current losses. Double spiral winding insures maximum efficiency and directional qualities. Frame and base satin finished mahogany. All metal A alight of the parts heavily nickel plated. exclusiv Atlas ha), Atlas unit, with at- mon er (Pat. ap- Price $10.00 tachment couplings ed for) -and your Retail to fit all standard speaker is harmo- dSold to the trade through recognized jobbers phonographs. nizedwith the broad- Dealers write for circular and terms, and if your jobber cast you are hearing can not supply you, we will serve you direct. and the set you are Radio Fans -If you want the best loop you ever saw and using. It gives you your dealer is not sufficiently wide awake to supply you, radio -as you ought send us your order with check or money order and we will to hear it. mail direct, charges prepaid, to any point in the U. S. POLLARD BROS. New type Atlas with the strikingly beau- 4038 N. Tripp Ave. Chicago, Ill. tiful bronze- brown ripple -finish goose- neck horn. Tell them that you saw it in RADIO 63

www.americanradiohistory.com STORAGE BATTERIES Continued from page 24 them, apply a bit of vaseline on the surface. Do not get vaseline on the point of contact between wires and terminals, Look at as vaseline is an insulator and may cause trouble. that If your charger is one which has the battery leads marked, be sure to place the positive lead on the positive terminal Finish! and the negative lead on the negative terminal. This is to insure that the current passes through the battery in the proper way. In some chargers, especially those of the vibrator type, it makes no difference which way connection is made. Follow the instructions with the charger and you will not go wrong. SUPER -HETERODYNE ADJUSTMENT Continued from page 3o secondary) and oscillator condensers are varied, the resonance point may be determined. The meter gives a distinct dip as resonance is passed through, which may be easily recognized after a little practice. The relative dip of the meter will also indicate, more or less, the And the High .Gloss is Everlasting strength of oscillations at that particular setting. .A small change generally A beautiful black, high gloss finish is but shows weák oscillations. With a little one of the superior features Spaulding observation, and general knowledge of Bakelite - Duresto panels can offer you. the tubes under varying conditions, it Bakelite -Duresto panels drill and engrave should not be difficult to correct and ad- easily without chipping. Will not warp, just the faults that usually occur. shrink, or split. Highest in dielectric As a summary the following is given : strength. The best that money can buy. No plate current Insist on Bakelite -Duresto. Your dealer (1) Defective tubes. will cut and drill it for you. (2) Open plate circuit - (a) Poor tube contact. Write for descriptive circular. (b) Opened transformer. MANUFACTURERS SPAULDING FIBRE COMPANY, INC. Dept. 7 (c) Defective wiring. Manufacturers who desire Tonawanda, New York SALES OFFICES -WAREHOUSES: Abnormal plate current - to build quality into their products and who insist on New York, Chicago, Philadelphia, Boston. (1) Positive potential on grid - speed and economy in their (a) C battery polarity re- plants should write to Dept. versed. 7 at our Tonawanda Office (b) Detector grid leak too for complete information on Spauld i ngBakelite- Duresto. low. BAKELITE-DURESTO Low plate current - Panels - Sheets -Tubes & Rods (1) Poor contacts. (2) C battery too high -- follow instructions. See note. (3) B battery weak or filament

1 ow. NOTE. -With correct C battery connections the plate current is very low, as compared to when it is not used. Test this out for yourself. A buzzing sound -loud and persistent At roek bottom prices you set the efficiency of eats an open grid circuit. costing' three times ea much. Users tell us that -shows ULTIMATE IN RADIO RECEPTION Mimeo Radio frequency receivers pick up stations from THE coast to coast Operate either on dry cells or storage battery. Solid mahogany cabinets -anent "orkmanahip throughout. Order direct or send for bulletin Remember that under the present regu- Two tube outfit . $29.50 Four tube outfit. .. $54.50 lations, amateurs are entirely forbidden DEALERS AGENTS -write for proposition quickly-it's a winner. to transmit between 8 and 10:30 p.m., SUPER -HETERODYNE THE 'MIDWEST RADIO COMPANY which is the result of a proposal by 814 Main Street Cincinnati, Ohio Reprints from "RADIO" them for the benefit of the broadcast By G. M. Best listener (or BCL). How many of the Sent to any address for 25 cents. latter would be willing to voluntarily Pacific Radio Pub. Co. 6 MONTHS FOR $1 00 agree, for the benefit of anyone, to keep Pacific Building, San Francisco, Cal. "RADIO" - San Francisco off the air for two and a half hours during the best part of the whole day ?

64 Tell them that you saw it in RADIO

www.americanradiohistory.com NAT NAT

Weston Electrical Instrument Co., 156 Weston Ave., Newark, N. J. Branch Offices in all Principal Cities ) Performance El tetr;cat Indicating Instrument plus Beauty Authorities %vI_:slrON. Choose your panel for its insulating value eI888 as well as for its appearance. STANDARD - The World Over MAHOGANITE JACK Radion Panels CARTER SWITCHES give you both the supreme insulation and the beauty of polished mahogany. For Mahoganite is not a surface finish but a material which extends from one side of the RADION Panel to the other. $1.00 $1.30 21 Stock Sizes Mahoganite and Black $1.15 $1.60 6x7 7x10 7x24 9x14 for a re- The "On and Off" feature shows 10x12 More and more the demand 6x101/Z 7x12 7x26 liable switch, without sliding contacts clearly at all times the exact position 6x14 7x14 7x30 12x14 which wear and make poor contact has of the switch. 6x21 7x18 7x48 12x21 been filled by the Carter Jack Switch. The contact is made by pure silver 7x9 7x21 8x26 14x18 hole to contacts which do not corrode and Simple to install, only one con- 20x24 drill, mounts like a Jack. cause trouble. A positive sure tact at all times. Look for this stamp For continued satisfaction always insist on genuine Carter products. on every genuine Coast Distributors: Atlantic- Pacific Agencies Corp., EL5. RADION PANEL. 204 Rialto Bldg., San Francisco. RADÌONpTs Beware of substitutes PUBBEREB.NY. In Canada -Carter Radio Co., Limited, Toronto HAAB AMERICAN and imitations. Any dealer f ..,,:1\ adio ,;; Ir Write for rrer : illustrated catalog can supply ;:ZO I, :;5'`:::5'rATE:STR_.R EE.'"". RADION JC.H I C'fi G O s..}, Supreme Insulation 9he MAKE MONEY -SELL RADIO 5 -PLATE Radio offers the biggest money -making opportunity today. And the Ozarka Plan opens the door to this big oppor- PANELS plan makes it easy and simple for CONDENSERS tunity. This wonderful you to manufacture the beautiful, long distance Ozarka Dials, Sockets, Knobs, Insulators Radio Receiving Set. It will be your Radio, made by you Given Free this Month and sold by you, with a big cash profit as your reward. No experience necessary. You need not have much cash. In return for your subscrip- At ail good Radio shops, All you need is spare time, determination and action. If you're that kind of a chap, the Ozarka Plan will start you tion to "RADIO" for one or write to on a straight line toward a real money- making business of your own. It can be as big and as profitable as you are year. Full price $2.50. AMERICAN HARD RUBBER CO. ambitious to make it. We want good men in every county. Exclusive territory is going fast. Be sure and give us the 11 New York name of your county. Write today for the Ozarka Plan. A "RADIO" Mercer St., wonderfully interesting book of facts, particulars and proofs. It is FREE. Act now. Pacific Building OZARKA, INC. 66 North Peoria St. CHICAGO San Francisco

Tell them that you saw it in RADIO 65

www.americanradiohistory.com OPERATION OF TRANS- MITTING TUBES Continued from page 31 of existence when a 250 watt tube was RADIoTuBEs REPAIRLO purchased. It never seemed to work as it should, never seemed to be as good as the old 50. "In a wilderness of radio tube mail -order One of the reasons is that perhaps the gyps, this is one honest concern -good tubes 50 had 2000 volts on it instead of the normal 1000. The 250 watter does not and a square to everybody. " deal -Volney G. deliver very much more energy to the Mathison. antenna at 2000 volts than does the 50 watter at 2000 volts. Many times the What is the difference between our tube repairs 50 watter actually delivers more energy and the co on, cheap new and repaired tubes into the antenna, at the same plate volt- flooding thrill 4 et? Costly tungsten -oxide fila- REPAIRED TUBES age. ments; all parts electric spot -welded; tubes bom- Cash or C. O. D. Postpaid. If, on the other hand, the normal barded gas -free in high- frequency external induction UV-199 $2.75 voltage to the 250 watt tube is doubled furnaces; fifteen hour endurance test; rigid inspec- j,çY 201 -A 2.75 (to 4000 volts), the antenna ammeter tions; and heavy shipping packages. These tubes U v -200 2.75 might decide to become very active. are loud, clear- toned, and long -lived. They pull 4V11-11 2.75 Right here, however, is the trick-if WD -12 2.75 you exactly normal filament current. They work on Q*09 2.75 trick wish to call it. The filament superheterodyne, neutrodyne, reflex, and all other 4401 -A 2.75 voltage of the 250 watt tube then must circuits. Best of all, they are remarkably uniform. 0-200 2.75 be raised to 14 volts or so. Its normal Absolute satisfaction or your money cheerfully re- 0 -11 & C -12 2.75 is 11 volts, and a great sigh of anxiety funded. Send in those burnt -ont tubes today. will greet this statement of 13 or 14 POWER TUBES volts. 6KA and 6AWT will vouch for Repaired and guaranteed this statement, I am sure. We make no pretense of competing with cut to stand up on 550 volts. price bootleg and repaired tubes. Apparently the 250 watt tube is the UV -202 $4.75 sturdiest of all the transmitting tubes. Cash or C. O. D. Postpaid. Apparently it can be overloaded with S. P. HANKINS & CO. We are Pacific distributors greater safety than the others, but unless of Dutch Radio Valves. the "spare" is handy 4000 volts 1411 Castro Street Oakland, should California Dealers invited to write. be considered as the extreme. One bad custom exists among transmitting amateurs, that of putting the tube behind the panel, or that of screw- ing the socket close to the table. No free circulation is possible -the air gets heated and stays about the tube. If, on the other hand, the tube is mounted on The Signola a lattice work rack, with nothing under, over or very close to the sides, a clean "The Radio Table Supreme" sweep of air can leave the floor, pass the tube and go to the ceiling. No fan will Top hinged in middle. Ample room be needed, nor is it desirable as it causes behind for set when table top is whirring noises, and the blast of air opened. "B" Batteries, accessories, might open up the seal enough to soften tools, etc., in large space at left. the tube. On actual test, the plates Recessed cabinet for "A" Batteries were cooler in a rack of this sort even and loud speaker horn gives ample when a 25% greater milliampere input leg room. Built in loud speaker (at the same voltage) was given the horn (loud speaker unit extra). tube. This is only one of the methods Mahogany finish, $30.00. for making the "one" tube work. Size, 30 in. high, 36 in. wide, 20 in. Every man who has a tube set, or who deep. contemplates building one, should spend as much money on the filter system as on tubes. The proportion holds true THE ARISTOCRAT for the 5, 50 and 250. In this way, maxi- "The Radio Table De Luxe." Everything out of sight when not in use. An mum output may be secured with the,, elegant piece of furniture for any home. Built in loud speaker (unit extra), ample minimum of interference locally. This space for super heterodynes and neutrodynes and all other sets. Also space for "B" is really very important, and, in addi- "A" Batteries and battery charger, etc. Size over all, 42 in. high, 36 in. wide, and tion, filtered is 16 in. deep. Write for illustrated folder giving full particulars. $55.00. the note louder at a distance of 1500 miles or more. The un- Factory and General Offices: filtered types of notes may be louder 1913 Broadway, locally and within a few hundred miles, Menominee, Mich. but, at a distance, the purer the better. Los Angeles Chicago Minneap olis New York San Francisco Anyone who is not willing to incur this Boston Philadelphia Montreal Pittsburgh St. Louis expenditure should content himself with Seattle Toronto Winnipeg Havana, Cuba the next lower size of tube. The com- You'll find our local address in your Telephone Directory. plete installation is the thing ; it gives best satisfaction and best results.

it RADIO 66 Tell them that you saw in

www.americanradiohistory.com Federal's Finest - --the Wonderful "Fifty -Nine USERS enthusiastically proclaim the Federal striving. It gives all the beauty of Federal Tone, "Fifty- Nine" as "Federal's Finest." The Selectivity and Distance Range, plus a simplicity "Fifty- Nine" represents the accomplishment of of operation that opens the real thrills of radio an ideal after over a quarter century's patient to novice and professional alike. FEDERAL TELEPHONE AND TELEGRAPH Look for this sign COMPANY Priced at f York Buffalo, New $177 1öeraL 1 With headphones stakt.,,, RADIO Products For loop reception (No. 61) Boston New York Philadelphia Pittsburgh extra Chicago San Francisco Bridgehurg, Canada StandardRADIO Products $46 t.

We Feature the Followin g Equipment It is Nationally Known -Has Reputation FADA NEUTRODYNE KITS $25.00. Parts for all circuits. Kilbourne -Clark WAVE TRAPS $8.50 COMPLETE SETS COMPLETE LOUD SPEAKERS INSTALLATIONS $120 Atlas Loud $25 Fada 120 We specialize in the installation Speakers Atwater Kent $104 of complete equipment. Get R3, Model D $35 our prices, they are reasonable. $130 Magnavox M4 $25 Radyne The Warner Guarantee goes Grebe, C.R. 12 $175 with it. Magnavox R2 $50 Our Line of Parts Includes Every Well Known Make Remember---Our Mail Order Service is Rapid and Reliable

THREE THREE STORES STORES 350 Market Street 428 Market Street San Francisco San Francisco Oakland- Twenty- second and Telegraph Avenue

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www.americanradiohistory.com TRANSFORMER IMPEDANCE Continued from page 19 Your For transformers used in the last or Radio Knowledge Worth power stage of an amplifier, there is an added advantage in keeping the second- 62500 to $10,000 Yearly ary impedance down to a moderate value. This results from the fact that, Free Book Below Tells All About It when the, grid of a vacuum tube becomes slightly positive with respect to the negative end of the filament, as is Many amateurs do not realize the big Radio Headquarters Will Help You opportunities likely to occur in the last stage, a small , awaiting them in the corn- mercial field. Thousands of men and boys The knowledge you have now of Radio I11 operating amateur stations have never con- operation and maintenance makes it easy for 111'! 1111111113111111111113I11 i ll8 ; il ll É 1N1ü 8 ii"RI lOglor 1 i' ñ sidered that they can earn . amazingly big you to train yourself and obtain a wonderful . ,. ,fidau+W=+WwwtlalWu!I. _ 0 Alit salaries doing the same easy, interesting work. position. You can work up to positions saianlni0lYdlNflll»klbrit!l0i#!1 B

: paying as high as $10,000 a year. If you are ° no ` 0 Radio is a gigantic, six- billion-dollar- l: '!:` 1NÚomgIlüllljimui¡l r,{1( IIfYL.Nllatlinlnl1 NItBNIPitú Í attracted by the ad- ...... industry -and growing bigger every 0!¡.1 , u uuwYWU4UruMpWtlUllllpltaf¿. r. {: P^' l Ï'`. ;, flfliipgg : .. . , : r : ' ; i!!p venture and excite- ! ; f day! t F Hundreds of commercial stations 1 i I lll' I"::8liillilll II i ment of travel, Ra- ,, are in operation . dio offers you a ' t today; thousands li i r: glorious opportuni- : more are being i: ii IN r (j ì see lflp.11lIIS {'ïil ;3 i erected. Nearly ty to the world IÌ pi plN with all expenses ix : ili i'.ui,',iii ;la l{O} LLi itlii4i3 =iíia ul every vessel on the Variation of Amplification with Frequencyl seas is a floating paid and a fine sal- radio station. Hun- ary besides, or you grid current flows, increasing rapidly dreds of manufac- can stay at home and take one of in magnitude as the grid becomes more turers, thousands of the fine positions all around you. positive. If the secondary of the trans - stores, millions of America's Radio Headquarters, former had zero impedance, this current people are interested in this great, new, the National Radio Institute, has devised an would cause no distortion, but, for a marvelous industry! amazing new plan that will complete your high 'secondary impedance, this current Radio education irb spare time at home, and cannot flow rapidly back to the filament, enable you to qualify for a Government Com- and hence produces a partial neutraliza- Trained Men Needed Now merical operator's cense so you Avin take your tion of the impressed positive wave of place in Ra profession iryhe shortest voltage with resulting distortion. Do you realize what this worldwide expan- possiblti ie. THE balance of this article describes the sion means to you? Many land radio interests One 6t the f ures of this remarkable methods and equations employed in se- employ a force of a thousand or more Radio course, which is Rroved by, the Govern- curing these results. The complete cir- men. Every vessel needs from one to three ment, is that you. are furnished free with four cuit of the bridge is shown in Fig. 1. The wonderful inlltruruendt for practical work at operators. Schools, stores, factories, news- impedance bridge network, consisting of home. Among them as the wonderful Natro- branches A and B, R. and C. and the trans- papers and cities need operators, demon- meter which quickly 'kelps you acquire expert former under test, was placed in the plate strators, salesmen, instructors, technicians, speed and accuracy in sending and receiving circuit of the first vacuum tube so that the designers, inventors, engineers. Everywhere code. plate current would pass through the trans- you turn you see the tremendous demand for In addition to this n tionally known Radio former windings. The presence of the vari- experts are your instructors. They correct more trained certified Radiotricians. able standard capacity C. as shown, and the papers, give you the advice you seek, 2 mfd. insulating condenser in series with the hourelp you in every way with their wide Continued on page yo Here is your greatest opportunity for for- experience to become a ccessful certified tune and success. Take advantage of it. Radiotrician.

Radio needs YOU NOW 1 Get into this fas- cinating profession. The field is uncrowded. Jobs are literally going begging for competent Get 'his New, Free Book trained men. The pay is big, and the work We have prepared a new handsomely illus- fascinatingly easy. trated book for free distribution to those who are interested in learning how to make big money in radio. It tells you how you can prepare quickly in your Pay Increases Over $100 a Month spare time to become an I am averaging anywhere from $75 to $150 and Innovations that a month more than I was making before expert radiotrician, enrolling with you. I would not consider also explains all about Set New Standards of $10,000 too much for the course. (signed) our free employment A. N. Long, 121 No. Main St., Greens- service. Mail coupon Condenser Efficiency burg, Pa. today for your free The efforts constantly directed to keep copy. National Radio U. S. Tool Condensers the leader have. re- Doubles Salary Institute, Radio Head- sulted in these remarkable new features: I can very easily make double the amount quarters, Dept. 10JA, One Piece Stator Hexagon Shaft -elim- of money now than before I enrolled with Washington, D. C. 1nating fanning of rotor blades. you. Your course has benefited me ap- Three Mounting Lugs and Pigtail Con- proximately $3,000 over and above what I would have earned had I not taken it. nection. minus, from in- (Signed) T. Winder, 731 Bedford Ave., National Radio Institute, ,i Guaranteed 3 %, plus or Grand Junction, Colo. 1 Radio Headquarters, Dept. ,10.1A, dicated capacity. i Washington, D. C. I Ask your dealer to show you these new Please send me your fr4e book telling how I can become types: Nos. 3 and 4, celeron end plates. From $15.00 to $80.00 a Week a Certified Radiotrician in my spare time at home with Nos. 5 and 6, low loss-metal end plates. I Before I enrolled with you I was making II details about the positions open to me in Radio and your $15 a week on a farm. Now, I earn from short. time offer. 100% GUARANTEED a year and the work is a Ispecial $2,080 to $4,420 Ì FOR LITERATURE hundred times easier than before. Since IName Age WRITE graduating a little over a year ago, I have earned almost $4,000 and I believe the I course will be worth at least $1,000,000 to IAddress U. S. TOOL CO., Inc. me. (Signed) George A. Adams, Route 1, I N. J. Box 10, Tamaqua, Pa. 1 City State 114 Mechanic St. Newark, Mfrs. of special tools, dies, jigs, automatic 1.11111M MR/MCIMEMLI/M1101 machinery and sub presses. RADIO 68 'fell them that you saw it in

www.americanradiohistory.com STANDARD of EXCELLENCE for audio amplification 4tiiirlWifld Made in two types: AmerTran AF -6 (Turn ratio 5) for use in the first stage. Success/ Amer -Fran AF -7 (Turn ratio 3%2) the companion trans- AMERICAN former for use in further stages of amplification where AF -6 is used in the first stage. BRAND CONDENSERS

NEPJRÁNRKREUSPAT.FKAN Improve your set Price, either type, $7 with an AmerTran at your dealer's Send for booklet containing much helpful transformer information AMERICAN TRANSFORMER COMPANY Designers and builders of radio transformers For over 23 years 174 Emmet St., Newark, N. J. Cal. Office, Rialto Bldg., San Francisco

i I,'!V1Ìl0ll!g a!1101!i101111 1111. 11 i1l-.Jll

With BUY TRIMM the for BETTER 10011 REPRODUCTION 'Worm Dritte 23 Plate, oniy$5 °O Even though you pay more money for a loud speaker, you These Condensers are now ready for you. Jobbers will not obtain a better value and dealers everywhere should have them to fill the than the Home Speaker. Its public demand. size, appearance and efficiency American Brand Condensers are made with the ranks with that of speakers highest ratio geared adjustment ever developed on variable condensers. They are without question the costing twice as much. Lowest Loss condensers available today. Their price of ordinary condensers. A wooden base enclosing the speaker unit eliminates is no higher than the price "tinny" tones and guarantees mellow reproduction. Please ask your dealer to show you this condenser- Non -adjustable, factory -regulated diaphragm assures if he can't do so, write us for a descriptive folder maximum satisfaction. and send us your dealer's name. Incomparable tonal quality, with natural clarity and Note to Dealer: If your jobber superior volume is characteristic of Trimm Quality can't supply you, write us. Reproducers. They are sold at all good dealers, or write direct, giving your dealer's name. AMERICAN BRAND CORPORATION 8 West Park Street, Newark, N. J. Trimm Radio Mfg. Company FACTORY, PHILADELPHIA 24 So. Clinton St. Dept. E Chicago, III.

Tell them that you saw it in RADIO (í()

www.americanradiohistory.com Continued from page 68 was connected by a transformer receivers, prevents any direct current from to the grid flowing except in circuit of the first tube, and the secondary of the branch containing the the transformer transformer and the arm B. under test was connected to the grid circuit of a second In practice, 14 and B were equal tube to simulate non- induc- the operating conditions tive resistances of 6000 ohms each and the of a regular two - re- stage amplifier. Means was provided sistance B therefore caused some reduction in for the plate current inserting a grid leak of 0.5 megohms in this through the trans- circuit for reasons already former. This was compensated as follows: explained. A With the normal plate milliammeter was provided in the plate cir- and grid voltages ap- cuit of the first plied to the first tube tube, both for reading the and a sample trans- amount of direct former connected in the current flowing through the circuit, the switch S primary of the transformer was closed. This allowed the normal plate under test and to prevent overloading of the first tube current to flow and the magnitude was noted by introducing too much current from - on the milliammeter in series with the plate the 1000 battery. The cycle oscillator. switch S was then opened and To measure the plate battery voltage the impedance of the trans- raised until the cur- former, the standard variable rent was restored to the normal resistance Rs value. (1 to 20,000 ohms) non -inductively wound A single frequency current of 1000 cycles Fig. 3. Impedance Bridge and capacity Cs (.001 to 1 mfd.) are

ELIMINATES See the INTERFERENCE HAMMARLUND EXHIBIT INCREASES at the PACIFIC RADIO EXPOSITION RANGE and VOLUME in Space D.

"Just be sure it's a Ilammarlund."

RADIO ci4GINEERING Makes Any Set Better NEW YORK CITY. 1. Lowest Losses (Too small to measure) fir'.; 2. Micrometer Verniers S. Adjustable Cone Bearings t o F 3. Soldered Brass Plates 6. Double Wiping Contacts 4. Rotor grounded to frame 7. Takes any size dial H A M M A RL U N D VERNIER VARIABLE CONDENSER LOW LOSS TUNER UNIT Most Efficient Tuner Available It rile fur New and Interesting Folder Real DX. Reception Extremely Sharp Tuning HAMMARLUND MFG. CO., 144 -146 West 18th Street, New York TWO TYPES{ AMATEUR- 45 to 225 METERS Pacific Coast Representatives BROADCAST-250 to 550 METERS Atlantic- Pacific Agencies Corp., 204 -212 Rialto Building, San Francisco. Special Types for Very Short Waves Price $10 each Write for Information A. C. LOPEZ & CO. Sole Distributors 334 FIFTH AVENUE NEW YORK CITY "A THING OF BEAUTY" THE "RF22"

^41£0N

Transformers in your circuit provide positive assurance of clearer reception, greater volume and a noticeable absence of howling and distortion. A "Five- Tuber" That Acknowledges No Peer Transformers Write us for bearing the Jefferson trade mark can be relied upon to amplify the weakest broad- Pamphlet and Testimonials casting, producing perfect tone quality. There's a Jefferson Transformer for every circuit Write for amplification data and interest- HALLOCK & WATSON RADIO SERVICE ing descriptive literature. 192 Park Street "KGG" Portland, Oregon Jefferson Electric Mfg. Co. WESTERN DEALERS - MAY WE QUOTE YOU? 424 South Green Street - CLlcago

70 Tell them that you saw it in RADIO

www.americanradiohistory.com (4) varied until no sound can be heard Each impedance may be written in the RuXs = - XURs in the receivers. It is necessary to set usual form, Z = R + )X, where X is and both the resistance and capacity to the proper its reactance component, whence for the XuXs (5) value silence, and the R RS =AB+ in order to produce case of Fig. 1: settings are then quite sharp. The accuracy Solving the simultaneous equations of the data resulting is plus or minus 5 %, Z1 =i4+j0 (The unknown (4) and (5) , by ordinary algebra, we { except in the case of very large impedances, Z2 =Ru+ jXu quantities) obtain: which may be as much as 8% in error. Hav- ( (The R & X corn- AB RS ing determined RN and Cn,. the resistance and Z3= R8 ± jX e Ru= reactance components of the transformer may ponents of the Rs2 Xs2 be determined from the mathematical rela- Z4 =B +j0 standards) AB ( -Xs) tions in the bridge. Hence, AB =(Ru + jXu) (Rs + Xu - Xs2 Given an impedance bridge having jXs) (2) (6) and (7) will de- four impedances, Z17 Z2, Z3, Z4, ar- Equations Expanding, AB =RuRs + jRuXs + resistance component Ru ranged as shown in Fig. 3, the condition termine the jXuRs XuXs (3) reactance component Xu of the for balance; that is, no sound in the re- - and the since all of the quantities ceivers, is the vector equation Z1Z4 = Equating the real and imaginary parts, transformer, Z2Z3. we have: Continued on page 73

Quality Volume Selectivity All Combined in the New Chelsea Set A SET OF BEAUTY FOR THE HOME It has a loud speaker range of from two to three thousand miles It is extremely selective. It reduces reradiation to a minimum. It gives enormous volume. Its quality is unexcelled. It ie simple to operate. This Radio Battery Has Over Twice The Life" THE Burgess Radio "A" is exclusively a radio battery, designed especially for service on the "A" or filament circuit of dry cell vacuum tubes. In Radio service it has over twice the life of the ordinary No. 6 ignition battery .. costs approximately the same ... has a rapid recovery to high voltage after short periods of rest . .. practically no voltage is lost when not in use. Replace your worn out "A" battery with a Burgess. Compare the service in your own set under any and all conditions. Then let your e*cperience guide you in your future purchase of Radio 'A, "B' and `C,' batteries; there's a Burgess Bat- tery for every radio purpose. "ASK ANY RADIO ENGINEER" Licensed under Armstrong U.S. Patent No. 1113149. Price $75.00 It has that essential pleasing appearance. It is fully guaranteed. BURGESS It requires a small antenna, and, with such, will give results equal to or better than the RADIO BATTERIES average five, six or eight -tube set now on the market. BURGESS BATTERY COMPANY Engineers - DRY BATTERIES - Manufacturers Chelsea offers a full line of parts and sets FLASHLIGHT - RADIO IGNITION - TELEPHONE General Sales Off ic e: Harris Trust B1dg..Chicago SINGLE tube regenerative set $17.00 Laboratories and Works: Madison, Wisconsin Two stage audio amplifier $16.00 Three tube regenerative set $35.00 Four tube tuned radio frequency $75.00 CHELSEA RADIO COMPANY 179 Spruce Street Chelsea, Mass. Western Agents- FREDERIC L. TOMLINSON CO. 447 Pacific Bldg., San Francisco 1113 Wall St., Los Angeles, Cal. 116 13th Ave. North, Seattle, Wash.

Tell them that you saw it in RADIO 71

www.americanradiohistory.com THE GRID LEAK REMLER CONDENSER Continued from page 34 Continued from page 4z directly- coupled circuit is used, however, tings of 20 and 180 degrees, corresponding to wavelengths from as in the tuned -plate circuit 150 to 580 meters using shown in a standard inductance of 50 turns. Panel Fig. 2, the leak should be connected as mounting is facilitated by a template with three holes for mounting screws shown, between the grid side of and one for the con- the 4-in. shaft. Less space is occupied than denser and the filament lead. This con- by the usual type of condenser. The construction nection should also be used when resist- is unusually sturdy and the bakelite gears operate without back -lash. The ance coupling between high frequency gears of two or more units may be meshed for and detector tubes is employed. "gang" mounting with single control. The construction and design eliminates body Grid leak values are elastic and very capacity and minimizes losses so that weak Get Directly little difference in the strength of re- distant stations can be brought in with ease. Pig -tail connections ceived signals will be noticeable in are used. most The straight line wavelength curve and gear standard circuits at any value between vernier gives close tuning on even the short at Them wavelengths. 1 and 4 megohms. It is much better, The unit includes however, to utilize a a special 4 -in. 360- degree Are the contacts in the fairly high grid dial and knob, together with renewable leak paper sockets of your radio set value when weak signals are de- charts for recording dial settings of stations sired, and a low value when strong sig- heard. This condenser is thus unusually well easily accessible for ordinary adapted for nals are being received. neutrodyne and superheterodyne and necessary cleaning? sets. With Na -ald De Luxe Sockets in use you need neither sand -paper or an extra reach to keep contact strips and tube terminals bright and clean. Just rotate the tube three or four times. Instantly the dual - wipe laminated contacts remove corrosion, making a bright perfect connection. The Helical Wound This action is on the Coil side of the tube terminals away from the soldered ends. "It's the contact that counts." The world's exclusive manu- Make your Super -heterodyne set facturer of Helical wound coils free from socket trouble by using announce their new line of Na -ald De Luxe Sockets. Sockets and panel mounts for all Samson tubes. Prices 35c to 75c. Send for catalog. Transformers AUDIO PUSH PULL HW -A2-6 to 1 $5.00 RW -A2 -I -Input ...$5.00 HW -A2 -3 to 1 5.00 EIW -A2 -T- Output.. 5.00 ALDEN MANUFACTURING CO. Dept. H SPRINGFIELD, MASS. i "Air Intermediate Core" Frequency

RADIO HW -R1 -3000 meters $4.50 HW -R1 -5000 meters 4.50 11W -R1 -1000 meters 4.50

Manufactured by Samson Electric Company CANTON, MASS.

REPRESENTATIVES: SAN FRANCISCO PORTLAND A. S. Lindstrom H. A. Killam 111 New Montgomery St. 312 McKay Bldg. LOS ANGELES SEATTLE Lombard J. Smith G. H. Maire 451 East Third St. 95 Connecticut St.

72 Tell them that you saw it in RADIO

www.americanradiohistory.com Continued from page 71 in the right members of these equations Thousands Now Know This are known. The total impedance of the to be the Greatest Radio transformer is then : Value Ever Offered Rue Z = V + Xu2 "P It will be noted that to measure a acific Quintet" PACIFIC Satisfaction positive (inductive) reactance Xu, a Super -Het Kit RANGER Guaranteed negative (capacitative) reactance X. $15.00 Finely finished (45,000 Cycle) SUPERNET merchandise must be used ; hence the use of the capac- KIT built for real ity C. in the bridge. Another Leader Product of the BALOWIN-PACIFIC CO. work. The reactance Ca is: Popular "Pacific" Line 106 A remarkable value, made possible Xa through huge quantity production. =- 2 VEC. Build your own Super- Heterodyne. where "f" is the frequency and C is ex- Rebuild or convert your old set to a modern and advanced type Super - pressed in microfarads. Heterodyne. All other parts required are standard . Hook -up Tested and Listed as Standard by Underwriters' print with complete and simple Laboratories instructions packed with each "Pacific Quintet" kit. Foresight and Advanced Engineer- "Pacific Quintet" Super -Het Kit ing Efficiency now bring the latest Consisting of 1 Pacific "Ranger" No. 30 Oscillator Coupler, 3 Pacific "Ranger" and most popular developments No. 25 Intermediate Frequency Trans- within a price range, to suit the formers and 1 Pacific No. 20 'Ranger" average pocket -book. Filter Transformer. If Your Dealer Cannot Supply You, SENT TO ANY ADDRESS Upon Receipt of $15.00, or by Parcel Post or Express C.O.D. BALDWIN- PACIFIC CO., Pacific Bldg., San Francisco

A noiseless, bulbless battery chargerg for the Pacific Coast The Balkite Battery Charger is today universally accepted as one of the most efficient and trouble - free methods of charging radio batteries. It is entirely noiseless, has no moving parts, vibrators or bulbs, and nothing to adjust, break or get out SUPER- of order. It cannot discharge, short HETERODYNE circuit or damage the battery by SETS overcharging. It needs no attention other than an occasional filling with distilled water. It is unaffected by No. 53 No. 55 temperature and fluctuations in line ¶ The Superheterodyne uses a large number of tubes and their control is very current. It is simple, efficient, and important. unfailing in operation. It can be used ¶ The Jewell No. 55 "A" and "B" Battery Multiple Reading Voltmeter and the No. 53 Ammeter have become standard on good Superheterodynes. while the set is in operation. Its ¶ Leading Radio Dealers carry Jewell Instruments. Ask for our Complete operation does not create disturb- Radio Catalog, No. 15 -A. ances in your set or your neighbor's. Jewell Electrical Instrument Co. Charges the 6 -volt "A" battery at 3 amperes, C. F. Henderson, Eicher & Bratt, from 110- 120 AC, 60 cycle current. Special Call Bldg., San Francisco CHICAGO L. C. Smith Bldg., Seattle, model for 50 cycle. Will also charge "B" bat- Thomas Machinery Co. Kimmel Co., teries of the lead type. If your dealer cannot sup- American Bank Bldg., 25 Years Making Good Instruments' Nixon 167 So. Wall St., Spokane. ply you, sent direct prepaid on receipt of price. Los Angeles. FANSTEEL PRODUCTS COMPANY North Chicago, III. PACIFIC COAST DISTRIBUTORS: San Fran- cisco: A. S. Lindstrom, 111 New Montgomery St. Los Angeles: Lombard I. Smith, 451 E. 3d St. Seattle: George H. Maire, 95 Con- PERITE necticut St. Portland: H. A. Killam, 312 Mc- kay Bldg. :ñe 'SELF-- ADJUSTING " Rheostat

Trice $20 PERFECT ev°ery CI RCU IT East of Rockies Simplifies wiring F. TEE._ $19.50 Eliminates anada $27.50 hand rheostats \RADIALL COMPANY Balkite 320 W. 42nd St., N. Y,

Raflery Charger Write Dept. R -2 From for Free Your Hook-ups Dealer

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www.americanradiohistory.com New Models BRISTOL RADIO RECEIVERS 100 VOLT TYPE Incorporating the Patented Grimes YOUR MONEY BACK IF YOU'RE Inverse Duplex System NOT SATISFIED WITH KIC -O We have thousands of unsolicited letters of Watch recommendation. KIC -O "B" batteries will for further announcements in make good for you, too. Life unlimited. Not harmed by short cir- all leading radio publications. cuiting, over- charg- ing, idleness. Panel Price, With Grimes System Insures Natural Tone Quality switches give single Volts Plain Panels cell variations. Re- 22 $ charge from any 110 - 5.50 Improved Bristol Audiophone Loud Speakers volt A. C. line with -gives greater 32 7.25 $11.75 volume, is more small home rectifier. sensitive and still maintains its round, full Charge lasts 3 to 6 tone and its distinctive freedom from distortion. months in detector 48 9.50 14.00 plate circuit. Ask for Bulletin No. 3017 -R. 68 12.50 17.00 GUARANTEE 100 17.50 22.50

Your money back on any 145 23.50 28.50 Manufactured By KIC -O Battery if not satisfied within 30 days'. Mounted Write for full Rectifier.. $2.50 information Unmounted THE BRISTOL COMPANY on "A" and "B" Batteries. Rectifier. $1.00 Waterbury, Conn. BABY AUDIOPHONE KIMLEY ELECTRIC COMPANY, Inc. With Fibre Horn 2661 MAIN STRFET BUFFALO, N. Y. Pacific Coast Branch Office 332 Rialto Bldg., San Francisco, Cal. Price $12.50 as.c.1), ... Storage "B" Batteries

5 long service, low cost.

BREMER -TULLY LEADS AGAIN With a real Low Loss Tuner The Tuner which gives results heretofore impossible. BEWARE TlIIS is the original B -T product, the first "tuner," improved with new B -T method of inductance winding and New adjustable untuned primary. of Imitations! Low Dielectric Losses Windings are supported with the least possible insulation The UNCLE SAM MASTER TUN- (approved by Bureau of Standards). ING COIL is the original 3- circuit Adjustable Untuned Primary tuner. Demand only the genuine if meets the great problem of the past -that of adapting a tuner to the various types of antennae circuit re- you want VOLUME, quirements and local receiving conditions. DISTANCE, Adjustments permit greater selectivity or increased signal strength as desired. SELECTIVITY. A new support, providing either base or panel mounting. Single hole mounting can be used if desired. A new adjustable lubricated cone bearing. Pigtail connection. Binding Post connections with tinned soldering lugs. F Adaptable for any circuit requiring a tuner. Two types for Broadcasting-200 -565 meters. for short wave work -50-160 meters. Price $5.00 Go to your dealer and examine this remarkable new

'. tuner. "Better Tuning" (now in its 6th edition) tells you why and shows you how-complete instructions and diagrams for progressive construction from Crystal to Reflex and Radio Frequency circuits. Mailed on receipt of ten cents. Not a technical book but a book of Technique. Carl A. Stone Co., 1113 S. Carl A. Cook, 1116 Minor E. J. Koepke, 644 New Call Wall St., Los Angeles, Cal. Ave., Seattle, Wash. Bldg., San Francisco, Cal. BREMER -TULLY MFG. CO., 536 S. Canal Street, Chicago UNCLE SAM TUN NG COIL Verifications from satisfied users prove conclusively such DX Re- ception as Philadelphia to KFAE latestDevelopmenthi (Pullman, Wash.), Ardmore, Pa. to WKAQ (Porto Rico), Trenton, 1RADI® N. J., to KHJ (Los Angeles). 1heNewPfanstiehl And as to selectivity, a committee Non-Oscillating of engineers in Philadelphia clearly heard 49 different stations Principle sign off in 8% hours on the air. Complete Outfits The only licensed all Litz Tuner "REFLEX SPECIAL" Easy Mlon th ly Paym e n ts Only $ 5.50 QUICK CONTACT The season's biggest sensation. Carl Pfanstiehl's improvement over Neutro- 111 all good dealers RECTIFIER dyne, Super Reflex, etc. Positively non - GUARANTEED regenerative. Brings a new degree of musi- Ask your dealer or send self -addressed, cal Quality, selectivity, and simple operation. The Acme Apparatus Co. says "prevent dis- Solid mahogany cabinets. Accessories included. stamped envelope for FREE wiring tortion and howling by using a BROWNLIE Write Today for FREE Trial Offer! diagrams of circuits using this coil. CRYSTAL in REFLEX SETS." Write quick and get our special price offer with 2 week's Order From Your Dealer or Direct FREE Trial, and easy payments. 9, 4 or 6 tube sete. W rite. UNCLE SAM ELECTRIC CO. MARSHALL RADIO PRODUCTS., Inc., Dept. 59 -36 ROLAND BROWNLIE & CO. Marshall Blvd. and 19th Street, Chicago, Ill. 213 E. 6th Street Plainfield, N. J. 24 Saunders Street, Medford, Mass.

74 Tell them that you saw it in RADIO

www.americanradiohistory.com LARGEST SELLING TRANSFORMERS IN THE WORLD

u - AMERicA N For Your Super- Five faultless coupling! Engineers built this condenser!! For two years we have successfully marketed the Sexton Condenser, and it was good. But we were not satisfied, we wanted the best condenser it was possible to make, that could be used in any kind of a set and give the best results. So, five engineers whose combined experience covers all phases of radio work, laid out the HI CO Condenser Housed in beautiful bakelite cases, exactly similar, are these two All- All the features incorporated in this condenser are acknowledged to Americans of characteristic high be right, and best of all includes a new type of vernier control, quality: a sharp -tuned Air -Core Transformer which filters out a 10.000 meter wave, and a Coupler Noiseless Cam Vernier on Stator Plates which enables the oscillator to deliver a remarkably uniform out- This allows the minutest adjustments without the noises of rotor put. plate control. Type R -120 Filter is made in four types: Transformer $6.00 The HICO Type R -130 Short -Wave 11 Plate .00025 cap. $4.50 ea. R. F. Coupler 5.00 17 .00035 66 4.75 " 64 .0005 5.00 " 43 " .001 66 6.00 " All with Cam Vernier. We make only the one type as cost would be the same without vernier and it operates as plain type as well. At all good dealers, or sent on receipt of price THE HARTFORD INSTURMENT CO. 309 Pearl Street Hartford, Conn. Western Agents -FREDERIC L. TOMLINSON CO. 447 Pacific Bldg., San Francisco 1113 Wall St., Los Angeles, Cal. 116 13th Ave. North, Seattle, Wash.

Known and relied upon everywhere for splendid intermediate -frequency amplification, the All- American You Can Also "Long- Wave" gives maximum results at all wave lengths from Charge 4.000 to 20.000 meters. SIMPLEX Lightning "B" Batteries Type R -110 Long -Wave Arresters at Home! Transformer $6.00 Approved Alr Gap type. $1.50 Sealed In fine brown glazed i n APCO "B" Battery Charger is a The new RADIO KEY -BOOK -Just worthy ally to the successful APCO Out -Hook -Ups -Helps -You'll be sur- porcelain. Easily Charger for "A" Batteries. Renews prised! ordered yours, any 24 or 48 volt wet "B" battery in If you haven't installed. hours disconnecting set. send 10 ten -without cents --coin or stamps. No fuse or vacuum. Its noiseless. clean and as easy to hook up as an electric iron. Complete with SIMPLEX RADIO CO. wires ready to use, $10. Write for interesting circular and nearest dealer's RAULAND MFG. CO. (Mfrs.) Philadelphia name. Western APCO MFG. CO. 2654 COYNE ST. CHICAGO Representatives: Virginia Ave., Providence, R. I. Frederic L. Tomlinson Co. Ask PIONEERS IN THE INDUSTRY Seattle San Francisco Your Los Angeles Dealer

Tell them that you saw it in RADIO 75

www.americanradiohistory.com et4 ..u,., for all itcøu(dn't be Charger 7AetsaW done, The Standard bile and Radioautomright obile Autour° 12 volt right 6 or batterieshe cat. 2 volt ` peanut "e, 6 voltvo 1 to 4 "B" radio batteries.£ MERE e o Simple. Cannot nom al. bat- does tery havé to be i have Live dealers Co. watched ElectrictTepcisc o C ValleyBldg San Write for Rialto it is at tam literature

A 5 -TUBE SET Tuned Radio Frequency Clarity RADIO PARTS built of the finest low loss material and in a beautiful genu- Beauty ine solid mahogany cabinet at only sixty dollars. Formerly Volume "MASTER" Line Ask your dealer for a REDESIGNED AND IMPROVED free demonstration. Distance For ACCURACY, EFFICIENCY and Complete catalog glad- APPEARANCE, insist on "K.B." Selectivity ly sent on request. products from your dealer. Ask to see our new type Variable Condensers with important Special New Features. Jobbers and Dealers write for attrac- FRESHMAN tive prices and discounts. K. B. MANUFACTURING CO. Dept. C-No. 222 Eighth St., mASTREVE San Francisco BAKELITE Mouldings, Dies, Custom Work

1 Super -Hetrodynes Worth of Wiring charts $ $5O and hook -ups for only

This valuable book gives you a series of over thirty super - hetrodyne wiring diagrams and hook-ups which would easily cost more than $50 if purchased separately. Not a catalog - but a thoroughly scientific text book with a wealth of data Chas. Freshman Co., Inc., 106 Seventh Ave., New York on every phase of super -hetrodyne equipmedt. Sixty-four pages of worth while information. with more than fifty illustrations. Only 51.00 postpaid. Get it today -at your dealers or use the coupon below. J. T. BOONE RADIO CORPORATION BOONE SUPER -HETRODYNE TRANSFORMER KITS BOONE SUPER FOLDING LOOP AERIALS BOONE SUPER VARIABLE CONDENSERS From your dealer or direct from our factory. 5111111111111111111111 IIIIIIIllll 11111111111111111111111111111111111111111111111111111111111111111111111 68 STATIONS ON CRYSTAL J. T. BOONE RADIO CORP., 3469 E. Jefferson, Detroit, Mich. SIX MONTHS FOR without tubes or batteries. You fellows who Enclosed is áß1 for your text book, -The Super- Hetrodyne." haven't tried my hook -up don't know what Please also send me information on your Super -Hetrodyne Transformer Kits-Folding Loop Aerials -Low Losa ONE DOLLAR you are missing. Write Variable Condensers. "RADIO" San Francisco Leon Lambert Name 542 Volutsia, Wichita, Kansas Address C2

76 Tell them that you saw it in RADIO

www.americanradiohistory.com Jones Multi -Plugs are supplied for panel or bracket mounting. Also (as illustrated belowl with seven 2-foot leads coded A for attaching to binding Receiver set. Acme posts of any Telmaco The Ideal Receiver for all Seasons Telmaco Acme et AMPI-. eti The BIDET Receiver is truly portable. Entirely contained in beautiful traveling case. Tubes, batteries, loop, loud speaker, Complete everything built into $5.00 set. No outside loop, no aerial, no ground ONE PULL - -- required. nu the Jones M (IL TI -PLLY; instantly discon- Size of Case 8' x 10° nects antenna, ground, A and B batteries from x 18 °. Weighs only your set! One push reconnects( Long cable 27 pounds complete. permita placing batteries out of way-in base- Easily Carried. ment, closet or elsewhere. All leads coded. JONES Acme 4 -Tube Reflex Circuit Used MULTI -PLUG securing selectivity, distance and volume Can't be plugged in wrong. Prevents burning with minimum battery consumption. out tubes or shorting batteries. 100% fool- Complete in itself. Easily carried from room to room in proof. Enables anyone to connect your set with safety. Standard on Zenith, workrite and your home or to office, neighbors, etc. Take it along and many other leading sets. Jones Multi -Plugs. have music, entertainment, speeches, news, market reports complete for panel mounting, $4.00; for bracket wherever you happen to be. mounting, $4.50. Binding Post type, $5.00. Carried by all jobbers. If your dealer isn't Instantly ready for use as it is. You can use external antenna supplied, state his name when ordering. Folder free. and ground, loop and loud speaker if desired. 4 tubes (fully Pat. Applied for protected by shock absorber sockets) -equal to 7 tubes, due HOWARD B. JONES to reflexing and use of crystal detector. 614 S. Canal St. Chicago Reasonably riced Write for Free illustrated circular fully PACIFIC COAST DISTRIBUTORS: y describing Telmaco Acme Receiver. San Francisco, Calif., Los Angeles, Calif., Complete Telmaco 64 page catalog containing 20 circuits in blue and A. S. Lindstrom, Lombard J. Smith, describing the best in radio sent postpaid for 10c. 111 New Montgomery St. 451 East Third Street. Quality Radio List fide dealers Seattle, Washington, Portland, Oregon, Dealers igrequest on eir bus ness stationeryna George H. Mayer, H. A. Killim, Exclusively 95 Connecticut Street 312 McKay Building. Established 1918 Radio Division TELEPHONE MAINTENANCE CO. 20 South Wells Street Dept. A Chicago, Illinois

A Pleasant Surprise Awaits the User of the A.C.H. Sharp Turner Dials

Ampitfy the MODERN wad

MODERN "PUSH- PULL" Transformers are the recognized last word in Radio Amplification.

the A.C.H. is different) Here's Why-- - 5. Can be used in any PUSH-PULL- Why circuit now available with any of the s I. 3 in. DIAL ACJt 156 -0 -I Perfectly balanced. standard tubes now on the market. 4in. DIAL 20 ALIL> 215 -to -1 2. Capable of the greatest possible amplification. 6. Made with the greatest care. Will improve any receiving set, making difficult tuning easy 3. Distortion reduced to a minimum. thoroughly tested and fully GUAR- ANTEED. Money Back Guarantee 4. Adds clarity and volume to any set. own specially Prioe3 -inch size.. $2.50 Price 4 -inch size . $5.00 7. Coils are wound on our Regular fitting e,(° shaft and 84....5c each extra Price per matched pair designed winding machines in our y Sold by all good dealers. $12.50 Extra Advantage of the A. C. H. Bulletin FREE on REQUEST. own factory. 1. Can be attached or removed from any instrument. MODERN Long -Wave 30 K. C. Transformers. 2. Rough tuning same as any dial. Each $5.00 3. eye detect MODERN Standard Audio Transformers. Each $5.0J Movement so fine that the cannot MODERN famous one -Tube Reflex Audio but the ear can. Transformers. Each $5.50 4. Automatically locks instrument so no jar can disturb it. FACTORY REPRESENTATIVES 5. Dial grounded reducing the body capacity to a Frederic L. Tomlinson Co. minimum. Los Angeles San Francisco 6. Special dial 2 graduations where ordinarily one. Mail Orders sent Prepaid in U. S. A. The Modern Electric Mfg. Co., Toledo, Ohio A. C. HAYDEN RADIO & RESEARCH CO. BROCKTON, MASS., U. S. A.

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www.americanradiohistory.com +oirde-... Oai .01141.. Announcing Finest Smallest .s Lightest Yet nnounein Made PREMIER the New "CROFOOT" Trade Mark VARIABLE CONDENSER "The Condenser with the Red Stripe" A real achievement in scientific engineering. It has the greatest tuning ratio and the widest and sharpest tuning range for given capacity. ln operating efficiency it is unexcelled; light. compact, and the smallest condenser for capacity -.0005 M. F. Capacity, 3 inches in diameter, weight I I ounces. Get! all the facts about this wonderful new Condenser. Send for Bulletin No. 94. Capacity List Price .0001 M. F. $2.75 .00025 M. F. 3.25 .00035 M. F. 3.50 .0005 M. F. 3.75 Minimum Capacity for .0005 M. F. Condenser is .000007 M. F. Tuning Ratio I to 74. ASK YOUR DEALER FOR CROFOOT FREE: -- Diagrams of the most popular "hook- ups," including Harkness Reflex, Neutrodyne, Super- Heterodyne, Tuned Lefax Radio Frequency, Regenerative, etc. Send for them. PREMIER ELECTRIC COMPANY KADIO HANDBOOK 3813 Ravenswood Ave. Chicago WESTERN SALES OFFICE: Bound Edition. 1612 Maple Ave., Los Angeles

The Special (7th) Edition of the Lefax Radio Handbook is now ready. 60,000 copies of the loose -leaf edition have been sold. The new edition is Unequalled for available in bound form. Clarity of Tone Volume and FOR $2 NOW Long Life

WHAT YOU GET 20I -A When you become an owner of a TYPE Lefax Radio Handbook 3.50 1 Authoritative facts on Radio. A 3 A reference and instruction book that complete book written by Dr. J. H. will help you get better with GUARANTEED Dellinger, Chief of the U. S. Bureau results of Standards' Radio Laboratory, and your set. Bound with a fabrikoid Mr. L. E. Whittemore, of the Inter- Morocco grain binding, attractive and departmental Radio Advisory Com- long wearing. mittee. Pages that are extremely readable and well -illustrated. 2 A complete list of broadcasting sta- KEYSTONE tions, giving the information you want about each one. VACUUM TUBE When you order specify "Bound Edition" The Keystone Vacuum Radio Tube is the result of the very latest research into the principles underlying vacuum tube construction. WHAT'S WRONG WITH CONDENSERS? The Keystone Tube has a larger mutual con- RADIOFAX has just completed, after months of investigation and research, ductance factor which insures greater clarity the testing of over 200 well known condensers. Valuable and useful as well as of tone than the ordinary tube. interesting information has been learned. The results appear in the September issue. The Keystone Tube also has a larger ampli- This is but one of the articles covering new developments and hook -ups and fication factor, which means much louder signal reports of our Research Laboratory that appear every month in RADIOFAX. Send strength than the average tube. Operates in your subscription today per year. equally well for radio or audio frequency -$3.00 amplification. Ask radio supply man, stationer, or bookseller. FULLY GUARANTEED your to give satisfactory service If your dealer does not have Keystone Tubes we will ship prepaid anywhere as many as you LEFAX, Incorporated, Publishers need upon receipt of price. 149 St. Philadelphia, KEYSTONE ELECTRIC & RADIO CO. South 9th Pa. 110 -116 Nassau Street, New York, N. Y. Sonic dealer territory still open e. .t.e... -.141,51P i

78 Tell them that you saw it in RADIO

www.americanradiohistory.com RADIOADS DUoSPIR4L A CLASSIFIED ADVERTISING SECTION READ BY BETTER BUYERS The rate per word is five cents net. Remittance must accompany all advertisements. FOLDING LOOP Include name and address when counting words. ADS FOR THE OCTOBER ISSUE MUST REACH US BY SEPTEMBER FIRST Increases Reduces Selectivity Static MIMS ONDtl) WOIS YOUR NEUT RIGHT? To revitalize un- WANTED -Used 15 dial Omnigraph, American neutralizable Neutrodynes we devised this Kladag Morse Code,- or Dodge Automatic Transmitter. Coast To Coast Circuit. Uses same panel, etc., Must be in good condition. Write description. as Neut, except three less parts. Merely re- F. L. Davis, Martinez, Calif. wire. Success certain. Necessary stabilizer, - ñ 22 feet gold sheathed wire, circuit and complete, simple instructions -$5.00 prepaid. Many have AGENTS wanted to install Radio Sets in your already rebuilt their Neuts -and written wonder- territory. Good money guaranteed. Full time ful testimonials. Thousands will do it. Be or part time. No money required. Ask for full FIRST -have the finest five tube set in your information. Ruf Radio Lab., 1480 Santa Clara neighborhood, revitalize others' Neuts. De- Street, Santa Clara, Calif. scription, etc. -10c. Radio Lists -2c. Stamps Easily accepted. KLADAG LABORATORIES, Kent, EDISON CELLS complete, also paired ele- Price $8.50 Ohio. ments (sample, 10 cents). Henry Chapelle, Portable Woodburn, Ore. MAKE BIG MONEY Patents pending OUT OF RADIO The SOLDERING HINTS. No chain is stronger highest development in a portable aerial. Thousands of People want to buy a good Radio Compact, convenient and self contained. No instrument. than its weakest link and no radio is better than outside aerial or ground They have read that vast improvements its weakest connection. But we wire necessary. Can be have been made and they are ready to buy now if you must admit used anywhere. Brings in distant stations show them the best. that the soldering flux is nine -tenths of the con- with remarkable volume. It is one thing to make a good radio instrument for nection. Jones' Solder -Eze is more than the name implies. It combines the principles of The Duo -Spiral has a swivel base graduated in your own amusement, but why not cash in now on your degrees experience? Let us send you full particulars of the ease in soldering a joint that holds where you for calibration. A convenient handle Ozarka Plan which shows you how to put it, and does not corrode. In bottles 50c. permits adjustment without body capacity Jones' Solder -Eze Company, Dept. A, 105 Tipton effects. It has been adopted as standard equip- "MAKE $120 WEEKLY" Street, Johnson City, Tennessee. ment by 'leading manufacturers. Its handsome selling long -distance Radio sets. The season is on right silver and mahogany now. Let finish harmonizes with the us tell you how to combine the clear signal finest. furniture. The folding feature makes it of the crystal detector with the distance of the vacuum LARGE size Edison elements .05 per pair, easily portable. tube. Write today and don't fail to give the name of prepaid. Wired Elements, your county. spot welded connec- I)uo- Spiral is made by the manufac- tions, nickel wire .07'% per pair prepaid. Arthur turers of OZARKA INCORPORATED Chapelle, Woodburn, Tiny -Turn, the superior 814 Washington Blvd., Chicago Oregon, Radio 7NX. vernier control which makes perfect tuning easy. If your dealer is unable C. W. and RADIO PHONISTS -Our new converters MAGNAVOX M4. List $25. Introductory to supply you with either of these will satisfy your need for a more efficient and durable $21. Radio Central, Dept. P, Abilene, Kansas. standard products, write us direct. direct current plate supply. No armatures to burn out. Output from seven hundred to two thousand volts at .4 amperes. Synchronous Motors, Transformers and GONE ON VACATION, -all my "B" batteries other parts sold separate. Write immediately, Kimley except the Edison; so I'm ordering more Edison Riu»oWns Equipment Mfg. Co.. 290 Winslow Ave., Buffalo, N. Y. elements from Henry Chapelle, Woodburn, Ore. Irc (tc) 1303 First Avenue Maywood, Ill. ULTRADYNE (Super -Heterodyne) for sale. ARC & SPARK SYSTEMS Complete with 8 tubes, Send for Descriptive Circular QRD. loud speaker, batteries, Interesting and Instructive (tc) and RECTIGON charger, $180.00. WILLARD, Pacific Radio School 433 Call Bldg., San Francisco 1950 Hopkins St., Berkeley, Calif. Vacuum Tube Hospital We repair and guarantee them. Agents, Dealers, and Customers Wanted. Radiotube Co., 903 Broad St., Newark, N. J. tc BIG Money and Fast Sales -every owner buys gold initials for his auto. You charge $1.50, make, $1.44. 10 orders daily easy. Samples and information free. World Monogram Co., Dept. 68, Newark, N. J. (SAS) RADIO GENERATORS-500V 100 watt $28.50. Battery Charging Generator $8.50. High Speed Motors. Motor Generator Sets, all sizes. MOTOR SPECIALTIES CO., Crafton, Penna. (tc) ARE YOU PLANNING TO MANUFACTURE RADIO PARTS ? Here is a chance to save a The lot of money. We offer slightly used tool equip- three most powerful ment for 19 standard parts. Write for particulars. WEBSTER ELECTRIC CO., Racine, Wis. circuits combined in FREE DIRECTIONS for constructing home one single receiver built Radio with two thousand mile receiving range. Send self -addressed stamped envelope. THE ARISTOCRAT END 10 cents for booklet Maitland Roach, 2905 Columbia Ave., Philadel- containing phia, Pa. OF AMPLIFIERS S diagram and in- Quality in Radio is No Less Marked structions for building this won- 1500 VOLTS FOR $45 I ! 1 1 ! ! Brand new Than Quality in people. The Re- derful Shamrock -Harkness set. General Electric Dynamotors made for U. S. sistance Coupled Amplifier is a `Naval Air Service, ball bearing. Low tension Quality Product. SHAMROCK MANUFACTURING CO., side 25 volts 31 amps, high tension (rated) 1500 Dept. 54, Market St., Newark, N. J. volts 233 M.A., but will actually deliver nearly DAVEN COMPLETE 500 M.A. without heating. Also with shafts ex- AMPLIFIER KIT tended for driving by an external source, such as 3 -Stage $13 50 an AC motor, etc., for which about 1 HP is 4 -Stage 17.00 needed. Low KITS SHAMROCK tension side as a generator will without sockets and con-

www.americanradiohistory.com -- WEATHER FORECASTS BROAD GOND/ T/ONS N/1RKETREAOPTS NEWS /TE'AlS ,19 ` r' PEEKESG 17AL5/ SONG M5/C

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6 iiharpWl!uning U ôlkn-ßn4çy 1 roduCtS . Selectivity depends upon the combined efficiency of all parts of your radio set. One poor device in your hook -up frequently offsets the effectiveness of the rest of the set. For this reason, only well -known, tested radio parts, such as Allen- Bradley products, should be selected for maximum efficiency and selectivity. This remarkable radio filament rheostat, B lv+a,w utilizing graphite discs, instead of coiled wire, PERFECT FILAMENT CONTROL $1.85 stands supreme for noiseless, stepless control. For All Tubes It is standard equipment on many fine sets. Proclaimed by Crosley, Kennedy, Amrad, Flewelling, and other leading THE PERFECT GRID LEAK Cockaday, radio $1.85 experts, as the perfect grid leak. A range of Vs to 10 Megohms I/4 to 10 megohms assures maximum efficiency for all tubes. A highly -praised adjustable resistor for radio circuits. It is made in three sizes, and pro - THE PERFECT RESISTOR $2.00 vides a marvelously smooth and noiseless vari- No. 10 10,000 to 100,000 ation that assures rapid adjustment to the point of highest efficiency. No. 25 25,000 to 250,000 No. 50 Another Allen -Bradley contribution to radio. 50,000 to 500,000 THE PEPFEC POTENTIOMETER ohms Made in two sizes for all types of radio frequency circuits. No coiled wire to slip or break in operation. A totally -enclosed convenient battery switch for A or B- battery circuits. Requires only $2.00 PERFECT BATTERY SWITCH for 200 ohm one hole in panel for mounting, and is com- $3.00 pletely protected against accidental injury. Saves batteries and tubes. for 400 ohm -131m47,, Allen -Bradley Co. 288 Greenfield Ave.. Milwaukee, Wis. Electric Controlling Apparatus Please send me a complete set of your bulletins of Allen- Bradley radio products. 288 Mil- 60c Greenfield waukee, Name for A or B Ave. Wis. batteries Manufacturers of graphite disc rheostats Address for over twenty years.

80 Tell them that you saw it in RADIO

www.americanradiohistory.com Loud S is Perfected! Human Voice and Music Now Actually Reproduced over Radio The slap -stick assembled loud speaker consisting of a phone unit attached to a horn and absolutely void of any engineering principles has placed radio in contempt. Rather than tolerate its irritating noises mixed with uncanny tones, many still prefer the headsets. A faithful reproduction of the original tones -free from all noises -was necessary before radio could be changed from a braying novelty to a refined medium of entertainment. To reach this goal, it has been conceded by experts that a radical departure in the construction of loud speakers must be made. The Loud Speaker of Tomorrow Must Positively be Built Along acoustical lines, not merely advertised as such. Only as a reproducer, not as a reproducer and a producer. Without a resonance that will shade the original reception into a deep down -in -the -well reproduction. Before trim -0am A clear re- creation of the fundamental tones and their "The loud speaker with a nose." overtones - free from all internal noises -is possible. Such only is the loud -speaker Echo -Tone. Equally adapted to sets using dry or wet A batteries - ECHO -TONE is built upon the principles of catacoustics- no extra power needed. the science of reflected sounds or echoes -because it was dis- covered that the sound waves and air back of the diaphragm Dia. Horn i6 in. needed attention. In other words, the loud speaker needed a Height 24 in. nose, and by giving Echo -Tone a nose -the loud speaker was Weight 534 lb. perfected. Color Silver Tone THE NOSE WHICH Material Aluminum ELIMINATES ALL Durable -Fool- proof. NASAL. METALLIC. AND TIN HORN EFFECTS price $30.00

Throw away your headset! Waiting t. now is wasted time; for that Loud el Speaker of Tomorrow is here Today ! _ h Order immediately and allow the whole family to enjoy in advance the v new improved 1925 model Echo -Tone.

PATENTED WILLIAMS RADIO COMPANY 1438 Washington Boulevard DETROIT, MICHIGAN Western Representatives GLOBE COMMERCIAL CO. - 709 Mission St.., San Francisco

www.americanradiohistory.com "THE CHOICE OF RADIO EXPERTS" Designed for PRECISION

Heavy Brass Plates Soldered to Minimize Resistance Balanced Losses Vernier Gears Promote Extreme Selectivity Capacity 500 MMF Price X500 The outstanding feature of a GEN- soldered, thereby reducing resistance ERAL RADIO condenser is PRE- losses to a minimum. CISION. This method of soldering makes the PRECISION in a variable condenser whole condenser assembly more rugged gives you the sharp tuning and low losses and assures the perfect alignment of which mean greater selectivity, signal plates which keeps capacity values con- strength and range. stant. Balanced ratio gears with accurately machined teeth provide a perfect ver- Type 247 -H 500 .MMF with nier adjustment. vernier $5.00 Heavy brass plates of the rotor and Type 247 -F 500 MMF without stator groups ire correctly spaced and vernier 3.25 For Sale by Good Radio Dealers Everywhere

GENERAL RADIO CO GENERAL RADIO C9 t:bridge.Mass. Mas u.s.A. Write for our New Instructive Folder "Quality Condensers"

SUNSET PfI6SS. SAN FRANCISCO