(Broadcastage's Entertainers N O R'of Ifi ' Contest O

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Announcing Winner of Radio (BroadcastAge's Entertainers N o r'of Ifi ' Contest o

-a >_,.. v. .-..y..., tAl u .ffisimfr 1' Is The 0 'ANNUAL' on your ill Summer List?

IF YOU intend to take a trip this Summer, you're surely going to keep in touch with Radio, either by bringing a set along or building one during the dull afternoons, from parts you can take with you. AND how are you going to build this set or study up on radio for the big season that A Big Section is bound to come in September? Blueprint The answer is simple. All you have to do is to invest for your Dollar! ONE DOLLAR in a RADIO AGE ANNUAL for 1925, the How many blueprints could you buy for a world's most complete and authoritative hookup book, dollar if you started out to buy them, one and take it with you, whether you go to Eagle River or the by one? Very few, you'll admit. Yet in the 0 River of Doubt. RADIO AGE ANNUAL for 1925 you'll find sixteen full pages of blueprints in actual 1925 Let the ANNUAL for be your Radio Companion this color, explaining concisely every important 111 Summer! It will tell you whatever you want to know in simple and complicated hookup developed the radio line -from troubleshooting of the little faults during the past year! The 32 -page blueprint that may develop far from home -to the actual construction section of the ANNUAL is worth many O of simple portable sets or elaborate multi- tubers. times the purchase price of the book alone. Order the ANNUAL NOW -for the limited o GET THE ANNUAL NOW -and THEN go on your vacation! first edition is rapidly being bought up by It will be your radio safeguard! eager radio enthusiasts. o $1.00 a RADIO AGE ANNUAL $1.00 a ¡I Copy FOR 1925 Copy Some of the Features Flow to read and understand hookups. back receivers. neutrodynes, reflex hookups, Baby Het No. 2, a How to understand radio phenomena. Wonder Super -Het, and others. Building your first simple set. Flow to get rid of interference. flow to select the right receiver. How to make an amplifying unit. Substituting a tube for a crystal -building the first tube set. How to recognize and deal with every kind of tube trouble. How to amplify any kind of set. Another superheterodyne for the super experimenters. o Making a reflex set. Building your first Reinert. set. Hints on tracing troubles in super -heterodyne circuits. The renowned Baby Heterodyne No. 1. A three -tube long distance regenerator. Adding audio and radio stages to the Baby Het. A 3 -tube set that easily receives KGO on the loud speaker How to make a battery charger. from Ohio. How to make a loud speaker. Improving the ever popular Reinarts. D RADIO AGE ANNUAL BLUEPRINT SECTION with such AND MANY OTHER UP -TO- THE -MINUTE HOOKUPS AND pular hookups as the aperiodic variometer, loop sets, feed- ARTICLES.

o RADIO AGE ANNUAL COUPON RADIO AGE, INC., 500 North Dearborn St., Chicago, Ill. Gentlemen: 1 want to be one of the first to get the RADIO AGE ANNUAL FOR 1925. Enclosed find $1.00. If o I am not satisfied with the ANNUAL I will return it within five will 0 days and you refund my dollar. U Name. Address 11 o City State 9 7 -25 OI ICI ®oof GOo. o 12111121 Unusuál Features IncreaseReceivingEfficiency

IN less than six months the Ultra -Lowloss Condenser has proved its right to leadership by greatly simplified design, greater tuning efficiency, and radically different operating results -not only in the eyes of scientific and engineering men, but with the buying public as well. These are the predominating Ultra -Lowloss features: (1) Single insulation strip reduces leakage losses materially, (2) Monoblock mounting with plates cast into block reduces series resistance and assures positive contact, (3) Minimum of metal of high resistance material in the field and frame reduces eddy current losses, (4) Cutlass Stator Plates produce a straight line wavelength curve -separating stations evenly over the dial. Each degree on a 100 degree scale dial represents approximately 3% meters over the broadcast wavelength range. This even separation applies to both high and low wavelengths! Simplifies tuning materially! The Ultra -Lowloss Condenser is a recent development of R. E. Lacault, To manufacturers E.E., originator of the famous Ultradyne Receiver. Sunpiifies radio tuning. who wish to improve Pencil record a station on Design of Lowloss Coils furnished free with each Condenser for amateur and their sets Om dial- thereafter simply broadcast wavelengths showing which will function most efficiently with the turn the finder to your Condenser. Twill gladly consult with pencil mark to get that in- At your Dealer's. Otherwise, send purchase any manufacturer regard- stantly. Easy -quick to price and you will be supplied postpaid. ing the application of this mount. Eliminates fum- condenser to his circuit bling, guessing. Furnished for obtaining best possible clockwise or anti -clockwise efficiency. in gold or silver finish. Gear ratio 20 to 1. Silver $2.50. In gold finish, $3.50. tILTR7-LOTj)bOSS úLTR14 V RP1ER CON DENSER TUNING CONTROL IJ'rite for Descriptive Folder.

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$ Tested and Approved by RADIO AGE 2 RADIO AGE for August, 1925 The Magazine of the Hour A Chat With ÚKO the Editor THIS issue of our magazine The Magazine of the Hour 1 is a milepost in our progress. Established Mach, the This is the twelfth consecu- WITH WHICH IS COMBINED RADIO TOPICS tive month in which RADIO AGE has presented a group of blueprints with accompanying con - I- olunie -1 August, 1925 Number S structional detail. It is fitting, therefore, that we celebrate the close of our first blueprint year CONTENTS by offering our readers a collec- - Page tion of blueprints which comprise all the basic circuits known to Radio Editorials.__._. 4 radio. Upon the circuits described Winner of the Radio Age Popularity Contest ...... 7 and illustrated in this group ALL hookups are developed. Other A Plea for More Smooth Tuning Receivers 9 arrangements may differ from the By Brainard Foote parent circuit in many details but fundamentally all of them are only Realizing Economy with A. C. Tubes. 11 adaptations of one of the basic Deciding on a Portable Super 13 designs inside this cover. By Russell H. Hopkins It will be remembered by radio fans that RADIO AGE was the Variations in DX Reception and Their Causes______15 first magazine to present illustra- By Ernest Pfaff, Assoc., I. R. E. tions of radio circuits in picture Some Radio Luminaries Why 17 form. That is, we were far ahead -and magazines in producing A Page of Interesting Pictures of all other drawings in which the parts of the Announcing a Prize Contest for Readers . 18 receiver were indicated in their proper location, thus getting. away Pickups and Hookups by Our Readers 19 from the ancient schematic dia- Conducted by F. A. Hill gram. Many old timers still pre- RADIO AGE BLUEPRINT SECTION 23 -84 fer the wiring diagram but the The First Real Presentation of All Basic Radio Hookups- continued success of RADIO AGE Illustrated profusely with Radio Age Blueprints. shows that there are many thousands of fans who prefer the pic- the Radio Manufacturers 85 ture diagrams. This magazine Standard Radio Receivers. 87 therefore gives both, and has been doing for two years. Corrected List of Broadcasting Stations. 98 OtsoOtherher magazines have fallen into line, although tardily and the picture diagram is an essential Radio Age is published monthly by RADIO AGE, Inc. these days. We predicted we Member: Audit Bureau of Circulations. would have imitators and we are that our competitors have Address all communications to RADIO AGE. INC. pleased Executive, Editorial and Advertising Offices justified our prophetic accuracy 500 N. Dearborn Street, Chicago, III. and at the same time have flattered Publication Office, Mount Morris, Ill. us by thus plainly showing their approval of our original methods of FREDERICK A. SMITH, Editor helping those who built their own. FRANK D. PEARNE, Technical Editor M. B. SMITH, Business Manager Now several other publications have taken a deep breath and Advertising Director leaped into the making of - blue HARRY A. ACKERBURG prints. After one year of offering 500 N. Dearborn St., Chicago, 111. an exclusive blueprint feature we Eastern Representative again are pleased to have "follow DAVIDSON & HEVEY, 17 West 42nd St., New York City the leader" publications admit they have been behind the times Pacific Coast Representative for twelve months. V. M. DEPUTY & ASSOCIATES, 515 F. W. Braun Bldg., After all, what makes a "big "mag - Los Angeles, Cal. azine? We leave the answer to you. Final Advertising forms close on the 20th of the 2nd month preceding date of issue 'Z Vol. 4. No. 8. Issued monthly. Subscription price *2.50 a year. August, 1925. Entered as second -class matter at post office at Mount Moms, Illinois, under the Act of March 3, 1879. Cayyriche, 1555. b5 RA DIO AGE, Iva. Loltor Radio Age. RADIO AGE for August, 1923 Tite Magazine of the Hour

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X Tested and Approved by RADIO ACE .' 4 RADIO AGE for August, 1923 The Magazine of the Hour

RADIO Corporation of America has quit its fight several years and have been making mental bets that to deprive RADIO AGE of its name. It now certain individuals in the trade would succeed and that appears that the title of this magazine will be duly certain others, who bore the outward appearance of registered in the United States Patent Office at Wash- success, would fail. Most of the bets were cashed. ington and that the publishers will be left in peaceful Makers of sets and parts either kept faith with the enjoyment of the snappiest and most expressive name public or they did not keep faith. They were either in the radio publication field. after a quick dollar or they were intent on establishing The immediate reason for this fortunate ending of a sound business. They were either price -cutters or the controversy is the decision of Radio Corporation they aligned themselves with the anti -gyp forces. to discontinue publishing "Wireless Age." The Cor- They were building up suspicion of radio performance poration bought 'Vi'ireless Age" with other assets which by selling inferior stuff or they were fortifying the radio it took over from the Marconi Wireless Telegraph industry by selling merchandise that would function. Company several years ago. The radio men with the conscience are still in When RADIO AGE applied to the Patent Office the industry and they are preparing for immense pro- in July 1924 for registration of its title the Radio duction this season. Some of them have been adver- Corporation interposed formal opposition on the ground tising in RADIO AGE since popular broadcasting. that the name RADIO AGE was causing confusion first thrilled the country and they are still advertising.. in the public mind between RADIO AGE and "Wire- It is a pleasure to see their names in the book. They,- less Age." The publishers of RADIO AGE, having prove that honest manufacture and honest merchan -- been building up the prestige of their name for several dising pays. years, resisted the Radio Corporation's contention As time passes it is going to be increasingly diffienfr. vigorously and the details of the controversy have for the gyp and the maker of shoddy radio to exist. interested many thousands of radio fans, as well as The fans are educated. If just entering the fascinating editors and publishers who are naturally interested in art they have friends in plenty who will warn then= such litigation. away from the catch -penny purveyors. We want to It is to be regretted that the legal points involved add our voice to the general chorus and warn the radio could not have gone to a decision. This magazine has beginners to let the flashy stuff alone. Buy from the been sincere in its conviction that it was morally and manufacturer or the dealer who has invested heavily of legally entitled to the name which it has endeavored money and effort to build his business. He respects his to identify honorably and helpfully with the progress business and will not jeopardize it by gyping customers. of radio in the United States. Deal with manufacturers who advertise in reputable We are informed that the subscription list of "Wire- radio publications. Wise publishers will not knowingly, less Age" has been sold to another radio publication accept advertisements from sources which do not give and that the Corporation's magazine will not appear value received. after the August issue. This is, perhaps, a develop- Radio progress has been marvelous but it woud'd! ment which points to more compactness in the radio have been more speedy if it had not been for ehe' publication field. RADIO AGE, in the last few years, ghouls who tried to raid it before its structure was has absorbed two other radio periodicals. It is a field scracely begun. The radio industry is on its feet and of free competition and only the fit will survive. It it is a giant. The day of the gyp is numbered. is a business so keenly competitive that the successful radio publisher must make a business of radio publishing and not attempt to make it pay him dividends as a Certain editors of radio publications constantly are sort of by- product of his other publishing or commercial shouting that their editorial columns are not for sale. enterprises. Yet we seem to detect evidences that some of them As the dove of peace settles down upon our editorial have been sadly tempted. desk we look about us at the discarded implements of war and we have the same sort of feeling that swept Radio is fortunate in having one of its leactii g- over us a few minutes after 11 a. m., Nov. 11, 1918. We were a battlefront war correspondent and while the figures represented in the MacMillan expedition to the arctics. presence of E. F. MacDonald, yiaesii dead were still being carried from the American field The Jr., walked up to the German barbed wire and across it dent of the Zenith and Radio Corporation, as comdl- we er of MacMillan's second ship, the "Peary" assures the exchanged questions with Fritz as to what all the shoot - in' was for. world that whether this adventurous group find tlhe had unexplored continent or not they at least will giive low The boys from the fatherland their notions wave on the matter and we had ours. But we agreed on one radio transmission the most effective test in has thing-the dadblamed rukkus was over and we couldn't ever enjoyed. wait to cut across the shell -holed scenery and get back to the pursuits of peace. Peace, be it said, with honor. We are receiving numerous letters from our English Away with legal briefs! Bring on the blueprints! and Australian readers. They are eagerly testing and proving the blueprints. Brazil, Japan, Holland, THE radio man who has been mixing his conscience Germany, France and South Africa, as well as Mexico, with his business policy is stepping out on the Cuba and Porto Rico are represented on the growing long, straight highway which leads to permanence and subscription list. Verily the hook -up is the same in prosperity. We have been watching the radio trade for all languages. RADIO AGE for August, 1923 The .Ita.'a^ine of the Hour

Introducing the Winner!

Photo posed e.oeoisar for RADIO AGE. HE WINS RADIO AGE SHIELD Karl Bonawitz, premiere organist for Radio Station WIP, the Gimbel Brothers radiocast at Philadelphia, Pa., emerged with first honors securely won after the final count in the first annual RADIO AGE Broadcast Entertainers' Popularity Contest. Karl maintained a steady lead throughout the entire competition, which started last July. A picture of the shield to be presented to him will be found on page 8, this issue, with the Contest Editor's comment on pages 7 and 8. ou may escape t7ie collection but not the need o ETICE THE satisfaction you receive from your radio depends We Have Openings for a Few not on what it does once in a while -but night after More Ozarka Factory night and month after month. Whether you grin or cuss Representatives depends on the service behind your radio. OZARKA Incorporated, is now entering its 4th year. From a beginning with one engineer, Ozarka radio instruments are do not buy the Ozarka. If you one stenographer, one salesman - our present only by trained factory rep- do buy it, you can rest assured, president, the Ozarka organization has grown to sold over 3100 people. There must be some good resentatives, men who not only no matter what happens, a com- reason for this growth. specialize in radio but sell and petent service man is at your Ozarka instruments have made good they service Ozarkas only. 3,100 call at all times. No Ozarka have more than met competition. Ozarka- repre- of these men, trained directly representative can sell Ozarka sentatives have made good not only because under Ozarka engineers consti- Instruments without giving Ozarka instruments were right, but because they tute a service force, unequalled Ozarka service. You are entitled to have been willing to learn what Ozarka engi- such service -demand it! neers were willing and capable to teach them - elsewhere in radio today. Ozarka unusual salesmanship and Ozarka service. The Representative There are still openings for the right men in this organi- When you buy a radio you'll Ozarka zation -men who believe in the future of radio -men who knows every part, every wire are tired of working for some one else-men who want a compare appearance, tone, vol- fact business of their own. Prove yourself by sales and will- ume and selectivity by having of the Ozarka. In he com- ingness to learn and exclusive territory will be given you. pletely his own The man we want has lived in his community for some various instruments set up in assembles time. He has the respect of his fellow men because he has instruments. His training on never "put anything over" Just to make money. He may your own home but -that isn't not have much money, but he is not broke and is, at installations, aerials, ground least, able to purchase one demonstrating instrument. enough- compare the service connections, operation and behind each one. service comes directly under our own Check Coupon for FREE Selling Book Any Ozarka factory represent- engineers who designed and perfected Radio offers a wonderful opportunity to men who are will- the Ozarks circuit. ing to start at the bottom and build. You need not know ative will set up an Ozarka in salemansbip, bu will you learn what we will gladly teach you? You may not know radio. your home -he will not even That is why our book, `Ozarka but we can and will teach you if you No.200," describ- will do your part. With such knowl- operate it himself, but depend Instruments Uzsa:tP: edge and willingness to work ,it doesn't for his sale on what you your- ing all models of Ozarka should Ran seem possible tbat you cannot make self do. If you, by your own be of particular interest to you. This good. Sign the coupon below, don't book and the name of the Ozarka rep- fail to give the name of your county. operating, do not bring in the Better still write a letter, tell us about resentative near you, will be sent yourself and attach the coupon. if distance, the volume and tone, immediately at your request. Please interested in our salesman's plan ask you expect a radio to give, then give the name of your county. for "Ozarka Plan No. 100." INca RP QRATEU 121 Austin and La Salle Streets 121 Austin and La Salle Streets Chicago, Illinois Chicago, Illinois

Gentlemen: Without obligation send book "Ozarka Instru. Gentlemen: I am greatly interested in the FREE book "The meats No. 200" and name of Ozarka representative. Ozarka Plan" whereby I can sell your radio instruments. Name Name Address City Address City County State County State- * Tested and Approved by RADIO AGE ©CIB665129 AUG 14 '25 RADIO AGE, for August, 1925 The Magazine of ¡he Hour 7

i tie Map3ine pithe Hour

A Monthly Pu blicatian M. B. Smith Devoted to Practical Frederick A. Smith Business Manager Radia Editor

Results of Readers' Vote -- I30 \AWITZ WI \S Contest! BY popular acclamation, Karl Bona - By HARRY when the announcer from Hastings witz, organist, has been chosen ALDINE deposed H. W. Arlin from second place. winner of the RADIO AGE Two months later Bert Davis came along Broadcast Entertainers' Popularity Con- respect to the strains of an organ, the and shoved Hay off his comfortable test for 1924 -25. By virtue of his victory performances were limited and pitted perch. For the next sixty days it looked he will be awarded the winner's shield. against a handicap of entertainers who as if the congenial announcer were Getting off on an early start, the name performed nightly over the microphone. through. Karl Bonawitz appeared in eighth posi- Bill Hay Then, suddenly, Bill Hay staged the tion after the first thirty days of the con- most remarkable comeback in the history test. During the next month he climbed Bill Hay, Announcer of KFKX, the of the contest. Holding a poor third, to third place. Then with the contest Westinghouse station at Hastings, with John S. Daggett and H. W. Arlin only one quarter of the way through, he Nebraska, in addition to taking second close on his heels, the scattered forces suddenly jumped to the head of the list place in the contest, must be given credit rallied round Hay, and with a deluge of where he has been continuously threaten- in being named the greatest announcer votes pushed him back to the seat of ed by Bill Hay, Bert Davis and H. W. in the world. For from among the great honor second only to Karl Bonawitz. Arlin, but never at any time displaced. array of talent, Bill Hay succeeded in Twenty -one more votes would have K. B., as he is familiarly known to the pulling more votes than any other declared him winner, which is the closest thousands of radio fans, might justly be announcer. He is the only candidate who the organist has been to defeat in recent christened "The Monarch of the Reeds." drew the greatest number of monthly months. One year ago, in the July, 1924, issue votes on three different occasions. Forty-one votes behind Bill Hay of RADIO AGE, there appeared a full Hay is Consistent comes "The Clown of the Air," Bert page announcement of the RADIO AGE Davis, for third honors. While Bonawitz Broadcast Entertainers' Popularity Con- HE, like Bonawitz, took off to early and Hay had a thirty day start on the test. start and was never at any time lower eccentric comedian from \VQJ, Bert made "\Vho is your candidate for the Radio than third position. Starting at the an excellent showing and for a time it Hall of Fame ?" is the way it was pre- head of the list, he gave way to the appeared that he would run away with sented to our readers. organist and H. W. Arlin. And there he first honors. The fans whose votes stayed to the end of the seventh month, placed the eccentric entertainer at this Open To All . point of vantage, will undoubtedly HE candidate could be any person regret having deserted him during the identified with radio, including an- last few days when a comparatively few nouncers, entertainers, inventors, manu- ballots would have put him over the top. facturers, or in fact any person in any By way of consolation, it must be manner connected with the great radio noted that Bert Davis has been pro- industry. Beginning with that issue, claimed the leader in his particular style ballots appeared in twelve successive of entertainment, as no singing comedian numbers of the magazine, the last one leads him in the final accounting. A being presented in RADIO AGE for wandering minstrel, more or less, since June, 1925. he first started performing over the radio, During that period thousands of radio the Clown of the Air is now started on fans were given the opportunity of nam- what will be the first leg of a trip around ing their favorite, and as each ballot the world. iñ every instance registered only one Fourth on the list, we find "Uncle vote for the candidate, it is believed that John S. Daggett," the beloved announcer the winner was selected strictly on his of KHJ, Los Angeles. Here again we own. merits. RADIO AGE maintained must pause to recognize an exceptional an attitude of strictest impartiality achievement in Uncle John's having throughout the contest. landed a place so close to the top. Locat- In receiving the votes, after the contest ed way out on the Pacific Coast, far had ended on midnight of June 15, a from the center of population of the number of interesting facts was dis- United States, added to the fact that closed. the contest had been in progress for sixty It is quite singular to note that of all Bill Hay, genial host at KFKX, Hastings, days before his name was mentioned in the hundreds of candidates, that the Neb., who was among the leaders when the RADIO AGE, makes his showing all the heaviest vote should have been polled final vote was taken in RADIO AGE's more remarkable. From among the in favor of an organist. For with all due Popularity Contest. He won second place. many broadcasting stations in his section 8 RADIO AGE for August, 1925 The Magazine of the Hour

of the country, he is the outstanding In the two years that followed, Karl figure west of the Rockies. Bonawitz has rendered over two thousand H. W. Arlin, the world's pioneer compositions. Thousands of letters and announcer from Station KDKA, comes telegrams give testimony to the recep- fifth. During the early stages of the tion accorded this popular entertainer. contest our friend front Pittsburgh con- Performing from one of the largest sistently held a corner on the position instruments in the country, this pioneer next to the top for six consecutive broadcasting organist "Could make the months. It was during the early part reeds talk," and the simple manner in of 1925 that his support gave way to find which he made his announcements him eventually a little lower down the between numbers made the listeners scale. His record is worthy of commen- realize that he was not "acting." dation. RADIO AGE congratulates Karl There then follows in the order named Bonawitz on his success. In behalf of Coon Sanders' Night Hawks and Art the others who made such an excellent Linick, both of KYW; Jack Nelson of showing, we can only regret that there is WJJD, Harry Snodgrass, formerly WOS, but one first place. and Ford and Glenn of WLS. A reference to the "Final Standing" will show A Word from the Winner how the next twenty stood. SINCE closing its first editorial There follows the standing of the can- forms, RADIO AGE has been didates as it looks at the conclusion of the fortunate enough to hear from the contest: winner Bonawitz. He is now "The Clown of the Air," Bert Davis, who -Karl play- FINAL STANDING made a big spurt toward the end of the con- ing the organ in the Stanley Theater in Karl Bonawstz, Organist..____..._ WIP, Philadelphia test and missed winning the coveted shield Atlantic City, N. J., where the bathing Bill Hay, Announcer VITIOC Hastings by only a few votes. Bert's popularity beauties flock every year. Bert Davis, Entertainer.____.._._.._...WQJ, Chicago among Middle Western fans grew amazingly However, let's let Karl tell the story in John S. Daggett, Announcer ._ KHJ, Los Angeles during the life of the contest. He finished third. his own way. H. W. Arlin, Announcer KDKA, Pittsburgh Here's his letter: Coon -Sanders' Nighthawks OrchestraKYW, Chicago Jack Nelson, Anouncer._ ..... ____WJJD, Mooseheart fortunate shut -ins, he surely deserves to "Harry Aldine, Art Linick, Entertainer ._____ ..._...... KYW, Chicago win your contest. Popularity Contest Editor, Harry M. Snodgrass, Entertainer Very truly yours, RADIO AGE: WOS, Jefferson City Thomas Prentice. "Dear Harry: Ford & Glenn. Entertainers ..... __._..WLS. Chicago "I received your kind letter and I am Duncan Sisters, Entertainers______..KYW, Chicago His Life Story Lee Sims, Pianist __.KYW, Chicago very much pleased to hear that I have Lambdin Kay, Announcer._..__..._ WSB, Atlanta Karl Bonawitz was born in Phila- won the RADIO AGE Radio Favorite J. Remington Welsch, Organ ist____...KYW, Chicago delphia in 1894. He studied organ, piano Popularity Contest, which was begun a 'Fred Smith, Announcer..- ____..WLW, Cincinnatti and musical composition in that city; year or so ago. E. L. Tyson, Announcer.--- __WWJ, Detroit also in London and in Berlin. Hired Hand, Announcer._.__ WBAP, Fort Worth "I stopped broadcasting a month ago, The thousands of radio fans who have although I notice I have been getting "Sen" Kaney, Announcer._.___ - KYW, Chicago heard and enjoyed his organ recitals were Nick B. Harris, Entertainer...... _KFI, Los Angeles votes since then. When I saw that there Jerry Sullivan, Announcer- Entertainer_ -.... first introduced to him at the German- might be a chance of my winning your he went WQJ, Chicago town Theatre, where on the air contest, I made several announcements Edward H. Smith, Director -Player._._...__..... for his initial performance. This was by radio concerning your excellent maga- WGY, Schenectady in May, 1923. zine and its popularity contest., Charles E. Erbstein, Announcer .. _..WTAS, Elgin He was at once accepted by the delight- "I started broadcasting from the Ger- Wendell Hall, Entertainer._-__.WDAF, Kansas City ed fans, who an of con- sent avalanche organ on May 15, Howard Mriholland, Announcer.._.__.KGO, Oakland gratulatory messages to the Gimbel mantown Theater Scottish Rite Orchestra.. _..____... _._._-KGO, Oakland Brothers Station, WIP, Philadelphia, 1923, and thereafter I was on the air Banks Kennedy, Entertainer.._...__.WEBH, Chicago at and four times a week with organ who broadcast the strains of the German- three S. Hastings, Announcer...___...._....KFI, Los Angeles recitals and Sunday night concerts. Robert Boniel, Anonncer.___....__ -WEBH, Chicago town organ. I from all over Arion Trio, Instrumental KGO, Oakland have letters the country Gold Dust Twins. Entertainers _.WEAF. New York and telegrams numbering over 1,500. I have never received a penny for broad- And now a few additional remarks about casting, and in two years of this work I the winner of the contest. What was have given approximately 336 hours of there about the performances of Karl my time. Bonawitz that won for him first place in "But don't get me wrong. I did it the hearts of the great radio audience? Rida_ _0t4./);4;1111 willingly and would certainly do it all The following is a letter typical of over again, as I firmly believe radio the many which accompanied the votes kV{ Kt:l=-íz work is the greatest advertising medium received by Harry Aldine. in the world. "Now, you wanted to know something 123 Waverly Place, Utl:sl.' 3 I will Trenton, New Jersey, of my new activities. On July of the Stanley 1925. be solo organist new February 4, N. We may RADIO AGE, Theater in Atlantic City, J. Lí:el::L>i 1 LEl",11i.Yi lt:kt.' soon be on the air again through Station 500 N. Dearborn St., you Chicago, Illinois. WVPG at Atlantic City. However, might write in your paper that my posi- Att.: Mr. Harry Aldine, Contest Editor. l'l21:11LJaY'Y C i i:1t1 tion will be changed from the German- Gentlemen: town Theater in Philadelphia to the Kindly enter my vote herewith for Mr. Stanley Theater at Atlantic City. Karl Bonawitz. His informal Manner of announcing makes one feel he is playing "I hope you'll pardon my hurried note, for the liseners in personal benefit. His and let me know if at any time I can be of happy manner is certainly medicine to service to you. those who cannot get out of a sick room. "Sincerely, A view of the shield which is to be presented "Karl Bonawitz." If this peculiar method of announcing to Karl Bonawitz on behalf of the readers of and his clever playing can in any way RADIO AGE. It measures six by eight And so ends the contest. Long live make life more worth while to un- inches over all: the king! RADIO AGE for August, 1925 The :Magazine of the Hour A Plea for More Smooth- Tuning Receivers Failure 45 turns to Balance the Tuning Conden- ser and Coil 1 Causes Woe BY BRAINARD FOOTE SO OFTEN we come across a radio set whose tuning dial includes the entire broadcast band within perhaps 50 degrees on a 100 degree dial. .0005 condenser The short -wave stations like WFKB, Chicago, and WHT, Deerfield, Ill., come in at 30 and we find KSD around 80. Fig. I -A simple wavemeter that will help Sometimes, and really almost as often, in the process of fixing the coil and con - the short -wave stations aren't heard denser tuning range. The points for 200 meters and 550 meters are noted on the wave - at all. The blank spaces at either ex- meter scale by the absorption method in con- tremity of the dial are absolutely useless nection with the regular receiving set, before and they only serve to compress the the 'fixing" process is started useful timing scale within narrow limits and to render much more difficult the exact adjustment of the dial. What's wrong, anyway? Why don't and that fewer turns of wire will be moisture and then paraffined to pre we have sets that tune with smoothness nceded to place the lowest wavelength vent moisture from penetrating. The from 200 to 550 meters over a scale of at the desired point -200 meters for actual number of turns must be dc- zero to 100? The fault is that the tuning broadcast reception. The effect of the termined by experiment, according to condenser and the coil are not properly tuning condenser is thus decreased; that the capacity of the condenser, and of balanced. Perhaps the coil is too big is, a larger condenser is necessary to that we shall speak later on. or the condenser too big. Does the cover the broadcast band. trouble lie possibly in the design of the Now suppose we wind a coil to have Spacing coil? There's a little of each to be con- very little distributed capacity. This THE simplest method of spacing is to sidered. may be done in various ways, the simplest use two wires, winding them both In the first place, we should recall of which is perhaps to employ the on at once. After the coil is complete, the well- proved statement that the "basket" construction, where the turns one wire is unwrapped and the remaining loudest signals are obtained with a criss -cross and come near each other only turns are correctly spaced by the diameter minimum of capacity and a maximum at the crossing points. This method is- of one wire. A useful wire to use for of inductance in the circuit. This fact very desirable because of the reduction such work is enamelled, without other used to be used in support of the vari- of distributed capacity, but it has a insulation. It will "sink" into the ometer method of tuning the secondary serious drawback not commonly thought paraffined surface sufficiently to retain circuit, but the extra length of wire about. The wire in a coil must describe its position of spacing. Hard rubber required by the variometer and its added a certaiu number of revolutions at a tubing is likely to shrink, so that it must resistance wasn't considered. To keep given diameter to attain a certain amount be used for space wound coils only where . inductance high and capacity low, it is of inductance. If each revolution is a it is threaded and the wire wound in the evident that the circuit is 100 per cent circle of that diameter, the length of grooves. efficient (if there is any such thing) at wire needed will be a minimum, inas- Now for coordinating the condenser some short wavelength at which the much as the circle is the geometrical and coil. Take the usual combination capacity is sufficient to make the circuit shape having the largest inclosed area of coil and 23 plate or .0005 mfds. vari- oscillatory and at which the inductance for its perimeter. The basket form able condenser. Its effective work may is predominant. This would be near involves a number of angles and the start at 15 or 20 on the dial and wind the "natural wavelength" of the coil. length of wire per turn of wire on the up at 90. On the lower settings it Distributed Capacity coil is quite a bit greater. Thus the doesn't amount to much. The trouble resistance will be increased. is that the coil is built to produce the THE fact that a coil has a natural Hence, the ideal form of winding is one longest wavelength near the highest wavelength without a condenser having a cylindrical shape where the setting of the .0005 mfds. condenser and connected across it may be understood turns are spaced from each other suffi- then the short wave setting occurs when it is shown that a coil is NOT pure ciently to reduce the distributed capacity, wherever luck puts it- usually around inductance. It has a certain amount but not with so much separation that 20 or su. Now it is NOT possible to of inherent capacity, which is caused the field is tuo extensive. A spacing design a space,wound coil for such a by the side -by -side position of the equal to the diameter of une wire is condenser, and the easiest and most adjacent wires. When the wire is in- correct and the ideal wire size is from practical method for the constructor sulated with enamel or single silk, and No. 18 to No. 22. Such a coil can easily to follow is as follows: wound closely, the turns lie very near be made by using a treated cardboard 1. Wind the space -wound coil with each other and the distributed capacity form about 4 or 5 inches in diameter and too many turns, perhaps 65 or 70. Insert is very high. This mcans that the coil about 6 inches long. The form should the coil in the set, with the tuning con- already has a certain amount of capacity be heated in the oven to drive out the denser at zero and find the wavelength, 10 RADIO AGE for August, 1925 The Magazine of the Hour which will be the natural wavelength of the coil plus an increase due to the minimum condenser setting and the tube capacity. This wavelength should be 200 meters, and to be absolutely certain

about it some kind of a wavemeter is 530 I helpful. KSD A wavemeter for the purpose may r4- easily be made by winding about 45 / I turns of wire on a 3 inch piece of tubing about 3 inches long, using small wires, H a- say No. 24 single covered. Place binding posts on the coil and fasten lengths of I i'I bus bar in them and to the posts of a 15 p9.0t9.0 Lou.), 60 .0005 mfds. mounted variable condenser as in Fig. 1. Next, tune in the amateurs JPa4.12d. on 200 meters (where the whistling dots tuiwt..o and dashes are to be found.) Or, if 200 (a) meters cannot be heard on your regular set, tune in the shortest wavelength station you get, perhaps WFKB on 217 meters, let the set oscillate and bring the wavemeter near the coil of the set. Vary its condenser and at a certain point it will, by absorption, stop the set from oscillating. This is the corresponding point on the wavemeter. Note the dial reading and then install your space wound coil, with tuning condenser at zero and the tickler winding placed in inductive WFK relation so that the tube is just oscillat- zoo ing. Bring the wavemeter near and vary 2,5 100 the condenser. If the absorption point is less than the wavemeter setting for. OLDS J¿/K,l,i1Q/J 217 meters by a few degrees, say four 2. or five, the natural of the coil is O. K. But if it is higher, some turns must be removed until the lowest wavelength Fig. 2- Comparative tuning curves showing the advantage gained by using a space wound tuned in is about 200 meters. It is best coil and a smaller condenser. The 15-plate condenser was made by removing five of to have the antenna off and the antenna the rotor plates from the 25 plate instrument, the corresponding 5 fixed plates thus not coupling coil out of the way while doing being used. this. 2. The shortest wave is thus put at pulled out (as with a condenser having line wavelength condenser and a close - 200 meters with the tuning condenser plates held in slots.) In a typical case, wound coil of 45 turns. 200 meters at zero. Now increase the tuning con- I used a straight -line wavelength con- occur at about 25 on the dial in this denser gradually until the wavemeter denser having 25 plates and .0005 mfds. case, on account of the slight change in absorption method shows that the con- capacity with a space -wound coil that had to have 60 turns for 200 meters at capacity of such a condenser on short denser is set at the highest wavelength, wavelengths. No advantage was taken higher, say 550 zero condenser setting. It was necessary or a little about meters. to pull out FIVE of the rotor plates of the good tuning possible on short This will undoubtedly occur at about waves with 60 or 70 on its dial, showing that the before the tuning range was properly a condenser of this character. condenser has too much capacity. Some spread over the dial. Fig. 2 shows this. But with the space wound coil, even with a great many more turns, zero of its plates are then removed by bending Ease of Tuning the them back and forth a few times until setting is brought to 200 meters, on they either break off at the rotor shaft THE steeper curve of Fig. 2 shows account of the greatly reduced dis- or become loosened so that they can be the tuning scale with the straight- (Turn to page 92)

45v. ei

O N .3. J íck.Q2n. .0005

Fig. 3- Weagant- Reinartz circuit for the space wound coil and parts as used in the usual three- circuit tuner. This method of regeneration control doesn't interfere with the setting of the tuning dial. Try it. RADIO AGE for August, 1925 The Magazine of the Hour 11 Realizing Radio Economy with ALTE;RNATING CURRE \T Tubes THE elimination The tube draws a of batteries from filament current of radio receivers two amperes. A small has been the aim of nickel cylinder C, 1 -8 engineers for a num- of an inch in diameter ber of years. The and an inch and a logical place fro m half long, surrounds which to draw the the filament and is power to operate our heated by the white radio receivers is the hot filament F F to lamp socket. Here is slightly below red power in abundance, heat. The cylinder is cheaper by far than coated on the outside

that obtainable from with a layer of bar- ! dry batteries or stor- ium oxide. Surround- age batteries. But ing the cylinder C is the power is not in the regular spiral grid a form which can be G and the cylindri- used directly on the cal plate P. The tube modern tubes. is shown connected In the majority of in a regular single homes 110 volts A. circuit set, the plate C. is employed for voltage being sup - lighting purposes, Fig. 1. Here is the schematic drawing for a typical alternating current tube supplied plied by the "B" bat - whereas we require from the conventional 110 volt house supply. The filament F. F. is heated by the tery B. When the cyl- direct current to light transformer voltage and in turn it passes its heat to the cylinder C which gives off inder C is heated by the filaments of our an electronic emission. the filament inside tubes and to supply of it, it gives off them with plate volt- electrons and acts as age. How to use the the source of elec- alternating current trons for the tube. for the purpose -that Tz But since it is in no is the problem. Ob- way connected with viously there are two the alternating cur- alternatives open to rent lines, no hum us. Either we may can appear in the out- design a battery sub- put circuit of the stitute which will op- G tube. The alternat- erate from the alter- ing current serves nating current lines merely as a heating and supply power to source to raise the the types of vacuum Cg cylinder C to the pro- tubes now in use, or per temperature so we may design an that electrons will be entirely different type emitted. The rest of of tube which is cap- the circuit functions able of being oper- in the reuglar way. ated from alternating The grid return and current directly. the negative side of Without going into the B battery are the matter in any connected to the cyl- detail we may state inder C because this that the design of a is really the filament battery substitute to ( I I of the tube. supply both filament A. C. Tube and plate current tio Ac A Truly from alternating lines SO FAR so good. is a difficult matter Now let us elimi- indeed. The plate Fig. 2. Here the A. C. tube is combined with a kenetron to give us B battery nate the B battery, supply is a problem supply from A. C. mains after being rectified by the kenetron. making this a truly easyof solution; there A. C. tube. There are many successful "B" battery is no reason why we cannot use a eliminators on the market. By By EDWIN E. TURNER Jr. kenetron in place of the "B" bat- proper balancing it is possible to op- tery to supply the plate of the erate the filaments of amplifier tubes from These difficulties led to the develop- tube with high potential D. C. Figure alternating current supplied by a small ment of a tube which is capable of being 2 shows a tube of the type which we have step down transformer. The great and operated from alternating current di- just described, supplied with plate poten- heretofore insurmountable difficulty has rectly. Such a tube is shown in diagra- tial by means of a kenetron. G, P, C been the operation of the detector tube. matic form in Figure 1. The filament of and F. F. have the same meaning as Do what you will, if the filament of the the tube F. F. is a tungsten thread before. A second transformer T 2 sup- tube is operated from alternating current, heated to incandescence by the trans- plies the high potential A. C. which is there will be a terrific hum in the output former T which steps the line voltage rectified by the two element tube F2, Circuit. down to the proper value of 5 volts. P2. The large condenser C2 is con- 12 RADIO AGE for August, 1923 The Magazine of the Hour netted in shunt to the rectifier to smooth former serving both tubes. The values out the voltage supplied to the plate. shown are the same as before. One fact stands out from figure 2: namely, that the anode of the kenetron P2 and A Little Experiment the source of electrons of the tube C THE arrangements shown up to this are connected together directly. There point operate satisfactorily on alter- is no good reason, therefore, why they nating current, but it will be noted that cannot be combined into one electrode. the circuits contain transformers and Also, there is no reason why the fila- other accessories which may be elimi- ment F2 and the filament FF cannot be nated if we take the pains to analyze combined into one, since the function of the circuits. Let us see if we can operate the filament FF is simply to heat the the filament of the tube directly front cylinder C. Also, the high potential alternating current at 110 volts, incor- winding S can be wound on the same porating all the advantages which we transformer which supplies the filament have outlined. Figure 5 shows the current to FF, the primary of this trans- one' :,o A c. circuit when the tube has a 110 volt former serving for both. Fig. 3. This is a typical one tube regener- filament. The filament F operates from The combined circuit is shown in ative circuit with the A. C. tube arranged so 110 volts A. C. directly, operating exactly Figure 3. The filament, FF heated from it also delivers B battery current in addition as before to heat the cathode C and to A. C., serves not only to heat the equi- to the A current. furnish the electron emission for the potential cathode C, which in turn rectification taking place between _C serves as the secondary source of elec- Cl, C2 and C3 in parallel back to the and F. For the high potential to operate trons for the tube proper, but also acts electron source C. The winding S in the kenetron, C F, we employ the voltage as the cathode of the kenetron formed the tube circuit tested had a voltage of of the line by means of the well known by the cylinder C and the filament. The 110 volts. The circuit operated as a Edison effect. Every cycle this side cylinder C acts as the secondary source regenerative detector supplying all neces- of the line X becomes positive with of electrons íor the tube C., G, P and at sary power from the lighting circuit respect to the side of the filament Y. Hence there is an electron flow and rectification between Y and C. The condenser C serves to smooth out the rectified currents, making the operation of the tube more smooth. The extreme simplicity of the receiver can be appreciated at a glance. And as a last step in order to bring the circuit to the highest point of efficiency, let us make the change shown in Figure 6 by making the connection to the plate of the tube to the middle point of the filament F, instead of to one side of the line. At once we have done two things. We have caused the receiver to be connected to the alternating current lines at a point which is always at equal potential with respect to both sides of the line. This alone tends toward the elimination of the hum. At the same time we have substituted for the half wave rectification furnished by the Edison effect a full -wave rectification. Elec- tron flow and rectification takes place Fig. 4. The alternating current tube adapted to the two stage amplifier in which the B every half cycle instead of every cycle. battery potential is also produced by the A. C. tube. The electron flow takes place first from one end of the filament and then from the the same time acts as the anode for the other. The result is a smoother output kenetron FF, C. The high potential to the receiver and less hum. winding S is connected to the middle point of the filament lighting secondary. By tracing the circuit carefully, it will be seen that at no point is the alternating current line connected to the filament circuits of the receiver, the 13 battery return being made through the electron stream from FF to C. With the tube tested by the author, condensers Cl, C2 and C3 were 2 M. F. each and resistances R1 and R2 were 36,000 ohms each. This combination forms a filter which serves to smooth out the plate supply to the tube. It will be noted that Fig. 5. Now we are using 110 volts on the these condensers in parallel are in shunt filament instead of a lower vol age. Also we to the source of high tension supply, the are supplying the plate potential through F,,, G positive terminal of which is the filament the rectifying properties of the same tube. FF and the negative terminal the cylinder Fig. 6. The above circuit shows us the C. The load across these condensers, at 60 cycles A. C. without the least A. C. tube at its highest e iency; it furn- upon close examination, will he found ishes A battery current or the electronic trace of hum. Figure 4 shows the emission and also furnishes its B to be the plate the C, own po- current of tube hookup of a two stage audio amplifier tential through the connection between the G, P by way of the tickler T, through the using these tubes. Each tube supplies plate of the tube and the center of the 110 telephones C4, through the condensers its oivn plate current, a single trans- volt filament. RADIO AGE fop August, 1925 The Magazine of the Hoar 1> Deciding on a Portable Super -Het r11%, Small Parts and Efficient Transformers are Vital for Real Portability

illThe portable super at the left gives a good example of how a multitube set should be laid out for true portability. Note the compact arrangement of batteries and the small space consumed by them. And can't you imagine how easy such a travelling case would BY RUSSELL be to carry on your vacation? H. HOPI< I NS IT HAS long been acknowledged that fears by assuring them that inter -stage Without it a receì%er may get the sta- the superheterodyne receiver is coupling can be made to disappear en- tions, but it will not get music, clarity the last word in radio development. tirely in well constructed portable re- or sweetness of tone. Selectivity, sensi- For all- around, all year reception, under ceivers. tivity and distance- getting features are all conditions, and for general in re- efficiency Use Small Parts admirable when combined one of operation, the "super" cannot be sur- ceiver, but tone is most important, for passed. IN designing a portable super, which we what good are distant stations if we do For too long a period the super was the have taken as our model receiver for not enjoy their offerings? instrument of the experimental labora- this discussion, it should be advisable to Portable superheterodyne receivers tory instead of the practical receiver of use instruments that have been purposely have been snubbed by some fans who the everyday fan. Too long have supers designed to permit their being placed in would otherwise be loyal boosters, just been great consumers of battery current small space. Otherwise we are taking because the designers, in their mad and occupiers of unwieldy space. Some great liberties in calling this a "portable" chase for extreme portability, forgot to radio engineers have attempted to reduce set. At the same time, these parts must include pleasing tone. Even after tone the battery drain by introducing com- not be so placed that they interfere has been achieved, a creditable loud plicated reffexing, but that addition did electrically with each other. speaker must be used to convey that not tend to bring about the desired In super- heterodynes, as in any receiv- pure tone to willing ears, and not con- simplicity that was essential if the super ers, short wires insure best results, so vert it into a "tinny," rasping squeal. was to become universally adopted. the fact that a super was once a complicat- Several small, built -in loud speakers are After testing about every known type ed affair need not make the prospective now available, so there should be no of superheterodyne design, from six builder believe that connections must be excuse for imperfect loud speaker re- to eight tube layouts and back again, elaborately though unnecessarily long. production in a portable set. a conclusion was arrived at that Then, again, if we mount our parts for all-around desirability, as well as compactly, long wiring will be done The Heart of the Super sensitivity, selectivity, weight and dura- away with and we will have attained our THE heart of the portable super, as bility, the portable superheterodyne ideal from the standpoint of wiring. well as of the more elaborate models, was the ideal receiver for the fan who If our portable super is to be a welcome is in its transformers, for they are the wants all the latest radio improvements companion on our Summer trips, instead real factors to consider when we set out arranged in such a way that they will of a cumbersome hindrance, it must be for results in amplification, tone quality, constitute a truly portable receiver, and easy to handle or we will wish we had selectivity, economy of current consump- not, as one radio pioneer so aptly put left it at home. And the next time we go tion and wavelength range. Accordingly, it, "so portable that one man -and six away, we will be sure to leave it at home, we will devote part of this discussion to boys -can easily carry it about." unless we make it as small as is possible the proper choice of transformers for the An ideal portable super -hererodyne without hampering mechanical perfec- portable superheterodyne. can be built on a panel 7 inches by 18 tion. To say that the question of high fre- inches by 3 -16 inch and a subpanel if In our quest for compactness, however, quency air -core transformers versus com- desired. If old-timers lift their eye- we should not be blinded to the fine paratively low frequency iron -core trans- brows in amazement and question the qualities that every receiver, and particu- formers in a superheterodyne is a much possibilities of inter -stage coupling and larly the super, should possess. The mooted one would be to be truthful but excessive crowding, we will allay their foremost lof _these is tonal quality. not at all original. However, the super 14 RADIO AGE for August, 1925 The Magazine of the Hour fan will be interested in a few of the facts side of a sufficiently wide speech -band. shift from 2,150 to, roughly, 1,600 meters responsible for the decision to recom- This would be the ideal condition, since for this particular set of transformers. mend iron -core transformers in port- amplification would remain constant even This indicated how very slightly dependable supers. though the transformers varied slightly, able the manufacturer's rating of the The best gain; that is, voltage amplifi- due to manufacturing difficulties. These operating efficiency of air -core transform- cation, that could be obtained with difficulties, however, are very much small- ers really is. At these low wavelengths standard air -core transformers varied er at 30 K. C. than at 100 K. C. in the changes like this are of considerable between 8 and 16 with an average of 14 case of air -core transformers, which are importance, whereas the changes which for 201A tubes and somewhat less for non -adjustable, the selectivity is depend- occur in iron -core amplifiers at higher UV199's. The voltage gain for the trans- ent upon each stage speaking at substan- waves are very slight, principally due to formers used in a portable super is 34 tially the same wavelength, the in -put the comparatively high distributed ca- per stage between UV199's. There is no transformer used with them being used pacity of the windings. argument here between the 100 kilo- principally for other purposes than to Since a 50 K. C. amplifier is more sta- cycle amplifier and the SO K. C. amplifier sharpen up the amplifier tuning. This is ble than a 100 K. C. one, less loss in the -though the average iron -core trans- very nice where each stage can be tuned forni of positive grid bias need be intro- formers on the market give a 14 to 18 individually but not so nice otherwise. duced to stabilize it. In actual practice voltage gain per stage. The two instru- In an iron -core amplifier the selectivity the former amplifier may be tuned with ments for which the makers make the is almost entirely determined by the filter, the grids from one to four volts negative most extensive claims give only 24 per which means that the selectivity of the with respect to the minus end of the fila- stage, whereas another transformer for amplifier is under easy and accessible ment for UV199's The average positive which no extensive claims are made gives control in one circuit -not distributed bias for air -core transformers at 100 30 per stage. These latter types are all over several non -adjustable circuits. K. C. with ÚV199 tubes is one-half to iron -core operating from 6,000 to 10,000 The primary complaint of lack of selec- two volts positive. It is an axiom that a meters-the low frequency of the last tivity in iron -core transformers is due to tube is inefficient when its grid is operat- one being its only drawback. the use of poor filters, as up to the present ing positive and where a strong signal It is possible to tune a 100 K. C. am- time practically no really sharp filters is to be handled distortion is bound to plifier using air -core transformers very have been marketed -the writer is fami- result from a positive amplifier grid. sharply and yet not cut side -bands. liar with only two which are not make- Besides being far more efficient in opera- It is possible to tune a 50 K. C. amplifier shifts, improperly designed. tion, a tube with a negative grid bias sufficiently sharply so as not to cut Attaining Stability consumes very much less current than a side -bands and yet eliminate noises, but tube with a positive bias. The writer it is very difficult to do so with a 30 K. C. THE lower the frequency, the greater has noticed in an amplifier using air-core amplifier. Under certain conditions the stability of an RF amplifier - transformers a current consumption, of perfectly matched air -core transform- the very principle of the super being 50 per cent greater than the consumption ers an amplifier might be made so sharp based on this law in a measure. The of an iron core 50 K. C. amplifier. as to cut the side -bands and distort feed -back effects are less the lower the The potentiometer controlling regen- speech received considerably. The dan- frequency, and are slight in a 50 K. C. eration on an air -core amplifier will ger of this is greater at long than at short intermediate amplifier and very easily generally, if retarded over thirty degrees waves, but since iron -core transformers overcome. Where an iron core is used of its arc, throw out a comparatively are generally used on the longer waves, in a transformer, the field is limited and strong station entirely. This indicates this difficulty disappears here and holds shielding may be employed efficiently that the nature of the gain in the ampli- only for the short wave amplifiers using if desired, although since the field is fier is mostly regenerative, since for good air -core transformers. limited, it is generally necessary to no sensitivity the amplifier must always Assuming the air -core transformers to greater extent than individual transform- be operated just below the oscillating be all adjusted to the same wavelength, er shields, which are provided on prac- point. This is not a good condition, the selectivity will be good. If one is off, tically all standard makes of iron -core since regeneration such as is necessary amplification will fall off badly and transformers. An ai r -core amplifier can- for sensitivity will distort the signal in selectivity will be poor, due to the very not be shielded without increasing its addition to rendering the control of the sharp peaks of the transformers. These bulk very noticeably, and unshielded set extremely critical. With an iron -core peaks must be sharp if any amplifica- require .( greater spacing than an iron - K. C. amplifier this is not the case -the tion at all is to be obtained from this core amplifier. operating at even the grids are run negative by a "C" battery system. Each transformer must be same wave length, in order to maintain and if a potentiometer is used it is merely matched for a given set, and the trans- stability. for volume control. The amplifier need formers in an amplifier should be matched With a given set of air-core trans- not be operated just under the oscillating for individual positions, since variations, formers designed for operation at 140 point to secure good selectivity, and the which to some extent can be predeter- K. C. with 201A tubes, the substitution of potentiometer may be retarded over its mined, occur from stage to stage. UV 199's would throw the operating entire scale in the case of a well de- In the assembly of the amplifier the frequency up to 190 K. C. signed amplifier without throwing a greatest care must be taken to see that This means that the wavelength would signal out. Unless the signal is weak, the characteristics it will be a gradual of each stage- assem- decrease, which bly are identical or means that is more all the advantages nearly a true vol- of a well -matched ume control than in set of air -core the previous case. transformers will be Yet the 50 K. C. lost. Due to the amplifier will give lower frequency at better amplification which iron -core with a non -critical transformers are op- adjustment than a erated, this trouble 100 K.C. operated at is practically never its limit -just before encountered and a the oscillating point. set of transformers could be built for Few Stages Best operation of SO K. THE fewer stages C., which will give Back view of a truly portable super -heterodyne, for Summer as well as we can use in an practically no dis- all -year use. Use of small parts enables the builder of a set like this to amplifier the more tortion and yet have mount his transformers under the tube sockets and out of the way, thus con- efficient each stage a sharpcut-off either serving valuable space. (Turn to page 93) RADIÓ AGE for August, 1925 7'ke Magazine of the Hour Where to Look for Faults in Reception, gradual decrease of signal intensity of a transmitting station of a given power, The Causes of at various distances from the source. It will be seen from the curve that it will take approximately nine units of energy to operate a crystal receiver. VARIATION in The threshold value of a regenerative receiver is lower, therefore, decreasing the amount of energy necessary to operate it to about eight units; similarly the regenerative and the neutrodyne re- DX Results ceivers require even less energy. Lastly the superheterodyne requires but one unit of energy to operate it and we are By ERNEST PFAFF consequently at the point where a further Assoc., I. R. E. increase of sensitivity will be of no avail, since at this point the noise becomes louder than the signal. In other IN VIEW of the fact that the more or atmosphere, which manifests itself in a words, if we decrease the threshold less experienced radio amateur, as fading of signal strength and deflection value of the superheterodyne which is well as the novice, is confronted of radio waves by large metallic masses. shown on the curve, there will be no in- with such a variety of confusing and con- These factors will be dealt with in some- crease in the range of the set because it is flicting information regarding the range what greater detail in the following already capable of picking up any 4 of various receiving sets, a non -technical paragraphs. signal that is audible above the most discussion of the factors limiting long Theoretically, increasing the sensitivity favorable winter noise level. distance reception will undoubtedly be of a radio receiver will increase its range, The summer noise level is so high that appreciated by many enthusiasts. because the energy necessary to operate the lightning discharges are made audi- It is the purpose of this article to point it will be reduced. The value of signal ble in the most unsensitive receiver. out the limitations of radio reception in strength necessary to operate any re- It should be noted that the noise appar- general, since the varied conditions under ceiving system is generally called the ently increases as the sensitivity of the which an instrument may be operated threshold value. The accompanying receiving instrument is increased. In makes it practically impossible to esti- curve will show the approximate thres- order to make the received signal audi- mate the range of a receiver with any hold value for the most common types of ble, it is obvious that it must be of greater degree of accuracy. This is due to receivers. Abnormal conditions some- amplitude than the noise level. The forces entirely beyond our control, such times cause results which may vary neutrodyne is capable of reaching the as atmospheric conditions involving the considerably, but these results are termed - summer noise level and during the amount of moisture in the air, electrical "freaks" and are not worthy of lengthy summer months would have a range charges which accumulate upon particles discussion. equal to that of any set. The super- of dust and moisture causing various The curve in sketch I gives an approxi- heterodyne, however, has the distinct forms of static, man -made electrical mate idea of the relative sensitivity of advantage of obtaining the maximum interference, interference between direct several very general types of receiving range which is possible under the very waves and waves which have been re- equipment. The line sloping down across best conditions of noise level and inter- flected from the upper strata of the earth's the chart from left to right indicates the ference. (Turn tie page)

N\ \. '11016.:10111 .1:1 a__.IllfIlll.'(n. 1-'/Il31,1i-a, pp7N.f. \\NN\Nle i/\\.íf.iSiy/ G/' ]L. ` O]..lSL'II7 ...N. 1/1_./"'%i.l 1.1111160. 1011 ...... Wilk W. Nr,- N. vl,n a NM;1, Bf4.1JN.-:'L1V:r./.r29Q: 111/1111211111111 MMMMMMMMMMM 1II6Y 111 nH 61.... :.i II1: ú1 \:iii~iiNNN.NNf: UNNl Ñ.,MI%NNN ' IM'II .N1 11 1 N I~ N.N....111 \...N '4: Jtl:,,7,71-4 /f.C---2.l1l III\\N\N\N 1 11.11 1111 1 411111/ ..: I Il\ IH N\ N u1111 ' 11 1.i'/.:1.+Jr, 7/Rr_.pT'1-I/\7.I.III il ..... 1111I11 .N:\\.1;.\ 111 11L' II M11\+ n 4 '7a!sl./yy 1/..ri7 411'1-/:.I1 1H1 111 ..N. . II.1 rL.r 1.1.211411111.I /N:.\\111111110,11111111 OM N6L.N1 1111,ll N re. /1 .r.l...l N I/ 1E0,1 El 1116 ../ 1121111115 on. UI Wive N ... .r!7.N.I!uNN1.N.pA CO::::g + ..I.G 11 1N.Y1./1..0.1T..u.... . H1 i..a %6C\..7 .NYW1 I].\.1...._L111IC..I O6TCO_ /°f-L7-=-O7-C-7-1!7-l-7__,\ re=2C . I l 1111 1.1.-.:. l 1 1111 -, :,,110 _.. r 1,...11.: 1 \.^.T\.PA içi "% '^.../.'. :=¡.1 1f7.í¡YI ..- r.1": ./%/%//%J!94Y/ilI61M1rIï/M6Y5%/%K9%\E%i%i%i:t%Ï%/./.47-'-/iJii.-/wl//(/.;Jr ;\R41ñ..rr%%L ¡"iiA//K 4%6!/2Y76' ..tN /%%///%LO97%I9YU%(Nh9 %/7/(6%/%9%61 r- ://N % 9Y/%/%/ /r/L////// %!HF/N % %//%/9%9//%/%6.i/%69%// NN. %///r%r7//re/bYA//GfN/60%JY6Y/9/969676%67r/'./i%6/.i/9/9Ai6%J915//6%6/r/j1//%//6 JiWore ./H/I%0e6765%6Y%Jl6fr%6%r/%6%9/%/1JR//J2!/L//1/J%6%/7/9676%//./%/767/%6%/h7/69%/Ì/AIi .N/ OL16 0%4 iiY/dYySIyA7///rp%h%r//1162/6%J%i%r6%J%9Z9/Ó/RI%/Z/r/E//L6%N//6%7/7/96%69A6719%6%6%069/9699YÉi[1M¡ya iutfgMsGlgCiy.%/L v/.rtr ;iZ 0o 600 900 Zoo - ]'eo 1600 1100 11'00 Ilea O STRNCE FROM TRRNSM/T TER S.TETCH r Fig. 1. The curve in the sketch above gives an approximate idea of the relative sensitivity of several very general types of receivers. The line sloping from left to right indicates the gradual decrease of signal intensity of a transmitting station of a given power at various distances from the source. 16 RADIO AGE for August, 1925 The Magazine of the Hour

IN VIEW of the above mentioned +..a.... , electric light socket, vibrating battery facts, it would be useless to build a :t.: :u' charger, electric furnace, tree branches receiver of greater sensitivity than the rubbing against a power line or induc- one which was last mentioned. Adding :%.w-T...CI 'L},.rJ7ll__'^ ' _tLi -r.,tsc'_ tion from any motor driven apparatus additional intermediate frequency am- L such as a washing machine or electric plification or preceding a good super- ti ` dish washer, etc. Violet ray machines heterodyne with a radio frequency am- - r;t rasra. and "X"-ray devices also are a common plifier would only serve to complicate :r't source of interference. matters. Future development in radio F The factor of atmospheric disturb- receivers will probably be along the lines i ance is a universal one, but varies during tccrr_ 1 of increasing selectivity so that one may certain parts of the day and is more 7C11 pick desired from others .¡s out any station prevalent in summer in i.Nl. . p than winter. . i, . which may be operating at approximately ti d . ii; "revr4:tí fa. -..: It is commonly known that reception the same wavelength. There will also be -. over great distances is made difficult, an endeavor to simplify this type of Fig. 2. I is evident that the number of if not entirely impossible during the sum- receiver so that the same degree of sensi- stations w'ehin the range of a .-eceiving set mer months because of atmospheric tivity and selectivity may be had with is increased as the square of the se. is' .ivity, so disturbances. It has also been demon- less equipment and consequently less selectivity becomes increasingly important strated that reception is greatly enhanced cause for trouble. as the threshold value is lowered. The on a clear, cold night. A brief sketch above illustrates considera- By referring to the above mentioned this point. tion of the electrical constitution of the curve, it may be of interest to note that atmosphere is necessary in order to clear- the signal intensity decreases as the first of the loop receiver is not its portability ly understand the phenomenon known as power for distances up to 200 miles; for or ease of erection, but rather in the direc- static. distances greater than this the signals tional qualities which enable one to en- The atmosphere contains a distributed will decrease according to an exponential tirely separate two stations operating positive charge, which, as a whole, ap- and inverse first power law. These laws on the same wavelength if they are lo- proximately equals the permanent nega- are more nearly accurate when the trans- cated at righ angles to each other with tive of the earth. Franklin proved that mission is over water because water is respect to the lo_ation of the receiver. there was a difference of potential be- better conductor than the earth. Since there is no reasonable limit to tl. e tween the earth and the atmosphere We are often startled when we are possible degree of sensitivity of a well de- when he succeeded in drawing a spark able to receive a station at some consid- signed superheterodyne, one would natur- from the cord which was holding his erable distance with comparative ease, ally come to the coiclusion that there is kite. The regular increase in voltage but experience difficulty in receiving no limit to the range of a receiving system between the earth and the air at various a more powerful station which is not so of this nature. However natural this sup- heights is called the potential gradient. distant. The cause of this dead spot or position may be, it is erroneous, since The vertical potential gradient varies semi -dead spot is usually found to be the principal limiting factor of radio between thirty volts per foot at the some absorbing or deflecting medium reception is the amount of noise which is earth's surface and one volt per foot at between the transmitting and receiving always prevalent in the atmosphere, the height of six miles. This condition station. The most common causes of _ regardless of whether it is made by natur- of the air is generally conceded to be due these dead spots are ore deposits, moun- al sources, power lines or electrical to ionisation of the gases which compose tain ranges, heavily wooded tracts of devices. The causes contributing to the earth's atmosphere, by cathode land, or groups of steel buildings. Any this phenomenon of noise level are rays or other corpuscles from the sun very large substance which is a conductor numerous, but may be divided into two and radio- active constituents of the of electricity may cause this effect. general classes, namely, "man -made earth's crust. The process of ioniza- By referring to the chart, it is evident interference" and "atmospheric disturb- tion consists of breaking up the atoms that station "B which is 2100 miles ance." which constitute these atmospheric gases. from the receiver, is to be received with If one is located in the city, the factor When an atom is broken up into its con- much greater ease than station "A" of man -made interference becomes very stituents, the result is a positive charge of which is only 1700 miles from the receiv- serious. This disturbance may be due electricity and a number of negative er, because the line of signal intensity to any arc or spark such as would be charges or electrons. has been caused +to follow the dotted produced by a faulty connection in an How Iona Recombine line of the curve by some conducting object which is responsible for this atten- AS THE relative position between the earth and the sun changes, it is evi- uation. uac With the advent of the more sentitive 1'II dent that the extent of ionisation will vary

.. . receivers, many other limiting factors .. .1 ...:1 IiIÜ.' .NA.E Ynt : to a considerable extent. In other words, .. . ¡ II have been realized. The most common ;:: the ions recombine rapidly as soon as the si. üvi force which caused this condition has hindrance to good reception is "lack of ¡';i!; ,r 'I . selectivity." It is evident that the üili'!il; ._ ceased. This de- ionisation or recombin- 11 ;I¡ '. !:! ing of the ions to form gas atoms will number of stations within the range of a ¡ I'I i :il ¡l'iN change the amount of electrical charge ¡ - receiving set is increased as the square *I ; of the sensitivity; therefore, selectivity .AR_ « in the air. It is the change in amount of ¡I ; I :-1-v1' n' electrical charge, or change of potential becomes increasingly important as the .':i1111 t 11 'I II CA ' gradient, which causes the electrical dis- threshold value is lowered. This fact is :I:LI'ili,, h 11IIl'11 ': Li Ilt¡ illustrated graphically in sketch 2. How- turbance or noises in the radio receiving set which are commonly known among ever, this factor has been greatly di- Ill i!I minished, if not entirely overcome,-by . II radio operators as "grinders." These wIII I the superheterodyne type of receiver grinders travel over great distances and which permits a very marked degree of Ilij Ìlii are more noticeable at night just after selectivity. i+q EfiliHlFlIUNIIÍ111i1' h sunset, because it is then that the pro- n t . .r.,, ',tt cess of de- ionisation is at its height. The +FWtvi u,.i.i''r' mrwW i.e! '. , by The Super and the Loop t.*ser: .Jfev r?rt 1 potential gradient may also be varied r.r.,c t{nuc.1 u r, .fiJ: .. : I vertical air currents, which are caused : il :i: . THE super -heterodyne receiver has Li: Li1; by the sun's rays heating and expanding another advantage: that of being the upper layers of the atmosphere. highly efficient when used with a loop Fig. 3. This sketch shows how both direct and reflected During the summer months, when the antenna, whereas most of the other waves travel from the transmitter to the receiver. The reflected wave sun is relatively close to the earth, the types of receivers require an outdoor travels much farther extreme heat will cause the air to shift antenna to realize than the direct wave any great degree and is:therefore subject to being out of phase vertically as already explained, thereby gf sensitivity. The greatest advantage with the latter wave. (Turn to page 05) RADIO AGE for August, 192; The Magazine of the Hour 17 Some Radio Luminaries and Why

Dr:.6e Stu ho Photo. Clurego WHO hasn't heard the McCormack -like voice of Sandy Meek trilling from the antennae of prominent Middle - Western radio stations, Very few, we'll wager, for Sandy has covered a lot of ground lately, specializing in Scottish and popular ditties from WBBM, WHT and WQJ, Chicago, also having appeared on RADIO AGE programs at KYW. The demure miss at the right, in case you aren't a movie fan, is Miss Carol Dempster, leading lady of the D. W. Griffith stock company. She told of some of her harrowing experiences lately when she appeared before the "mike" at WBCQ, the Grebe station at Richmond Hill, L I.

Incl. Photo

WALTER WIL- SON, "Uncle Bob, "the kiddies'bed- time idol at KYW, is shown spending a good part of his time in the admirable occupation of teaching school children the doctrine of "The Curb is the Limit, so stay off the streets." He has signed up more than 50,000 children in his campaign. His goal is 100,000. More power to you, Walter, 18 RADIO AGE for August, 1925 The Magazine of the Hour Radio Age Announces A PRIZE CO\TKST For the Readers of This Magazine and Particularly the Followers of the Pickups and Hookups Department; Awards to be Made Monthly to Lucky Winners!

WHEN all the radio set build- The second prize will be a year's incidentally, if you will stop to con- ers are busily engaged in subscription to RADIO AGE for the sider, it is the only art in existence making up the world beater reader sending in the second largest in which there are so many devotees for the Winter session of DX chas- number of subscriptions, and for the scattered over the four corners of ing, or substituting quality for third prize a six months' subscrip- the globe, all intent upon making quantity for the benefit of the tion to RADIO AGE will be some discovery or improvement that family, it behooves this department awarded. If you are already a sub- will not only reflect credit upon the to get busy with a matter that is of scriber your subscription will be worker, but simplify the game for interest both to us and the readers. extended for the period of the prize the benefit of the millions now This matter is the subscription list you win. interested in it. of the magazine. A Fertile Field A Worthy Project Idly gazing over our subscription list the other day, we observed some MANY of you have countless FOR that reason we believe the very strange things. For instance, friends who are readers and yet Pickups and Hookups readers we have least subscribers in Miss- not subscribers of RADIO AGE. will be interested not only in making issippi and New Mexico. There This is a very fertile territory for you a fight to win the monthly prizes, might be a reason for a paucity of to work. Another is the occasional but will as well be glad to increase subscribers in Mississippi, for we reader of the magazine upon whom the number of subscribers to the can well remember as far back as you can exert your wiles. The ladies magazine and thus increase the 1912 when that state always was a are not exempt from the attraction family circle. More subscribers mean hard one for radio, for what reason of RADIO AGE, as you have ob- more readers of this department; we do not know, but assume on ac- served from the many letters they more readers mean more contribu- count of the "delta static" which have sent in. tions; more contributions mean more many of the old timers will remember. Despite the fact RADIO AGE has data and information for you, and Whether this same reason could a very flattering news -stand sale, more information for you means be ascribed for the poor showing in nevertheless it seems to us that we your quicker advancement in the New Mexico is not known. We do would become much more like a game. So it is something worth not believe these conditions should family circle if the number of annual while for you to strive for both from be allowed to govern, and with this subscribers were increased. So many the remuneration involved and the and other figures in mind, we are times, through one reason oranother, mental satisfaction in learning more starting a subscription contest for you will fail to get your copy of the and more of the most interesting the benefit of the Pickups and Hook- paper at a news -stand, whereas by study in the world. ups readers (and of course all RADIO being a subscriber you can always And the holders of the D. T. but- AGE readers.) count on having the postman deliver tons who have striven for distance your favorite radio magazine to and succeeded should now have an Monthly Prizes your home or office once a month. added incentive in doing what they THE contest will take the form can to spread out the scope of their A Family Affair of monthly prizes given for the favorite journal, which is even now RADIO AGE reader who sends in WHILE the contest is intended read on the two continents and the greatest number of subscriptions for all readers of RADIO AGE, many of the island countries of the for a given month. The contest is at the same time it is believed that world. to be started during the month of our Pickups and Hookups readers On your toes, readers of this de- August. Thereadergetsthis RADIO are the ones most interested in the partment, and let's see what you AGE by the 15th of July and will award of prizes, since they belong can do! First prize, the .0005 mfd be in position to compete for the to that indefatigable band of ex- ultra -low loss variable; second prize, August prizes. perimenters who are never content a year's subscription to your maga- First prize for the. RADIO AGE to let radio stagnate, but who by zine; third prize, a six months' sub- reader sending in the greatest num- their innate curiosity are forever led scription. These prizes are for the ber of paid up subscriptions to the into trying this and that combina- men and women who send in the magazine during the month of tion of circuits; of tinkering to see greatest number of paid up sub- August will be a .0005 mfd ultra- what makes the thing tick. All of scribers to RADIO AGE during the low loss variable condenser. You this labor, some mental and some month of August. Returns must be have probably seen it pictured on physical, is contributing toward in by the last day of August so we many occasions in the advertising the advancement of the art; for can make prompt award of the pages of RADIO AGE. after all, it is truly an art. And, prizes. RADIO AGE for August, 1925 The Magazine of the Hour 19

'i \ - -''7 Piaps °$ °` : IookupS r ,.- ó our leaders ` material appearing undcr the title "Pickups and Hookups by Our Readers" in RADIO AGE, is THEcontributed by our readers. It is a department wherein our readers exchange views on various circuits and the construction and operation thereof. Many times our readers disagree on technical points, and it should be understood that RADIO AGE is not responsible for the views presented berein by contributors, but publishes the letters and drawings merely as a means of permitting the fens to know what the other fellow is doing and thinking.

MANY ITEMS of interest will be found in this department for August, on account of the in- CONTRIBUTORS dustry of our contributors. The Summer Name Address City months are unquestionably the ones R. A. Ganatt_ 17 Lome Road, London _.N 4 England. when all the revamping of sets should be George B. Hostetter._-- Box 325._...-_- ...... _...... _. ...Freewater, Ore. , accomplished and any new ideas tried Francis Dickie. Heriot Bay__ B. C. Canada out, so the final set will be in excellent P. E. Chapman.-_--__-__805 N. Preston St West Philadelphia, Pa. condition for the Winter months. R. E. Cox.___. Douglas Shoe Co---_--...... _ _Brockton, Mass. Several of our readers have written in A. E. Hodson.____...... _.139 Rawson St., Farnsworth, asking for a method of drilling glass S. E. Lancashire, England panels. While it is a ticklish job, it can be done. The safest way is to have a DIAL TWISTERS wooden template to fit over the glass Leland Steele_ ._...... _...122 South White St__ Grand Island, Neb. panel, with holes bored in the wood for Harold Adams__ _.Evans, Colo. the positions you want them to occupy B. R. Cadman___ 3096 Bacon Road______Berketey, Mich. on the glass. Then take a rat -tail file and Shirley L. Travis_ 50 West Genesee St___ Hornell, N. Y. on an emery wheel grind one end down Charles Hrdlicka_ Kimball, South Dakota to a chisel edge. Then insert it in a Rhea Pearce____ 69 Vedado Way._ Atlanta, Ga. hand brace (not the egg beater type of W. J. Sergent, Jr. 25 Spellow Lane, Walton Liverpool, England hand drill, but the brace and bit type). Charles A. Wilson._ 2674 Burling St Chicago, Ill. Put a little three -in -one oil or turpen- Robert A. Fulton_.___._ ...... - -.... -.- Viroqua, Wis. tine on the place to be drilled, and start Harold Beaman_.._...:. ..95 Sherwood St Ottawa, Ont., Canada drilling. It is somewhat of a laborious W. M. Patterson___ 1003 Indiana Ave.____ Monaca, Pa. process, but if you must have glass Hans G. Hirsch.__ P. O. Box 993.___ Havana, Cuba panels, you must pay the price in man- William Motyle__..._ 1320 N. 14th St East St. Louis, Ill. ual labor. The wooden template serves to keep the drill from slipping sideways. Torofd Coils outfit is given for the benefit of our read- ceivers built in the mind which were Our request for data from those who ers. given space in radio periodicals. However, build the toroid coils has have tried to Real DX Work such a practice has only served to make not been in vain, for we hardly had us more firm in our determination not to uttered the request when George B. Recently we spoke of the long distance publish anything that has not been Hostetter, Box 225, Freewater, Oregon, achievement of E. H. Scott, who heard all built, tested and found effective for the came to the rescue of our readers with manner of American signals from Tas- purpose for which it is intended. two pictures and a descriptive article man, Nelson, New Zealand. In connec- of how he made his toroid coils, which tion with this matter we note that Dial Twister P. E. Chapman, 805 article we are including in this month's KFRU, owned by the Etherical Radio North Preston St., West Philadelphia, department. Co., at Bristow, Okla., considers this Pa., who is greatly interested in the One of our traveling readers has sent in reception the longest distance from which application of portables to a canoe, has pictures of his portable set. R. E. Cox's "The Voice of Oklahome" has been re- written us telling of his scheme of corn - contribution will also be found in this ported, according to a letter received in bining pleasure on the water with radio. section. our office from Roy C. Griffins, the direc- He uses a standard variometer hooked Naturally enough, many of the poten- tor of that station. up after the fashion of the ultra -audion tial DT button aspirants will not be RADIO AGE is always glad to receive with two stages of amplification. Using quite as active during this month unless letters like the following from Rhea "199" tubes, he finds this set weighs little they confine their activities to the sta- Pearce, 69 Vedoda Way, Atlanta, Ga., and occupies a very small space in the tions heard on a portable while on their for we are then sure we are on the right canoe. With a six foot piece of copper vacation. It would not be surprising if track as regards things that interest and wire (bare) dangling in the water and we had just a few of the button seekers satisfy our readers. After sending in his without an antenna, Mr. Chapman this month, but we know they will be remittance for another year's subscrip- finds this set will give loud speaker back with full force within the next tion to the magazine, Mr. Pearce says: volume on local stations in Philadelphia month or so when the weather begins "I think RADIO AGE is the best so the music can be enjoyed on the lake. getting back to normal as far as radio is on radio I've seen. Your hookups are His set was assembled at a cost of $16.83 concerned. good and I've built sets by a lot of them and a diagram of the circuit is shown From Francis Dickie, Heriot Bay, and they always work." The last three elsewhere in this department. The British Columbia, Canada, we have a words are most appreciated because we assembly is left to the individual needs picture of a radio -tester; a little device have always tried to adhere to a policy of the builder. well known to the craft for use in testing of not giving space to sets which have for "opens" in coils and other purposes. only been constructed in the mind. We Charles Hrdlicka, Kimball, South A picture and a short description of the could tell you a lot of things about re- Dakota, has epitomized the experience 20 RADIO AGE for August, 1925 The Magazine of the Hour of all radio fans in the words with at 122 S. White St., Grand Island, Neb., sets and parts has occurred during the which he describes his receiver. He says, is Leland Steele, who sends in a dandy past few weeks. This seems unusual, "1 attribute the success of the receiver list of stations. He is another of the in view of the Summer months, but it is a to the fact that high class material is RADIO AGE addicts who tells us that fact, nevertheless. Multi -tube sets, sup- employed throughout." every set he has made from blueprints er -hers, neutrodynes and the like are There is no question that the best is in our magazine works, and works fine. commanding the attention of the British none too good for our modern receivers Another DT added to the ever increasing amateurs. The fans are feeling ashamed when we strain to make each tube and family of distance hounds. of themselves, and on the quiet are say- its associated parts do its full duty. ing, 'I'm not going to let my American Mr. Hrdlicka is using a five tube Weagant- From across the pond our English cousins put it over me.' " Reinartz described in the May RADIO cousins have furnished us a bit of news, And finally Mr. Ganatt gives us warn- AGE, with the last two tubes arranged which is very interesting. The writer ing that the movement is bound to suc- push -pull for quality. His list of sta- is R. A. Ganatt, 17 Lome Road, London ceed, and for us to be on our guard, tions automatically gives him the coveted N. 4, who tells us of the great British for the British say they refuse to be a button. DX movement. Knowing that our read- bunch of "radio boobs" any more. ers are keenly alive to the quickening of There is no question but the continen- . Shirley L. Travis, 50 West Genesee St., the radio pulse abroad, we are printing tal attitude in high places towards radio Hornell, N. Y., sends in an interesting Mr. Ganatt's communication in full. has resulted in keeping down the en- list of stations picked on a receiver of the It follows: thusiasm of the radio public, but once factory built type, which list also entitles "There is a great DX movement feeling their oats, there is no reason why him to entrance into the family of Dial amongst the British fans for the Summer the millions of listeners in the British Twisters. months, and already many ambitious Isles should not take matters into their plans have been made. At last the own hands and bring about conditions B. R. Cadman, 3096 Bacon Road, British radio fan is feeling how much he parallel to those in existence in the Berkeley, Mich., informs us of the suc- is missing by not putting more enthus- United States, provided they desire that cess he has had with the set he con- iasm into radio. Up to the present kind of conditions. More power to our structed from an article in RADIO it has been a half- hearted attempt, but British experimenters and DX seekers. AGE, in May, 1924. He says he has now things are beginning to move. made a number of sets since that time, "Capt. Eckersley has aroused all self - Speaking of conditions in England, we but always goes back to his first love for respecting fans in talks given from Lon- have a letter from A. E. Hodson, 139 distance work, which is a converted don, and he gives the impression that Rawson St., Farnsworth, S. E. Lanca- single circuit with two stages of audio. only about five people in every hundred shire, England, reporting his reception of We are glad to see that Mr. Cadman who listen want to get DX. This is KDKA, WGY, WBZ and CKAC, to- believes in converting the single circuit, absurd. Britain wants to listen in more gether with a number of continental sta- for we know of thousands who are often than she ever did to American and foreign tions. He sends in a hookup very popular of the same opinion, especially on the broadcasting, and she is now putting her with the British fans, which is printed nights when lean signals and fat regenera- shoulder to the wheel and before long she at the bottom of this page. tive whistles do not mix well. His will get what she wants. efforts in tuning also merit DT recogni- "The spirit of enthusiasm is getting Some of our radio friends are terrified tion, so Mr. Cadman getsthe little button. hold of the British bug properly, and he at the prospect of the combine using feels himself endowed with greater some sort of a hashing machine to make Harold Adams, who lives at Evans, strength toward this effort. This trans- broadcast music unreadable except to Col., sends in a list of Eastern and formation has been in force only for a those owning a receiver put out by the Western stations that permits him to week or two, and already its effects are radio trust. This subject has had some become a member of the dial twisting being felt. Heretofore the British fan attention from contemporary radio maga- fraternity. He does not state his type did not go in for anything like DX and zines, but so far the matter does not of receiver, but he has the stations to was content to listen to the only programs seem to be as terrifying as it sounds. show for it, so it must be all right. available, and these local ones at that. Within thirty days after the first hashing "Manufacturers and dealers agree machine goes to work, its circuit and Another ultra -audion fiend who lives that an unprecedented rush for radio constants would be known and within

This is the general type of tuned radio, detector and one stage of audio amplification in use in the British Isles. It is sent in by A. E. Hodson, 139 Rawson St., Farnsworth, S. E. Lancashire, England. RADIO AGE for August, 192." The Magazine of the Hour 21 another thirty days a goodly number of experimenters would have receivers of their own rigged up. From that point it is easy to see that such a scheme of broadcasting only for the benefit of the privileged few will hardly ever come to pass. There is hardly a thing that has been invented that has not had something come along later to either improve it or nullify its usefulness. And the prospect of piping music into the home, which was done as early as 1912, might seem rosy at first blush, but a little sober reflection will produce the thought that the one tie that binds in radio is the ability of the set owner to pick programs at will, and not have them thrust upon him willy-nilly. So it does not seem there will be much of a change in the status of broadcasting. Those who de-. rive an advertising benefit from the transmitters can hardly expect the public to contribute, when, after all, the amount of money tied up in receivers and allied apparatus probably overshadows by a great deal the total involved in the ownership and operation of broadcast Fig. 2. A neat and efficient means of testing for breaks in wiring of sets, which can be transmitters. applied to almost any use in determining the continuity of wiring in coils, transformers, phones, and other apparatus. The circuit shown in Fig. 1 can be made up with honeycombs for covering a wider span of wavelengths than the Box 325, Freewater, Oregon, who tells an inch wide and bend it into a ring broadcast band. Otherwise it can be readers of this department how to make whose outside diameter is exactly equal made up in the low loss type of winding. the toroid coils for use in radio frequency to the length of the secondary coil The detector is regenerative. This type sets. The process is as follows: measured on the tape. Cut two circles of of circuit is in use in the British Isles on Procure a cardboard tube one and a heavy cardboard two and a half inches in account of regulations preventing a quarter inches in diameter and about diameter. Glue the ring to these disks, regenerative set coupled to an antenna. nine or ten inches long. This is shown forming a spool as shown in the upper Some of our English friends tell us in at G in the photograph, Fig. 3. On this part of Fig. 3. letters that despite the ban against wind a layer of ordinary twine string (B in With a piece of adhesive tape fasten regenerative sets there are a multitude photograph) fastening the end with one end of the coil to the spool, bring of squeals to be heard over there. This a tiny piece of adhesive tape, A. Over the other end of the coil around until is the set with which Mr. Hodson heard this fasten a thickness of writing paper. the ends fasten together with another KDKA, WGY, WBZ and CKAC, to- Get a roll of half inch adhesive tape and piece of tape, working between the turns gether with a bunch of broadcasting cut off a piece about 21 inches long. of the coil, which may be straightened stations on the Continent. Split each end of this piece for a distance back into place after the ends have been of about seven or eight inches. Lay the secured. You will now have a coil as William J. Sergent, Jr., 25 Spellow tape length -wise on the tube, sticky shown in Fig. 4. The leads may be Lane, Walton, Liverpool, England, sends side out, pushing the split edges into brought out through holes punched in in a DX list that certainly gives him the the ends of the tube out of the way. the disks as shown. These coils may be button. He also heard KDKA, WGY Now wind on 225 turns of No. 24 SCC used in any tuned radio frequency and WBZ using a four tube set, one wire, D and DI in the picture, securing circuit. They eliminate special placement radio, detector and two audio, built the ends by punching a hole in the tape. of coils or the use of stabilizing devices. along the lines as Mr. Hodson's shown in Lay one of the quarter -inch pieces of Fig. 1. He also uses a one tube receiver tape back over the coil and the opposite Another traveling man, this time R. E. with two stages of audio and on it does quarter -inch piece on the other end of the Cox, who travels for the \V. L. Douglas most of his DX work. He is particularly coil, so as to form a strip a half inch Shoe Co., Brockton, Mass., and who desirous of getting an extremely selective wide over the top of the coil. writes from Coldwater, Mich., shows us set using four tubes. Maybe some of our About a quarter of an inch from the end how it is possible to always be in touch Pickups readers can give him a circuit of this winding, start the primary, wind- with the world by means of a portable that will do hair- breadth tuning. ing four turns of the same wire (El). which he carries with him on all his Do not break the wire, but run it along trips. The device shown in Fig. 2 is a radio- the tape for two and a half inches, then In Figure 5 is shown the receiver, tester, manufactured by the British wind four turns more (E2), run along which uses the circuit around which Industries Association, 317 High Hol- the tape again for two and a half inches, Browning -Drake have developed a re- born, London, W. C. I. It consists of a and wind four more turns (E3). This ceiver, while Figure 6 shows the self dry cell, a small lamp and a series con- makes twelve turns in all for the primary. contained set being carried by Mr. Cox, nection arranged so that continuity Each coil of four turns should be held whose northern extremities were not of wiring may be tested in inductances, temporarily in place with a small piece shown, since he was more desirous of transformers, phones, rheostats, poten- of adhesive tape. showing us the set than himself. Mr. tiometers; it can also be arranged to test Now take the two other pieces of Cox tells us the set has four tubes, the condensers. A similar device in the quarter inch tape and stick them tightly fifth being in parallel with the fourth. workshop of the experimenter will save a in place over the primary as at (F). He gets excellent results and is strong lot of trouble in testing. The illustra- Pull the tape (A) loose and unwind the for RADIO AGE. tion is sent in by Francis Dickie, Heriot string, pulling it out the end. This will For essentially local work in a canoe, Bay, British Columbia, Canada. allow the coil to slip off the tube very where weight is a consideration, the set easily. Then the layer of writing paper shown in Fig. 7, contributed by Mr. Previous mention has been made of may be removed. Chapman, might be of interest to readers the contribution of George B. Hostetter, Cut a piece of light- weight cardboard with aquatic proclivities in the Summer- 22 RADIO AGE for August, 1925 The Magazine of the Hour time. A six foot piece of bare wire U. S. Bureau of Standards. Copies of serves as the ground. Locals come in this paper may be secured from the well on a loud speaker and help con- Superintendent of Documents, Govern- siderably while out on the lake. ment Printing Office, Washington, D. C., for 5 cents. Charles A. Wilson, 2674 Burling St., Chicago, Ill., went DX hunting on the The conductor of this column is taking night of March 29, and came forth with no chances of your failing to read about a very interesting radio scalp, that of the subscription contest, which 4YA, has been the broadcasting station of the started by Radio Age and accordingly British Electric and Engineering Co., calls your attention to the full details 219 Moray Place, Dunedin, New Zea- on page 18 of this number. Dial Twisters land. To make sure there would be no are especially invited to take part in the mistake, Mr. Wilson communicated with contest because of the nature of the the company and received due verifica- prizes and because of the fact that read- of the tion reception. While it has be- ers of this department are the ones most come rather commonplace for the New interested in the creation of a larger Zealanders to hear our American sta- Radio Age family which will naturally tions, it is nevertheless somewhat of a be followed by much more interesting fete for the reception to be in the oppo- data in these columns. site direction. Both Mr. Wilson and the broadcasting station in New Zealand have The a. c. tubes, which being given reason to feel proud of their achievement. are consideration in this issue in an article by Turner, should Robert A. Fulton, of Viroqua, Wis., Fig. 4. Here is shown the toroid as it looks command the attention of our fans. Probably who, incidentally, is only eleven years when completed. A careful study of the more research accompanying description will show you is still necessary with these tubes, but old, has qualified for a D. T. button with how to do it nicely. nevertheless they seem to point the way the list of stations he sends in, all of to the battery -less set of the future. which have been heard on a home -made See what you can do with them typically regenerative set. tactics of the Octopus, William Motyl, and let 1320 North 14th St., East St. Louis, Ill., us have the dope. Using a two tube ultra -audion de- furnishes us with a DX list of stations scribed in the March RADIO AGE, heard on the regenerative reflex described Dial Twisters may be interested in Harold Beaman, 95 Sherwood St., Otta- in the March blueprint section. Mr. knowing that WGY may now be found wa, Ont., Canada, brought in a total of Motyl used a variometer with an aper- on four wave channels, according to a 79 stations from the Atlantic to the iodic primary instead of the r. f. trans- recent announcement. These follow: Pacific and earned for himself an en- former and a variable to tune the r. f. WGY 379.5 meters; 2XAF 38 meters; blem of the dial twisting fraternity. transfomer proper, these two additions 2XK 109 meters and 2XAH 1660 meters. helping out to a considerable extent on The last three groups of call letters are W. M. Patterson, 1003 Indiana Ave., DX. Another member added to the dial special experimental licenses of the Monaca, Pa., who seems to be a mem- twisting family. General Electric. The purpose of the ber of the A. R. R. L., sends us a list of four channels is for research work by his DX results on a single tuber which Those interested in insulating materials the company's engineers on transmis- allows him to bring home the bacon in may find data of interest in the techno- sion problems under all conditions; the form of the button. His list of 83 logical paper No. 284, "A Study of the day and night, summer and winter. stations includes a number of amateur seasonal variation of the r. f. phase Radio fans who are equipped to receive phone stations. difference of laminated phenolic insulat- on the four wavelengths are invited to ing materials" by J. L. Preston and report to the engineers the quality, The conductor of this column has been E. L. Hall, which has been issued by the (Turn to page 86) accused of many things in his career but never yet has he qualified as a mind reader. The reason for the foregoing is the receipt of a letter from a radio enthusiast whose address is Route C, Box 141, Frederick, Oklahoma. The correspondent neglected to sign his name to the letter, and as a consequence we have a Dial Twister's button issued to an address instead of an individual. If the resident of the address given above will communicate with us, we shall be glad to send him the button which he has merited through the DX list sent in.

Making up a "Baby Het" from specifications in RADIO AGE and adding a stage of audio for increased volume, Hans G. Hirsch, P. O. Box 993, Havana, Cuba, is having the time of his life logging them from coast to coast. His list is a fine one, especially when many of our readers imagine that residents of the Gulf section are continually fighting static: We will give him the button as an indication that static does not mean much in the existence of a real distance seeker. Fig. Patting our Editor 3. The picture above shows the toroid cod wound on a straight form, preparatory on the back for his to its being bent in the form of resolute stand against a doughnut. The form shown at the top is that used in the insidious the final assembly of the coil. RADIO AGE for August, 1925 The Magazine of the Hour 23

Radio Age Offers the First Real Presentation of Basic Hookups in. "De Luxe Edition" Conducted by F. A. Hill blueprints shown herein, we are giving In the blueprint section this month IN putting forth the August number the basic circuit and a brief comment as readers will find a number of the conven- of RADIO AGE, its publishers have to its history and its adaptability for tional symbols which have been drawn up simply acceded to the demand on the experimentation. Perhaps later experi- by Mr. Rathbun and which should prove part of radio fans for the basic hookups mentation with some of the circuits has of interest to the fans who are beginning to from which the various radio circuits shown improvements can be made by learn the intricacies of the game. have been developed, without a ple- slight deviations from the plans. Where Readers following this section closely thora of misleading terms attached to an such is the case, due mention will be made will see all of the basic, hookups from old circuit and put out under a fancy of the changes and the reason for such which the many forms of circuits are sounding name. The radio fan has come changes. developed. Any one of the circuits can to the stage in this interesting science With the August number of RADIO be twisted around in different ways as where he courts and welcomes frankness, AGE in his possession, the radio fan is far as the material is concerned, but the and it is the purpose of RADIO AGE to in a position to start work on the simplest electrical characteristics will not change. give the reader such frankness in its to the most complex radio set, since The substitution of variometers for tun- columns. nearly every form of set is shown basic- ing the plate circuit of a tube instead of an In looking over the crystal circuits ally; the experimenter only has to use his inductance and a condenser does not shown by Mr. Rathbun on page 30 of this ingenuity in making up sets embodying change the set from a regenerative set section, you will find all the possible elaborations or amplifications of the into something else. And so on down means of hooking up a crystal set. These basic data given. through the list. forms have been tried out by the Bureau The popularity of the blueprint sec- In thinking over the various items of Standards and measurements made to tion of the Radio Age each month can which the experimenter will require in enable the radio fan to determine which best be understood by the flood of letters the assembly of the various circuits, type he desires. The relative audibilities from fans desiring to build the sets de- very careful consideration should be shown will soon show the interested fan scribed, and also from the satisfied set given to the use of good material. There which type of hookup he wishes to use. builders who report their success with the has never been any question of the fact Yet many of the forms shown here have receivers. that good material will make a set where found their way into the market under The correspondence seems to be pretty poor material will ruin it. See that your "high -faluting" names, some of the indi- well divided over the entire country, condensers and inductances are made by viduals even going so far as to claim the including Canada. Foreign countries reliable manufacturers. Look over the invention of this or that particular also furnish a pretty good volume of socket market and pick out one of the crystal circuit. Such practices as out- letters, all testifying to the popularity type that will give you positive contact lined are not countenanced either by the of the blueprint instructions as contrasted on all the prongs. readers or the publishers of a good radio to the conventional black and white The grid leaks should especially be magazine. This is only one of the many drawings. scrutinized for in the grid leak lies a great reasons for our publication of this In following the blue prints experi- deal of the trouble of the set builders. wonderful DeLuxe Edition. menters should always remember that It might pay to buy two or three leaks of Another of the reasons for its appear- for electrical connections the schematic different values just to be sure you have a ance is the fact that many experimenters diagram should be followed, since the good one. The little grid condensers have been stumped to find a basic cir- other drawings are either isometric or should also be good ones, preferably cuit when they have been assailed on all plan views of the set and are not intended with mica insulation and copper plates sides with developments, improvements, as electrical hookups. Always follow that will not alter their characteristics. additions and deletions to the standard the schematic when wiring your set and A good deal of attention can also be circuits. Insofar as it is possible in the you will not make mistakes. paid to transformers and to loud speakers. 2 RADIO AGE for August, 1925 The Magazine of the Hour A Timely Discourse on Conventional Radio Symbols and Crystal Detector Sets By JOHN B. RATHBUN CONVENTIONAL radio circuit dia- left, which may indicate the output of any radio grams, the radio, have receiving circuit. Abbreviation (PH). The polari- short -hand of ty may be marked by ( +) or minus as shown, always proved a sticker to the tyro in or this may be omitted at will. The positive con- this science, and it is certain that many a nection of the phone cords is colored red and this How to Understand red strand be to ( has a should connected the +) connec- prospective builder contracted bad tion of the circuit. At the right is the symbol for case of cold feet and quit the game when the horn or loud speaker which can also be marked he was brought face to face with the All Radio Symbols; with the polarity. - curley -cues and zig -zag lines of the tech- 7. CONDENSERS. A "fixed" condenser con- nical diagram. Not being very familiar Giving the Crystal sists of alternate sheets of tinfoil and paper or mica is no compressed into a compact pile. and adds with the apparatus itself, it wonder "capacity" to the circuit, an effect opposite to that the prospect of learning still more Its Merited Attention that of an inductance coil. The symbol for a fixed of the technique filled him with dismay. condenser is at the left where the abbreviation is how as (K) where However, when these symbols are once and the capacity in micro - farads is also added where advisable. A VARI- understood, they are more easily read transmitting station. The abbreviation is the ABLE CONDENSER used for tuning inductances and understood than the picture diagrams letter (L) and its magnitude is generally expressed i s shown at the right, where the rotor plates are in millihenries, or by the number of turns of wire. i ndicated by the curved line and the stationary or for they show the functioning and general stator plates are shown by the short straight principles of the circuits far more clearly 2. IRON CORE CHOKE. This consists of a line. great many turns of wire wound around a core of The Stator (Straight line) should go to the grid of a to the experienced eye than pictures of soft steel wire or thin steel sheets called "lamina- tube, while the rotor is connected to the ground see is used when side or ( -A) side of the circuit. This condenser the apparatus. You can the course tions." It a greater retardation must is also rated in microfarads (m. f.). taken by the current in the different be had than is convenient with an air core choke, ani can choke back audio as well as radio frequency branches of the circuit at a glance, and 8. RESISTANCES -RHEOSTATS. A fixed currents. Values in henries or millihenries. or unvarying resistance is shown by the zig -zag can immediately classify the circuit with 3. TRANSFORMER -COUPLER (Air Core line which distinguishes it from an inductance. For little chance of error; something that Type). This transformer for radio frequency I ow resistances used for controlling the filaments of I have never yet been able to do with the currents consists of two coils of wire called respec- the tubes, its magnitude is given in terms of ohms. tively the PRIMARY (PRI.), and the SECON- For very high resistances, as used for grid leaks, picture type. However, the picture DARY (SEC.) coils. Radio frequency currents the resistance is given in terms of MEGOHMS, diagram has its place in the scheme of passing through the primary induce similar cur- abbreviated (MEG). rents in the secondary coil, thus affording a means things where the reader is not interested A RHEOSTAT or variable resistance is shown some of "coupling" two circuits together magnetically. in theory, but simply in building - In our diagrams the primary coil (PRI) is shown at the right and is usually employed for controlling thing that will bring in the voice and with fewer turns than the secondary and is shown the filament current of tubes. The letter (R) is used music with the least delay and study. on the end opposite to the grid connection (G). for a rheostat, or resistance. For the benefit of those who have not The other connections are the filament (F), the 9. BATTERIES. An "A" or filament battery plate connection (P), the positive "B" battery or a "C" battery is shown by the symbol at the left yet become familiar with the standard connection (B) and the neutral tap (N) used for which consists of alternate short heavy lines and conventional symbols used in radio cir- certain neutralized circuits. The abbreviation is longer light lines. The short heavy lines indicate cuit diagrams, I have prepared the ac- (RFT), and it may be tuned or untuned, the the negative ( -) plates while the long linea are the former by a variable condenser. ( +). Each pair companying two pages of blueprints in positive plates of these lines rep- 4. VARIOMETER. This is a form of variable resents one cell, and it is the best practice to mark which the more common symbols and inductance used in place of the air core choke, and the voltage below it as at (6v.) and the letter (A), abbreviations have been defined. In ad- consists of a movable member (The Rotor) which (B) or (C) above it to designate the type of battery. A "B" battery is at right where line dition to the listing of the symbols, I turns inside of a stationary coil called the "Stator." the the dotted The abbreviation is (VAR). By this means the indicates a number of omitted cells, there being have taken up a short description of the inductive or choke effect can be varied through a too many cells in a "B" battery to draw them com- various parts used in the receiving cir- wide range without condensers and the device is plete. When the battery is tapped at some low frequently used for tuning a circuit inductively. It voltage, as at ( +22), the voltage of the tap is cuits so that the subject will be more marked in this way. easily followed. may be tapped at the mid -point as shown at (Q). S. ANTENNA- GROUND -ARRESTOR. At 10. PONTIOMETETER. This is a device which Circuit Symbols (Sheet No. 1) the right is shown the symbol for the antenna or looks much like a rheostat used for the accurate control of voltages, 1. INDUCTANCE (Air Core Type). The aerial, abbreviation (ANT). In the center is the generally the biasing voltages hollow coil of wire or other inductance coil with an symbol for a ground connection (GND), and at applied to the grid of a vacuum tube. It consists air core is shown by a continuous scroll or helix the right is the convention for a lightning arrestor of a fixed resistance of from 200 to 400 ohms con- as in Item No. 1. Its purpose is to choke back or (LA). nected across the battery and a sliding contact impede the flow of radio frequency current or for 6. OUTPUT - PHONES - SPEAKER. The which taps off the drop of potential at any point of tuning radio circuits to the wavelength of the symbol for the headset or phones is shown at the the resistance. The polarity of the slider also Blueprints of Conventional Radio Symbols and Typical Crystal Receivers on pages 28, 29, 30 and 31

UP AND AT 'EM! Perhaps some of the Dial Twisters and readers of the Pickups and Hookups Section have strayed over into these blueprint pastures in B search of choice morsels of radio information. Here's one morsel all of our readers should seek : On the page facing the Pickup and Hookup Section, you will see notice of a monthly subscription contest. For the month of August prizes are to be awarded for the reader who sends in the largest number of paid -up subscriptions to your favorite journal, RADIO AGE. We could tell you a lot more, but space is limited. Read page 18 and then go after new radio recruits. 0 i lal000©oo ® 1013o30000a322 RADIO AGE for August, 1925 The ]lagaziue of the Hour 25 vari_, with its position, hecoming negative at one (SW) being used to vary the number of understandable signals on so small an end and positive at the other. turns in circuit. amount of current that it can be esti- 11. THREE ELEMENT VACUUM TUBES. In 23 The three elements of a vacuum tuhe are the Fig. is a regenerative circuit with mated in millionths of an ampere; and filament (F), the grid (G) and the plate (P), al. one stage of audio frequency amplifica- yet, with all of this delicacy, the appara- though these parts need not be marked as shown. tion, a type of circuit, very commonly tus is perfectly simple and so rugged A "hard" amplifying tube is indicated by a single met with. is heavy circle drawn around the elements and as a The detector tube (T1) a that it can withstand a considerable hard tube is much used at present for a detector as soft tube, while the amplifier tube (T2) amount of abuse at the hands of the well as for an amplifier. When a soft detector tube is a hard tube, as will be seen from the listener. must be used, two circles are used, as at the right. circles. A To of readers who The word amplifier is abbreviated (AMPL) and coupler is used for tuning, most our have had detector by (DET). having the primary coil (Ll) and the experience only with the cheap and simple 12. TWO AND FOUR ELEMENT TUBES. n secondary coil (L2), this being used single- slide, single-circuit crystal detec- two element tuhe or Firming valve is indicated at sometimes instead of the abbreviations tor sets sold on the open market, the the right and has the filament and plate but no grid. "PRI" and "SEC." The secondary is crystal detector is considered only in the This is most generally used as a rectifier for charg. ing storage batteries from alternating current, but tuned by the variable condenser (K1). light of a toy having only a very limited is also used as a detector. The four element tube For regeneration we have the tickler coil use in reception. This, however, is not at the right has two grids. (TIC) placed directly above the second- the case, for with proper attention to the 13. GRID CONDENSER AND LEAK. This ary coil (L2) and connected with it by details of construction and with as much symbol used with detector tubes is simply a combi. nation of the symbol of a condenser and that of a means of an arrow. The arrow in this care taken with the tuning units as we resistance (The leak). The leak abbreviation is case indicates that the two coils are pay to the construction of a tube set, the (GL) and the grid condenser is (GC). If either of inductively coupled by a variable rela- performance can be greatly improved in these items is variable, then this fact is indicated by a slanting arrow across it as at the right. tion; that is, that the position of (TIC) regard to distance range and signal irawing can be varied in strength. If we constructed 14. CRYSTAL DETECTOR. A crystal detec- respect to (L2). The our tube tor is indicated by an arrow head for the cat - grid condensor (GC) and the grid leak sets with the same lack of care and with whisker and a small block for the crystal. (GL) are shown connected to the grid the same primitive tuning systems that Abbreviation is (CD). of the tube. are used on commercial crystal sets, we 15. AUDIO (IRON CORE) TRANSFORMER. Current would not get very An iron core transformer, commonly known as an for lighting the tube fila- much better perform- audio frequency transformer, is used for increasing ments is supplied by the six volt "A" ance. Single- slider, single -circuit tuners the voltages of currents approximating voice fre- battery which is connected so that the are not conducive of good results with quencies or audible frequencies. It consists of a negative pole either primary winding (PRI) and a secondary winding goes to the detector rheo- the crystal or tube detector, for (SEC) with a few parallel lines drawn between the stat (RI). The negative pole of the they cannot be tuned accurately in re- coils to indicate the iron core. The four connec- "A" battery connects with the negative sonance with the incoming waves, and tions are marked as follows: (G) for grid, (P) fcr pole of the "B" there is always a considerable loss taking plate, (F) for filament and (B) for B" battery battery, and the latter connections. These apply to vacuum tube connec- is tapped at the ( +22) volt point for the place that limits the distance and tions with which the transformer is most commonly detector current. The total voltage of volume. a are used. Iron core transformers of special type the "B" battery at ( goes to the also sometimes used on radio frequencies, but when +90) The Crystal Detector Circuit this is the case the fact will be particularly noted on last stage jack (J2). A two circuit jack the drawing. Ahbr. is (AFT). J1) permits us to plug in on the detec- OCR primitive crystal detector circuit 16. WIRING AND CONNECTIONS. In tor tube alone without amplification, or consists of three principal units: general, wiring is indicated by very heavy lines, without lighting the amplifier tube (1) The tuning unit, by which it is and curved by an arc where a turn is made. Where two wires connect, a small OPEN circle is used to (T2). Plugged in on (J2) we get the brought into resonance with the incoming mark the connection as at (a). Where one wire amplified or intensified current for the waves, (2) The crystal detector employed crosses over another, the crows -over is shown as at operation of a loud speaker. for rectifying radio frequency im- (b). Connection posts or terminals for batteries, the etc., are shown by a circle with a heavy hlack dot An iron core audio frequency trans- pulses for the development of the audio inside, as shown in a horizontal row. The letters former (AFT) transfers the plate energy waves, and (3) The audio output mechan- indicating the "A ", "B", and "C" batteries are of the detector tube (T1) to the amplifier ism which converts the audio frequency marked at the terminals, together with their polarities. In the case of the "B" battery connec- tube (T2), and it will be noted that the electrical waves into mechanical sound tions the various taps are marked by the voltages terminals of the transformer are marked vibrations (Phones). All three elements as at (+22), ( +45) and (+90), but the letter "B" in accordance with the points that they must be as perfect as possible if we are to is not used. connect. Thus (G) goes to the grid of extract the maximum[ output in the form 17. TAP SWITCHES. Tap switches used for cutting out active turns in a coil should he con- (T2), connection (P) goes to the plate of of sound, for the incoming energy is nected so that the contact points go to the grid or tube (T1), connection (B) goes to the exceedingly feeble and must be carefully aerial side of the circuit with the hinge connected ( +22) volt tap of the "B" battery, and utilized with the least possible loss. to ground or on the far side from the grid connection to prevent body capacity effect. connection (F) goes to the ( -A) through This means sharp tuning, a crystal hav- 18. INSTRUMENTS. Measuring instruments the "C" battery. A fixed condenser (h) ing excellent rectifying qualities and an such as the voltmeter (VM), the ammeter (AM) or is shunted across the secondary. A 4.5 exceedingly sensitive pair of phones, the hot wire ammeter (HWA) are shown in circles. volt "C" battery is used for biasing the none of which are in evidence in the usual The polarity should be marked, and also the range of volts or amperes at at (0-10) and (0-5). grid of the tube (T2) and the negative $2.00 crystal detector set. In reviewing pole ( 19. JACKS. Jacks are specially arranged con- -) is connected to (F) of the trans- the requirements, we must also remember tacts used for making temporary connections by former so that the current gets to the to include an efficient antenna into the means of plugs and may be of many types. At the grid of the tube through the windings. assembly, which should have greater left is shown the single circuit jack (J2) generally Tube (T2) is used for the last stage connection and at the left controlled by rheostat length and capacity than the antenna is a two circuit jack (J1) used for plugging in (R2). commonly used with tube sets. The between stages. These are by far the most common Fig. 24 is a typical reflex circuit with latter item is generally neglected in the types. the radio frequency transformer (RFT) installation of a crystal set, with the 20. SWITCHES. Different types of battery and the audio frequency result very little volume or distance switches are shown, the left symhol being for transformer that symbolic diagrams while the second from the left is (AFT), the former being tuned by the is had. Conservation of energy is a prime used frequently on picture diagrams. The switch variable condenser (K2). A coupler is requisite. at the right is a double pole knife switch used for heavy currents. provided with the primary (LI) and It is here that the low -loss coil and the secondary (L2) by which the set is tuned low -loss condenser hold forth with to wavelength. The grid bias on the particular advantage; spiderweb, honey- Sample Symbolic Drawings tube is varied by the potentiometer (PO). comb or barrel -wound coils being of The rest of the parts have been explained great advantage in the construction of ON SHEET No. 2 we show four repre- before. sentative circuit drawings which such a set. The phones should prefer - include most of the symbols tabulated. ably be of the mica diaphragm class or Each symbol is lettered with the standard Crystal Detector Sets with very thin flexible metal diaphragms abbreviation so so that the slightest current in the coils that it will not be difficult TO ME, to trace out the relation between the the crystal set has always will give a maximum vibration. When parts in the table and the corresponding seemed the most wonderful of all we look at the cheap phones ordinarily parts in the diagram. radio receivers, for with this device supplied with crystal sets, with their we employ the feeble energy of the radio thick cast -iron diaphragms and their A simple crystal detector set, tuned by waves alone to vibrate the diaphragms weak magnets, it is no wonder that the variometer (VAR) is shown in Fig. of the phones without aid or reinforce- reception is limited to 10 or 15 miles. 21. Here we have the symbols for the ment from local sources of energy. After This would be almost the case with a variometer, crystal, aerial, ground, traveling fifty miles or so, there is still tube set if it were supplied with the same phones and two fixed condensers. Note sufficient energy left in the waves to sort of phones. The feeble impulses that when two condensors are shown move a relatively stiff piece of metal and received demand the most sensitive and that they are numbered as at (IC1) and to produce the audible air vibrations efficient equipment that we can supply (K2). In Fig 22 we have another single known as sound. Further, it is an exhi- if the crystal set is to be more than a circuit crystal set tuned by a simple tapped bition of the remarkable sensitivity of mere toy for children's use. inductance (L), the tap switch the modern headset which produces Please don't infer that I am recom- 26 RADIO AGE for August, 1925 The Magazine of the Hour mending the crystal set as a substitute While the complete theory of contact Galena, silicon, carborundum, cerusite, for the tube set, for I am not. I am rectification is not yet well understood, pyrites, perikon, radiocite, and hecite are simply bringing to your attention the I will explain the functioning and purpose among the most commonly used simple fact that the crystal set performance can of the crystal in a general way so that minerals, and in addition to these are the be wonderfully improved by a little care the beginner can at least get a working numerous synthetic crystals that bear a in the construction and that it is a most knowledge of its properties when in- multitude of trade names. A good galena desirable proposition for local reception stalled in the receiving set. Mechani- crystal is probably one of the most sensi- where we do not wish to go to the trouble cally it is very simple, consisting of a tive crystals, but it is not stable and must of installing batteries and similar com- small piece of mineral called the crystal, be readjusted frequently. Silicon and plications. The crystal set has a field and a thin wire making light contact carborundum do not require so frequent all its own and is almost indispensable with the crystal at a sensitive spot. In adjustment and are quite sensitive if for certain purposes, and for this reason some cases, contact is had between two carefully selected and mounted. The I believe that more attention should be crystals instead of between the wire synthetic crystals are in most cases stable paid to the development of its perform- and crystal, but in any event the radio and sensitive, and have the advantage of ance rather than to cutting down on the frequency current must pass through a having a greater effective area or more expense of construction, as has been done high resistance contact of some sort "hot spots" than the natural crystals, so heretofore. You cannot get long distance before passing through the phones, so that it is not so difficult to adjust them. consistently, nor can you get full loud that the audio or "hearable" portion of For the catswhisker wire, we require speaker volume of the crystal alone, but the incoming waves can be developed. a metal that will not corrode under you can get locals with good volume, Owing to the rapidity with which the ordinary atmospheric conditions and one clear and sweet, without the fuss attend- radio wave oscillates back and forth, the that will maintain a bright metallic con- ing the operation of a tube receiver. diagrams of the phones cannot follow the tact area at the point where it rests on the When loud speaker volume is required radio frequency currents in the receiver crystal. A copper wire will work well on local, with particular attention to with most crystals, but a silver or gold quality, we can add one or more stages wire is better, as it does not corrode or of audio frequency amplification to the get dull as rapidly. With the exception detector. Of course, we are now getting of the carborundum crystal, the cat - back to vacuum tube complications and A ROUND -UP OF whisker wire should make very light batteries, but with very simple layouts HOOK -UPS contact with the crystal, working best we can obtain wonderful tone values on when only just barely touching the sur- the loud speaker and a somewhat in- Will Rogers would probably call face. With the carborundum detector a creased distance. Just as an experi- this August number a "Radio very heavy pressure is required, which ment, it is very interesting to add resist- Rodeo" but we have named it the in itself is one reason for the stability of ance coupled stages to a crystal detector De Luxe Edition. the carborundum, as the heavy pressure to discover what real tone purity is like. Having seen and burrowed in its prevents the displacement of the contact The natural tone and life -like quality alternate reading and blueprint when subjected to vibration. will be a revelation to you, and if you pages, you will no doubt want to There has been a great deal of 'argu- live within 25 miles or so of a broad- send a copy to one of your friends ment for and against the fixed crystal casting station, I am sure that you will who so far has resisted the lure of detector with the immovable catwhisker, keep this circuit hooked up permanently. radio. but I believe that the fixed detector will Future of the Crystal Set A very simple matter! Get an prove best in the long run for the begin- extra copy from your newsdealer ner, at least, as it avoids the necessity of CONSIDERING the many 5,000 watt and pass it on to your friend. constant readjustment and the detuning broadcasting stations now under Then watch the fun. effect when these adjustments are made. construction, and the increasing practice It will perhaps be of interest to know that of re- broadcasting, it is certain that the the crystal has a great deal of effect in crystal detector receiver will find a more OR If you must, take his $2.50 for a the tuning of the circuit and very often extended use than his been the case in we can tune a station in and out by means the past. Increased power at the stations year's subscription to the Magazine of the Hour. of the crystal adjustment alone. For the and the relaying of these stations at close experienced crystal set operator, the intervals over the country will mean that adjustable crystal is therefore often an the crystal will take on a new life. At advantage, as it is an aid to selectivity least ten telephone companies have and tuning, particularly where there are adopted local re- broadcasting systems as directly and nothing will be heard in the many strong local stations and other an additional service to their subscribers, phones if some sort of rectifier or "de- interferences. and I do not believe that the telephone tector" is not inserted into the circuit. companies will be the only people to These waves are "alternating," that is, It is a good plan to get a number of engage in this work. If the network of they flow first in one direction and then crystals and then select the best crystal re- broadcasting stations is fully developed in the other, and before we hear the sig- by actual test. There is a great deal of the use of the crystal set will be practical nals these waves must be made "uni- variation among crystals even of the same in almost any part of the United States. directional" so that they will flow in one make, and the only way that you can be One re- broadcast station equipped direction through the phones but with assured of the maximum results is to with a good receiving set and a trans- an intensity that varies according to the select the best crystal from a number of mitter of moderate power will easily sounds sent out by the broadcasting samples. cover a radius of 25 miles and will station. The crystal detector with its Hook -Up or efficiently serve crystal detectors in this contacting "catwhisker" wire acts as The Circuit 50 -mile circle. The expense of main- such a rectifier and permits the passage THERE are about a thousand different taining such a station is comparatively of only one set of waves that are flowing crystal detector hook -ups from which small and can be borne by the local in the same direction. to make a choice, and all of them have Granges or community associations with With the radio frequency current rec- their adherents, who believe that they a great saving to their members. The tified, the "audio frequency" waves are have the only circuit worth using. Some station receives the voice and music developed so that the diaphragms of the employ variometers for tuning induct- from distant stations and then broad- phones follow the slower voice frequency ances, others use spiderweb coils, vario- casts these signals through simple appa- pulsations, thus producing sound. Our couplers, honeycomb coils and straight ratus to local listeners, thus avoiding the station waves therefore consist of two solenoid coils in all sort of combinations, expense and trouble of arranging pro- components, the high radio frequency but as a matter of fact, a close examina- grams. So far, this arrangement has carrier waves oscillating at the rate of tion will show that most of these circuits increased the total number of listeners about 1,000,000 vibrations per second, can be boiled down to six distinct classes. tremendously without appreciably affect- and the audio frequency waves impressed The type of inductance does not change ing the sale of tube sets. On the contrary, on them that will range from a few hun- the characteristics of a circuit as a circuit: one re- broadcasting station states that dred to an upper limit of about 15,000 it simply adds or detracts from its effi- the interest aroused in radio via crystal vibrations per second. These latter ciency by the sharpness of its tuning sets has greatly increased the sale of tube waves are produced by varying the in- properties and the losses occuring within sets in its territory, and that a great tensity of the radio waves by "modula- the coil. A variometer may show better proportion of the listeners now have tion," and are not actually an indepen- results than a simple tuning coil, simply both crystal and tube sets in their dent series. for the reason that it can be more closely homes. Tiring of the local re- broadcasts, There are a great number of minerals adjusted to wavelength than the coil - and desiring different programs, they that will act as detectors to some extent, not because it is a variometer. An in- turn to their tube sets and tune in the but only a few that are effective enough ductance is an inductance no matter what distant stations for themselves. to be used in the practical crystal set. form it may be used. RADIO AGE for August, 1925 The Magazine of the Hour 27

Fig. 1 shows the six basic circuits with and is almost equal to that of the first been built and connected up to the aerial. are their relative audibility value, as de- diagram. This may be a 0.001 m.f. fixed condenser. Tp.'e termined by the U. S. Bureau of Stan- Diagram F ih, dards. The relative signal strengths are Picture Diagram of Set 1r a given in terms of percentages, and it will Our last diagram (F) is the ultimate in A complete drawing of the circuit with 're be seen that the hook-up has a great deal selectivity but has a very low audibility all of the parts in place is shown by Fig. to do with the reception, varying as it factor. The circuit is split by means of 3, the letters in this drawing correspond- aa;i does from 10 per cent to 85 per cent. the coupler coils (L2) and (L3) so that ing with similar letters in the schematic a1d These diagrams refer only to the detector almost any degree of selectivity can be diagram of Fig. 2. A detail view of the circuit itself and do not consider the attained but at the expense of a great coupler coil is shown which is connected if various methods of coupling or connect- loss in Signal strength. \Ve can obtain to the variable tuning condenser (C1), r'e ing the circuit to the aerial and ground. a good degree of selectivity by other the latter being connected directly across means without loss in signal b!e A variable condenser is used for tuning and so much the secondary coil (L2) of the tuning in- 'al a fixed inductance in all cases. strength; hence, this type or circuit can be ductance. The crystal detector (CD) is are neglected for the time being. best placed as shown and should not so Diagram A Circuit With Coupler be mounted on the front panel where it is Diagram (A) shows a simple form of likely to be thrown out of adjustment by circuit often used, which FOR the sake of selectivity we will con- the jar of the hand every time we move contains the nect our aerial and ground to the er inductance (L), the variable the tuning dial. condenser detector circuit by means of an aperiodic (Ll ^e (C), the crystal The tuning inductance -L2) is detector (CD) and the so phones (Ph) all connected in series. For or semi- aperiodic coupler of the type wound on a cardboard tube three inches commonly use in tube sets. For the de- in 1 ie ordinary broadcasting diameter and about 4 -2 indes long. wavelengths there we will will be about 55 turns of wire in (L) when tector circuit adopt the circuit The primary winding consists of 12 turns shown in Diagram (B) to obtain the of No. 24 D.C.C. wire, and a space of d wound on a three inch tube, and the capacity of the variable condenser (C) will greatest signal strength and will depend about 1 -2 inch is left between this coil be from 0.00035 m.f. to 0.0005 m.f. The entirely upon the coupler construction and the secondary coil (L2). Starting audibility is 55 per cent. for our selectivity and tuning. This coil (L2), we wind on 55 turns of the same combination will probably give us the size wire, and fasten the ends of the coil Diagram B best all -round combination for signal securely by passing them through holes strength and selectivity and at the same punched in the cardboard tube. For In Diagram (B) we have the same cir- time is simple to and tune. cuit with the build strong local stations, it may be necessary addition of the small fixed In Fig. 2 we have the schematic dia- to increase the distance between coils to condenser (K) connected across the stal cry- gram of the complete circuit. The 5 -8 inch or 3 -4 inch to obtain the required detector. This fixed condenser acts coupler consists of the primary coil (L1) selectivity, but this space should be no as a storage capacity for the waves and adds connected at one end to the aerial and greater than actually required for the considerably to the volume, as it to the ground at the other end. The radio complete tuning out of the strongest supplies an additional current to the impulses to crystal. from (Ll) are communicated station. If the gap is much greater than This addition has increased the the secondary coil (L2) which is identical this, the signal strength will be reduced. audibility from 55 per cent to 85 per cent, with the (L) in Diagram (B). A the coil The tentative wire (g) and the experimen- maximum value determined by the variable condenser (Cl) is connected tal fixed condenser (K1) are shown in Bureau. across the secondary coil so that it can be The dotted lines as they may not be needed capacity of (K) depends upon the tuned to wavelength. The fixed con- with the combination of parts used in nature of the crystal detector, but in any denser (K) connected across the crystal your set. event the capacity must be small to detector (CD) serves the purpose al- prevent by- passing The condenser (C1) can be either a 17 much of the current ready described. The phones (Ph) are plate or 23 plate variable condenser hav- across the dectector. With some de- in series with the crystal detector. tectors 0.00025 ing a capacity of 0.00035 m.m. to 0.0005 m. f. is about right, By means of the inductively coupled m.m., but the latter is preferable. If you while with other types this may be as coils (L1) we can much low and (L2) obtain do not wish to wind the coil yourself, you as 0.0001 m.f. or even less. A small better selectivity than with the aerial and can use a neutrodyne transformer which three -plate variable condenser will often ground connected directly to the de- can be purchased complete and mounted prove of value in getting the adjust- selectivity ment tector circuit. The depends on the back of the variable condenser. correctly. largely upon the distance between these Such combinations cover a wavelength Diagram C two coils. The greater the distance the band of from 200 to 600 meters, the range greater will be the tuning qualities where of the average broadcasting stations. In Diagram (C) we have the same cuit cir- there are many strong local stations. It is most convenient to mount the as in Diagram (A), but a fixed con- Properly it is possible to tune denser (K) is used adjusted, apparatus on a 6 in. x 7 in. x3 -16 in. panel to bypass radio fre- in and out on a difference of five meters as shown by Fig. 4 with the tuning dial quency current around the phones. The average wavelength, but with comparatively lit- (D) appearing on the front of the panel audibility under all conditions tle loss in signal With the is reduced to 45 per strength. as shown. The aerial binding post is at cent; hence, this is not aerial and ground connected directly to ANT, the ground connecting post at always an advisable addition. In many makes the detector circuit, it is probable that a GND, and the phone posts at PH. The of phones there is a considerable will in all around amount of distributed nearby station come method of connecting to the aerial and capacity in the the dial, no matter how it may be turned. ground is also shown in this view, the windings of the magnets and this frequently ground being a connection to a water or is sufficient to properly by -pass Holds on Grimly steam pipe. the radio frequency current around the inductance without In regard to a crystal detector, it may The aerial should not be less than 60 the addition of ex- be said that it is much more difficult to feet in length, and more than this is ternal capacity. However, in case the phones have a high get selectivity with a crystal than with desirable where the necessary room can be inductive value with a tube receiver and that greater care will obtained. With a crystal detector set, little distributed capacity, a by -pass (K) may be necessary. be required in the adjustment. The the more aerial wire that we hang up, the crystal has the peculiar property of hang- better will be our reception, and any Diagram D ing on to a station even against powerful length (L) can be used up to 150 feet. Diagram controls, and while it has not much dis- With two wires placed side by side, 150 (D) is a type of crystal de- tance or ability on weak signals, it will hold feet long and with the set located in the tector circuit often used on wave- meters and similar on like grim,death to fairly strong signals. open country, quite long distances can be instruments where very sharp Under some conditions it may be ad- covered. However, with a 60 foot aerial tuning is necessary. The audibility is so visable to connect the lower part of the in a goad locality, we can get good re- low (10 per cent) that it is impracticable circuit to the ground connection (GND) ception with fair distance, providing that for a receiver and therefore need not be discussed by means of the short dotted wire (g). the aerial is not screened by steel struc- further. Its only virtue is its The rotary plates should also go to this tures such as steel factory and office extreme selectivity. side of the circuit (ground) as indicated buildings, bridges, etc. by the curved line at (Cl) and the Diagram E stationary plates are connected directly Diagram (E) a second variable con- to the crystal detector (CD). denier (C2) is employed in addition to With some phones, which have very John B. Rathbun the original variable condenser (Cl). little distributed capacity, it may help This sharpens the tuning considerably matters to connect the fixed condenser has a surprise and has a much greater audibility than (K1) across the phones (Ph) as indicated in August Age the circuit in Diagram (D). The audi- by the dotted lines. This is best deter- the Radio bility is four times as great as with (D) mined by actual test, after the set has L L 1111 1111 9/R CORE Ch'Off.E. /RON CO.Pc.. Ch'OffE PRI PLA/N SPL/T O - iEi P ® s /'\ //'\\i.e\\ RFT VAR ,, VAR F (JIJU C \\\ iij \\\ e//

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Ì 32 RADIO AGE for August, 1925 The Magazine of the Hour A A Capacity Feed -back Receiver By JOHN B. RATHBUN

NEARLY all of our readers are in the conventional manner, and the blade familiar with the inductive feed- of the switch is then connected to ground. back types of regenerative cir- Variable condenser (C1) should have cuits in which tbe plate energy is re- A Sensitive Circuit ample capacity, Bence should be a 43 turned to the grid circuit through the plate or 0.001 mf type. Tbe grid con- inductive effect of a tickler coil, or by with Greater Volume; denser (GC) is a mica dielectric type means of tuning the plate and grid into with a capacity of 0.00025 mf while a mutual resonance by means of plate Variable Condenser the grid leak (GL) should be either a and grid variometers. He is also familiar variable leak or else a fixed type with a with the direct feedback type in which Controls Reaction resistance of about 1.0 to 1.5 megohms. the plate circuit is connected directly The tube (T1) can be any standard with the aerial as in the single circuit tube of the amplifier type such as the Ultra -audions and other circuits. shows the general arrangement on the UV -201A or UV -199 type. It will be However, there is a third means of rear of the panel and the run of the noted that both the detector tube (Ti) feedback whicb is highly effective, known wiring, but we advise the reader to make and the audio amplifier tube (T2) are as the "capacitative feedback" by which the actual wiring connections with the connected to the positive terminal of the plate energy is returned to the aid of either Fig. 1 or Fig. 2 as in these the same "B" battery and therefore primary and controlled through a varia- views the wiring is clearer and easier to that both tubes carry the same high follow. Keep these blueprint diagrams ble condenser between the . primary in- plate voltage. The "B" battery voltage ductance and the plate. for reference and you will have no trouble will range from 45 to 90 volts, but the As with the inductive feedbacks, there witb this set. best results are obtained at 67.5 volts are a great number of circuit combina- Looking at Figs. 1 -2 we see the tuning with the majority of tubes. tions possible with the capacity feed- variometer (VA) which is really a spe- At the output of the detector circuit back system and one has only to con- cially connected vario coupler of the we have the primary coil (4-B -P) of the sult an English radio magazine to dis- spiderweb type. In the particular audio frequency transformer (T) con- cover this fact. Its popularity in Eng- coupler shown a movable coil or "rotor" nected in the plate circuit. A fixed land is undoubtedly due to the fact marked (r) is connected in series with condenser (Kl) is connected across the that a capacitative feedback circuit the stator (s), the latter being the tapped primary which has a capacity of 0.001 coil. The tapped portion (L) of the has a lesser tendency toward breaking mf. The secondary coil ( -F) and (G) down into free oscillations when the coupler stator is simply the tapped por- is connected to the audio amplifying circuit is being forced, and as we all tion of this member but is drawn out tube (T2) through the 4.5 volt "C" know, radiation from the aerial is separately in Fig. 2 for emphasis in show- battery (C). The transformer (AT) ing the application of the tap switch the Englishman's private pet peeve. should have a ratio of from 5 -1 to 6 -1 Another factor which stands in favor of (TS). The tap switcb gives closer con- for the best combination of amplifica- the capacitative system is the fact tbat trol of the tuning and it will be noted tion and clear tone. Lower rations give much closer control of regeneration is that no variable condenser is included less distortion but also less volume. possible by means of a vernier variable in the grid circuit. It should be particularly noted that tbe condenser than by the standard tickler Regeneration Control ( -) negative pole of the "C" battery coil arrangements, and tkat the tube should go to the grid post (G) of the can be brought closer to the spilling AT (Cl) we have the vernier variable amplifying tube socket (T2). point without actually causing trouble. condenser in the plate circuit which controls the regeneration or feed back Simple Output Arrangement A Sensitive Hookup into the or primary aerial circuit. On SIMPLE single circuit jacks (J1 -J2, ICLAIM no for gen- hookup we will see originality the tracing out the that are used in both stages, and while eral of circuit which is the condenser is type demon- (Cl) effectively in series this leads to slightly diminished volume strated in this article except in points with the variometer (VA) and therefore in the detector stage, yet tbis is no of minor refinements. It has been that the variometer acts as an auto- practical disadvantage variously known as the -Reinartz," for the plate circuit, increas- as the detector "Super transformer is used only for receiving local as the "Inverted Weagant," ing the potential applied to the grid stations and the of in the majority of cases. The Audion" is advan- "Capacitative Ultra- at various the tube. This identical in action lies in times. However, no matter what to Weagant tage the simplicity of the jack its the circuit except that an connections and in the fact that the origin may have been, it is an exceedingly auto -transformer (Single circuit induct- circuit is not broken any ir. sensitive circuit and gives great is instead at time signal ance) applied of the two cir- switching from one stage to the other. strength on local. Tbe circuit is tuned cuit transformer used in the Weagant. to wavelength by means There can be no open circuits due to of a variometer Maximum potential is developed be- nor microphonic while the feedback is controlled poor jack contact by tween (Cl) and (VA) at the point where noises set up as this point. In the hands means of a vernier variable condenser. the grid circuit is connected through The principal improvement introduced of the novice a two circuit jack in the the grid condenser (GC) and the grid very frequently leads to in this article is the use of spiderweb detector stage a leak (GL). The detector tube is at trouble. Jack (J2) in the stage type of variometer. (T1) with audio its controlling rheostat (R1). is of the usual type and requires no In Fig. 1 of the accompanying blue- The use of a spiderweb inductance prints we show a wiring further explanation. diagram and in this circuit eliminates a great deal The only special instructions plan view (Looking down on of wasteful that top of the the distributed capacity seem necessary for this circuit are those set) which is for the use of our readers wbich commonly grounds a large per- which who are not familiar with conventional centage of the aerial current in single relate to the conversion of a vario- or symbolical diagrams. In Fig. 2 is circuit receivers of this class. This is a coupler into a tapped variometer. One the symbolical diagram of the set for marked advantage over the layer wound lead from the rotor or movable coil the information of the advanced readers type of coupler and shows up well in shown by (r) in Fig. 2 is connected to who may wish to learn how the circuit practice. The tap points on the section the outermost lead from the stator functions. An isometric view in Fig. 3 (L) are connected to the tap switch (TS) coil (s). In this way the rotor and RADIO AGE for August, 1923 The Magazine of the Hour 33 stator are connected in series and the In the old days when Armstrong was Radio Trade Association device now becomes a variometer. Do publishing his original means of producing not make the connection with the tapped regeneration and oscillation by means Meets end of the stator coil. Leave the tapped of an inductance in series with the B Unquestionably the biggest and most end battery and phones, which was induc- enthusiastic meeting of the Radio Trade open for the inductance switch Association ever held since organiza- connection. tively coupled to the grid circuit, Weag- the ant came along with another means of tion came into being was held in the afternoon of May 28 at Pontiac, Michi- Good Distance Work securing the same object. gan, the members of the Association With this set, the writer has pulled His scheme was merely the use of an being the guests of the Jewett Radio & them in for very considerable distances inductance in series with a condenser Phonograph Company of Detroit and in parallel Pontiac. The usual attendance of the and with surprising volume. It has all arranged to the plate and filament of the vacuum bi- weekly meeting of the Association the signal strength of a single tube. The induct- circuit ance used in the plate paralleling scheme was more than doubled. receiver combined The meeting began with a luncheon with a great per- could be placed either in inductive rela- centage of the selectivity of the three served in the Board of Commerce of tion to the grid or secondary coil, or it Pontiac, as a compliment from the Jewett circuit type. It is not quite so selective could be placed away from that circuit. Company. During the luncheon, short as a three circuit tuner, especially when Better control was found by putting the talks were made by E. H. Jewett, Presi- two or three local stations are going at plate or tickler coil in inductive relation dent of the Company, S. W. Edwards, one time, but it is much better than the secondary. Several years later Reinartz Secretary of the Radio Trade Associa- average single circuit arrangement in to the took up the \Veagant and did a tion, and Howard E. Campbell, Chief good deal Radio Engineer and Director of the this respect. One stage of audio fre- of intensive work with it, work- Broadcasting Division. quency amplification is always desirable ing it over into a single circuit instead In his short talk, Mr. Jewett expressed with any regenerative and is quite of the loose coupled original. his pleasure for having such a large economical. It is the addition of the He added the choke coil in the plate attendance at the meeting and spoke second stage that leads to complication circuit to assist in easy control of the briefly of the trend of radio manufactur- tube. ing and merchandising, calling attention and expense. to the fact that this Company was in One stage of audio permits of excellent New Circuits? the radio business to stay, to produce loud speaker volume on stations up to products of quality and to stand back Reinartz' work with the circuit was the of even after they reached 100 miles or so and makes headphone these products signal for a horde of eager -eyed experi- the homes of the consumers. He decried signals audible that would often be menters to start turning out circuits at the many instances in which "fly -upon- passed by with the detector tube alone. the rate of one each day or so, few of night" manufacturers and dealers have With UV -199 tubes, both stages can which had any particular merit. We put into the hands of the consumers be worked off of three No. 6 dry cells merchandise of a questionable character, have seen many instances where indi- which in the long run has tended to for a long time and with excellent results. viduals would take the basic Armstrong lower the confidence of the general public By biasing the audio tube (T2) the total circuit, transpose the position of the B in almost everything pertaining to radio. demand on the "B" batteries is very battery and the phones, or else the B This, he said, was on the mend, and before light and the smallest size of cells can battery and the plate inductance, and long the dawn of a staple industry which be used for long periods. then label it an original circuit. It used has as its aim -to serve every American to be so bad that conductors of technical home -is in sight. of departments in newspapers were putting In replying to the brief remarks the "B" Battery Current President of the Company, Mr. Edwards, WHILE the amplification is slightly on the market wonderful receivers with a representing the Radio Trade Association better with 90 volts of "B" battery fancy name, but having nothing but the of Michigan, graciously accepted the on the plate yet 67.5 volts gives nearly basic Armstrong or the \Veagant sub- courtesies that had been shown the the same volume with a much smaller stitute. And readers used to deluge members of the Association, and ex- the editor's desk with new and novel pressed a desire for closer and better consumption of "B" battery current affiliations among the representatives and witn less tendency toward whistling. circuits, all of which when analyzed turned out to be the basic stuff. of the various divisions of the radio With 45 volts on the plate the tone is industry. probably purer but the amplification is Some of the intricacies of broadcasting very much reduced. If only 45 volts Public Enlightened and a few of the humorous incidents are used, then the "C" battery should But fortunately this condition could that are always occurring in the studio be reduced to a two cell, three volt not persist. The public became more and of the broadcasting station, but are type in place of the three cell 4.5 voli more enlightened; the trimmers and never brought to light so far as the radio battery used for 67.5 to 90 volts. riff -raff of the game were gradually audience is concerned, were enumerated Fiom 40 to 60 feet of outdoor flat eliminated or else their wings clipped, by Mr. Campbell. top aerial will give very good results. and today the radio game is getting to Following the meeting in the Board of Corn - If the aerial is made longer than be pretty much of a standardized science of Commerce, the officials the this Associa- there will be trouble in maintaining in which the public cannot for long be pany and the members of the the factory, one of selectivity a mis- informed and mis -led without dis- tion went to the Jewett required although longer modern radio factories in the aerial may give a slightly greater range. astrous consequences. the most If you don't believe it, get up beforè country, located on the outskirts of the The great trouble with the majority of Here they were taken listeners a gathering of radio hounds and announce city of Pontiac. lies in the fact that they try through the factory proper, two units to hang up too much wire in their aerial in stentorian tones that you have just shown an original circuit. of which are completed and then circuit and in so doing increase the developed through the broadcasting station of the interference and disturbing noises that Seriously, the \Veagant- Reinartz- et -al- Company, which will come on the air may originate in the neighborhood. system has proved very popular prin- early in July. This station will be of the A single wire is better than two wires in cipally on account of the simplicity of latest type Western Electric equipment, parallel. regeneration control, by means of a having an antenna input of five thousand A 7'x14' panel can be made to accom- variable condenser which can make watts. modate this apparatus as laid out in capacity changes in the circuit with Between the towers, which havenow the drawings without much squeezing. greater finesse than the rotation of a reached one -third of their two hundred If it is likely that a second stage of plate coil inside of the secondary. Grant- foot height, the operators of the station audio will be added in the future then a ing the plate coil in the \Veagant combi- and workmen were laying some of'the panel 7'x18' should be used. Bakelite nation is fixed, it is possible to log the set. six thousand feet of ground wire required or hard rubber are the best materials If the plate coil is put at the filament for the station. There they watched:a for the panel, and while the baseboard end of the secondary, the wavelength specially designed instrument sinking s usually made of wood this can also is not thrown out when copying c. w. the wire a foot into the ground "as fast be made of hard rubber or bakelite. signals. as the tractor could pull it. I, C11n.IoIIIII11It m

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36 RADIO AGE for August, 1925 The Magazine of the Hour A Two -Tube Ultra Audion By JOHN B. RATHBUN

F the twenty -eight radio receiving fifty miles or more away from a broad- circuits known as ultra -audions, casting station, but in congested local O there is one simple circuit that is A New Version of :an traffic it is not much good, and in most commonly known to the radio Chicago it is practically useless except novice. This is the ultra -audion, Old Reliable Hookup on silent nights. alias the "Little Wonder Circuit," In Chicago, the complete set of parts alias the "Radio Demon," alias the have been sold retail for $6.75 for the "Ultraphone," alias the "Gibbon's Os- and not particularly selective where there single tube ultra, and from $10.00 to cillator." It has also paraded under the is much strong local, but it will reward $12.00 for the two tube set. This, of peculiar cognomen of the "Carpet of you by pulling in stuff that you would course, does not include headset, tubes Bagdad," which however, has nothing otherwise only read about. Dollar for or battery. This is not so much greater to do with the photoplay of that name. dollar, and tube for tube, you can cover than the cost of building a crystal set, In fact, every time that any dealer more mileage with the ultra -audion than except for the tubes and battery, and wishes to bring out a simple, cheap and any other set I know of, and it is on this you get real tube results with a few efficient distance getter, he drags out basis alone that I recommend it. For a dollars invested. the ultra -audion and labels it with his single circuit receiver it tunes quite I do not recommend the single tube pet name. Results are about as certain sharply, and is selective enough when ultra -audion for two reasons. (1) Be- with this little outfit as is possible with cause the phone impedance forms part any simple combination of variable of the inductive balance in the circuit condenser and single inductance coil; A COMPLETE BLUEPRINT which is upset when two or more pair of hence it is ideal in its own sphere of use- phones are inserted into the detector fulness. SECTION IN THE circuit, and (2) because there is a One thing that appeals particularly to ANNUAL considerable body capacity effect in the the poor hook -up editor is the fact that A thirty -two page blueprint phone cords when the headset is con- you have twenty-eight chances of avoid- section, replete with ¿tried hook- nected directly to the detector tube. ing a mistake in connecting it up; in ups and sixteen; pages of blue- By using an audio transformer as the fact, it is almost impossible to get it prints in actual color, isthe out- inductance for the first tune, we do hooked up so that it will not percolate to standing feature of the RADIO away with both difficulties and the re- some extent unless you should get the AGE ANNUAL'for:1925, now avail- ceiver is theretore much more flexible "B" battery across the filament of the able at $1.00 a copy. You can in regard to the output connections. tube. Confidentially, it can also be used use these blueprints as real work- A single tube ultra will not carry two as a transmitter over a short range by ing drawings, for they are clear sets of phones satisfactorily, either in connecting a microphone in the ground and easy to follow. Sixteen pages series or in parallel, for this varies the circuit. This statement will probably of blueprints TareIworth many feed -back potential and therefore the bring down the united curses of entire times the purchase price of the degree of regeneration. When working neighborhoods on my head for bringing ANNUAL. full blast on distance, the phone cord it to our readers' attention, but I thought n In addition to the blueprint capacity may be so great that the you ought to know it. Radiate? I'll section, there arelhundreds of new station will be tuned in or cut every say she does. When village pest for beginner and expert you move your head or touch the hookups "--for. time that starts twisting the dials of this outfit in the ANNUAL 1925. Every the headset with your fingers, but the you will see your neighbors climbing up to class of radio fan will find his introduction of an audio transformer and the house tops taking down their aerials. wants fulfilled. second tube will prevent this trouble. The first edition consists of a But It Works! limited number of copies, which Wide Wave Range IT may be noisy and it may radiate, are being exhausted quickly. Send your dollar NOW if you want to Fig. 1 is a picture diagram of the two but it certainly gets the DX. Like be assured of getting your copy INtube ultra -audion using a spiderweb every other circuit having distance of the RADIO AGE ANNUAL. coil or "pure inductance" for the tuning getting qualities, it is noisy, unstable, unit. This type of coil is far superior Blueprints of the Two-Tube Ultra Audion on Pages Following =a=tco:=4: - 112o 1=3*=3totx

Here is another of the forms by which it was originally attempted to get around the basic Armstrong. It is known as the ultra -audion and is nearly as old as the Armstrong itself. But it has changed its name oftener than a bootlegger. It also obtrudes its presence upon the Q neighborhood in about the same degree as the neighborhood cat. It is fine for the wide open spaces where men are men and single circuits are welcome, but not much for the crowded city sections when it is expected, on account of superior intelligence and enlightenment, the cliff - u dweller will observe the golden rule of radio -"Don't be a tweeter." Mr. Rathbun has efficiently described the circuit in the article above, so this leaves only the opportunity of calling your attention to the subscription contest on page 18. Read it and ri go out after the recruits; the RADIO AGE family sholud be expanded and the readers are the most logical ones to do it, especially since they have a chance at some of the monthly prizes.

L3 t=SlQf1031Ott0l7Qt70tFOi7QttQtlQltQ3iO i rcl RADIO AGE for August, 1925 The Magazine of the Hour 37 A New Version of the wavelengths, and the latter type of con- and difficult to manage and also takes denser is perfectly correct. However, a more current than the other tubes. Ultra Audion fixed condenser of 0.00025 mf capacity Any good make of audio transformer will do very nicely and is used in most of can be used at (AT) with a ratio of from to the common homemade coil wound on the ultra -audions. A variable grid leak 5 -1 to 6 -1. This single stage of audio a tube. With a 23 plate or 0.0005 mf at (GL) must be used under all condi- amplification is sufficient to get good variable condenser (C), the range will tions as the tube is very critical to the volume on distance, and with local be from 200 meters to well over 700 resistance of the leak. stations, very good loud speaker volume meters with the specified coils. It will can be obtained. In fact, I have had be well to use a vernier type of condenser The Plate Voltage fair loud speaker volume on local with so that the maximum signal strength Now just a word in regard to the the detector tube alone, so intense is can be more easily developed by closer voltage of the "B" or plate battery the regeneration in the ultra -audion tuning. (B). If we are to avoid excessive radia- circuit. The output (p -p') is connected When a spiderweb coil is used, such tion from our aerial, and reduce inter- to the phones or speaker, as may be as supplied by our advertisers, a total ference to a minimum, we must nor use desired. No jack has been placed be- of eighty -five turns should be specified, over 22.5 volts on the detector tube (T1). tween the detector and audio stage, as tapped at such points as will properly This result is attained by taking an inter- this would introduce "unbalance" into cover the range of wavelengths. The mediate "B" battery tap at the point the circuit and also give phone cord tap switch (TS) makes closer tuning (+22) at the 22 -volt section of the capacity effect, which is disastrous to possible over a greater wavelength range battery; as shown. If maximum amplifi- proper performance. than an untapped coil, but a plain coil cation is required without regard to Only a very small panel is required, can also be used with a total of 75 to and the set has been assembled satis- 100 turns. A 75 turn or a 100 turn factorily on a 6 "x10" and 6 "x12" size honeycomb coil will be right, but the with plenty of room for all of the parts. 100 turn is probably the better for the Its portability is a great feature and the broadcast listener with wavelengths aver- Working Blueprints small panel permits of placing batteries aging about 360 meters. This is one of of this famous and all in a comparatively small cabinet, the advantages of the ultra -audion; it thus making the set self- contained and can be used over a very broad band of handy to move about. When the detector wavelengths by simply substituting coils is used alone, without audio amplification, of various numbers of turns. Special ULTRA -AUDION a 6"x7" or a 7 6.x9" panel will be ample tapped honeycombs can be used as well HOOKUP for the accommodation of the parts. as the plain, untapped variety. Tapping In regard to the tap switch (TS), I is not a necessity but simply convenience. wish to say that the number of contact Wound on Cardboard buttons used will depend upon the num- Are to be found on ber of tapping points on the coil When the coil is wound on a cardboard and this is likely to vary somewhat tube, a diameter of from 2.5 inches to pages 38 and 39 among different makes of coils. I have shown seven 3 inches can be used, and we should have taps on the drawings, but this must be about 120 turns tapped at about ten - regulated intervals after the fiftieth turn. by the coil used. Some com- turn Another set of mercial honeycombs use five Thus, we will tap at 60 turns, 70 turns, taps, others use seven taps and there are so 90 turns, 100 turns, 110 turns BLUEPRINT SURPRISES coils with turns, nine taps. It should be and at the finish. This will give us seven understood that the number of taps tapping points, including one end. To in September RADIO AGE connected to the contacts is one less than conserve space use No. 26 D. S. C. wire, the total number of wire ends, since one if No. 24 or No. 22 can end of but desired, also the coil is permanently The low loss idea connected to be used. can be the aerial by wire (1). introduced by giving the coil a good coat- radiation, then we can put the full "B" In Fig. 1 is the picture ing of celluloid varnish (not shellac), voltage on both tubes by connecting diagram by which the most inexperienced should and then slipping the coil off of the tube (+B) of the transformer with the (+67) be enabled hook up set. 2 when dried. The varnish can made of the battery by means of the wire (22). to the Fig. is a be conventional drawing using symbols, by dissolving bits of celluloid in amyl If you love your neighbors, don't do while Fig. 3 is an isometric view which produces fairly good this anywhere except in the country showing acetate, a the back of the panel non -capacitative coating. If shellac where you are at least five miles from and the arrangement of the apparatus as it actually is used, you will get no results at all. the nearest receiving set. At least 45 appears, but it should not be The paper tube can. be slit lengthwise volts should be used on tube (T2) and used in making the actual connections, as some before winding, and when the is preferably from 67.5 to 90 volts so coil of wires we that we gain the maximum the and connections are hidden dry, can easily separate it from the audio amplifi- from view. For making connections, tube by breaking down the latter at the slit. cation. The high voltage on (T2) has use Fig. 1 Fig. 2. no radiating effect. either or An isometric is Now comes an important precaution very useful for gaining against body capacity. The stator or Owing to the fact that full control an idea of the general arrangement of the parts stationary plates (s) of the variable of the regeneration is had by the adjust- and main runs of wire, but if it is made so condenser (C) should be connected to ment of rheostat (Rl) it is sometimes a that all of the wires are in plain view, the grid line (5) while the rotor or moving good policy to make this a vernier rheo- then the view is so distorted its plates should be connected to ground or stat, but fair results will be obtained that principal value is destroyed. All sense of to line (23). If this is done, will from a plain rheostat of the proper not you proportion and scale are lost in this way. be annoyed with "body capacity" so that resistance. The rheostat (R2) is not when you put your hand anywhere near critical and any type can be used here. IN GENERAL, it is best to place a the dial it will detune or give a shrill The resistance of the rheostats depends spiderweb coil (L1), or "pure induct- "Whee- e:-ee" and break into violent upon the type of tube used. Any tube ance" as it is sometimes called, at right oscillations. can be used for the detector (T1) but angles to the condenser (C), for by this For the best results the grid condenser the amplifier (T2) must be some hard arrangement practically all electrostatic (K) should be a variable condenser or amplifier such as the "11, " "12," "199," or coupling between the parts is eliminated. one of the semi- variable grid condensers "201A" type. For small sets the '11" The audio transformer should be kept now placed on the market for this pur- and the "12" tubes work very well, but away from (Ll) to prevent noise. It pose. When the capacity is once adjusted of course the 201A is preferable where a seems almost unnecessary to state that to the requirements of the particular tube storage battery is justified. The soft all connections must be soldered, and in the socket it does not frequently need "200" tube is probably a more sensitive soldered without acid, but I will say it readjustment except on wide variations of detector at (T1) but it is more critical anyway for the benefit of the beginners. -A +A - +2z +67

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40 RADIO AGE for August, 1925 The Magazine of the Hour An Aperiodic Variometer Set By JOHN B. RATHBUN

TUNING the grid circuit inductively Live feed -back, yet the addition of the by means of a variometer is noth- plate variometer made the set even more ing new in radio. In fact, this is Applying Variometer selective than before and greatly in- practically as old as the use of the fixed creased the signal strength. Regenera- inductance tuned by a condenser, but the tion is more easily controlled without idea has considerable merit owing to the I dia to Good Circuit accurate filament current adjustment, fact that it is possible to establish higher and by the combined effects of the feed- potentials on the grid of the tube in this back coil and the tuned plate circuit, a way. Thus, the incoming signal has more HAVING progressed this far, the next condition of resonance is more accurately effect on the tube grid when capacity is thing was to apply the idea to some approached in both circuits and the im- lacking in this circuit than when a vari- specific circuit where its full possibilities pedance of the circuit can be made more able condenser is used for tuning the cir- could be developed without complicating nearly the theoretical zero necessary for cuit to wavelength. Better results are the controls. Various circuits were in- the establishment of maximum voltages. therefore obtained. vestigated and finally it was decided that In Fig. 1 on page 34 we show a picture In the older circuits, the grid vari- this circuit offered an excellent oppor- circuit of the set called the "Aperiodic ometer was used as a tuning agent for tunity for the application when the plate Variometer Set" with the two variometers single circuit sets or else it was used in circuit was tuned by a second vario- used for the grid and the plate respec- connection with the standard type of meter. While the original Wizard circuit tively. For maximum results and for tapped variocoupler where the additional worked very well without the plate loud speaker operation at fair distances losses introduced rather than offset the variometer and with direct induc- one stage of audio amplification has inherent advantages of the variometer been added permanently which gives an inductance. Used in a single circuit set, excellent two -tube set with great volume there was a loss of selectivity. Used with and a very considerable range. Of course, a standard variocoupler, the losses in the HOW TO USE RADIO AGE the detector tube can be used alone or taps and tap switches often offset the in- BLUEPRINTS else another stage of audio amplification creased efficiency of the variometer. In The RADIO AGE blueprints are can be added, but for the best results for other words, the variometer was never arranged in the ANNUAL so that a given investment, I believe that the cir- used so that it was allowed to develop they may be used as actual work- cuit is at its best the way that it is shown its full possibilities in the grid circuit. ing drawings by the set -builder. in the figures. It is certain that the addi- steps slightly Variometer For instance, each hookup de- tion of radio frequency only "Switched" scribed in the RADIO AGE AN- increases its range and that the expense After carefully going over this matter NUAL blueprint section consists and trouble of adding the radio stages is and experimenting with various combi- of four pages, two of which are ex- not justified by the slight increase in per- nations of variometers, it was finally de- planatory pages and the other two formance. cided to make the variometer an integral real blueprints. as Coil part of the primary and secondary tuning The Aperiodic Variometer set, Variometer Secondary circuits so that the variometer formed the for example, is described in the In Fig. 1, page 34, is the grid variom- secondary winding of the coupler, while a text on this page and on page 41, eter marked (VI) which is used for few turns of wire at one end of the while the blueprints for this hook- tuning the set to wavelength, this variometer acted as an "aperiodic" pri- up may be found on the two variometer acting as the secondary cir- mary coil. No condenser was needed, pages following. cuit coil of a two- circuit receiver. At the and the full selectivity of the vario- Blueprints in the ANNUAL blue- left is the aperiodic primary coil (L) con- coupler was attained without losses in the print section are arranged in the sisting of about 25 turns of No 26 tapped coils and rotor. The construction same manner for the convenience D. S. C. wire wound on a four -inch diam- is simplicity itself and lives up to ex- of the reader. eter bakelite or cardboard tube. In ad- pectations in every way. dition to acting as the primary of the Blueprints for the Aperiodic Variometer Set on Pages Following

Now We' ll Tell One! It's just like this; you pride yourself on being a subscriber of a magazine with a large circulation. No magazine ever has a large enough one, regardless of how high in the hundred thousands its circulation runs. So at this time of the year, when you are revamping your set for the Winter, you have a chance to add to RADIO AGE'S family of readers by rounding up annual subscribers and, incidentally, trying for some of the prizes offered each month for the reader who brings in the largest number of paid up yearly subscriptions. On page 18 you will find the terms of the contest. Each reader and contestant knows perhaps a lage number of individuals interested in radio who do not subscribe to this magazine. Just a little exertion on your part and two things are accomplished: You win one of the prizes and we add members to our radio family circle. RADIO AGE for August, 1925 The Magazine of the Hour 41 used if the other tubes are not practical Fig. 2, page 35, the latter being the An Aperiodic under the given operating conditions. The isometric view of the set. soft detector tubes such as the UV200 Variometer Set will not give as much volume on strong Audio Amplification signals as the UV201A or the UV199 for For aid in picking up distant stations for Efficiency the reason that we cannot carry such high at good volume and for loud speaker plate voltages on the soft detector tubes. operation on local and at moderate distances, one stage of audio frequency am- circuit, the coil (L) also acts as the Distortion Eliminated plification has been added. Stations 200 tickler or feed -back coil which induces As shown in the diagram, 45 volts are miles away have been picked up with additional impulses into the secondary used on the detector tube (T1) and 90 good volume on the loud speaker with by connections with the plate circuit. volts on the audio amplifier tube (T2). the single amplifying stage, and local The tube of (L) is fastened to the side This gives the maximum results without comes in with terrific volume. In fact, of a standard molded variometer in any distortion when the UV201A and UV199 local stations can be had on the loud way that may be convenient with the in- are used. Using a higher voltage on the speaker with the detector tube (T1) strument used. The distance between the detector tube (T1) gives a somewhat alone, but as will be explained, it is con- coil and variometer is not critical and greater signal strength on local stations sidered desirable to have the detector can be made as shown. Any type of but it also introduces undesirable tube and the amplifier connected in one per- molded or honeycomb variometer can be noises and distortion. Lower voltages manent unit. used, but a wooden variometer is not than those specified naturally give weaker A five -to -one ratio audio frequency usually practical owing to the great clear- signals, and the weaker voltages on the transformer is shown at (AFT). The ance space ordinarily found between the plate also reduce the selectivity of the primary of the transformer is connected rotor and stator of the wooden vario- circuit. at the posts (P) and (B) to the detector meters. The grid leak (GL) is of the pencil circuit at the output wires (e) and (f). mark or other variable leak. Its value is The secondary of to be adjusted until the signals are strong- the transformer is at AT (V2) we have the standard plate (G) and (F), and is connected into est and clearest. If the resistance is too the variometer used for controlling re- circuit of the amplifier tube (T2). A generation and for varying the inductance three cell, 4.5 volt "C" battery is con- of the plate circuit. This can also be nected in the grid circuit of the amplifier any standard type of molded or honey- tube for biasing the grid and is of great comb variometer but usually the induc- USE THE ORIGINAL assistance in clearing up the reception and tance value must be greater than can be BLUEPRINTS for obtaining maximum amplification. In attained with the ordinary wooden va- all cases, the negative ( -) terminal of the riometer. Very frequently the inductance On Pages 42 and 43 "C" battery should go to the grid (G) of of wooden variometers is so low that they to make This the tube, so that the grid will receive a have absolutely no effect on the regen- Aperiodic Variometer Set. negative charge or bias. The output or eration when turned in any direction, and plate (P) of the tube (T2) goes to the this fact is emphasized for the benefit phones or loud speaker (PH). of those of our readers who may attempt In laying out this circuit, it was con- the building of the circuit with this type high, then there will be noises and the sidered advisable to omit the usual jack of variometer. The tuning is exceedingly reception will have a whiney tone. If between the detector tube and amplifying sharp and fairly critical so that the addi- the resistance is too low, then too much stage, both on the score of simplicity and tion of a "Tiny Turn" vernier button to radio frequency current will be bypassed effective operation. While both tubes the dials of the variometers will be of and the signal strength will be reduced. must be used at all times with the present importance, or any other type of geared The proper value for any one tube can arrangement, yet it has certain advan- vernier adjustment which can be con- only be tried by direct experiment. tages which are lacking when interme- veniently attached to the dials. diate jacks are installed. For example, THE aerial connection at (ANT) to- there are no losses or noises due to imper- At (K1) we have the usual type of gether with the ground (GND) and fect contacts in the jacks, and, further, as grid condenser with a capacity of from battery connections are placed at the rear the audio stage is always in circuit, there 0.00025 to 0.0005 mf., the former value of the set, thus allowing all wires to enter is no danger of detuning a distant station usually proving best for the UV201A and the rear of the cabinet and improve the when the audio stage is plugged in. When ÚV199 tubes. Tube (T1) is the detector appearance of the receiver. The binding a jack is installed after the detector, and tube which is controlled by the filament posts at the rear are mounted on two when one picks up a faint signal, it often rheostat (R1). Of course maximum re- strips of bakelite or hard rubber about 1 happens that this station is lost when a sults are obtained with the power tubes inch to 1 1 -4 inch wide and about 3 -16 stage or two of audio is plugged in at the operated by a storage battery such as the inch thick. The strips are raised above jacks. UV201A, but very good results can also the surface of the bottom board, so that In this arrangement, this cannot hap- be obtained by the small dry cell tube no metal parts or wires will come into pen; and when the reception becomes too known as the ÚV199. The WD11 and contact with the wood. This construc- strong, we have merely to turn down the WD12 are not so selective but can be tion is clearly shown in both Fig. 1 and rheostats.

In the circuit shown here, patterned after the basic Armstrong with a few changes made by Mr. Rathbun, the energy from the plate is fed back to the grid circuit through the aperiodic primary. The absence of a variable across the secondary circuit and the use instead of a variometer increases the signal voltage on the tube grid. While it is true that variometers are gradually going out of existence, nevertheless there is a place for them in circuits of this type, and many an experimenter will never rest until he has tried out the scheme outlined above by the conductor of the blueprint section. z 1,

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44 RADIO AGE for August 1925 The Magazine of the Hour A Tuned Plate Regenerative Set By JOHN B. RATHBUN

PROBABLY one of the most effective the negative side ( -) of the battery types of straight regenerative cir- through the wires (9 -15). Each change cuits and the simplest to build is in the rate of flow in this circuit moves the "tuned plate" type in which the Attaining Selectivity the diaphragms of the phones (PII) and plate circuit is tuned to resonance with thus produces a sound. the grid circuit by means of a variable With An Aperiodic As the grid (G) of the tube is between inductance such as a variometer. the plate (P) and filament (F), it acts While I do not present this well known Coupler Added To a like a valve on the current flow. When circuit as anything new in its entirety, the aerial current induces a negative yet by the use of an aperiodic coupler Well Known Circuit charge on (G), the current flow is in- I am sure it is far more selective than the stantly checked. When the incoming older arrangement with a variocoupler signal imparts a positive charge to (G) and that it is far easier to tune. With a then the rate of flow is increased. Each single stage of audio amplification as one of these changes in the rate of flow shown in the following it is blueprints, a powerful steam engine or heavy stream causes movements of the head -set dia- an exceedingly good DX set and gives of water. phragms in proportion to the intensity good volume on distant stations. of the incoming waves. During this Fig. 1 is Varied is a "picture diagram" of the Inductance process of amplification, the incoming circuit arranged for the use of the begin- By means of the variable condenser waves are "rectified" or checked so that ner. In Fig. 2 is a schematic diagram (Cl) the inductance of the coil (L2) is only waves of like polarity pass through by which the action of the circuit can varied so circuit can be tuned or the tube. This rectification makes it be more easily that the traced out by those exper- brought into step with the frequency of possible to develop the "modulation" ienced in handling symbolic diagrams. the desired station. Coil (L2) by acting or voice frequency waves upon the In following description we will the inductively on (L1) allows only the phones, as the frequency of the radio refer, therefore, particularly to Fig. 2, current of the desired frequency to pass frequency waves is far too high to cause all three views bear same although the to The of of wire diaphragm movement. reference By earth. number turns numbers and figures. on (L2). and the capacity of the con- Thus the tube aets in two roles. In this system of lettering, the novice denser (Cl) determine the frequency of the first place it amplifies the incoming can trace . forth between back and the circuit or the wavelength to which signal waves, and (2) the tube rectifies the two diagrams become and thus it Increasing the number these waves so the voice frequency acquainted with the conventional may respond. that of turns on (L2) or increasing the capacity impulses are developed in the phones. symbols which mean so much to the wavelength We not with the experienced radio man. of (C1) increases the of the are directly concerned circuit. In the same way, cutting down rectification factor at present in describ- How to Increase Range the number of turns or the capacity of ing the regenerative circuit; hence we TO BEGIN with, in every type of condenser (Cl) lowers the wavelength will let this matter drop and consider straight regenerative circuit, some of of the system. As it is far easier to vary only the means of amplification. the amplified plate energy is fed back the capacity of (C1) than to alter the Named according to the tube elements into grid or input circuit of the tubes, number of effective turns, the number of with which they are connected, we have thus increasing the potential acting on turns on (L2) is fixed at some value so the grid circuit at (6- 4- L2 -7 -8) and the the grid of the tube and increasing the that the operation of (CI) will cover the plate circuit at (11- VA- 12- 13- 14- 9- 15 -F). range and signal strength of the circuit. complete band of broadcasting wave- The grid circuit is the "input" of the tube For example, the feeble little impulse lengths. The number of turns on (Ll) while the plate circuit is the amplified induced by a distant station in the aerial is not of so much importance in this "output." As the current in the plate enters the antenna binding post (ANT), respect, but in any case the turns on circuit is very much heavier than that passes through the primary coil (L1) and (Ll) are only a small fraction of those on in the grid circuit, it is evident that the thence to ground through the ground post (L2) output could be further increased if we (GND) and the dotted ground wire. Tubes or Crystal? could feed some of the plate current That is, the antenna current of the station back into the grid circuit for re- amplifica- to which the set is tuned passes to earth WE were to depend completely upon tion in the tubes. in this manner, the remaining waves IFthe signals produced in this way, the Thus, the plate current could be am- from other stations being "choked back" vacuum tube would not be so very much plified a second time with corresponding by the self-inductance of the system more effective than a crystal detector increase in the output, and this is While passing through the primary for the reason that the potentials acting exactly what is done with the regenera- coil (L1), the current sets up a slight on the grid of the tube are very feeble tive circuit. In one type, the con- magnetic field which threads its way and the amount of battery current con- ductively coupled regenerative, the through the turns' of the adjacent sec- trolled would be correspondingly small. plate (P) is directly connected to the ondary coil (L2) of the tuner and "in- The "amplification" or "multiplication" grid circuit as at (4) or to the aerial cir- duces" or creates a current in (L2). The of the tube would not be sufficient to cuit wire, (2). In another type, the induced current, known as the "secondary give us the tremendous distance and plate current is led through a "tickler" current" acts on the grid of the tube signal strength, attained by the tube coil which acts inductively on the sec- through the grid condenser (CG) and when used in a "regenerative" circuit. ondary coil (L2). leak (GL), thus causing the relatively As matters stand at this point, the In the present "tuned plate" regenera- powerful local battery current to flow in relayed battery current from the "B' tive, the feedback is "capacitative "; step with the pulsations in the aerial. battery (B) passes through the plate that is, the plate current is fed into the In effect, the tube is now simply a form circuit (12 -13) from the positive side grid circuit through the internal capacity of current relay or valve by which a of the battery (-i-), through the phones of the tube, control being had by means feeble pulsating current controls a rela- (PH) and back to the tube plate at (P). of the variable inductance or variometer tively much more powerful battery cur- Inside the tube this current flows through (VA.) It will be seen from Fig. 2 that rent in the same way that a slight move- the vacuous space between the plate the grid (G) and the plate (P) are like ment of the hand on the throttle regulates (P) and the filament (F) and returns to the plates of a condenser in regard to Blueprints of the Tuned Plate Regenerative on Pages 46 and 47 RADIO August, AGE for 1925 The Magazine of the Hour 45

A New Twist to the Tuned reduces body capacity. The extreme with the majority of circuits of this outer turn (c) of coil (L2), the end far- nature. It is nowhere near as bad as a Plate Regenerator thest away from the primary (Ll) should single circuit tuner and is better than other, and therefore grid be connected to the grid line (4 -5), and the majority of variocoupler types each current it should can be fed into the plate circuit or plate be particularly noted that the having a greater number of turns on the "stator" or stationary plates of (CI) primary. The looser the coupling current can be fed into the grid circuit should be- through the capacity of this condenser, be connected to (c), and also tween (Ll) and (L2) the less trouble providing that the two circuits are (4 -5). If this is not done, then there is there will be from local "razzing" and brought nearly into step or "resonance" likely to be trouble with body capacity. interference. with each other. Any standard variometer will work Do not let your tube whistle or howl The of the variometer well in this circuit, but if possible, obtain in tuning, and when you tune into a wave, inductance a "plate (VA) is varied until the grid and plate variometer" especially designed tune in sharply. Don't get in on the circuits are nearly in resonance, and when to work in the plate circuit. This vario- fuzzy edge of a wave. Don't keep your meter has fewer turns of heavier wire tubes heated up to bright incandescence. this is attained, plate current feeds than across (P) and (G) into the grid circuit, the "grid" type variometer. How- If you obey these instructions, you will producing "regeneration." This causes ever, both will give results if it is impossi- not cause much disturbance in the neigh- ble to a tremendous increase in the output of obtain these distinctive windings. borhood. the circuit with corresponding increases It will be well to keep the variometer From those of our readers who have in range. Without regeneration the well away from the tuning coil (Ll -L2) tried out this circuit from sketches mailed ordinary range of the tube would prob- so that there will be no coupling between to them before this article was written, ably be between 50 and 100 miles. Adopt- the two units, and for the best results we have had remarkable reports on its ing the regenerative principle makes it is better to incline the coupler at a selectivity and range. It is a simple, 1,000 miles an ordinary range on voice considerable angle so that the axis of the stable circuit without any gew -gaws, transmission and even 2,000 miles is not coupler does not coincide with the axis and should appeal to the beginner in of the unheard of. variometer stator. radio. Condenser (Cl) should be of the vernier type, Units and Dimensions capacity 0.0005 m. f. (23 HERE again we have the conventional plates). This form of coupler is very Armstrong, which seems to have sur- NOW we will get down to the practical sharp and a vernier arrangement of some vived all the fads and foibles of the game. description and give specific instruc- kind is therefore highly desirable. For Circuits have come and gone, but this form tions for the building of this receiver. the tubes ordinarily used, the grid con- seems to have stuck about as well as the We can now include the picture diagram, denser (CG) should be of the mica type crystal. In a way this is the same with Fig. 1, and the isometric view of Fig. 3, with a capacity of 0.00025 mf. While a the basic circuits; they survive while the which shows the general arrangement of variable grid leak is the best, a 1.0 adaptations and substitutes are gradually the apparatus behind the panel. With megohm fixed leak will generally be very eliminated from the field. the exception of the aperiodic coupler satisfactory. The bypass condenser Of course, any of the regenerative sets (Ll -L2) all of the apparatus is standard. (K1) has a capacity of 0.002 mf. and is coupled to an antenna will emit a strong There is nothing at all critical about the effective in reducing the impedance of or a weak wave when the tube is oscillat- set and even the inexperienced need not the plate circuit, for the phones (PH) ing, the strength of the antenna emission hesitate. For those experimenters who and the "B" battery both introduce a depending upon the amount of coupling have built the Baby Heterodyne II, I high resistance to the radio frequency between the antenna circuit and the will say that the same tuner, variometer currents in this circuit. The "B" battery secondary. If the coupling is close, and condenser can be used for building voltage may range from 16 to 45 volts, stronger emission will be noted than if the this circuit, and several of our readers but with the average tube it is likely that coupling is kept very loose. By the same 22.5 have already done this successfully. volts will be perfectly satisfactory. token an increase of selectivity is noted The aperiodic coupler has been described whenever the coupling is loosened more many times in these columns, but for Picking the Tubes and more until a point has been reached newcomers, I will the benefit of the where the feeble energy in the now dis- ANY type of standard tube will repeat these specifications. give tant antenna coil will not induce current Both the primary (L1) and the sec- satisfactory results, ranging from in the secondary. same the WD -12 to the UV -201A or UV- ondary coil (L2) are wound on the the For those who wish to follow he cardboard or bakelite tube. This tube 200. The latter is somewhat more sen- "golden sitive rule" of radio, a step of radio is about three inches in diameter and as a detector and will give good frequency ahead of any regenerative long. consists of results on voltages not much exceeding cir- four inches Coil (Ll) cuit, if properly arranged, will eliminate No. 26 double silk covered 22.5 volts. This tube is sharper 15 turns of and the emission from such regenerative cir- 1 the. more critical than wire, wound -2 inch from one end of the hard tubes. The cuits which emission has been secondary coil (L2) contains battery "A" depends upon the tube the bane tube. The of existence of countless thousands of size wire used. For the WD -12, single 1.5 about 60 turns of the same a volt cliff dwellers in the thickly populated and is started about 1 -2 inch from the cell of dry battery is used. For the UV- areas. end of coil (L2). In other words, there 199 we use three dry cells in series, giving is 1 -2 inch space between (Ll) and (L2). a total of 4.5 volts, while for the UV -200 Under certain conditions, particularly and UV -201 -A a six volt storage battery with long aerials, it may be necessary to is best. Symposium reduce slightly the number of turns on It is best to leave the aerial and ground (L2), say by five to eight turns, in order wires (1) and (2) connected temporarily on methods of doing to bring in stations on short wavelengths until the set is completed and can be around the 200 -meter mark. This is tuned in. Now connect the aerial (AN) away with best determined experimentally at the and the ground connection (GND) to time the set is built, owing to the great (a) and (b) alternately, until the best Oscillation variation in the constants of commercial results are obtained. When this is deter- condensers and variometers. mined, the connection of the primary In the September issue of Radio long wires, it is generally (Ll) can be soldered in permanently. To avoid Age fans best to support the coil on the back of There is one connection that is best will find an article deal- the condenser by means of short brass and experiments alone can determine ing with all the known methods of brackets which also serve as the con- this. preventing oscillation. Such an nections (4 -7) between the coil (L2) and As with all regenerative circuits, this article will be an invaluable aid to condenser (Cl). The jumper wire con- circuit will radiate from the aerial if those experimenters who nection (3) may or may not be necessary, not carefully handled, but owing to the are depending upon local conditions, but as small ratio between the turns on coils troubled with undesired oscillations. a rule this is desirable, as it greatly (Ll) and (L2) this effect is not as bai as 1Í1111I1Ii1IIIIi111I11I1I11111111!If

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48 The Magazine of the Hour RADIO AGE for August, 1925 A Regenerative Reflex Circuit By JOHN B. RATHBUN REFLEX circuit experimenters are coupler consisting of about 15 turns on divided into two camps. First, the primary coil (L1) and from 55 to 60 those who are adherents of the the turns on the secondary coil (L2). The crystal detector, commonly known as Getting Most coils are separated by about 5 -8 inch for the "Tube Conservationist Party," and selectivity and are wound on a three second, those who believe in the use of From Your Detector inch diameter tube with No. 26 D. S. C. the standard three -element tube as a wire. The secondary is tuned by the detector, and derisively called the "Howl 0.0005 mf variable vernier condenser (Cl). This concludes the tuning unit. Hounds." and range, and then I have seen the There are arguments in favor of both reverse. It depends a good deal upon The output of the amplifier tube (Tl) methods, but when it comes down to the and how it is put passes through the primary of the radio an who builds the circuit final analysis, it is not so easy to give up. I have seen both circuits howl with frequency transformer (RFT), and the opinion as to the merits of either side. considerable vigor, and the tube detector secondary of this transformer forms the In fact, I am very glad I am not in a has nothing on the crystal when the detector circuit of the detector tube position to take a stand one way or the latter is out of adjustment. (T2). \Ve can have either an untuned other and have declared a condition of well this point transformer at this point or an air -core columns go. It might be to remark at neutrality so far as these that a soft gas detector tube seems to be transformer of the neutrodyne type with There are those who go so far as to more effective in stabilizing the circuit a condenser tuned secondary, but for state that a reflex circuit never functions than a hard tube, so a soft tube should the sake of simplicity in the controls properly until there is at least some re- be used as the detector when possible. (RFT) is shown of the untuned type generation in the radio frequency stage, Probably one of the best tubes from this which will give good results on the aver- and if this is the case, why not carry out standpoint is the "sodion" tube, which age broadcasting wavelength range of the regenerative idea throughout and really does cut down the oscillating 200 to 600 meters. A tuned transformer dispense with the crystal? The other tendency to a marked degree. Then do gives us slightly more amplification, but party to the argument claims clearer you remember the little Welsh (501 -D) it runs up our controls to a total of three, reception, but when you come right down tubes with the filament wrapped around and this is not always desirable in a set to the bottom of the matter, the principal the outside? These were quite good of this kind. objective is the elimination of the de- detectors for this sort of circuit, but they As shown, regeneration in the detector tector tube and conservation of - the lacked the sensitivity of the sodions and tube circuit is had by the plate variometer battery current. So it goes. As reflex the volume was less. These tubes were (VA) which tunes the plate of the de- circuits with crystal detectors have been not oscillators and could not be made tector into resonance with the grid cir- presented time and time again in RADIO regenerative, but they were far more cuit. This not only increases the range AGE, I am going to hand you a circuit effective than a crystal and were much and volume but it also helps in obtaining this time which employs a three element quieter. selectivity. In place of the variometer works this de- tube detector and which The Circuit Itself we can also use a "tuned impedance" tector to the limit of its capabilities; in the plate circuit consisting ofpa 0.0005 that is, the detector tube will be made NOW we come to the actual circuit mf variable condenser with a 50 turn regenerative so as to squeeze out the last which is illustrated by the accom- honeycomb coil. This is for the benefit drop of blood remaining in it. 7an.ing blueprints, Figs. I, 2, and 3, of those readers who are not provided which are respectively the picture dia- with a variometer, but the results will Advantages as Detector gram, the conventional symbolic diagram be about the same in either case. If it is and the isometric view. These pictures desired, the tube (T2) can be made non - AL\\AYS remembering that I am and diagrams are clear enough for the regenerative with the variometer or tuned neutral ( ?) I will start the ball rolling class of amateurs I am appealing to with- impedance omitted altogether, and while by stating the following advantages out the use of extensive description, for the amplification will not be as great claimed for the tube as a detector. (1) I believe that this job should be tackled this way, yet it will be considerably A standard detector tube is capable of only by those who have had previous greater than with a crystal detector. considerable amplification within itself, experience in building reflex circuits. while a crystal detector cannot amplify. It is not so difficult, but it does need that An audio frequency transformer (AT -1) (2) A tube detector can be made re- experience by which we can make ad- with a ratio of from 5 -1 to 6 -1, is used generative, which adds still further to justments by the sound of the disturb- for coupling the detector stage output the range and signal strength. (3) The ance. Some of the bypass condensers with the amplifier input. This is of the use of a tube detector eliminates "cat - are likely to be rather critical, and with usual iron core type and needs little whisker punching" from the game of some makes of transformers, it may be further comment. Both the primary radio hide- and -seek, and this is truly an necessary to change the values of the and secondaries of the transformers are advantage. (4) Properly installed, a units from those given here. bypassed by the fixed condensers (K1) tube tends to stabilize oscillations in the Tube (T1) is the amplifier tube which and (K2). These will probably work radio frequency circuit (Perhaps). (5) amplifies at both radio and audio fre- out at 0.002 mf, but in some cases the That the detector tube is so efficient quencies, and therefore this must be a transformer characteristics are such that when regenerative that it gives just as hard tube similar to the UV -199 or they can be eliminated altogether. The mnch volume as one reflexed tube with UV -201A. Tube (T2) is the detector usual grid condenser (GC) of 0.00025 mf a crystal; therefore there is no real tube tube and can be anything that we may is used in the grid circuit of the detector or battery economy when a crystal is choose to use in the tube line. Either tube, and a one megohm grid leak (GL) used. In other words, one two -tube set a hard or soft tube can be used as a de- is connected across the grid condenser. with a tube detector will give just as good tector with the preference in favor of a As the detector tube is not in the aerial performance as two reflexed stages with gas -filled sodion type. The rheostats circuit, a higher grid leak value can be a crystal detector,so what is the use of (Rl) and (RI) must be adapted to the used than when the detector is in the the latter? (6) That a crystal detector is tubes used, and if controls are to be at a forward position and there will be no not a perfect rectifier as so often claimed, minimum, an amperite can be used in trouble with oscillations and radiation. and that it introduces just as much the filament circuit (R1) of the amplifier From 45 to 90 volts of "B" battery distortion and noise as an improperly (T1), but a rheostat must be always used can be used on the amplifier tube (TI), adjusted tube detector if not more. with (T2) as the filament adjustment but the plate voltage of the detector tube There you are; choose for yourself. for this tube is rather critical. Just as a depends upon the type of tube employed While all of the above statements are suggestion as to how an automatic fila- at (T2). If a soft detector tube of the academically correct, it is not always ment control can be used with an ampli- UV -200 type is used for (T2) we cannot so easy to make them work out in prac- fier tube, I have indicated an amperite have more than 22.5 volts at this point, tice. I have seen some tube detector at (Rl) in place of the more usual rheo- and as a rule it is not advisable to have reflexes which were wonders, and then stat, but the rheostat can be substituted more than 45 volts with any detector there were others which were far from if desired. An automatic filament con- (T2) as higher voltages give greater having this distinction. I have seen two - trol gives us just one less adjustment tendency toward squealing and oscilla- tube reflexes (with a detector tube) which to bother with, and when once right, it tions. To provide for the use of two would put a three tube and crystal de- remains right. plate voltages for the detector and ampli- ..rtor outfit to shame, both as to clarity At (LI -L2) we have the usual aperiodic fier, a detector tap is shown at (DB). 3Y.

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RADIO AGE for August, 1925 The .11agazine of the Hour 51 A Three -Tube Neutrodyne By JOHN B. RATHBUN

PROBABLY the'rnost popular multi - emission to the point required without tube circuit of the present time is also producing troublesome audio oscilla- the tuned radio frequency type, Clear Tone Assured tions or squealing, and this of course of which the neutrodyne is the most limits the possible amplification. In fact, the by a Crystal Detector prominent example. neutro- AMATEURS who have wished dyne was one of the first radio receivers \ dANY 1 to work the neutrodyne circuit more than three tubes which employing we have been held back by the expense of became popular with the broadcast cannot attain maximum amplification in the radio stages unless the feed- the usual five tube standard set. It is listener and therefore stands alone as for reason writer has worked being the representative long range back through this capacity is offset by this that the out a three tube neutrodyne which will least in the minds of some external device. Starting from the circuit, at the aver- give many of the advantages of the more age home builder. This popularity led antenna end of the circuit, we find that of will feed elaborate circuit with only a slightly to the development of a long series of some the radio energy straight internal of tube reduced output and range. A crystal "dynes" which bear more or less re- through the capacity the without any amplification. Starting detector is substituted for the more usual semblance to the original neutrodyne detector tube and only one stage of audio which of at the output or plate end of the radio and all of are members the frequency amplification is employed, tuned radio frequency family. stages we can see that some of the plate current is fed back to the antenna through thus doing away with two of the tubes. Tuned RF Arguments the tube capacity and thus produces Fig. 1 is a picture diagram of the three In a tuned radio frequency circuit regeneration with its annoying noises tube neutrodyne, where it will be seen we the distinguishing feature is the employ- and re- radiations from the aerial. When that have two radio frequency stages, ment of tuned transformers (air core regeneration in the radio stages occurs a crystal detector, and one audio stage. type) in the radio frequency stages. in this way, we cannot carry the electron This will insure very good distance re- on all Each radio frequency transformer is ception and loud speaker volume individually tuned to wave length by but the more distant stations. The means of a variable condenser connected crystal avoids the noises of the detector tube, thus giving a very pure, natural across the secondary coil and by this In this article you find the orig- means the maximum amplification or tone that is unapproached by the stand- inal neutrodyne, the patents on ard five tube set. Further, when properly "peak" is obtained on all wavelengths which are chiefly held by Prof. within the range of the condenser and adjusted it will not squeal nor howl under Hazeltine. This type of a receiver any tuning conditions. coils. Further, the tuning of the inde- long held sway, and still does to a pendent stages very greatly increases large extent, but the chief difficulty All Tubes Amplify the selectivity, since each transformer seemed to be in getting proper In Fig. 1 the two radio frequency tubes is an additional tuning coupler which neutralization at all wavelengths. are at (Tl) and (T2), the crystal detector augments and corrects the selectivity is (CD), and the audio tube at (T3). With the newer forms induct- at of the first antenna coupler. With two of All tube filaments are controlled by the stages of radio frequency ance winding, this trouble was (R), resistance of amplification, gradually lessened, single rheostat the we have three tuning controls, the an- until today by which depends upon the type of tubes proper design is tenna coupler condenser and the two it almost possible used, and as this carries the current for to arrange tuned r. f. circuits with- variable condensers used in All the resistance must be some - connection means of neutralization. tubes with the two radio transformers. Should out We what lower than when a single rheostat say for the sake of con- the wave of an undesired station "almost" is for tube. It must be borne succeed servatism, used each in passing the will though there are many in all of the tubes are ampli- antenna coupler, it who mind that be eliminated in either the first second claim total elimination of fiers such as the UV -201A, C -301A, or necessity for transformer of the succeeding tuned neutralization by the UV -199 or C -299 and that soft detector radio transformers. type of inductances now in use. tubes will not give the necessary ampli- Because of the condenser effect be- fication. tween the grid and plate of the tube, (Continued on Page 56) Blueprints for Three -Tube Neutrodyne on Pages Following Real Blueprints in RADIO AGE Every Month

Radio Age is the only Radio Magazine you can buy in which you can find real Blueprints of Radio Hookups. The Blueprints in this section are but a sample of what's in store for you in each issue of RADIO AGE -The Magazine of the hour Subscription, $2.50 a Year 52 RADIO AGE for August 1925 The Magazine of the Hour at a comparatively low cost we will not the circuit. We have only three tubes A Simple But Effective enter into their construction. and the small additional current taken Neutrodyne by the final tube doesn't make it practical Tuning Condensers to introduce jacks at this point. A fixed (Continued from page 55) The secondary tuning condensers (CI), bypass condenser (K2) bypasses the In the aerial circuit (ANT) we have (C2), (C3), should be a reliable make of radio current across the phones and the fixed coupler (RFT -1) with the variable condenser. Plain condensers "B" battery. The value of this con- aperiodic primary coil (1) and the sec- are used and verniers are not necessary. denser is not critical and may range from ondary coil (2). The secondary (2) is The majority of the commercial neutro- 0.0025 mf. to 0.006 mf. tuned to wavelength by the variable dyne transformers on the market require condenser (Cl) while the lower end of a condenser having a maximum capacity Battery and Voltages the primary (1) is grounded to the ground of 0.00035 mf or what is commonly known post (GND) and to the ( -A) line. The as a 17 plate condenser. Usually, a 23 TO produce the maximum range and plate output of tube (T1) is fed into the plate condenser is too large for this volume, we will require a 90 volt primary coil (1) of the radio frequency purpose, and makes the tuning un- "B" battery for supplying the plate transformer (RFT -2) where it induces necessarily critical and difficult. The current. This is connected between the a current of higher voltage in the second- condensers can be connected to the ( -B) and (+B) battery binding posts. ary coil (2) of RFT-2. The outer end transformer secondaries by the brackets The audio amplification will be made of the secondary (2) is connected to the shown or else by wires when the trans- somewhat greater if we introduce a 4.5 grid of the second tube (T2) where the formers are of the type which are fastened vole "C" battery between the secondary next radio amplification takes place. to the floor. transformer post (G') and the grid (G) The secondary of (RFT -2) is tuned to of the tube (T3). Full details of this wavelength by the variable condenser arrangement were shown on Data sheets (C2) which is the second control. In JJ -9 -25 and JJ-9 -26 of the September RADIO AGE. The installation in Fig. the same way, the output of the tube USE THE ORIGINAL (T2) is fed into the crystal detector cir- 1 of data sheet JJ -9 -26 shows the in- cuit (CD) by means of the third radio RADIO AGE stallation exactly as it would be made. transformer (RFT -3). The crystal de- Be sure that the negative ( -) post is tector (CD) rectifies the radio current BLUEPRINTS connected to the (G) post of the socket. into the modulated audio frequency After the circuit has been wired up current. On Pages 53 and 54 according to the diagram in Fig. 1, with Make the apparatus located as in the isometric ALL THREE units (RFT-1), (RFT-2) to This view of Fig. 3, we can connect the bat- and (RFT -3) are standard air core Three Tube Neutrodyne teries, insert the tubes, and then make radio frequency transformers commonly the neutralizing adjustments. With known as standard "Neutrodyne Trans- the tubes lighted up to normal brilliancy formers," and it is far better to buy these we can tune in some local station by to means of the variable condensers transformers ready made than attempt In the condensers to the until home. Unless properly connecting we obtain maximum volume. Now note making them at secondary coil of the transfromers we made, such transformers will greatly care to have the the position of the dials on the condensers, of the circuit should take particular and after loosening the dial, set the screws reduce the effectiveness or stationary plates connected in tuning. In the stator and turn them until the same number and cause trouble to the wire which runs to the grid of the Fig. 1, transformers are on each dial comes exactly opposite to diagram of the shown in the diagram. The down in a horizontal tube, as its stationary pointer. This will save shown laid flat rotor or movable plates should be con- position so that the connections can be much time in tuning, as we are now able to ( and If this is they are nected -A) ground. to get all three condensers in exact agree- more easily seen, but actually not followed then we will be sure of 60 degrees out, ment by turning to the same number tilted up at an angle about to trouble with body capacity. horizontal so that there will be have on each dial. with the The outside turn of the secondary coil no coupling between the adjacent stages. With everything running at full pitch, that we (to the right), the stator of the condenser It is of the greatest importance wire must remove the first radio tube (T1) from having the magnetic flux from one and the grid be connected avoid together for the best results. This is its socket and place a piece of paper transformer feedback into the following across the "A" battery contacts so that hence, the arrangement clearly shown in the diagram and should transformer, be followed out carefully by the builder: the tube will not light when replaced must be made as in Fig. 2 where the in the socket. With this tube in place, transformers are shown tilted up at an Any Ratio Possible but not lighted, see if you still hear the angle of 60 degrees with the baseboard. At (AT) we have the usual iron core local station with the rest of the tubes As shown by Fig. 3, the center to center audio frequency transformer for the at normal brilliancy. If you do, then spacing between the transformers and audio stage. Almost any ration can be adjust the first neutralizing condenser condensers is 5 1 -2', and the transformers used with slightly varying results. With (NC) until you can no longer hear the should not be closer than this if maximum a ratio of 3 -1 or 5 -1 we obtain very clear signals. With this accomplished, take results are to be obtained. With this amplification with a slight decrease in tube (T2) out of its socket, place a piece spacing we can get the apparatus on a volume. With a 10 -1 ration we have a of paper across the battery springs as 7x18' panel without difficulty but if somewhat greater amplification but with before, so that the filament of tube (T2) we consider adding a second stage of slightly increased distortion. A ratio will not light. With the other tubes audio in the future it would be better of 5 -1 probably is the best compromise burning, try again to see if any signals to use a 7x21' or 7x24' panel. but this is not exactly the case with all are being heard through the capacity of Returning to Fig. 1, we see the neutral - makes of transformers. In any case the dead tube. If signals are still heard ing condensers (NC) used for neutraliz- there will be less distortion and noise with (T2) dark, adjust the second ing the internal capacity of the tubes. with a crystal detector circuit than whén neutralizing condenser (NC) until signals At one end they are connected to the a detector tube is used, and therefore cease or are reduced to a minimum. grids (G) of the tubes while at the other we can probably use a higher ratio with The set is now only partly neutralized end a connection is made to an inter- this circuit than would be permissible at best and further adjustments of the mediate tap in the secondary of the with a circuit employing a detector tube. neutralizers (NC) will probably be neces- transformers. By adjusting these con- A 0.001 mf. fixed condenser (K1) is sary until the best tone and volume, and densers (NC) we can completely offset connected across the primary (P' -B') the best all around reception is had. the internal capacity so that maximum of the transformer to bypass the radio There should be no squealing or howling amplification is attained. The neutraliz- frequency component. No jacks are and the "tweet- tweet" of the carrier ing condensers (NC) should be purchased used for the detector and final stages, wave should be very faint when tuning ready made, and as they can be obtained since they introduce complications into into a station

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/1:dLMOQ400QQ90 RADIO AGE for August, 1925 The Magazine of the ¡four 55 A 3 -Tube Portable Reflex By JOHN B. RATHBUN

TO BE truly portable, according to mind, we will study the battery situa- my idea, means that a receiving tion and the proper tubes to go with set should be easily carried about Reversed Capacity these batteries. without seriously from place to place Dry straining its owner's physique, and at Feedback Cuts Out Cells Used the same time it should be so compact Storage batteries are out of the ques- that it will not take up any more room Free Oscillations tion, of course, hence only dry cells are than necessary in a trunk. There are available for the filament and plate portables and portables, but the absolute current. This means that the tubes zero in portability is the set made up in ment. Our current supply system must must either be of the \\'D -12 or the UV- a traveler's sample case which weighs be reduced to the lowest possible limit 199 type, which are specially designed about 100 pounds and occupies about even at some sacrifice in the life of the for dry cell service. They do not give fifty per cent of the trunk space. On the batteries. If the batteries stand up for the volume of the 201A power tubes other extreme is the freak midget set a month while traveling about, it is gen- used with storage batteries, but they which has been variously fitted into pill erally considered satisfactory for vaca- give excellent results if properly handled. boxes, fountain pens and pickle bottles. tion tours. At home, we can substitute The \\'D -11 and WD-12 are the same and which has absolutely no purpose in larger batteries installed-outside the set, tube with the exception of the base. life except to exhibit the make's in- but in touring, the space and weight are The base of the \VD -11 is a special small genuity. The real portable should have the principal items. With this idea in size, while the WD -12 fits in a standard a good range and sufficient volume to socket. Both tubes operate on the 1.3 operate a loud speaker, and yet at the volts produced by a single dry cell and same time should not take up a great "EVERYTHING I NEED take 0,25 ampere per tube. Each tube deal more space than a camera, even IN RADIO" therefore takes 1.5x0.25 =0.375 watt. when fully equipped with batteries. or 3 -8 watt. One No. 6 dry cell is pro- "I bought a copy of the RADIO No really practicable portable has AGE ANNUAL for 1925 and I vided for each tube, which can be con- been turned out with less than three found that everything I wanted nected independently to each tube of a tubes, for it is impossible to operate to know about radio, from crystal multi -tube set or to a multiple connected a loud speaker satisfactorily with less sets to complicated multi- tubers, battery with as many cells as tubes. tubes on anything but local stations. was contained between its two As 0.23 ampere is the rated discharge For this reason I will assume a three covers," wrote an enthusiastic rate for a No. 6 cell, it is not possible tube set from the beginning and will beginner. to use a smaller battery. never knew so much could be build up "I Next come UV -199 or the C -299 all the other data about this contained in one book without the premise. Whether this is to be a regen- crowding or omitting necessary tubes, which require 3.0 volts at the fila- erative, radio frequency or reflex still details. But you haven't left a ment, and which take only 0.06 ampere remains to be seen, but as the maximum thing out of the ANNUAL for of current. As the voltage of a battery volume is to be obtained from a minimum 1925." falls off with use, we must use three dry number of tubes and batteries, I have Letters such as the above are cells in series, which gives us a total of strong leanings for the reflex type. The sent to us every day, voicing sin- 4.5 with a fresh battery. This excess reflex circuit is not always the greatest cere appreciation of the ANNUAL is taken care of by a 30 to 40 -ohm rheo- for 1925, the most complete radio does permits the use of a battery distance getter, but what it get, hookup book ever printed. And stat, which it gets good and loud. the price for the 120 pages of between the limits of 4.5 volts and 3.0 volts, the batter); being discarded when Batteries Consume Space technical "nuggets" is but ONE DOLLAR, postpaid. the voltage drops to the latter point. ROBABLY the most important item Send your order now while The power taken is therefore: 4.5x0.06 =

- in a portable is that of the batteries, our supply of the limited first 0.27 watt, very much less power than is for the batteries weigh more and take edition lasts. required with the \VD -12. up more space than the rest of the equip- (Tarn to page 56) Blueprints of the 3 -Tube Portable Reflex on Two Pages Following

RADIO AGE is the only radio magazine on the market to originate and maintain the blueprint form of printing hookups in its columns. The popularity of such a process is shown by the countless letters from fans, many of whom would rather work from a blueprint than the best black -and -white drawing available. Every month you will find in RADIO AGE a set of blueprints together with a descriptive article by John B. Rathbun on how to construct a certain type of set. By becoming a subscriber of RADIO AGE, you have a steady stream of accurate and workable blueprints coming into your home; a handy reference for the future, or a necessity for the present in the making of a good receiver. 56 RADIO AGE for August, 1925 The Magazine of the Hour

(Continvel _from page 55) A special method of avoiding oscilla- with a separation between the two coils Q.talities of "199" Tube tions by means of a reversed capacity of approximately 1 -2 inch. The wire is feed -back is applied to the radio fre- No. 26 D. S. C. magnet wire. MOT only is the power loss with the quency tube, which has proved effective Condenser for Suppression - UV-199 tube, but the amplification in all the cases experimented upon by OSCILLATIONS is greater with the \VD -12, and the in the radio fre- than the writer. The plate current is fed back quency 199 is much more satisfactory in the circuit are suppressed by into the primary of the tuning coil the very small variable condenser (C) amplication of radio frequency currents through a very small variable condenser connected in reflex sets. In fact, the 199 comes between the primary coil in such a way that it opposes the free (on the aerial side) and the plate of the next to the 201A tube in regard to am- oscillation tendency of the first tube. first plication and only takes one -quarter tube (T1). This is a condenser It is a simple application of the reversed such as the "Chelton Midget" or the of the current. Three No. 6 "A" batteries feed -back system without the necessity "Amplex" will 199 for a long neutralizing condenser, having operate three tubes of a tickler coil. As the suppression of a maximum time, for the discharge rate is only capacity of from 0.000025 free oscillations is one of the most difficult to 0.00006 mf. 3x0.06 0.18 ampere, or less a This is somewhat critical = than propositions met with by the amateur on most sets, single WD -12 tube. The 199 is the ideal hence the condenser (C3) is represented tube for a portable set from many stand- by a dial on the front of the panel. When points, and takes up a minimum of room. MATERIALS FOR "JUNIOR properly adjusted PORTABLE" the first stage can be cleared up quickly As the rating of a No. 6 dry cell is 0.25 Codo No. of and easily by simple ampere for filament lighting, this size Letters Pos. Name Size this adjustment. A -9 'C" batteries. largo. 4.5 vna. The output of the first tube passes of cell will operate three 199 tubes for a Arr-2 Audio Frequency Transformers, 4 -1 to 6.1 ratio. through the primary (P) of the special very long period, much longer, in fact, B -4 'B batteries. 22.5 volt blocks. Small size (1200 m. h.). transformer (RFT -2) which transfers than would be absolutely necessary with CI -C2-2 Vernier variable condenser, 0 -00035 mf 17 plate). the radio frequency current to the de- a portable receiver. For this reason, C3 -1 Equalizing variable coodemer, we 0.00006 mf. tector tube (T2). This coil (P) is located can use a smaller filament battery bias C" -Small batter/. about 1 -4 inch from the end of the sec- with satisfactory results, and if the set D-1 Bakelite panel 10 83-4 "s3 -16" E-1 Bakelite tube shell 4 a6 ondary coil (S), and at the other end of is not used for too long a period, a 4.5 F-6 Marked binding posta. volt C battery can be used for each tube. GL-1 Grid leak (adjustable or fixed), 1.0 to 2.0 meg- (S) is the tickler coil (T) provided for obms. regeneration C J1- 1 Single eire.,it jack. in the detector stage. All As the battery takes up much less K1 -1 Find condenser. mica ins. type 0.001 mf. space and weighs much less than a No. K2-1 Fixed condenser, mica Ins. type 0.002 tuf. three coils are in fixed relation on the K3 -1 Fixed condenser with leak lugs 0.00025 mf. same tube, is 6 cell, we can use a 4.5 volt C for each K4-1 Find condenser mica ins type 0.00025 ml. and the detector circuit RI -R3 -2 Amperites for fila. control (199. 4.5 volts). tuned to wavelength by the variable tube or a total of three C batteries in R2-1 Filament rbeostst, vernier. 40 obm tylie. RFT -1 -1 Standard air core R. F. transform neutro- condenser (C2) connected across the all. For home use, where less frequent dyne type. replacements are desirable, we can use RFT -2 -1 Bakelite tube. 2 1.4 diem. 8s long. secondary coil (S). The tickler (T) has RFT -2 -l-4 lb. silk covered magnet wire No 26 about 25 turns, the secondary (S) has a larger external battery-a storage D. 8. C. 8-4 small brass shelf or support angle,. 58 turns and primary (P) is a 12 battery if necessary. 12' Bus wire, No. 14, tinned copper. the 1 Rosin core solder. turn coil. The general details of this An alternative will be to use two C l' Spagbetti. 25 Miscellaneous machine screws. coil or transformer are shown by Fig. batteries in parallel for each tube. This 17-2 Condenser dials (If not witb con.) 8" Diem. will give longer life than the singles as SW -1 Battery cutout switch. Standard. 1C, but it may be found necessary to 'Fl- T2-T3-3 UV -109 tubes. give a connected above, but will take less space V -8 "199" tube socket, absorb. base. few more or less turns on (T) until w-4 Condenser ongles for bolding coils on condenen. the proper regeneration is than three No. 6 cells. The following X --8' Flexible fixture cord for battery Connections, obtained with No. 18. the vernier rheostat (R2) turned to the table will give the comparative sizes: Y -1 Special cabinet (Complete) 1 Phone plug. "half -on" position. NO. OF SIZE OF SPACE 60' Annunciator wire, wax cotton or No. 18 flexible fixture wire for aerie). Need Accurate Rheostat CELLS CELLS OCCUPIED As 3 No. 6 5'x5 °x6.5 = 162.5 cubic in. the current flowing through the in the construction of a reflex circuit coil 3 C 4.1'x3 "x4" = 49.5 cubic in. (T) is almost entirely dependent a most 6 C 4.1 "x6 "x4" = 99.0 cubic in. he will find this important point upon the filament emission, and hence Fig. IA is a schematic diagram of the the rheostat adjustment, a very accurate In effect, the three C batteries will be "Junior Portable," showing the three rheostat will be required. A 40 -ohm connected in parallel through a switch, tubes, the transformers, and all con- rheostat will be found about right at and we will use the C batteries, as we nections. The tube (T1) is the reflexed this point for the proper control of regen- wish io get the smallest possible set. radio frequency and audio frequency eration by the filament emission system. If longer service from No. 6 cells is tube; tube (T2) is the detector, and If the tube has to be turned up bright required, then the only change necessary (T3) is the straight audio frequency for the regenerative effect, increase the will be to use a single group of three cell amplifier. All radio frequency stages number of turns on (T) until it starts in series of the No. 6 type, and to corre- are tuned by variable condensers so that to "flop over" with the rheostat turned spondingly enlarge the battery com- the maximum amplification peak is about half way on. The regulating partment of the set. attained, and at this same time this is a resistance for the radio reflex tube (T1) The Hookup Detail valuable aid to the selectivity of the set. is an Amperite shown at (R1), and a in The second tuning coil or radio frequency second Amperite is at (R3) for the auto- In general, the "Junior Reflex" is a transformer is of a special type, as it matic control of the amplifier filaments. regenerative reflex using a tube detector contains three coils which act respectively The amplifier tubes (T1 -T3) are not with a tickler coil feed -back and equipped as the primary, secondary and tickler critical, but the detector tube (T2) is with one additional stage of straight coils. Only two dials are required for very critical so that a rheostat must be audio frequency amplification. This the tuning operation proper, the regenera- used instead of an Amperite at this point. arrangement gives us one stage of radio tion being controlled by the detector The detector tube circuit is a conven- frequency amplification, a regenerative rheostat, a method that is entirely prac- tional feed -back circuit and has the usual stage, and two stages of autio amplifica- ticable with a vernier rheostat, and which grid condenser (K3) and grid leak (GL)' tion. Enough for three tubes. A short, greatly simplifies the construction and The grid leak is from 1 to 2 megohms, temporary aerial of from 40 to 60 feet tuning. and the condenser (K3) is probably best will be all that is ordinarily required, At RFT1 we have the usual aperiodic at 0.00025 mf. A bypass condenser either of the indoor or outdoor type, tuning coil with the primary (P) and (fixed) is placed at (K2) which is of assist- and I have had good service with a 30 the secondary (S) which is tuned by the ance in reducing the R. F. resistance of foot indoor aerial run around the picture 17 plate (0.00035 mf) variable condenser the detector plate circuit. The value moulding of the room. So far as possible, (C1) connected across the secondary may range from 0.001 mf to 0.002 mf, small or miniature parts are used to in the conventional manner. A detail depending upon conditions in the circuit. economize space, and it is surprising how of this tuning unit is shown in Fig. 1B, The circuit tuning condenser (C2) has much apparatus we can get into a small which shows the principal dimensions. a capacity of 0.00035 mf., so that (C1) cabinet when we make up our mind to There are 58 turns on the secondary and (C2) will "log" well together. concentrate our efforts to this end. and 12 turns on the primary coil (P), As is usual, the output of the detector RADIO AGE for August, 1925 The Magazine of the Hour 57

tube is reflexed back to the first tube with three tubes, and are shown in the tionary plates of the variable condensers (T1) by means of the audio frequency assembly diagram. With three tubes (C1- C2 -C3) connect to the grids of the transformer (AFT -1), the latter being kicking out from 10 to 12 milliamperes, tubes to prevent the body capacity effect in the grid return circuit of the first the 450 m. a. h. type does not last very from being carried out to the front of the stage. This can be any make of trans- long before the voltage runs down and panel through the shafts of the condensers. former having a ratio varying from 4 -1 the volume falls off. The grids are at a high potential, and to 6 -1, but as we wish to gain every In the table on page 38 is listed all of anything connected to the grids is easily inch possible, I have shown the miniature the material required for building this affected by the capacity of the hand and Premier Hegehog transformer in the set, each item in the list being preceded is detuned by this capacity effect. picture diagrams. In some cases, a by a letter corresponding to the letters All of the batteries are carried in the 0.00025 mf fixed condenser (K4) im- on the diagram. All of these parts are bottom of the cabinet, very closely proves results when connected across standard and the majority are built packed together to prevent movement, the secondary coil of (AFT -1), and again, by a number of radio concerns so that and connections are made with the cir- this seems to have but little effect. It it will not be difficult to pick up all of the cuit above through the flexible cords seems to be a matter of experiment with parts at your dealer's. The only special (X). Connections are more certain and each individual set to determine whether parts are the cabinet, which must be more easily made if "spade" type clips (Ii4) should be used. Its effect is prin- built to fit the job at hand, and the tun- are soldered to the ends of these cords. cipally on DX rather than on volume ing coils and RF transformer, which can Do not use solid wire for this purpose with local stations, so that we should try easily be wound up at home. A neutro- or simple cotton covered wire, as such for distance in making this adjustment former or tuning unit can be purchased wire is likely to short- circuit. Flexible rather than to experiment for volume for use in place of RFT -1, but RFT -2 fixture wire has a rubber covering which alone. is special and is not stocked. is further protected by a cotton braid, The output of the reflexed tube (T1) making a short circuit unlikely. now passes to the primary coil of the second audio transformer (AFT -2), and The Aerial Wire this latter transformer is a part of a Outdoors or 'fHE aerial wire can be a temporary straight audio stage that is not reflexed. Indoors 11 affair run around the picture moulding Connections are made to (T3) in the usual -You of the room, strung up temporarily from standard manner, and the total output Will Find All Your room to room, hung between trees or of all three tubes passes out through other supports. It is connected to the the output jack (J1) to the phones or Radio Needs antenna post (ANT) with the other end loud speaker. This is not a complicated Satisfied In left free and unconnected. For indoor circuit to hook up, but it requires some service about 60 feet of annunciator readjustments as with any reflex circuit, RADIO AGE will be sufficient and no supporting in- particularly in regard to the values of Every Month. sulators will be needed, as the waxed the bypass condensers. cotton cover will be sufficient insulation For the smallest portable set, three when laid along the plaster of the walls 4.3 volt "C" batteries are used for the Another Blueprint or along wood surfaces. For outdoor filament current as at (Al- A2 -A3), the Hookup In September work, or where it is likely to be damp, cells being in parallel and connected RADIO AGE-Out Aug.15 a wire with rubber insulation should be to the circuit through the battery cutout used, such as flexible fixture wire or switch marked (SW). lamp cord. Lamp cord is excellent for 22.5 Volts for Detector this purpose, as it has a low R. F. re- Fig. 2 shows all of the parts connected sistance and is sufficiently flexible to DLATE or "B" battery connections up in "picture" form for the benefit of allow winding up in a small coil. are tapped according to the require- the novice who does not understand con- After cutting the batteries into circuit ments of the various stages. A voltage ventional or symbolic diagrams. Either by means of the battery switch (SW), of 22.5 volts generally proves best for Fig. 1 or Fig. 2 can be used in making the detector rheostat (R2) and the the detector circuit under all around the actual connections, for both show the equalizing condenser (C3) are adjusted conditions, although 45 volts may give same circuit and the parts are lettered until all whistling and howling stop. greater volume and selectivity on local with corresponding letters. There should be a slight hissing or frying stations. A potential of 45 volts is most Fig. 3 is a rear elevation of the set with noise which will indicate that the tubes effective on the radio frequency tubes the back panel removed and shows how are functioning, but the adjustments on distance, hence a 45 volt tap is indi- the parts are assembled, ready for wiring. should not be much above this point. cated for this stage. The audio stage The three tubes and sockets are mounted Next, turn the wavelength adjustment requires 90 volts for the best performance, on the top of the shelf (E) while the audio condensers (CI) and (C2) very slowly and 67 volts gives nearly as good results transformers are hung underneath. This and at about the same rate of speed until with one less block of "B" battery. The not only saves room but it also shortens a "station whistle" or voice is picked up. set can also be operated with4.45 volts on and simplifies the wiring. Of course, Juggle the condenser dials until the signal the audio stage, but with greatly diminish- machine screws must be used for this is at a maximum, and then manipulat_ ed volume on all stations. I do not assembly instead of the more usual wood the detector rheostat (R2) just under recommend placing the full 90 volts on screws, as all parts are fastened to Bake- the point where it is about to break down the radio frequency stage, and never on lite. The shelf is attached to the panel into free oscillations and where the sig- the detector stage, and after experiment- by means of the small brass angle brack- nal is at a maximum. Working the ing extensively I find that the best all ets (S) which can be made at home or detector rheostat in connection with the around results will be found with the purchased at almost any radio store. condender (C3) will give the maximum plate battery connections as indicated. I wish to call your attention to the volume. Four small B batteries (90 volts total) fact that the two radio frequency trans- Remember that (C3) is for the purpose can be used for this set and will last most formers or tuning coils (RFT -1) and of checking oscillations in the radio of the season. The smallest B batteries (RFT -2) must be placed at right angles frequency circuit, and that this controls are the 450 milliampere -hour cells to one another, as shown, to prevent the radio frequency circuit in about the which measure 2' wide, 3 -3 -8' long and coupling back between stages and to pre- same way that the detector rheostat 2 -9 -16' high. The next largest size take vent oscillations being set up by induc- controls the detector. Howling can be up very little more space and give much. tion. The coils are supported by brass checked by either (C3) or (R2) depending longer service. This is the 1200 milli- lug connections to the terminals of the upon whether the trouble is in the radio ampere -hour size which is 2 -9 -16' wide, variable condensers so that their weight frequency or detector circuits. 4 -1 -6' long and 2 -3 -4' high. The latter is substantially supported. It should be The selectivity depends upon the size are the more practicable, especially particularly noted that the stator or sta- (Turn to page 58) Blueprints of the 3 -Tube Port.-ble Reflex on Pages Following 58 RADIO AGE for August, 1925 The Magazine of the Hour Battery Problem. Easily Handled (Continued from page 57) at the first attempt, try reversing the the positive of the "B" battery must distance of the primary coil (P) from the connections to the secondary and tickler always go to the plate directly, or to the secondary (S). The greater the distance one at a time, until you get the best plate through the tickler coil or trans- the looser will be the coupling and the results. After the best point is found, former primary. If this polarity is not greater the selectivity. This applies to you can complete the wiring by substitut- observed, the set will be absolutely dead both (RFT -1) and (RFT -2). Usually ing soldered bus wire connections for the without a hiss or grunt to be heard. the best spacing of the coils is as shown temporary wires. This may save you a A biasing "C" battery for the grid of by Figs. lB and 1C, but with some types lot of work and should be observed. the audio amplifying tube (T3) can be Be sure that the prongs of the tubes of audio frequency transformers, this connected in at ( -C) and ( +C) as shown must are making proper contact with the be increased. The wavelength just under the audio transformer (AFT -2) range is determined by the number of springs in the sockets, and try this out in Figs. 1 -2. This will save enough "B" on before you screw the sockets down into turns the secondary coils (S), and as battery current to pay its way, if place. A loose tube or loose contacts but it shown, will cover a range of from 200 is not desired at the present time, the to 600 meters. mean all kinds of trouble, and trouble binding posts or ( is difficult to remedy after the set is connections -C) and Fig. 4 is a front e.evation of the panel, that (+C) can be sort completed and in the cabinet. Also circuits as indicated showing the dials and other controls. by the dotted line carefully examine the jack connections, running between these It is advisable to allow the cabinet to two connections. The "C" can project and make sure that a projecting lump of battery beyond the panel in front for the be the smallest type of "C" battery or protection of the dials, and to provide solder is not short -circuiting the jack. The lugs very else can be a small flash light battery, a door at this point, so that the set can are close together and it is giving easy to short -circuit at this point. either a total potential of 4.5 volts be completely closed. on the grid of the tube (T3). Trouble Shooting Use only the small "midget" type WHEN the signals are weak and the variable condensers for the transfer (C3). A standard condenser, even as small as a Y selectivity seems poor, the trouble In this article Mr. Rathbun has made is usually due to coil reversal; that is, the three plate, is much too large to cover the up a set that is really portable. Hereto- various coils in the tuner or transformer range even with all of the plates out of fore portability has been a word and not do not bear the proper inductive relation engagement. The zero capacity of an accomplishment, for whatever was to one another. If, for example, the prim- standard condensers is very frequently labelled portable was sure to tip the the maximum ary coil should be connected so that it greater than capacity scale around the hundred pound mark. produces a magnetic field that opposes desired at (C3). But in this the weight is kept down, the field of the secondary coil, then the Sometimes reception is improved by which alone should appeal to the camper output will be practically neutralized and connecting a 0.001 mf fixed condenser or traveler. there will be little reception. It is for this across the ends of the jack (J1), and some- The future of the portable does not reason that I suggest that you connect up times this has no effect at all. It all seem to be in doubt. The set will be all of the primary coils permanently when depends upon the winding characteristics improved more and more as time goes you wire the set, and make temporary of the coils in your phones and speaker. on, so that eventually it will be down to a connections to the secondary coils and In making battery connections, be small sized outfit that can be readily tickler coil with magnet wire. sure that the positive pole of your "B" carried and which will at the same time After you connect up the set, you can battery is connected into circuit at the perform nearly as good as one of the tune in, and if results are not satisfactory point indicated in the drawings, that is, larger sets. l Meet Your Broadcasting Favorites

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K =o ,., L - /G. 4 ryCI(/N/OR PORTABLE" FROÑTELEVAT/ON 4.1 B.,QATHBUNj PKESSP T. PE/VO.) RFX-ï46 I RADIO AGE for August, 1925 The Magazine of the Hour .;3 More Volume and Range with A 5 -Tube Radio Frequency Set By JOHN B. RATHBUN

SINCE the introduction of the five - R. F. or audio amplification. In the most tube neutrodyne about two years part they confined their inventiveness to ago, we have had an almost end- A Receiver that Will contriving schemes for the elimination of less stream of five -tube radio frequency oscillations in the radio frequency stages. "dynes" which testify to the popularity Minimize Distortion For a long time the suppression of of this sort of radio receiver. This oscillations in the radio frequency stages neutrodyne was the first really high stages of transformer coupled audio was a problem to which many solutions powered type introduced to the general stages. There was seldom any attempt have since been offered. We have the public for broadcast reception. The at regeneration in the detector tube well-known neutralizing system intro- fans to this time had been limited to the circuit or any other means of amplifica- duced by Prof. Hazeltine, the reversed three-tube regenerative with the con- tion outside of the simple amplifying feed -back system, the potentiometer, of similar devices, and is in ventional detector and two stages powers of the tubes themselves. True, and it this part The of the of the circuit that most five tube audio frequency. addition the first neutrodyne introduced by radio two stages of radio frequency to the frequency circuits differ from each other. detector in the neutrodyne not only Prof. Hazeltine was of the reflex type, It would be almost impossible to say increased the range enormously, but also but strange to say, little interest was which of these systems has proved the very considerably added to the selectiv- taken in the reflexed neutrodyne until most sensitive and efficient, for each few seemed ity, and I believe that the selective a months ago. Experimenters type has its band of adherents who defy feature of the tuned radio frequency content to stick to straight radio fre- any of their opponents to show better set had as much to do with its promotion quency amplification without the assist- reception or greater range. as the increased range and the possi- ance of either regeneration or reflexed It has long been the belief of the bility of coast -to -coast reception on the writer that very marked improvement loud speaker. could be made in the five tube radio Untuned radio frequency reception WHAT KIND OF A SET DO frequency receivers by the introduction with untuned radio frequency coupling YOU WANT? of regeneration in the detector circuit units had proved somewhat of a fizzle, The RADIO AGE ANNUAL or by reflexing certain of the stages so not only because the maximum range for 1925 has a blueprint section that some of the tubes could be made to and signal strength were not developed in actual color, in which is perform dual duty. Shortly after the but also for the reason that such re- contained every kind of hook- introduction of the neutrodyne, I made ceivers were hardly more selective than up from one -tube simple sets several experiments in obtaining re- regenerative set of that period, and to an efficient 8 -tube super- generation in the detector circuit by the heterodyne. Whether you are even two years ago the question of inter- contemplating building your means of a variometer or tuned im- ference was becoming a serious proposi- first set or branching out into pedance in the plate circuit, but while tion. By tuning the transformers be- complicated "multi- tubers," this increased the range and signal tween the radio frequency stages, we you will find the ideal re- strength considerably, it did not meet reach the amplification peak in each ceiver for your needs in the favor for the reason that it introduced stage and also increase the losses at a 32-page blueprint section of a fourth control, and a rather critical number of points so that 'undesired the ANNUAL FOR 1925. Every sensitive control at that. Further, stations could be eliminated with cer- hookup a tried and true winner. regeneration was not always dependable even through strong local inter- Assure yourself of owning with neutralized grids, and as neu- tainty, this wonder hookup book by ference. Using three tuning controls sending one dollar now to tralization held the floor at that time to made long distance reception possible RADIO AGE ANNUAL, before the exclusion of every other idea, the for the city dweller on every night in the first edition is exhausted. matter was dropped for the time being. the week. Hundreds of RADIO AGE fans Rheostats Cause Trouble The Typical 5 -Tube Set have bought their copies and USUALLY the five -tube outfits con- written us their praise. Get TO ELIMINATE the fourth regen- sisted of two stages of radio fre- yours NOWT erative control, I next tried several quency amplification, detector, and two (Turn lo page 64) Blueprints of the Five -Tube Radio Frequency Receiver on Pages Following. If You Want To Be Timely in Radio Affairs, Read RADIO AGE Every Month ! For Radio news and latest Radio Hookups, RADIO AGE has never been "Scooped." As soon as a new and promising hookup has been tested and found efficient, it is presented to the readers of RADIO AGE, in a clear, concise manner, illustrated profusely with accurate isometric and circuit diagrams. So-Let Our Hookups Be Your Guide 64 RADIO AGE for August, 1925 The Magazine of the Hour results with a Reflexed Detector (Continued from page 63) usual first two radio frequency tubes of apparatus he intends to use. A 400 regenerative stunts in the detector cir- (T1) and (T2), and the three radio ohm potentiometer is the best, but it 200 cuit such as the fixed tickler used in the frequency coils or transformers, (RFT -1), ohm can also be used, and to reduce the Wizard receiver, and the Ultra-audion (RFT -2) and (RFT-3) connected up in radio frequency resistance in the grid single control method, both of which the usual way of radio frequency trans- return line, a fixed bypass condenser gave strong regeneration and sensi- formers. The transformers are tuned (K1) of 0.0006 mf capacity is con- tivity but which made the rheostat by the 17 plate (0.00035 mf) variable nected between the slider and the nega- controls critical and difficult to manage. condensers (C1), (C2) and (C3) con- tive "A" post of the potentiometer With such circuits, control of the regen- nected across the secondary coils of the resistance coil. The impedance of a wire eration is had entirely by the rheostatic transformers. There is little to say wound potentiometer is considerable, or filament emission method, and a about the transformers except that they and unless the bypass condenser is vernier rheostat is absolutely essential are of the conventional type used in installed, the tuning will be upset at for the proper adjustment. Unless it every adjustment of (PO). was brought just below the oscillating point, the circuit would break out into BILL OF MATERIALS Reflexed Third Tube violent free oscillation with accom- FOR THE SET TUBE (T3) is the tube ordinarily panying howls and shrieks. While this MARK NO. OF used as the detector tube, but in this wonderful results in the hands of (LETTER) PIECES NAME OF ITEMS SIZE gave A I Filament A' Battery, Stop- case it is the tube of a special reflex an experienced operator, it certainly age Volts circuit, acting both as a radio 1 Audio Frequency Trans- and audio was not a circuit to install in the home former 6-1 Ratio amplifier at one tinte. In fact, there is B 2 45 Volt Block. of B" or for the everyday broadcast listener. Battery ...... Large. no detector tube in the circuit since the while CI-C2-C3. 3 Variable Condenser. It seemed for a that the only 0.00035 ant (17 Ph.) major part of the rectification is per- resort was to reflex the detector circuit CD I Fixed Crystal Detector CLI -CL2 2 Grid Leak...... I-2 Megohm. formed by the crystal detector (CD). and this is what I finally accomplished JI Twoeut Jaek Standard J2 Single Circuit Jack.. Standard Transformer (RFT -3) connects the radio after a number of experiments. The K1 Fixed Mica Condenser 0.006 Mf. stages to the reflex stage K2 Fixed Mira Cond 0.002 MI. and the reflex reflexing of the so-called detector stage K3 Fixed Mira Cond 0.002 Mf. is tuned by the third variable condenser K4 Fixed Mica Condenser 0.006 MI. or third tube both increased the volume KS Fixed Mica Cond 0.006 MI. (C3). Note that all of the radio fre- the quality of recep- KB Fixed Mica Cond 0.002 MI. and improved the K7 Fixed Mica Condenser 0.500 Mf. quency and audio frequency trans- tion, and from many standpoints was NI -N2.. Reel Coupling sistan es...S Ohm. formers are marked according to the an advance over the regenerative prin- PO Potentiometer connection posts as at (P), ( (G) ..400 ohm., or 200 ohm. +B), ciple or the totally reflexed method by RI- R2 Rheostat. for (dament and -F), to correspond with the mark- Control .sass. . 6 Ohm. which all of the tubes were reflexed. RFT- 14-3. Radio Frequency Trans- ings on the actual coils. third tube former.. (Tuned) . Standard Reflexing the alone gave us RFX Untuned Radio Frequency At (RFX) is an untuned radio fre- approximately three stages of radio Transformer 200 -600 meters SW Battery Switch Standard quency transformer used for coupling frequency amplification with the same S Tube Socket. Standard the plate circuit of (T3) with the crystal TI- 2 -3-4 -S 201A Amplifier Tube. Standard number of tubes ordinarily used to obtain VM B Voltmeter (Flush detector and the audio transformer Type) 8 to 10 Volt. two stages, and in addition it added w Panel 7'.26.3 -16e (AT). The latter is of the usual iron 0.8 of an audio stage. Marked... Binding Posts.. ...Standard about Further X Terminal Strip (bake - core type, bypassed on both the primary audio amplification was then obtained lite) 1"s7es3 -16' Y Bottom Board (Wood).... and secondary sides by the fixed bypass by two stages of resistance coupled .. I-2'a25ÿ1 -2e condensers (K2) and (K3). Ordinarily Z Radio Cabinet .7.26' audio, which gave the total audio volume 30' Tinned Copper Square Bus the capacity of these condensers is Wire .... sass. .No. 14 without the distortion usually intro- ó' Spaghetti Standard 0.0015 mf to 0.002 mf, but much depends duced by iron core radio frequency 50 Solder Lus. Standard D.... 3 Dials and Knob. 4e Diameter upon the type of audio transformer transformers. NOTE( Item. marked () can be substituted In some cases it will found fer by complote re.i.t.nce coupling unit.. used. be Summing up the matter, we obtain advisable to omit (K3) altogether when practically three stages of radio fre- there is much distributed capacity in quency amplification and the equivalent the primary winding. of two audio frequency transformer standard radio frequency circuits, and On carefully examining the circuit coupled stages by five tubes, and with- that it is far more desirable to purchase of tube (T3) you will see that it is a out distortion or "razzing" even when these parts than to attempt making simple single tube reflex circuit giving the tubes are being pushed to the limit. them at home. the equivalent of one stage of radio The audio stages consist of one trans- The three tubes (T1- T2 -T3) are con- and one stage of audio amplification, former coupled stage and two resistance trolled by the six ohm rheostat (RI) so that up to and including (T3) we coupled stages, which give us a volume while the two audio frequency ampli- have three radio and one audio stage on slightly better than two transformer fying tubes (T4) and (T5) are regulated three tubes. This alone will give good stages. A crystal detector performs the by the six ohm rheostat (R2). In giving results, but for the proper loud speaker rectification without introducing the the resistance of these rheostats, I am volume under all ordinary conditions, tube noises that ordinarily affect the assuming that 201A tubes are used, it was considered advisable to add the output. In short, it is just like adding because they give better results than the two resistance coupled stages as shown two stages of radio amplification to a dry cell type. If 199 tubes .are used, by tubes (T4) and (T5). single reflex circuit and then increasing then the resistance of thr rheostats By plugging in at jack (J1) we obtain the volume by the further application must be higher, say 15 or 20 ohms. the output of three radio and one audio of two resistance coupled stages. With five tubes, dry cell operation is stage. By plugging in at the jack (J2) The Circuit Layout not recommended, for in the end it will we obtain three radio and about 2.6 be far more expensive to replace dry audio stages. IN FIG. 1 we have the layout shown cells than to purchase a storage battery A typical resistance audio coupling by a schematic diagram and in Fig. and recharge it from time to time. Dry is made for the tubes (T4) and (T5). 2 the same circuit is given in "picture" cell tubes do not give the amplification The fixed condensers (K4) and (KS) form, which not only shows the wiring of the storage battery 201A type. of 0.006 mf capacity are the coupling in simplified form, but also suggests Grid potentials are regulated by the devices in the grid lines, while the re- the arrangement of the apparatus behind potentiometer (P9). While there are sistors (Nl) and (N2) are non -inductive the panel. Fig. 3 is the front elevation certain objections which can be leveled resistances of from 48,000 to 50,000 of the panel with the control dials and at this type of control, yet it is the better ohms. Both of the resistors are con- knobs located. method for the beginner, especially nected between the positive "B" (+3) Looking at Fig. 1 or Fig. 2 we see the when it is not known what make or type and the plate (P) of the tube, and it is RADIO AGE for August, 1925 The Magazine of the Hour u5

Tubes Do Dual Duty in. This Set ¡ the difference of potential established ing can be put on a 7'x24' bakelite series and require the most accurate across these resistors that causes the or hard rubber panel. The inside dimen- adjustment for the filament control. amplification. The grid leaks (GL1) sion of the cabinet (depth) should be Cutting the large hole for the body of the and (GL2) are of one megohm to two at least seven inches to accommodate voltmeter is a problem for the home megohms capacity and are connected the apparatus. Care should be taken mechanic unless he has some form of between the grids and ( -A) just as not to crowd the radio frequency trans- "fly- cutter" for the job. However, this with any grid leak. Such resistors formers RFT -1 -2=3 too close together can be cut by any machine shop or introduce no distortion into the circuit, and the tubes should be well oustide radio store. and when worked in connection with the magnetic field of the transformers Unless the transformers (RFT) are one transformer coupled stage as at to prevent back coupling between the marked at the connection post by the (AT), we obtain both volume and purity stages. The panel thickness should be makers, the builder often has trouble of tone. The ratio of (AT) should be at least 3 -16 inch so that it will not be from "bucking" or opposed coils. If from t to t but no higher. necessary to cut down screws or shorten you do not think that you are getting The resistors (N1 -N2) can be obtained the shafts. the proper volume or the distance, try from a number of RADIO AGE adver- In arranging the reflexed part of the the effect of reversing the connections tisers, either as separate units or as circuit, see that the untuned transformer to the primary of these coils, one by assembled units containing the fixed (RFX) is placed as close to the tube one. In fact, it is best to connect up the condensers, resistor and leaks all in (T3) as possible, so that the line from the transformers temporarily with small one compact mounting. post (G) on the transformer to the (G) insulated wire until you are certain that Fig. IA at the bottom of the circuit post on the socket is very short. This the polarities of the transformers are drawing shows the method of connecting is important. Again, keep (RFX) well correct. up the resistance coupling units in com- away from (RFT -3) and the audio trans- All crystals do not work equally well pact form when the resistors and leaks former (AT). If these parts are so close when reflexed, and for this reason it is and condensers are purchased separately best to get some sort of a crystal detector and assembled by the builder of the set. in which the crystals can be easily Spring clips can be obtained for mounting changed. With a small stock of crystals, the resistors and grids just as tubular say five or six, experiment until you find grid leaks are mounted the best crystal. Crystals do not cost Bypass condensers such as (K6) of Are You Going to Take much and they may be the reason your 0.002 mf capacity and (K7) of 0.S mf a Radio Set with circuit is not functioning as it should. capacity are frequently of advantage You on your After the crystal detector is once ad- in reducing the resistance offered to the justed, and put in an out -of- the -way radio frequency current by the "B" Vacation This Year? place where it is not likely to be dis- battery and the impedance of the output turbed, it will require very little attention. circuit, particularly after the "B" bat- Watch this and teries become old and dried out. In Use Care in Building some cases and using certain materials future issues of IAM sure that if you construct this in the circuit, these bypasses work a RADIO AGE great improvement, while under other receiver with care and use judgment conditions their effect is unnoticeable. for the latest in in the operation of it, you will get ex- the set will perform better Portable Receiving Sets ceptionally fine results. Its freedom from However, distortion extreme sensitiveness and more consistently throughout the and Accessories. and are life of the "B" batteries when the by- remarkable. Stations from both coasts passes are used than when they are not have been heard repeatedly on the loud installed. speaker from my laboratory here in Chicago. Materials Used As I stated before, Professor Hazel - that they are coupled by the magnetic tine's original neutrodyne was of the re- ALMOST any of the standard materials flux, there will be trouble. The crystal flexed type, but for some reason little in RADIO AGE can advertised detector, which is of the fixed or semi - interest was taken in it. Why this should be used for this circuit, and as it is against fixed type, can be placed in such a posi- be is hard to explain. I suppose the rea- our policy to recommend one make of tion that it does not complicate the son is that most fans were a little bit apparatus over another, we cannot wiring, say near the rear edge of the afraid of the reflex circuits. We really specify any particular make in these bottom board. It is not advisable to have no reason to fear them, as they are specifications. The only effect that will put the crystal detector on the panel, quite simple. It just requires a little be caused by changing parts will be on as it is likely to be knocked out of ad- patience to get them to operate correctly. the values of the bypass condensers, justment every time we handle the dials. Most of the trouble experienced seems and this is always more or less of an The coupling resistances for the audio to be in getting fixed and by -pass con- experiment in any case. However, the stages are small and easily disposed of densers of the right capacity. However, bypasses are quickly and cheaply shifted in the arrangement, and as shown in these are cheap and if the builder will about, and this should prove no objection Fig. 2 these audio coupling units are supply himself with a selection of these, will show to the user. Experience that placed quite close to the two audio - he can change the capacities of each in it is very seldom that any one value tubes (T41 and (T5). All of the arrange- the different parts of the circuit until the of bypass will apply to all conditions in ment should be made with an eye to best results are obtained. any circuit. simple wiring and simple connections. One of the probable reasons for the In the accompanying list I have given You will not go far wrong if you follow clear tone of this receiver is the resistance the number of parts needed and their the diagrams in every detail. coupled method of amplifying after the size, all items being given a letter cor- A voltmeter (VM) is very useful in detector. To those who have not tried responding to the lettering on the draw- a five tube set for keeping the potential this system of increasing the signal ings so that their location can be quickly constant across the filaments as advised strength to loud speaker volume, this identified. by the makers of the tubes. As shown system will be a revelation. All distortion Assembly of Set in the diagrams, the voltmeter registers and transformer noises will be eliminated. the potential across the filaments of the If you are undecided as to whether cr not THIS receiver will assemble easily on radio frequency and reflex tubes, as you shall use resistance coupling, my a 7'x26' panel, and by a little crowd- these tubes are the most critical of the advice to you is to try it by all means. CO 4- SNd'/J1 as .». .aa-n.voJ3

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COMPACT portable radio receivers, ling requires no separate interstage con- having sufficient power to operate trols, but unfortunately, resistance coupon either loop or flat top aerial, are Controls are Simple ling in the radio frequency stages is only desirable for home use as well as for efficient on long wavelengths, say on camping and motoring trips. Provided and Operation Quiet wavelengths above 1,000 meters. This with self- contained batteries, such outfits resistance coupling method will be fine can be easily moved about from room to and this system must therefore be dis- for the audio stages, and is just What will room in the house or can be carried to the carded right at this point, both for the be used for the output, but we will have home of a friend to provide music for a reason that it takes up much room, and to guess again in regard to the coupling dance or for other similar occasions. The also for the reason that a separate dial on the R. F. end of the hookup. The portable has a much wider field of appli- control will be required for each radio untuned or fixed radio frequency trans- cation than the conventional, cumber- stage (and for the tuner unit in addition) former at once suggests itself, but for this some cabinet with external batteries, and which will bring the total number of time it must be rejected because of the should be seriously considered by those controls up to three or more. This is out space occupied and for the reason that who desire a receiver of the all-round type. of the question in a portable outfit; hence such transformers are likely to "back - For the sake of simplicity, such an we must look farther for a means of radio couple" between stages if crowded to outfit should be of the single control type, frequency stage coupling. We should gether as closely as we intend to crowd the or should not have more than two controls have only a single selective control for the stages of this outfit. at the most. It should have at least two tuner unit, and no variable controls after radio frequency stages for distance and the first stage that are represented by THERE is only one other coupling pos- for operation on a loop aerial, and at dials or knobs on the front of the panel. sible on the R. F. end, and that is least two audio frequency stages for loud by means of inductances of the "choke speaker operation. With transformer Resistance Coupling coil" order, which are connected into cir- coupling this means at least five tubes, Resistance coupling for the radio cuit just like the resistance units of a if the tubes are not reflexed, and we must frequency and audio frequency coup resistance coupled stages. One end of therefore carefully consider the methods the choke coil is connected to the plate of of coupling the stages to conserve space the tube, while the other end goes to the and to minimize the number of controls. THE RECEIVER FOR (+ B). The connection between the Dry batteries must be used for the fila- YOUR NEEDS first tube plate and the grid of the follow- ment "A" battery, and the type of tube This Summer's tendency will be ing tube is made through a fixed condenser must be such that not more than three for simplified radio receivers, with just as in the case of the resistance or four No. 6 dry cells will be required. compact parts and ease of operat- coupling scheme. The choke çoils must This, of course, suggests the "199" tube, tion and control. A radio¡ set have a very much higher inductance than which is ideal for a portable rig because of without these characteristics can- commonly used with radio frequency its low filament current consumption.and not be called up -to -date. tuning units. They should consist of small size. Five "199" tubes will take THE RADIO AGE ANNUAL for several thousand turns of very fine wire. 1925 contains several of these won- 5 x 0.06 =0.30 ampere which is not pro- der hookups that are easy to build, The secondary coil of an audio frequency hibitive for dry cell service, and the cells easy to operate and pleasant to transformer will be just about right for will last for a considerable length of time hear. The latest in portable sets as this purpose when standard 100 Milli- on such work. Six tubes will take: 6x0.06 well as the larger models are all in henry chokes cannot be obtained. The =0.36 ampere which is within reason. this new ANNUAL, which is yours inductive value must be sufficient to choke Transformer coupling between either for $1. Send your remittance now the high frequency plate current so the radio frequency or audio frequency if you want to have this radio back handbook with you on your vaca- that it will not shoot circuit back through stages takes up considerable room. If year ever -ready the R. F. transformers are of the "tuned" tion this as an the "B" battery connections, and at the radio guide. same time the coil resistance should not type then they must be spaced well apart $1 while they last. to prevent coupling back between stages, be sufficient to interfere with the supply Blueprints of the Six-Tube "Portatron" on Pages Following

John B. Rathbun, Originator of the Blueprints in this remarkable section, writes exclusively for RADIO AGE every month. RADIO AGE for August, 1925 The Magazine of the Hour 71 of continuous "B" battery current to the tained on the plate. The plate of tube tubes and increases their effectiveness. plate of the tube. The choke coil permits (T1) is coupled to the grid of the second At tube (T3) we have the detector tube the "B" battery current to pass to the R. F. tube (T2) through the fixed coup- which is connected into circuit by the plate, but chokes back the R. F. current. ling condenser (K1) which is ordinarily 0.00025 mf. fixed grid condenser (K2), and of 0.002 mf. capacity. This condenser the one megohm grid leak (GL1). As with Radio Frequency Amplification prevents the application of the plate all the other tubes, this is a "199" tube, THE application of the choke system voltage to the grid of (T2) and thus pre- but to prevent critical rheostat adjust- 1i to the first three tubes will be seen vents the high "B" voltage from paralyz- ments the plate is supplied with 45 volts ing this coil (CC) can by an intermediate in Fig. 1 and Fig. 2, where Fig. 1 is a tube. The choke tap at the "B" bat- schematic diagram using symbols, and be the secondary winding of an audio tery. From the detector tube on, all of the stages Fig. 2 is a picture wiring diagram. The transformer, and as will be seen, prevents are resistance coupled by the first will be of more service to the experi- the R. F. plate output from short circuit- 50,000 ohm resistances (Ml- M2 -M3) and enced builder in "doping out" the circuit, the grid leaks (GL2 - GL3 -GL4). The while the latter will show the novice how hand controlled rheostat is shown at (R) the wiring connections are actually made by which the detector filament can be For those who want greater controlled Fig. 3 is a front elevation accurately for any conditions. to the parts. For of the panel and cabinet, while Fig. 4 is a distance, Mr. Rathbun has de- use with "199" tubes, the resistance rear elevation showing the parts assem- signed the six tube portable, of (R) should be from 30 to 40 ohms, the former for bled at the rear of the panel. Fig. 3A is but with resistance coupled dry cell operation and the side of latter for use with storage cells. a sectional view as seen from one audio amplification shown in- the assemblage. Resistance Coupled Audio Taking Figs. 1 -2, we see that an aperi- stead of the transformer method odic type coupler is used at (L1 -L2) of coupling. ALL of the three audio frequency tubes which is tuned by vernier variable con- (T4-TS-T6) are supplied with the denser (Cl) connected across the second- The change lies with the full "B" battery voltage through the ary coil (L2) of the coupler. This can be builder. A great deal of space fixed resistances (Ml- M2 -M3) which have a home -made coupler such as has been may be saved by the use of a resistance of 50,000 ohms. The plates described many times in these columns; and grids of the tubes are connected by it can be a standard neutrodyne trans- resistance coupling and at the means of the fixed condensers (K3 -K4- former or else a standard adjustable same time it delivers good K5) of 0.005 mf. capacity. This value aperiodic tuner. In any event, the quality. is not critical, and 0.006 mf. fixed con- primary coil, (L1) is untuned. When the densers can also be used if this is the only usual flat top aerial is used, the aerial capacity to be found in stock at your lead -in wire is connected to (ANT) and radio store. They must be of the mica the ground wire at (GND), a system whch ng through the "B" battery. It allows dielectric type, or condensers in which the gives the greatest range and signal the "B" battery to go to the plate of the plates are separated by thin sheets of strength. By connecting the ends of a first tube, however, but stops the high mica insulation. loop aerial at (XI) and (GND), and then frequency current from backing out. The grid leaks (GL2, GL3, GL4) opening the grid switch (T), we can oper- This requires no control. of the audio tubes "taper" toward the ate on the loop aerial. The tap switch Filament Controls rear; that is, the last tube has a higher (T) cuts out the secondary coil (L2) leak resistance than that of the first which is necessary on loop reception. of the amplifying tubes, five in audio amplifying tube. (GL2) =1.0 Coil (L3) suppresses oscilations. ALtnumber, are provided with auto- megohm, (GL3) =5.00 megohm, and When operating on the flat top aerial, matic filament controls which maintain (GL4) =25.00 megohm. This arrange- or a type similar to the usual outdoor the amplifying tube current at the proper ment gives a stronger bias to the grids aerial, the coupling between the primary intensity without rheostats or other on the tubes which are most heavily (L1) and the secondary (L2) must be very manual controls. This is a decided step loaded, and therefore results in a better "loose;" that is, there must be a consider- toward simplicity and compactness, and distribution of amplification through the able space between the two coils. For this prolongs the life of the tubes by holding the three stages. The output of the sixth reason, it is best to adopt a ready -made filaments constantly at the proper temper- tube (T6) leads to the output jack (J1). coupler in which the coupling gap can be ature. A manual rheostat (R) of the A full 90 volts must be maintained on easily adjusted until the proper degree is usual form must be provided for the the plates of all amplifier tubes, and where found by experiment. We have only one detector tube (T3) as this has a rather possible, this should be increased to 112.5 control, and to obtain the proper selec- critical filament adjustment that cannot volts as the choke and resistance coupling tivity in local jams we must have the be automically controlled. The rheostat demands a higher voltage than the straight proper "looseness" between the coils. The (R) is represented on the front of the panel transformer coupling ordinarily used. home -made coil generally contains from by a knob as shown by Fig. 3, and is the Two vertical type 45 volt blocks will 12 to 15 turns of No. 26 D. S. C. wire on only control outside of the condenser dial take up the minimum amount of space the primary (L1), and from 55 to 60 turns (C1). A switch (SW) must be provided for in the cabinet when the batteries are on the secondary coil (L2), using the same shutting off the filament current when the carried in the cabinet, but a third small size wire. The distance between the two set is not in use. It is no longer possible to 22.5 volt block will greatly improve the coils, or the coupling, may be from ;b to turn off the amplifying tubes indepen- performance by raising the voltage to inch or even greater. dently as when the usual form of rheostat 112.5 volts. The great trouble with a By using a 4.5 volt three cell "C" bat- is used. This can be an ordinary battery portable set is to get the batteries into tery at (C), we usually get greater sensi- switch of the type to be found at any place without monopolizing all of the tivity and signal strength, and the battery radio store. cabinet space. When the set is built for also reduces the tendency towards free A second choke coil (CC) is shown con- ordinary stationary service, then we can oscillations in the circuit. However, the nected to the plate circuit of the second use three 45 volt blocks of "B" battery, "C" battery can be omitted in many radio tube (T2), and as this is exactly giving 135 volts, and will thus obtain cases without serious loss. The switch similar to the first, there will be no further the maximum output of the tubes. The (T) can be the usual form of tap switch comment. The output of tube (T2) leads small size "B" batteries must be used with one active contact point, and one to the detector tube through the 0.00025 for the portable set. dead contact. mf. grid condenser (K2). It should be Filament or "A" batteries are to be The first radio frequency tube (T1), noted that a one megohm grid leak (V), No. 6 cells and are connected up in series which follows the tuning inductance, is shown dotted on the grid of tube (T2), to give a total of 4.5 volts across the provided with the choke coil (CC) con- will often prove of advantage. It should at rheostat. When possible, these should nected to the plate at one end and to the least be tried out in the position indicated be square batteries so that the maximum ( +B) line at the other, so that from 90 by the dotted lines before completing the amount of battery material can be put to 135 volts of "B" battery will be main- set, for it sometimes stabilizes the first into a minimum of space. The demand 72 RADIO AGE for August, 1925 The Magazine of the Hour of the six tubes is slightly greater than THE finish of the cabinet depends when built of 5 -16 inch stock. The that ordinarily recommended for con- upon the taste and ingenuity of the bakelite panels should not be less than tinuous service (0.36 ampere), but builder. It can be polished with wax or 3 -16 inch and this also covers the shelves with careful handling they can be made varnished in natural wood finish, or which should be of the same material to last for a long time before replacement it can be covered with leatherette or as the panels; that is, hard rubber, bake- becomes necessary. similar black grained covering material. lite or formica. The shelves carry the If leatherette is used, then all of the wiring and many of the current carrying Reason for Six Tubes corners must be well rounded off so that parts so that their insulating value should WITH transformer coupling on both the material will not get loose or buckle be fully equal to that of the panels. radio frequency and audio frequency along the edges. The front face of the We cannot go further into the details stages, a five tube set is commonly built battery compartment door comes flush of the cabinet construction, but the con- with two radio stages, detector, and two with the face of the cabinet and struction will be clearly seen by those audio stages. With choke coils in the panel door; hence this part is given the who are competent to undertake work radio stages and resistance coupling in same finish as the outside of the cabinet. of this sort, and if one is not sure of being the audio stages, the amplifying power Rubber pads or feet (i) prevent the set able to build this cabinet, the drawings of the tubes is somewhat reduced so are amply dimensioned for a practica that one more tube will be required to cabinet maker. If you give the job to give the same results. However, this is BILL OF MATERIALS USED a cabinet maker, I suggest that you also Tho following list will give the materials used and their give him more than compensated for by the sim- sises The parts are listed according to the ea refer- the panels and shelves so that plicity of the controls and the clear ence letters used on the drawings so that their relation he can get a good fit betwen the edges n be seen at a glance. of the panel toned, noiseless operation of the set. PORTABLE RECEIVER MATERIALS and the rabbet of the cabinet It has a far better tone than with the "A " -3 Filament "A" Dry Batteries. 1.5 volt. No. 6. ANT-1 Loop aerial (optional), 2 Ft. Square. Arrangement of Apparatus usual arrangements and can be handled B "-2 '$" Plate Batteries, Vertical type, 45 Volt "C"-1 "C" Sim Battery, Three cell. small, 4.5 volts FIG. by the rawest novice in radio. C1 -1 Vernier Variable Condenser (23 plats), 0.0005 mf 4 shows the arrangement óf the 3, CC-2 100 Millihenry Choke coils, or audio tram - seen Fig. showing the front elevation of former secondary coils. apparatus as from the rear of the the panel and cabinet, gives a good idea D-1 Special cabinet, as specified in drawings panel. The six tube sockets (U) are E-1 Special Panel. as specified in drawings, 3/15 -inch of the general arrangement of the Bakelite. placed in groups of three on the two F -H-2 Special Shelves. as specified in drawings, 3 -15 receiver when designed as a portable set. inch Bakelite 5ez534 shelves (F) and (H), and the outlines o G-1 Carrying Handle Complete, Standard. the The cabinet is really divided into two GL1 -1 Crid Leak. 1.00 Mecohm. tubes are indicated by thin dot and parts, (1) the upper portion covered by GL2-1 Crid Leak. 1.00 Mechem. dash lines so that the allowance GL8 -1Grid Leak 5.00 Megohm. for shel the panel being for the radio circuit G14-1 Odd Leak, 25.00 Megohm. clearance can be easily seen. The tubes h-4 Hinges or butts. Standard. proper while (2) the lower compartment I -2 Lock Catch, Standard. are numbered so that their relation to 1.--4 Rubber pads of feet. Medium Size. houses the "A" and "B" batteries. As J1 -1 Single Circuit Jack, Standard. the circuit drawings of Figs. 1 and 2 can K1 -1 Fixed Condenser, Mica dielectric. 0.002 mf. be this is a special arrangement, the cabinet K2-1 Fixed Condenser, Mica dielectric. Grid clips. easily followed, and the sockets can and panel will have to be made specially 0.00025 rat. be located in the same way. Fig. 3A K3 -1 Fixed Condenser. Slice dielecrlo. 0.005 or for the job and it is not likely that a ready- 0.006 ml. and Fig. 4 can be used in combination K4-1 Fixed Condenser. Min dielectric, 0.005 or made cabinet or panel can be found which 0.006 ml. thus obtaining the side and rear eleva K5-1 Fixed Condenser. Mica dielectric. 0.005 or will exactly fit the conditions. 0.006 mt. tions of the assembly. 3 we see L-4 Braes Angle Brackets. Standard. will In the front view of Fig. that Ll -L2 -1 Aperiodic Type Coupler. Standard. It be seen that the shelves are cut the panel contains all of the controls, Ml -M2. 513-350.000 ohm Resistor Unite. off at the right in Fig. 4 to accommodate R-1 Filament Rheostat. 30-40 ohms. and also the three binding posts for the r1 -r2, etc. -3 Automatic Fila. Controle (Amperita) the variable tuning condenser (C1) and 109 -4.5 volts. aerial (ANT- XI -GND). The dial of the SW-1 Battery Switch. Standard. the tuning inductance (L1 -L2). On T -1 Tap Switch. Standard. tuning condenser is at (C1), and for t-2 Contact pointe, with two stops, Standard. the lower sides of the shelves will be seen this should be a four -inch dial Tl -T2. stn. -5 Tubes. "199." the coupling resistances, grid accuracy U-6 Absorber Base Tube Sockets. "199" Type. condenser with some sort of vernier arrangement, 40' Tinned Square Copper Bus Wire. No. 14. gridleaks and the wiring. In making 75 Solder Clips. Tinned. Standard. as the tuning -is exceedingly sharp. 3 Binding Posts. Composition Caps. Standard. allowance for the space between shelves Z-4 Brass angle connections. Standard. The rheostat control (R) for the detector V -1 Leak. 1 megohm. measure the height of the tube plus the tube is at the right of the condenser dial. FM-Filament voltmeter. 0.8 volte. height of the socket, plus a little more The battery switch for turning the "A" clearance so that the tubes can be taken battery current on and off is at "SW" out of the sockets and replaced without and the output jack is (J1). In the rom scratching finished surfaces on which tearing the set to pieces. In other words, upper right hand corner of the panel is 't may be placed, and further, they the true height of the socket assembly the grid switch (T) by which the set prevent or help to prevent, the ringing is the sum of the tube height, plus the can be thrown over from flat top aerial microphonic noises experienced with socket height, plus 3 inch clearance to loop operation. This is all there is "199" tubes. between the lower end of the tube and to the control of the set and its external Shelf for Tubes the top of the socket. connections. The side sectional view of Fig. 3A shows The arrangement of the battery corn As will be seen from the side sectional that a shelf (F) is used for carrying the partment in general with the batterie view, Fig. 3A, the panel is set back from first three tubes, and that this shelf is in place is marked. Strong fiat springs the front edge of the cabinet so that the attached to the panel (E) by means of made from flat spring brass plates bear front door will clear the knobs and dials. brass angle brackets (L). The shelf (F) on one side of the batteries and hold them The door swings on two hinges (h) and carries the first two tubes (T1 -T2) of in place against jolts and jars when the is just large enough to cover the panel, the radio frequency circuit and also the set is being carried. Connections between the top of the battery compartment detector tube (T3). Below the upper the apparatus and batteries are made by being at the lower edge of the door. shelf is the lower shelf (H) which carries means of flexible fixture wire which can Any suitable catch or lock (I) can be the three audio tubes (T4-T.5--T6). As be obtained from any electrical store used on the left hand edge of the the resistance units and other parts of This is very flexible and well insulated cabinet for fastening the door, and a the circuit are carried on the underside and makes an ideal connection.. The ends lock is not a bad idea even in the home, of the shelves with the sockets on top, of the fixture wire should be provided as it prevents children from tampering we must be sure to leave room to accom- with "spade" type tips soldered to the with the set. At the top is a leather modate the height of the tubes over copper strands, and these make a perman handle (G) fastened to the cabinet by their sockets, plus the thickness or height ent contact with the connection screws standard hardware that can easily be of the resistance units and the condensers, which is easily attached and which does obtained from a trunk or suitcase house plus clearance. not loosen under ordinary conditions or from some hardware stores. The lower The material used for the cabinet can Do not attempt placing the strands of battery compartment door, just below the be 5 -16 inch or 3 -8 inch thick, but if care- wire directly under the binding screws, panel, is shown closed. It is through this fully constructed with dovetailed or for when connected up in this way they opening that we replace the batteries. matched corners, will be perfectly safe are almost certain to get undone. Blueprints of the Six -Tube "Portatron" on Pages Following RADIO AGE for August, 1925 The Magazine of the Hour Lconomy of Arrangement Is Vital AS WILL be seen, the part of the center of the graduated scale where arrangement, and there are no separate assembly taken up by the receiver the divisions are the largest, and the controls as when a potentiometer is used. proper is very small, the panel measuring battery voltage should not throw the In addition to the compensating coil 104 long and 11.kg deep, but for some needle to the far end of the scale. (L3), the "C" battery will be an aid in purposes the total height with the keeping down oscillations and increasing batteries included may be too great to Suppressing Oscillations the sensitivity of the first two tubes. be practicable. In such a case, the In the center, and at the bottom of battery compartment can be made Free oscillations in the radio fre- Fig. 1, will be found a detail of a small separate, terminating the receiver por- quency stages are the greatest difficulty radio frequency choke coil which can tion at the board shown running over in the construction of a radio frequency be used when an audio frequency trans- the tops of the batteries. This, however, or reflex type of receiver, and we must former secondary is not available. This for makes it necessary to reconnect the bat - devise some system stopping these consists of about 450 turns of No. 36 terieseverytimethat the receiver is set up oscillations if we expect to get the full D. S. C. wire wound on a cardboard and as a result it is a decided nuisance. output of the set. In fact, most of the or bakelite tube as shown, and is mounted As laid out in the drawings, there is trouble reported with sets having radio on the upper shelf (F) of the set. Some ample room for a fifth "B" battery if frequency stages can be traced to im- little experimenting may be required it is desired to operate with a plate proper or imperfect methods of damping to get the most effective number of voltage of 11234 volts, or a sixth "B" down the oscillations. There are a turns, but the coil is not very critical battery if we wish to operate at 135 number of methods of stopping oscilla- to the turns, and for most apparatus the volts. Further, there is room for one tions, among which are the potentio- number of turns shown will come very spare "A" battery if it is desired to carry meter, neutralizing condensers, bias bat- close to the best effect. We must have this replacement along on a trip. teries, etc., but in this receiver we have sim- enough turns so that the tubes will not The voltmeter (VM) is. a very desir- plified the problem by the use of a plate re- paralyze on the higher wavelengths able instrument, particularly when dry actacne coil marked (L3) on the diagrams. through leakage of the R. F. current cell "A" batteries are used, for it at Coil (L3) consists of four or five turns to the '"B" battery. once indicates. the drop in voltage due of wire wound on the end of the tuning In the lower right hand corner of to weakening batteries. Unless we have coil. One end of this coil is connected Fig. 1 is a detail of the resistor assembly some means of testing the voltage to the plate of the first radio tube as used in the audio frequency stages. occasionally, we are likely to believe shown, while the other end is left opened We can assemble the resistors and grid that the set is out of order when the or is unconnected. As one end is opened, leaks on the shelves by means of clips voltage drops, and waste mtich time only capacitative current will flow from as shown, or better yet, we can buy chasing for trouble in the wiring when the plate into the coil, and the magnetic these completely assembled units from the difficulty actually exists in the coupling is therefore very feeble, as it our advertisers, at a reasonable figure. cells. Just because automatic filament should be. Some little experimenting controls are installed for the regulation will be required in adjusting this coil Summary of the filament current is no reason before it just stops the oscillations. why the voltmeter should be omitted. It may be that the plate connection IN tuning this set, the adjustment of Voltmeters must be connected properly must be connected to the other end of the detector rheostat (R) is of great according to polarity, and you must (L3), or that the whole coil must be importance, for there is one position be guided by the markings on the instru- wrapped on the other end of the tube. of the rheostat where the detector tube ment. If the polarity is wrong, then Varying the number of turns, or the is the most sensitive and gives the the needle indicator will be thrown distance of (L3) from (L2) may be greatest volume. This generally occurs against the wrong end of the scale. required. Just because you have not when the rheostat is about one -half on, The size of the voltmeter should be so hit the proper combination on the first and it is seldom necessary to turn on chosen that the full voltage will bring trial is no proof that it will not work. this tube to full brilliance as with the the needle near or slightly beyond the The losses are at a minimum with this amplifier tubes.

LET OUR HOOKUPS BE YOUR GUIDE IN RADIO AGE The Magazine of the Hour Let America's best known radio experts keep you informed of the latest in technical radio. Here are a few of the radio men who write for RADIO AGE monthly: John B. Rathbun, Frank D. Pearne, Edmund H. Eitel, Paul Green, Brainard Foote, H. Frank Hopkins, Armstrong Perry, McMurdo Silver, Roscoe Bundy, Arthur McCullah, and many others. RADIO AGE is the Only Magazine in which you can find Real Radio Blueprints every month. The RADIO AGE blueprint section, begun in September, 1924, has attracted world -wide comment. The eight -page blueprint section in the monthly RADIO AGE is worth many times the yearly subscription rate. ALSO A BIG STUDIO -LAND FEATURE SECTION about your favorite Radio Stars and stations in every issue. Subscribe Now -Only $2.50 a Year On the News -Stands the 15th of Every Month -25c. a Copy :5 ®

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8 78 RADIO AGE for August, 1925 The Magazine of the Hour Here You Are! A Real Receiver A New 8 -Tube Super- Heterodyne By JOHN B. RATHBUN

SO much has been printed in RADIO less of the incoming radio frequency. AGE upon the elementary prin- The oscillator condenser forms one of ciples of the superheterodyne that it A Super That Gives the two tuning controls of the circuit. seems hardly necessary to enter again into the theory in much detail. Distance and Tone The R. F. Transformers heterodyne Briefly, the super- is a ALL of the radio frequency trans- special form of radio frequency circuit first stages of the circuit. It should be formers operate at a constant fixed in which radio frequency amplification noted that the R. F. tubes and trans- wavelength or frequency at which maxi- takes place at a much longer wavelength formers work normally at a frequency mum amplification takes place, regard- than that of the incoming radio waves, which is not very much greater than the less of the frequency of the broadcasting thus reducing the losses in the tubes and higher audio or voice frequencies, and station which may then be tuned in. This R. F. transformers and adding to the therefore a certain amount of audio optimum frequency is determined by the efficiency of the set. Broadcasting wave- amplification is also possible in the radio windings of the transformers and more lengths ranging from 200 to 600 meters stages, when iron core transformers are particularly by the filter condensers are converted into wavelengths approxi- used at this point. With air core trans- placed across the first or last R. F. mating 10,000 meters before the waves formers receives transformers. The frequency stages. the audio component transformers are enter the radio After little if any amplification in the radio therefore sharply tuned to a single definite amplification, the waves then are rectified stages, and hence under these conditions wavelength or frequency to which the by the usual detector tube producing the rectification of the first tube (1) is heterodyned waves must be adjusted which audible signals can be further not of importance and can be considered by means of the oscillator variable, con- by or more audio stages. amplified one and used as a strictly radio frequency denser. As the transformers will not A typical eight tube super -heterodyne stage. The advantages and disad- respond to any other frequency than that of the type to be described consists of vantages of either system are still a matter determined by the filter, the oscillator the following principal unit divisions of of some dispute. condenser becomes an effective tuning tubes: We now come to the oscillator tube (3) control, which in connection with the (1) The first detector tube. by which the wavelength or frequency aerial or loop condenser insures a high (2) Three radio frequency amplifying of the incoming waves is converted into degree of selectivity. tubes. the desired value for use in the radio All the radio frequency transformers, (3) One oscillator tube used as a fre- frequency stages. Really this tube is an whether of the air core or iron core type, quency changer of the heterodyne type. independent unit as far as the rest of the are of the "long wave" design especially (4) One second detector for rectifying circuit is concerned, for it does not enter designed for the super -heterodyne cir- the output of the radio frequency stages directly into the amplification or rectifi- cuit. In the circuit illustrated, the and thus producing audible signals. cation of the waves. It simply produces transformers are designed for operation (5) Two audio frequency stages for a series of independent, continuous on approximately 45 kilocycles (45,000 increasing the volume of the audio com- oscillations, which are combined with the cycles frequency) which corresponds to a ponent so that a loud speaker can be incoming radio waves to form a third wavelength of 6,000 meters. This is used. series of oscillations having a greater not a fixed standard frequency which The Detector Tube wavelength or lower frequency than must be maintained strictly in all cases, IN a certain respect, the first detector either of the original series. This method but has been found in practice as the most tube (1) can be considered as a radio of changing frequencies is known as effective compromise for the circuit at frequency amplifying stage, and in some heterodyning. The third wave is ampli- hand. Actually, the waveband may circuits is used exclusively for this pur- fied by the succeeding radio stages. extend from 1,200 to 25,000 meters in pose without the conventional grid con- The frequency of the oscillations set up many circuits, but at either extreme cer- denser and leak, but when iron core by the oscillator tube is determined by an tain objectionable features appear which radio frequency transformers are used inductance coil and a variable condenser make the 6,000 meter type the logical the detector tube is of advantage in in such a way that a constant frequency compromise for iron core transformers. providing an audio component in the is maintained in the R. F. stages, regard- (Turn the page) Blueprints for the New Super -Heterodyne on Pages Following

Like a Woman's Heart - Always room for one more subscriber in the RADIO AGE family. Each month prizes are to be given for those who send in the largest number of paid up yearly subscriptions to this magazine. Details of the contest are to be found on page 18. Summer -time is the time to go after your prospects; neither you nor the other fellow is too busy. And with this DeLuxe edition as a fore- runner of the good things you may expect form RADIO AGE in the future, you should have no difficulty in bringing more radio recruits into the ranks. RADIO AGE for August, 1925 The Magazine of the Hour 79 Uniformity of Tubes Vital in "Super" Circuit Diagrams controls used and therefore the actual outer tube is 2.5 inches in diameter and operation of tuning is much simpler than carries both the grid and plate coils of Fig. I is the schematic circuit drawing with the usual tuned radio frequency set. the oscillator circuit. The grid coil of the superheterodyne developed by we four carries 20 turns of No. 26 D. S. C. wire Mr. Posth of the Radio Doctors, Inc., Further along the panel have filament control rheostats (R1- R2 -R3) and the plate coil consists of 40 turns of Chicago, and which has been built by a with resistances varying according to the the same size wire. The latter is spaced of with excellent number amateurs number of that they about one half inch from the grid coil. results. is not a radical departure from tubes control. It Rheostats are based on the use of 201A A detail of the oscillator coil is shown in conventional practice, but is a simple, tubes throughout both for the amplifiers Fig. 4 where the external plate and grid compact layout which is easily con- and detectors. The three rheostats coils are clearly seen. The inner and outer structed by the novice in "dyne" cir- marked (R1) have a resistance of 20 oh ms tubes are mechanically connected by short cuits with an excellent chance of getting the pieces of small fiber tubing through which results immediately after the completion and control respectively oscillator tube (1), the first detector tube (2) and brass screws are run. When tuned by the of the set. It is the result of nearly a the second detector tube (6). Rheostat 0.0005 mf condenser (C1), this oscillator year's continual experimenting by one (R2) controls the three radio frequency will fully cover the ordinary range of who has alternately added and then broadcasting wavelengths. eliminated various experimental features tubes (3 -4-5), and because of the greater current has resistance of only six ohms. At (2) we have first which have been brought up from time a the detector tube Rheostat (R3) has a resistance of 15 ohms with the grid condenser (K2) to time in development of 0.00025 heterodyne for the control of the two audio tubes mf capacity and the grid leak (GL) until the present circuit was arrived at. with (7 -8). a resistance of two megohms. As will be Fig. 2 is a picture diagram of the hook- Watching Potentiometer seen from the plan view in Fig. 2, the up which will be of service to those who oscillator coil and the two tubes (1) and have not yet delved into the mysteries AT (PO) is a 400 ohm potentiometer or of which (2) are located well back on the base- conventional diagrams. Here each part stabilizer controls the grid potential of the radio frequency stages. board, so as to clear the variable con- is drawn out as it actually appears in the densers (C1 -C2) indicated by the dotted proper proportion, with wiring runs In actual operation the potentiometer the has lines. The outline of the baseboard is located at the most advantageous points. a marked influence on the volume and indicated selectivity but is not frequently used by (F). A bypass condenser The letters and figures on Fig. 1 cor- (K1) has a 0.005 after the set is set into operation in the capacity of mf. respond to those marked on Fig. 2, so Next in order come the radio frequency that the relation between the two draw- same sense that the condensers are used. A potentiometer lower stages consisting of the tubes (3), (4), ings can be easily traced out. For con- of resistance is not recommended, as it does not give (5) and the long wave radio transformers venience, Fig. 2 is divided into two parts. (RD1- RD2 -RD3 -RD4). All of the trans- lower half drawing sufficiently accurate control of the grid The of the represents formers are of the iron core 45 kilocycle a plan view of the baseboard potential. A voltmeter (VM) is desirable and appa- for indicating type and are tuned to work in agreement ratus as it appears to the observer on the potential across the filaments of the radio tubes, but it is not with the oscillator by means of the fixed looking straight down on the set. The condensers (Kl -K4). (RD1) is the input upper half is the rear view of the panel absolutely essential. By means of this voltmeter (0 and (RD4) is the output transformer. as seen from the rear of the assembly. -10 volt scale), the tubes can be kept to Any iron core of 45 kilocycle type can be Between the upper and lower views we accurately the point of great- sensitivity. An employed. Condenser (K4) has a ca- see the wiring in est ammeter, shown connecting drawn heavy gives pacity of 0.00025 mf. Owing to the body lines, which the by (AM) the total current consumed connect apparatus in capacity which is sometimes in evidence, mounted on by all tubes the circuit. A battery the baseboard to that switch (SW) is it is frequently desirable to ground the attached to the rear of the panel. as at very convenient Ar- and is an insurance against the accidental metal cases of the transformers as indi- ranged in this way, the connections are cated by the dotted line (g). easily followed. burning of the tubes after leaving the set for the night. It makes the complete With the particular transformers shown Fig. 3 is a front elevation of the panel readjustment of the rheostats unneces- in Fig. 2, the tube sockets and trans- which shows the controls and the center sary when the set is used the second formers can be set very close together, to center dimensions between the various time. All of the above apparatus is about 2 7/8 inch centers. The trans- units mounted on the panel. As will be mounted on the panel as shown by the formers are of the metal shielded upright seen from the blueprints, the panel is upper view of Fig. 2. cylindrical type, which lend themselves 8'x32'x1/4', a reasonable size for a Three output jacks are provided. nicely to compact formation. The grid super-heterodyne and a panel not much Inserting the plug into jack (JD) gives post (G) of the output transformer longer than that used with many tuned reception from the tubes up to and in- (RD4) goes to the grid condenser (K5) radio frequency outfits. The circuit is cluding the first detector tube (6) and grid leak (GL) of the second detector for with and arranged exclusively use a loop this corresponds to the detector tube tube (6). The grid condenser (K5) has a aerial, and with this arrangement the circuit of the ordinary regenerative capacity of 0.0005 mf, while the grid loop plays no small part in gaining circuit. Plugging into jack (JI) gives leak has a resistance of 2 megohms. absolute selectivity in districts where the addition of one stage of audio ampli- there are a number of broadcasting fication, while jack (J2) includes all of 201A Tubes Used stations located within a short distance the tubes or two stages of audio. Ex- of the receiver. BY using 201A tubes throughout with perience has shown that one stage of a current consumption of 0.25 Starting in with either Fig. 1 or Fig. 2, audio is all that is required for loud ampere per tube, the total current is only depending upon the experience of the speaker operation on all but the faintest 8x0.25 -2 amperes, the exact amount reader, we note the two variable con- and most distant stations. of current taken by a five tube neutrodyne densers (C1) and (C2) mounted on the An oscillator coil (OS) of the fixed when a soft detector tube is used. As a panel at the right. Both are of the low winding type is located between the first soft detector of the "200" type takes loss type with external vernier adjust- detector tube (2) and the oscillator tube about one ampere and introduces a cer- ments, and both have a maximum capaci- (1). The functions of this inductance tain amount of hissing tube noise, its ty of 0.0005 microfarad or the capacity of coil have been described before. This use is not recommended in this set. the standard 23 plate. Condenser (CI) coil is very compact and requires no Owing to the high potentials on the grids controls the oscillation frequency of the adjustment. The inside bakelite tube of the tubes, it is necessary to use the oscillator tube (1) and the oscillator coil is 1.5 inch in diameter and carries about highest grade of sockets to insure against (OS). Condenser (C2) tunes the loop four turns of wire near its center which leakage and internal capacity effects. and the grid circuit of the first detector corresponds to the "pick -up coil" of the For the same reason, the bottoms of the tube (2). These are the only tuning usual heterodyne oscillator coil. The sockets should be raised well above the 80 RADIO AGE for August, 1925 The Magazine of the Hour face of the baseboard by means of spacers mf. while (K8) is a 0.001 mf. size. care that the parts are actually soldered or liners, say about 1/4 to 3/8 inch above Another filter fixed condenser (K4) is and not simply stuck together with the the board. connected between the grid (G) and the non -conducting rosin flux. After solder- For the best results all tubes should be ( -) post of the "C" battery at (K4) and ing, shake the wire vigorously to make carefully matched by the dealer before has a capacity of 0.00025 mf. This com- certain that the parts are soldered. In delivery, for all of the tubes in the radio pletes the audio frequency stages except such a complicated set, it is exceeding frequency stages at least must have for the three jacks (JD- J1 -J2) which are difficult to trace trouble when due to exactly the same electrical characteristics. interconnected with the stages as shown. open joints, hence we must be vigilant during the wiring operations. When so many radio frequency tubes are The Loop Connections connected up in cascade (series), and when Tubes should be matched by the the transformers are exactly matched as At the extreme upper right hand corner dealer so that all of the radio frequency they should be, any small difference in of the panel in Fig. 2 are the two binding tubes are electrically identical. If this the tube characteristics will cut down the posts for the loop connection. It is best is not done, then it will be impossible output to an alarming extent. Matched to use binding posts and to avoid the to secure maximum amplification in the tubes may cost slightly more than tubes use of a jack at this point as a jack in- radio stages. Much of the success with taken out of stock at random, but they troduces objectionable capacity into the a super -heterodyne circuit depends upon are well worth the money. Any one who circuit and also permits of some leakage the accuracy with which the transformers has constructed a neutrodyne set knows of the already weak radio impulses. As are matched and their agreement with how greatly tubes of the same make and explained, the set is somewhat more sen- the tubes. When the transformers are type vary among each other, and how sitive and selective if the lower binding successively numbered from the input difficult it is to get dissimilar tubes to post is grounded, or if the ( +A) line is through to the output transformer, they act together. grounded. This ground can be made must then be arranged in numerical order as shown by RD -1, RD -2, RD -3 fixed must be directly from the post or from some more Large bypass condensers and RD -4. used to shunt the radio frequency cur- convenient point in the circuit as at the rents around the windings of the poten- ( +A) binding post. This effect is parti- For the convenience of the builder tiometer and across the resistance of the cularly noticeable in cities where the the "A" and "B" battery connections "B" batteries. This is even of more radio traffic is congested and where the are made according to two different importance with long wavelengths than utmost in selectivity is necessary. systems. In Fig. 1 the negative "B" at broadcasting frequencies and the ca- In regard to the "B" batteries it must ( -B) is connected to the positive "A" pacities of the condensers must be cor- be noted that the demand for plate cur- ( +A), and in general this will give the respondingly greater. Condenser (K3) rent is very heavy and that for the best best results. The connections can be, has a capacity of 0.5 microfarad and is service a storage "B" battery is highly seen at the extreme right of Fig. 1 at used to shunt the R.F. current around desirable. If a storage "B" is out of the the terminals. However, under certain the potentiometer windings. Fixed con- question with the user, then only the conditions it is better to connect ( -A) denser (K6) has a capacity of 1.0 micro - largest size of dry batteries are advisable. to ( -B) as in Fig. 2. Either connection farad and shunts the "B" battery. The eight tubes will run down a small or is easily had without labor. by changing Smaller condensers should not be used. medium size "B" battery in a very short the cross connection or "jumper wire" time and in the end, the smaller dry cell Last are the two audio frequency at the terminal board. In the first case, batteries will prove much more expensive the jumper in Fig. 1 runs from the ( stages at the extreme left of the board. -B) than storage batteries or large dry bat- terminal to the ( terminal. In Fig. Tubes (7) and (8) are the first and +A) teries. A full 90 volts should be main- 2 this is switched from ( +A) so second audio tubes respectively, while that the tained at all times for the maximum out- ( terminal is connected the audio frequency transformers will -B) to the put, and much of the trouble experienced ( -A) terminal. This is simple, and we be seen (AT). In general, these at with super - heterodynes can be traced to same should try out to find which is best. two audio stages are the as any exhausted "B" batteries which have been In connecting the ammeter volt- stages but owing to the nature of and audio allowed to outlive their usefulness. meter, we must observe the polarity superheterodyne, it is necessary to the At the left of the baseboard will be marked is, filter the by means of certain on these instruments; that output seen the terminal strip of bakelite on the wire from the positive bus must fixed so the second stage go condensers that which the battery binding posts are of can be worked without noise and dis- to the positive terminal the instru- mounted. This is 1 1/4 inch wide and 6 If To use these stages ments. these connections are reversed, tortion. "straight" inches long with thickness of 3/16 inch. without filters means trouble as soon as a then the instruments will have the needle Wires to the connections run off through zero stop the output is taken from the second stage come to rest on the and will not (J2). Any the side or back of the cabinet, and this indicate the current or voltage. In through the jack high grade makes a much neater arrangement up the audio frequency transformer can be used than connecting transformers, the with the binding posts mounted on the on purpose. The ratio of first marks the transformer posts should for this the front of the panel as we sometimes stage should preferably be from 3/1 to see be observed, the grid (G) on the trans- such sets. Spacers are placed beneath former being connected to grid (G) 4/1 while the ratio of the second stage the terminal strip to raise it well 1 be 5/1 6/1. Higher the above of the socket as shown in both Figs. -2. transformer can to the bottom board and so ratios are general not advisable. that the screw Particular care should be taken to heads will not make contact with the connect up the variable condensers so Grid biasing by means of the "C" bat- wooden bottom board. Wood is not a that the connections between the grid tery is most essential to the proper perfect insulator and therefore we should of the tube and the stator (stationary operation of the set. It at once promotes avoid placing any current carrying parts plates) are always observed. If the grid clarity of tone and effects a saving of "B" in contact with it. is connected to the rotor or movable battery current in the audio frequency While spaghetti can be used with plates, then we will have trouble from tubes. For a plate potential of 90 volts, profit on all "A" battery and ground body capacity effect, as the full. grid a three cell 4.5 volt "C" battery will give wires, its use is not advised on wiring potential is then carried out to the hands the best results with the 201A tubes. which carries radio frequency currents, through the condenser shaft. The proper There is no current drain to speak of on except at points where a short length is connections are clearly shown in Fig. 2. this battery and it can be the smallest necessary to prevent actual short circuits. In order to absorb undesirable vibra- type of three cell battery procurable. Spaghetti has a high dielectric value and tions from the radio stages, a grid leak While most high grade audio transformers increases the capacity of the circuits (1 megohm) is connected across between are well shielded, yet it is safest to place with attending losses. the negative of "C" and the grid of the them at right angles to one another as last audio tube so that the leak (GL) shown in Fig. 2. This eliminates any T GOES without saying that all joints and the condenser (K2) form the con- danger of noise or interference. must be soldered and that particular ventional grid leak and condenser. This Two fixed condensers are connected care must be taken where soldered con- has a notable effect in reducing noise across the primary and secondary of the nections are made to the jacks. Rosin when the second stage of audio is thrown first stage audio transformer (AT1). flux must be used exclusively (no acid) in. The negative of the "C" battery Condenser (K4) has a capacity of 0.00025 and in using the rosin one must take must go to the grid (G) as shown. O

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ia ' II *, ari r. l. h ttl- +i -°uruor`..._ . . . . .s _ .,?. . uwwus+&°"°4 Silver Super Wins Grand Prize Stemm Assumes New Signal Holds Sales at Los Angeles Show Duties Conference Against a field of more than 400 set - Royal A. Stemm, who has for the last The annual sales conference of the builders, including scores of radio ex- two and a half years beén the Illinois Signal Electric Manufacturing Company, perts and engineers, an 18- year -old representative for the Crosley Radio of Menominee, Michigan, was held builder of a Silver Super -Heterodyne Corp. has tendered his resignation to this May 18th -22nd. Twenty -one represen- carried away first honors in the Grand company, effective June the first, and will tatives from all over the United States Sweepstake Contest conducted at the immediately assume his duties as Presi- and Canada were brought to the factory National Automotive School Radio Show dent of the Jackson Sales Company, 20 for five days of business and pleasure. in Los Angeles, June 7. East Jackson Boulevard, Chicago. Business in the morning, fishing, boating The prize was a $300 cash award, Mr. Stemm has been intimately and dancing in afternoon and evening. offered for the finest set in the entire associated with radio in its various Before the conference opened the rep- contest, which was held in conjunction phases since its first inception as a com- resentatives took a tour through the with the radio show. The youthful mercial product and has always forcibly factory, which covers 42,380 square feet winner was Robert Haig, of 8123 Norton and effectively played his part along of floor space, and were shown how Sig- Ave., West Hollywood, Calif., and the the tangents that are for the betterment nal Quality Products were manufactured super -he°- '+dyne with which he won the of radio and its merchandising problems. and each one assembled a Signal Jr. grand prize was built from the circuit "Royal ", as he is known among his inti- Fan, which has proved a big winner this developed by McMurdo Silver, Assoc., mates, has by his energetic and pleasing year. I. R. E., whose work in superheterodyne personality won a large coterie of friends, The conference was called to order and transformer development is nation- both in the social and business world of at 10:00 a. m. by Charles E. Hammond, ally known and recognized. Silver- radio. general manager, and first expressed his i Marshall super parts, also developed The many messages of congratulations appreciation for the good work "The and designed by Mr. Silver, were used and good wishes already received, demon- Boys" had done during the past year. exclusively in Mr. Haig's prize receiver. strate his popularity in the trade and He next introduced William E. Hopper, The award was judged on distance, it is predicted that in his new and larger the newly appointed sales manager. quality of tone and selectivity, by three fields of activity, he will be much The present items of the line were of the best informed radio engineers and heard of throughout the middle west first discussed and then the new ones editors in the industry. The set was a territory. were introduced. These newly introduced portable model Silver -Super, a seven - The Jackson Sales Company, which items were received with great enthu- tube outfit on a 7" by 18" panel. was organized over a year ago, are the siasm and the unanimous opinion of Of the total of 432 sets entered in the exclusive Manufacturer's representa- sales force was that "Signal Would contest, eighty -three were super- hetero- tive of the well known Air Way Receivers Enjoy Wonderful Business" on all its dynes, built by some of the best known for the States of Illinois, Wisconsin, lines, but especially on the new items, super -heterodyne experts in the country. Minnesota, the Dakotas and the upper which are "world beaters." More than 40,000 radio fans attended peninsula of Michigan. They also repre- The new items introduced were: a the exhibition. sent the Wireless Dry Cells Ltd., Niagara new loop, variable condenser, a complete In thanking the judges for the grand Falls, manufacturers of Maximite "A," line of A. C. and D. C. bells, exhaust prize, young Haig said: "B," and "C" Batteries, and operators of fans, new bell ringing transformer, fac- "I have built more than 10 supers, but Station CKCL Toronto; The Shamrock tory siren Signal, and newly designed I found the Silver-Super the very best Manufacturing Company, Newark, N. cabinets. I ever built and it is beating every set J.; The Inter -Ocean Radio Corp., manu- in town for reaching out and bringing in facturers of Woodehorn; Niles Manu- "Clearco Crystal" the distant and hard -to -get stations. It facturing Company, manufacturers of is easy to tune, selective, the locals the Niles chargers; and several other Ready never bother me, and it was easy to build. well known lines. fine or the most unusual endorsements The parts and circuit are all Silver- ever given an accessory has just been Marshall, and I feel I have the best - put into practice by the Howe Auto performing set on the Pacific Coast. New "B" Battery Products Company, which now are I had no trouble in building it. I simply including with each Howe Radio Re- followed the instructions with parts I Charger ceiver a special card relating to the had bought, and after hooking it up, it The Apco Manufacturing Company, Clearco Crystal, which has been adopted worked perfectly." makers of the well known line of Apco as standard for Howe Sets. ' The card Battery Chargers and other Radio states: Fada Radio, Limited,, products, announce a new "B" Battery "This Howe Radio Receiver is equipped Charger, that is a radical departure from with a Clearco Crystal, adopted as Announcement anything heretofore manufactured. standard for Howe Sets after exhaustie A Canadian Corporation has been It is a combination electric light bulb tests. It is highly sensitive and hot formed under the name of Fada Radio and vibrator type, which charges either everywhere. \Ve highly recommend this Ltd., at 821 -827 Queen Street, E. Toron- a 24, 48 or 96 volt battery at from 1 -10 crystal. The continued use of Clearco to, Canada. The officers of this company to 1 -4 of an ampere, depending on the Crystals in your Howe Set will give you are as follows: President and Treasurer, size of the lamp used, which is an or- the best possible reception. If your Frank A. D. Andrea; Vice -President, dinary electric light bulb of 25 to 150 dealer does not handle Clearco Crystals, Concetta Andrea; Secretary, R. M. watt capacity. have him write direct to the Clearco Klein; Manager, C. R. Fraser; Superin- The manufacturers claim that this is Crystal Co., Idaho Springs, Colo." tendent, T. M. Rozelle. the only Battery Charger made that The card shows upon its reverse side This Canadian Company is licensed will charge 100 volts at one time in 10 the towering peaks of the Rocky Moun- under the Canadian Hazeltine patents hours, at a cost so insignificant that it is tains in the vicinity of Idaho Springs, in conjunction with F. A. D. Andrea, hardly measurable. Colorado, where the mineral which goes Inc., of New York City, to manufacture The device sells for $4.00, and complete into the making of Clearco Crystals a complete line of Fada Neutrodyne data will be sent by the manufacturer is mined. The spot, incidentally, is Receivers. on request. (Turn to page 90) 16 RADIO AGE for August, 1925 l'he Magazine of the Hour

ment in the form of two fifty watt tujes. Previous oscillators had been made to operate on four or five meters, but it had been necessary to eliminate the tube sockets and remove the bases. It was also necessary to nullify the tube capacity. Redington's form of oscillator makes use of the internal capacity, and by the use of extremely short leads between the sockets, he was able to make the set oscillate at 3.8 meters.

Write the Pickups and Hookups editor and tell him what you are doing to eliminate static.

Fig. 5, (above) Browning Drake adaptation, using 4 UV199's, the fifth in parallel with the fourth tube.

Fig. 6 (at right). The veins on Mr. Cox's hand do not stand out unduly, so we assume the self-contained set must not weigh very much. And weight is something which a traveling man doesn't like plenty of. (Continued fron: page 22) f: sling and strength of signals on differ - ci.i wavelengths.

Edmund B. Redington, of Waverly, N. V., a senior in the class of 1925 at Union College, has been awarded the Bailey Prize given each year for the senior who contributes most to the advancement of the college. Redington's work was the operation of a radio transmitter on 3.8 meters. This was accomplished using standard equip-

Fig. 7. Here is the set we mentioned previously which P. E. Chapman uses while canoeing. It is an ultra- audton arrangement with two stages of audio, using "199" tubes.

li RADIO AGE for August, 1925 Tl.e Magazine of the Hour 87 Standard Radio Receivers Earn $100 a Recently RADIO AGE inaugurated a new department called "Know Before You Buy," to serve as a guide to the prospective radio purchaser in deciding on the. receiver best suited to his individual needs. Fans throughout the Week In Radio country have shown an instantaneous response to this new feature, and accordingly it is continued and will be a feature of all forthcoming numbers of RADIO AGE. Readers are invited to write us concerning the sets in which they Easy to are interested, and manufacturers also are asked to send us material describing their sets. Learn at Home Big money every week in fascinating easy work wonderful future. Hun-- dreds of big paying positions

in this huge new industry 1

More Money for YOU in Radio THOUSANDS of Radio Experts are needed to design. repair, maintain, sell radio apparatus. to operate broadcasting stations, as ship and land operators. to go into business; to instruct, sell, demonstrate, superintend and for V TESTING the Melco Supreme re- frequency of an incoming signal. If the scores of other big paying radio jobs. ceiver we experienced a few new set is designed to give great amplification And now. you can easily become a Radio Expert. Studying at home in spare time. you can quickly things, both in circuit design and it often will burst into a shrill whistle as qualify for a splendid Radio position. Astonishingly use of radio apparatus. The Melco exact resonance is reached. It is both small cost. Famous radio instructors give you Indi- Supreme receiver is a tuned radio - desirable to obtain great amplification vidual help by mail. Training Guaranteed. frequency receiver using five tubes, and of the signal and a resonant tuning follows the usual design in such a circuit. condition but it is impracticable to re- Free Employment The differences that exist arr not in any ceive a signal under such n condition way radical but they represent refine - without promoting the oscillation an- Service Hardly a week goes by without our receiving wents in parts of the circuit that are im- noyance. urgent calls for our graduates. "We :teed a com- portant. petent Radio Engineer " -"We want men with The engineers of the circuit have Oscillation Control. executive ability ir, addition to radio knowledge to become our local managers " -"We require the used a variable inductance in places The Melco Supreme receiver employs services of several resident demonstrators"-these of the customary variable capacity and a method of controlling oscillation by are just a few small indications of the great variety fixed inductance combination that is allowing exact tuning to resonance and of opportunities open to our graduates. used so much in this type of receiver. controlling the amplification of the The advantage in substituting a variable signal to a point that lies just below Receiving Set and inductance in place of the customary the point where oscillation takes place. Special Parts condenser and coil combination lies in the This is done thru the manipulation of Our course of practical instruction includes greater amplification of the radio -fre- two small dials that are situated a not only several of our own special patented instru- quency energy given by the use of a. little above the center line axis of the ments, but in addition we furnish material and dia- large grid inductance. We not seen three main wave length tuning controls. grams for building receiving sets-all without addi- have tional cost. This is an absolutely complete course much in the line of variable inductance Reception of distant stations is made which qualifies you for the government first -class tuned radio -frequency receivers because more easy by the use of these dials license and for the big -pay jobs in Radio. there are many peculiar obstacles that by allowing the two oscillation con- We Help You to Big -Pay present themselves when a high induc- trols to remain in an oscillatory con- tance is used in the grid circuit. The dition. The incoming signal is no- Positions Scores of young men who have taken our course most pronounced of the drawbacks is ticed by the oscillation whistle. When are already earning from $75 to over $200 a week. the straying of magnetic fields from once the station is located the two Merle Wetzel of Chicago Heigits, Iu., advanced one stage to another. A feature of controls may be adjusted to a point from lineman to Radio Engineer, increasing his salary 100% even while taking our course! Emmett the Melco Supreme inductances is the below the oscillation point and the Welsh. right after finishing his training started confinement of each field to its respective signal will be freed from any inter- earning $300 a month and expenses. Another grad- inductance. ference caused from the oscillation. uate is now an operator of a broadcasting station PWX of Havana, Cuba, and earns $250 a month. "D" Shaped Coils Used. Spacing of Parts. Still another graduate only 16 years old is averaging $70 a week in a radio store, and we help our graduates This is accomplished by splitting Maximum spacing of the sensitive to positions like these. the inductance in two D shaped coils, parts of the circuit is obtained by con- both mutually connected to form one structing the set with the stage sockets Send for FREE BOOK continuous connection, mag- in following order: (1) Second There's more money for You in Radio. Find out but the the audio what this field has meant to hundreds of our grad- netic lines of force so travel that they stage; (2) First radio stage; (3) Second uates -and how you too can profit in it. "Rich are attracted to one another and self - radio stage; (4) First audio stage; Rewards in Radio' has just been printed. It is confined. The between (5) Detector stage. filled with the latest Radio facts. figures and illus- path presented trations of tremendous interest to you. Right now the two coils of each stage is of much Spacing the first audio stage be- -if you are at all ambitious -send for this valuable less resistance than the path offered from tween the second radio and the de- free book. Write Now while our Special offer is stage still open. Fill out the coupon -and mail It now! to stage for promotion of magnetic tector stage keeps the detector stage National Radio Institute, Department 53KB, straying from one stage to another. sufficiently far away from the radio Washington, D. C. The prevention of stray magnetic stages to minimize any tendencies for fields is highly desirable if reception is the detector tube to oscillate or regen- NATIONAL RADIO INSTITUTE, Dept. 53K1., wanted, unaccompanied by whistles and erate. If this were not corrected in Washington, D. C. howls. To prevent the impairing of this manner it would probably be Without obligation send me your book "Rich Re- reception by whistles and howls the necessary to use an additional oscilla- wards in Radio," which tells all about the oppor Melco tunitics in Radio, how spare time study at home svi:l receiver has two auxiliary ad- tion control to retard regeneration. qualify me quickly as a Certified Radiotrician so I justments that are designed for the sole By arranging the parts as specified can get one of these splendid positions. and how purpose of allowing maximum amplifi- regeneration is eliminated before it is your Employment Service helps me to secure a big - cation of the received signal without created and the additional control is pay job. interference by whistles and howls thru made unnecessary. Name ° ge... _...... oscillation. Oscillation is generally ex- The Melco Supreme receiver is a perienced when the three main tuning handsome instrument possessing a most Street .....__ _. .._._. vials are tuned to resonance with the pleasing balance of operating controls City __ ....Stase...... _.....- SS RADIO AGE for August, 1925 The Magazine of the Hour THE RADIO AGE BUYERS' SERVICE What do you want to purchase in the radio line? Let the staff of RADIO AGE save you time and money by sending in the coupon below. Enter the number of the article you would like to know more about in the spaces provided in the coupon. VLIh'--Ir - _IIIIIU1 1 tIt _ll f¡ t 1 95 186 } "A" Batteries Grid leak holder. Rheostats, automatic 2 Aerial protector. 96 Grid, transmitting leaks 187 Rheostats, battery 1Ì ¡=unld, 3 Aerial insulators 97 Grid leaks, tube 188 Rheostats, dial 4 Aerials 98 Grid leak., variable 189 Rheostats, filament 5 Aerial.. loop 99 Grinder., electric 190 Rheostat, potentiometer 6 Amplifiers 100 Ground clamps 191 Rheostats, power 7 Amplifying units 101 Ground roda 192 Rheostats, vernier 8 Ammeters 102 Handles, switch 193 Rods. ground 9 "B" batteries 103 Head band. 194 Rotors Roll 104 Head phones 195 Scrapers, wire Majestic 10 Batteries (state voltage) 11 B dry cell 105 Head sets 196 Screwdrivers 12 Batteries, storage 106 Honeycomb coil adapters 197 Screw. of the 13 Battery charger. 107 Hook ups 198 Schools, radio 14 Battery clips 108 Horns, composition 199 Set.. receiving -- cabinet 15 Battery :Yates 109 Horn., fibre 200 Set., receiving-crystal 16 Batter> bstitutes 110 Horns, mache receiving-knock-eceivr g- knock- 17 Bezels Ill Horns, metal downdownSet., 18 Binding posts 112 Horns, wooden 202 Set., receiving - Neutro- Mighty Organ 19 Binding posts, insulated 113 Hydrometers dyne 20 Book. 114 Indicators, polarity 203 Set., receiving-portable 21 Boxer. battery 115 Inductances. C. W. 204 Set., receiving-radio fre- 22 Boxes. grounding 116 Insulation, molded quency 23 Bridges, wheatstone 117 Insulation material Sets, receiving-reflex 24 Broadcasting equipment 118 Insulators, aerial 206 Sete, receiving-regenera- Mighty tones from 25 Buhingn 119 Insulators, composition tive 26 Buzzers 120 Insulators, fibre 207 Seta, receiving -Reinartz 208 Set., receiving -sectional 27 Cabinets 121 Insulators. high voltage 122 Insulator., cloth 209 Set., receiving-short wave the depths of the 28 Cabinets, battery 210 Seta, receiving-super-re- 29 Cabinets. loud speaker 123 Insulators, glees generative 30 Carbons. battery 124 Insulators. hard rubber porcelain 211 Sete, tramitting noblest of musical in- 31 Cat whiskers 125 Insulators. 212 Slate 32 Code practise. 126 Irons, soldering 127 Jack. 213 Shellac 33 Coil. 214 Sliders struments do not tax 34 Coils, choke 128 Filament control 215 Socket adapters 35 Coils, coupling 129 Jars. battery fIA 216 Sockets. 36 Coils, filter 130 Key., transmitting 217 Solder the resources of 37 Coil., grid 131 Knob. 218 Soldering irons, electric 38 Coil., honeycomb 132 Knock -down panel unit. 219 Soldering paste 39 Coils, inductance 133 Laboratories. testing 220 Solder flux IIt Rauland- Lyric. Ac- f 40 Coils, Reinartz 134 Lever, switch 221 Solder salt. .ei 41 Coils, stabilizer 135 Lightning arresters 222 Solder solution 42 Coils, tuning 136 Loosecouple. 223 Spaghetti tubing curately designed for 43 Condenser parts 137 Loud speakers 224 Spark coils 44 Condenser plate. 138 Loud speaker units 225 Spark gaps 45 Condenser., entenneoup- 139 Lugs, battery 226 Stamping. ling 140 Lug., terminal 227 Stator. faultless amplifica- 46 Condensers, by -pate 141 Measuring instruments 228 Stop point. 47 Condensers. coupling 142 Megohmeters 229 Switch r 48 Condenser.. filter 143 Meters, A. C. 230 Switch levers t((;fl tion, this instrument 43 Condensers, fixed (paper. 144 Meters, D. C. 231 Switch points grid. or phone) 145 Mica 232 Switch .top. 50 Condensers. variable grid 146 Mica sheet. 233 Switches. aerial faithfully transmits all 51 Condenser., variable mica 147 Milliammeters 234 Switches, battery 52 Condensers. vernier 148 Mineral. 235 Switches, filament 53 Contact points 149 Molded insulation 236 Switches, ground organ tones-those 54 Contact, .witch 150 Molybdenum 237 Switches, inductance 55 Cord tip. 151 Mountings, coil 238 Switches, panel 56 Cord.. for head act. 152 Mountings, condenser 239 Switches, single and dou- of the piccolo stop as 57 Couplers, loose leak ble throw 58 Couplers. molded 153 Mountings. end 240 Tone wheels t1. 59 Coupler., vario 154 Mountings. grid leak 241 Towers, aerial as 60 Crystal alloy 155 Mountings, honeycomb 242 Transformers, audio fre- well those of the 61 Crystal holder. coil quency 62 Crystals, rough 156 Mounting. inductance 243 Transformers, filament 63 Crystals, mineral .witch 244 Transformer., modulation open diapason. 64 Crystals, synthetic 157 Name plates 245 Transformers, power 65 Crystals, unmounted 158 Neutrodyne set parts 246 Transformers, push -pull 66 Crystals. mounted 159 Nuts 247 Transformer., radio fre- 67 Desks, radio 160 Ohmeters quency 68 Detector unit. 161 Oscillators 248 Transformer.. variable 69 Detectors, crystal 162 Panel cutting and drilling 249 Transmitters 70 Detector., fixed crystal 163 Panels, drilled and un- 250 Tubes, vaccuum- peanut 71 Dial. adjuster. drilled 251 Tubes, vacuum -two ele- 72 Dials, composition 164 Panels. fibre ment 73 Dials, hard rubber 165 Panels, hard rubber 252 Tubes, vacuum- threeele- 74 Dials, rheostat 166 Parts ent 75 Dials, metal 167 Paste, soldering 253 Tuners 76 Dials, vernier 168 Patent attorneys 254 Variocoupiere, hard rubber 77 Dials with knob. 169 Phone connectors, multi - 255 Variocouplers. molded 78 Dies 256 Vario rs. wooden 79 Drills, electric 170 Phonograph adapters 257 Variometermeter e, hard rubber 80 Dry cells 171 Plate., condemer 258 Variometere, molded 81 Earth grounds 172 Plugs, coil 259 Variometer., wooden 82 Electrolyte 173 Plugs, telephone 260 Varnish, insulating 83 Enamels, battery 174 Pointers, dial and knob 261 Voltmeter. 84 Enamels, metal 175 Pole., aerial 262 Washer. 85 End .topa 176 Potentiometers 263 Wave meter. 86 Eyelets 177 Punching machines 264 Wave traps 87 Experimental work 178 Reinartz set parts 265 Wire, aerial 88 Fibre sheet, vulcanized 1'9 Regenerative set parts 266 Wire,l ped and stranded 89 Filter reactor. 180 Receiver caps Wire, copper 90 Fixtures 181 Rectifiers, battery 268 Wire, insulated 91 Fuse cut outs 182 Resistance leaks 269 Wire, Litz 92 Fuse., tube 183 Resistance unit. 270 Wire, magnet is a Rauland -Lyric laboratory- 93 Generator.,high frequency 184 Rheostat base. 271 Wire, platinum grade audio transformer de- 94 Grid chopper.. rotary 185 Rheostat strips 272 Wire, tungsten signed especially for music 1I lovers. The price is nine dollars. s If nn a e e s s Descriptive circular with am- RADIO AGE BUYERS' SERVICE. 500 N. Dearborn St.. Chicago, Ill. iii plification curve will be mailed Please see that I am supplied with buyinn s7cifiestions and prices on the articles numbered herewith: on request. All- American Radio Corporation, 4201 Bel- mont Ave., Chicago. I I I I I I I I I I I I I JII I am a- Dealer E Jobber I:1 Mfgrg.' Rep. Manufacturer

Firm [If identified with Radio industry] ...... __...... _..

-'4'\.: My Occupation ; Tai ill( AN Off III - AptERI MyName ....'--'----_....----'---'---'---_....__...-..-----...---_...._ Q.Y ra,r CqN ' TRANSFORMER c The Choice of Noted Musk Critics City ...... --_....-_--.._.....--..._..-..._ State -..._...... -._...... _....-....._.-_. t . a.aS a iQmnapsi i se®olos ems ow® mai 0oes (AAt * Tested and Approved by RADIO AGE RADIO AGE for August, 1925 The 1f(4,razifie of the hour S') Scientifically Designed I. F. Transformers IT IS not the purpose of this paper, nor is it possible in the space available, to enter into a theoretical consideration of the ideal characteristics of intermediate frequency inter -stage transformers suitable for use in super- hetero- dyne receiving systems, but rather to explain the desirable characteristics of such transformers briefly, and to present some designs which have been found most satisfactory, yet simple enough to be constructed by the experimentally inclined radio enthusiast. As is well known, a signal received Over 500 Stations in U. S.- upon a superheterodyne system at a short wavelength is converted by means How Many Do You Get? of an oscillator and first detector to some longer wavelength, then fed to a sharply The air is fairly crowded with an infinite variety of programs. tuned amplifier, amplified, and again Yet most listeners rarely hear more than thirty or forty. A detected, after which the audio frequency in signal may be further amplified. The good set has the ability to bring practically all of these sta- reason for this change in wavelength tions, but it takes fine tuning is two -fold: Direct radio frequency to get them. Almost impos- amplification at short wavelengths is not at all efficient, whereas it may be sible with ordinary dials. Slip- made extremely so at longer waves ping, backlashing "Verniers" between two and ten thousand meters. are little better. The second reason is that an efficient The new "BETTER TUNING" radio frequency amplifier operating at Control, solves the problem. Smooth, broadcasting wavelengths must have each stage tuned, which would involve easy action without the slightest from three to six adjustments for a really backlash or lost motion. A vernier sensitive receiver (interstage coupling device for fractional readings. Turns in the amplifier prevents practically quickly and easily to that last, fine building such a really sensitive system) hairline adjustment. each time it was desired to tune to a Works with either right or left turn- different signal. In the super, the ampli- ing instruments. Readings in dial fier, consisting of several stages, is per- numbers and wave lengths or call manently tuned to one wavelength, and letters. the signal wavelength changed to that of the amplifier by means of but two adjust- Not only makes your set work bet- ments -the oscillator and loop circuit ter but look better. controls, regardless of the amount of New B amplification obtained. -T Products The New B -T Inductance, the Toro - style Transformer practically eliminates The Requirements Patents Pending pick -up, no intercoupling. OBVIOUSLY, The B -T Socket, something new and the ideal interstage different. Features you'll appreciate on transformer must operate at a wave- sight. Write Dept. S for circulars. length long enough to get away from the drawbacks of shortwave amplification, but not long enough so that the amplifier will verge into the audio frequency range MFG. and be non -selective. The transformer BREMER - TULLY co. must give the greatest possible again 532 S. Canal St. Chicago, III. (amplification) so that a minimum number of stages may be used; it must be entirely stable, and preferably operate with a negative grid potential to be economical of plate current. In its ideal MARVELOUS NEW WHERE AN AUDIO $3.$D state, the transformer would give uni- AUDIO TRANSFORMER Transformer la Called for in add e mueioelaualityto ear setfar the Blueprint Use form amplification beyond anything you ev.r beard over a frequency before. range of 10,000 cycles (necessary for KARAS HARMONIK FLINT GUARANTEED Amelieee low. middle and high undistorted speech and music repro- tone. -all to the same big volume. Transformer thon elimimtios distortion. Brings From Your Dealer or Direct. duction) yet no amplification of any out the vita harmonics and over frequencies outside this range. tone et music. Pries $7.00. Writ; FLINT RADIO CO. It must Reckwdl 1894 Wilson Ave., Chicago not be so selective as to cut frequencies Ions Electric Ce, Dept. 58.93 4042 N. SI.. Merge within this range, and it should be so shielded either by a metal case or an iron core that it will not be affected by strays in the nature of long wave telegraph CORRECTION transmission, etc. This latter considera- BAKELITE KNOBS Our new address is 116 -118 So. Wells Permanently hold their color and Street, Chicago. Dealers will please tion necessitates the use of a wavelength finish. Write for Booklet 31. not note this change when writing for a commonly used for telegraph trans- our "Salespeaker." mission, ÖBAKELITE CORPORATION copy of B 247 Park Avenue, New York, N.Y. HUDSON- ROSS116 S. Wells St. Chicago (Turn to page 96) 00 Chicago Office: 636 West 22d Street * Tested and Approved by RADIO AGE 3F 90 RADIO AGE for August, 1925 The Magazine of the Hour LIFE, With the Manufacturers LIBERTY (Continued from page 85) and the Pursuit of Brooklyn "Good Will" Trip Voices of the World to Be a Success at "World's Fair" HAPPINESS! Covering 9,021 miles by rail and 2,500 YORK -Plans now afoot by miles by automobile on their "good-will NEWleading broadcasting interests in the and industry" trip, the Brooklyn Cham- United States, who will exhibit at the ber of Commerce made radio history as Fourth Annual National Radio Exposi- (-1(4v) well as scored travel and industrial honors tion, opening in Grand Central Palace, this year. New York, September 12, will create in Their special train was radio- the Exposition auditorium a new tower equipped of Babel in which the voices of the world and with the exception of one day, fol- will lowing the damaging of the apparatus, the be received by radio, according to an members heard broadcasting, in many announcement by Harold Bolster and cases of programs welcoming them to J. C. Johnson, directors of the Exposition. various cities or given otherwise in their Through the broadcasting studios and honor, throughout the United States and receiving station to be set up in Grand Canada. Central Palace during Exposition \Veek, was probably London, Paris and Berlin will The antenna 60 feet long, on the be "plugged in," through high power 1,rt) roof of the observation car, serving a five first tube neutrodyne set an amplifier. transmission, and the exchange of and international concerts, it is expected, will In addition, a portable set was carried take on Dis- wherever the party went on auto trips to place the opening night. scenic patches from Berlin, reflecting the great points. public interest created in Germany by Eric H. Palmer, of the Freed -Eisemann the announcement that an agreement had Radio Corporation, member of the Cham- been concluded between wireless interests ber, made the entire trip, and reported in excellent reception on the whole, con- that country and America for an You Won't Have sidering the conditions, particularly of exchange of radio concerts, are confirmed the high -power stations like KDKA, by exhibitors at the Fourth Annual to WHT, KGO, KOA, WGN, and WSAI,' National Radio Exposition. Technical sometimes when the train was going a experiments, it is added, will begin almost mile a fading on immediately, and by September the regular minute, with occasional exchange of in force. Pursue sharp turns and marked fading in tunnels concerts should be when The present outlook is that the Amer- and crossing steel bridges. ican radio fan will be greeted at the Expo- HAPPINESS Palmer, took his set into the Grand sition in four languages Canyon, of Peak, into at least different You can have it right at your elbow to the top Pike's from as many parts of the world. On the to while away the time 'til old Lady Yosemite Valley, besides Lake Louise and on snow- other hand, the messages delivered Static gets off the line! the covered mountains of the through the microphone in Grand Cen- You'll have no trouble getting Canadian Rockies, among Indian pueblos tral Palace by leading figures in American station Z- I- F -F -S, because you'll of the. Southwest, on the shores of the Pacific public and industrial life, will be heard in find it is always tuned in to catch Ocean, and along the auto roads millions of homes across the Atlantic. your funny bone's wavelength, and of California, never failing to receive music from Radio interests representing an annual is more ticklish to your giggle box the ether. business of over $300,000,000 will exhibit than the finest cat whisker! at the Fourth Annual National Radio ZIFFS, Badzib's Book of Art Exhibition. So complete and elaborate and Wit, is the only humorous Double Service Tube on the are the exhibits to be offered this year to monthly of its kind on the market, the radio trade and the radio public that and is crammed full of the best Market the third floor of the Grand Central artists and funsters in the world! A tube with double service is announced Palace has had to be opened for the Exclusive Photo Section! Com- Exposition, in addition to the ground plete gallery of French -American by the Van Horne Co., at Franklin, Ohio, this and mezzanine floors. Nor is public Art Studies in color! Fifty pages of concern being the manufacturers of interest less keen. Reservations already illustrations! Pep, Ginger, Punch! the Van Home Selected and Musselman had been received for over 50,000 tickets ALL FOR TWO BITS! Certified radio tubes. from large industrial organizations, The new tube is known as the 3V -A national institutions and dealers through- Pick This Out On radio tube and'is adaptable either to dry out the country. cell or storage battery operation. It has Your Piccolo ! the same structural principle as the 5V-A, An Antenna Support for Even tho' your set is growling which is patterned after the conventional 'TO you think a cat is howling City Dwellers 201 -A. It And the music cones in wailing. hissing sniffs. consumes one quarter of the An attractive antenna support for the You will giggle. grin and chuckle current of a 201 -A. 'Tit you hafta loose the buckle use of cliff dwellers in the city who desire The 5V -A tube is of the 5 volt type On your belt. if you've the latest book of ZIFFS that radio shall be as unobtrusive as . with a current consumption of one quar- possible, has been designed and marketed You wouldn't go fishing without ter of an ampere, while the 3V -A takes by the Jife Support Co., at 5568 \Vest bait, would you? Well, then, don't three volts and consumes one tenth of an Van Buren St., Chicago, Ill. try to get Hong Kong on a stormy The device consists of a wire spring night with a crystal set, till you've ampere. The mutual conductance on the 3V-A's is 500 micro -mhos; the plate clamp which encircles a small porcelain put your John Henry on the tag is slipped onto flow 3.8 milliamperes to 5 milliamperes insulator. The clamp below: wire which is to 6.5. picture moulding; the and the amplification be strung up inside the house is passed TIFFS, \Vith each of the certified tubes sold, through the insulator held by the spring 608 South Dearborn, Musselman furnishes a characteristic and the job is complete. Chicago, Ill. curve of the tube itself, a scheme which Dear Badzib: is rapidly finding favor with the radio I got a radio. I got Hawaii. I y got drowned 3: ' T out. I got peeved. public. Thus you have matched trans- 6M= I don't see nothin to laugh at, you big bumf formers and then matched The E Here's two bits. Send me the July ZIFFS, and tubes. LA I will characteristic curve on each tube enables you to determine its ability to perform in !or D1. oellonlersAmplegC8acvb They Call Me 12,000, 48.000, 50,000, 100,000 Ohms. Lint different parts of the circuit, and saves the 61.50 each. Special sixes to Order 82S0 each. trouble of having to have a curve drawn Deale write for discounts. When Better /tenth: our, LndIliveet are made they will be Crescente. on all your tubes. Crescent Radio Supply Co., 5 Liberty St., Jamaica, N.Y 44 Tested and Approved by RADIO AGE aF

11 RADIO AGE for August, 1925 The .Naga :ive of the flour 91 James F. Kerr, Noted French Battery Reorganizer}, Showman, Dies A refinancing plan, whereby the French Battery Company Madison, It is with profound regret that we at Wiscon- announce to the radio Industry the sin, will be able to greatly increase the untimely death of James F. Kerr, general output of that plant, has been announced manager of the Radio World's Fair and by officials of the company. At a stock- RSM nationally known showman. holders' meeting recently, it was decided Mr. Kerr's sudden demise will in no to increase the preferred stock. way alter the policy and activities of the The reorganization plan which makes Second Radio World's Fair and the the Madison concern one of the largest PAM Fourth Annual Chicago Radio Show, it manufacturers of dry batteries and has been announced. U. J. Herrmann, flashlights in the United States does not Managing Director of both shows, and involve any changes in personnel. closely identified in their management, In view of the fact that the company has welfare and success in the past, will decided to intensify on the production continue to carry them on with the same of dry batteries and flashlights, the degree of perfection as attained at previ- directors voted to drop the word "Car- ous shows. bon" from the name of the company, giving the firm the new title of "The Mr. Herrmann was to have sailed with French Battery Company." the Donald B. McMillan Expedition from Entirely silver -plated! And Boston on June 17th, but has now cut "Arctic" Pierce North a new standard has been set short his trip in order to devote his to for Canada for low -loss condensers! It undivided attention to the direction of New Arctic radio transmission records is only logical that the new the forthcoming Second Radio World's undoubtedly will be established when Silver -Marshall S -L -W Con- Fair and the Fourth Annual Chicago the Canadian Government ship "Arctic" densers should be the first Radio Show. enters the polar regions on her annual to be so built. Their losses trip this Summer. The vessel will be are lower than many labora- Brandes Broadens Line equipped with a transmitting set espec- Since 1908 Brandes have been special- tory standards --their me- ially designed to keep the Canadian chanical design unique and izing in radio acoustics and their labora- Government posted on her movements in tories been to original. The S -L -W plates have constantly striving the land of the midnight sun. The mean real selectivity and improve the audio circuit of the radio Arctic will leave Quebec about June 27. station separation. receiving set because it, in the final The vessel holds the present record for analysis, determines the quality of the receiving and transmitting radio messages No. 305 .0005. $6.00 work has resulted in No. 306 .00035.. 5.75 reception. This from the point nearest the North Pole. No. 307 .00025.._ the following new additions to their line: The Canadian Government is preparing A new audio transformer which ampli- to start the ship off on her voyage some- fies without distortion frequencies from what earlier this year, in order to pierce S -M 200 to 4000 cycles per second with the farther into the Arctic ice field than it did in high voltage amplification ratio of 1 to, 5. 1924. The staunch ship, built especially Type It is so designed that two stages of ampli- for Arctic travel, is being reinforced on 210 fication may be employed without sac- bow and stern with heavy steel plates to rificing quality of reproduction. It is fight its way through the ice to a point and provided with outside soldering terminal farther north than it has been able to 211 connections, screw mounting base, and penetrate most of the 20 years it has been is completely shielded. making annual pilgrimages to the Arctic Trans- Announced also is a new horn speaker circle. formers (Type H), which is somewhat larger than Last year the vessel continuously their Table- Talker and gives much received messages from the Canadian S -M 210 and 211 trans- greater volume. This speaker has lam- government transmitted from Station formers are known as the inated pole pieces which increase its KDKA, on the short wave, and estab- finest intermediate trans- magnetic efficiency, and, in turn, increase lished the "farthest north" reception formers ever made. They its volume. record when a message from KDKA were an important feature of was received at Cape Sabine, north of the receiver built entirely of Peary's winter base at Etah, and within S -M parts, that took the 11 degrees of the north pole. grand sweepstake prize at the recent Los Angeles Radio "THE TUBE WITH A PEDIGREE" Not all the reply messages sent from the vessel to the Canadian government Show. Price, each...... $8.00 were received, however, and in order to Send 4c in stamps for Free insure uninterrupted two way transmis- Circulars of S -M Products, and reprints of article from Radio sion this year, Commander C. P. Edwards, Broadcast, describing the remark director of radio service of the Canadian able new Super -Autodyne Re- il yr -rrTar-f -P.r:fry Department of Marine and fisheries, in ceiver. collaboration with C. W. Horn, superin- HE yt+ tendent of radio operations of the West- ' MVSSE MCa el Silver jarsha Lim OD, inghouse Company and the KDKA ... engineers, is having a more powerful set Ave. built for the vessel this year. 114 S. Wabash Chicago, Illinois William L. Sayre Joins HERE is only one way to measure the value of a radio tube, regardless of who H. H. Eby Co. made it, and that is by the characteristic The H. H. Eby Manufacturing Com- curve reading. In this way, and no other, of well known can its value as a tube be determined in pany Philadelphia, makers advance. All MUSSELMAN TUBES of quality binding posts, recently acquired have a characteristic curve slip inclosed the services of William L. Sayre, who has at the factory and certified when the read- been identified with radio interests for ings are above the standard set by leading the past fifteen years. Perfect Reproducer an Tone loud and pleasing. radio engineers as to what constitutes Mr. Sayre was made an associate of Handsome material sad design. unusually good tube. the Institute of Radio Engineers in 1914 Black, $22.50 Shell, $25.00 Jobbers, manufacturers, and and later of the American Institute of Mother -of- Pearl ...... $30.00 dealers are Invited to write for Makers details as to sales franchise. Electrical Engineers. His earlier training AMERICAN ELECTRIC COMPANY State and 64th Sta.. Manufactured by under able physicists, coupled with his Chicago later practical radio and merchandising The Van Horne Co., Franklin,Ohio experience, SALES OFFICE will enable the Eby organiza Lion to offer further aid to its many A. J. MUSSELMAN manufacturing and distributing customers Are you ready for the big season that 601 -C Machinery Hall - CHICAGO upon whom NIT. Sayre will call after a starts in the Fall? Order your September time spent at the factory. RADIO AGE NOW! Tested and Approved by RADIO AGE iK 92 RADIO AGE for August, 1925 The ÄTagacine of the flour Brainard Foote Analyzes Tuning Tricks (Continued from page 10) tributed capacity. Then, to bring KSD ELL The Jewell near to 95 on the dial, it was necessary to remove five of the rotor plates. The Radio Test Set condenser is then really only a 15 plate instrument, because the fixed plates corresponding to the removed rotor U This is the most com- plates are "dead" too. Thus the capacity plete Radio Test Set on is reduced to about 7 -12 of its former value, or about .0003 mfds. Two marked the market. improvements result from this: I. The inductance to capacity ratio q Manufacturers, Ex- is much higher than it was, meaning perimenters, Jobbers and louder signals. Dealers all over the world 2. The tuning scale is evenly distributed over the entire scale, meaning just as are using it. This set is good selectivity with much easier tuning. Jewell's outstanding con- Thus one of the chief gains made by tribution to Radio. using a coil having low distributed capacity, even with the basket-wound type, is the greater wavelength range possible with a given variable condenser. Price $75oó It must be understood that more wire is needed, and because of the fact that Send for Complete added wire means added resistance, some might think the spaced system a Circulár disadvantage. However, the use of a higher inductance - to - capacity - ratio Order from Dealer throughout the scale more than offsets the slight increase in wire resistance. Jewell Electrical Instrument Co. A set adjusted to tune in this fashion, 1650 Walnut St., - Chicago especially if the condenser be one of straight -line wavelength, as in Fig. 2, where each degree represents a certain "25 Years Making Good Instruments" number of meters (usually 3M to 43 meters) is a pleasure to operate. To keep it smooth- running, the antenna absorption must not interfere on short waves, on account of the natural period of the antenna system. Antenna Natural ¡N THE case of a long and high aerial, the natural wavelength may lie near 200 meters or above it, including the antenna coupling coil of the set. Hence, the coupling coil should have a tap on it, WANT SELECTIVITY? so that only 4 or S turns are used for short wave coupling. The antenna natural interferes with regeneration and With Tone, the set usually will not oscillate over 4 or 5 degrees near its lower scale in case the antenna natural is too high. When * Clearness and Volume? the natural can't be reduced by using fewer turns in the coupling coil, a small series condenser is advised, .00025 to THE .0005 mfds. capacity. The circuit given in Fig. 3 shows how the regular three -circuit tuner outfit can be rearranged along the lines of this article. In addition, the method of regeneration does not interfere with the ORIOLE to any noticeable extent, the two tuning controls being independent of each other. 5 -TUBE MODEL 7 The secondary is the space -wound coil about 4 inches in diameter and having Fills the Bill about 60 turns, or any number necessary to place the shortest wavelength at 200 meters. The wire ought to be about Jobbers and Dealers Write for Exclusive Appointments No. 18 in size, although no smaller than No. 22. The tickler is a coil having about 15 turns wound on a 3 -inch tubing W-K ELECTRIC CO. and placed inside the secondary at the KENOSHA, WISCONSIN filament end. The primary is about ten turns, wound on the same tubing as the secondary and at the filament end.

* Tested and Approved by RADIO AGE aF RADIO ACE for August, 1925 The Magazine of the flour 93

The tickler, while -fixed in position, must be tried reversed in case its direction is wrong for oscillation. If wound in the same direction as the secondary, the end away from the grid goes to the regeneration condenser. The headphones or primary of the JEFFERSON audio transformer act as a radio frequency choke coil, so that the R. F. choke coil often specified at point X isn't needed for broadcast waves. Care must TRANSFORMERS be taken not to use a fixed condenser across the phones or transformer pri- AIL- i mary, however. There should be no more turns than necessary on the tickler to secure regeneration, for with too many turns the range of the regeneration condenser will be constricted and it will be hard to adjust the tube to the "edge" of oscillation, just as it is when the usual type of tickler is too big. If the tube oscillates with only 10 turns on it, so much the better. Deciding on a Portable Super -Het (Continued from page 14) will be proportionately, due to the elimination of reaction, etc., which is bound to occur to a varying extent in every amplifier. With the transformers used in the portable super, two stages will get down to the noise level under average conditions. The question then arises as to why we whould use three stages when we obtain the same results Two PopularTypes of with two, and save a tube and batteries. The average fan's answer is "greater sensitivity" but he forgets entirely the JeffersonTransfonners noise level and the fact that more than a Living tones of music and song, drawn into the" mikes" for your given value of sensitivity, assuming for a entertainment, get the reproduction they deserve with Jefferson moment that it would result from the use Radio Transformers as part of your set. The extraordinarily of a third stage, is worse than useless. accurate amplification afforded by Jefferson Transformers brings There is no question but that a novice in to you the music from the air as you would hear it in the studio. can assembly a two -stage audio amplifier Jefferson Transformers give their best, just as the artist does. and make it work perfectly. Yet the It takes pains -and brains -to make fine transformers. Our recipe same man will have great difficulty for leadership in the field is simple: We devote all our time and experience to coils. assembling a comparatively high fre- manufacturing transformers and quency RF amplifier. The same A good set demands Jefferson Transformers to make it better. condi- Good them. tions hold in an intermediate amplifier dealers sell and the number of successful supers JEFFERSON ELECTRIC MFG. CO. that have been built using iron -core 501 S. Green Street Chicago, Illinois transformers indicate they are far the easiest to build in Makers of Radio Tulle Rejuvenators, Radio Transformer.. actual practice. Where Bell- Ringing Transformer., Sign -Lighting Transformer, only two stages are used, the efficiency ile I Coils. Break 1 Có , Auto Transformers,TetgInstrument.,k Ty per stage is increased over a three -stage Transformer., F d Oil Burner Transformer., Oil amplifier, the possibility of trouble in the Burner Ignition Cods. amplifier decreases 25 per cent; and a tube, its socket, a transformer and some wiring are eliminated. This is a decided advantage. From the foregoing it is evident that on the counts of amplification and current RADIO AGE SUBSCRIPTION BLANK consumption, the iron -core transformer Radio Age, Inc., is far superior to the air -core system, 500 North Dearborn Street, $2.50 A YEAR even when the latter is built in the form Chicago of a tuned neutrodyned system. From the novice standpoint, Gentlemen: Please enter my subscription for RADIO AGE, the Magazine of the Hour. for one the additional year. beginning with your next issue, for which I enclose $2.50. stability and ease of assembly put the iron -core system far ahead of the high frequency amplifier. Name It will be seen, then, that the choice of transformers is important, affecting as Street Address it does the operation of the entire super. Transformers that are tested and match- city ------ed as to curves and peaks, in careful laboratory tests, are the best for portable State supers, for they eliminate all possibility Send cash, money order or draft. * Tested and Approved by RAtDIO AGA: 94 RADIO AGE for August, 1925 The Magazine of The Hour

of guesswork and danger of poor opera- 1 tion after you have transported your set a few hundred miles from civilization and radio stores. A fan who takes a portable super on his vacation does not want to fuss with several imposing controls before he finally "lands a station. Sometimes, under the screen of night and in the absence "None better made:' of suitable illumination, he will find it Conform to Bureau to be aware of what he is of Standards spedfi- impossible cations for lowest doing if he has to tinker with six or eight losses. Automatic adjustments before actually beginning bearing take-up and to perceive results. If a portable super ,12-Cell- 24-Volt rugged construction e/ assure permanent is to be efficient, it must be easy to tune. Storage`B'Battery All capac- Two tuning controls, one for each hand, Positively given free with each alignment. purchase of a WORLD A" DMPdEX ities- plain, vernier. and not more than two other adjustments Storage Battery. Yon must Fully guaranteed. send this ad with your order. STANDARD for filament and volume control, are WORLD Batteries are famous for their guaranteed quality easy to remember and easy to handle. and service. Backed by yearn is of successful mannfacture and The day of the complicated super over, tbonsands of satisfied users. Duplex Matched Condensers coianoed with Soto Robber ca, and a portable super that is not easy to against acid and leak Afford Uniform Dial Settings operate had better be left at home for age. yeneeve &Oyer cent and get. the expert to experiment with. 2 -Year Guarantee Always ' O .yeP Only One Bond In Writing á °D t -, Approved Read In installing a portable super in a travel- teil their frisad.. That's o. ea.mlpatlen tabac . v arrival. FftÉÉ " B.tta lacluded. DUPLEX CONDENSER & RADIO CORP. bly of efficient apparatus that will really Extra Often 6 per cent diamant for cub mriestRadio with .new and gat tG g ß. 42 Flatbush Ave. Extension, Brooklyn, N.Y. produce coast -to -coast results. annteed1 st- 50per contmanna trm.Poo. and Ld.z. Inc. WORLD BATTERY COMPANY For portable use, the type "199" 1219 So. Wabash Ave., Dept. 36 CHICAGO. ILL. tubes are acknowledged the most con- For Lack some of the DUPLEX and their difference in volume AUTO refinements JUNIOR venient, and of the and battery drain as compared with the orld Duplex Standard but T (RADIO tubes is negligible. Small tubes STORAGE are 'best at the price:' . larger olo Idealforportable sets. =`; can be so mounted in a portable super, All capacities -plain on a 7 inch by 18 inch panel, that trans- and vernier. \'. \ formers and other parts can be mounted underneath the tube sockets and put out of the way. For general compact- Get Cuba ness, it has been found that seven tubes fit most satisfactorily in a 7 inch x 18 or WANTED-MEN inch layout, as well as being the best from a strictly mechanical standpoint. Mexico City TO L The parts used must also be durable. While Big Local Stations Are Broadcasting, . ARN RADIO... . Many fragile radio parts are now on the The New York Evening World got 40 stations in $75 to $200 a Week market, and they are suitable for the One Evening including Dallas, Los Angeles, and Right now, everywhere, big, Porto Rico; while testing the wonderful sensitivity easy money is being made in elaborate home models for which they of the Radio. Field unlimited.You can were constructed. But for outdoor master radio quickly at home New In Principle -New In Design s'V in spare time. No previous exile- use they will not stand up under the pt', °r" rienceneaessary.Nowisthetime ravages of the weather. Carefully cov- WERNER .I l'sL7/ toenterthis new, uncrowded field. that will withstand inclement 1,000 Mile Receiving Set -FREE ered parts Radio Frequency Onr new home -shady methods make everything about radio conditions, as well as the corroding ele- amaziogly simple. No other conrse like it. Makes yon ex- TRANSFORMERS pert on radio operation, repaira and iostavations of all ments of the atmosphere, should be used. kinds. Send for literatnre telling all about opportunities Not all the burden should be put on the and bow we give 1,000 mile receiving set FREE. Don't . For All Circuits miss tbis big offer -ACT. Write now for big free book. parts, however; the outer case or cabi- Radio Association of America Insist on getting them, if your dealer can't supply 4513 Ravenswood Ave., Dept. 25 ChIcigs net must be covered with a weatherproof you, send your order to us. paint or leather covering, or a like material, that will thrive under Nature's Price $4.00, All Types LOW LOSS punishment. A portable set cannot be Send for Diagrams / Interference expected to be kept indoors during A wonderful interesting book "Radio Frequency frill/ e Eliminator its actual use, so its construction should Amplification" contains popular and technical information with many up-to -date R. F. circuit dia- 50,000 Sold Firs18 Weeks -Every Radio Owner Needs One be carried out with a view to making it Cut oat'lnterference and un- grams of greatest interest to both radio user and Select Station at Will desired a anons. Tune in loud durable against weather as well as the engineer. and clear. Results amazing with any make tube or 25c postpaid crystal set using any kind of serial except loop antenna hardships of walking or automobile ABSORBS STATIC - INCREASES VOLUME travel. R. Werner Radio Mfg. Co.' POSTPAID! The accompanying photograph shows Better reception or 204 -206 Ninth St. Brooklyn, N. Y. your money refund- how a cabinet can be utilized to hold the ed. Bank guarantee. receiver itself, the lower part of the case Assembled complete; attach to being used for the batteries, all of which acrialio two minutes. No tools. Doesn't disturb present log. No are of the dry cell type. The "A" batter- additional tubes or batteries. ies, placed in the order shown, stop the Send SI Bill Now ñm 'onZr_r3 THE LATEST way with is ,7,' Complete ' InGrferenre Radio literature FEE. "B" and "C" batteries, take up the least parts in STEINITE LABORATORIES, Oept 401, ATCHISON, KANSAS possible room and take the curse from the and sets are always featured B. Write for dlcrlpd.e literature and prices our Salespeaker. If you are a live- Staloff.. tat,nlly known price Radio Saw popular load usually caused by the current sup- wire dealer, write for your copy, now. ply. Such an outfit will weigh about 30 HUDSON -ROSS -.116 S. Wells St. Plenty of Surprises in the September pounds, which is about as light as can be Chicago Radio Age! expected of a complete portable set. ,F Tested and Approved by RADIO AGE At RADIO AGE for August, 1925 The Magazine of the Hour 95 Causes of Variation in DX Results (Continued from page 16) Build this phenomenal causing a maximum disturbance at that time. Lightning discharges also cause a great amount of noise in a receiving set, espe- new radio in 45 minutes cially during the summer, when electric storms are frequent and most severe. It is surprising to many when they learn that these disturbanccs are not usually heard over distances greater than 100 miles. These disturbances cause sharp clicks of considerable intensity in the receiver. Another condition which is often found to be very annoying is fading. Many theories have been advanced regarding The revolutionary Erla the causes of fading, but the latest infor- Cirdoid -Five Factory- mation upon the subject seems to indi- Bilt Rit -as you cate that it is largely a matter of inter- receive it. ference between direct waves and waves that.have been reflected from the Heavi- Price $49.50 side layer, which is a layer of ionised air in the upper strata of the earth's atmosphere. This ionised air has the peculiar property of reflecting radio This new type kit is factory assembled. Ready cut, flexible, waves in a manner which might be com- solderless leads make it ridiculously easy to wire. Amazing pared to a mirror reflecting a beam of light. new inductance principle brings results hardly thought Sketch 3 illustrates how both the direct possible. Send for book, Better Radio Reception. and reflected waves travel from the transmitter to the receiver. It is evident OW anyone can build the finest of 4. Improved Tone Quality: The self- receivers in only a few minutes. No enclosed field of Erla Balloon Circloids that the reflected wave travels much more wire bending or soldering. Merely eliminates stray feed -backs between coils farther than the direct wave and is there- attach a few ready cut. flexible eyeletted and consequently does away with mush - fore subject to being out of phase with leads and the job is done. The finished ing of signals and distortion. Tone is the latter wave. As the height of the set is unsurpassed even by the costliest crystal clear and perfectly lifelike. Heaviside layer varies, the phase rela- factory -built receiver. Write for fire information on kit -also book tion will change, thereby changing the But most amazing is the new induc- extent to which the two waves aid or tance principle incorporated in this last See how 45 minutes of fun will give you oppose each other. It is possible for word in kits - called the Erla Circloid the newcst and most nearly perfected set the two waves to entirely neutralize principle of amplification. known to radio science. Easy as A -B -C Four vital improvements result from to finish. Examine it at any Erla dealer's, each other, causing the signal to disappear or send entirely, or they may aid each other and this great discovery, which are not found the coupon for full information, in ordinary sets. illustrations and diagrams free. Also ask cause an abnormally loud signal in the for remarkable new 1. Greater Distance: * Balloon book, "Better Radio receiver. Exhaustive tests have proven Erla Reception," describing the sensational hat barometric pressures also affect * Circloids have no external field, consequently do not affect adjacent coils or new Circloid principle. Enclose 10c for signal intensity and sometimes cause wiring circuits. This enables concentra- mailing and postage on book. ading. tion of proportionately higher amplifica- ELECTRICAL RESEARCH LABORATORIES tion in each stage, with materially in- 2548 Cottage Grove Ave., Chicago *Trade Mork R ei.erred. MARVELOUS NEW creased sensitivity and range. AUDIO TRANSFORMER sdd, s musiealqua1itrto soy setter 2. More Volume: Increased radio fre- ELECTRICAL RESEARCH beyond anything you ever beard quency amplification made possible by LABORATORIES, before. 2543 Cottage Grove Ave., KARAS HARMONIK Erla Balloon Circloids gives concert vol- Amplifies low, middle and high ume to distant signals inaudible with Chicago. U. S. A. tones-el I to the same his volume, nie free than li tins distortion. Brings receivers of conventional typc. Send informa- omt the vita harmonies and over. tion on kit. Enclose 10o This sign idenehrs at. tease of moan. Prise $7.00. Write 3. Increased Selectivity: Erla Balloon for postage for book "Better theneedErbdirtdburorr. Kass Electric Co., Dept. 58.93 4042 N. Reeitretl S1.. Chicago Circloids have no pick-up quality of their Radio Reception." A[(are equipped to give own. Hence only signals flowing in the complete radio service. REBUILD YOUR NEUT-Use same pane antenna circuit are amplified. Static is Name...____.....__ ._...... _-- ...... __..»__..- same parts. No neutralization. 22 feet gold only extra part, circuit and complete greatly reduced for this reason. simple instructions -$S.00 prepaid. Hundred Address of Neut owners use this kit. Details-I0c Dealers Exefunrrffranchiser ere available to high daodeal- 48 page catalog parts-40c. Stamps accepted. euislocabtu aeliopen. Writeorwireimmdiesdy KLADAG RADIO LABORATORIES, KENT, O.

In our July issue, in reporting COMING IN SEPTEMBER - tests on the Wet "B" batteries furnished the RADIO AGE In- -An unusual bunch of surprises that the Editors of RADIO stitute by the Kelman Electric AGE have been saving for you all Summer. First, John B. Rath- Co., at Rochester, N. Y., inadver- bun, the "Man Who Makes the Blueprints," will have an exhaus- tently it was stated the jars were housedinawoodcontainer. RADIO tive article on "Thirty -Two Ways to Prevent Oscillations." That AGE is glad at this time to learn in itself ought to hold you for a while. Then such radio experts its error and to state the container as Roscoe Bundy, H. Frank Hopkins, Frank D. Pearne, Arm- is made of solid rubber, since strong Perry and Brainard Foote will reveal their new develop- obviously wood would not last for season. long as a container for lead plate ments the coming Are you ready? September issue batteries. out August I 5!

* Tested and Approved by RADIO AGE 96 RADIO AGE for August, 1925 The Alagazine of the Hour Solving the Question of I. F. Transformers (Continued from page 89) It is commonly accepted that a wavelength in the neighborhood of five to seven thousand meters is most satisfactory, preference being given to 5,000 meters, since transformers may be made more selective at this wave than at the longer ones. Obviously, a transformer wound with a large low -loss air -core coils, tuned by a low -loss condenser, would give maximum gain. Actually, it LEAK IT INTO THE GROUND! would be so sharp as to cut side -bands, ENJOY winter reception all and would have a terrific field, resulting summer! The Static Elimina- in instability and inability to use more Adaptable to coarse or tor -the newest and most startling than one or two such coils. The next fine tuning, the infinite thing in Radio -cuts out practically step is an air core transformer with precision oftheAccura- all static without loss of volume! smaller coils of higher resistance. How- tune brings all sta- ever, the same troubles prevail in a in And in addition it will help increase lesser degree until we resort to an iron tions within the scope selectivity, tune out local stations, sharpen core, which limits the transformer field, of your set clearly, signals, remove noises, lessen interference strongly, and with little and prevent re- radiation! broadens the curve to the desired width, and reduces amplification. If we go effort on your part. it with any receiving set -hook it up Use we in less than a minute and enjoy perfect further, and use a large iron core, get Easily substituted in a reception unmarred by static. a nice flat curve, wonderful reproduction, few minutes for ordi no selectivity, and no gain. is obvious Mail your order It nary dials without al- today. Satisfaction again that we must resort toa compromise, teration of your set. An guars teed. Money few and if this paper has brought out this single refunded att once, if paid essential accessory. returned within 5 point, the writer feels amply repaid, days. for it may be said that the necessity for Write for descriptive folder compromise between desirable theoreti- ` MYDAR RADIO CO. STATIC ELIMINATOR CO. cal extremes is an axiom of radio equip- 17 CAMPBELL STREET 483 United Bank Bldg., Cincinnati, O. ment engineers. Looking at the curves of Figure 1, we see A, B, C and D. "A" represents CCURATUNL the ideal transformer, giving infinite amplification over a 10,000 cycle band, yet at no other frequencies. "B" is an air -core transformer giving the highest possible amplification. It is useless, since it will not pass music and speech, and is subject to the physical limitations previously set forth. "C" is the practical ideal transformer, passing the desired frequency band with a gain variation Battery Prices insufficient to cause distortion, yet with a MASHED! limited field and good stability. "D" is To Consumers Only the extreme for perfect reproduction Here is a rest battery quality, - guaranteed to you at prices but gives no selectivity and no amplifica- that will astound the entire bat- The Famous Truly Portable tery-buying Order Di- * public. Put the tion to speak of. rect From Factory. Dealer's Profit in your own pock- TELMACO P -1 Receiver et. You actually save mucb more Work of Seven than half, and so that you can be Four Tubes Do the Construction Details convinced of true quality and perform - The peer of portables in size, weight, ease of tuning, ane a give a Written S- Year Guayan¡ selectivity, distance, volume, workmanship and price. SUPPOSE we wish to construct "C", tee. H re is your protection! No need to Aerial, loud speaker and batteries self contained. take a chance. Our battery is rigbt- and Complete with tubes and batteries, $125.00 which is the best transformer we the pace rs lowest ever made. Convince $143.50. Receiver only . can build practically. We will require a yourself. Read the prices! Auto Batteries Radio Batteries P -t Kit Saves You Money? Volt.100Amp.S9.50 bobbin turned out of wood or built up 6Von. tl Pl.te.59.50 1.50 Our offer of the Telmaco P-1 Receiver In kit form hm 5v,It.ss PIata.111.50 6VOtt.120 AmD--13.00 met with enthusiastic reception. Tbie o tains all of fibre, together with two pieces of core 12Volt, l Pl.te,13.00 6Volt.140lime part,, se built by us including case, drilled and em Buy Direct -Send No Money graved panel, and illustrated rnatructions. $80.00 iron as shown in Figure 2. This bobbin We ask no deooeit. Sim ly send 0.m. and ad- Complete kit s dealer.), write ne. folder free. someday Weyreelveyoy rder Explresss C.Ó.D. Ask your Deecriptive is wound with 1,400 turns of No. 36 SSE barrittÌ `Radio Division: on Ouexamination in the smaller slot for the primary, and h battery. Weclów S'I withor- Co. for comb in full with or- Telephone Maintenance 3300 turns of the same wire in the larger der. yYou cannot h eel DI. yWl order today 20 So. Wella St. Dept. c Chicago, slot for the secondary. The core is put ÑÓ ARROW BATTERY CO. in so that the air -gap comes under the Dept. 11. 1215 50. Wabash Ave.,Chlcago yislity 'Kadin exclusively ' established 1918 larger or secondary coil, and the ends of the laminations are bent over each other to hold them together. This transformer may be placed in a small metal can, with leads brought out as desired. It A regular $25 loud speaker for $16. Loud, clear, mellow tone. should first be boiled in a resin -bees -wax Bell t3g in. diameter, horn compound, with which the can should be SALESPEAKER 22 in. high, equipped with most interesting Lakeside Adjustable Unit. filled. is the name of the Agents wanted, write for par. radio bulletin published If you are a ticulars. This transformer, while selective, 'nay dealer, we will mail you a copy, on be used in conjunction with another request. Lakeside Supply Co. best type, which would be a compromise HUDSON -ROSS -116S. Wells St. 73 W. Van Buren St., Chicago Chicago between "B" and "C". J Tested sad Approved by RADIO AGE RADIO AGE for August, 1925 The Magazine of the Hour 9 This latter transformer may be built by turning out a wood spool. In the bottom of the slot are wound 250 turns of No. 30 DSC wire. On top are wound 1,500 turns of No. 36 DSC wire, forming the secondary. This coil has an air core, and cuts side bands slightly. Using but l p by one, this is not noticeable, but the use of two or three would be out of the question ,S attestedetets field man{ for reasons outlined above, in addition e a d e rtam so to this latter one. the et L4 ` Now that we have these transformers, ghop t we cannot use them unless they are Paceo ti {oá q4meot properly matched. Such a step will of t Staáa of as dealerline insure co- ordinate operation at all times. th tn Ask yourrpete us e co t Parts. CRISS-CROSS "Don't THE COUNTRY WITH Improaise- promiPr Pacentize" 5TU8E Trade Bara Chicago RADIO ESSENTIALS St. Louis Washington Boston San Francisco PACENT ELECTRIC COMPANY, Inc. Birmingham Philadelphia Buffalo Jacksonville 91 Seventh Ave., New York City Detroit Something decidedly new, different. and better has been perfected in radio. Inter - Minneapolis Canadian Licensees, White Radio Ltd., Hamilton, Ont. Pittsburgh eating information is ready for you. Write us nt once. PREMIER ELECTRIC CO. Dept. J -21, 1800 Grace St., Chicago, III. Premier Electric Co., geA Dept. J -21. 1800 Grace St., Chicago. Illinois. Pend me immedierely full information about the new Premier Euemb's. This does not obligate me. ReIO gig MoneySav lag Radio Catalog EXPERT containing a theueand bargains of every- Name thing In radio; parts. supplies. complete parts for eets,cornplete sets. Address EARN etc.. etso a mine of very latest information on all dif- City Stata $50 to $200 a Week ferent circuits.. complete list See navel of tlone and Free dhow mm:nhygwondertmmont' °maki nho t unities are waiting for you an a Trained Expert valuable,'ing st lo [he iivest, fastest growing Big Pay held ie Easy to build your own radio the world -RADIO! set. All Complete parts of Bete Book et of standard advertised Superdon Radio Set FREE guaranteed and inelnde Long distance ppeer- powerful select. parts I radio set FREE to every student drilled bekellte panel,' and wh- e who sub sowi Not acent extra charge. ile diagrams for espy eseemhling Mite --1?eeÓ 3:cT Everything guren teed .n mener ^emu amae cee°d;cklyyinthe Service Department fat par business also bow tb agis o ,Our Fuelev u the dertm sweeaó Sàvê 2 iO 3 Send name. address for free cata. THE cost. at once -Newt No oblliigation. em names of friends; we will mail them catalogs. RANOIINI ORATION 646N.MIchlgan Ave , Oept 99, Chicago 169 North Union Avenue.AOvos 044 CHICAGO su RAMPLIFIER IPI The tide has turned -Resistance Coupled Amplification is here to stay and is now riding the "top- RADIO AGE FOR ONE YEAR AND 1925 RADIO most wave" of popularity. The D avon Super Amplifier d AGE ANNUAL-BOTH FOR $2.50! t Amplifier Kit combined with the Here is a bargain! For a limited period only, we are offering RADIO D awn High Mu Tubes will give AGE and the RADIO AGE ANNUAL for 1925 at the astoundingly low to any receiver that super amplification you demand. figure of $2.50. First orders will be filled first. Act now if you want this amazing value. Fill out below and send in: The Super Amplifier $15.00 it High Mu Tubes Mu20 1.00 Radio Age, ------Daven Power Tubes Mu -6 5.00 3Stage Amplifier Kit ...... 9.00 500 N. Dearborn St., Chicago, 111. Sold of Good Radio Stores Enclosed is $2.50, (stamps, money order or cash,) for which send me RADIO Reed the Resistor Manuel. From AGE for one year beginning with the current issue, and the Your Dealer, 25e: Postpaid. 35c. ANNUAL for 1925. Name fflG Fn. s..w.r Address. '04118NA81 Q'6d8tQhrt'16N sr City and State NEW

WANTED -CHICAGO REPRESENTATIVE Manufacturer engaged in the making of kit, radio set and loud speaker desires Chicago distributor with financial and merchandising responsibility to handle exclusive representation in Chicago. Dealers to be given exclusive territory. Price and quality will be maintained. This is a desirable connection i' W X for the right party. is kind of easy to get with the right Address H-8, ' set. Profits are easy to get with the right -Box kind of goods. Dealers write for facts. Radio Age, HUDSON -ROSS -116 S. Wells St. 500 N. Dearborn St., Chicago, Ill. Chicago

F Tested atol Approved by RADIO AGE * 9S It.\I)IO .\GI'. for August. 1925 The Magazine of the Hour Corrected List of Broadcasting Stations

KOKA W..tioshonse Electric k Mfg. Co Eeet Pittsburgh. Pa. 309 KFVH When Radio Shop (Herbert Whim) Manhattan. Kansas 218 KDLR Radio Electric Co Devils Lake. N. D. 231 KFVI Headquarter. Troop. 56th Cavalry Houston, Texas 248 KDPM Westinghouse Electric & Mfg. Co Cleveland. Ohio 270 KFVJ First Baptist Churob San Jose, Calif. 228 KDYL Newhouse Hotel Belt Lake City, Utah 250 KFVK Sacramento Chamber of Commerce Sacrament, Calif. 248 KDZB Frank E. Siefert Bakersfield, Calif. 240 KFVL Lt. Richard F.Lue.ier,Ith Iof. U. B.A., Vancouver Barroaka.Vaneou er. Wash. 231 KDZI Elect:le Supply Co Wenatchee. Wash. 380 KFVN Carl E. Begley Welcome. Minn. 227 KFAD McArthur Bros. Mercantile Co Pboeoi.. Arix. 273 KFVO F. M. Henn Kirksville. Mo. 228 KFA[' Biste College of Washington Puliamo. Wash. 358 KFVR Moonlight Ranch Route 6. Denver. Colo. 248 KPAF Western Radio Corporation Denver. Colo. 278 KFVS Cape Girardeau Battery Station Cape Girardeau. Mo. 224 KFM University of Colorado Boulder. Colo. 380 KFVY Radio Supply Co Albuquerque. N. M. 250 KFAN University ol Idaho Moscow. Idaho 230 KFVZ Glad Tidioge Tabernacle San Francisco, Calif. 234 KFAU Boise High School Boise. Idaho 271 KFWA Browning Bros. Co Ogden. Utah 214 KFAW The Radio Den (W. B. Ashford) Santa Ana, Calif. 280 KFWB Warner Bros. Hollywood. Calif. 252 KFRB F. A. Buttrey k Co Havre. Moot. 380 KFWD Arkansas Light k Power Co Arkadelphia. Arkansas 288 KFBC W. K. Achill Ban Diego, Calif. 278 KFWH F. Wellington Mone, Jr. Chico. Calif. 254 KFBG First Presbyterian Church Tacoma. Wash. 250 KFWI Radio Entsrtainmcoc. Inc.. South Sen Francisco. Calif. 220 KFBK Kimbell -Upson Co Sacramento, Calif. 283 KGB Tacoma Daily Ledger Tacoma. Wash. 252 KFBL Leese Bros Everett. Wseh. 224 KGG General Electric Co Oakland. Calif. 381 KFCB Nielson Radio Supply Co Phoenix. Arie. 238 KGU Marion A. Mulrony Honolulu. Hawaii, Waikiki Beech 370 KFCF Frank A. Moon Walla Wells. Wash. 288 KGW Portland Morning Oregonian Portland, Oreg. 491 KFCZ Omaha Central Rich School Omaha. Nehr. 258 KGY St. Martine College (Rah. Sebastian Ruth) Loy, Wash. 253 KFDD St. Michael. Cathedral Boise. Idaho 252 KHJ Times- Mirror Co. Lee Angeles, Calif. 408 KFDH University of Arisons Tusoon, Arie. 388 KHQ Louis Wesmer Seattle ,Wesh, 273 KFDJ Oregon Agricultural College CorvaWe. Ores. 284 KJR Northwest Radio Service Co Seattle, Wash. 384 KFDM Magnolia Petroleum Co Beaumont, Texas 318 KJS Bible Institute of Los Angeles. Inc. Lee Angeles. Calif. 293 KFDX First Baptiet Church Shreveport. La. 380 KLDS Reorgaoiaed Church of Jesus Christ of Latter Day Saints..Independenc.. Mo. 441 KFDY Routh Dakota State College Brookings, S. Dsk. 380 KLS Warner Brother. Radio Supplies Co Oakland. Calif. 242 KFDZ Harry O. Iverson Minneapolis. Minn. 231 KLX Tribune Publishing Co Oakland, Calif. 508 KFEC Meier k Frank Co Portland. Ong. 248 KLZ Reynolds Radio Co Denver, Colo. 283 KFEK Augshury Seminary Minneapolis, Minn. 281 KMJ San Joanuio Light A Power Corp Fresno. Calif. 243 KFEL Winner Radio Corp Denver. Colo. 254 KMO Love Electric Co Tacoma. Wash. 250 KFEQ J. L Soroggin Oak. Nebr. 288 KNX Lon Angela. Evening Exprene Los Angeles. Calif. 337 KFER Auto Electric Service Co Fort Dodge. Iowa 231 KOA General Electric Co Denver. Colo. 323 KFEY Bunker Rill a Sullivan Mininc and Concentrating Co Kellogg. Idaho 233 KOR New Mexico College of Agriculture k Mechanic Ara. State College, N. Me :. 348 KFFP First Bepti.t Church Moberly. Mo. 28 KOP Detroit Police Department Detroit. Minh. 286 KFFV Ormeland College Lamont Iowa 280 KPO Hale Bro. Ban Franoieco.Callf. 428 KFGB Heldbreder Radio Bnpply Co Utica. Neb. 224 KPPC Passdeos Presbyterian Church Pasadena, Calif. 229 KFGC Louiefana State University Baton Rouge. La. 284 KPRC Houston Pot-Dispatch Houston. Texas 270 KFGD Chiokeshs Radio A Electric Co Chickasha. Okla. 248 KQV Douhlda.v -Hill Eleetrio Co Pitaburgb, Pa. 270 KFGH Leland Stanford University Sanford University. Calif. 273 KOW Charles. D. Herrold Sm Jose. Calif. 228 KFGQ Cary Hardware Co. Boone. Iowa 228 KRE V. C. Battery A Electric Co Berk.l.y,Calif. 275 KFHA Western Sat. College of Colorado Ounoieon, Colo. 282 KSAC Kansas Sate Agricultural College Manhattan, Kens. 341 KFHH Ambrose A. McCue Neat Ray. Wash. 281 KSD Post Dispatch (Pulitzer Pub. Co.) St. Loua, Mo. 545 KFHL Peon College Oskaloo.. Iowa 240 KSL Radio Servies Corp. ol Utah Bolt Lake City. Utah 299 KFI E. C. Anthony. Inc Los Angeles. Calif. 488 KTCL American Radio Telephone Co.. Inc Seattle. Wash. 308 KFIF Benson Polyaohoio Institute Portland. Oreg. 248 KTHS New Arlington Hotel Co Hot Springs. Ark. 375 KFIOQ North Central High School Spokane. Wash. 252 KTW First Presbyterian Church Seattle. Wash. 455 First Methodist Church 242 KUO Examiner Printing Co San Francisco, Calif. 248 KFIU Alaska Electric Light A Power Co. Juneau, Al.. 228 KUOM Sate University of Montana Missoula. Montana 244 KF1X Reorganled Church of Jesus Christ of Latter Day Saints .Indepondenc., Mo. 240 KWG Portable Wireless Telephone Cn. Stockton. Calif. 248 KFIZ Daily Commonwealth and Omar A. Huelemsn Fond du Lao. Wis. 273 KWKC Wilson Duncan Studio. Kansas City. Mo. 238 KFJB Marshall Electrical Co Marshalltown. lows 248 KWWG City of Brownsville Brownsville Texas 278 KFJC R. B. Ferran (Episcopal Church) Junction City. Kansas 219 KYO Eleetrio Shop Honolulu. liawali 270 KFJF Nations' Radio Manufacturing Co Oklahoma City. Okla. 252 KYW Weetioghouee Electric k Mfg. Co. Chicago. Ill. 835 KFJI Liberty Theatre (E. E. Morals) Astons, Ores. 252 KZM Preeton D. Allen Oakland,Calif. 242 KFJL Hardsasg Manufacturing Co Ottumwa. Iowa 242 WAAB Valdese( Jensen New Orleane.La. 283 KFJM University of North Dakota Grand Forks. N. Dak. 280 WAAC Tulane University New Orleans La. 278 KFJR Ashley C. Dixon a Soo Bavemville. Mont. 258 WAAD Ohio Mechanics Ieetitute Cincinnati, Ohio 248 KFJX Iowa Sate Teacher's College Cedar Falls, Iowa 280 WAAF Chicago Daily DrovereJoumal Chicago. Ill. 288 KFJ Y Teamed! Radio Co Fort Dodge, Iowa 248 WAAM I. R. Nelson Co Newark, N. J. 383 KFJZ W. E. Branch Fort Worth. Texas 254 WAAW Omaha Grain Exchange Omaha. Nebr. 285 KFKA Colorado State Teacher. College Greeley. Calo. 273 WABA Lake Forest University Lake Forest Ill.. 227 KFKO Conway Radio Laboratories (Ben H. Woodruff) Conway. Ark. 250 WABB Harrisburg Sporting Goode Co Herrleburg.Pa. 288 The University of Ksmse Lawrence. Kans. 275 W ABC Asheville Battery Co.. Inc Asheville. N. C. 254 KFICX Westinghouse Electric I Manufacturing Co. Hastings, Nebr. 288 WABI Bangor Railway k Eleetrio Co Bangor. Me. 240 KFLD Paul E. Oreenlaw Fmokllatoa, La. 234 WAHL Connectiout Agricultural College Born.Conn. 283 KFLP Everett M. Foster Cedar Rapide. Ia. 258 WARN Ott Radio. Inc LaCrosse. Wis. 244 KFLR University of New Mexico Albuquerque,New Mexico 254 WARD Lake Avenue Baptiet Church Rochester, N. Y. 283 KFLU Rio Grande Radio Supply House San Benito, Texas 238 WABQ Haverford College. Radio Club Haverford. Pa. 281 KFLV Rev. A. T. Pre m. . Rockford. BI. 229 WARR Scott High School. N. W. B. Foley Toledo. Ohio 270 George Roy Clough Galveston, Texas 240 WABU Victor Talking Machine Co Camden. N. J. 224 KFI.Z Atlantic Automobile Co .Atlantic. L. 273 WABW College of Wooster Wooster. Ohio 234 KFMB Christian Churches Little Rock, Ark. 254 WBAX Henry B Joy Mt. Clemens. Mich. 270 KFMQ University of Akrens.. Fayetteville. Ark. 299 WABY John Mageldi, Jr Philadelphia, Pa. 242 KFMR Morninnide College Sioux City. Iowa 281 WABZ Coliseum Place Baptist Church New Orleans. La. 283 KFMT Dr. George W. Young Minneapolis. Minn. 231 WADC Allen T. Simmons (Allen Theatre) Akron. Ohio 258 KFMW M. O. Bsteren Houghton. Mieb. 288 WAFD Albert B. Parlez Co Port Huron, Mieb. 233 KFMX Carleton College Northfield. Minn. 338 WAHG A. H. Grebe k Co Richmond Hill, N. Y. 315 KFNF Henry Field Seed Co. Shenandoah. Iowa 288 WAMD Hubbard sad Co Minneapolis. Minn. 244 KFNG''Wooten e Radio Shop Coldwater. Mis. 254 WBAA Purdue University W. Lafayette. Ind. 283 KFM' L. A. Drake Battery and Radio Supply Shop Santa Ross. Calif. 234 WBAC Clemson Aerie. College Clemson College. S. C. 331 KEGA Rhodes Department Store Beattie. Wach. 454 WRAH The Dayton Co Minneapolis, Minn. 417 KFOC First Christian Church Whittier, Calif. 238 WBAK Pennsylvania State Police Harrisburg. Pa. 278 KFOJ Moberly High School Radio Club Moberly. Missouri 248 WRAC, Jemes Milliken University Decatur. Ill. 380 KFOL Leslie M. Schsfhueh Marengo, Iowa 234 WBAP Wortham -Carer Publishing Co. (Bar Telegram) Fort Worth. Texas 478 KFON Eohopbone Radio Shop Long Beech. Calif. 234 WRAV Erner k Hopkins Co. Columbus. Ohio 292 KFOO Latter Day Saints University Salt Lake City. Utah 281 WBAX John H. Stenger. Jr Wilkes- Barre. Pa. 254 KFOP Rohrer Eler. Co.. Marshfield. Ore. 240 WBAY Western Electric Co New York.N.Y. 492 KFOR David City Tire A Electric Co David City. Nebraska 228 W BBC Irving Vermilya Mstapoaett. Magie. 248 KFOT College Hill Radio Club Wichita. Kansas 231 WBBL Grace Covenant Presbyterian Church Richmond, Ve. 283 KFOX Board of Education, Technical High School Omaha. Nebraska 248 WBBM Atless Investment Co Chicago, Ill. 228 KFOY Beacon Radio Service St. Paul. Minn. 228 WBBN Blake. A. B Wilmington, N. C. 275 KFPG Garretson and Dennis Les Angeles. Calif. 238 WRAP Petoskey Hush School Petoskey, Mich. 248 KFPL C. C. Baxter. Dublin, Texas 242 WRRR People. Pulpit Mao Roseville. N. Y. 273 KFPM The New Furniture Co. Greenville.Texas 242 WRBS First Haptiet Church New Orleaps,Ls. 252 KFPR Loa Aocd.s Co. Forestry Dept Los Angeles. Calif. 231 WBBU Jenks Motor Sales Co Monmouth. Ill. 224 KFPT Cane k Jobn.= Salt lake City. Utah 288 WBBV Johnstown Radio Co. Johnstown, Pe. 245 KFPV Heists A Hollimon, Inc. Ban Francises. Calif. 238 WRBX Rufoer Junior High School Nor folk. Va. 222 KFPW St. Job. M. E. Church. Carterville. Mo. 288 WRBY Washington Light Infantry Co. "B" 118th Inf Cherle.ton,S.C. 288 KFPY Svmon. Investment Co Spokane. Wash. 283 WRCN Foster k McDoland Chicago. Ill. 288 KFOA The Priacinie St. Louie, Mo. 284 W BDC Baxter Laundry Co Grand Rapids. Mfah. 258 KFQR The B..rehligbt Publishing Co. Fort Worth. Texas 221 WBES Bliss Electrical School Takome Perk Md. 222 KFOC Kidd Brothers Radio Shop Taft. Calif. 258 WBGA Jones Elec. k Radio Mfg. Co Baltimore Md. 254 KFQH Radio Service Co. Burlingame. Calif. 231 WBOQ A. H. Grebe A Co., Inc Richmond Hill, N. Y. 238 KFOP G. 9. Carson, Jr. ..Iowa City. Ia. 284 WBR Pennsylvania Sate Police Butler. Pa. 281 KFOR Walter LaFayette Ellis Oklahoma City, Okla. 220 WBRC Bell Radio Corporation Birmingham, Ala. 248 KFOT Texas National Guard Deooises , Texas 252 WBRE Baltimore Radio Exchange WBkee -Bene. Pa. 231

KFOU W. Riker - Holy City. Calif. 253 WBS D. W. May. Inc Newark N. J. 252 KFOW (. F. Knierim North Bend. Wash. 248 WBT Southern Radio Corp Charlotte,N.C. 278 KFOY Farmers Sate Bank Belden. Neb. 273 WBZ Westinghouse E. k M. Co Springfield, Ma.. 333 KFOZ Taft Radio Co Rollywood, Calif. 240 WCAD St. Lawrence University Canton. N. Y. 280 KFRC City of Paris Dry Goode Co. San Francisco, Calif. 288 WCAE Kaufmann a Baer Co. and 7 he Pittsburgh Pree Pitahurgh,Ps. 481 KFRM James F. Boland Fort Sill. Okla. 283 WCAG Clyde R. Randall New Orleans. La. 282 KFRU Etheric.l Radio Co. Bristow. Okla. .394 WCAH Entrekin Electric Co. Columbus. Ohio 258 KFRW United Churches of Olympia Olympia. Wash. 220 WCAJ Nebraska Wesleyan University University Place. Nebr. 283 KFRX J. Gordon Klemgard Pullman. Wah. 217 WCAL Bt. Olaf College Northfield, Minn. 338 KFRZ The Electric Shop Harrington. Nell. 222 WCAO Sander. k Sayman Co Baltimore Md. 278 KFSC Angelus Temple Los Angeles, Calif, 272 WCAP Chesapeake k Patenta Telephone Co Washington. D. C. 111111 KFSY The Van Mariam Ce. .. Helena, Mont. 281 WCAR Alamo Radio Electric Co. Ban Antonio. Tens 283 KFUJ Kopper Plumbing and Heating Co Breckenridge. Minn. 242 WCAS W. H. Duowoody Industrial Institute Minneapolis. Minn. 280 KEUL Thom.. Ooggan k Bro.. Music Co. Galveston. Texas 258 WCAT State College of Mines Rapid City, S. Dsk. 240 KFUM W. D. Corley Colorado Spring.. Colo. 242 WCAU Durham A Co Philadelphia,P.. 278 KFUO Concordia Seminary St. Louis. Mo. 549 WCAX University of Vermont Buclbgtan,Vt. 250 KFUP Fitesimmooe General Hospital Denver. Colo. 234 WCAZ Carthage College Carthage.Ill. 248 KFUQ Julius Brunton and Sons Co Sap Francineo, Calif. 234 WCBA Charles W. Heihathm Allentown. Pa. 280 KFUR H. W. Pe.ry and C. Redfield Ogden. Utah 224 WCBC Uoiversity of Michigan Ann Arbor. Mich. 280 KENS toe. L. Sherman Oakland. Calif. 233 WGBD Wilbur C. Voliva Zion. Ill. 344 KFUB University of Utah Sit Lake City, Utah 271 WCBE Uhalt Radio Co New Orlesns,La. 383 KFUU Colhurn Radio Labe. San Leandro. Calif. 231 WCBF Paul J. Miller Pittsburgh. Pa. 338 KFUY Irvine M. Bouchard Butte. Mont. 284 WCBG Howard S. Williams (Portable) Pmasgoua. Mae. 288 KFUZ Y. M. C. A Virginia. Mao, 244 WCBH University of Mie. Oxford. Mlee. 242 KFVC Ben.herge Music Co Camden. Arksmse 248 WCBM Charles Swan Baltimore. Md. 229 KFVD MoWhlrsnle Electric Co San Pedro. Calif. 202 WCRN James P. Boland Ft. Beni. Harrison. Ind. 288 KEVE Film Cornoraslon of America St. Louis. Mo. 245 WCBQ First Bootie Church Nashville ,Tenn. 238 K VF (lacenre R. Juneau Hollywood. Calif 208 WCBR C. H. Meeeter Providence, R. I. 248 KFVG First M. E. Church Independence. Kanese 238 WCBT Clark University, Colonists Dent Worcester, Maso. 238 RADIO AGE for August, 1925 The Magazine of the Hour 99 Radio Test Trip To Begin in Findings to be Broadcast apparatus will include both transmitting Communication with Eastern and and receiving equipment. This informa- August Pacific broadcasting stations will be tion will also be given to the-radio public While other radio engineers are ex- maintained throughout the long trek, through RADIO AGE, to guide the which is to be made by automobile. fans who desire improved reception or ploring and testing atmospheric condi- who tions to the Arctic and in the tropics, Several radio stations have expressed are far from strong stations and are H. Frank Hopkins and Harvey T. Kelley, a desire to broadcast the findings of the troubled with such disturbances as Assoc., I. R. E., plan to make an exten- expedition to guide them in reaching fading, static and other radio phenomena. sive survey of transmitting and receiving listeners in isolated districts of the coun- Mr. Hopkins and Mr. Kelley have long conditions in America's own front yard. try, where difficulty is experienced in been identified in radio circles, ever since They will leave Chicago some time during maintaining consistent touch with broad- the days of the old spark transmitter and August on a trip through the territory casters throughout the year, and espe- before vacuum tubes were used for re- west of the Mississippi River in an effort cially in Summer -time. ceiving purposes. They have done con- to trace the causes of difficult Summer Mr. Hopkins and Mr. Kelley intend siderable research work and development reception and discover remedies for to devise several new types of radio and as a result the findings of their trip existing conditions. apparatus to meet the difficulties they should be of interest to all persons con- expect sciences. Their trip will first take a northerly will confront them. This new nected with radio and its allied direction, and will gradually return south and west to Colorado and Utah. From there the two engineers will head Northwest to the state of Washington, THE NEW RADIO TUBE down the coast through Oregon and Designed Especially For Resistance California, and eastward through Arizona New Mexico, Texas and so on until they again arrive in Chicago about six months COUPLED AMPLIFIERS later. Tested and Approved by RADIO AGE Their findings will be revealed regularly HI-CONSTP.ON throughout the long journey, and it is Type C. T. 101A expected they will be of great value to Another Cleartron product-the tube that gives greater volume, better quality at one -third the plate voltage. Designed for Re- the radio public throughout the country. sistance, also Intermediate steps of Superhetrodyne and in Radio The largest mobile broadcasting set frequency receivers. ever transported in such a manner will AMPLIFICATION CONSTANT 20 be part of the radio equipment to be (Almost 3 times that of 201A) carried on this trip, in order to test radio transmission in so-called "dead spots" 5 VOLTS AMP. and in places where static disturbances Price $3.00 and other natural interference prevail. Manufactured by Under these extremely adverse conditions an attempt will be made to determine just what kind of radio receiving circuit performs the best. Several types of You can't loose, for circuits will be taken on the trip and Cleartron is backed with ironclad guar- tested under varying atmospheric and antee to make good. 28 WEST 44th ST. NEW YORK geographic conditions. cllie Official ZS .R.M.A.J'how The Great THE S OND Manufacturers' Exposition. RADIO(WUÙ»S FAIR Attended by N E O RK ITV Leading U. J. HERRMANN, MANAGING DIRECTOR Jobbers and 14th 19th Dealers SEPTEMBER. to MONDAY NOON TO SATURDAY MIDNIGHT ENTIRE EXHIBITION ON GROUND FLOOR IN THE LARGEST HALL IN THE WORLD NEW YORK OFFICES ,too TIMES BLDG NEW Von CITY 258th Field Artillery Armory

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* Tested and Approved by RADIO AGE 100 RADIO AGE, for August, 1925 The Magazine of the Hour

WCBU Arnold Wireleo Supply Co Arnold. Pa. 254 WIAS Hume Electric Co Burlington Iowa 283 WCBX Radio Shop of Newark (Herman Lubimky) Newark, N. J. 233 WIBA The Ce.pitei-Times Studio Madison. Wis. 236 WCCO Washburn- Croshy Co Twin Minn. WIBC L. M. Tue Pmt. No. 39. Venn. of Foreign Wen.... St. Petersburg. Florida 22? WCEE Chari. E. Erbstein, Villa Olivia ntry Elvin, Ill. 278 WIBD X -L Radio Enrolee Joliet. Illinois 200 WCK stir -Bast-Fuller D. G. Co 8t. Louis. Mo. 275 WIBE Maniashurg Radio Broadcesttva Co Mertinahuro. W. Va 210 WCTS C. T. Scherer Co Worcester. Mass. 268 WIBF 8. P. Miller Dance Activities Wbeatlmd, Wise. 231 WCX Free Press Detroit, Mich. 516 WIBG St. Paul'. Protestant Episcopal Church Elkiee Park, Pa. 222 WDAE Tempo Doily Times Tampa. Fla. 365 WI BO Nelson Brothers Chicago, 111. 226 WDAF Kansas City Star Kansas City. Mo. 365 WIBH Elite Radio Storm New Bedford. Macs. 209 WDAG J. Laurence Martin. Amarillo. Texas 263 WIBI Frederick B. ZitteU, Jr Flushing. N. Y. 219 WDAH Trinity Methodist Church (South) EI Paso. Texas 268 WIBJ C. L. Carrell (Portable) Chicago, Ill. 216 WDAR Lit Brothers Philadelphia, Pa. 394 WEEK Univenity of Toledo Toledo, Ohio 205 WDAY Radio Equipmeot Corp. Fargo, N.Dak. 244 WIBL McDonald Radio Co.. Portable Station Joliet, III. 2157 WDBA Fred Ray Columbus. Ga. 236 WI BP First Presbyterian Church Meridian. Mim 210 WDBB A. H. Weite & Co.. Inc Taunton. Mass. 229 WIRR Thurman A. Owings Weirton. W. Va. 246 WDBC Kirk. Johnson & Co Lancaster, P. 258 WEBS New Jersey National Guard, Edon. Co. 57th Iof. Brig.. 921 Edgwood Road, WORD Herman Edwin Bur. Martlnahur8, W. Va. 268 Elizabeth, N. J. 202.6 WDBE Gilliam- Schoen Elec. Co Attancio. Ga. 278 WIBQ F. M. Schmidt Farina Dl. 205 WDBJ Richardson Wayland Electrio Corp Roanoke. Va 229 WIL Continental Electric Supply Co Washington. D. C. 360 WDBK M. F. Bros Cleveland, Ohin 227 WIP Gimbel Bros Philadelphia. Pa. 509 WDBL Wisc. Dept. of Markets Stevens Point, Wis. 278 WJAB American Electric Co Lincoln, Nebr. 229 WDBN Electric Light A Power Co .... Bangor, Me. 252 WJAD Jeckaon e Radio Engineering Laboratories Waco. Texas 352 WDBO Rollins College Inc Winter Park. Fla 240 WJAG Norfolk Daily News Norfolk. Nebr. 283 WDBQ Morton Rado Supply Co Salem. N. J. 234 WJAK Clifford L. White Greentowo, Iowa 254 WDBR Tremont Tempo Baptist Church Boston. Mass. 256 WJAM D. M. Perham Cedar Rapids. Iowa 268 WDBV The Strand Thutre Fort Wayne, Ind. 258 WJAR The Outlet Co. (J. Samuels & Bro.) Providence. R. I. 306 WDBX Otto Baur New York, N. Y. 233 WJAS Pittsburgh Radio Supply Hone. Pittsburgh, Pa. 286 WDBY North Shore Connegational Churcb Chicago. Ill. 258 WJAZ Chicago Radio Laboratory Chicago, E. 268 WDBZ Boy Scouts. City Hall IGngatown. N. Y. 233 WJBA D. H. Lentz. Jr Joliet. III. 207 WDM Church of the Covenant Washington, D. C. 234 WJBB L. W. McClurg St. Petersburg. Fla. 207 WDOD Chattanooga Radio Co.. Inc Chattanooga. Tenn. 256 WJBC Hummer Furniture Co. LaSalle, III. 234 WDWF Dutee Wilcox Flint. Inc Cranston, R. I. 441 WJBD Ashland Broadcasting Committee Ashland, Wisc. 233 WDZ J. L. B.h Tuscola. UL 278 WJBI H. M. Couch Joliet. IU. 2142 WEAA F. D. Follain Flint, Mich. 250 WJD Denison University Grenitevile. Ohio 229 WEAF American Telephone & Telegraph Co. New York. N.Y. 485 WJJD Supwme Lodge. Loyal Order of Moose Mo.ebeart, IU. 303 WEAR Wichita Board of Trade Wichita. Ka.. 280 WJY Radio Corp. of Ama New York. N.Y. 455 WEAL Cornell University Ithaca. N,Y. 286 WJZ Radio Corp. of Ama New York. N. Y. 455 WEAJ University of South Dakota Vermillon, S. Dak. 283 WKAA H. F. Paar Cedar Rapide. Iowa 278 WEAM Borongb of North Plainfield (W. Oiheon Bonfield) .. North Plainfield. N. J. 286 WKAD Chas. Louff (Crescent Park) East Providence, R. I. 240 WEAN Shepard Co Providence, R. I. 273 WKAP Dut.. W. Flint Cranston, R. I. 234 WEAO Ohio State University Columbus. Ohio 293 WKAQ Radio Corp. of Porto Rico Bu Juan. P. R. 340 WEAR Goodyear Tire wad Rubber Co - Cleveland, Ohio 389 WKAR Michigan Agriculture College East Lansing. Mich. 285 WEAU Davidson Bros. Co Sioux City. Iowa 275 WKAV Laconia Radio Club Laconia, N. H. 254 WEAY Iris Theatre (Will Horowitz, Jr.) Houston, Texas 270 WKBE K. h B. Electric Co Webstar. Mwsoho.ette 231 WEB Beowood Co. 8t. Lou.s Mo. 273 WKBF Dotes Wilcox Flint Cra.ten, Rhode Island 286 WEBA Electric Shop Highland Park. N. J. 233 W KBG C. L. Carrel. Portable Chicago. 111. 216 WEBC Welter Cecil Bridges superior, Wig. 242 WKY Wky Radio shop Okla. City. Okla. 275 WEBD Electrical Equipment and Service Co Anderson, Ind. 246 WLAG Cutting h Washington Radio Corp Minneapolis, Minn. 417 WEBE Roy W. Walker Cambridge. Ohio 248 WLAL First Christian Church Tula.. Okla. 250 WEBH Edgewater Beach Hotel, Chicago Evening Post Satin Chicagg111. 370 WLAP Wm. V. Jordan Louisville. K,. 288 WE/3J Third Avenue Rahway Co New York. N. Y. 273 WLAO Arthur E. Shilling Kalamazoo. Mich. 283 WEBM Radio Corporation of America Portahle 226 WLAX Putnam Electric Co Gresooutle,Ind. 231 WEBP E. B.Pedicord New Orle..., La. 280 WLB University of hiinnesou Minneapolis, Minn. 278 WEBT The Deytoo Coop. Industrial High School Dorton. Ohio 270 WLBL Wioconvn Stete Dept. of Markel Stteve.point, Wis. 278 WEBW Beloit College Beloit Wis. 283 WLS Sean Roebuck & Co Chime°. Ill. 344 WEEI The Edison Electric Illumtpatmg Co. Boston, M. 475 WLTS Lane Technical High School, 1225 Sedgwick Rood Chicago, Ill. 258 WEHS Robert E. Hughes Eve.too, fll. 205 WLW Croaky Mfg. Co Cineimstl Ohio 422 WEMC Benign Springs, Mich. 285 WMAC J. Edw. Page (Olive B. Meredith Cueoovia, N. Y. 261 WENR All -American Radio Corporation Chicago. Illinois 266 WMAF Rued Hills Radio Corp Dartmouth. Maas. 360 WEW St. Lour University Sa Louis, Mo. 280 WMAK Norton Laboratories Lockport. N. Y. 273 WFAA Dallas News & Dales Journal Daum, Te. 472 WMAL Trenton Hardware Co Trenton, N. J. 256 WFAM Times Publishing Co St. Cloud, Mann. 273 WMAN Finn Baptist Church Columh., Ohio 286 WFAV University of Nebraska. Department of Electrical Engineering. I6neolo. Nebr. 275 WMA9 Chicago Daily Newa Chicago, DL 447 WFBC First Sanitise Church Knoxville. Tenn. 250 WMA% Alabama Polytechnic Instituts Auburn, Ala. 250 WFBD Gethsemane Baptist Church Philadelphia. Pa. 234 WMAY Kiogahighway Presbyterian Church St. Louie, Mn. 280 WFBE John Van De Wade Seymour, Ind. 226 WMAZ Mercer University Macon. Ga 261 WFBC The Wm. F. Cable Co Altoona. P. 261 TrionTrianon Bell Room Chicago. nl. 250 WFSH Concourse Radio Coporatioo New York, N. Y. 273 W11./BF Miami Buell. Fla. 384 WFBJ St Johns University Collegeville. Minn. 236 Memphis. Tema. WFBQ Wynne Radio Co Raleigh. N. C. 255 WMCA Hormel MoAlp e (Greeley Square Hotel Co.) Citty 341 WFBIL Fifth Inf. Md. Nat" Guard. 5th Reg. Armory Baltimore. Md. 452 WMH AI.worth -Gate, Radio Co Cincinnati,ti, O. 321 WFBW Ainsworth -Gates Radio Co Cincinnati. Ohio 309 WNAB The Shepard Storm Boston,Maas. 250 WFBY Signal Officer Ft. Ben Harrison, Iod. 258 WNAC Shepard Stores Boston, Meer. 284 WFBZ Knox College Galesburg. Ill. 254 WNAD University of Oklahoma Norman. Okla. 258 WFI Strawbridge and Clothier Philadelphia. Pa. 394 WNAL Omaha Central High School Omaha, Nehr. 255 WFKB Frncl, K. Bridgman Chicago. LU. 217 WNAP Witteoherg College Springfield. Ohio 271 WFUV G. Porsoo Ward Springfield. Mo. 252 WNAR First Christian Church Butler. Mo. 230 WFUW Earl William Lewis Moberly, Mo. 233 WNAT Lemig Brother. Co. (Frederick Laanlg) Philadelphia. Pa. 254 WGAL Lanester Electric Supply A Co.tructioo Co Lancaster, Pa. 248 WNAX Dakota Radio Apparatus CO Yankton, S. Dak. 248 WGAQ YoureeRotel Shreveport. La. 252 WNYC Dept. of Plant and Structures New York, N. Y. 526 WGAZ South Beod Tribune South Bend. Ind.. 360 WOAC Page Organ Co Lime. Ohio 260 W G BB Harry H. Carman, 217 Bedell St Freeport, N. Y. 244 WOAE Midland College Fremont. Nebr. 280 WGBC Fiat Baptist Church Memphis. Tenn. 266 WOAG Apollo Theater Belvidere Amassment Co.) Belvidere. DI. 274 WGBF Fink Furniture Co Eve.ville,Ind. 217 WOAI Southern Equipment Co San Antonia Texas 392 WGBG Brietenbub'a Radio Bbop Thrifton, Va. 226 WOAN Vaughn Conservatory of Music (Jame. D. Vaughn) ....Lawrenceburg. Tenn. 280 WGBH Fall River Herald Puh. Co. (Portable) Fail River, Mess. 209 WOAO Lyradioo Mfg. Co Miehswaka, Ind. 369 WGBI Frank S. Mumma Summon, Pa. 240 WOAR Luodekow, Henry P Kenosha, Win 225 WG BK Lawrence Campbell Johnstown. P. 248 WOAT Boyd M. Hemp WUmiogtoo.DeL 360 WCBM Theodore N. 8utr Providence. R. I. 234 WOAV Pennsylvania National Guard, 2d Battalion. 112th Infantry.... Erie, Pa. 242 WDBL Elyria Radio Aaso. (Albert H. Ernst) Elyria, Ohio 227 WOAW Woodmen of the World Omaha. Nobuaki), 526 WGBQ Stout Institute Menominee, Wis. 234 WOAX Franklyn J. Wolff Trump, IN..N.J. 240 WGBR Marshfield Broadcasting Assn. Marshfield, Wu. 229 WOC Palmer School of Chlropractfc Dovanoort. owa 484 WG BS Gimbel Brother New York N. Y. 315 WOCL Hotel Jamestown Ina Jamestown. N. Y. 275 WGBT Furman University Greeoviile, S.C. 236 WODA James K. O'D.. Paterson. New Jene, 203 WGBX University of Maine Orono. Me. 252 WOI Iowa State College Ames. Ia. 207 WG BY Progress Sales Co R. R. No. 2 218 WOO John Wanameker Philadelphia, Pa. 509 WGES Corne Electrical School Oak Park. I11. 250 WOR L. Bomberger and Co Newark. N. J. 405 WGI American R. é R. Co. Medford Hillside. Mme. 261 WORD Peoples Pulpit Assn Beierte, III. 276 WG MU A. H. Grehe dr Co., Inc.. Portable Richmond Hill, N. Y. 236 WOS Stete Marketing Bureau Jefferson City, Mo. 440 WGN The Tribune Co Chicago, Ill. 370 WOWL Owl Battery Company New Orison., Is. 270 WGR Federal T. and T. Co. Buffalo, N. Y. 319 WOWO Main Auto Supply Co Ft. Wayne, Ind. 227 WCY General Elec. Co Schenectady N. Y. 379 WPAB Pennsylvania State College Biota College, Pa 283 WHA University of Wisconsin Madison, Wis. 535 WPAC Donaldson Radio Co Okmulgee, Okla. 360 WHAD Marquette University Milwaukee, Wu. 280 WPAJ Doolittle Radio Corp New Haven. Conn. 268 WHAG University of Ciocianmti Cincinnati, Obio 222 WPAK North Dakota Agricultural College Agricultural College, N. D. 283 WHAM Hafer Supply Co Joplin, Mo. 283 WPAL Superior Radio it Telephone Equipment Co. Columbus, Ohio 286 WHAM University of Rochester (Eestmao School of Music) Rochester, N. Y. 278 WPAZ John R. Koch (Dr.) Charleston. W. Va. 273 WHAP H. Alvin Simmons, 290 Flath.b Ave Brooklyn. N. Y. 240 WPG The Municipality of Axleutic City Atlantic Citi. N. J. 300 WHAR Seaside House Ati otia (Sty, N. J. 275 WQAA Horace A. Beale, Jr Parkersburg, Pa. 270 WHAS Courier-Journal A Leolsvita Times Louisville, Ky. 399 WQAC E. B. Gish Amarillo. Texas 234 WHAV Wilmington Electrical specialty Co Wilmington. Del. 360 WQAE Moore Radio Newa Station (Edmund B. Moore) Springfield. Vt. 275 WHAZ ' Rensselaer Polytechnic Institute Troy. N. Y. 385 WQAM Electrical Equipment Co. Miami, Fla. 283 WHB Sweeney School Co /Ceases City. Mo. 365 WQAN Scranton Timm Scranton. Ps. 280 WHBA C. C. Shaffer Off City, Pa. 250 WQAO Calvary Baptist Church New York. N. Y. 360 WHBB Nobel's Store Stevens Point. Wis. 240 WQAS Prince -Walter Co .. Lowell, Maas. 268 WHBC Rev. E. P. Graham Canton. Ohio 245 WQJ Calumet Ballabo Broedueting Co Chicago. Dl. 447 WHBD Chas. W. Howard Behefootaine, Ohio 222 WRAA The Rice Institute Ho.too. Texas 256 WHBF Basrdeley Specialty Company Rock bland. Illinois 222 WRAF The Radio Clash (Inc.) Laporte. Ind: 224 WHBG John 8. Skatre Harrisburg. Pa. 231 WRAK Economy Light Co Escanaba, Mich 256 WHBH Culver Military Academy Culver. Iod. 222 WRAM Lomhed College Cottrell... DI. 244 WHB.I Lauer Auto Co Ft. Wayne. Iod. 234 WRAP St. Luis Radio Service Co.. St. Laura, Mo. 263 WHBK Franklin St. Garotte. Inc EWw,orth, NI mine 231 WRAV Antioch College Yellow Springe, Ohio 242 WHBL James H. 8lucser Logansport. Iod. 220 WRAW Avenue Radio Shop (Horace D. Good) Reading. Pa. 238 WHBM C. L. Carroll. Portable Stalin Chicago. III. 233 WRAX Fumes Garage Ol000.eter City. N. J. 268 WHBN Fret Ave. Methodist Church St. Petersburg. Florida 258 WRBC Imaouel Lutheran Church Volpsrsioo, Ind. 278 W HBO Y. M. C. A.. Summer Street Pawtucket. Rhode Island 231 WRC Radio Corp. of Ama Washington, D. C. 468 WHBP Johnstown AutomohOe Co Joheotowo. Pemxylvania 256 WREO Rao Motor Car Co Lasing, Mich. 286 WHBO St. Joho. M. E. Ch inch Snth Memphis. Tenn. 233 WRHF WehIogton Radio Hospital Fund Wuhlegtoo, D. C. 256 W H BR Scientific Electric A Mfg. Co.. 3684 Vine St Cincinnati. Ohio 216 W RN Y Experimenter Publishing Co. New York. N. Y. 258 WHBS Edward Wm. Locke Mechaninhnrg. Ohio 208 WRK Doran Bros. Hamilton, Ohio 360 WHBU B. L. Binge Bons Anders. Ind. 218 WRL Union College 8ehs.ctsdy, N. Y. 270 WHBV Fred Rays Radio Shop Columbns. Ca. 244 WRM University of Illinois Urbana. DI. 273 WHEW D. R. Morale P1)iladelphia. Pa. 215 WRR Police and Fire Signal Department. Dallas. Texas 261 WHBX J. W. Bowser Punxkutawney, Pa 213 WRW Tarrytown Radio Res. iahe Tarrytown. N. Y. 273 WHEY St. Norbert's College West De Pore. We.. 250 WSAC Clemson Agricultural College Clemson College, S. C 336 WHEC Hickson Electric Co., Inc Roohestor, N. Y. 258 WSAG Laren Vnderheck Davis St. Petersburg, Fla 264 WHK Radiovox Company Clevelaod.OhIo 273 WSAI United Sates Playing Cerda Co. Cincinnati. Ohio WHN George Schubert New York. N. Y. 360 WSAJ Grove City College Grove City, 325 WHO Bankers, Life Co.. Des Moines. Ia. 526 WSAN AUeetown Call Publishing Co wllentowa Ps. 729 WHT Radiophone Broadcasting Corporation Deerfield. III. 238 WSAP Seventh Day Adventist Church New York, N. Y. 263 WIAD Howard R. Miller Philadelphia, Pa. 264 WSAR Douchtyd: Welch Electrical Co Fall River. Mw. 264 WIAK Journal -Stockman Co.. Omaha, Nebr. 273 WSAV C. W. VIA Radio Construction Co. Houston. Texas 360 WIAQ Chroniol. Publishing Co Merlon, Ind. 226 WSAY Irving A.tin (Port Chester Chamber of Commerce)...Port Cheater, N. Y. 233 RADIO AGE for August, 1925 The Magazine of Ille Hour 101 Standard Radio Receivers (Continued from page 87) The Anylite King Cole The Blair Receiver Receivers Employing Resistance -Coupled Audio Anylite King Cole radio sets will be Amplification and Tuned made for external batteries and may be Radio Frequency used with any standard tubes. The The Blair Six Tube Receiver, employ- cabinet is brown mahogany and the ing two stages of tuned radio frequency, panel black formica with gold trimmings. a detector and three stages of resistance - An outstanding feature is simplicity coupled audio amplification, is now 1.10 of control by means of two vernier dials. available to the American market. verywhere All reception is possible on a loud speaker. The Blair Receiver is the result of Selectivity is unsurpassed by any set, Amperite automatically controls tube cur- years of experimentation in both British rent. eliminates and coast to coast reception is possible American and repre- hand rheostats. Marnent under favorable weather conditions. and laboratories meters, guessing and all tube worry. sents the perfected combination of these Simplifies wiring, tuning and operation. The small amount of B battery current, two highly efficient methods of ampli- as low .002 long life Permits the use of any type of tube or any as amperes, assures fication; namely, tuned radio frequency combination of tubes. of batteries and low upkeep expense. for distance selectivity, re- Tested and used set is and and by more than 50 set manu- The non -radiating and all parts sistance- coupled_audio,for tone :quality. facturers and in every popular construe. are extremely efficient. The coils are tion set by far the most efficient we have ;been >e able to secure. RADIALL COMPANY King Cole sets are guaranteed against DepLRA.- B, 50 Franklin St., New York City defective material and workmanship, ,^m°°irrp Ttt:ay' Write for and when used with any good loud `7;F':>t FREE speaker will give ample volume and ex- JI Hook -ups cellent tones. Anylite King Cole audio frequency transformers are designed to give strong amplification and faithful reproduction TE over the entire musical range. These :The "SELF ADJUSTING "Rheortat transformers may be used with all stand- The result is the surpassing clarity of ard tubes and large, plainly marked delivery for which resistance -coupled terminals provide for secure connec- amplification is noted, together with tions. The cases are handsomely finished distance and volume in any quantity in black enamel and serve as a_shield for desired. the coil. Heretofore, the manufacturers of the Sales Distributor King Cole Transformers have been Blair Receiver have confined their sales developed after exhaustive research on efforts to the British market, and they Wanted the part of the Anylite Engineers; and are now one of the largest exporters of to start now in the fastest will give complete satisfaction. radio receiving sets in this country. growing business the world In choosing a receiving set for his ever knew -Three Million radio Majesty . King George V, the British lr engineers chose resistance -coupled ampli- sets were sold last year - fication. 22 Million will be sold in the The The Blair Receiver comes in mahogany U. S. A. Five Tube or walnut cabinets with sloping panels and three dials. The list price is $75.00. THE * Set which This set is being manufactured by the Blair Radio Laboratories, 23rd MUSIC BOX startled Street & 6th Avenue, New York City. the World. RADIO Foreign Visitors at N. Y. RECEIVER FRESHMAN Radio Show is the peerless seller of them all. Think! Only two orders MASTERNEct The undoubted leadership which the radio industry of the United States main- weekly means $600 per month. tains over those of other nations is Four orders $1200 per month. The Greatest Value reflected by the many foreign visitors who The Set with the Marvelous ire planning to come to this country for Tone and Volume Supreme, EVer Offered in A the Exposition to be held in Grand Central Palace during September. the Distance getter of them Radio Receiving Set A radio Festa, in which the leading all. Write now, today, for stars of the microphone will participate, our liberal 15-day trial offer At Authorized Dealers is planned for thelFourth Annual National and protected territory. Radio ¡Exposition by S. L. Rothafel, ("Roxy,") who will have charge of the THIELEN, Manufacturer entertainment program to be broadcast 1207 North Shore Ave., Chicago, from Grand Central Palace during Expo- e lier rraffic Cop sition Week. E. R. H E N D F pp of the jlir , y // Add a Fathead Wave' sY!ueCrr_/T!(uJ'- SEND NO MONEY! Trap to your Radio Set and aad"Police "yy nrrasep- --d Pnñed Fr a On Thank Cards noa. Regolata ual80. HYyear what YOU like. Stetiaas eled- Guaranteed to tone out kyOU^- "Get Away From any interfering station. ltink your ffavorite vtions. tMa Spe- Widely imitated but _rrv v . cial get ATTENTION. `o."$ the dRAGE. 00 10 Me Boys, You Bother Me" never equalled. The -ot,e 800-62.001 original d only suc- ..r._._w. s...... 15:00. ta,ddf Yvitth'ordr. is a ours. Our Salespeaker will cessful WA VETRAP.a favorite of MONEY REFUNDED If No Deilhted write for it. Now is its third year. eaed.. High Ntanaa. be a favorite of yours. Dealers Seat Postpaid upon enula grad. Ó. D. With 1st order. Shows all. city. S. Wells St. length, 4 dial settle., rte. Statica bet br HUDSON -ROSS -116 plus postage. Send for Free Booklet FREE LOG length. Distance map. Ripple cover. Chicago FERBEND ELECTRIC CO. Send no mosey- -pay po.tman when Va get cards etc. Order NOW! i E. So. Water St. - Chicago RADIO PRINTERS. Dept. C202. Marengo. In. * Tested and Approved by RADIO AGE 102 RADIO AGE for August, 1925 The Magazine of the Hour

WSAZ Chas. Electric Shop Pomeroy. Ohio 258 W TAR Relieve. Electric Co Norfolk.Ve. 280 WSB Atlanta Journal Atlanta, Ga. 428 WTAS Charles E. Erbstein Halo. III. 202 WSBC World Battery Co.. 1219 S. Wabash Ave., Chicago., 111.209.7 WTAT Edison Electric Illuminating Co (portable) Boston. M... 244 WSKC World's Star Knitting Co. Bay City, Mich. 261 WTAW Agricultural & Mecbanieal Collet* of Tease College Sutton, Txa 280 WSMB Saenser Amusement Co. and Maison Blanche Co New Orleans, La. 319 WTAX William. Hardware Co Streator. DI. 231 WSMH Shattuck Music Houe Owosso. Mich. 240 WTAZ Thom. J. MOOuire Lambertville. N. J. 283 WSMK B. M. K. Radio Corp Deylon, Ohio 275 WTHS Flint Beolor High School Flint, Mich. 218 WSOE School of Engineering Milwaukee. Wig. 266 WTG Ka.. Stau Agrisultural College Manhattan. Kane. 273 WSRF Herders Sal. end Service .Broedlands, ni. 233 WTIC Trevelere Insurance Co Hartford, Coon. 323 WSTA Camp Marienbad Ch.hem, N. H. 229 WTX H. 0. Seal Co Chicago, DI. 268 WSUI State University of low. Iowa City, Lowe 498 WWAD Wright at Wriebt (Inc.) Philadelphia. Pe. 360 WTAB Fall River Daily Herald Publishing Co Fall River. Mn... 268 WWAE The Alamo BW Room Joliet. Dl. 242 WTAC Penn Traffio Co Johnstown. Ps. 360 WWI Ford Motor Co. Dearborn, Mich. 273 WTAL Toledo Radio & Electric Co Toledo. Ohin 252 WWJ Detroit Newe (Evening New. Asen.) Detroit, Mich. 352 WTAP Cambridge Radio & Electric Co. Cambridge. Ill. 242 WWL Loyola Univeraite New Orlesna. Le. 260 WTAQ S. H. Vn Gordon á Son Osseo, WU. 220 WWOA Michigan Coles. of Mt,. Houghton. Mich. 244 Canadian Stations CFAC Calgary Herald Calgary, Albert. 430 CHXC J. R. Booth Ottawa, Ont. 435 CFCA Star Puh. & Prtg. Co Toronto, Ontario 400 CHYC Northern Electric Co Montreal, Quebec 410 CFCF Marconi Wireless Tales. Co. Cenad. Montreal. Quebec 440 CJBC Jarvis Baptist Church Toronto, Ont. 312 CFCH Abitibi Power & Paper Co.... Iroquois F.W. Ont. 400 CJCA Edmonton Journal Edmonton. Alberta 455 CFCJ Le Cis de L'Evenement Quebec. Quebec 410 London Free Pre. Prtg. Co London, Ont. 430 FCKC Radio Supply Co Edmonton, Alberta 410 CG.ICD T. Eaton Co Toronto, Ont. 410 CFCN W. W. Orant Radio (Ltd.) Calgary. Alberta 440 GCE Sprott -Shaw Radio Co Vancouver. B. C. 420 CFCQ Radio Specilties (Ltd.) Vancouver, B. C. 450 CJCF The News Record Kitchener. Ont. 295 CFCR Laur.ntide Air Service Sudbury. Ont. 410 CJCI Maritime Radio Corp Bt. John. New Brunswick 400 CFCT Victoria City Temple Victoria, B. C. 410 CJCK Radio Corp. of Calgary Calgary. Alta. 316 CFCU The Jack Elliott Radio Limited Hamilton. Ont. 410 CJCM J. L. Phillips Mont .1.11, Quebec 430 CFCW The Radio Shop London. Out. 420 Simons Agnew Q Co Toronto. Ont. 410 CFDC Spark. Co N.aimo. B. C. 430 úsc Evening Telegram Toronto. Ont. 430 CFHC Henry Birk. & So. Calgary, Alta. 440 CKAC La Pre.. Pub. Co. Montreal. Quebec 430 CFLC Ch.. Goy Hunter 561 Adelaide St., London, Ont. 410 CKCD Vancouver Daily Province Vancouver, B. C. 410 CFQC The Electric Shop (Ltd.) Saskatoon. Saskatchewan 400 CKCE Canadian Independ. T.lepbo. Co Toronto. Ont. 450 CFRC Queens University Kingston, Ontario 450 CKCK Leader Pub. Co Rettine. B.katcbewen 420 CFUC University of Montreal Montreal. Quebec 400 CKCO Ottawa Radio Association Ottawa. Ont. 440 CFXC Weetmi.ter Trust Co New Wetminat.r, B. C. 440 CKCX P. Bur. A Co Calgary, Albert* 440 CFYC Victor Wentworth Odium Vancouver, B. C. 400 CKLC Wilkinson Electric Company Calgary, Alberta 400 CHAC Radio Engin.r. Halifax, Nova Scotia 400 CKOC Wentworth Radio Supply Co Hamilton, Ont. 410 CHBC Albertan Publishing Co Calgary. Alberta 410 CNRA Canadian National Railway. Moncton. N. B. 313 CHCB Marconi Company Toronto, Ont. 410 CNRC Canadian National Railways Calgary. Canal. 357 CHCD Canadian Wireless & Elec. Co Quebec, Quehe. 410 CNRE Canadian National Railways Edmonton. Anal '455 CHCE Western Canada Radio Sup. (Ltd.) Victoria, B. C. 400 CNRM Candie. National Railway. Montreal, P. Q. 410 CHCL Vancouver Merchant. Exchange Vancouver, B. C. 440 CNRO Canadian National Railways. Ottawa. Ont. 430 CHCM Riley & McCormack Calgary. Alberta 415 CNRR Canadian National Railway. Regina, Bash. 312 CHCS The Hamilton Spectator Hamilton, Ont. 420 CNRS Canadian National Railways B.katoon. Seth. 329 CHIC Northern Electric Co Toronto. Ont. 356 CNRT Canadian National Railways Toronto, Ont. 357 CHNC Toronto Radio Research Toronto. Ont. 350 CNRW Canadian National Railway. Winnipeg. Man. 384 Cuban Stations PWX Cuban Telephon Co Habana 400 2K Alvera Due Habana 200 20W Pedro Zar. Habana 300 2HS Julio Power Habana 180 2AB Alberto S. de B.tamant. Habana 240 20L asar Collado Habana 250 20K Mario Cercla Vd« Habana 360 2WW Amadeo S... Habana 210 2BY Frederick W. Gorton Habana 260 5EV Leopoldo E. Flguero - Colon 360 2CX Frederick W. Gorton Habana 320 6KW Frank H. Jon.. Tuinuou 340 2EV Westinghouse Elec. Co. Habana 220 6KJ Frank H. Hones Tuinueu 275 2TW Roberto E. Ramiro. Habana 230 6CX Antonio T. Figueroa C1.fiego. 170 2HC Heraldo de Cuba Habana 275 6DW Eduardo Terry Cienñego 225 2LC Lui. C.. Habana 250 6BY Jose Canduxe Cienfiegoe 300 2K13 E. Bashes de Fuent. Habana 350 6AZ Valentin Ullivari CI.neego. 200 2MN Fausto Simon Habana 270 SHY Alberto Revelo Btgo. de Cube 250 2MG Manuel G. Sale. Habana 280 8FU Andrea Vinnet Sego. de Cube 2JD Retal Pat. Falcon Hahm. 160 813W Pedro C. Andue Stgo. de Cube 225 European Broadcasting Stations British Stations 2L0 London 365 5140 Newcastle SIT C(rminsh.m 5 S 420 5WA Grdlfl 350 6SL Abard «n 492 IBM 385 65L Sheffield (ruby station) 303 2ZY Iwoheat.rManchester 375 French Stations YN Lyon. 740 8AJ Parie Pari. (Eiffel Tower) 2,600 ESP Pari. I 490 End your Radio Troubles for 30e in Stamps We have laid aside a limited number of back issues of RADIO AGE for your use. Below are listed hookups to be found in these volumes. Select the ones you want and enclose 30c in stamps for each desired. The supply is limited, so enrich your store of radio knowledge by laying in an ample stock of copies NO \\'! January, 1924 August. 1924 -A Tuned Plata Regenerator. - Tuning Out Interference-Werve Trepe-Elimmatorr -Breaking Into Radio Without Diagram. -Making e Station- Finder. 4- -Filter. -The English Element Tube. February. 1925 -A Junior Super-Heterodyne. -Filtered Heterodyne Audio Stages. -A Sure Shot Super -Het. -Push-Pull Amplifier.r car. -An Audio Amplifier Without an "A" Battery. -A Three Circuit Regenerator. -Rosenbloom Circuit. -Data Sheets. -A Real. Low Lo. Set. September, 1924 -Blueprints of a 3-tube Reflex Sf Merck, 1924 -How Careful Moatins Will Improve Reception. -An Faillit-Tube Super-H.terodyo. March, 1925 ?)! -One Tuning Control for Hair's Breadth Selectivity. Permanent Super -A ample. low lose tuner. Pages Real Blueprints New Baby -A -Het. -A Tuned Radio Frequency Amplifier. -Four of of Heterodyne -A 5-Tube R. F. Receiver. -Sirop Reflet Set. and an Aperiodic Variometer Set. -How to Wind Low Lo. Coil.. -Data Sheets. -A Short Wave Receiver April, 1924 October, 1924 -Blue Print* of 'Iwo -Tube Ultra Audio. and Re- -An Efficient Super- Heterodyne (fully illuetreted). -An Leal, Made Super -Het. generative Reflex. Tep -Dollar Receiver. -A -Two Radio and Two Audio for Clear Tone. April, 1925 -Anti -Body Capacity Hookups. -A Simple Regeoerative Set. -Rodening the Three-Circuit Tuner. -The Ultradyne for Real DX. -A 3 -Tube Portable Ses Voltage from the C. -Index and Scot two i.ullments of Radio Age Data Sheets. -Real Blueprints of 3 -Tube Neutrodyo and Midget -"B" A. Socket Reflex Set. -An Amplifier for the 3- Circuit Tuner Mer, 1924 -Blueprints of Five -Tube Radio Frequency Receiver -Construction of a Simple Portable Set. November. 1924 -Blueprints of Single Tube Loop Set and May. 1925 -Radio Panels. Capacity -A. "Quiet" Regenerator. -Third Installment of Radio Age Data Sheet.. Feedback Receiver. 3-Tube Low -A Power Supply Receiver. -A Lo. Regenerator. -How to Make Tube -Teeter. Jun., 1924 -Mastering the 3- Circuit Tuner. Super-HterodYne. -A Unique Super-Het and an Improved Reinan.. -Important Constructing December. 1924 -A Six Tube Portable Receiver Illustrated with Blue- -A Universalaln Amplifier. -Blueprints of New 8 -Tub Super- Heterodyne. print. -A Sure Fire Reflex Bat. -How to Make a Receiver that Minimiser Static. -Adding Radio and Audio to Baby Heterodyne. June. 1925 Trans-Atlantic -Reducing Static Disturbances - Nadio Age Data Sheets. -H Mak Hors Made Battery Charger and Loud Speaker at Small Cut. -A Seven-Tube Super -Heterodyne July. 1924 -The Double Grid Tube in Ordinary Sets -A Portable Tuned Impedance Reflex. January, 1925 -Browning-Drake Receiver -Operating Detector Tube by Grid Bi... -A Reflexed Neutrodvoe -Overcoming Oscillations in the Roberts Receiver -A Three -Tub Wiee,d Circuit. -A Six Tube Super -Het. -An Ideal Set in Practical Form -Data Sines.. -An Efficient Portable Set. -Soldering Secrets RADIO AGE, INC., 500 N. DEARBORN ST., CHICAGO RADIO . \GE (or Auguz,t, 1925 The Magazine of the !lour I11.: CLASSIFIED ADVERTISEMENTS If you have anything to buy or sell, don't overlook the value of RADIO AGE'S classified advertisements. Many such messages have paved the way to independent incomes. The classified advertising rates are but ten cents per word for a single insertion. Liberal discounts are allowed on three, six and twelve -time insertions, of five, fifteen and thirty per cent respectively. Unless placed through an accredited advertising agency, cash should accompany all orders. Name and address must be included at foregoing rates and no advertisement of less than ten words will be accepted. All classified ads for the September issue must be sent in by August 1.

AGENTS WANTED INVENTIONS RADIO CIRCUITS FORDS. 60 miles on one gallon of Gas. It has been NEW IDEAS WANTED -Well known Radio Manufac- SPECIAL FOR JULY proven such mileage can be made. AIRLOCK guar- turer whose products are nationally advertised and .old The Reinert. Radio Booklet, by Frank D. Pearne, eeeeee mileage: also radiator everywhere want. to sell. Will fully antees to in gas prevents new Radio device pay illustrated. and RADIO AGE, for $2.50. Price of Book- boiling in summer or freezingfro ing in winter. Cools. Fuels, outright or royalty for idea or invention which is really let alone i. 50c. Send check, currency or money order Decarbeni the Ford motor. Splendid territory new d leable. Address: Mr. R. F. Devine, Room to RADIO AGE. 500 N. Dearborn Street, Chicago. open. AIRLOCK PRODUCTS, Box 703G, Willow S , 1101 116 West 32nd St., New York, N. Y. Long Beach, Calif. RADIO DEALERS RADIO-Join r sales organization and make big MAGAZINES money. We want man in every countyo to .11ll well DEALERS -Write for our illu d catalog of reliable advertised t. and part made by the leading manu- DREAMS. A magazine for all who dream. If you Radio Merchandise. Ro..iter- Manning Corporation, facturer.. cWidener of Kansas City make. $150.00 d i the subjects of science. sex. psychology, Dept. D. 1830 Wilson Ave., Chicago, 111. weekly. You can do as well or better. Write today health. love and romance, you cannot afford to be with- for catalog, and discounts. Name your county. Wave - fout this magazine. Three dollars will bring this most land Radio Company. Div. 52, 1027 No. State St., Chi- ascinatine monthly publication to your home for RADIO SUPPLIES cago. Ill. one year. M. B. Smith Publishing Co., 508 N. Dearborn St., Chicago. III. Ten per cent discount on all standard radio parte frocondensers to transformers to tube. etc. Send MANUFACTURER'S AGENT calling on Radio -Elec- our latest price lier, special vicinity, has opening 3 for with bargain. on State- trical Jobbers, Chicago and for MANUFACTURING FACILITIES eliminator., portable loud speaker.. Redlotrona, Ger- additional lines carrying volume business. cater man silver to large Edelstein, 1804 McCormick Bid., win, etc. RADIOGRAPH LABORATORIES. jobber.. AN OLD AND WELL ESTABLISHED MANUFACTUR- 1234 Rosemont Ave., Dept. 4, Chicago, Ill. Chicago. ING COMPANY IN THE MIDDLE WEST WITH LARGE WELL EQUIPPED PLANTS AND UNUSUAL FINAN- AGENTSWRITE FOR FREE SAMPLES. Sell Madison CIAL RESOURCES. DESI RING TO ENTER THE RADIO STAMPS AND COINS Shirts for large manufacturer direct to FIELD WILL CONSIDER THE MANUFACTURE AND ..Better-Made" SALE OF RADIO SETS OR DEVICES OF OUTSTAND- wearer. No capital or experience Many 158 Genuine Foreign Stamp.. Mezico War Laues, weekly MADISON MFGRS., 501 ING AND UNUSUAL MERIT ON A ROYALTY BASIS. bonus. rd. ADDRESS BOX IA. RADIO AGE. V la, Salvador and India Service. Guatemala, earnBroadway, $lee a nd China, etc., only Sc. Finest approval sheets, 50 to 60 per cent. Agent Wanted. Big 72 -p. Liste Fru. We Buy Stamps. Established 20 Yens. Hussman 90c an h te advertise and distribute sample. to con. PATENTS Stamp Co., Dept. 152, St. Louis, Mo. Writer quick for territory and particular. American Product. Co.. 2130 American Building, Cin- FOR SALE: U. S. and Canadian Patent on an Attach. STAMPS, 50 varieties, Africa Brasil, Peru, Cuba, cinnati. Ohio. ment for Phonographs; is the most beautiful inven- Mexico. etc., 10c 50 different U. S., 25c1 1,000 mixed, tion of the age. Address Chas. F. Smith, Huff, N. Dak. 40c; 1,000 hinges, 10c List free. C. Stegman. 5950 Man wanted for this territory to sell wonderful Cote Brilliance, St. Louis, Missouri. value women's,, Children's shoes direct, saving Experience ecce vary. Sa pl . supplied. Big weekly permanent PERSONAL VOCATIONS Write today Tanners Mfg. Co.. 1334C. St., Boston, Mu. LONELY HEARTS: Exchange letter: make interesting Make Big Money. Safe and Lock Expert. Wayna new friend. In our jolly club. Eva Moore, Bog 908, Strong, 3800 Lan Franco St., Lo. Angele.. Calif. Jacksonville, Florida. Enclose .tamp. "B" BATTERIES Look! You Radio Bugs( Join Radio Correspondence WANTED Club. Entirely new. Broaden your acquaintance, 100 VOLT EDISON TYPE "B" BATTERY. knocked ideas. Membership open to LADY BUGS WANTED -To complete my set RADIO AGE need down. Parte and plans-complete. $12.50. Lane Mfg. aexchangelso. Dime stamp brings pamphlet and Radio Novelty August, September, October, November, 1923, eeeee 2937 W. Lake, Chicago. Cards. Radio Rose, Box 662, Cleveland, Ohio. bound or unbound. Advise price. Lloyd C. Henning, Hellbrook. Arisona. BATTERIES FOR SALE -Fou 24 -volt "Main" Sto "B" Batterie., never used, shipped and ready to wire PRINTING WIRELESS for $38.00. First order gets the batterie.. Address Box B. Radio Age. $00 N. Dearborn St.. Chicago. Ill. WE print Stationery, Booklets, Catalogs, Circular.. WANT TO MEMORIZE THE WIRELESS CODE? The Samples. Commercial P , Batavia, Ohio. Coryden Snyder Code Method. Patented, i quickest. Send 50e co stamps or M. O. to C. G. Snyder. 1423 Elmdale Ave., Chicago. III. BUSINESS OPPORTUNITY RADIO TELEGRAPHY-Morse and Wireless-taught at home in half usual time and at trilling cost. Omnigreph MR. MANUFACTURER: Would you be interested in A PRACTICAL TUBE RECEIVING SET FOR $10, Automatic Transmitter will send, on Sounder or Bur - a national advertising campaign to reach more than Postpaid, less phones and tube. Complete with ages. any speed, just as expert two million prospective buyers of quality radio products tube and 6 $18.00. J. B. RATHBUN, Aeunlimitedrator would. Adopted U. S. Govt. and used by -each week? Do you want te establish agencies in 1'hone.,067 Winona Sc., Chicago, Ill. leading Universities, Colleges. Technical and Telegraph new territory and create national interest in your ScbooI throughout U. S. Catalog free. Omnigraph very conservative cost? It cart done. Standard oderle.. radio Jack.. Binding poet e h- Mfg. Co., 13 F Hudson St.. New York. Let us explain our system without obligation to you. nt. Double circuit. One dollar bill. Postpaid. Drop a card to Radiograph Labo le., 1234 Rosemont Clinton Seward. Jr.. New Paltx, New York, N. Y. Ave., Chicago, Ill., Box 6. WRITERS Three Cosmopolitan Phu.iformer., each $5.50, book of instruction included. F. A. Mall, Triopli. Iowa. NEW WRITERS WANTED -Articles. stories, poem., etc. $13,500 ju.t paid to unknown writer. CRYSTALS Entirely new field. (No. bunk.) NOT A CORRE- 15 to 25 per cent discount on nationally advertised .et SPONDENCE COURSE. Moving picture indu.try and and parts. Every item guaranteed. Tell u your n publisher. crying for new original material. YOU TESTED GALENA CRYSTALS, 50e pound bulk. Bu.- IMPERIAL RADIO COMPANY. Delaware. Ohio. CAN DO IT. We buy manuscript for book. and mag- kett, Geologist, Joplin, Mo. Send self addresaed envelops for lie of 100 RADIO Our prices uve you money. List. free subjects. CALIFORNIA STUDIOS. P. O. Box 697, Lo. The RadioRad S. Ape, Box 645, East Liverpool, Ohio. Angeles. Calif. HELP WANTED AT LAST The Rade. Static Eliminator. Eliminate WRITERSCash in on your knowledge of radio by 50 to 90 ^, Static. Many satisfied users Write fo writing for Radio Magazine. and Newspaper Supple- particulars. Radio Specialties Company, Sioux Falls ments. Write uls Your radio a Aerie your new RADIO SALESMEN and SET BUILDERS -We need South Dakota. hook -up, your knowledge of broadcasting nation. and you and you need u If you a reliable and well Experienced authors will correct and improve known in community,s we will appoint you our your you. pt.make them typically profe..Ional furnish you with standard Advisory Senice your prices will enable work. FREE Criticism and until aderticed sets and that manumript is sold! ALL Magazines and Papera de- to sell at a handsome profit at once for cata- NOTICE TO READERS! m ding fiction and article. dealing with radio. Here log and sales plan. Waveland Radio Co.. Div. 53, 1027 YOUR OPPORTUNITY to fit! Send for FREE N. Stata St.. Chicago, Ill. Up to and including August 15, 1925, booklet. "How You Can Sell Your Manuscript." number of AGE Willis Arnold and Assoc:atm. 210 Ean Ohlo St. the August RADIO Chicago, Ill. MEN wanting forest ranger, ilway clerk and other will sell for the customary price of 25c position., write free of government for particular. Make big money writing Movie Plays. Circular. free. exam. okane, Dept. B -33. D , Colo. per copy, but after that date the price Krug. Ashton, Illinois. will be 50c per copy. If you wish for W. C. Classified ad. copy for the Sep- additional copies, or know of friends who might want this August issue, Have you ordered your tember RADIO AGE must be sent BUY NOW before the price goes up! in by August 1, 1925. September Radio Age? J Tested and Approved by RADIO AGE 104 RADIO AGE for August, 1925 The Magazine of the Hour

X60 -page DEVICES Reference Radio Age Institute displaying this seal have been tested Book Manufacturers' Testing Service and approved by MEMBERS of the staff of RADIO AGE will be pleased to test devices the RADIO AGE and materials for radio manufacturers with the object of determining their efficiency and worth. All apparatus which meets with INSTITUTE. the approval of various tests imposed by members of the technical staff of RADIO AGE will be awarded our endorsement, and the In- Apparatus illus- stitute seal will be furnished free of charge. Materials for testing trated and de- should be sent to scribed below has successfully passed RADIO AGE INSTITUTE our tests for Aug- 504 N. Dearborn Street, Chicago, Ill. ust, 1925. Maili List. Test No. Test No. 82. 79 consists SILVER "TWO - Catalog of a 'grid con- TENS" and denser made 'TWO -ELEV- No.55 i n circular ENS." Long wave POLK'S REFERENCE BOOK form with transformers. New FOR DIRECT MAIL ADVERTISERS conven- style Bakelite Shows how to increase your business by tional lugs Cases, replacing the use of Direct Mall Advertising, 60 pages for making connections. A cut-away the old type alu- full of vital business facts and figures. \Vho, section where and bow many prospects you have. shows the plates made of thin minum case, and Over 8,000 lines of business covered. brass Ieaves with ample dielectric, the far more efficient. Supplied in sets of Write for your copy. FREE whole mounted securely in a metal 2 or 3 21.0's (iron core interstage and R. L. POLK & CO., Detroit, Mich. housing. The capacity is stamped on one 211, (filter for input or out -put) ass POLK DIRECTORY BUILDING the back of the housing. Submitted with identical peaks and separate curves. Branches In principal cities of U. S. by the A. E. Hill Manufacturing Co., The feature of these transformers lies in the fact of Atlanta, Ga. Tested and approved that the makers plot the curve in their own labora- by the RADIO AGE tory and record them directly on a tag attached to Institute. each transformer before it Is placed on sale. Tests to determine the accuracy of these charted and matched transformers were conducted in this magazine's laboratory and in every instance the tag attached to each transformer was found to have the correct curve. Manufactured and submitted by Silver-Marshall, Inc., 105 S. Wabash Ave., Chicago. Satisfactorily passed the tests and requirements of the RADIO AGE Institute. Test No.83 submitted RADIO by the Storage "B" Battery Electrad, No.80. Inc., 428 w Lasts Indefinitely -Pays for Itself Test ilfEconomy and performance unheard of before. Recharged A compen- Broad- at a negligible cost. Approved and listed as Standard by Radio Poo sated multiple way, New Set. Inst. Standards, 14diolNewsaLab, Lef . loe, adogee . portent with an incur. variable condenser York gainst add and leakage. °hear, glee. rruugged ploma. Order yours today! which the manu- Sample car° nmb°` consists SEND NO MONEY JaeO facturers claim to be the only practical order la received. Extra Otter: batteries in series1196 volts $12 96. single dial control on the market. of a grid condenser type G -S equipped :¢4 5 par cent dbeomt for unit Pueboath order IDteiÌ ya,m neide bñó `Ies. Submitted by the United Scientific with punched connecting lugs by means WORLD BATTERY COMPANY Laboratories, Inc.. 80 Fourth Avenue, of which the condenser may be mounted 1219 So. Wabash Ave., Dept. 81. Chicago, Ill. make,. of' the Famous World Radio "A" Stomas Battery New York City. It can be built into directly to the socket. There are two Prieee: a-oolt, 100 wipned Amy. no.a0. is orongs for the use of a cartridge resistance of a grid via SooliidBubb*, daao. any tuned radio frequency circuit; leak. The capacity of each condenser is stamped í?!ç $ compact and space saving and reduces on the prongs. Tested and approved by the RADIO FOR panel requirements. This new multiple AGE Institute. World RADIO is a straight -line, low -loss condenser STORAGE BATTERIES making the sharpest tuning, quick and Qipi( gvrAfW61jw5 sKtufltOslCFw7Pf-KKQI easy. The manufacturers claim that dozens of stations can be brought in instantly. Capacity .00035 mfd. per unit. Tested and approved by RADIO AGE Institute. Test No. 81. Submitted by the Anylite Electric Co., at Ft. Test No. 84. Sample submitted by Wayne, Ind. The the Walbert Mfg. Co., 925 Wrightwood Dealers -if you want the best pro- sample consists ducts, the fastest shipments and Ave , Chicago, Ill. This socket of the most liberal discounts, write on of an audio fre- bakelite with a safety top rim has both your Iecterhead for our catalog trans- L1003. quency side and bottom contacts for the prongs former, well built of a vacuum tube. With both types of friction con- and shielded, tact there should be no difficulty with loose con- designed for use nections. Tested and approved by RADIO AGE in any audio am- Institute. plifier where Test No. 85. clearness of Submitted by speech and volume is desired. Tested Dongan Elec- and approved by RADIO AGE Institute. tric Manufac- turing Co., //í Radio 2983 Franklin MARSHALL eeceiversey St., Detroit, RADIO CONSOLE Embodying a marvelous New Mich. T h i s Non -Oscillating Principle unit is designed for delivery from IIO R AULF MFG. C0.562 VEDDER ST. Sold Direct on Free Trial and Easy Terms volts, a.c. of the necessary voltage for Write for catalog and Special Offer the new McCullough a. c. tubes. Equipped CHICAGO. WRITE FOR CIRCULAR with lever switch for various volta Marshall Radio Products, Inc. taps. Tested and approved by RADIO Dept.B-589 MaraballBlvd.&19thSt.Cbieago AGE Institute. * Tested and Approved by RADIO AGE IF Mr. Manufacturer e Would you write 100 letters to 100 people to reach just two men? Then, before you invest your advertising dollars- THINK!

An analysis shows that publications of general circulation, newspapers and magazines, devote less than 2% of their reading columns to Radio -proving that in the opinion of This Association their ov.n Editors less than 2% of their readers are inter- is comprised of ested in Radio. In fact, many general publications carry no the leading Ra- Radio editorial matter. Therefore 93% of your investment dio Magazines. is lost!

On the contrary, the Radio magazine offers 100% Radio editorial -- attracts 100% potential buyers. Spend your advertising appropriation in Radio Magazines. Be sure of the greatest possible return on your advertising dollar, Radio Magazine Publishers' Association, Inc. RADIO AGE is a member of the Radio Magazine Publishers Association, Inc. to

-LONG DISTANCE4. TRADE MARK REG. Arctic Explorers Stake Their Lives on Zenith Radio

It is one thing to select a radio set for pleasure only -it is quite another to select a set which may be called upon most Costs More unexpectedly to save your life. But Does More Alone in the Arctic -cut off from the nearest rescue post by hundreds of miles of ice and open water -men cannot run to the nearest radio shop for repairs. If transportation fails, and radio does not work, they are in the gravest peril. This summer -across the million square miles of unexplored territory stretching between Alaska and the North Pole - MacMillan and his party of explorers will fly in three great navy planes. Each of these cruising airplanes is equipped with Zenith radio, as are the Bowdoin and the Peary, which will locate at Etah as their base. Between ships and airplanes messages will be sent and received. When Arctic explorers of MacMillan's calibre stake their lives- repeatedly -on Zenith performance, one reason only can explain their choice -Zenith has proved to be the best obtainable, at any price. Call this evening at your nearest Zenith dealer and let him Super. prove it to you by a demonstration. Zenith IX ZENITH RADIO CORPORATION 310 South Michigan Avenue, Chicago

HE complete Zenith line ranges SUPERZENITH V1I -Six tubes -2 stages tuned reproduce both high and low pitch tones otherwise in price from $100 to $475. frequency amplification- detector and 3 stages audio impossible with single -unit speakers. frequency amplification. Installed in a Price (exclusive of tubes and batteries) With either Zenith or beautifully $475 3R Zen;.h finished cabinet of solid mahogany -447i inches long, All Prices F. C. B. Factory 4R, satisfactory reception over dis- 16.'á inches wide, 10. inches high. Compartments at tances of 2,000 to 3,000 miles is either end for dry batteries. Price readily accomplished, using any (exclusive of tubes and batteries) $240 ordinary loud speaker. Models Zenith Radio Corporation 3R and 4R licensed under Arm- SUPER -ZENITH VIII -Same as VII except-con- Dept. C -8 strong U. S. Patent No. 1.113,149. sole type. Price (exclusive of tubes and + 310 S. Michigan Avenue, Chicago, Illinois They are NON -RADIATING. batteries) $260 Gentlemen: - Please send me illustrated literature about Zenith 4R $100 SUPER-ZENITH IX- Console model with addi- Zenith Radio. Zenith 3R - $175 tional compartments containing built-in Zenith loud The new Super- Zenith is asix -tube speaker and generous storage battery space. Price (exclusive of tubes and batter- Name set with a new, unique, and really ies) different patented circuit, con- $355 trolled exclusively by the Zenith Address SUPER-ZENITH X- Contains built -in, patented, Radio Corporation. It is NOT Super-Zenith Duo -Loud Speaker,' (harmonically regenerative. synchronized twin speakers and horns), designed to

* Tested and Approved by RADIO AGE