www.americanradiohistory.com 7

41.1 /he ;Ái»ut- big radio

AWAY with "B" batteries on those many sets -tube sets! Have you tried to work a "B" eliminator on a six, seven, eight tube set? Here's one that was designed specially to take care of the heavy current drain of these sets -the RCA Duo Rectron.

It delivers power aplenty for big or little sets. It delivers it smoothly, steadily, silently. And economically! It supplies up to 135 volts for the power tubes -taps for less if you want it -and a voltage regulator to keep the current exactly right for your radio set.

And also-it's a proved product

of RCA !

For Christmas, what better idea than an RCA Duo -Rectron -to do away with "B" batteries forever, and give improved reception. It means top- notch performance all the time, with no care at all.

Buy with confidence where you see this sigh ftCA "B" BATTERY ELIMINATOR (DUO RECTRON)

1111.11.,N A M E R I C A N E W Y O R I C A C O SAN FRANCIS glir

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 751

Eveready's exclusive Layerbilt construction makes this the most economical of "B" batteries

IMPROVEMENT 011 top of im- battery. This exclusive Ever- This HEAVY-DUTY EVER - provement has been the history eady Battery development EADY LAYERBILT BATTERY of Eveready Radio Batteries. packs more active chemicals gives twice the service of the Here, in the radically differ- in a given space and enables smaller Light -Duty batteries ent Eveready Layerbilt, is them to produce more current and greatly reduces your "B" the "B" battery which tops and give longer life. battery operating cost. them all. The ability of this Use Eveready Layerbilts battery to give you unrivaled on any set, and get not only is to Tuesday night means Eveready Hour -9 P. M., extra service, but also service and economy due (:astern Standard Time, through the following this - its unique internal design. In- stations: the greatest "B" power op- WWF -Vnr York Wrest- Cteretand the usual assembly of w,an- Prorideneo WWI -Detroit erating economy -the u' stead of Waal -Boa /on Won- Chieogo round .cells, it is built of flat ara.c- Woreedn woc-Davenport in "B" power depend" Wn- PAaadelphla wceo ilinneavolls w .a- B.palo Sgt. Paid layers of current -producing wrap.-PIttabargk Heo -Al. Loar. D. C. (direct - materials pressed firmly to- Weal-Cincinnati WBC -Wash lndten purest fora gether. This construction pure tit" makes use of the spaces now Everea wasted between the round -type Manufa cells and avoids the usual sol- Radio Batteries NATION connections. Ever- -they last longer New York dered wire Canadian Matto eady Layerbilt is every inch a Toro,

www.americanradiohistory.com Popular Radio EDITED by KENDALL BANNING

FOUNDED 1911 %OD U9:4v VOLUME X December, 1926 NUMBER 8 CONTENTS (Cover design by Frank B. Masters) The Effect of Temperature If You Want to Read the Code - on Signal Strength Practical advice, by a former Radio Inspector, By for learning how to receive and transmit E. E. Free, Ph.D PAGE 763 messages in code Wanted -A Radio Humorist By Howard S. Pyle PAGE 778 By Homer Croy PAGE 766 How to Build the Uncle Sam's New Short Wave Net LC- Intermediate Power -pack The second of a series of article, to follow the "How By Captain J. L. Autrey PAGE 769 to Build the LC-27 Receiver," published in October How Circuit Resistance By Laurence M. Cockaday PAGE 780 Affects Selectivity Practical pointers about coil resistances in the "From Fire and Flood -" radio-frequency circuit, for the experimenter who What five radio amateurs of Oklahoma did to win wants the greatest selectivity with the best tone the POPULAR RADIO Medal for Conspicuous Service quality that can be obtained By Lloyd Jacquet PAGE 783 By Glenn II. Browning .... PAGE 770 Simple "How to Build" Articles The Salt on the Tail of the for Beginners Broadcast Frequency NUMBER 17: How to Build an "A" and "B" How the tiny piezo crystal serves the interests of Power -pack for Direct Current the broadcaster by checking station wave- By Morris M. Silver. PAGE 785 lengths and preventing interference By Morris S. Strock PAGE 773 Inside Information on New Radio Receivers Popular Radio Circuits FOURTH INSTALLMENT INSTALLMENT No. 5: The Model 8C Kolster Receiver The Grimes "Inverse Duplex" Receiver The Ferguson Model 10 Receiver The "Infradyne" Receiver The Clearcone Model 110 Receiver The Technical Staff PAGE 776 By S. Gordon Taylor.... . PAGE 786 DEPARTMENTS The Yes and No Man 798 The Beginner in Radio. Armstrong Perry .. 818 What Readers Ask. David Lay 840 In the World's Laboratories. .E. E. Free 848 Broadcast Listener Raymond Francis Yates 858 Broadcasts Charles L. Reese, Jr 862

was X DECEMBER. 1926 NuMBER 8 hed monthly by Popular Radio, Inc., 627 West 43rd St., New York, N. Y., telephone number. Chickering 1906; Douglas H. Cooke. President asurer; Kendall Banning. Vice-President; Laurence M. Cockaday, Secretary; Joseph T. Cooney, Asst. Treasurer. Price 25 cents a copy; tion $3.00 a year in the U. S., Canada and all countries within the domestic postal zone; elsewhere $3.50 a year, payable in advance. The News Company. Ltd., No. 5 Bream's Bldg., London, E. C. 4, sole distributors in England. Entered as second class matter April 7, 1922, t Office at New York, N. Y., under the act of March 3, 1879. Copyright, 1926, and title registered as a trade -mark by Popular Radio, Inc. n Great Britain by Popular Radio. Inc., 6 Henrietta St., Covent Garden,. W. C., London, England. For advertising rates address E. R. Crowe & Company, Inc., 25 Vanderbilt Ave., N. Y. or 225 North Michigan Ave., Chicago. Printed in U. S. A. NCE M. COCKADAY. Technical Editor E. E. FREE. Ph.D., Contributing Editor S L. REESE, Jr., Managing Editor JOHN V. L. HOGAN, Contributing Editor

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 753 J'1'heted leader > rie FG1(d ORMER

If you love music, and want your radio set to reproduce tones fault- lessly, there is one audio transformer you can absolutely depend on -the famous Rauland- Lyric. Voices and instruments alike are amplified wich amazing realness by the Rauland-Lyric; with faithful amplification of those "overtones" essential to full, natural reproduction. The amplification curve of the Rauland- Lyric illustrates its outstanding superiority in tone purity. The Rauland -Lyric is the undisputed leader in its field. It is invariably chosen by set builders who want the utmost in perfect tone quality. A new high mark in Panland=rforrc3io three -stage audio amplifiers Your receiver's tone quality depends in large measure on correct audio amplification. The famous Rauland -Lyric Transformer may now be combined with two Rauland -Trios (im- pedance units) to form the Rauland- Lyric -Trio -the highest known perfection in three -stage audio amplification. Rauland -Trio is a com- pact, well -made unit - containing in one shell - inductance, resistance, and capacity in correctly balanced relation.

Write for "Modern Audio Amplification ", a free book, describing this fine unit. New 1927 Radio Key Book You'll enjoy reading it -48 pages of interesting, up- to- the -minute facts about radio, simply told. Also full construction details of all leading types of circuits. Send io cents (coin or stamps) to cover postage and mailing cost.

ALL -AMERICAN RADIO CORPORATION 4207 Belmont Avenue, Chicago, Illinois

OWNING AND OPERATING STATION W E N R + 2 66 METERS

www.americanradiohistory.com A PAGE WITH THE EDITOR RADIO experimenters and home set - light globe's offspring, the radio vac- A PRELIMINARY study of the answers builders need no introduction to Ken - uum tube -recently burst forth into a is now being made. When the best of neth Harkness, whose place in the broad critique of radio, he was obviously the letters are selected, copies will be Radio Hall of Fame was assured when inspired in part by a desire to exploit submitted to the judges for final de- he developed the Harkness Reflex Re- his new type of phonograph record that cision. The prize -winning letter will be ceiver three years ago and the Counter- was about to be placed on the market. published, as soon as the winner is flex Receiver last year -both sub- chosen, in POPULAR RADIO -probably stantial contributions to the radio art. AND when the Grand Old Man of in the February s number. Menlo Park claims that the public in- s * IT Is with particular gratification terest in radio is waning, he merely THE judges of the contest are Prof. therefore that POPULAR RADIO now ad- utters an opinion based on a hope, and Alfred N. Goldsmith, Secretary of the vises its readers that another-and the speaks without knowledge of the facts. Institute of Radio Engineers; Col. W. E. best- circuit developed by 11lr. Hark- s s Harkness, Vice- president of the Broad- ness will be first and exclusively an- BELOW, for example, are a few facts casting Company of America; Frank nounced, with complete constructural and figures concerning the increase of H. %fcDonald, President of the Broad- details, in the coming issue of this mag- public interest in radio; they carry the cast Listeners Association; Frank W. azine -for January, 1927. authority of an official report from the Elliott, President of the National As- * * U. S. Department of Commerce, dated sociation of Broadcasters; and the THE new Harkness Receiver (which October 16, 1926: -only a few days editors of POPULAR RADIO. L9 designated as the KH-27) is a 6-tube following Mr. Edison's statements. two-dial set that employs dual tuning. THE winners of the contest may thus * * THE indications are that the growth be assured that their suggestions will be AN outstanding feature of the re- of interest in radio during the coming brought to the attention of the very ceiver is the new form of amplification winter, and the increase in sales of radio men who are in the best position to that it incorporates; it consists of double receivers and apparatus, will break all make practical use of the ideas sub- impedances that bring out both the high records. mitted. and low notes with remarkable clarity. s s s IT is unfortunate that these figures HOMER CROY, whose article "Wanted THE radio-frequency stages are neu- were not at Mr. Edison's disposal at the -A Radio Humorist" appears on page tralized so that the set cannot oscillate, time he made his observations. Facts 766 of this issue, is the novelist whose and figures are sometimes embarrassing book and film "West of the Water MR. HARKNESS, it may be observed details to reconcile with theories and Tower" made him famous practically in passing, has been working in radio for opinions formulated without them. overnight, and paved the way for the s twelve years, during which time he has success of his latest novel "They Had to seen war service as a radio operator in ON October 15th the prize contest See Paris." This is his fifth contribu- the British Navy, did extensive work for answers to the question "How can tion to POPULAR RADIO. on the Armstrong super-regenerative radio broadcast programs be im- s s circuit, wrote book the "Radio-fre- proved?" closed -according to schedule. WITH the coming issue of POPULAR s s quency Amplification" and for two RADIO -for January-the department served years as the technical mainstay ALL answers that bear a post mark "What's New In Radio" will be con- of the magazine "Radio in the Home." dated on or before October 15th are siderably expanded. POPULAR RADIO welcomes him to its eligible for the cash prizes, as an- s s long and growing list of distinguished nounced in the September number of THIS expansion has been made nec- contributors. this magazine. essary not only by the rapid develop- * s s ment of apparatus in the field of radio WHEN Thomas A. Edison -who in- THE wide interest in this live topic, but also by the corresponding increase vented the incandescent light globe as evidenced by the large number of of interest on the part of experimenters fifty years ago and who has expressed entries, has evoked some novel and and broadcast listeners alike in irritation new at radio -possibly because Ile original ideas -which was, of course, types of receivers, loudspeakers, tubes, cannot also claim the parentage of the exactly the purpose of this prize offer. condensers, transformers, coils, an- tennas, rheostats, power-packs and other Per Cent 192.; 1923 Increase apparatus which constitute valuable contributions to the radio art and are TOTAL VALUE $170,390,572 854,000,470 215.5 increasing the efficiency of the receiving LOUD SPEAKERS: Number 2,606,866 623,146 :318.3 set. Value 19,162,591 5,608,330 241.7 s s RECEIVING BETS: READERS are invited to notify the Tube type_ Number 2,130,622 190,374 1045.4 Editor of the "What's New in Radio" Value 88,800,538 13,326,110 566.4 department of any new inventions that TRANSFORMERS: are of particular interest; apparatus of Number 3,413,993 1,571,817 117.2 Value 7,457,805 3,929,581 89.8 outstanding merit, that is passed by RHEOSTATS: the POPULAR RADIO LABORATORY, Will Number 3,531,871 1,085,171 225.5 be duly recorded and, whenever pos- Value 2,084,188 953,396 118.1 sible, pictured for the information and LIGHTNING ARRESTERS: guidance of all. Number 2,971,379 1,758,723 69.0 Value 506,034 422,036 19.9 RADIO TUBES: Number 23,934,658 4,687,400 110.6 Value 20,437,283 9,824,172 108.0 MISCELLANEOUS PARTS: Value 27,978,007 12,999,623 115.2 Editor, POPULAR RADIO

www.americanradiohistory.com I \NORATORY Page 755 AU apparatus advertised in this magazine has been tested and approved by POPULAR RADIO

Aerials have gone out of style In the old days, when radio was new, the "fan" was known by crazy festoons of wire that decorated his housetop or yard. These were the old-fashioned aerials, and no one has forgotten all the grief they caused. Modern radio may use the hidden loop, or the short indoor aerial. But there is a better way. The Dubilier Ducon enables you to use the complete wiring system of your house without risk, and with better results than most out door aerials give. You simply screw a Dubilier Ducon into any lamp socket, and con- nect it with the antenna binding post of your set. You will find that it increases selectivity- especially in crowded neighborhoods, and will reduce "static" in the summertime.

Try a Dubilier Ducon on your set tonight. They are sold by all good dealers on five days' trial for $1.5o Jubilier CONDENSER AND RADIO CORPORATION

www.americanradiohistory.com SEEN BY THE CHRISTMAS SHOPPER Some of the new and interesting radio apparatus that has just been put upon the market -and that offer suggestions for holiday gifts. (Names and addresses of manufacturers of the apparatus mentioned will be furnished upon request by POPULAR RADIO SERVICE BUREAU) A De Luxe Combination $225. For about $35, you can buy a good loudspeaker but that bnngs the A Useful Power-tube Adapter Receiver and Phonograph extras to about E85, for $1.25 That Sells for $1,000 * THIS beautiful piece of inlaid furniture is a combination of the best there is in Standard Storage Battery radio with the best there is in the phono- Tubes from $2.00 Up graph art. These instruments list at $1,000. They use no batteries or antenna; all you do is plug them in the light socket and they're ready to use. All necessary tubes come with the outfits; no extras to buy. To change from radio to phono- graph, all you do is throw this switch. A gift you can be proud to give. HERE'S an interesting combination that's a safe bet for anybody with a good five or six-tube set that isn't specially A Good -looking Set for $260 wired for a power tube; they'll call you quite an expert for picking out this com- bination! Buy this power tube adapter, IF your radio friends are still using the making possible the use of a power tube tubes they bought with with an ordinary set. It gives much the set a year ago, clearer give them a new set of tubes. It's like signals, especially on loud nearby having the valves ground and new piston stations. The adapter is $1.25, the tube rings put in your automobiles it peps the $4.50, that's $5.75. You add the neces- set up wonderfully. Practically every sary extra batteries for the power tube storage battery set will work too, so they can hook the tube right up. with UX- needs 201-a type tubes throughout. They cost It two 43 volt "C" batteries, $1.30 $2.00 apiece. But most sets are equipped and one large 45 volt "B" battery, $3.75. to use a power tube in the last stage, So with $10.80, they have everything, which makes them capable of handling even batteries for six or eight months, to a run power much louder signal without distortion. A their tube. power tube costs about $4.50. So, with such sets, figure on one less UX-201 -a type tube and get one power tube for the A Particularly Easy -to- last stage. * * Operate Set for $231 THIS receiver is an interesting one be- A Fine New Detector Tube cause it uses alternating- current tubes. It's low in price for a receiver that elimi- for $5.00 nates all batteries. Laboratory tests on this receiver have shown up very well. HERE is the same receiver without the Just two dials to tune. Loudspeaker and phonograph in connection with it, sold in antenna are all you have to buy in addi- this table form for tion to the set. That's $231, plus $35 or $260. It suggests an for antique desk, doesn't it? No antenna is $40 those two items. required. It's selective enough for the most crowded conditions. Used with this $225 power loudspeaker, it gives as good reproduction and offers the same freedom from batteries as the $1,000 combination phonograph -radio just shown you. THERE'S another substitution you can A Receiver Without Batteries make that will tickle any fan who goes after distance; get him' a UX -200 -a type That Costs $400 detector THIS magnificent tube. It fits any set that uses a looking receiver UX-201 -a type sounds just as well as it looks. The parts detector tube. It's worth inside are spaced the $5 for the extra volume and long dis- far apart, reducing in- tance it brings in. teraction to a minimum. Three large This is the line -up on knobs serve as dials. storage battery tubes: first choice, three tuning The dial UX -201 -a type settings for any station are nearly the same tubes, one UX -200 -a type on all three dials. All detector tube and one UX-112 type or you have to do is UX-171 mark correct settings on a card and you type power tube, total cost $15.50; second choice, four UX-201 -a can get the station back again any time tubes it is on the air. This set gets its power and a power tube, $12.50; and direct from the current mains without third, five UX -201 -a type tubes, $10. storage or dry cells and it costs $400. Dry-Cell Tubes at $2.25 A Good Two-dial Standard to $2.50 Loudspeakers Cost from Receiver for $225 ABoUT dry-cell tube sets; here you $10 to $225 Tats console is made by a manufacturer require a different line. Corresponding to ABOUT loudspeakers, won there is no end of who has an enviable reputation with the UX-201 -a type storage-battery tube is choice. This $225 power this product; it's in its second the model plugs into year now, UX-199 type dry -cell tube, selling for any alternating- current lighting line and without radical change. Just two tuning $2.25; to the UX -112 type power tube, is delivers volume controls. nearly equalling that of The console with loop and built - the UX -120 type dry-cell, power tube, the original music, or it can be softened in loudspeaker is $365; you must add selling for $2.50. Don't go wrong on down to a whisper without about for charger, distortion. It $50 tubes and batteries tubes. Buy only standard makes that you is a wonderfully useful addition to a good although, of course, you can spend a little know about and only dry -cell tubes for set, now using a small, ordinary loud- more on these items and make the set dry-cell sets and storage battery tubes for speaker. It's a good addition much to maintain. to a good easier In the table storage battery sets. The wrong kind of a set, but it won't make a poor set into a model, without loudspeaker, the set costs tube rs useless. good one. 756

www.americanradiohistory.com RADIO LABORATORY Page 757 .417 apparatus advertised in this magazine has been tested and approved by POPULAR

Recommended for the LC SENIOR POWER PACK THE NEW PRECISION HIGH VOLTAGE FILTER CONDENSERS

FOR THE LC -27 RECEIVER PRECISION

in the tollcwing capacities particu- DUO -OCTAFORM COILS Made larly for use where high voltage condenser- are necessary: Used in Mr. newest contribution to radio. No. 46-4 mfds. DC working voltage 60O Cockaday's Price $9.00. Price each $3.50. *No. 26 -2 mfde. DC working voltage 800 Price $5.50. No. 44-4 mfde. DC working voltage 400 BUILD THE LC -27 FOR CHRISTMAS Price $5.50. No. 24 -2 mfde. DC working voltage 400 For the convenience of those consumers and dealers who wish to Price $3.00. buy Cockaday's LC -27 in complete kit form: we offer the follow- '?periled for the Senior Power Pack. ing parts exactly used in Mr. Cockaday's laboratory model. 1- Hammarlund mid-line dual condenser, 1-Mar-Co. illuminated control. scale 0 to THE PRECISION .000275 mfd 100 53.50 COIL mid -line single condenser, 2 -Co small controls for LC -27 1.60 R. F. CHOKE I Hamm -Mar 0 mind 4.65 1 -Carter battery switch .65 Precision Duo- Octaform coil set, one 1- Samson radlo-frequency choke colt No. can be used wherever this 1- 85 1.50 type of coil Is necessary. antenna coupler and two interstage couplers 10.60 3- Aerovex mica fixed condensers. .00025 Very compact, bring one 1.05 Inch In diameter and one 1- Amertran De Luxe Brat-stage trans- mfd former Durham resistor. 4 megohms .50 and one -half inc s long. De 1- Can be mounted on a sub- 1-Amertran 1 -Lynch grid leak mounting .35 Luxe second- .25 panel or a emeboard. stage trans- 1- Carter Gem Jack liracket for baseboard former 10.00 1- Carter resistance. 0- 10,000 ohms 2.00 mounting provided with posta 1,80 1 aA 4erchoke No. 12 -Eby binding rh coll. Has a very low 5.00 Benjamin CX sockets distributed rapacity, due 6- 3.75 of t-DubWer No. 1- Amperite to the slotted form 902 filter con- aluminum winding. list price 51.00. Mechanical Kit consisting of denser. 4 mfd. . 5.50 strip. decorated panel No. shields, binding post 1-DublBer and Tait Brackets 12.50 907 alter con- Complete $85.20 denser, .1 mfd. .60 180 VOLT B- SUPPLY Without Cabinet $85.20 With Corbett Cabinet $103.20 for use with 110 v. AC 50 -60C. with cabinet $10.00 extra A very powerful. strongly constructed Built complete t'X216B tune eliminator. (lives 180 volts : 80 mils. Particularly designed to supply current for the new UX171 tube. POWER PACK Lint price $47.50. THE INTERMEDIATE

Resistance. 2. 0011 ohms.... 52.00 Switch No. 444 $5.00 1 Centralao 1 Yaxley Automatic Relay 7334 z 18' z H .85 Transformer, type K- 180 5.25 I Ha.dscood baseboard. 1 Filtrer A-C binding post panel, 354 x 4 S4s Choke Cotte. type IC ®$6.76 13.50 1 Bakelite Filtrer .35 3/32', drilled, ... .50 1 Na-atd Socket 1.00 .90 1 Set POPULAR RADIO blueprints.. 8 EDY binding posta wire. screws. etc .50 block, 14 mfd 11.00 Connecting 1 Acracon condenser cord with attached volts 1 8 ft. twisted silk lamp 1 n filter condenser, .1 mid. 400 Act 1.00 Plug 40 200. l F h L Tapped Resistance -type ç n $47.50 20.000 ohm. o THE LC SENIOR POWER PACK 17.50 Contrefit $ 6.00 I -Brach -52 18.00 1- Centraalab resissotacce, 5wwatts, 2,000 t- AmerTrao transformer, PF ohms 2.00 l- Benjamin UX- Socket binding post strlp, 3W z 15 2- AmerChokes, No. 854 12.00 1- Bakelite . x yf ' 7 -Eby binding Poets strip, 175{' z paper filter condenser. No. 26, 1 -Brass mounting 1- Precision 5.50 1/18' 2 mfde x z H .60 condenser. No. 24, 1- Hardwood baseboard 834' Ib' THE ORIGINAL I- Precision paper filter POPULAR RADIO Blueprints 1.00 2 mfde 3.00 1-Set COCKADAY COIL 1-Precision alter condenser, No. 44, The only coil ever specified by Laurence M. epaper 5.50 565.20 Cockaday, inventor of the famous Cockaday Four Circuit Tuner for use in his set. The fully guaranteed. best hard rubber tubing and double silk Exactly as used in the laboratory model. Every part covered copper wire Insures a coil of unusual quality, resulting in increased volume and HAVE greater selectiMty ksge EVERY DEALER SHOULD losses are extremely low.11tPrice. $5.50 INFORMATION a set of Precision Coil catalog sheets. They describe in detail Write for receivers for all of the Precision Coils used in POPULAR RADIO designed the past two years. Units are also given in \ complete list of the new Precision Line of Radio Power easily filed catalog form. PRECISION COIL CO., Inc. 209 Centre St. New York, N. Y. a

www.americanradiohistory.com A Popular HERE'S an automatic "A" Line of Sets battery con- A Good Buy Costing from trol device that saves no end of trouble for at $119 $29 to $50 the storage -battery set owner who has a battery charger. When you shut off the set, it connects the charger; when the battery is fully charged, it cuts off the charger automatically. It pays for itself by doubling the life of your storage bat- tery. The cost is $12.50.

An Excellent Receiver for HERE is a line of simple, neat -looking the Beginner low -priced sets. The four -tube model costs only $29; the five -tube is made in two models, $38 and $50. The higher priced one has only one control; the cheaper one has three. Yes, they're regenerative -but this isn't the kind your HERE'S a remarkable buy at $119. friend has warned you against' it won't Good looking console, loudspeaker built spoil your neighbor's reception because it in and space for concealing batteries, has a blocking tube ahead of the regenera- eliminator, charger, whatever you use. tive tube which keeps squeals from get - Three dials, but when you consider the ting out. Tubes, batteries, loudspeaker price, you're getting a whole lot for the and antenna are extra. money. Good looks, good selectivity and * you can't complain much about that sur- A prising volume and tone quality. The Unit that Makes a Good tubes and batteries are extras; count Set Better for $49.50 about $45 for them. s * THIS set is just right for the person who doesn't know anything about radio. Standard Parts that Cost l'here's just one knob to turn and the from $1.25 scale there tells you the wavelength in to $6.60 meters. Stations are listed by wave- HERE are a few hints about buying for lengths in the newspapers so all you do is experimenters, the kind to who builds sets pick out a program you want to hear and experiments from seven in the evening and set the dial to its wavelength. If the till one in the morning. Confine station's in yourself rango you get it. The set is to parts that fit in any circuit, or else $110. Yes, there are extras, -tubes, bat- you Il pick something teries, wrong. Here's a HERE'S something that makes any good loudspeaker, antenna -about $55 list of suggestions: set better; it's a combination to $60 in extras. It's a good set- selec- power amp- tive, excellent Illumirwtrd vernier dial lifier and "B" battery eliminator, combined tono quality, well worth Set of resistors: *3.50 in the money. Small one $49.50 unit. Plug it in the power selection, one each j, 3,6, 1, 2, 3 line and and 5 megohms get smooth loud volume and eli- Large 3.00 minate the "B" battery selection, three y(,, one each Sf, % from your set. and 1 megohm 3.75 * * Selection /fixed conleneers: A Magnetic Relay Switch Small selection, one .01, three two.00025. .001. A $12.50 Device that Doubles mfd. 1.25 for $6.00 Large selection, three each 1 mfd., .001 the Life of Your and ..000'25 mfd 6.75 Battery Tills device is a magnetic relay switch Sel of filament resistors: For storage battery and it eliminates a lot of bother if you use a tubes, five 1 -A and trickle charger and "B" one 12 type 6.60 battery subeti- For dry-cell tubes, four 199 and one t,uto. When you shut off the set, it cuts 120type 5.50 in the charger; when you turn on the set, To simplify it cuts in the "B" battery substitute. And the selection of gifts here is better yet, you can put it list that gives radio purchases in order all three things in of price. the cellar and control them at a distance. The footnotes are a guide to the That helps improve the class of radio enthusiast and the type of appearance of receiver to which the living room a whole lot and costs only the suggestion is suited. $6.00. - EDGAR H. FELIX

Hints for the Christmas Shopper Gifts that cost from 25 Cents to 81,000 for the radio fan: to Lea 8.50 $..00 to $7.00 Can of solder SC 850.00 to 8100.00 Bus bar Supersensitive detector ..... DX, SBR Complete SC High grade audio transformer SC moderately priced Binding posts SC Automatic receiver ALL ('all letter hook filament and battery DX substitute switch ALL, *100.00 to 8800.00 Single resistance mountings SC SBR, AC Efficient 87.50 to $10.00 5 -tube console receiver. ALL 8.50 to 81.001 8200.00 to Trickle charger AC, SBR 8500.00 Hydrometer...... Salt Power Double Renewal of "B" batteries ALL loudspeaker ALL, AC resistance mounting . . SC Renewal Complete console radio receiver Lock filament switch SC of tubes ALL ALL 810.00 lo 815.00 *500.00 to *1,000.00 81.00 to 1400 Long distance receiver Filament resistors Set of short -wave coils SC requiring SC Small cone speaker no batteries or antenna ALL Battery voltmeter.... ALL ALL Combination radio Pilot Full automatic "A" battery and phono- light battery switch SC control graph ALL Power tube adapter ALL ALL, SBR *5.00 to 815.00 to 885.00 AC -House 83.00 Three -stage must be wired for electric lights with Subscription to Popular Radio ALL resistance ampli- alternating- current supply. Illuminated fier ALL vernier dial 8C Medium sired ALL -Suited to needs Vacuum tube ALL Cone ALL of any radio enthusiast who Storage battery charger.. ALL, SBR has not the equivalent of the device men- 83.00 to *5.00 885.00 lo tioned. Extra large "B" 850.00 Battery ALL Combination amplifier and DX -For the Selection of resistance and ca- eliminator "B" long distance enthusiast. pacities ALL, AC SC Large cone speaker ALL SBR -For storage battery receivers only. Power tube ALL B" battery eliminator ALL SC -For the set constructor. 758

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY l'age 759

TYPE R -171 TYPE R -210 Contains a power supply transformer Contains a power supply transformer for Raytheon BH rectifier, 2 filter for UX 216-B rectifier, 2 filter chokes, 2 buffer condensers, and a chokes, and a filament supply of 712 filament supply for UX 171 power volts for UX 210 power amplifying amplifying tube. tube. $15.00 $20.00 The Complete Foundation Unit for power amplification and B supply Simplified Assembly. The Power Compact con- The R -210 type assembly will deliver 400 volts to tains within itself the greater part of the complete B the plate of the power tube, and in addition, will sup- supply unit. With the Type R -171, only 14 leads ply a constant 90 volts to the receiver at any current complete the Raytheon assembly. All terminals are drain up to 40 milliamperes. carefully located for the greatest ease of assembly. Silent in Operation. There is no traceable hum, Compactness. The only additional apparatus re- either mechanical in the compact itself, or electrical quired to build the B supply are the condenser block through the loudspeaker. (Raytheon type), a Raytheon tube BH, and the resist- Complete Supply for Power Amplification. The ance units. The complete eliminator occupies a space Power Compact not only supplies B voltage, but also of but 6 in. x 9 in. without crowding. provides for the filament current and grid bias of the High Efficiency. The power supply of either Power stage of power amplification. Makes it possible to use Compact furnishes the proper current for maximum power amplification even on sets designed for dry bat- efficiency of the rectifiers used; the chokes are of suffi- tery operation. cient capacity to carry the maximum output. Conserv- Electrically Centered Filament Supply. The atively rated, will not heat up in continuous service. power tube filament supply is tapped at the exact elec- High Voltage Output. The R -171 Power Compact trical center for grid return. The center tap is taken assembly will deliver a maximum plate voltage output from the common lead of two perfectly balanced wind- of 300 volts at 30 milliamperes, or 275 volts at 40 ings- completely obliterating the A. C. hum. (An ex- milliamperes. clusive Thordarson feature.) Write for instruction booklets SD -49 and SD -50. If your dealer cannot supply, order direct from the factory. THORDARSON ELECTRIC MANUFACTURING CO ?ransforrner Specialists Since 1895 WORLDS OLDEST AND LARGEST EXCLUSIVE TRANSFORMER MAKERS 'lfuron and Kingsburz, Streets -- Chicago.Ill. ESA. 3446

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www.americanradiohistory.com The Unique Service Rendered by POPULAR RADIO "POPULAR RADIO occupies the unique position of supplying its readers with `popes lar radio news,' combining strict technical accuracy with ease of comprehension. Here the engineer and the layman find a common interest in its pages. The greatest commendation I could give POPULAR RADIO is the lively interest and pleasure with which I read each copy."

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GENERAL MANAGER, THE KEN -RAD CORPORATION

www.americanradiohistory.com AVERA6EMON7HLYS/4/YAL AN07ENPE.PATizPE '924

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How Signal Strength Follows Changes in Temperature Dr. L. W. Austin of the United States Bu- reau of Standards, seated at the right, finds that the air temperature has important in- fluences on radio transmiesion. Two of Dr. Austin's graphs, reproduced above, show clearly that the strength of the radio signal corresponded with the average air tempera- ture during 1924. The temperature curve is inverted, higher temperatures being toward the bottom of the chart.

Underwood & Underwood mrr

www.americanradiohistory.com VOLUME X December, 1926 NUMBER 8

She Effect of Temperature on SIGNAL STRENGTH Newly -collected data on the part that hot and cold waves play in radio reception holds out the prospect that "radio weather" will be forecast as accurately as the Weather Man now predicts rain and shine.

By E. E. FREE, Ph.D. rr HE striking difference which exists received on the Bureau's antenna at atmosphere, appears to be unmistak- 1 between the good radio conditions Washington from the transatlantic radio able. of the winter months and the relatively stations at Tuckerton and New Bruns- A few moments study of Dr. Austin's poor transmission that is apt to be ex- wick, New Jersey, showed an apparent comparative curves will convince any- perienced in the summer is a good deal variation with the temperature of the one of the reality of the temperature of a mystery. air. In particular, the winter months effect. Even during relatively cold peri- In spite of many suggestions and some of that year were characterized by ods, a temporary increase of air tem- partial explanations, the difference in several distinct cold waves. These peri- perature will be reflected at once in a radio conditions between the colder ods of intense cold had noticeable diminution of radio transmission. At- months and the warmer ones remains effects on the received signal strength at mospheric heat is bad for radio; at- inexplicably large. It is quite true that Washington. Dr. Austin's curiosity mospheric cold is good for it. That is there are more atmospherics in the sum- was aroused. After announcing the the clear meaning of the graphs. mer. These annoy the listeners and in- effect apparently detected, he began The same conclusion is apparent from terfere with the clarity of reception. records which would determine, over consideration of the monthly averages. But that is not the point. Even when a period of many months, whether the The average signal strength during the the actual strength of the received signal temperature of the air really is to be month of February turns out to be more is measured electrically, so that the dis- considered one of the effective factors. than twice what it is during the month turbing effects of lightning flashes and These observations* are now available of July. The February figure is even other sources of atmospherics are elim- over a period of more than two years. substantially larger than it should be inated, the winter signal is found to be They show a clear relation between the according to the usual law of decrease much stronger and more reliable than two daily conditions, the temperature of signal strength with distance. the summer one. of the air and the strength of the re- The distance of transmission used in Undoubtedly meteorological factors ceived radio signal. The effect is an these tests is within the range of dis- are involved in this difference. Differ- inverse one; when the temperature is tance most likely to disclose, Dr. ences in air pressure have been invoked high the radio transmission is low, and Austin points out, any atmospheric by some investigators. Others have rice versa. Other factors are evidently effects which may exist. It is neither blamed the greater moistness of the at work also, for the effects of tempera- too short nor too long. Over longer summer air. Still others lay the differ- ture are sometimes obscured. But that distances, like that across the Atlantic, ence at the door of mere temperature, these effects exist, that temperature the weather is not likely to be the same certainly the most obvious place to lay does alter the radio conditions in the in all parts of the path followed by the it, for the outstanding difference between waves. A cold wave at one point may is that the *The results obtained by Dr. Austin will be pub- be cancelled by a hot spell at another the winter and the summer lished presently in a paper delivered by him before latter is the warmer. the Institute of Radio Engineers. By Dr. Austin's point. And for very short distances the courtesy, POPULAR Raub is permitted to an- the atmosphere do not Over two years ago, in 1924, Dr. L. nounce in this article some features of the results effects due to United States Bureau and of their probable meaning, together with a have opportunity to show themselves. W. Austin, of the graphie representation of the results themselves of Standards, noticed that the signals as reproduced on other pages. The distance from New Brunswick to 763

www.americanradiohistory.com Page 764 POPULAR RADIO Washington is 175 miles. From Tuck - received strength of both stations was these waves from Tuckerton or New erton to Washington is 156 miles. Both reduced to the basis of a 600-ampere Brunswick probably consisted of two of these distances lie, therefore, within antenna current for New Brunswick parts; the part that came through the the range between, 100 miles and 200 and of a 500- ampere antenna current for atmosphere and the part that travelled miles, which is probably about that Tuckerton. Different days are, there- along the ground. Either or both might within which the effects of alterations fore, entirely comparable. be affected by temperature. of the atmosphere would be expected to At first sight, it may seem that the That the real effects are largely in the play their maximum role. The wave- differences discovered are perhaps ex- upper levels of the air is indicated, how- length of the New Brunswick signals plainable as due to changes in ground ever, by Dr. Austin's further observa- during the tests was 13,600 meters. conductivity, rather than to effects of tion that the signal strengths in ques- That of the Tuckerton signals was the air temperature. Like almost all tion are not affected materially by long - 15,900 meters. In the calculations, the radio waves over moderate distances, continued rains or droughts or by the 2 20 /0

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/ 2 3 4 5 6 7 8 9 /0 // /Z /3 /4 /5 /6 /7 /8 1.9 20 2/ 22 23 24 15 26 771,91980.3/ DyK OF A/O/YTH Note How Radio Follows Fluctuations in Air Temperatures These curves show the daily deviations from the monthly averages for both temperature and the strength of the radio signal, as indicated, respectively, by the broken line and the solid one. When the temperature moves downwprd from the monthly average, the radio signal usually increases. The clearest instance on these graphs is during the week of December 25, shown at the right -hand end of the lowest curve.

www.americanradiohistory.com DECEMBER, 1926 Page 765

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\J L,. 5,a1e 1II.3I0.000 __ '.. --- I -- L /á01e, 30.0 What the Weather Map Told the Radio Fan Last December The map above shows average temperatures and air pressures (black lines) and average winds (arrows) for December, 1925. The United Slates Weather Bureau publishes these maps for every month. Below is the experimental radio receiving station of the Bureau of Standards at Kensington, Maryland.

Underwood & t nut nsood presence of snow on the ground. All mosphere at once; indeed, it is the itating some of it as rain. Warm air of these conditions, especially the soak- arrival of colder atmosphere from farther holds much water; if the air is cooled a ing of the ground by rain, have marked north or from higher up above the earth part of this moisture is instantly thrown effects on ground conductivity. The which causes the cold wave. On the out of the air, usually as fog, rain or fact that they do not importantly affect other hand, such cold waves do not snow. the radio transmission tends strongly immediately affect the conductivity or Another difference between warm and to prove that over the distance and with other characteristics of the ground. cold air is in its density. Cold air is the the wavelengths concerned the received It is safe to conclude, then, that the heavier, quart for quart or cubic mile for transmission is largely through the air. effects of cold or warmth on radio trans- cubic mile. It will sink beneath warm It was noted, also, that relatively n.ission are effects in the atmosphere. air, thus setting up more or less violent rapid changes of radio transmission The next question is that of what atmospheric circulations. It is also occurred at the times of the well - causes them. true, usually although perhaps not nec- marked and wide- spread falls of tem- Dr. Austin does not commit himself essarily, that cold air tends to contain perature with which we are so familiar to any opinion about this, and, indeed, fewer dust particles than warm air. in the United States and which we call no final opinion is possible in the pres- In its electrical properties, which are, "cold waves." It was the effects of ent state of our information. A change of course, the ones most likely to affect these waves, it will be remembered, of temperature does many rather di- radio matters, the cold air is apt to con- which first drew Dr. Austin's attention verse things to the air. It alters, for tain fewer electrified air atoms or "ions" to the problem nearly three years ago. example, the amount of water vapor than does warm air. This gives it a The cold of such a wave affects the at- which the air can hold without precip- (Continued on page 856)

www.americanradiohistory.com Page 766 POPULAR RADIO WANTED A Radio Humorist

WE are greatly in need at once of a number of good radio hu- morists, male or female. Applicants must be able to make-people laugh without hurting anybody's feelings. Steady employment, good salary and short hours. Don't wait to write -apply by wire. -BROADCASTING DIVISION ANY RADIO CORPORATION

By HOMER CROY

"'PHIS is the story of a firm which had settled back in their luxurious chairs at The bright business men had made a Bright Idea. home, prepared for a good old-fash- the discovery that what is funny on the It was a big firm with big money and, ioned stomach laugh. stage is not necessarily funny on the it liked to think, with big ideas. It had The comedian pulled his opener; it air. been watching other concerns going on was pretty poor, but the business men The reason that the great comedian the air and getting a lot of indirect ad- smiled and waited for the fun to grow so much resembled Sidney Carton on vertising by putting over something in hot and heavy. the scaffold was that he was the kind the radio line, and so it decided to do a But it didn't. Instead, it seemed known on Broadway as a "prop" little of the indirect stuff itself. more like what the boys are finding at comedian. That is, his pockets were But instead of going in for music and the North Pole. filled with strange devices and much of a classical program, it decided to put on The comedian pulled more of what his humor consisted in pulling out these "something different." he thought were sure-fires and went various articles and in talking about "Why not give 'em something fun- through his bag of tricks and a great them, or trying them on, and also in ny?" said the president. "People like sadness settled upon the faces of the wearing strange clothes. It wasn't to laugh." waters. And also upon the faces of the legitimate humor; it was eye humor - It sounded good -just awfully good. bright business men, and now and then and Mike has no eye. He is all ears "We'll get the best comedian on they had sharp shooting pains in the and if the humor isn't ear humor, why Broadway, play him up and put over region of the pocket -book. They then it is a total loss. some thing that'll make 'em talk," said themselves had gone to the theatre and And that explains why radio humor is that up-and -coming man. laughed and pounded their neighbors so hard to get. So they got a comedian who, in the on the back and had pulled at their In all other lines of entertainment we pure English of Broadway, was a wow. own suffocating collars, but now their have great comedians and humorists, So big was he that his name out in front collars were plenty loose. people who are known far and wide for could fill a house and when he went on Why was their comedian a riot in the their ability to create laughs- actors, tour they had to turn 'em away. And theatre and a funeral on the air? They humorous writers, comic artists, and so popular was he that he was always couldn't understand it. so on -but as yet there is no great radio being impersonated; and the newspapers At last, the comedian finished and humorist. He will have to be de- constantly quoted his wisecracks. was led away from the vibrating plate, veloped -and it is a good field to get The time came with the great come- and the agony was over and the bright into by any one who has the ability to dian out in front of the microphone and business men had only to think of the tease a laugh out of the immutable the bright business men with ideas fat check, outward bound. microphone.

www.americanradiohistory.com DECEMBER, 1926 Page 767 Many a famous comedian from the stage has stepped in front of the micro- phone with the world ready to applaud -and then had to back away, a Hamlet in modern clothes. And because a person is funny in some other line doesn't mean that he will be a success over the radio. Charley Chaplin, the world's greatest comedian, is, when he goes on the air, pretty -but 'twere kinder not to dwell on it. And Harry Lauder, who has made the world laugh, is not a success when his wig and his crooked stick are taken away from him and he finds himself alone in the sound-proof room. One reason, is that his accent is so thick and his rrr's so burry that they get all mixed up in the machinery and the people can't make head or tail of them. Another reason, is that only a lim- ited number of people in the United States know enough of the Scotch dialect to understand the stories. Radio has to pick something that everybody high and low, east and west, can under- stand, and what chance has a Swede in Minnesota to understand a Scotch story? "Hoot, man, ninna a nickel," Scotch goes fine on Broadway (I refer of course, to the dialect), and also it goes well and is understood in the larger cities, but at the cross roads it is a bunch of lilies. Up to the present time the only general humor that has been successful, when given the freedom of the air, is singing humor. It is understood by all, it is in verse and it has the added pull of music. One does not have to catch all of it to understand it. The opposite is true in a humorous story. One has to listen closely, to get every word, or the point will be lost - and there are fewer sadder things in the Posed by Raymond Hitchcock world, m'lord, than a joke without a funny make -up, was not wanted by the house lights on so that he can study point. People like to use the radio to radio audiences. the faces of the audience and tell ex- help entertain their friends; they like to And here, it is interesting to note actly how the audience is responding turn it on and to chat away while the that the English vaudeville comedians to his jests, and he gets his inspiration music lends a pleasant, stimulating -"variety artists," they call themselves in turn from the audience. But in the background. This they can't do when -are more successful when transferred broadcasting studio, when the actor it is a humorous story. They have to to the radio than are ours. The reason steps in front of the trembling tym- take it as it comes, or not at all. is this. In England they have what is panum, inspiration has flown out the At first, it was thought that the fail- known as the "red nose" comedian; window; his "audience reaction'''' is ure in radio humor was due to the poor that is, when he comes on his only make- gone and he might just as well be holler- choice of comedians, and so the powers up is his red nose; he has to depend for ing down a rain barrel. behind the broadcasting stations de- his. laughs on lines -not on his gro- Another reason for the poor quality cided to get vaudeville comedians. tesqueries. He has worked over these of the humor which comes over 'the They had, so the radio people thought, lines, he has polished them and re- radio is the number of restrictions put the ability to make people laugh; they vised and tested them until they are upon it. Radio humor must not offend had eliminated the poor lines until their all white meat, and so when he goes anybody -any race, any religion, :. y pattern was almost sure fire, and so the before the microphone he has more class of people -and it mush vaudeville comedians were brought be- nearly what the radio audience wants simple that it can be undcrs s .. s y fore the microphones and hope was in than has the comedian who expects a all. Great numbers of radio listeners every heart. But when the comedians funny hat and a mother-in -law joke to are children, or people in their 'teens were heard without the glamour of the get him by. and the humor must be of such a nature footlights and without the oddity of One reason why humor over the as to appeal to them. Sophisticated or their clothes to add to their effect, they radio is so flat is that it lacks spontane- subtle humor would go over their heads. fell as flat as flypaper. Their chatter, ity. As a result a joke that will appeal to divested of the surroundings and the A vaudeville actor works with the young and old, to the intelligent and

www.americanradiohistory.com Page 768 POPULAR RADIO to the simple -minded and which has a home, before the wife and children and would not be understood so well, and point that will not be at the expense of maybe grandma knitting in the corner as a result many in the radio audience any class or race of people is almost (that is, if grandma knits any more) would muff the story. impossible to get. If the radio did not why, then it is a horse of a different One reason that radio humor usually have such a wide audience it would be color. is such a total loss is that it lacks spon- much easier to find humor for it. The joke that goes out over the radio taneity, and this is due to the fact that Recently a patter comedian was put must, above all other things, be clean the actor has nothing to bring out his on at a studio not a hundred miles from and wholesome. The club smoker and best. He recites his pattern without New York and, after singing a comic after-dinner variety of a joke is a total knowing whether it is going over or not song or two, began to tell funny stories loss. and trusts to luck. If the element of about plumbers. The stories were fairly The radio stations are not in favor of spontaneity could be injected into it funny and the studio was well pleased, Jewish stories, funny as they may be, then the quality of the humor would be but the next day there was a vigorous for the reason that many Jews are sensi- much higher. The funniest thing that protest from the secretary of a plumbers' tive about them and write in complain- has ever been sent over the radio was union and also letters from a number of ing letters. The Scotch story goes the result of this unexpected quality of plumbers and their families protesting much better than the Jew joke, but it spontaneity. against the great injustice that had is not a success away from the large Graham McNamee and Major White been done them. cities where the Scotch dialect is better had been sent out to report a football Funny stories are not a success over understood than in the small towns game in Philadelphia, and, as is known, the radio; that is, the average funny where they think all Scotchmen look these two are friendly rivals. The story is not. At first, the powers be- like Harry Lauder, for it must be re- learned gentlemen took their places on hind the radio thought that it would membered that anything that goes out the sidelines with their headpieces on, be a splendid idea to hook up the radio over the radio must have a universal and all was set for the game. It had on some after- dinner speakers and let appeal. It can't be aimed at just one been raining and Major White was the people at home have a hearty class of people. sitting under an awning, laughing and laugh. And the microphone was trotted As a whole, a dialect story has hard smiling and at peace with the world. out and set up before the speakers' sledding, but there is one dialect story McNamee, a few yards away, was wait- table, but if anybody at home laughed that is almost sure fire -the negro story. ing, ready to begin his announcing; in no record was ever found of it. After- None of the larger stations have a ban fact, he had started and was now filling dinner stories don't go over the radio. against it. One reason that the negro in time until the game really began. In fact, the ordinary, everyday funny story goes over so well is that it doesn't And then unexpectedly something hap- story doesn't go at all. There are a hurt anybody's feelings. The negroes pened. Water had accumulated in the number of reasons for it. In the first themselves are not sensitive about a awning directly over White's head, and place, a good many after-dinner stories negro story, as it usually deals with the canvas had sunk lower and lower are off color, or their humorous kick the race gently -it has no mean, biting under the great weight without that depend on a double meaning. The spirit behind it Another reason is that talented announcer noticing that any- radio can't take these into the home. the negro dialect is a slow, musical, thing was wrong with the world. Sud- A risque story may sound just awfully easily -understood dialect. It has what denly there was the cruel sound of rip- funny at a college fraternity dinner- is known as "microphone quality," and ping, a heavy gurgle of eager water and especially if there has been a little wee also practically everybody in the then a little Johnstown flood descended doch and dorris -but when that story United States knows the negro dialect. upon that famous hero. McNamee is turned loose in the privacy of a The same words transposed into Scotch happened to be looking at him at the time and saw the great astonishment which came over Major White's face, and also what spread over his clothes, and Major White's frantic efforts to disentangle himself from the lines and the clinging canvas. McNamee began telling exactly what was happening - describing what he saw and he laughed so heartily at what he saw and at the strange contortions that the otherwise dignified Major White was going through that the people on the receiving line began to laugh too. The descrip- tion and the merriment kept up for some five minutes, McNamee all the time laughing heartily. In all, it was the most spontaneous and humorous epi- sode ever transmitted over the radio. And much of its effect was due to the hearty laughter on the part of the announcer. Katie! 4 lierber t What he saw and heard was funny "EYE HUMOR" MUST BE SUPPLEMENTED WITH to him and he succeeded in making it "EAR HUMOR" Ulu to his audience. No matter how funny comedians whose fun depends upon make-up A professional humorist who has the props may be their humor is lost upon a radio audience unless give the sounds that they make are in themselves funny. These "Radio ability to a turn this feeling of Aces" (Macy and Scott) for example, must get over with their unseen freshness and spontaneity is Will Rogers. audiences without the aid of the props that are drawn in this picture. (Continued on page 804)

www.americanradiohistory.com DECEMBER, 1926 Page 709

UNCLE SÁ111.5 SHORT- The chance that the Army is iving F. t e I\amateur to render public servit pea o \\ By CAPT. J. L. AUTRE' SIGNAL CORPS, U. S. A.

ONE OF THE CENTRAL STATIONS IN THE RADIO NET The radio "shack" and antennas of amateur station 2SC, which is operated by the U. S. Signed Corps at the headquarters of the Second Corps Area, Governors Island, N. Y. Three antennas may be seen; the vertical transmitting aerial, the inverted "L ", used for reception, and the outside loop.

THE transmitting amateurs' para- Three communication networks are trol and supervise all traffic to and from dise, the short -wave territory of provided for in the War Department's their respective subsidiary stations. the ether, has not escaped the eagle eye scheme of affiliation of the amateur with A second network, known as the of the military authorities. Indeed, the the Signal Corps. The first of these is Division Radio Net, links the Corps sympathetic support of the representa- known as the Corps Area Network. Headquarters Stations with brigade, tives of the army has always been a bul- A headquarters station is located in regimental and reserve units within wark of defence when the amateurs' each Army Corps Area which acts as each Corps Area. rights to the ether have been assailed. liaison agent for the army. This station Finally there is the Governor's Radio The amateurs' part in the war is an supervises and maintains communica- Net which places him in touch with each old story, but the army's participation tion with the amateurs co-operating unit of the National Guard in his State. in amateur radio is comparatively new. with the Signal Corps. A certificate of A unit in this system which is conspicu- Plans have been in the process of prep- appointment is issued to all amateurs ous for its efficiency and for the charac- aration for several years but now we who volunteer and have been recom- ter of its equipment is that installed at have more than plans; we have army mended for an assignment. A net con- the headquarters of the Second Corps stations that have been specially de- trol station, consisting of a principal Area, Governors Island, N. Y., and signed and constructed for communi- and alternate is selected for each reserve operated by the personnel of the Fourth cation with amateur stations. division and each Governor's net to con- (Continued on page 83e)

www.americanradiohistory.com Page 770 POPULAR RADIO

COIL 1 COIL 2 Coll. 3 In this single -layer solenoid coil the turns This coil is wound of insulated wire in a An entirely self -supporting lattice-work coil are spaced and automatically wound on a lattice -work form; it will be noted that it is that has no dielectric except the silk insula- cellulose cylinder. entirely self-supporting. tion on the wire.

119W CIRCUIT RESISTANCE AFFECTS SELECTIVITY Practical pointers about coil resistances in the radio- frequency circuit for the experimenter who is planning a receiver that will give the maximum of selectivity -and at the same time a good tone quality.

By GLENN H. BROWNING

WHENEVER radio experimenters This circuit is shown below in Figure6. is not adjusted to its resonance value. get together it is a pretty sure bet Let us suppose that the coil, L, is a Thus, we may say that a coil and con- that the talk will turn sooner or later to large coil or loop.with the waves from a denser have the same property in the the subject of coils and radio-frequency broadcasting station sweeping past it. electrical world that a spring with a resistance. And it is nearly as certain These waves carry with them, or rather weight attached has in the mechanical that the usual conclusion will be reached, are made up of, what we call an electro- field. The weight is analogous to the that if we could make a perfect coil and static and an electro-magnetic field. coil while the spring represents the con- condenser we could make receivers that The electro-magnetic field passing the denser. Now, suspend the weight on the would tune with perfect selectivity. loop sets up a small electro-motive force end of the spring so that it will be free to But the trouble with this whole con- in every turn of wire. This creates a bob up and down and tap the weight at clusion is the fact no one has had much difference of electric pressure between regular intervals. to say about quality of reception. For the ends of the winding. This tapping corresponds to the elec- even if we could make a receiver that This electric pressure charges the trical impulse that is given the coil by was perfectly selective in this way (and parallel condenser which, when charged, the broadcasting station. Then, sup- it must be remembered that selectivity tends to discharge and send a current pose, that you adjust the length or is not wholly dependent upon coil and back through the loop. If the broad- stiffness of the spring until the regular condenser resistance), we would be apt caster is transmitting at a wavelength tapping occurs every time the weight to spoil the quality of reception at the of 300 meters (a frequency of one mil- starts its upward swing. This is me- same time. For some of the better coils lion cycles), the magnetic field passing chanical resonance which comes at the already have about as low a resistance by the loop reverses a million times a point where a regular impulse of definite as is consistent with good quality. second; this means that the electric strength builds up the most motion in The lowest -loss coil, as nearly every pressure or electro-motive force at the the weight and spring system. The one knows, is the single -layer solenoid terminals of the loop also reverses at the motion built up, at resonance, cor- in which the winding is spaced approxi- same rate. Thus, the condenser is responds to the current built up in the mately one -half of the diameter of the charged first in one direction and then coil, and condenser system, at res- wire. in the other direction. onance. The best way to find out how a radio If this condenser is adjusted to It will be noticed in the above experi- receiver operates is to gain an exact resonance, a large current is built up ment that the regular tapping on the understanding of the phenomena that in the coil and condenser circuit, and a weight builds up very little motion, if take place in the fundamental circuits. difference of potential is established the spring is not adjusted to the correct In this case we shall take under con- across the terminal of C which is 100 to value. sideration a circuit that is fundamental 300 times the difference of potential In the same manner, a broadcasting in all radio sets, a coil connected in that is impressed on the loop by the station builds up little current in the parallel with a variable condenser. broadcasting station when the condenser electrical system unless the condenser

www.americanradiohistory.com DECEMBER, 1926 Page 771 .03

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HOW N VARIES WITH THE WAVELENGTH FIGURE 1: This curve -chart shows the variation of N (as explained by Mr. Browning) with the wavelength of six different kinds of coils that are illustrated through the article. Notice that N for Coil 5, which is a bunched wound coil, is higher than over any of the others; this indicates that this coil is not a good coil to use.

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XVC 3/0 370 330 340 350 340 370 360 CAPACDAL .I O%R3/C!NS.FA.P.10s a 7 i 5 4 3 2 / O / 2 3 4 .4. 6 7 Q 9 THE RESONANT VOLTAGES OVER A SHORT WAVELENGTH BAND FIGURE 2: This chart indicates the increase in voltages at resonance over coils having varying values of N. Notice that Coil 4 with a value of N of .0001 has more than three times the voltage resistance of Coil 1 with an N of .01.

www.americanradiohistory.com Page 772 POPULAR RADIO

?00 300 400 500 600 lOWELEN6TH- METERS RESISTANCE PLOTTED AGAINST WAVELENGTH FIGURE 3: This chart shows the resistance values of the coils under consideration at various radio frequencies; notice that Coils I and 6 have approximately the same resistance values.

is adjusted to resonance. Broadcasting coil, L, either from an oscillator or from amount of voltage, E, that is set up stations on different wavelengths have a broadcast station. Call this voltage across the condenser and let us see different periods of electrical vibration E. There is always a resistance in the what can be done to make it as large as which require, as we all know, different coil and condenser which we will repre- possible for the strength of the signals condenser settings to resonate the signal sent by R. Now let us calculate the (Continued on page 828) and make it audible. It is a fortunate thing for us that a coil and condenser have the property of selecting different stations at will for otherwise all stations within range would give a bedlam of sound in the loudspeaker. The question naturally arises, why is one coil and condenser more selective than another? The answer lies partly in the amount of resistance that is present in these two pieces of apparatus, for that is what damps the oscillations. We uld our weight spring system build up a greater amount of motion if the weight were C suspended in air or if it were immersed in alcohol? The answer is that the .0/ alcohol would naturally retard motion more than air. The spring immersed in alcohol cor- responds to a coil and condenser that /00 200 300 4Q9 5A'J 600 700 900 900 /01:0 have great amounts of resistance in if AE L EN6 T h' - /3 ¡E TE PS them. N PLOTTED AGAINST WAVELENGTH Let us consider the circuit, shown in FIGURE 4: This figures Figure 6, a little more in detail. curve gives the general for the value N at various frequencies that include the wavelength band used for amateur broad- Assume that a voltage is set up in the casting and commercial transmission and reception.

www.americanradiohistory.com Page 773 DECEMBER, 1926

Bureau of Stand met; HOW A PIEZO CRYSTAL IS CUT only FIGURE 1: The piezo plate is cut out of a section of quartz crystals; it will oscillate if it is cut in the corred plane and contains no flaws. If the plate is cut roughly il is ground down smoothly to the correct thickness for the frequency to which it is to be used. The Salt on the Tail of the Broadcast Frequency How the tiny piezo crystal is serving the interests of the broad- cast listener by checking the wavelengths of stations and preventing interference between transmitters. * By MORRIS S. STROCK a piece of equipment. MOST broadcast listeners are all atus known as a "piezo crystal oscil- used as separate Bureau of familiar with the shrill heter- lator." For some time past the too with the whistle that often comes unin- This interesting apparatus has the Standards has experimented odyne frequency control; vited into their loudspeakers; and a useful quality of maintaining certain latter method of describes the apparatus good many of them know that this predetermined frequencies for an almost and this article were used to secure annoying whistle is due to interference unlimited time. If it is constructed so and methods that result. between the carrier waves of broad- that one of its frequencies corresponds the desired is a Greek word casting stations that have strayed too to the assigned frequency of a broad- The term "piezo" "press." "Piezo electricity" is far off their assigned frequencies. casting station and is operated in con- meaning by pressure upon certain crys- Few fans, however, realize that this junction with its transmitter, the sta- produced Rochelle salts, sugar and source of interference, at least, could be tion can never stray far off that fre- tals, notably fact was discovered about eliminated forever if all broadcasting quency. quartz, a that by the Curie brothers. stations could be persuaded to add to There are two ways in which the piezo forty years ago found that a reversed their equipment a tiny piece of appar- oscillator may be used to keep the fre- Later it was quency of a broadcasting station at a effect could be secured. This was ob- action of an electric 'Published by permission of the Director of the constant value. It may be included in tained through the National Bureau of Standards of the U. S. Depart- circuit, or it may be field upon a quartz plate cut from a ment of Commerce. the transmitting

www.americanradiohistory.com Page 774 POPULAR RADIO natural quartz crystal. The electric Figure 4 shows a schematic wiring utilized frequency field was supplied by of the piezo oscillator two metal plates diagram of the piezo oscillator as used and the frequency connected in an of the transmitting electron tube radio- by the Bureau of Standards; Figure 2 set. frequency generating apparatus. shows a completed piezo oscillator that The reason that a harmonic from the When a quartz plate was placed be- was built according to specifications quartz plate was used was to find tween the two metal plates, it was out prepared by the Bureau.* whether there would be less trouble from found that it could be made to control In the illustration it is shown ready a possible blanketing effect from or maintain a fixed value of frequency the in for operation except that the "A" and transmitting set than when the generating apparatus. Because a funda- of "B" batteries are not connected. The mental frequency of the quartz plate its physical characteristics, quartz was holder containing the quartz plate is were utilized. Of course there found to be more satisfactory for this was no shown attached to the right edge of the specific reason for grinding the plate purpose than other crystalline sub- cabinet, and an interior view of a plate stances. so as to utilize the 6th harmonic rather holder of exactly similar construction is than making (for example) the 4th Thus the term "crystal," as applied or shown at the lower left corner of the 5th harmonic equal 640.3 kc. to the piezo oscillator, is a rather incor- This cabinet. The same oscillator, in oper- harmonic frequency was made slightly rect expression for denoting this piece of ation, is shown in Figure 3. greater than 640 kc so that the trans- apparatus. The quartz crystals, in mitting circuit could be adjusted their natural state, are very much to The Technical Details of the exactly 640 kc by the pitch of the larger than the plates which are cut beat Tests of the Piezo Oscillator produced in the phones of the piezo from them. An idea of their size may be oscillator instead of utilizing zero gained from Figure 1, Arrangements were made with two beat by referring to the as in the second test. centimeter scale at left. of the Washington broadcasting sta- This principle the could, of course, The plates tions, WRC and WCAP, whereby the have been applied that are used in piezo oscil- instead to lators piezo oscillator, shown in Figure 2, a fundamental frequency of are even smaller than this, as may the quartz plate; be could be tested in the operating rooms it had nothing to do seen from Figure 2. " Piezo" is a with the much of these stations in order to determine fact that a harmonic was better term than "crystal," as utilized. the word itself suggests the action of the its possibilities.t For these tests, the Figure 3, shows the piezo oscillator quartz plate and as the plate is quartz plate was first ground so that the only a outfit during one of part of the crystal. sixth harmonic of one of its funda- the tests in station The terms "crystal WRC at Washington. controlled" and "crystal mental frequencies was 0.3 kilocycle$ The box at the checked", as right contains applied to transmitting (300 cycles) higher than the assigned "A" and `B" batteries stations for the piezo oscillator. equipped with one frequency of the broadcasting station; of the two forms of Imagine that the piezo apparatus previously next, the plate was ground so that transmitting set is mentioned, to be adjusted by listening may therefore be another of the fundamental frequencies to the beat somewhat misleading. produced by It is better to say "piezo was equal to the assigned frequency of the 6th harmonic of the controlled" quartz plate and "piezo checked." the broadcasting station. interacting with the fre- quency of the transmitting set. When it has been properly cut from The method of performing the tests The observer wearing the head phones the crystal, the quartz plate generally was to place the piezo oscillator near the hears a beat note with a gives three natural frequencies transmitting set in the operating room pitch equal to the which difference between are fixed by certain of the station and listening for the beat the frequency of the dimensions of the transmitting circuit plate. Even a disc- shaped note heard in the phones, which was and the oscillator. quartz plate He now varies gives these three frequencies. produced by the interaction of the the frequency of the transmitting set by rotating a knob As quartz is a durable and permanent on ',These specifications are known as Letter Cir- the control board. This adjustment is material, the frequencies which it gives cular 186. and may be obtained by request from the continued until zero beat is obtained. are equally permanent and constant. Bureau of Standards by anyone actually requiring them for constructing the device. The transmitting set is thus adjusted It is in this that the value of }Acknowledgment the quartz is due to the operating staff to 640.3 kc (the 6th plate in maintaining a frequency of stations WRC and WCAP for their cooperation harmonic of the stand- in arranging these tests. utilized frequency ard arises. of the piezo oscilla- (Hereafter written "kc." tor). The knob is now rotated a little further in a direction such that the fre- quency of the transmitting set is slightly decreased, this adjustment being con- tinued until the pitch of the beat note in the phones is estimated to be 0.3 kc (300 cycles). Thus the frequency of the transmitting set is brought close to the assigned frequency of 640 kc. In this test the apparatus was placed about six feet from the control board; and the beat note heard in the phones, while not loud, was of sufficient inten- sity to be readily heard through the other noises in the operating room. This test proved very successful; the observer had no difficulty in noting slight changes in the frequency of the transmitting set. Without A SET -UP FOR CALIBRATION making a comparison with an audio-frequency note of 300 cycles, it r FIGURE 2: This standard tvaverneter is crystal controlled; the crystals are mounted in the small redan polar blocks, one of which leans up was of course necessary to estimate against the end of the wavemeter and the other is connected to two bind- when the resulting beat note was of that ing posts in the wavemeter circuit. frequency. In this an error of even 0.2

www.americanradiohistory.com DECEMBER, 1926 Page 775

Bureau of Standards ADJUSTING A. TRANSMITTER BY THE BEAT NOTE METHOD FIGURE 3: The station may be set at its correct frequency by adjusting the wavelength so that the beat note obtained between its frequency and the frequency of a crystal -controlled oscil- lator is of a certain fixed audio-frequency value This is a simple way to check the fre- quency of any transmitter no matter how powerful it may be. kc (200 cycles) is unimportant as this those just described were repeated. Re- operating room, the transmitting cir- is a difference of only 0.2 kc or 0.03 ferring again to Figure 4, assume that cuit can, by this method, be adjusted percent from the assigned frequency of the observer is once more adjusting the very easily to within 0.1 kc of the piezo the broadcasting station. Tests at transmitting circuit to the piezo oscilla- oscillator frequency; in fact, if the head WCAP met with similar results. tor. In this case the proper adjustment phones would respond to a sufficiently The quartz plate was reground so that is obtained at zero beat in the phones of low frequency this adjustment couldbe it gave a fundamental frequency of the piezo oscillator. Barring inter- made to an accuracy of about 16 cycles, exactly 640 kc, and tests similar to ference from extraneous noise in the (Continued on page 807)

www.americanradiohistory.com Page 770 POPULAR RADIO

The Grimes "Inverse Duplex" Receiver This receiver, has an efficient inversed reflex system, an output filter and a logical volume control. The circuit gives good volume with a fine quality of reproduction; selectivity is obtained by means of two extremely sharp stages of radio-frequency amplification. Popular Radio Circuits INSTALLMENT NO. 5

THE PARTS THAT ARE RECOMMENDED FOR USE IN THIS RECEIVER ARE- RFT1, RFT2 and RFT3 -Lind R F coils; Cl and C3 -Sangamo mica condenser, R2- Centralah potentiometer, zero to RFC -Grimes radio-frequency choke; 00025 mfd.; 250,000 ohms; AFT1- Samson audio-frequency trans- C2, C4 and C5- Sangamo mica condenser, R3 -DeJur resistor, 1 meg.; former, ratio 2 to 1 001 mfd.; R4 -DeJur resistor, 24,000 ohms; AFT2-Samson audio-frequency trans- C6- Dubilier mica condenser, 1. mfd.; Grimes metal panel former, ratio 6 to 1; C7 -DeJur mica condenser .1 mfd.; Grimes metal instrument base; AFC-Samson audio output choke; GL -Lynch metallized resistor, 2 meg.; Grimes shields; VC1, VC2 and, VC3 -Lind variable air GC- Dubilier mica condenser, .00025 Grimes crackled finish cabinet; condenser, .000.5.mfd.; mfd. provided with grid-leak clips; 2 vernier dials; VT1, VT2 VT3, VT4 and VT5 -Ben- J- binding posts for the loudspeaker tips; Composition binding post strips; jamin sockets; R1-rheostat, 6 ohms; 4 Eby binding posts.

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www.americanradiohistory.com The "Infradyne" Receiver waves in This set has as a novel feature a new intermediate amplifier operating on short conjunction with an oscillator intended to obtain a frequency of this order by heterodyning within the broadcast range. Distance reception with this circuit with the initial signals of is readily attainable and when coupled with high -grade transformers, the quality be excellent. In the intermediate amplifier and the oscillator, l %X -I99 reproduction should a type. lype',tubes are tube is a the others are -'Ot This es the best results with fiftyfoot antenna.(IX

THE PARTS THAT ARE RECOMMENDED FOR USE IN THIS RECEIVER ARE - rheostat, No. 301, 30 RFTI, RFT2 and RVI'3-Tharola No. 33 C2 and C3- Dubilier mica bypass con- R3 -General Radio 1 mfd.; ohms; , doughnut,radio-frequency coils; densers, type; Remler lnfradyne (intermediate) C4-Sangamo mica condenser, .0005 R4- Amperite, 6V -199 IFA- Amperite, 1 -A type; amplifier; mfd.; R5 and R6- coil VCI, VC2 and VC3- Continental triple R7- Amperite, 112 type; LI., L2 and L3 -0scillator coils (each filament switch; With No. 24 DSC wire, 8, 14 and vernier air condenser; S-Yaxley wound V No. 135 voltmeter, zero to 5 14 turns respectively); VC4- Remler air condenser, .00035 mfd.; -Jewel mica condenser, .00025 volts; AFT1- AmerTran DeLuxe first stage GC1 -Sangamo circuit jack; transformer; mfd.; JI- Electrad closed- GC2 Sangamo mica condenser, .0005 J2- Electrad open- circuit jack; AFT2- AmerTra,n DeLuxe second stage baseboard, 10 inches by transformer; mfd., with grid -leak clips; B- hardwood GL1 -Lynch resistor, 1 meg.; 34 inches by u -inch; VT1, VT2, VT3, VT4, VT8, VT9 and panel, 7 inches by 30 VT10- Benjamin sockets; GL2 -Lynch resistor, 2 meg.; P- composition .0001 or R1 -U. S. L. rheostat, 10 ohms; inches by 3 /16 -mch; Cl-Electrad mica condenser, binding posta. .00025 mfd.; R2- U.S.L. rheostat, 30 ohms; 9 Eby

www.americanradiohistory.com Page 778 POPULAR RADIO EVERY broadcast listener is familiar with the tiny "whistlings" that he picks up among the wavelengths below 200 meters; they are the code communications the of ç amateurs. To the fan who can read them a new and fascinating "world of ether" is revealed.

DO NOT STUDY THE CODE BY VISUALIZING DOTS AND DASHES -BUT BY LISTENING TO "DITS" AND "DAHS" If no neighborly operator is available, the beginner can get good by means practice in reading code of the ommigraph, which transmits interchangeable messages at Incidentally, this machine is adjustable speeds. employed by the Radio Inspectora for testing the abilities of applicants for licenses. If You Want to Read the Code By HOWARD S. PYLE

RADIO broadcasting commanded arrangements of their own; and second Far down at the low end -two hun- the public attention to a far greater the class who were content to purchase dred meters and under, he will pick extent than had any previous scientific a good set and exert up their efforts to an a myriad of tiny whistlings exactly discovery, when the "radio craze" ar- endeavor to compile like a long list of distant those which he has come to know rived in 1922. stations which they had heard. as the The natural "carrier wave" of a broadcast station. consequence followed; Both classes of radio fans are hundreds, then thousands now This newer whistle, though, is broken up and finally found to be searching for new fields millions of enthusiasts to into alternate short and long sounds took up the new conquer. Witness any average man offering and introduced at variously intermingled. The tones are it into their the dial of his receiver of an evening, homes. Technical varied -from almost one extreme of the development natu- after an hour or so of logging distant rally kept pace, and, musical scale to the other and he knows with such an over- stations and listening to a few numbers whelming interest, them from experience, as the dots and broadcasting de- of their offerings; his hands are restless veloped at an astounding rate. dashes of the Continental radio-tele- and as they wander over the dials; it is graph code. Two classes of radio broadcast en- with rather an aimless purpose -just a Similarly, at the upper extreme thusiasts developed; first the experi- hope that he may run of his across something dial will he cross a similar series mental class who derived their greatest a bit out of the ordinary. of dots enjoyment from and dashes, probably of greater strength trying every hook-up Sometimes he will run into something available and and of more varied tone though more finally devising intricate that may stir his curiosity keenly. closely confined to an audible note of

www.americanradiohistory.com DECEMBER, 1926 Page 779 about five hundred cycles. Broader continental Europe and in radio com- There are several ways of doing this, tuning in a number of these waves will munication the world over, is distinctly the result of schemes formulated by in- mark the wave as that emanating from a process of sound and not sight; for dividual interested parties. A great a damped -wave transmitter, more famil- this reason, it is wrong at. the very start deal of research along the lines of code iarly known to him as a "spark to memorize the alphabet by calling instruction was carried out by the U. S. set" and long the subject of much "A" a "dot and a dash" "B" a "dash and Navy immediately after our entry into vehement protest from the great broad- three dots." You do not read a mes- the European hostilities and with the cast listening public, for the inter- sage coming into your headphones by establishment of the great Naval Radio ference of which it has been guilty Schools at Harvard, Great Lakes and these five years gone. Fortunately, elsewhere. The Navy was faced with progress in receiver design and agita- the problem of turning out thousands of tion leading to the almost forced aban radio operators in the shortest possible donment of spark transmitters has less- time and that they did this successfully ened this evil, though numbers of them was the result of the most advanced still exist. methods of instruction. And in every The average fan, has as yet, but little ...1 instance, it was found that the sound interest in the transmitting equipment \41. teaching of the alphabet was far supe- itself -but he is captivated by a curi- rior to sight, for one less mental process osity as to just what those mysterious was required. and elusive dots and dashes are saying. The Code Chart For example: a student hearing a short and a long buzz through his head- Here is a new field within the scope of Dah Method" and it seems to "Dit phones would immediately see a dot his present equipment A-Dit dah open the gate to a freshened interest in B-Dah dit dit dit and a dash when learning from the the receiving set that has of late gath- C-Dah dit dah dit sight method and he would then have ered a bit more dust than had been the D-Dah dit dit to exert his mental faculties again to E-Dit associating a dot and a dash with its case in the few years past. F -Dit dit dah dit Curiosity grows and a few casual G-Dah dah dit proper letter. inquiries among his friends brings out H-Dit dit dit dit On the other hand, the sound student the fact that they too have been in- I -Dit dit would hear' the short and long buzz and J-Dit dah dah dah immediately think the letter itself trigued by the peepings and wailings of K-Dah dit dah - the various code signals. A few eve- L-Dit dab dit dit not th, dots and dashes associated with nings later we find the average fan M -Dah dah it and then the letter. The resultant secretly poring over the conglomeration N -Dah dit instruction was greatly speeded up by the 0-Dah dah dah using the sound method and the stu- of long and short marks that form P -Dit dah dab dit code chart which he has purchased that Q-Dah dah dit dah dents speed increased at a far greater day from a young amateur at the local Il -Dit dah dit rate than when using other methods. radio shop -a knowing smile from the S-Dit dit dit For the sound purpose, the printed boy being the basis for that slight un- T-Dah code charts as commonly known in radio U -Dit dit dah circles, do not answer at all, in fact it is easy feeling. V -Dit dit dit dah Concentration for some two hours W -Dit dah dah strongly recommended that the student leaves him still in the dark as to just X -Dah dit dit dah not even allow himself access to the Y-dah dit dah dah familiar "dot and dash" code. Rather what the code is all about. Pride per- Z-Dah dah dit dit haps won't permit him to talk to the he should cut out the chart reproduced local amateur next door whom he once with this article, paste it on a piece of reported to the radio supervisor for The Numeral Chart stiff cardboard and carry it with him, "cluttering up the air " -though good- using it as his one and only alphabet ness knows the boy would be tickled "Dit Dah Method" card. pink to welcome him into the great ham 1-Dit dah dab dab dah It will be noted that a dot is called dah dab dah fraternity. So the fan pores over his 2-Dit dit a "dit" and a dash, "dah." 3-Dit dit dit dah dah illogical at collection of dots and dashes and 4-Dit dit dit dit dah It may appear somewhat learns little, the total extent of his ab- 5-Dit dit dit dit dit first thought and the student will per- sorption being that "a dash is equal in 6-Dah dit dit dit dit haps feel a bit silly to refer to the letter length to three dots." Even if he does 7 -Dah dah dit dit dit "B" for example as "dah dit dit dit," 8-Dab dah dab dit dit off it will be found get a somewhat shaky picture planted 9-Dah dah dah dah dit but this will wear and in his mind so that by knitting his eye- 10-Da -a-ah (Long dash) that he will in time become proficient brows and devoting all his faculties to NoaE: O is sometimes used thus: in talking to friends who also have code DAR DAH the problem he can say with some Little DAH DAH DAH knowledge by merely calling off the certainty that, "A is a dot and a dash," Common Punctuations "dit daha" corresponding to the letters he cannot co- ordinate the sight of the Period -Dit dit dit dit dit dit making up the sentence he wishes to dot and dash with its sound as carried Comma-Dit dah dit dah dit dah say. A refined "hog -latin" perhaps it dit dab dah on the ether lanes. Nor will he, for a Question Mark-Dit may be termed. dit dit For example, "How about it ?" can be long, long time, if he goes at it in that Attention Sign -Dab dit dah dit manner. dah transmitted by word of mouth by say- Mastery of an aural signal code, such ing instead, "dit dit dit dit -dah dah as either the Morse telegraphic alphabet dah-dit dah dah-dit dah-dah dit dit as used on the land-wires of the com- seeing the dots and dashes but by hear- dit -dah dah dah -dit dit dah-dah- mercial wire telegraph companies ing them. Therefore it should be the dit dit- dah." Awkward and clumsy throughout North America or of the aim of every beginner to form a firm probably it sounds, but good practice so- called Continental or International impression of the sound of the letter and for the code student and certainly a code used on the land telegraph lines of not the sight picture of it. (Continue(' on page 836)

www.americanradiohistory.com Page 780 POPULAR RADIO tiThe list of parts given below includes the exact instruments used in the set from which these specifications were made up. The expe- rienced amateur, however, will be able to pick out other reliable makes of instruments which have been approved by POPULAR RADIO and which may be used with good results. But we recommend that the novice follow the list, as the diagrams in this article will tell him exactly where to bore the holes and exactly where to place the connections. If instruments other than the ones listed are used, the only change that will be necessary will be the use of different spacings for the holes that are drilled in the sub-base for mounting the instruments. To any reader who has difficulty in obtaining any of the parts which are necessary in making up these model receivers and power units, POPULAR RADIO SERVICE BUREAU, 627 West .48rd Street, New York City, will gladly assist in seeing that his requirements are promptly supplied.

HOW THE UNITS ARE INSTALLED FIOURE 1: This picture wiring diagram shows the LC -27 receiver connected up to the "A ," "B" and "("' power and to the antenna, ground and loudspeaker. The input to the "A" supply units and the intermedioi, power -pack are connected in parallel to the 110-volt alternating current lines, so that no batteries are required. HOW TO BUILD THE LG Intermediate Power -pack This unit, which has been developed in POPULAR RADIO LABORATORY, was designed especially for use with the LC-27 receiver, although it will be found extremely satisfactory when used with any type of receiving set -provided that a UX -171 type power tube is incorporated in the last stage of amplification. By LAURENCE M. COCKADAY

COST OF PARTS: Not more than $47.50 I1ERE IS A LIST OF PARTS USED IN THE LABORATORY MODEL- A- Yaxley Automatic Relay Switch No. G-Acracon condenser block; 14 mfd.; K-Any approved high -current variable 444; H-Acracon Filter condenser, .1 mfd. for resistance Filtrex to dissipate 5 watts, 2,000 B- A-C Transformer, Type K -180; 400 -volt operation; ohms; (Centralab Resistance illus- C-Any approved UX type socket; (Na- I- Hardwood baseboard; 7s/ inches by 18 trated); ald vibrationless socket illustrated); inches by 3 -inch; Bakelite binding D- E L- post panel, 3% inches -Filtrex Choke Coils, Type K; J- Resistance unit, type 200, 20,000 ohms by 4% inches by 3 32 /inch; F F2, F3, F6; -Fl, F4, F5 any approved total resistance; tapped to obtain cor- 1 set POPULAR RADIO blueprints; binding posts; (Eby binding posts rect voltages; (Mfd. by Barwick, Connecting wire, twisted lamp cord, plug, illustrated); Field & Loeb); screws, etc.

FOR those radio fans who have built issue) for supplying "A ", `B" and "C" power tube in the set is supplied with the LC-27 Receiver (described in currents to the set, this Intermediate filament current from the "A" power POPULAR RADIO for October, 1926) and Power-pack has been specially designed. unit. The voltage supplied is correct whodonot need the greatvolume of sound This new unit, which is here de- for the operation of the UX -171 type can be that obtained with the LC-Senior scribed, has similar characteristics of the power tube in the receiver. This new Power -pack (described in the November LC-Senior Power -pack except that the unit gives the same type of quality re-

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THE PICTURE WIRING DIAGRAM FIGURE 2: The instruments in this diagram are drawn in about their relative positions, and the wiring is shown in heavy white lines. Notice that the input plug from the transformer, B, is inserted into the proper socket on the relay, A. The 110-volt lines should be connected to the power -pack by means of the input plug that is connected to the wires marked "to line" on this relay.

THE WORKING DRAWING FOR CONSTRUCTION FIGURE 3: In this drawing all of the parts are shown in their exact positions; these are gwen from center to center for all of the instruments. If these dimensions are followed carefully the home -constructed unit should function exactly like the original model built in the laboratoru.

www.americanradiohistory.com Page 782 POPULAR RADIO production as its larger brother and will sides of the baseboard, I, by means of shielding; and it is due to this as well as supply ample volume for ordinary home two screws as shown in Figure 4. These to the electrical design of the circuit that use. It furnishes over 200 volts for the screws are inserted through the two no hum is produced in the receiving set UX-171 type tube that is used in the last holes in the panel, into the edge of the to which it is attached. stage of the LC-27 receiver when oper- baseboard I. They should be strong, It is recommended that all wiring be ated from this unit. It supplies ap- round -head wood screws, preferably done with an insulated, solid, round proximately 90 volts for the first and brass. bus -wire.* second stages of radio-frequency am- Next, mount the control relay switch, When wiring up, the home-builder plification and for the first stage of A, by means of two wood screws. This should refer constantly to the picture audio-frequency amplification; it also should be mounted in the position in- wiring diagram, Figure 2. supplies approximately 45 volts for the dicated in Figure 3. Start the wiring by preparing the plate circuit of the detector tube. A Then mount the transformer, B, by transformer leads in the correct lengths. "C" battery potential of 20 to 50 volts means of two strong wood screws fasten- The color design of the transformer leads is also available from this unit for the ed directly to the wooden baseboard, I, is clearly shown in Figure 6. By com- power tube. and mount the two choke coils D and E paring this diagram with Figure 2 the The LC-27 receiver when operated in the same manner. The positions for proper wires to connect are easily de- from this unit and in conjunction with these instruments are also given in termined. the 110 volt 60 cycle alternating- current Figure 3. A short piece of twisted lamp cord supply will surprise the uninitiated list- Mount the socket, C, and the resistor, should be fastened to the two primary ener with the lifelike quality of the re- J, as shown in the same diagram. terminals of the transformer, B, and ceived broadcasting. Next, fasten down the condenser this should be attached at the other end block, G, as shown. Be sure that it is through a plug to the How to Construct the Power-pack relay switch, A. mounted in the exact position shown in The plug should be inserted in the socket After all the instruments and mate- the drawing with the terminals turned on the relay switch that is marked "B" rials for building the unit have been pro- and facing the resistor unit, J. Eliminator. cured, the baseboard, I, should be cut The last job is to mount the small Then, wire up the leads to the socket to the correct size, as shown in Figure 3. condenser, H, in position between the and the resistance, the condenser bank, It should be smoothed with sandpaper transformer B and socket C. This the chokes and the binding posts. Be and given a coat of shellac. should be fastened to the baseboard I sure that none of the leads touch each Next, the small panel, L, upon which with two small, brass wood screws. other when they are made with the are to be mounted the binding posts This completes the construction work "Celatsite" wiring. They should be Fl to F6 and the "C" battery control, and the Power -pack is now ready to be spaced about % of an inch wherever K, should be prepared as shown in wired. necessary. Figure 7. When all the holes are drilled When the wiring is completed the How to Wire the Unit the six binding posts should be mounted Power -pack is ready to be installed. and the variable resistance, K, should The mechanical and electrical design be fastened to the panel L, as shown in of this device have been worked out with *The type of bus wire used in all the experimental models of this unit was "Celatsite. ' Figures 2, 3 and 4. The panel, L, may extreme care during months of experi- then be fastened on one of the long ment and test. The whole unit is self- (Continued on page 810)

A VIEW OF THE POWER-PACK AS SEEN FROM ABOVE FIGURE 4: The relative position of all the parts that are mounted on the baseboard and the connection panel; the parts are designated with letters that correspond with the list of parts and with those given in the text.

www.americanradiohistory.com DECEMBER, 1926 Pagr 783 "FROM FIRE AND FLOOD -" What five radio amateurs of Oklahoma did to win the POPULAR RADIO MEDAL FOR CONSPICUOUS SERVICE

Alvin C. Krupnlck. Tula* THE SENDER AND THE RECEIVER OF THE CALL FOR HELP The first call for help for the inundated area came from amateur station 6SR of Sand Springs; it was picked up by amateur station 6SG of Tulsa. From that moment amateur radio played an im- portant part in the rescue of lives and property.

By LLOYD JACQUET HALTON H. FRIEND, 59R RAYMOND V. KINNEY, 58G ON the morning of June 9th, 1923, of Sand Springs had been silenced. hurried signals from the Sand Springs the inhabitants of Sand Springs, Thus, at midnight of the first night amateur: Oklahoma awoke to find their small of the flood, Sand Springs was envel- "Will you take traffic for Tulsa? city several feet under rushing water. oped in a darkness more swilling than Urgent!" The highways were impassable, the that of the leaden cloud -laden sky Would he take traffic? Of course he streets inundated; and the railroads above. No news could be had from the would. Every amateur station does useless. Rushing waters from the over- outside. Worse yet, no news could be that, as a matter of service. flowing Arkansas River, augmented by sent out from the stricken area. . So 5SG nonchalantly switched over to a bad storm, had precipitated a flood. Such were the desperate conditions in his transmitter, and said: And the breakdown of all communica- the middle of the first night. "O. K., O. M.... GA!" which, in tion lines with the outside world made And then the radio amateur came to the snappy language of the amateur it impossible to tell the neighboring the rescue. code means, "Certainly, Old Man, go cities about the damage done or to As that last line of communication ahead, I'm ready!" summon aid; under the rush of water, was breaking under the combined strain But of course, McKinney did not poles supporting telephone and tele- of traffic and storm, amateur radio expect the flow of traffic which followed. graph wires had fallen, and destroyed fingers were weaving an invisible link For several hours young McKinney, the precious remaining links with the which would withstand all assaults. who was only a fifteen -year old member country with one lone exception. Shortly after midnight, Raymond V. of the amateur fraternity, labored hard, That one exception was a telegraph McKinney, an amateur then located at writing down the scores of messages, line. 1342 North Elwood St., Tulsa, and reports, news bulletins, notes, and All messages, consequently, were owner and operator of station 5SG was traffic of all kinds for Tulsa and other rushed to this single line. Messages of sitting at his apparatus, just "tuning points. assurance, messages of query, mes- around." Suddenly, he stopped whirl- So the first contact from Sand Springs sages of hope. ing the dials of his short wave receiver. with the outside world, other than with With this inrush of traffic, the line Station 5SR, owned by Hatton H. wire and messenger had been success- became quickly over oaded. And sud- Friend of Sand Springs, was calling him fully established. denly, in the middle of a message, the -and calling him desperately. The first news accounts which trickled line gave out. With a quick, business like click, he into the newspapers of the country the The last line of communication out acknowledged the call. Back came the (Continued on page 814)

www.americanradiohistory.com Page '784 POPULAR RADIO

THE SCHEMATIC WIRING DIAGRAM FIGURE 2: This diagram shows in schematic form just how the power -pack works. Separate circuits are used for the "A" and "B" current su ies; these circuits, of course, are con- nected in par .

The list of parts given on page 785 includes the exact instruments used in the unit from which these specifications were made up. The experienced amateur however, will be able to pick out other approved makes of instruments which may be used with good results. But we recommend that the novice follow the list so as to be sure to obtain results similar to those obtained with the laboratory model. To any reader who has difficulty in obtaining any of the parts which are necessary in making up these model receivers and power units, POPULAR RADIO SERVICE BUREAU, 627 West /43rd Street, New York City, will gladly assist in seeing that his requirements are promptly supplied.

THE PIC ruI E WIRING DIAGRAM FIGURE 3: This drawing, which shows the positions of the instruments on the baseboard as well as the wiring for the whole unit, should be referred to constantly -both in constructing and wiring the power-park.

www.americanradiohistory.com DECEMBER, 1926 Page 785

A TOP VIEW Oh' TILE POWER-PACK FIGIIan. 1: This view of the unit shows the simple arrangement of the various instruments upon the baseboard. All of the instruments are designated by means of letters which corre- spond with the designations used in the other illustrations, in the text and in the list of parts at the head of the article. Simple "How to Build" Articles for Beginners NUMBER 17 How to Build an "A" and "B" Power -pack for Direct Current By MORRIS M. SILVER

COST OF PARTS: Not more than S40.00 HERE ARE THE PARTS THAT WERE USED IN THE LABORATORY MODEL OF THIS UNIT- Cl, C2 and C3 -Tobe paper filter conden- R3 -3500 ohm resistor;* type DEB90, to be inserted in base re- sers, 2 mfd. each: R4-3000 ohm resistor;' ceptacles T2 and T3; C4 and C5 -Tobe paper filter condensers, R5, R6 and R7 -1500 ohm resistors;' Extension cord and plug, 6 feet long; .5 mfd. each; R8 -750 ohm resistor;* Baseboard, 9% inches by 15 inches by F- Porcelain D.P. main -line fuse block; S-Hart & Hegeman 250 -volt, 10 -amp., %cinch; LI- Amerchoke, type 110; D.P. porcelain rotary snap switch; 5 Eby binding posts (marked as men- L2- Amerchoke, type 854; T1, T2 and T3- Hubbell base receptacles; tioned in text); P- Bakelite binding -post strip, 1% R9- Ward -Leonard resistor, type EB7, 2 Clearsite Fuses, 10- ampere; inches by 9% inches by 34¡-inch; to be inserted in base receptacle, Ti; 4 Wooden or rubber feet; RI and R2 -5000 ohm resistors;* R10 and Rll-Ward -Leonard resistors, *Contained in Ward- Leonard type C resistor kit.

DOWER -PACKS that will supply power -pack that is described in this that contains the new power tubes, the I both the "A" and "B" current to article was designed in the POPULAR filament current supply is not affected. radio sets, from an alternating current RADIO LABORATORIES. It is both in- The `B" voltage remains practically supply, are common enough now; but expensive and simple to build and it will constant with great changes in plate the average listener -in whose house supply both "A" and "B" current to current and with these changes the fila- current is supplied in direct current still the set straight from the DC lighting ment current and voltage are not al- has to be satisfied to plug along with lines. tered. batteries. Even with the heavy plate- current The schematic diagram, shown in To fill this very definite need the DC drain of a superheterodyne, or of a set (Continued on page 824)

www.americanradiohistory.com Pa;r 786 POPULAR RADIO

From a photograph male for POPULAR RADIO A NEW RECEIVER THAT IS COMPLETELY SELF -CONTAINED The compartment behind the closed doors at the bottom of the cabinet provides space for all of the batteries; the loudspeaker is concealed behind the grill at the top of the cabinet, and the loop is concealed in the door which occupies the entire left end of the cabinet.

INSIDE INFORMATION ON New Radio Receivers By S. GORDON TAYLOR Fourth Installment

THE MODEL SC HOLSTER; THE FERGUSON MODEL 10; THE CLEARTONE MODEL 110 The data incorporated in these critical surveys of sets that are only recently made available to broadcast listeners (or which will soon be available) is obtained at first hand by the technical staff of this magazine, largely from tests in the POPULAR RADIO Laboratory itself. The receivers already described in this series include the Radiola No. 28; the Fada "8" the Stromberg- Carlson "Treasure Chest;" the Bosch "Amborada;" the Grebe "Synchrophase;" the Freed - Eiseman "800;" the Crosley "5 -50;" the Murad "Super-Six" and the Freshman Console "6- F -1I." The Model 8C Kolster Receiver NE feature of the Model 8C Below the grill is a door which drops test or charge the storage battery or "Kolster" receiver which com- down to a position at right angles to the to replace the `B" batteries. mends itself to the average broadcast front of the cabinet; the operating con- One end of the cabinet is in the form listener is that it is completely self con- trols and tuning scale are then exposed of a door and in this door the loop tained. The cabinet is of the console to view and the receiver is ready for antenna is completely concealed. In- type and is of brown mahogany; all of operation. When the receiver is not in stead of being hinged at one side the the large surfaces are a soft brown tone use, or after a station has been tuned door is pivoted at top and bottom so and are finished in a paneled effect with in, this door may be closed or left open, that it may be revolved in a horizontal border inserts of black. as desired. plane. The purpose of this arrange- In front of the cabinet is a grill which Immediately below this door are a ment is to permit the edge of the loop extends across the front and just below pair of doors that open outward to to be pointed in the direction of the the top of the cabinet; this grill conceals provide access to the battery compart- station that is received to take advan- the cone -type loudspeaker from view ment. These doors remain closed at all tage of the directional properties of the but it does not interfere with the pro- times, of course, except at the rare in- loop for the best reception. In the case jection of sound. tervals when it becomes necessary to (Continued on page 794)

www.americanradiohistory.com Page 787 DECEMBER, 1926 The New Ferguson Model 10 Receiver ASTUDY of the Ferguson Model Ten receiver gives evidence that careful consideration in the design of the receiver has been paid to all of the features which go to make up a first class receiver- attractive appearance, ease of control, reasonable price, sensi- tivity,,.,selectivity, volume and tone qualit)ii. To the latter has perhaps been given most attention. In gt rat appearance the receiver is attractiltè, due to the excellent quality of the. _ dabinet work and to the soft brown tones in which the cabinet is finished. The cabinet is of walnut with a front panel of the same material; the coloring is uniform throughout, except for the edges of the cover, which are finished in a darker brown than the rest. No attempt has been made to break up the larger surfaces with borders or with contrasting colors and there is no necessity for such because the receiv- er is so small in size that the largest surfaces are not sufficiently large as to require such treatment. The receiver will fit into any home surroundings inconspicuously; as it is small in size and is happily lacking in conspicuous adornment. It may be mounted on any small table, or a small battery cabinet stand will serve as a mounting for the receiver and at From a photograph made for POPULAR RADIO the same time conceal all of the bat- A COMPACT TYPE OF RECEIVER TO SET ON A TABLE teries from view. This new Ferguson model strikes a keynote of simplicity -both in ap- The front panel is plain except for pearance and in operation. It takes up little space and may be mounted on any small table -or on a special battery cabinet as shown in this the three control knobs which project illustration. through bronze escutcheon plates. The larger center plate also contains a win- mum response on a low wave broadcast- ing device to obtain the best volume. dow through which the calibrated tun- ing station and the receiver is then The receiver is turned on and off in ing scale is visible. The knob on this tuned to a high wave station, a slight the usual manner by a small push -pull plate is the wavelength tuning control readjustment of the sensitivity knob switch operated by a small knob just with which practically all tuning is ac- will be necessary. This applies only in beneath the main tuning knob. complished; the calibrated scale behind the case of distant stations which call The sensitivity of the receiver is re- the window moves as this knob is ro- for extreme sensitivity if they are to be markable, considering the fact that only tated and shows the wavelength to brought in at all. two stages of tuned radio -frequency am- which the receiver has been adjusted On local stations there is no necessity plification are used. Operating the re- by means of this knob. For this purpose for readjusting this sensitivity knob, ceiver in New York City, from twenty the scale is calibrated directly in wave- once it has been adjusted for best re- to thirty stations may be heard by sim- lengths. Thus if it is desired to tune sponse from any one station. ply turning the main tuning control in a station of known wavelength it is The volume control in the lower left rapidly from one end of its range to the necessary merely to turn this tuning hand corner of the panel permits the other. By turning this control slowly knob until the desired wavelength is in- operator of the receiver to vary the an even larger number of stations may dicated on the scale. volume to suit his particular taste. It be heard, without once varying the The "sensitivity" control, at the provides absolute control of volume from setting of the "selectivity" knob. Dur- lower right hand corner of the panel maximum to zero. ing the early evening of September 28, is an auxiliary tuning control pro- These three knobs accomplish tuning with a heavy rain falling, a number of vided for the purpose of adapting and control of the receiver in a simple midwestern stations were brought in the values of the first tuned circuit to and natural way. Most people are in- with ample loudspeaker volume and the characteristics of the antenna used. terested only in reception from local and there was every indication that under In many cases it will be found that once semi- distant stations; for these the re- favorable weather conditions the receiv- this knob has been adjusted for maxi- ceiver is a real single-control outfit, in- er would be capable of covering the entire mum sensitivity on one station it will asmuch as all tuning is accomplished United States without difficulty. provide maximum sensitivity through- by means of the main wavelength tuning The selectivity of the receiver fur- out the entire broadcasting waveband knob. For the DX fan it will sometimes nishes another surprise. For instance, a without further adjustment. In other be necessary to resort to the use of the Chicago station was tuned in on 370 cases, if this knob is adjusted for maxi- "sensitivity" knob as an auxiliary tun- (Continued on page 790)

www.americanradiohistory.com Page 788 DECEMBER, 1926 the UX-213 full wave rectifier tube is placed in the socket provided in the power supply unit; the antenna, ground and loudspeaker are then connected to the terminals provided inside of the cabinet and the cord provided with the receiver is plugged into a convenient lamp socket. After that it is only necessary to turn on the switch provided on the front panel and the receiver is "ready to go." A single knob is provided at the left hand end of the panel to control the power supply unit; once this has been adjusted, it requires no further atten- tion unless the voltage of the alternating current house lighting lines changes. By means of this knob the power supply unit may be adapted to the particular line voltage obtaining in any home. Un- fortunately the so- called "110 -volt" light supply may be anywhere from 110 to 120 volts actually, depending on the location of the installation in relation to the generating or transformer sta- tions of the power company. The "off- on" switch provided just below this knob cuts the entire receiver off the light lines so there is no necessity for removing the plug from the line. The receiver uses five tubes which provides two stages of tuned radio-fre- quency amplification, detector and two stages of transformer -coupled, audio- frequency amplification. The antenna THIS SET OPERATES WITHOUT BATTERIES circuit is tuned by a variable condenser, To put this receiver in operation an electric light socket, an antenna operated by one of the tuning controls and a loudspeaker are the only external accessories required. on the front panel. The two radio-fre- quency stages are tuned by a tandem The Cleartone Model 110, AC Operated Receiver condenser which is operated by the second tuning control on the panel. BROADCAST listeners have long All that is required is a small transformer Thus the three tuned stages are actually been on the watch for a receiver to step the 110 volt house supply down tuned by two controls. An incidental which could be operated from the alter- to the proper operating voltage for these control is also provided to keep the two nating current house lighting lines. This tubes. Even this transformer has been circuits, tuned by the tandem condenser, desire has been gratified in a number of niade a part of the larger transformer in balance. This control is useful when receivers brought out within the past which provides the higher voltages for maximum sensitiveness is required, as few months, but the majority of these the plate supply of the Cleartone re- when tuning in distant stations. made use of external power supply ceiver so practically no space is required At the right hand end of the panel units. In other words a separate bat- for the filament supply apparatus. another knob is provided to regulate tery cabinet was still required to house The power supply unit in this re- the volume. the power supply units. ceiver consists of a rectifier tube, step- Provision is also made to operate The new Cleartone Model 110 re- up transformer and filter. This supplies the receiver with batteries. This is a ceiver does away with the necessity for direct current at the high voltages re- thoughtful provision, especially for all this by including the power supply quired for the plate supply and alternat- those who may desire to take the re- equipment in the receiver cabinet. And ing current at the low voltage required ceiver to camp or to the country where this is accomplished without making by the tube filaments. AC lighting current is not available. A the receiver any larger than many of In designing the receiver and the battery rheostat and battery switch the other table mounting type of re- power supply equipment, special care are provided on the panel for use at ceivers. The complete power supply was required in eliminating the possibil- such times. equipment occupies a space only five ity of a hum, due to the close proximity The cabinet is of neat appearance inches wide at one end of the receiver of the power supply equipment to the and is finished in a deep brown mahog- cabinet. receiver circuit. The designers have any. The composition front panel and The compact size of the power supply been entirely successful in accomplish- the control knobs which are mounted equipment is explained by the fact that ing this however, as there is no trace of on it all match the cabinet in coloring, this receiver uses vacuum tubes with hum or other noise from the supply and the panel slopes back sufficiently to filaments which are lighted by alternat- source or supply equipment. permit the tuning controls and calibra- ing current. Storage batteries, trickle To put the Model 110 receiver into ted tuning scales to be readily seen chargers and chokes are therefore elim- operation the five McCullough vacuum without crouching in front of the re- inated from the filament supply circuit. tubes are inserted in their sockets and (Continued on page 792)

www.americanradiohistory.com Page ,Ill apparatus advertised in this magazine has been tested and approved by POPULAR Rio LABORATORY 789 I actual reproduction possible?

it is common to hear -with the exception of a number of the ALTHOUGH who such claims as "Perfect Reproduc- makers of the more expensive sets tion," "Absolute Perfection," "The have a smaller production, and who were Living Artist Brought Right into your able to incorporate Truphonic amplifica- Home" -in spite of these claims scien- tion into their instruments. tists have never boasted absolute perfec- But for radio listeners and lovers of tion in radio reproduction. fine music who want this most nearly Let us look at the facts. actual of all reproduction now and the Truphonic Power station the music immediately, At the broadcasting Amplifier is provided in the sim- instance, is changed into of the violin, for ple, compact form shown below - a radio wave, and is broadcast. It is then attachment, without set and changed for instant detected in your radio and with no change whatever electric wave carrying tools, once more into an in your present radio set. the impulses of the music. This electric wave emerges from the detector tube not Whether you bought or made altogether perfect. However, it is so your set this year, last year or five nearly perfect that radio science has years ago, the Truphonic will give from the broadcasting you finer reproduction than you turned its attention of and detecting phases of reproduction to can get in any other way -regardless the audio amplifying of the detector tube how much you can afford to spend. output. The Truphonic Power Amplifier oper- by good amplification has ates directly from the detector output. Reproduction set are become the most important consideration No transformers now in the of radio. The amplifying trans- utilized. This pure detector music in in the art con- formers that were used in radio sets last every note, tone, and shade and in year are definitely a thing of the past. siderably greater volume, is so beauti- every set manufacturer has im- fully and faithfully reproduced that you Almost it is proved upon them. Some have adapted will find it as difficult to describe as resistance coupling, others large size for us to attempt to describe it to you. transformers, and some electric light socket power amplification. The Truphonic with Power Tubes Although these methods of amplifica- Besides the fundamentally great im- tion are an improvement, they do not and provement in reproduction that the Tru- cannot give perfect reproduction, nor do phonic brings to radio in such a conve- close to perfection as has niently applied form, there is the added they come as want now been made possible by the recently advantage that for those who announced new principle of audio ampli- extreme volume without overloading the fication. last stage tube, the necessary extra B and C battery connections for the use of power The New Amplification tubes are provided for in the attachment. cord. An entirely new system of amplifica- known as Truphonic has been de- We have tried in this space to give you some tion idea of what you may expect from this new principle veloped. This system more nearly ap- of audio reproduction that has come to radio. We proaches actuality than any other yet realize that we have made some strong claims for Scientific laboratory tests and Truphonic amplification but we have made no devised. claim that you will not find more than backed up tests before both the musically trained when you have tried the Truphonic yourself. r- and the musically untrained ear establish We urge you to get the Truphonic sow, -so that this fact beyond question. you may begin immediately to have an altogether different kind of enjoyment of the splendid pro- Unfortunately the Truphonic system grammes that are coming to you over the air was not developed in time to be generally Your dealer has the Truphonic, or will get it used in this fall's production of radio sets for you. ALDEN MANUFACTURING CO. Dept. 317 C- Springfield, Mass.

11 RU?IIcDNC Not Resistance Coupled Power Amplifier

www.americanradiohistory.com Page 790 All apparatus advertised in this magasine has been tested and approved by POPULAR RADIO LABORATORY Why the The New Ferguson Model 10 Receiver (Continued from page 787) meters without interference from a the Ferguson "Ten" certainly seems to local New York City station operating bear out the claims. on 374 meters. Then just above this A heavy wood chassis provides the WGY was tuned in, again without in- foundation on which the receiver is as- ÑA-ALO terference from the station on 374 sembled and wired. The cabinet and meters. There was no difficulty at all front panel simply serve as a housing in tuning in Washington on 469 meters for this assembly. Shielding is provided with the local stations WJZ and WEAF to reduce interstage coupling in the Silencer Socket going full blast; and in pulling in radio-frequency amplifier and also to Philadelphia, on 509 meters and right provide protection for the instruments. between WEAF and WNYC. This is This shielding takes a somewhat differ- excellent is essential selectivity, as one will realize ent form from the "cans" ordinarily used who is familiar with reception conditions for this purpose but is apparently equal- in to clean -cut New York, which is a nest of high ly effective. Instead of completely in- power stations. closing the individual circuits in sealed It is well to mention here that this metal boxes the manufacturer of this reception test was made with an antenna approxi- receiver has simply placed large copper mately 100 feet in length -long enough partitions between the circuits. to make selectivity rather doubtful on The circuit makes use of two stages In many cases many receivers. To make sure of ample good clean of radio -frequency amplification, detec- -cut selectivity, regardless of radio reception is the length of tor and three stages of audio-frequency decidedly hamp- the antenna used with the receiver, the amplification. This requires the use of ered manufacturers by the dis- have included a switch six vacuum tubes, five of which are of turbing micro - inside of the receiver which provides the 201 -a type. The sixth is a 112 type phonic noises with- No. 481XS four degrees of in the selectivity. Thus when power tube and is used in the last stage radio tubes -particularly the de- the tector tube. These disturbing noises are receiver is once installed in the home of audio-frequency amplification. caused by shocks and jars -very often this switch can be set on the point A three- section gang condenser is used slight -which come various from vibra- which provides the desired selectivity to tune the antenna circuit and the tions such as the vibration of the loud and the speaker, owner may be assured of good circuits of the two radio-frequency tapping the radio set itself, walk- reception ing in the room or even street traffic. without interference, regard- stages simultaneously. The common These vibrations cause the grid and the less of the size of his antenna. shaft on which the rotors of these three plate of the tube to vibrate slightly in Plenty of volume of reproduction is condensers are respect to one another. mounted also serves as provided through the use of three the mounting for a coupling coil in one "Float" your tubes! stages of audio-frequency amplification, of the radio-frequency circuits. By this using a power tube in In order the last stage. A means the coupling is automatically to shield the tube against these new method shocks the Alden Silencer Socket has been of coupling is used which is varied with the tuning condensers. This designed. With this socket the tube is claimed to combine the good qualities is one of the schemes used to obtain the "cushioned" and "floated," absorbing all of impedence-coupled amplification with increased efficiency of the radio-fre- shocks in all directions -sidewise, up, those of transformer-coupled down and pivotally. The marvellously balanced amplifica- quency amplification that is incorpor- phosphor bronze springs which accomplish the tion. The scheme as exemplified in ated as the "cushioning," form also the contacts for the tube heart of this receiver. and for the outside connections. This important point, among others, is fully covered by patents. Contacta press firmly, strongly and flatly against the full length of the tube prongs. Special phosphor bronze, triple locked, contacts are held in constant tension insuring permanent quiet action. Solder lugs are provided for making connection either above or below the base panel. Or the lugs can be removed and the binding posts used. Round edge permits of mounting in any direction, and makes for a neat mounting on the base panel. The Silencer Socket (for UV zorA and all UX tubes) is a markedly superior socket which large production enables us to sell for sac. At all dealers. Other Na -Ald Sockets

The Na -Ald No. 481X socket is the popular priced universal socket for all UV zorA and all UX tubes. This socket is in great demand for am- plifying tubes. The price is 35c. The Na -Ald De Luxe Socket is designed for heavy duty service with the bis, high voltage, ex- pensive tubes. Triple lamination, dual -wire con- tacts will carry the heavy current used. The tube prongs and socket con- tacts can be self cleaned simply by a half turn rotation of the tube in the socket. Alden pro- cessed moulding assures the necessary mechanical and electrical strength. The De Luxe Socket is ?Sc. at your dealer's. No. 400 THE RECEIVER UNIT OF THE SET SHOWN ON PAGE 787 ALDEN MANUFACTURING CO. This shows a bottom view of the chassis. All of the instruments are mounted on a heavy wood foundation and partial shielding of the radio - Dept. 317C. Springfield, Maas. frequency circuits is provided by the large metal box in the center.

www.americanradiohistory.com Ill apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 791 "MEN! Here's FREE! the dope'you've been looking for-

HOW TO GET INTO THE RADIO BUSINESS"

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www.americanradiohistory.com Page 792 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY The model "Ten" receiver may be biasing voltages that are necessary. Now you can used with batteries, or may be operated Any sort of an antenna may be used from the house lighting lines through with this receiver. For best all around suitable power supply units. If the results an outdoor antenna is to be rec- build a re ally latter is used, any of the standard makes ommended, and preferably one which is will be suitable. A six -volt supply is re- is not more than 100 feet in length in- quired for the filaments and must be cluding the lead -in. Such an antenna professional capable of delivering 1% amperes. For provides plenty of "pick -up" whereas a the plate supply a voltage of 135 is re- longer antenna may tend to overload the quired, at a drain of up to 30 milli- detector tube. An indoor antenna will amperes. The current drain of the re- provide all the signal strength needed radio set. ceiver is not actually as high as this on stations up to 100 miles or more. but this requirement for the supply To simplify the operation of connect- unit allows a margin of safety. ing the receiver to the batteries, a cable If batteries are used a six -volt storage comes with the receiver and has the vari- rtft battery is required and three "B" bat- ous wires plainly tagged; it is therefore tery blocks of 45 -volts each. The necessary only to connect these wires to manufacturer also recommends an ad- the battery terminals indicated by the ditional 45 -volt block for the detector metal tags. The other ends of the cabled plate supply, using the other three connecting wires are permanently con- blocks on the amplifier tubes only. This nected inside of the receiver. arrangement is desirable but not essen- There is little chance of even the tial. Two small 4M-volt blocks of "C" rankest novice going wrong in connect- TO BUILD a really professional looking battery are also required for, the grid ing up this receiver. and efficiently operating radio set here are two new and Important construction units. The Cleartone Model 110, AC- operated Receiver The Truphonic Power Amplifier, more fully described on another page of this issue, (Continued from page 788) provides by far the finest type of audio ampli- fication so far developed. For the set builder ceiver. The two major tuning controls 900 miles distant, on the loudspeaker; the Truphonic may be had in a Catacomb are set at the lower edges of ornamental the closer stations came in with great Assembly which gives you a complete unit At edges volume too much for use in the containing the following: Complete Truphonic composition plates. the upper -far audio amplifying system including an output of these plates, windows are provided home. But the volume control cut the unit to protect the speaker from burning out behind which the calibrated tuning volume down to suitable proportions. and demagnetization, sockets with attached scales rotate. The quality of reception was better leads for the tuning and detector end of the set. This receiver may be used with than that usually obtained from re- The illustration shows how neatly this either an indoor antenna, or with an ceivers which do not make use of a Catacomb Assembly houses all of these ele- is sufficiently power amplifier tube in the last audio ments and how compactly it fits behind the outdoor installation. It tuning control. No holes to drill, no apparatus sensitive to operate a loudspeaker on stage. Evidently the McCullogh tubes to mount. Short, direct leads with a minimum stations up to 20 miles distant when are capable of handling considerable of soldered connections. This unit may be using a two foot wire for the antenna; power without overloading; in any arranged in a hundred dif- ferent ways to match all the it is therefore evident that an indoor event the quality is good even when requirements of every cir- cuit and set design. A six antenna of 30 to 40 feet in length will the volume control is turned up to foot battery cable is in- provide plenty of volume for all normal provide great volume. cluded, in which provision is made for the extra B bat- reception purposes. For reception from On the whole this Cleartone receiver teries and C batteries for is is for who wish the use of power tubes. great distances an outdoor antenna an excellent one those The Truphonic Assem- is to be preferred, of course. Such an to enjoy radio without any effort other bly is provided in two antenna should not be more than about than that required to turn on the models, one for 6 tubes, $2o,and one for 7 tube:, $: , 75 feet in length, if the receiver is located switch and tune in the stations. No in a city close to the broadcasting sta- thought or attention is required by the Localized tions; for rural locations the antenna power supply equipment and there is Control may be longer than this if desired. nothing to wear out except the tubes - NPALf Tuning Unit Under reception conditions which can and their life is so long as to give little be considered only fair, this receiver cause for worry so far as expense is The Na -Ald Localized Control (Trade Mark Reg. U. S. Pat. Off.) Tuning Unit (Quadruple model shown) is a boon brought in a number of stations up to concerned. to the set builder-a great advance in multiple condenser construction. It can be used with any form of radio fre- quency coils, and gives you simple control under the finger tips of one hand, enabling you to tune all the con- densers at once, or to tune each one separately and dis- tinctly.

These advanced Na -AId Localized Control Tuning Units are provided in several models (all are of .00037s capacity unless otherwise indicated). Double $8 Double (.0005) Seo, Triple Seo, Quadruple, Sic, Double with tickler control Seo. With each unit is included the hand- some panel plate shown above. Your dealer has these Na -Ald advanced construction units, or can get them for you. ALTERNATING CURRENT HEATS THE CATHODES The power unit to supply the proper operating voltages from the house lighting lines is shown at the right. This unit supplies low -voltage ALDEN MANUFACTURING CO. AC for the heaters and high -voltage direct current for the plate supply Dept. 317C Springfield, Mass. thus eliminating all batteries.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 793

A $20,000,000 IDEA

r-g-I EN YEARS ago Charles Grover Smith began .Ji. the intensive study of the possibilities of handling electrical power by gaseous conduc- tion. With the resources of the Raytheon Re- search Organization behind him, he produced the Raytheon Rectifier, giving for the first time "Approved by Raytheon" full wave rectification with simplicity, long life, and absolute reliability, and making possible in Manufacturers of Complete the one year since its introduction, a business in &Power Units, Raytheon -equipped: Raytheon -equipped B -Power units of approxi- The Acme Apparatus Co., Cambridge, Mass. mately $20,000,000. All- American Radio Corp., Chicago, Ill. Romance of Raytheon Amer. Bosch Mag. Corp.. Spring'd, Mass. Raytheon has many ideas. For their development By DONALD WILBsLN Chicago, Ill. American Electric Co., Raytheon maintains a Research Organization BETWEEN the time Mr. Smith set Apco Mfg. Co., Providence, R. I. to work on his research, and the Cornell Elec. Mfg. Co., L. I. City, N. Y. housed in a separate building, and with a staff time that the Raytheon Rectifier was produced there were many hours. Electrical Research Labs., Inc., Chicago headed by such men as Mr. Smith, Dr. Vannevar days, and months of dreams, discour- General Radio Co., Cambridge, Mass. Bush of M. I. T., Monsieur Andre of the La agement. thrilling discovery. and Pa- Grigsby- Grunow -I -finds Co., Chicago, I11. tience. It makes good reading. For copper as being King Elec. Mfg. Co., Buffalo, N. Y. Radio Technique of Paris, Mr. J. A. Spencer, in- example, we think of an excellent conductor, yet Mr. Smith Indiana Kokomo Electric Co., Kokomo. ventor of the Million Dollar Thermostat, and found that he could pass seventy times Mayolian Radio Corp., Bronx, N. Y. many others. The equipment at their disposal as much current through a column of The Modern Elec. Mfg. Co., Toledo, O. gas as through a copper wire of the same diameter. Pathe Phonograph Co., Brooklyn, N. Y. cannot be duplicated anywhere. It is little are interested to know more Sparks- Withington Co., Jackson, Mich. close to radio power prob- If you wonder that those about the years of research resulting The Sterling Mfg. Co., Cleveland, Ohio lems look to Raytheon for their most effective in the development of the Raytheon Storad Mfg. Co., Cleveland, Ohio Rectifier, we shall be glad to mail you words J. S. Timmons, Inc., Germantown, Phila. solution. a leaflet telling the story in the Mr. Donald Wilhelm, author of Valley Electric Co., St. Louis, Mo. of COMPANY "The Story of Steel," "The Story of The Webster Co., Chicago, Ill. RAYTHEON MANUFACTURING Wrought Iron," and many other pub- Zenith Radio Corp.. Chicago, !IL CAMBRIDGE. MASSACHUSETTS lications. Drop us a line. RAYTHEON -- rectifier

www.americanradiohistory.com .Ill apparatus ad.vrtised in this magazine has been tested and approved by POPULAR RADIO LABORATORY The Model 8C Kolster Receiver NA -A1D (Continued from page 786) Adapters for all tube and socket combinations Na -Ald Adapters are indispensable to the set owner and set builder who wants a simple and instantaneous means of adapting any particular type of tube to the particular type of socket that is used in his set. For instance, if your set is now equipped with standard 2orA sockets, and you want to use the small UV tog type tube, simply insert the Na -AId Ada No 429 No. 41971 into the IotA socket anpterd insert the too tube into the adapter. The various types of Na -Aid Adapters are given below. Specify them for best results: For adapting small UX too and UX tao tubes to UV zotA sockets, use Na -Aid Adapter No. 419X. Price 35c. No 421X To bring up to date and decidedly improve the Radiola III and ILIA and similar sets employing WD II Tubes, use Na -Md Adapter No. 42iX Price 75c. For adapting UV too tubes to No. 429 standard zoiA sockets use the Na -Aid No. 429 Adapter. Price 75e. To adapt all UX tubes and UV 2oIA tubes to UV tog sockets use THIS RUGGED CONSTRUCTION ASSURES Na -Aid Adapter No. 9gg. Price PERMANENCY st.00. OF ALIGNMENT Na -Aid Adapters are sold by all This receiver unit good example good radio stores and carry the is a of the care exercised in making all Na -Aid unconditional guarantee. parts rigid enough to withstand the hard knocks of shipping, without endangering the careful adjustments of circuit values made at the ALDEN MANUFACTURING CO. factory. Note the heavy cast frame in which the condensers are supported. Dept. 3.7c SPRINGFIELD, MASS. of reception from local stations this the "station selector" this right hand door need not be opened at all. knob is adjusted to provide just the In addition to the 8C model four other desired degree of volume. A small models of the Kolster receiver are avail- lever just below the volume control ° 0111.- able. Two are for table mounting and knob serves as a battery cut-off switch °t.ttt ... there are two other smaller console to turn the receiver on or off. models. Three of these five are eight If an outdoor 1/4Po, or indoor antenna and tube receivers and in these three the ground connections are used in place of receiver units are identical, the only the loop antenna it is necessary to pro- difference lying in the style of the cab- vide some means to adapt the receiver inet and in the equipment. The other to the particular size of antenna in use. two receivers use only six tubes and are This adjustment is made by means of intended for use with an outdoor or a small lever found just below the an- NOTHING ELSE indoor antenna instead of with a loop. tenna tuning, or "sensitivity" knob. The operation of the 8C Receiver is This lever may be adjusted to any one of LIKE IT! decidedly simple. There are three con- three positions. HERE is a simple radio con- Position No. I pro- trol -the Centralab Modu. trol knobs in all. The central knob, vides maximum selectivity while posi- Plug -that is unique even in a called the "station selector," tunes the tion No. 3 provides maximum sensi- field where phenomenal de- four tuned circuits of the receiver tivity. Position No. 2 strikes a happy velopments are common. simultaneously and is the main wave- medium and will be the position at Provides smooth, noiseless con- length tuning control of the receiver. which trol of tone and volume direct this lever will usually be left when at the plug with the set oper- Just above this knob is a revolving scale using an antenna of average size. When ating at full efficiency. With- which is calibrated directly in wave- the loop antenna is used this lever is out adjusting tuning dials or lengths and which shows the wave- automatically cut out of the circuit. other controls, you can regu- length to which the receiver is tuned. The receiver late volume from a whisper to unit is complete in itself maximum simply by turning This scale is lighted from within by a and is shown on pages 794 and 796. It the little knob on this plug. small lamp that also serves as a pilot is entirely inclosed in an aluminum case, Reduces static interference- light inasmuch as it is lighted only part of which has been removed in the clarifies tone. Replaces the or- when the receiver is turned on. To the dinary loud -speaker plug. views shown in the illustrations, to left of the main tuning knob is the show $2.50 at your dealer's, or mailed direct on the inner construction. This receipt of price. antenna tuning control. This is called aluminum frame and case serves to CENTRAL RADIO LABORATORIES the "sensitivity" control because the shield the receiver from the loop an- 17 Keefe Ave.. Milwaukee, Wisconsin receiver is always most sensitive when tenna, thus preventing undesirable in- Manufacturers of variable resistances the antenna, as well as the other four teraction; for all radio circuits it also provides an absolutely tuned circuits are tuned to the exact rigid foundation for the inner assembly. wavelength of the transmitting station Care has been taken in every detail The third knob controls the volume. of the construction work to make every- When a station has been tuned in with thing secure so that the assembly, the

www.americanradiohistory.com All apttaratus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 795 CH RATIO

THE CRUISER -5 Tubes -$100 The new Bosch Radio models are finer, more powerful, easier to operate, more beautifully incased. Built to please the radio wise purchaser, Bosch Radio upholds the judgment of those considered experts. Completely armored and shielded, the five tube Cruiser sets a new standard in performance and tuning simplicity for receivers up to double its price. It has unified control, a single station selector for most tuning and two dial advantages for "Cruising the Air." The Amborada is an armored and shielded seven tube receiver, built on a steel cnassis for rigidity and long life. Its great power and unusual ability will be a revelation to even seasoned radio veterans. Its single station selector is graduated in wave lengths; eliminating multiplicity of dials and troublesome tuning, and its clear, tonal range is from a whisper to orchestra volume. This receiver is incased in a low, handsome, early American period cabinet, with ample room for all batteries, charger and power units. Bosch Radio cffers a wide selection -five, six and seven tube receivers, two cone type reproducers, the famous NoBattry "B" Power Unit and other equipment. Hear Bosch Radio at your Bosch Radio Dealer. We will send you his name upon request. AMERICAN BOSCH MAGNETO CORPORATION SPRINGFIELD, MASS. Branch's: New York Chicago Detroit San Francisco Ymufaetveed adder tevt sD Ilcstions or the Amerlcs Bosch hl THE AMBORADA Tubes -$310 laceo..d .1.e .°,der .eolío Co ntloe -7 .vd t on. of the Redly Freuneoer toLabontore., toe. All prices slightly higher Colorado, wit and In Canada

www.americanradiohistory.com Page 796 All apparatus advertised in th's magazine has been tested and approved by POPULAR RADIO LABORATORY wiring and the delicate electrical bal- This might seem rather unfair to the ance of the receiver will remain un- manufacturer if it were not for the fact or affected by shipment. These precau- that the company's engineer who was tions make it possible to balance the cooperating in the tests suggested that circuits exactly before the receiver leaves sub -normal conditions be selected. Power ibes the factory, with assurance to both the The receiver used in the tests was a manufacturer and the purchaser that standard, Model 8C Receiver which had no further attention will be needed in previously been purchased from the You don't the way of adjustment. regular stock of a local dealer. It was have The circuit that is employed was de- located in the basement of an apart- to change signed by Dr. Kolster who is well -known ment house in New York City and was your set wiring as the inventor of the radio compass, entirely below the level of the surround- one of the most important aids to marine ing ground. While using the loop sta- Na-Ald Connectoralds are particularly In demand for the new power tubes, l'X 1, 1, l'X 112 and UX 120. navigation ever developed. tions were tuned in up to 800 miles dis- which greatly Increase the undistorted volume that a set will deliver. There Is a Connectorald for every type of The design of the circuit is such that tant and every one was received on the tube and set. Each type of Connectorald Is equipped with cables to connect to the extra B and C batteries, it is absolutely free from oscillation be- loudspeaker with ample volume to be necessary for power tubes. This makes It unnecessaryy to change the wiring of a set In any way. Except where cause feedback has been overcome and comfortably audible anywhere in the noted, Connectoralds do not raine the tube h, the socket. interaction between circuits has been room. Twenty-five stations were "pulled Na-Aid Connectoralds reduced to a minimum, without the in" under these conditions in a little eo Trade Mark Reg. U.S. Pet. Odic, necessity for elaborate interstage shield- over an hour. This speaks most highly For UX 171 and UX 112 Tubes, Na -Aid 112 Connectoralds are recommended for maximum of the sensitivity and distance getting volume with storage battery sets. These tubes ing. will deliver without distortion several times the instruments of the receiver. IE volume of the regular 201A. Price $1.50. For the most part the ability For UX 120 Tubes In UV 201A sockets, the used in the receiver unit are of special Selectivity was excellent in spite of Na-Ald No. 120 Connectorald should be used. No.112 To convert a storage battery set to dry batteries are in this fact that the receiver was located with ample loud speaker volume. use a UX 120 design and manufactured the tube In the last audio stage with the 120 Con - company's own plant. in close proximity to a number of power- nectorald and l'X 199 tubes with 4I9X Adapters in the other sockets. Price $1.25. most owners of one of ful local stations. This was to be ex- For the UX Go Tube in UV 199 sockets, Undoubtedly ample loud speaker volume without distortion Is will to use the pected however, in view of the fact that obtainable from any set equipped for UV 199 these receivers prefer tubes by means of the UX 120 or equivalent loop-antenna which is incorporated in there are five tuned circuits in the No.120 tube, with the Na -Aid No. 920 Connectorald. The tube Is raised slightly, but provides for its the cabinet. This is more convenient receiver. use In most sets with limited headroom. Price $1.25. than installing an outdoor antenna and Perhaps the outstanding features of For UX 120 tubs ln the UV 199 sockets of step the Radiale Superheterodyne estable, will provide ample volume, quality, the reception was the fine tone quality Na . and and Radlole Super VIII. Thesee excellent Superheterodyne. will deliver ample volume sensitivity and selectivity to meet the with great volume -outstanding be- for loud speaker operation when equipped with the I7X 120 used with the Na-Ald No. 420 demands of almost any broadcast en- cause they are of more interest to the Connectorald. Price S1.25. thusiast. For the absolute maximum average receiver owner than is extreme ALDEN MFG. CO. in sensitivity an outdoor antenna is to sensitivity. The tonal reproduction was Dept. 317C NA-ALO N. aro Springfield, Mau. be preferred, of course. It need not be life -like and of a purity unmarred by large, however; thirty or forty feet is distortion in any form. The Volume sufficient. An indoor antenna of the was tremendous. same length may be used if preferred, An idea of the volume of output of this YOUR OWN and will provide greater sensitivity than receiver may perhaps best be conveyed the loop. by the statement that, even under the In the working test of this receiver, adverse conditions described above, it BUSINESS conducted by the author, extremely was necessary to cut down the volume unfavorable conditions were selected in on reception from stations as much as Without Capital order to make the test a difficult one. 500 miles away.

Right now, there is an opportunity in your locality to profitably devote your spare time or all your time to a pleasant, easy and profitable business -one that does not require any training or capital. The publishers of POPULAR RADIO offer you an opportunity to become their local representative to take care of expiring sub- scriptions and new subscriptions for PoP- rlwR RADIO and three other popular maga- zines that they publish.

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Send me full particulars regarding your salary and commission offer to local representatives.

Name

Address NOTE TIIE COMPLETE EXTERNAL SHIELDING The strong metal box which completely encloses the receiver (one sec- tion has been removed) serves the double purpose of protecting the instruments and of shielding the receiver from interaction with the

r loop antenna.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 797

F. O. B. Chicago. Orarke Senior P$ 13250 5 Tube Model complete withLoud Speaker and all accessories. Also built in a 7 Tube Model

F. O. B. Chicago. Ozarks Iunior 5 Many Are Being Fooled in Radio $100 Tube Model complete with builtin By Believing Service Unnecessary speaker and all accessories. ANY radio, no matter what its price may be, nor who makes it, will only be as satisfactory as the trained service behind it. In buying a radio there are a number of When anyone tells you that radio service is important things to consider- not necessary, think it over, your own good APPEARANCE sense will tell you differently. You have a - right to receive from your radio consistent TONE - operation, night after night and year after VOLUME- year-the right service by a service man who DISTANCE - knows how, will guarantee you that lasting EASE OF TUNING - satisfaction you are entitled to. and last but far the most important - The claim that service will not be necessary SERVICE. is the poorest type of salesmanship -it only leads to dissatisfaction later -far too often it F. O. B. Chicago. Ozarka Console Tone and Volume can very easily be de- up fact that the seller is $215 5 Tube Model, solid walnut cabinet, termined by listening. The real way to is used to cover the complete with all accessories. only in a position to deliver service. Also prove distance and ease of tuning is by oper- not built in a 7 Tube Model ating the instrument yourself, but the quality In the past, the selling of radio instruments We have a few Openings of service must be determined only by careful has depended largely on having stock on hand investigation. to deliver -in the rush to buy very few paid for the Right Men to what service could be de- Wl too often it to claim any attention W -IILE there are today 4364 Ozarka Far seems customary livered in case any little trouble came up. territory is still that radio service is unnecessary. For four some years this company has been building a fac- Today, service in radio is not only being open. We want men who believe in and demanded but people who the future of radio -men who are tired of tory trained service organization until today recognized working for who would it consists of 4364 men who know Ozarka know, go even farther and demand -service some one else -men instruments in every detail. These men have by factory trained men. like to add to their present income by de- been trained directly under Ozarka Engineers, voting their evenings to Ozarka. You would never consider letting any all At the start you can keep your present position. the men who originated and developed round mechanic repair your car -then treat Later on, after you have proven what you can do. Ozarka Instruments. your radio in exactly the same manner. then you will give us all your time because it will but the service of pay far more than your present position. You'll find it well worth your time to in- Demand not only service The man we want may not have much money vestigate this organization before you decide men who know -the day of the radio wizard but he is not broke. He has lived in his community on your radio. A trained Ozarka service man who knows all radio instruments is gone -the for some time -he has a reputation that his word is man has taken his good. He may not have made any startling success is near you -why not discuss this matter factory trained service but he has never "put over something' just to with him? place. make money. He may know nothing about radio or salesmanship but he will be successful if he is willing to study what we are willing to teach him, with- out cost. The field in radio is wide open for the trained man. The success of the 4364 Ozarks representatives proves what men can do. If you are int ed. ask fora copy of the Ozarks Plan. a 100 page book which tells a true story of how big money and a permanent business can be built in radio. It is a story of life: of why some men fail while others I fV C Q R R Q R AT E D succeed. This book has shown many men how to start making extra money immediately and within 120 W. Austin Avenue D CHICAGO. ILL. very short time establish business of their own.

www.americanradiohistory.com Page 798 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY ASK .. ANY .. RADIO .. ENGINEER The YES and NO DRAN AIJSA. -Yes, the Atwater -Kent pro- Chest Beebe plays the organ through grams will be continued this winter. WOR on Tuesday and Friday. ' My, Aiáita. Frances Alda, Lucrezia Bori, Madame you listeners who don't watch for the Schumann -Heink Frieda Hempel, Josef announcement of names cause us a lot Hofmann Albert Spalding, Maria Kurenko, of trouble. Edward Johnson, Louise Homer, Reinald Werrenrath, Margaret Matzenauer, Mary Lewis, Rosa Ponse&e and Charles Hackett HALLY. -Mary Lewis has signed up are signed for "appearance," and WEAF, with Charles Dillingham according to late WEEI, WSAI WRC, WCCO, WTAG, reports. Graham MacNamee used KSD and WWJ are to be in each hook -up. to be a music teacher before he crashed The We're going to have some Al pro- radio. s How do we get our informa- grams according to the almanac. tion? Oh, we just gossip and write hun- Crowning Adventure dreds of letters to the publicity men at z the studios. ofBurgess Radio Batteries JOSEPH B. -You evidently heard one of They Flew Over the North the General Electric short-wave experi- z Pole with Byrd mental stations operating; the G. E. Co. have fifteen experimental licenses; 2XAW, ONON May 9, history was made 2X0 2XAF, 2XAD, 2XAH, 2XI, 2XAK American history . 2XAZ, 2XAG, 2XAH, 2X1, 2XAM and .. 2XAE. They are named in order World history...undying history. of their wavelengths which run from 3 Lieut Commander Byrd, in his to 110 meters. fearless 1500 -mile flight across the top of the world, adds another z EDWARD M. B. -It was Harold A. thrilling triumph to the long, proud Loging who broadcast the Indian folk list of American achievements. songs from KOA. So you want more baritone solos! My dear fellow, Radio went along, for radio has we'd give you anything but more bari- become vital to the lives and tone singing; baritones are nearly as PERM ADAMS, JR.- Charlie Wellman success of explorers and adven- plentiful as sopranos and sopranos, if is an announcer at KFWB (Los Angeles); anyone should ask you, are nearly as here's his photo. Yes, Mary Lewis turers. Burgess Batteries went will broadcast again some time this winter; along, sharing the fate- sharing plentiful, and surely as pestiferous, as seven -year locusts. * We really ought it will probably be through the WEAF- the hardships and the glory of to give you a good bawling out. WJZ chain. Commander Byrd, the Detroit Artic Expedition, and Capt. z Donald MacMillan. BAMBO. -You want to present a loving CHARLES I.-We don't usually give the cup from the listeners of American to verses of songs heard over the radio but It is eminently significant that in these Norman Brokenshire. Sure we're you're so ingratiating that you almost glorious triumphs of American courage and American equipment where the test of men wild about the idea -crazy about it. disarmed us. and their tools was the test of the survival of We'll send you a couple of lead nickels. the fittest, that the standard produce of the ' (We wish we owned a hotel with a Burgess Battery Company were selected, thousand rooms in it and could find you ALLEN D.-August Werner of the New used and "carried on" under extreme and dead in each room.) unprecedented conditions. York Edison Hours is a Norseman; he used to sing under Riesenfeld at the BURGESS BATTERY COMPANY Rivoli, New York City. How do Gammas. SALES OPFICHS, CHICAGO HARRY L. Fern Van Bramer is the we know all of this stuff? Oh, we're just Canadian Factories and Offices: harpist who Flays with Lyon and Healy at an old gossip Niagara Falls and Winnipeg WGN. We have heard nothing about MacNamee going to WSAI; its z news to us, Wouldn't it be terrible if WEAF lost him! MABLE.-Why don't we have more Why don't we have more jazz? Dojazz?n't come to us with such a question; we'd give anyone ten years in Sing Sing for that request. Jazz is an in- dustry not an art.

MYRTLE AND MA22IE. -So you sing just like the Walton Sisters do you? Well that's no recommendation to us. i We hate baby talk in close-harmony. If you must broadcast, try WBAL, in your own town -but don't ask us to listen. A.W.-Kathleen Stewart is now only a microphone name; Miss Stewart was JUST A LISTENER.-Judge, Jr. (WJZ) married over six months back. Yes, composes most of his own stuff. He she did concert work before she joined wrote a play once called "The Brown WEAF'S staff. She lives at Pali- Derby." It was exposed to Broad- sades, N. Y, and has the living room of her way for one night only. cottage papered with applause cards.

BURGESS ELMER HAINES. Blande de Costa is the LrrrLE BEN. -We don't know who is soprano in the program of the Pro Musica RADIO BATTERIES doing the announcing at WHN' they come Society (KOA). Let's take the and go at WHN. Edward S. negr spirituals off the air? ' All Breck is the piano accompanist at WOR. right, let's. But how are we going to do it?

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 799

Contrast the clumsy dials of only two years back ... with the handsome illuminated controls MAR -CO makes today. Here is another good reason for build- ing your set yourself!

óßv dials give placeN to glowing spots of light

PICTURE a soft, subdued light vided reduces panel -drilling to in the room .. . the simple, fool -proof operation your set in the corner .o+ illustrated below. The original with glowing spots of light MAR -CO `friction- drive "-the illuminating its swiftly action that makes backlash impos- readable back panel scales. sible -has been strengthened, to this is radio at its hand- accommodate gang condensers. somest .. . The MAZDA lamp supplied runs this is the panel arrange- on your "A" battery, using only ment the type of skillful .1 ampere. The switch that con- tuning that distinguishes trols this lamp may also be used the 1927 trend in set as your filament switch the construction. lighted scales then serve as , Already, these new MAR -CO pilots. Scales read 0 to 100, or controls are specified or optional 100 to 0, as preferred. Price, equipment in a score of this sea- including template, bulb, and son's most advanced circuits. bezel, $3.50. Replacement At once, they have become the bulbs, $.20. Write today for standard in tuning control de- the booklet that illustrates 15 sign. Use them, in whatever standard makes of condensers set you build, to give the final mounted on MAR -CO back -panel Prominent touch of style, and the utmost controls. Martin -Copeland among the ad- in precision control. Company, Providence, R. I. MAR -CO controls are easy to Branch offices and representa- vanced circuit install. The steel template pro- tives in principal cities. designs which call for MAR -Co i1uminatedConlrols Controls, is the eco "LC -27" Here's how r that's ALL you drill fill you CAN'T the panel.. °' go wrong! screw Template Ur ill holes i2r1110Ve window Betel corers to panel through Template opening rough edge

www.americanradiohistory.com Pure SOO All apparatus advertised it this maeaaine has been tested and approved by POPULAR RADIO LABORATORY S. WENTwoRTn.- Broadcasting stations do not pay for the use of new, unpublished See that scren- Chosen by songs. A SeREWIORIVEL ADJUSTS AN X-L IN CROWDED EXPERTS Bio BOY.-No station that we know of PLACES XL specializes in poetry. * * N.T.C. (WHN) used to throw a poetry fit occa- ARIO GLENN H. BROWNING, Laurence M. sionally; he shattered the diaphragms of at Cockaday, Gerald M. Best and many least four microphones with "Boots" and DENSER other eminent radio designers use the "Dangerous Dan McGrew." I:sed in POPULAR It \Ultt Lynch Metallized Resistor in their ex. perimental circuits and receivers. These Improved Browning -Drake men know radio; they have laboratory HARRY M.C.-Franz Lehar wrote "The and testing equipment with which quick- Merry Widow," not Rudolf Friml ex- Hookup ly to make accurate comparisons. There cerpts from this have often been broadcast. Indorsed by leading radio authorities could be no better proof of the true merit A slight Iton obtains cor- of the Lynch Metallized Resistor than z Mode1 "N" rect tube oscillation on the endorsement of these experts. HINRY-DINK. You're getting to be a all tuned radio frequency circuits. Neutro- regular customer. * * How do you get a dyne, Roberts two tube Browning- Drake, Comprising a concentrated metallized McMurdo Silver's Knockout, etc., capacity deposit onethousandthof an inch thick job in a studio? Well, that depends upon range yf to 20- micro-micro farads. Price $1.00. upon a rigid core, sealed forever with- what you can do and how much you want for doing it. * * * If yeu can do a lot and grid clipe obtains the in a glass tube, the Lynch Metallized Model IG "withproper grid rapacity on Resistor gives conductive, non - arcing want a little, you might get a job. Cockaday circuits filter and intermediate fre- resistance remains silent, accurate! quency tuning in heterodyne and positive grid that bias in all sets. Capacity range: Model G- 1- .00002 to .0001 MFD Dealers -Write us! BELLE OF BELLPORT. -"Major" Andrew Model G -5 -.0001 to .0005 MFD White is just as he sounds over the air, Model G -10 -.0003 to .001 MFD ARTHUR H. LYNCH, Inc. "regular." * * * He lives in New York Price $1.50 Fisk Bldg., Broadway & 57th Street City and is president of a radio concern. X -L PUSH POST * * * We don't think that there is a more Push it down with your New York, N.Y. perfectly human announcer on the air - thumb, insert wire, remove pressure and wire is firmly and, as you know, we're au-fully fussy held. Releases instantly about announcers. Price 15e. Push Post Panel perma- nently marked in white on black insulating panel In box WRITER MAN.-Yours is an interesting including soldering lugs, rais- letter. * * WMCA gives a complete ing bushings and screws for financial service, following the tape mounting, etc Price, 51.50 Precision in closely each day. * Yes, there is a Manufacture great deal of room for improvement in The utmost care the best program presentation. of materials. the most skilled craftsmen make Lincoln each Lynch Metallized X -L Radio Laboratories CHICLAGO ILL. Resistor the precision. built, yet rugged little in- strument that it is. Frequent rigid inspec- tions, and sufficient aging before final test make possible our guarantee- Absolutely Noiseless Permanently Accurate Dependable! Our warranted accu- racy is 10% but through Because the fixed precision inmanufac- resistor is small ture, Lynch Metallized in size, do not Resistors avenge within underestimate its 5lú in actual production. four types vital importance. Arthur H. Lynch G. H. WHITEHEAD.-K. K. at WGR (Buffalo) are the initials of Mr. Kenneth thoroughly ex- Kickett the announcer at that studio. He was formerly a research worker in the plained in a fully Eastman Kodak Laboratories at Roches- illustrated FIXED RESISTOR ter. booklet

9r"x 1 2" . This book- HARRY L.B. -One of the "Two Guitars' let will be at WGBS is said to be a Russian prince sent traveling incognito; the other of the two is to you absolutely Serge Krotko , formerly a performer at Maxima's Cafe in Constantinople. if This sounds like publicity applesauce to FREE you will PRICES r- these old ears. * Langston Hughes is send me six .25 to 10 Megohms .50 the negro poet you are thinking of; he was cents above .01 to .24 " .75 Single Mounting .35 "found" by Vachel Lindsay, while a bus- .001 to $1.00 Double " .50 in stamps to cover .01 " boy at a Washington hotel. * * His Lynch Metallized Resistors cost no work has been read over several stations. cost of handling more than the ordinary kind. If your dealer cannot supply you it will be well and postage. worth your while to wait for the mail - ROBERT D.- ('harles D. Isaacson is the we ship postpaid, at once. impressario of WRNY; he was former musical critic of the Evening Mail. * 'N[ 7'11. So you are a Brokenshire fan. ' Wel!. well! * Don't try to work up our en- W. McMANN METALLIZED thusiasm; we eat men like Brokenshire. DEPT. PR L 1 1A..,i 64 CHURCH STREET SUPER-MAN. -Vee Laucnhnrst was not NEW YORK CITY FIXED RESISTORS named after a real estate development; she is now playing at WMCA in the Hardman Hour. * So's your Aunt Jemima.

www.americanradiohistory.com All apparatus advertised in this magazine Iras been tested and approved by POPULAR RADIO LADORATORN. Pane 801 Terted and approved by ail »B44S íltEE9NY{)URIIt of Radio's Highest Authorities Send Coupon for Amazing Special Offer! `5OAM° 6LáSÚST NOTE: This offer is made B UTIFULBIG- POWERFUL to prospective buyers by Ira IRACO tj famous Dig Radio Corpora. on, one of America's old 8,4,4íg , eat reliable manufacturer, of line sets- seventh sum tiesslul year. Many satin Retail fled users in every state. Postal or coupon brmgstee- simony of flambe user and L 1ST promproof Mimeo's outperform Sets Costing up to 4 times Price as much. Very easy t0 in FIER sae and operate. SPEGIA AMAZING ne IAL OFFER ÿcar Ion User-Agents who will friends to to o Y GUARANTEE SPEClueirMU Minces.

Bunt rfor- m like $200 nand Real Single Dial Control! Magnificent Big Powerful Miracoe'Unitune-5', Get Special Offer and Amazing Low Price! The celebrated Miracp Ultra -5- U.S. Navy type circuit, hag also been adapted to Single Dial Tuning -without eaerifie. of selectivity, volume, clearness, power, tone, or die. tonee getting qualities: In the magnificent big Miravo Uni. tune-5, above shown, you turn one vernier knob for stations everywhere. Beautiful hand- rubbed piano hinged, solid wal- nut cabinet, 29 in. long, 15 in. deep, Ib in. high. Sloping Bakelite panel is walnut finished to match. Also offer k0 days fns. Wall Coast to Coastaia Eórei n, IAAIC `Reception Certified RADIO 6112Iiraco users /ra G-le nu I ofth :,f. y,Jt: a7 tea ee 4 V ,eoWe,s l Notice! :FP.; " 1111lf GETS EM f fm delighted érhi¢hÌy mddnir,g i New them toofriends, enableu, m add host. of features, atest refinements Solid Walnut Cabinet Solid Walnut Cabinet COASTy0l and up-to-the-minute eÌImprovements such JL /// / . ht t to find d, J.j JSend COAa7T / ahf¢hrr Drieed rate. tllnm'. this rs 1I`ite Proof tW "etcbierw. wwerrfui ipriermomr gi `Libra USER -AGENTS WANTED . WRITE! afewrofrthemany our files andwhichlweoreceeiveadailThese TRADE MARK Ìn . Send coupon 28GO in.long fur plenty of additional proof and testimony of f27 in. long name users. HAS NO EQUAL FOR TONE VOL.. MOST SELECTIVE . SUPERIOR U ME,OIST NCE. North Wddw, ULTRA-SELECTIVE LONG DISTANCE 5 TUBE SETS EASY ON BATTERIES M,race N.J. but picked set 1 ever Colifotolaa. I do not br oteui Words showf my friends the "Mimeo Sa- the wondefulo quality volume, set, ro.ting d distance. Fin{ night received $ÿ2ö00 M,nm 47 The Unless Proves Your stations Loudspeaker. 't Trial the Most on Miraco Up to the most selective set I have Wt night, the 9th day, I have re- e yet andd cuts out the jumble exactly 109 stations; farthest fstations on the low owave , ngthe leceivedKGO, Oakland, Calif. on loud- to t 02 pointa. Wm. Schuette. . Also Porto Rico, Cuba sod Selective, Clearest Toned, and Most Gonad.. F rance a. MELLOW TOME .. LOUD AND Iwo. CLEAR. Indian River City. Fla. TONE QUALITY EVERY- Awooderset. Amhavingaplendid ONE. Phlladelybias Pa. Everyone remits. &bat bears tba Min; n very leased W havehadatt0000a 000nfour Powerful Distance Getter -Don't Buy it! tint from Cuba to New York. etc..Ituned indur. Denverinefowinn' com- No need to wear out expensive batteries burning 6. Our FaetorY Prices Save You Up to One -Half Inv International ing ih tone 7 or 8 tubes when users everywhere are reporting We deal direct by mail with users. agents and deal- Test Week I have one sold already did not even try. Mr. H. G. Duff. that the big latest Mirato 6 -tube sets actually are ere. thereby effecting great savings which are refiec- GIB. Msi- City. unsurpassed (even In amazingly Me..; SEW, Cuba; REFUSED TO TRADE at much higher prices) for razor- ted Iowpnces. Everßhingwe,eII i. high. 2E11. Edinburgh. EXPENSIVE SET. GFrOR edge selectivity, extreme long distance reception. grade. Don't confuse Mimeo's with small, cheap sets. also in Mi clear natural tone and powerful loud speaker volume be tip, In night on loud speaker. I ordered You'll Proud of Your Miraco Aires. Geo. W. Hill, Jr. he Mimeo for friend and he is combined with great economy in use of battery cur- In its big, handsome. expensive- looking solid wal- than pArgentine.WARS got situ O rent! Enjoy a powerful Miraco SO days in your home nut cabinet with sloping front, you'll be proud to have COAST.NRacNá I tny oorfo i t bU hrdeme refused and Ithaethe nameof the mat our risk -and be convinced! Your verdict final- friends examineand hear your Mimeo. In construction. 21.0 London lut Wednesday night la the community. M. E. no appearance and on r Mimeo. Heard choir sin Holtbest sett absolutely strings to this. Save or make a lot of performance. every inch a high - and announcement. Have also heard money onsets and accessories this season by sending priced set. Handsomely gold l -wx. Havana. Cuba; CYC. Mexico PENNSYLVANIA BEGINNER illustrated genuine City and GETS Pse ALL IMMEDIATELY for our Amazing Special Offer! Bakelite front panel and genuine Bakelite knobs- coast to coast.G Lawrence t'Unbert.m '. HiramoL ne month Direct with a finished in grained walnut. todsea n ry Deal Big Reliable Corporation Finest parts obtainable SELECTIVITYI- -CUTS TNROUON I Remember this offer is madedirect to you by a big -the kind used in8200sea. Bakelite sub -panel. Many STRONG LOCALS. Detroit Mich. stationstov from rrI I 1 am m than satisfied with my responsible manufacturing corporation-one of the exclusive features. Each Miracoreaches you complete- Minim. na cut through W WJQQ, UÍ futiel S;th. oldest and most successful set -builders in the indus- ly assembled, rigidly tested, splendidly and W.111.I packed CaoadaCub locaaltst tinns. endiihf. te done with and try -a concern which has grown to immense size thru factory guaranteed for one year. Easy to install and quarter of turo. In every way It inthkeis le recommendations of its many thousands of satisfied operate-full instructions supplied. Send NOW is Simply perfect. Charlee Paul. for prettyfo d for customers who bought after i testimony of nearby users CTO COAST trial and Amazing Offer! PROGRAMS. Heber had alnY ceneth The Mines sure can't he beat at efera.Drggteldae. What a $3,000,000Federal ReserveBankSays: AGENTS: any price. Coast sv ó DEALER ham hod sttions LINES'IT BETTER THAWS I SO "For year. the Midwest Radio Corporation of this city have been very in New York and Cuba in the east, a so Westville. Write for our and scores of other stations on the raiSETS. satisfactory customers of this Bank, one of the largest in Southern a « "I Ohio. The Midwest organization was one of the htteet Miravo K et. 1 ha.. logged up to geGe very flat to engage in proposition. data 1fìósutlou and the a come thct!h ne f the thik 6'1 the manufacture of radio sets, and to us their aurees. is evidenced by in wonderfully. Monte G. the sound and steady expansion of their business which we have Nation - wide I treeihee sra that roned observed year We popolaritY. M OTHER oheohotter after year. are personally acquainted with all officers ¡,cnor per- MAKES. I tried of the Corporation and from experiences know them to be men of honor, ,hreg other metros veil is ffreslk formance of the Mimeo. Ih had stntlansall integrity and ability. We consider them to be both morally and finan- the beet of them all. Received KFI, cially responsible. have Miracp Radio IL.. Ric Calif. o loudsaker,ix th U.S.Á. Ì tune in .te.,co limy reputation for fair and square am- U. Cioverty and Havana Cuba any time dealing.." THE PROVIDENT SAVINGS MANIC & TRUST CO. s,ts, at they are on the air. Alex kinder. azingly lower Neogddoochea. Tema. Oemy Mimeo Member Federal Reserve System. Capital and Surplus over p.0 0.030. trices, make I have heard station. from Cuba to B EATS COSTLIER SETS WITH San Francisco und from Mexico City MORE hem easy to to Pittsburgh. Welter M. Frlsbia. vTUBES. m tñröu'[h Ire Midwest Radio Corporation sell. Send cou- end lind It to do all you claim. pon today for COAST TO COAST LOUD AND 86 stations logged so far; getting CLEAR. Guthrie. M loo. We logged n every This li In- proof 30 stations and eludesdes ca coast. Canadien. .411 theThvof Abu want it waitingfarYou! Cuban andM esiean ealoo. The from hosts of in your vicinity and elsewhere that onrmron the loo e selectivity Is rem arkable. Coupon or postal brings reportA users proving the first night- -our O her. here lo town baye Miracp sets at rock- bottom money -saving factory prices, outperform Sets coot - first experience epneluve a d ng up to four times as much. You can also buy speakers, rado mortobr re b oboe, big savings from use we got WJAE lip n, hi batteries. etc., at JIghteck.nnville. Florida ever do this. Get our proposition before spends `.QRpoit: T10N odKFllo.An eles, money elsewhere Calif.. emp4. RADIO on the loudspeaker. h- MIRACO OUT. Buf 4es of S o. bon nay Mingo is the Mu they hive PERFORMS MlDW P ctncinngtl ever heard. (J. R. Wolf. THEM ALL Send coupon for SP 1 MIRACO BEATS A SUPER Eloift. St. Francis. of tar. AMAZING Gólte Cobalt. Ontario. Canada. Minim is Iviiraco BuUdinúr.ture. testlltwb9tgptory` Dglr moot the henradiosin all the north beard lot of 479.R tree maY..avini User pesette. There isa man wholue send radio, but the Amaking obul anon, {_ raiS. ( ) Aaou Super eightght and our Mimeo ie best Without Mbisirato beat It. W Samier. all around. lam d full part' Is:l tWU OUTPERFORMS SOME proud f mine. seta sad 1300 SETS. Shekel,. Commie Special/ Masco Ga. I am wel I pleased with ar. onoised tVW Mimeo. It does better Get lots of distant han machines that cwt Surely am NAME $900 or tiro. J. D. TUoo. tisfied.salions. OrveySbarpe. offer' I ADDRESS

www.americanradiohistory.com Page 803 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY BUTTERFLY.-Carolyn Andrews is now back in the Capitol gang. Yes, she is easily the most perfect soprano on the air; she is also the mother of a baby girl. Do we expect to be in the Hall of Fame? Why certainly; why not?

.TAMES BOWLES.- "Raindrop" was a fantasia presented by KNOX (St. Louis) on September 21, 19211. Mr. Gure- wich, the saxophonist, "appeared" at WOR; Sousa once said that he was the greatest player of this instrument in America. However, we're shouting for Rudy Weedoff.

HUCKLEBERRY. -We have tried to trace Jack Dorsey for you but our Intelligence 7 Department has been unable to locate him; sorry. Anything else we can N a Brdc1i- do for you? Yeah, we smoke cigars. JOHNNY. -Rudolph Pulelz played the French horn solo from WGBS on the night of September 21st; we did not hear CONTROLIT him, but a French horn solo does not seem exciting to us. It is said that A WORTH -WHILE GIFT this man comes from a family of French horn players. We come from a RADIO devotees will be glad to get a Brach Con- family of poker players. trolit on Christmas morning. Controlit is new. It's novel. It's different. It is something that will THOMAS BURNS. -We don't know who add enormously to the enjoyment of radio. plays WGN's "phantom violin" and we care less; it's cheap publicity, to our way Adding a Controlit to any set eliminates ALL P of thinking. Kelley Smith is the switches from "B" Battery Substitute and Trickle studio director of WBBM. Is Mac- Namee going to stay with the National Charger and places complete automatic control of Broadcasting Co.? We presume so. set and power supply in one switch - the SET Why should he leave? SWITCH itself. It is the gift of gifts to owners of radio sets. CIcER0. -The Do-Re- Mi- Douhle Quar- tette sings from KMOX. If you It should go with every new set at Christmas time. think announcers are detrimental to pro- grams, you're thinking straight. That makes you a very dear friend of ours Price $6 - in U. S. A. as N.T.G. might say if he had the chance.

JEROME J. J. -Al Santoro is the regular BRACH lightning Arrester sports announcer of station hCO. Were we ever an announcer? My heavens, do No aerial should be without the protection we sound like one? That's a very to radio and home which a Brach Lightning to ask this department. Arrester affords. Good sense demands this dangerous question protection. The authorities require it. Every Brach Arrester carries with it a $ I00 z insurance guarantee. CRANKY. -KGO's play "The Trick" Prices as low as St was written by Mrs. Rudolph Coffee, a J Californian. Kay Renayne sings The New Brach Drip-Proof "blue" songs from WBBM regularly. We TOTEM -POLE HYDROMETER are no great consumer of "blue" songs, we To the Hydrometer with the can tell you that. Don't write nasty ANTENNA famous Chaslyn Balls is com- things about Keith McLeod! Some dark bined the Drip proof feature v night you'll get tapped on the head with a Here is an aerial antenna that which insures full protection gives most complete reception against battery acid falling on piece of lead pipe; that's how much we and unusual clarity to radio. and injuring parquet floors, think of McLeod. It is the size of a small flag pole, rugs or clothing. can be readily attached to roof After testing battery, the Hy. or side or window ledge of drometer can be washed with- house and does away with all out danger from dripping acid. JULES BERNIE.- Eilelle Wentworth was unsightly makeshifts. singing from WPC; 1 Something nice to present to a the dramatic soprano Totem-Pole Antenna with 100 radio fan or to buy for your Atlantic City. She was the prima feet wound wire and fasteners, use. complete for own donna with San Carlos Opera Co. Only $10 Price SI N.Y.C. ANNOUNCER. -Do we ever tire of dishing out raspberries to the announc- ers? We don't dish out raspberries to the announcers; we chide them and deal out gentle admonishments, but that is all. Really, we're not nearly as Brach vicious as we may sound. CARL VAN BRUEN. -What made you Products think that Carolyn Andrews was Sirs. Radio Mendoza? You're wrong. Dacia L. S. BRACH MFG. CO., R'_warlt, N. J. Lady Baltimore (WBAL) is another L. S. BRACH OF CANADA, Ltd., Toronto, Can. "radio mystery."

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 803 Velvet rings Jay ?- -,, Wherever You Are! p Velvet Radio Speakers bring a def- inite contribution to Radio repro- duction in more than mere beauty -for the rich vi- brant tones are JÑJ natural as life itself -It's "just as if MOST any Speaker } you were there!" something of Radio's joy.. but until you really T You'll find a delightful have heard a "Jewel surprise in store -when Case" with its resonant first you hear the "Jewel tonal beauty, tonal com- Case"- or any Velvet pleteness, naturalness, you Radio S }eakers. have missed the fullest joy! There are so many claims in Radio we can- not ask you to believe our words -- -just believe your A rich musical background for own ears when you listen the tinkling pleasantries of the to recreations of music, card game -with the "Jewel speaking, or singing so Case". It's a musical instru- natural and satisfying you ment- supreme in tonal beau- scarcely realize the living ty and power -but it is, as well, authors are miles away. a rarely beautiful piece of That is Radio joy! handicraft.

For Christmas What more appropriate gift can you conceive - what more lasting pleas- ure can you give a loved one -than the joy to the eye and delight to the ear which the Velvet "Jewel Case ", of all Radio Speak- ers, brings in superlative No. 21 measure! "The Jewel Case" Words nor picture can fully reveal to you the soul of this instrument supreme -for it is as a Ask your Dealer! living thing -so natural are its tone recreations.

Sales Department Manufactured by The Zinke Co. The Borkman Radio Corp., No. 18 $27.50 1323 S. Michigan Ave. Salt Lake City, Utah "The Chinese Cone- Flex" Chicago, Ill. Kalamazoo, Mich. frinirfrilliffrEEITin

www.americanradiohistory.com Page 804 AU apparatus advertised in this magasine has been ksted and approved by POPULAR RADIO LABORATORY Wanted -A Radio Humorist (Continued from page 768) He is a good radio comedian; in fact, there is none better. And much of his 4D success is due to this very element of f n spontaneity, and also to the fact that his jokes and comments are upon events and happenings fresh in the f amazing public mind. His conmients are not the dead wood that so many entertain- ers pass out as humor. And also he has the ability to make his whimsical per- Special sonality carry over the radio; he can transmit it and stands as alive before the people with the headphones as he does before a Follies audience, or before Offer the diners at a banquet. Another factor in his favor is that he talks slowly and every word carries. Many a comedian has failed in broad- casting for the reason that he has talked too fast. It would not be too fast be- fore an audience which could see his facial expression and his illuminating gestures, but when these helps have to Fee -À LogBook be imagined the talk is so fast that only a part of it is understood. Irvin S. Cobb goes well over the with Every Set of radio, and one of the things which adds " much to his particular brand of enter- 'aristocrat tainment is the little chuckle he in- Vernier Port Dials dulges in when telling a story. The story is funny to him and he so com- pletely loses himself in it that he has to chuckle as he goes along, and this feel- THE Aristocrat Vernier Port Dial is three Aristocrat Vernier Port Dials, ing of enjoyment is in turn imparted to the finest tuning, finest looking dial your dealer will give you an up-to-date his listeners. And again he tells mostly on the market -the finest dial that men Log Book of 48 pages (worth $r). negro stories and he delivers the dialect so well that this, coupled with the fact, and machinery can build. Yet, despite It is bound in beautiful, two-toned as explained above, that a negro story its incomparable quality and superior MoCoTan Leather, embossed. Lists is the best kind of story to tell over the advantages, the Aristocrat costs no every station in the country using radio, makes him an outstanding radio more than ordinary vernier dials. power of 210 watts or more. All the success. It is interesting to note in this particu- Vernier ratio is 14 to r -fine enough important foreign stations listed. In- lar that Judge, Junior, is growing in to bring in countless stations that you've dexed by wave lengths, call letters and popularity as a radio humorist. He appears over 1VJZ never heard before. All mechanism location. You must see this Log Book and has a bright - chatter concerning the latest on Broad- and shaft only then can you ends are concealed. No gears, appreciate how way and its current attractions. At chains or cogs to backlash, wear out or valuable it is. first, people thought that he was in- get out of order. Easily installed -in spired by advertising, but now they are Remember, the Aristocrat Vernier beginning to discover that he has but a few minutes. The famous Kurz - Port Dial is supplied in three finishes - nothing to sell and that he merely talks Kasch Split Bushing fits all condenser about what So black with white markings and mahogany interests him. he is shafts -aligns rite, holds tite! coming to take his place among the or walnut with gold markings -at the popular entertainers. Judge, Junior, To acquaint you with this new same low price -$a. It is sold at all the himself was a former vaudeville per- superior dial we are making a special better dealers. If your's cannot supply former, but is no longer in vaudeville. He has a trained speaking voice limited FREE Offer. With every set of you, tell us about it. and knows how to get his effects. He is one of the few variety artists who is a THE KURZ -KASCH COMPANY, DAYTON, OHIO success over the radio. Moulders of Plastics It is particularly hard to get humor on the part of announcers at any of the Orrtces: New York, Chicago, San Francisco, Los Angeles, Portland, Spokane, Denver, Toronto larger radio stations, for the reason that the announcers are required to write out in advance what they are going to say and then must keep to the text. In this way they are not able to KURZ oaoo KASCH add anything personal or impromptu. In the smaller stations the announcers are allowed more freedom and can im- aristocrat Dials and Knobs provise and add to the entertainment by

www.americanradiohistory.com Page 805 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY ign o to sweet dreams

You enjoy radio like a gentleman -if you can get the best out of your set and forget all worry and bother. That's your happy frame of mind when you keep your batteries full of pep with a Rectigon. The most absent -minded dial twister snaps on a Recti- gon without a qualm. What if you do tune in while you're still charging your battery? There's no harm done, not the slightest. What if the current does go wrong in the dead of night? Your batteries will not be discharged with a Rectigon attached. when you keep dower in Your set with

No noise as it charges -not 6-14h a bit of fuss. Not even e Westinghouse a murmur that would disc urb the mildest slumber. Rectigon

No acids, no chemicals -no moving parts- nothing to spill or burn. No karger muss, no worry. You'll Batte have no spoiled rugs, no ruined clothing.

Saves its cost in short order - Count the dollars spent in a few trips to the serv- ice sta Lion and you'll hotfoot it for a Rectigon, for the good it does your pocketbook as well as your batteries.

Snaps on in an instant -just plug into the light socket, snap on the terminals. Saves service station bother. Spares interrup- tions caused by absent batteries.

Charges both "A" and "B" batteries - Keeps both packed with power. Bulb is used for "B" battery charging and it is en- closed, like all other parts, in metal, safe from accident. (Recti- gon charges automobile batteries, too.) THE RECTIGON is a superb Westing- house product. Things you can't see, like extra heavy insulation, things you can see, like the No Storage Battery Radio durably enameled case -all are of highest quality. manufactures a complete line of radio is Complete Westinghouse also instruments, and Micarta panels and tubes. Without a Rectigon WESTINGHOUSE ELECTRIC & MANUFACTURING CO. Tune in on KDKA - KYW . WBZ. KFKX

www.americanradiohistory.com Page 806 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY making wisecracks of their own. The larger stations are not in favor of it, as A Novel and Efficient Detector Receiver the stations wish to be bigger than any for employee, and if the announcer has any Home .. Office .. Hotel element of popularity he is apt to be- come bigger in the eyes of the public than is the station itself -and then he THE wants more money and the corporation can't see anything funny about that. A small station in New York has a TALKING BOOK rough and ready announcer who is Bringsa new story every night steadily gaining fame and popularity. There is nothing subtle about him - Complete merely rough, bubbling humor, but he Radio is funny. Rarely does he ever intro- Receiver "Weighs out right capacity as duce a speaker or an entertainer with- Pzir of standard Ear out getting a laugh out of his audience; Phones, Aerial and accurately as the Ground Leads, In- apothecary and so popular is he that often he is door Antenna, Self - weighs out a precious drug." bigger than the person he introduces. contained in attrac- But a large station, with all the rules tive book. A. C. L. that a corporation hedges around its Connected in a sec- ond. It runs for a announcers, would not keep him. Just lifetime. TECHNICAL men were about the time he got to be popular, No trouble -No over- quick to appreciate Sangamo the corporation would send him on his head. way, but it is he who makes the small condensers in intermediate capac- Equipped with New station very popular. is ities. One engineer, well known He one of the CELERUNDUM RECTIFIER real radio humorists of the country. to readers of radio publications - No battery required Austin C. Lescarboura -sends us And so we might close this article Tone Quality unequalled with an imaginary advertisement in the the following characteristic com- Price $3.50 ment, which is published with help wanted department of a newspaper: his consent: With Ear Phones $6.00 WANTED -A RADIÓ HUMORIST Live Distributors Wanted "In my laboratory we de- We are greatly in need at once of a num- Manufactured 8s Guaranteed velop new circuits and varia- ber of good radio humorists, male or female. by Applicants must be able to make people THE tions of old circuits, publishing laugh without hurting anybody's feelings. LISTEN -IN CO. the results in radio magazines. Steady employment, good salary and 115 Federal St. Boston, Mass. Needless to say, we are using short hours. Don't wait to write -apply and specifying Sangamo con- by wire. BROADCASTING densers throughout. In my DIVISION ANY RADIO CORPORATION Wonderful opinion there is no other fixed condenser that can compare Volume with Clearness with the Sangamo in accuracy, AM PL -TON E permanent capacity value, Changes in the List of neatness and handiness. Broadcasting Stations "The Sangamo condenser in the U. S. These corrections ard additions to the lint ud,i,h weighs out just the right cap- WWI published in the .March, 1926, issue of POPUL.UI acity as RADIO (together with the chargea which hare been the apothecary weighs pahliehel in succeeding months) make the list correct out a precious drug." as of November 1, 1926. Further changes will be pub- lished each month in this magazine. STATIONS ADDED KOCX Vida, Montana 240.0 KGDE Barrett, Minnesota 232.4 KSEI Pocatello, Idaho 260.7 KXRO Seattle. Washington 240.0 WBMS North Bergen, New Jersey 223.7 $300 WBRL Tilton, New Hampshire 365.0 Mica Condensers WDXL Detroit, Michigan 296.9 Phonograph makers have spent WEDC Chicago Illinois 422.3 WJUG New York, New York 516.9 years perfecting the acoustic prop- WKBO New York New York 285.0 erties of their phonographs. Use an are made in 34 sizes, ranging from 0.00004 W KBR Auburn, blew York 225.0 AMPL -TONE Unit and make a real mfd. to 0.012 mfd. Sangamo Wound WKBV Brookville, Indiana 236.1 Loud Speaker in an instant or use it Condensers are ready in capacities from WOBB Chicago, Illinois 552.0 WOCB Orlando, Florida in your horn and get better results. 1/ to mfd. to 4 mfd.; Series A guaranteed WKBS Galesburg, Illinois 361.2 After all, speakers are as good as for WTRC New York, New York continuous operation at 250 volts 239.9 their unit. We make a real unit at a AC, 400 volts DC; Series B guaranteed CHANGES IN CALL LETTERS real price. Money gladly returned if at loo volts AC, moo volts DC; also WBDC Grand Rapids, Mich. changel° you are not entirely satisfied. is and 14 mfd. blocks. WASH We make units for other manufac- CHANGES IN WAVELENGTHS turers. KFQB Fort Worth, Tee., 203 change to 508.2 SANGAMO1 KFWC San Bernardino, Cal., 211.1 change to 291.1 The UNION FABRIC CO. accurate? KFWI San Francisco, Cul., 226 change to 249.9 DERBY, CONN. KFWM Oakland, Cal., 206.8 change to 315.6 Radio Part, Maker. of the WCSH Portland. Me.. 2.56 change to 499.7 Excellent French AMPL -TONE Headset WEMC Berrien Springs, Mich., 285.5 change to 315.6 WGES Chicago, III., 249.9 change to 315.6 Please send me an AMPL -TONE W1BV Woodhaven, N. Y.. 469.9 change to 288.3 Unit for which I enclose $3.00. Sangamo Electric Company WJBW New Orleans, La., 340.7 change to 270.1 WLWL New York. N. Y., 288.3 change to 381.4 6332 -I0 Springfield, Illinois WRNY New York, N. Y. 374.8 change to 373.8 Name CHANGES IN LCCATIONS Address RADIO DIVISION, 50 Church Street, New York KFQW North Bend, Wash. change to Seattle Wash. KFWI South San Francisco, Cal., change te San Fran- State SALES OFFICES- PRINCIPAL CITIES cisco, Cal.

www.americanradiohistory.com LABORATORY Page 807 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO The Salt on the Tail of the Broadcast Frequency (Continued from page 775) this being the lowest frequency recog- nizable as a musical note. As 16 cycles is only 0.010 kc, this error would be extremely small. Although this test utilized a fundamental frequency of the quartz plate, it was found that there was no blanketing effect from the transmit- ting set sufficient to affect the operation of the piezo oscillator except when the oscillator was placed close to the con- trol board. Since in this test a funda- mental frequency of the piezo oscillator was used instead of a harmonic, the beat note was much louder than that previously obtained. From these tests of the piezo oscilla- tor one may predict that if their use becomes general in broadcasting sta- tions, all interference occasioned by beat notes between carrier waves of stations of different frequency assign- ment., will be eliminated. This idea is based on the fact that no two stations could ever deviate in frequency to such MakeYour Set Safe an extent that their frequency difference would be appreciably less than 10 kilo- With a cycles, a frequency which is entirely too high to produce an objectionable beat note in the phones of receiving sets. Of course a broadcasting station equipped Belden Fused with piezo oscillator apparatus directly connected in its transmitting circuit so that the frequency is automatically con- Radio Battery Cord trolled is even a step further toward the elimination of interference. However, a Radio Christmas, protect the new tubes and of the piezo oscillator perfect this application FOR and also avoid fire hazard from crossed wires by it requires partially re- batteries, is expensive; hooking up your set with a Belden Fused Radio Battery Cord. wiring the transmitting circuit. On the other hand, the use of the piezo oscilla- The tiny A and B battery fuses, concealed in the little two- tor as a separate device costs no more piece bakelite shell, can be easily inspected. than a well constructed frequency meter, This handy cord also improves the appearance of the set and and if the transmitting circuit is well eliminates all loose wires. designed, as indeed all transmitting circuits should be, so there are no sud- For maximum range and vol- - Ask your dealer den variations in frequency, it is merely ume, ask your dealer for a Bel It cannot cor- for a Belden Fused necessary for the station operator to denamel Aerial. Battery Cord. listen in the phones of the piezo oscilla- rode, even after years of service, tor at occasional intervals and make and requires no cleaning. slight readjustments in the transmitting Belden Manufacturing Co. set, demanded by the piezo oscillator. 2316A S. Western Ave., Chicago. Illinois The applications of the piezo oscilla- tor described herein utilize the faculty of hearing. It should be quite possible to add other apparatus to the piezo oscil- lator so that a variation in frequency from the transmitting circuit will, in- stead of producing a change in beat note, cause a movement of a needle e across a scale. Thus the individual 4414kL

=5-W This is a

© 911 Radio A PIEZO OSCILLATOR FIGURE 4: This schematic diagram shows Christmas the quartz plate in the circuit of a vacuum- tube oscillator for generating alternating cur- rent oscillations on a standard frequency.

www.americanradiohistory.com Page 808 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

preference of the station operator could QRS REDTOP be satisfied. Also it may be mentioned Radio Tubes that some operators prefer to have a beat note of a certain frequency pro- duced in the phones of the oscillator are when the transmitting circuit is prop- Better erly adjusted, while others may prefer zero beat. As shown by the experiments, either of these requirements can be met readily and the accuracy of either is more than actually needed. In case the beat note method is used, then it may be desirable to match this beat note against that obtained from a tuning fork of known frequency. The advantages of the piezo oscillator as a means of checking the frequency of a broadcasting station are peculiar to this piece of apparatus. Perhaps the most important advantage is that of constancy of calibration. The fre- quencies of the piezo oscillator as de- termined by the dimensions of the quartz plate are not affected by changes Super Detector Powerer Tubc 20íA Type Full Wave $5.00 $5 00 R ectifying Tube in inductance and capacity of the cir- 00 $6.00 cuit; it is merely necessary that these EVERY TUBE ABSOLUTELY GUARANTEED quantities be of certain approximate values in order to secure a fixed fre- You Will quency from the quartz plate. Depend- Note the Never Really ing upon the approximate values of in- Hear Your Radio Set Until ductance and capacity, the quartz Difference plate will either give one of the fixed Two tubes in one bulb - Consumes no more current You Use a QRS Redtop frequencies or it will refuse to function at all. The frequencies of the quartz Super Detector plate will vary slightly with tempera- ture, but for the use described in this The QRS Redtop Super De- article such changes are entirely too tector Tube is without a doubt the small to be considered. most wonderful detector Another advantage of the piezo oscil- tube made lator is that, unlike a frequency meter -with a 25% greater volume and a or frequency indicator, it is unaffected tone quality in a class by itself. by power variations in the transmitting set, which occur in both code transmit- American Radio Relay League ting stations and broadcasting stations. operator Knaack of Station 9 U Y In broadcasting stations these power says of it "I hear stations I never variations are caused by the voice or heard music modulations. The pitch of the before -it gives as much beat note heard in the phones of the signal strength as a regular detector piezo oscillator is affected only by shift- tube and one stage of amplifica- ing frequency in the transmitting cir- tion." cuit, and although sounds due to modu- lation may be heard in the phones, such We have many such testimonials. sounds are not loud and have no effect upon the frequency of the beat note. In conclusion, it may be said rWVn The QRS Redtop Power Tube that nothing will supply a large volume of un- short of actual mechanical injury to distorted output the quartz plate will cause a change in to your loud its frequency sufficient to affect its speaker; combining the double usefulness in a transmitting station. grid -filament and plate features with our new Power Tube design. "Man, you ain' gettin' no distance a -tall, is you ?" Illustrated literature mailed "Say, brown gal, heah dat whistlin'? without charge. 'Ems de Canary Islands!" -Princeton Tiger. s s The QRS Music Company Here lie the remains of a radio fan 306 South Wabash Ave. Now mourned by his many relations, Clearer Reception- Better He filled up his gas Tone Quality Chicago, Illinois tank while smok- You will never know how ing his pipe good your set is until you Factories an CHICAGO NEW YORK SAN FRANCISCO And was picked up by use better TORONTO, CANADA twenty -one tubes SYDNEY, AUSTRALIA stations. -Exchange

www.americanradiohistory.com Page 809 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

AMERTRAN RADIO PRODUCIS

A RELIABLE CHOKE for FILTER CIRCUITS The AmerChoke Type 854 is a choke coil or impedance designed primarily for use in filter circuits. As an output im- pedance with a fixed condenser it forms an ideal filter for the loudspeaker, insuring tone quality equal to the average output transformer. And it will be more economical. For filter circuits in "B" Eliminators, the AmerChoke will give perfect results due to its scientific design and generous proportions. To obtain even, quiet current supply use the AmerChoke and the AmerTran Power Transformer ( described at the left) in the construction of your power amplifier. The AmerChoke type 854 has a noload inductance of ap- proximately 100 henrys at 60 cycles with average close butt joints. Magnetic saturation from direct current is pre- vented by two butt joints in the iron core. The AmerChoke AmerTrart shipping weight is about 5 pounds and the price $6.00 each Dealer. The AmerTran Power FOB Newark, N. J. , or at any Authorized AmerTran De Luxe Audio Transformer Transformer Type PF -52 in- AMERICAN TRANSFORMER COMPANY This new transformer Type PF -52 is sets an entirely new tended for use in the Newark, N. J. of Audio power supply de- 178 Emmet Street, standard velopments. It will Amplification. It "Transformer builders for over twenty -five years" makes possible a convert the standard transformer coupled 110 volt. 60 cycle amplifier that excels alternating house all other forms of am- lighting current to plifiers. Made in a higher voltage for Other AmerTran We shall be very glad upon two types for first the plate and lowvolt- Products: to send you stages. a copy of our and second ages for filament request ,Price -$10.00 each supply. $18.00 each. AmerTran Resistor booklet "Improving Type 400 - $7.50. the Audio Amplifier" AmerTran Heater together with other Transformer Type interesting and con- H -28 (for A. C. structional data. Tubes) -$10.00.

AmerTran Types AF-7 and AF -6 AmerTran Audio Transformers. types AF -7 and AF-6, have been considered for years amont the leaders in audio ampli- fication. These popular d efficient models are made in two types -AF -7 (ratio 3 A :1) -AF-6 (ratio 5:1) $5.00 each. /D

www.americanradiohistory.com Page 810 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY How to Build the LC Intermediate Power-pack. (Continued from page 782)

Aoiseles s / your receiver become HASAS miniature Babel of strange noises? Look to your grid- resistor. There lies the seat of distortion in most cases.

The Durham Metallized Re- es sistor is scientifically built to function as noiselessly as the balloon gliding silently to- wards the sky. Fixed in re- sistance value, and tempera- ture- proof. 500 ohms to 10,000 ohms 51.00 HOW THE "A" AND "B" POWER -PACKS ARE Above 10,000 ohms to .24 meg...... 75 INSTALLED IN .25 meg. to 10 meg ...... 50 THE BLANDIN CONSOLE FIGURE 5: In the top compartment is shown the set and in the lower compartment is shown the charger, C, and the filter unit, A, which supply the "A" power to the receiver. At the right, is shown the intermediate power -pack, B, which supplies the "B" and "C" voltages to the set.

How to Install the LC -1 nterntediatePower- tu the "A," "B" and "C" voltages will pack with the LC -27 Broadcast Receiver be supplied from the power units. In the October issue the receiver was In the illustration (Figure 5), are shown with complete installation data shown the various units installed in F for use with a standard "A" battery and one of the standard Blandin Consoles DURHAM RESISTOR dry-cell "B" batteries; in the November with the set in the cabinet proper and MOUNTING issue the operating data was given for the Power Units installed underneath Made of moulded insulation of excep- using the receiver totally on an alternat- in the battery compartment. The tionally high resistance. Has best ing current supply, with a Davy "A" charger "A" is used to rectify the alter - quality, tension -spring, bronze con- Power -pack and LC- tacts. The only upright mounting the Senior Power - nating current and to deliver it to the filter made. Occupies but little space in set. pack. In this present article, in Figure B, which extracts the hum and supplies Aingle mounting 50e 1, is shown the electrical connection for the remaining pure direct- current to the i,r condenser._ 650 the LC-27 Receiver when used with the filaments of the tubes in the set. The LC- Intermediate Power -pack. For use LC- Intermediate Power -pack is desig- in conjunction with these, the Balkite nated as (C) in this picture. It supplies T ALLIZE TALLIZED "A" battery charger, type H or type J, the "B" and "C" power for the tubes in ENJ'tm1 ll111 and the "A box" Filter Unit is shown as the set. The wiring between the power a combination "A" power unit for sup- units and the set itself may be done with RESISTORS plying current to the filaments of all the special Belden power cable con- INTERNATIONAL RESISTANCE CO. the tubes. This will enable the opera- nector- assembly or it may be done with Dept. A. Perry Bldg., Philadelphia, Pa. tion of the set totally without batteries separate wires as illustrated in Figure

www.americanradiohistory.com Page 811 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

,wí!* i . .r ¡1 _._'!6í (West of Rockies, 1,` $ 18.00) An astonishingly low . 22- . price for this A.._t , inch Windsor Cone i Loudspeakermount- ).)1(. ed on sounding board I and supplied with easel. Can be hung on wall or stood on table or floor.

`` .1% ! R .%n..ii ÿ.r: ..0-

This Amazing New Cone Speaker lungs on Wall or Stands on Table! ()W the radio world enjoys a new sensation -a 2z-inch cone mounted on a sounding board and equipped with This Windsor Cone loudspeaker back so that it can he hung on the wall, stood on a Loudspeaker Console is N an easel equipped with a 22 -inch table, or placed on the floor. Windsor Cone Loud- Its tap is 30s speaker. Loudspeaker that reproduces x 17s and is 29s high. And this is the famous Windsor Cone The battery shelf pro- a/I the tones as they are broadcast. From the deepest throated pipes vides ample space for of the largest organ to the softest note of a crooning lullaby -from full batteries, charger, bat- volumed brass of a band playing "The Stars and Stripes Forever" to tery eliminator and the last faint note of "Home Sweet Home" played by a master vio- other equipment. Beau- is reproduced with perfect fidelity in all tifully finished in either linist -every tone, every sound Mahogany or Walnut. its beauty, just as it entered the microphone. Price only $ 2900 Model 200 model Windsor Cone Loudspeaker has no With 22.inch Cone (West of Rockies, $35) This wall and table equal in value in the world of radio. When compared with the average cost of cone -type loudspeakers of even smaller size and without the sounding board and easel back, the cost of this Windsor model is amazingly low. In this Windsor Con- sole is combined both Dealers everywhere -are showing this new radio wonder. Go to the Windsor Moulded your dealer today-see and hear this marvelous loudspeaker -note its Horn Composition extreme compare its low price with others- compare its tone and the utility- Loudspeaker have no other. If your dealer should not Windsor Cone -its volume -then you rvill 18-inch information and Loudspeaker. The top have one, send your name and address for complete is ;os x I711 and stands prices on the entire Windsor line of Cone and Horn Loudspeakers and lys high. Ample bat- Loudspeaker Consoles. tery and equipment of the high- space is provided by Write or wire today for details Note to Dealers ly profitable Windsor selling franchise. large shelf in rear. Price finished in Walnut or Mahogany $4800 WINDSOR FURNITURE COMPANY Model 302 World's Largest Manufacturers and Originators of Loudspeaker Consoles With Moulded Composition (West of Rockies $55) Horn Loudspeaker and 18. 1414 CARROLL AVE. CHICAGO, ILLINOIS inch Cone Loudspeaker Los Angeles Branch, 917 Maple Ave.

www.americanradiohistory.com Page 812 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY 1. A hole should be bored through LElrENO the back of the cabinet and the back of A L O RS OF TRNN SF D, r M ER I NELLaN' LEAO S the battery compartment for running ,,/NyNOP- the leads between á-RÉÓ -ENAAIEL the set and the power - 6 BLAIK units; the exact connections for all of O these wires is shown clearly in Figure 1. The input wire to the relay switch Inp IIIND MO Ow should be connected in parallel with the input wire to the Balkite charger and these should be plugged directly into the 110 -volt, 60 -cycle power lines through a standard plug and socket arrangement. If the set is to be used with an an- tenna, it should be connected as shown in heavy black lines in Figure 1. If added selectivity is required, this wire may be connected to the second post, as indicated by the dotted line. The ground connection is also shown in this a same pictorial diagram. If, however, /Yore: LEADS T,eeir FROM th'PER5/OE OF the set is to be used without an antenna, T,Prwrspa AIERARE5HOIVA'PV TEO the ground should be connected to the HOW THE TRANSFORMER LEADS end binding post that is ordinarily used ARE DESIGNATED FIGURE for the antenna. Notice that the fila- 8: This small drawing gives the correct information for wiring ment circuit is connected externally up the leads Precision to from the transformer, B, to the various the set with two wires run across to the other parts of the circuit. both The leads are of detail, electrically two "A" binding posts. The wire run- designated by color as well as by number. and mechanically, is what ning to the "A" ( -) post includes a Y2- places so far ahead of the ampere automatic filament control. pack. Be sure that the pins of the field the The loudspeaker should be inserted tubes are pointed in the direction of the in the jack on the front of the panel of arrows on the sockets otherwise the the set. The set is now ready for plate circuit may be short -circuited armson operation. through the filaments. o % Uniform Frequency After the "A" and How to Operate the Set "B" power -packs with the are connected and the Condensers Intermediate Power-pack plug is placed in Electrically the 110 -volt light socket with the switch this condenser has First of all, mathematically proportioned place two L'X -201 -a type turned off, the set is ready tubes to run. By plates so that all stations are in the first and second sockets in merely turning the switch the receiver. on the lamp uniformly spaced. The dielec- Then place a UX -200 -a socket the "A" power -pack tric is small and well removed type will begin tube in the third socket with a immediately to furnish current from the field. The plates are X -201 to the t -a type tube in the fourth tube filaments of the tubes small and close together avoid- socket. and this will ing losses due to fringing cause the automatic effects Put relay switch A on and large plate area and are a UX -171 type tube in the last the "B" power -pack to operate or and turn plated for high surface con- fifth socket. Then insert a UX -216 -b on the "B" and "C" power. ductivity. type tube in the socket on the power- Mechanically this condenser Next, vary the "C" battery adjust- is the smallest made. It is built on a rugged frame capable of mounting in all positions with or without single -hole mount- ing. The rotor is of heavy construction having cone bear- ings on either end and should wear indefinitely without ad- justment. A shield is incorpor- ated with the condenser to pro- tect against injury and dust. The Samson Uniform Fre- quency Condenser is furnished in five sizes: Prices 500 mmf., $7.50; 350 mmf., $7.25; 250 mmf., $7.00; 125 mmf., $7.00; 75 mmf., $7.00. Our book "Audio Amplifica- tion"- already accepted as a manual of audio design by many radio engineers -con- tains much original information of greatest practical value to those interested in bettering the quality of their reproduction. Sent upon receipt of 25e. /-- Samson Electric Co.

Wain OfBre Manufacturer' HOW Canton. Mass. Since 1882 THE BINDING -POST PANEL SHOULD BE MADE FIGURE 7: This drawing gives the exact size of the small panel, L, as well as the dimensions for the drill holes for the binding posts and the "C" battery control resistance.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 813 A Brief Study of Audio Amplification

TN THE design of any amplifying device for A 1 use at audio frequencies, it should be kept in mind that the curve of voltage amplification against frequency should approximate as closely as possible a horizontal line, if true tone quality is to be preserved in the process of intensifying the audible notes. Since the purpose of amplification is to effect a considerable increase in volume, the curve representing the character of amplification should be as high as possible as well as a straight line running in a horizontal direction. While it is a comparatively simple task to design a transformer to have a high and even I \pc 265 amplification curve over any narrow frequency '1'2, pe 369 band, it is considerably more difficult to main- tain the same degree of amplification at very low Audio and very high frequencies as in the middle of Coupling Transformers the range. Impedance In order that a transformer may function efficiently at Under average conditions two low frequencies, its input impedance must be high- several While the greater amplification stages of audio amplification are times the plate impedance of the tube at too cycles. This is that is obtained by a transformer necessary to produce the desired transformers accomplished in the General Radio Type 285 coupled amplifier has much in its loudspeaker volume. by means of a core of large cross-section of high permeability quality can steel and a primary coil of many turns. Proper coil design, favor, slightly better Usually a combination of to 2.7 avoiding excessive coil capacity and magnetic leakage pre- sometimes be obtained by the use of and t to 6 ratio transformers proves vents loss of notes above the middle register. if one is willing most satisfactory, with the high impedance coupling, ratio preferably in the last stage. Careful laboratory measurements of all General Radio to dispense with the greater ampli- Type 285 Audio Transformers show a high and compara- fication per stage of transformer The new General Radio Type tively flat curve over practically the entire section of the coupled amplification. 285 -D transformer has a ratio of to audio range covered by the human voice and musical 2.7 and has been designed specifically instruments. The impedance method of coupling for use in the first stage of audio am- in It will be remembered by radio experimenters whose is considerably more efficient than the plification following the new type terest in the science dates back to the early days of broad- use of resistances because it allows a 2ooA detector tube. Because of its casting, that in 1917 the General Radio Company brought high input impedance, it produces out the first closed core transformer to be sold commer- much larger proportion of the plate very noticeably better tone quality cially. This instrument was the type 166. It established a voltage to be impressed on the plate than is possible with other trans- new and higher standard of audio frequency transformer of the amplifier tube. formers having a lower input impe- design. Since that time the subject of amplification has been dance. exhaustively studied in the laboratories of the General By using a choke ot sufficiently Radio Company with the result that transformer design This transformer is particularly high inductance a quality ot repro- has been constantly improved and today the General Radio adapted, therefore, to use in the first duction may be obtained which can is universally recognized as an outstanding manu- stage of audio amplification and Company gives facturer of quality transformers. not be distinguished from that ob- excellent results in the second stage tained by the use of resistances and a as well. Ask your dealer or write for catalog 975 containing full descriptions and prices of all General Radio Parts larger amplification per stage pro. Type 285 t to 6.... Price, $6.00 duced. w Type 235D 1 to 2.7 .. 6.00 GENERAL RADIO CO.! Type x69 Coupling Impedance, Type 285 -L t to 2.... 6.00 Cambridge, Mass. Price, $5.00 ea. GENERAL RADIO PARTS AND ACCESSORIES Behind the Panels of Better Built Sets

www.americanradiohistory.com Page 814 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY ment K, on the power -pack until the last tube in the set draws the proper plate cur- rent. This may be determined by means BettQ1 than eves;/ of a milliameter connected in series with LC-27 KITS the plate circuit. Then, tune in a sta- PARTS EXACTLY $85.205.20 tion exactly as outlined in the article AS USED BY O The NEW in the October issue of POPULAR RADIO. AUTHOR r MINI a signal is tuned in loud, make a Prúsl iyainhzzol further adjustment of the "C" battery COMPLETE WITH INSTRUCTIONS resistance, K, until the tone quality sounds the best. When this is done the V9UPPLY set is ready for constant use and will The SILVER need no further care. SHIELDED SIX Type 612 If an "A" battery is to be used with the set it may be connected in place of COMPLETE $95.00 The SPECIFIED PARTS "B" Without a Buzz the "A" power -pack except that them P WITH INSTRUCTIONS Prepaid will I no wires running from it to the 110 -volt alternating -current supply. If the constructional data in this THE article and in the article on the receiver Iran Hun HI -Q in the October issue is followed closely, NEW oberts and if the connection diagram shown in COMPLETE $63.05 Figure 1 at the head of this article is AUTHORIZED KITS le adhered to strictly, this interinediate WITH INSTRUCTIONS Prepaidsl power -pack will need no further atten- tion and the set will give the right kind of service on broadcast reception with SMALL DEPOSIT WITH ORDER no more fuss or bother than the simple WILL INSURE SHIPMENT Delivers i8o Volts turning on and off of an electric-light ON DAY OF RECEIPT socket switch. DEALERS: Get our attractive ALL VOLTAGES "From Fire and Flood discounts before buying elsewhere ARE -" ADJUSTABLE (Continued from page 783) following morning were sent by radio RADIO MAIL ORDER HOUSE from these amateur stations. And thus 296 BROADWAY NEW YORK CITY Complete with the world knew of the plight of Sand Raytheon Tube Springs. The town was no longer 7c%%%%%%%%%%%%%%%%%%%%%%%%:: isolated! $42.50 As it became known that a way had . been opened through the flood to Sand ti a . AMAYOLIAN gives you, direct from Springs, and that young McKinney was gl Resistance-Coupled :. your . light socket, silent, dependable handling messages free of charge into "B" current -at half the cost of burn- ERFECT AUDIO AMPLIFIERti ing a 25 the stricken community, his little shack } -watt lamp. This means greater ef- ti ficiency, more volume, better tone from your resembled a busy telegraph office. receiver -and the permanent solution of all Anxious men and women wrote out ~ :-. i_ ti "B" battery problems. '_ messages of inquiry to parents and More than four years of pioneering and friends; these were dispatched quickly intensive research have led us to the devel- and directly to Halton Friend. opment of five types to meet the voltage and - . l'r'Hdea audio emplifleation aito minimum distortion. Rndleranit - - current requirements of any receiver. There wasn't much sleep for McKin- o1Jed resist used In föa tiradle -Amplifler áo a arl wlib age and .re of ado eted by.hnoepnerio % ney and Friend the first night. Thirty t Inconditions. Can be used replant transformer amplifier* Mayolian Units have earned the endorse- standard radio sots withdecided Wens. intonequality. ment of the leading engineers, magazines minute schedules were agreed on. First ti and receiver manufacturers, because each one station, then the other t ansmitted 612WPORKI,W CO. k laboratory-built Mayolian is unconditionally the accumulation of messages. Arms Electric Controlling Apparatus guaranteed for one year - provided seals began to stiffen, and fingers grew numb 276 Greenfield Avenue Milwaukee. Wis. remain unbroken, and installation instruc- tions are as several thousand words passed over :- ..:rave r.vorreee:r :ti carefully followed. Mayolian pays .. :.:: for itself over again every year. the keys of the operators. { After the first day, the traffic in- The nearest Mayolian Dealer creased, and station 5GA, operated by ti will demonstrate. ll'rite as! Edward Austin, Tulsa, came to the B rescue. Then another station in Sand THE PERFECT GRID LEAIC Springs was brought into action, 5GJ, Provides a noiseless range MAYOLIAN ti dof grid leak resistance from ., owned and operated by Howard Sieg- RADIO CORPORATION ti % to 10 megohms. Assures - fried. most effective grid z 668 WebsterAve., Newyork, N.Y. Besides messages for the local tele- J,Jl1l1`,`,y leak resistance . u. rt value for all tubes. ' ionerrs in Battery Elimination phone company, press news for the ti Tulsa Tribune and the Tulsa Daily VI' Small gridconden - : ser(0.00025) is sep- World, over 200 personal messages and 4 amte. Metal parts ti 40 special reports were handled by the L/1``' nickel plated. One hole mounting. - The Power of Niagara - 5GJ and 58R stations in Sand Springs and by 5GA in Tulsa. Instead of a half k The ,t_iet of an Arctic Night hour schedule, a ten-minute schedule agn-Bradbr c ti Electric Controlling Apparatus was possible. Siegfried's first watch 276 Greenfield Avenue Milwaukee. Win. began at 7.30 P.M. the second day of Y.r v v v: .... 4i..r::: le a.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 815

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-i

n DEALERS - JOBBERS: The Cooper "A" Eliminator is entirely different from the many "A" power dances on the market. It offers tremendous saks possibil- ities. Limited distribution and full protection to trade outlets in- sure legitimate profit. Write for full particulars of our exclusive proposition.

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Actually Eliminates the "A" Battery ! Operates Any Receiver Direct from the house current! No batteries to water -- -needs no attention of any kind At last the storage "A" battery, ing system. The Cooper "A" Elimi- with its messy watering and charg- nator requires no attention of any ing, has been totally eliminated as a kind - no batteries to water or radio necessity. bother with - no acids or liquids to Now any set can be operated direct replace-plug it into the light socket from the light socket. The Cooper as you would an electric iron or "A" Eliminator actually eliminates toaster. A simple throw of a switch the "A" battery- creates filament and your current is on-tumble back current direct from the house light- the switch and the current is off. Not a Power Unit - Employs No Trickle Charger The Cooper "A" Eliminator operates purely on a rectification and filtration principle. It delivers up to 21A amperes of noiseless, distortionless filament current that works wonders with your receiver. The Cooper "A" Eliminator is designed to operate on any make or type of receiver using up to ten 6 -volt tubes. It consumes current only while you use the set. Send for This Free Booklet! We have prepared a very complete folder describing the Cooper "A" Eliminator and the new principle upon which it is built. A letter or post card will bring it to you free. Good radio dealers in most cities have the Cooper "A " Eliminator now on display. Price $87.50 (tubes extra); slightly higher west of the Rockies.

THE COOPER CORPORATION, Radio Division, Dept. P, CINCINNATI, OHIO Founded 1904 - Factories, Cincinnati and Findlay, Ohio

www.americanradiohistory.com Page 816 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY the flood, and he stayed at his post until 7:00 A.M. the next morning. After nearly twelve hours of continuous oper- ating, he was relieved by Halton Friend, SHIELDED DIAL who continued until 6:00 P.M: that EB FOR ANY TYPE CONDENSER night. From then on, it became easier to Turns Clockwise and Counter - Clockwise handle the traffic that was piling up at both ends. Even then, operator Completely shielded by its metallic Austin back, this dial minimises the effect of welcomed the assistance which J. B. body capacity and improves the appear- ance and performance of any set. Sen- Lewis (whose station SWX was not sitive and finely constructed, it makes then in operation), offered him in accurate tuning possible and keeps the run- instruments set even after your hand ning his station. is removed from the dial. Static was increasing. And added to The Eby Shielded Dial operates any type condenser whether it turns clock- the torment of sore muscles, was the in- wise or counter -clockwise. Graduated creasing sleepiness from 0 to 100 and from 100 to 0 with a that overcame the hairline indicator and beautifully tired little group of doughty operators. moulded black Bakelite housing. Only now and then were they able to No gears or washers to wear out. Smooth, noiseless, sensitive action ob- snatch a few hours of rest. tained by an anti -backlash friction drive and non- microphonic construction. One During the whole of the second day, hole mounting. messages kept on going between the Eby Products are recommended and two links. Static was playing havoc used in the Infradyne H am m ar- I u n d- Roberts, Cockatiay, LC 27, with the tympanums of the young oper- Browning -Drake, Victoreen, Madison - Moore, Lynch and Varion Power Units ators. Apparatus was beginning to and other popular circuits. show wear under the unaccustomed pressure to which it had been subjected Price, $2.50 continuously for several days at a stretch. Made by First, McKinney's station began to A complete metallic sputter. THE H. H. EBY shield forme the back The operator in Sand Springs MFG. CO. of this new dial and 4710 Stenton Ave. Philadelphia, Pa. minimises the effect grew anxious as his fellow-amateur's or body eapafty. Manufacturers of Ebv Binding When the hand Is re- signals showed signs of unsteadiness; to Posts and Eby Sockets moved the set stays tuned to the station him, it meant the loss of the threadlike coming In when your hand was on the dial. connection which tied Sand Springs with Tulsa. At Tulsa, McKinney fixed up one bit of apparatus, then another, as he worked the key hour after hour. First, the insulators sparked; then the rectifier brewed difficulties. This part of the transmitter absolutely had to be repaired and time was taken, between Attention schedules and winks of sleep, to repair the cells individually so that they could go on with their important work of Dealers rectifying the current for the trans- mitter. On the third day, the waters began Send for our to recede. One of the roads became passable, though it was in very bad con- 200 page catalog dition. On the fourth day, gangmen from the Southwestern Bell Telephone VOY Company, Western Union, and M. K. ERO R T. were patching up wires, righting poles, and stringing lines to replace those "Built Ile urs" that had carried away in the flood. Soon, line communication was re- estab- lished. FIXED Until the 14th of June, the stations manned by the amateurs kept up their service as an auxiliary to the lines. CONDENSERS The finest and largest Then, Sand Springs was back in the are Specified to exclusive Radio swing of things, drying itself out of one Catalog of the worst floods it has ever expe- LC27 by L. M. Cockadal in the United States rienced. And the small group of radio Diamond of the Air " Herman Bernard amateur operators switched off their 7o be announced soon( ?) " John Rider transmitters to catch up with lost sleep. Raytheon "B" Eliminator " Raytheon Mfg. Co. ultradyne ' R. E. Lacault For this service in alleviating human To br announced soon( ?) ' R. E. Lacault Schneitter suffering and saving human life, the Mamma fixed condenser have been approved Comm'ttee of Awards has conferred by M. I. T. and Yak Universities. Radio Company upon five radio amateurs -Raymond V. Dept. G Kinney, Halton H. Friend, Edward AEROVOX WIRELESS CORP. Austin, Howard Siegfried and John 489.491.493 Broome Street St. Joseph :: Missouri Lewis POPULAR RADIO Medal for New York -the Conspicuous Service.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 817

ghe new Balkite"B"af 279 and the new Walkita Charger convert your radio set

CVJ info a light socket receiver To enjoy the convenience of operat- charger gives you the advantages of ing your radio set from the light socket both trickle and high -rate charging. add the new Balkite "B" and the new Both Balkite "B" and the Balkite Balkite Charger. Charger are entirely noiseless in op- Balkite "B" -the unique "B" power eration. Both are permanent pieces of Balkite supply -eliminates "B" batteries en- equipment, with nothing to wear out Trickle Charger tirely and supplies "B" current from or replace. Other than a slight con- MODEL K. With6- volt "A" the light socket. The new Balkite "B"- sumption of household current, their batteries can be left on con- tinuous or trickle charge thus W at $27.50 serves any set of 5 tubes first cost is the last. Both are built to automatically keeping the or less where 67 to 90 volts are re- conform with the standards of the battery at full power. With 4 -volt batteries can be used quired. Balkite "B " -X at $42 serves sets Underwriters' Laboratories. as an intermittent charger. of up to 135 volts and 8 tubes. Balkite Over 650,000 radio sets Or as a trickle charger if a re- -one sistance Is added. Charging "B " -Y at $69 serves any standard set. of every ten -are already Balkite rate about .5 ampere. Over 200,000 in use. Price$10. West The new Balkite Charger at $19.50, equipped. Add these two Balkite of Rockies $10.50. (In Can. with both high and low charging rates, Units to your receiver now. Then ada $15.) is the most convenient of all methods you too will know the convenience of of charging your "A" Balkite Light Socket battery. At the low rate Balkite Operation. Then you it can be left on contin- too will know the uous or trickle charge. Radio Symphony Concerts convenience of own- Thus it automatically uith WALTER DAMROSCH ing a radio set always and the New York Symphony keeps your battery at ready to operate at These concerts are broadcast full power. W ith heavy every other Saturday Evening. peak power. duty sets, large sets or On intervening Saturdays Mt. West of Rockies: Bal- sets use Damrosch gives one of his pop- kite Charger $20. In Can- in constant ular piano recitals onW aguer's where excessive "A" great music dramas. At 9 P.M. ada: Charger $27.50; "B "- Balkite Combination current is required, a Eastern Standard Time, over a w $39; "B "-X $5950; When connected to your group of 13 stations: WEAF, "B " -Y $96. "A" battery supplies auto- few hours' operation at WEEI, WGR, WFI, WCAE, matic power to both "A" the high rate quickly WSAI,WTAM, WWJ, WGN, Fansteel Products and "B" circuits. Controlled by the filament switch on brings the battery to WCCO, KS D, WOC, WDAF. Company, Inc., North your set. Entirely automatic full charge. This new Chicago, Illinois. in operation. Can be put ei- ther near the set or In a re- mote location. W ill serve any set now using either 4 or 6- volt "A" batteries and re- TEFL. quiring not more than 30 FN milliamperes at 135 volts of "B" current -practically all sets of up to B tubes. Price $59.50. (In Canada $83.) All Balkite Radio Power Units B alkite operate from 110-120 volt AC current with models for both 60 and 50 cycles. The new Balkire Charger is also made in a spe- Power Units model 25-10 cycles. radio cial for

7 /_--.

www.americanradiohistory.com Page 818 .411 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Reliable- Noiseless Powerful KEEPS your set full of live, marvelous energy - ban- ishes its dull, listless moments due to run down batteries. Im- proves tone, and cuts operating cost to almost nothing. Rigidly tested and fully guaranteed. Double the pleasure to be de- rived from your receiving set with the órnell The BEGINNER IN RADIO CONDUCTED BY ARMSTRONG PERRY Voltage Supply ( "B" Battery Eliminator) A Good Set to Begin With powered broadcasting stations come in Equipped with long life Raytheon Tube which has no filament for $16.85 over distances up to a thousand miles with average atmospheric conditions. to burn out THE picture at the bottom of this Type "B " -i37 to 220 volts at 3o page shows the "makin's" of a beginner's s e milliamps.; 150 volts at 6o milliamps. one -tube receiver. In the back row are $39.50 Why Honeycomb Coils are Type "CB "- (illustrated below) 142 to the "B" and "A" batteries, which cost 227 volts at 30 milliamps.; 155 volts at a total of $2.40; in front (left to right), Useful to Experimenters 60 milliamps $49.00 are: a honey -comb coil, costing 50 cents, IN the early days of radio, most (West of Rockies, told $1.:10 to abore lid priers) a .001 straight-line Sold only through authorized CORNELL condenser, costing transmission was on wavelengths above Dealer. $1.75; rheostat at $1.00; a spool of No. 600 meters. Inductance coils for re- 22 double cotton -covered wire, costing ceivers were wound on cylindrical tubes 75 cents, Baldwin phones, costing either in single layers or with one layer $12.00; a WD -11 detector tube, costing over another. A single -layer coil used $2.50; and a grid -leak and condenser for in reaching the longer wavelengths 45 cents. might be three or four feet long, and it By using cheaper phones -and fairly took up so much space that it was in- good ones may be purchased as low as convenient to use in a small room. $2.50 -the cost of this entire outfit can Bank- wound, or multi- layer, induc- be brought down to $11.&5. Adding tances had disadvantages also, one of $5.00 for aerial wire, guy rope, insu- which was the amount of distributed lators, lightning arrester and ground capacity between the turns and layers. clamp, this still is about as cheap a It was discovered later that a coil plaything as a man can buy. The one inch long could he made to provide money it will save in gas, oil and tires as much inductance as a single -layer will more than pay for it in a season. coil three feet long, if the wire were A man who builds this set and listens zigzagged around the tube or form in- to all it can bring in will acquire a fund stead of being wound straight around. of useful experience and the rudiments Furthermore, the turns could be widely of a liberal education. Several hook- spaced by this method, and made to ups are possible. With a larger honey- cross each Other at angles that reduced Teatedand approved by comb coil, suitable for the longer waves, capacity effects. Raytheon Laboratories a set built of these parts has brought in With the coming of the broadcasting Beautify your Set European code stations. The higher- era, and the crowding of the amateur With its deeply etched plate, in antique gold fin- ish, this new at- tractive smooth friction, 9 to r vernier dial will beautify your set and make it a 1927 model List Price $1.50. CORNELL ELECTRIC MPG. CORP. Rawson & Annabelle Ste., Long sand City, N. Y. Please send full information about your Córnell Voltage Supply; also name of nearest dealer.

Name

Address ..-- ---__.. - -..- ...._.._._._.. dealer, check here and re HERE ARE THE PARTS YOU NEED TO BUILD THIS SET flIfceive special dealer proposition. Any boy with ordinary proficiency with tools can assemble this singlle tube receiver from the parts that he can buy at any radio shop.

www.americanradiohistory.com All apbaratus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 819

You must have this latest guide to Radio prices and Radio quality. All of our vast resources and radio experience have been utilized to assemble for you in one gigantic institution, the best and newest things in radio. The Randolph catalog is indeed the radio market place of the world -a masterpiece of merchandising that befits our house -THE LARGEST EXCLUSIVE RADIO MAIL ORDER HOUSE IN THE WORLD. Radio Bargains OVER 2000 ITEMS RADIO KITS From the most beautiful, sully equipped console radio set. Includes the following well known circuits, down to the smallest part or tool for the set builder-kits. parts and supplies of every conceivable type and style. .5, 6, 7 designed and approved by the world's fore- and 8 tube sets, with three dial, two dial. and the newest and most radio engineers: Madison Moore Super; most popular single simplified control. All sets are assembled Victoreen Super: Silver Marshal Six; in beautiful, genuine mahogany and walnut cabinets in a Sar- choice of latest types and designs. gent's Infradyne; Remler Super; Short Wave Kits; 9 -in -Line Super; New Acme Reflex; A complete line of "B" batteries, eliminators, including the Cockaday; Neutrodyne; Browning- Drake; all famous Raytheon Eliminators latest types loud speakers, cone speakers, "A" power unite. Everything in radio at classes of radio frequency. Super Heterodyne money saving prices. and every other approved popular circuit. The New Ampliphonic Six The Latest Two -Dial Receiver WITH THE

'10011,P Genuine Amplion Unit Genuine dark tone and shaded walnut cabinet. Stands 39 in. high. Top We Save You Money measures 27x16 in. Beautifully etched burl walnut because we handle radio panels. Built-in loud speaker with Amplion unit. exclusively and sell a tre- Large doors open to smaller doors enclosing a ß large compartment for batteries. chargers, elimi- mendous volume of every- nators, etc., everything concealed in this exqui- thing in Radio. sitely designed radio cabinet. Volume purchases reg- Tube Tuned Radio Frequency ulate prices. 6 -tube tuned radio frequency two dial con- We command rock bottom trol receiver. 3 stages of direct and trans- prices from manufacturera, and former amplification. Has provision for power in many cases we contract for tube and an additional tap for increased "B" entire factory output of exclu- battery voltage. Very latest construction in- sive products. You will benefit cluding solenoid coils, bakelite sockets taking all by our great volume of pur- prill.IWINMew the latest X -type tubes, modified chases and sales, by securing straight line condensers. Wonderful579 S anything you may want in _ volume, nothing like it on the mar- radio at a substantial saving. ket at more than twice the price. Without Accessories Closed view

These sets are typical examples sf the bargains In Five our catalog. You may order direct from this page, Symphonic sending Brown Spanish leatheroid finish cabinet with gold engraved walnut panel to match. P. O. money order or draft for full amount. Two small We ship freight or express, charges collect. Contrasted beautifully with the black fine tuning knobs. knobs control We guarantee volume and clarity. The volume control is of the finest smooth slow variation type. to back up every article with our own, Roller bearing. Condensers are of the modified straight line frequency type, sub- as well as manufacturer's, assurance of quality. stantially constructed and o' latest design. All Is sub-panel mounted, using the new X -t:pe socket. Latest development In solenoid colis. Two stages of low ratio audio amplification Columbia Senior Six with high grade transformer offers the true amplification re- Beautiful table set. New localized control. One hand quired for both low and high notes. to tune with, three rotating drums easily controlled and easily logged. Dark finish etched panel mahogany SZ49O finished hand- rubbed cabinet. Size 7x22. Without Accessories 6-tube set, giving tremendous volume, wonderful tone quality, set complete with five latest straight line condensers, solenoid coils; The 45 sub -base mounting and new am- type X201A tubes, two ov 100.0. Designed to sell f50 volt "B" batteries. one 100 overwith Puce, Amp. Hr. storage battery. without ncceeaorles complete aerial equipment, accessories 36 one battery cable attached Set complete with two 95 volt Including cone speaker of B" batteries, 100 amp. hr. type Storage "A" battery. one 4i4 pictured x°.554.75 volt "C" battery six type X201A tubes complete aerial kit, attached battery cable, cone speaker or Victor Columbia Grand borns type loud 6 -Tube Console Set speaker 565'S Here's a sensational bargain In a console radio with built -In loud speaker and adjustable unit. Spacious compartment for all batteries, etc. Very latest type 6 tube tuned radio fre- quency receiver. Low loss modified straight line frequency This Coupon Brings the condensers. Iias three stages of low ratio audio amplification. Designed to accommodate new power tube. Equipped with X-ty Great RADIO BooK FREE sockets. Beautiful gold etched panel with handsomely Pa= engraved designs. Price of set with accessories.. . RANDOLI'H RADIO CORPORATION This set with all accessories which include 2 95 volt "B" batteries 180 N. Union Ave., Dept. 193 Chicago, Illinois 100 Amp. llr. storage ' A' battery, 6 201A tubes. aerial and ground equipment -everything complete. nothing else $6535 Send me-free--your 84-page, 1927 Radio Book. t0 Day Have Book Nance Beautiful hand rubbed, You Must This two -toned ma h o g a n y Space limitations here prevent our telling you more about the Randolph Catalog. Simply fill out and mall the coupon -or you finished cabinet, size Street 1 8: 1 9 x 3 6. Built -In may send a postal or letter -and this truly' remarkable Radio and No._ - loud speaker. book will come to you ABSOLUTELY FREE. MAIL THE COUPON NOW. R.F.D. __ _Boa Randolph Radio Corporation City_.. __State_ 180 North Union Avenue Dept. 193 Chicago, ID. ti u

www.americanradiohistory.com Page 830 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY down to wavelengths around 200 meters, honey -comb coils lost some of the great popularity that they had formerly among amateur experimenters, because 4 they are less efficient below 600 meters than they are above that wavelength. However, they still are used extensively Improved Tuned Radio because of their convenient size and w:' h Benja in Radio Products FrequencyTrans formers form and because they are mounted in in Securing Results such a way that they are interchange- ((Radio able. A coil designed to cover the \' broadcasting wavelengths can be re- moved from the mounting and a coil that will bring in the transoceanic com- mercial stations can be plugged in, all o 111 Benjamin Radio Prnduds are oj the same hlyh n a moment. standard as the far-famed eleRa-?one Sockets- Another advantage that the honey- comb coil gives the experimenter is the You will find that almost every good ease with which circuits can be con- radio set in the neighborhood has some or structed and changed. A single honey- all Benjamin Radio Products in it. Radio comb coil shunted bya.001 mfd. conden- experts and set makers have Space wound; basket weave: cylin- proved drical ; highest practical air dielectric. ser, will cover a waveband from 130 to through long Proved togivethebestresults in sharp- experience that only radio 12,000 meters wide, parts conscientiously ness of tuning, increase in volume and depending on the and painfully improvement in quality. Authorita- number of turns in the coil. The small- made to improve delicate tive laboratory tests and practical ex- tonal quality, perience of manufacturers and ama- est coils in common use have 25 turns selectivity and volume can bringa leader- teurs shows that this type of coil ex- cels in every important characteristic. and tune down as low as 120 meters. ship in securing the best radio results. 21/4-inch Diameter The largest have 1,500 turns and tune Ifyouwould have your set just as good Transformer up to 26,500 meters. Even with a or better than your neighbor's make sure Compact. Especially desirable for single coil and condenser, several dif- crowded assembly. Eliminates inter. that every component part is reliable and feting "pick- ups." ferent circuits can be made. The De bears the trade mark of a manufacturer Set of Three. $5.75 Forest ultraudion circuit is one of the in whom you can place your full con Single Transformer, $2.10 most popular of these and, with proper fidence. The world -wide recommenda- 3-inch Diameter coils, will cover almost the entire range tion ofBenjamin Radio Products by radio Transformer of wavelengths used in radio transmis- authorities Ca»acity coupling reduced to lowest is the best testimonial for degree For use with .00035 Mfd. sion. There is another circuit in which their scientific accuracy and uniformity Condensers. a large coil, say one of 1500 turns, can in securing the best radio Set of Three, $6.00 be employed as a loop aerial to pick results. Single Transformer, $2.25 up long waves from high -power stations. Rewards for Radio Reasoners "Lekeless" Two coils, in a two -coil mounting, Awards for novel and original hook -ups. Transformers form a variometer, which may be used modifications of existing circuits; trade in tuning the antenna or the plate cir- names; slogans; write our nearest officeffi for full details. cuit. They can be operated in a parallel position or can be made to form any If your dealer cannot furnish you with angle up to 90 degrees, so the transfer BenjaminRadio Products send amount direct of energy from coil to coil is under con- to our nearest sales o ffice with his name and we will see that you are promptly supplied. trol. A slight change of wiring turns the variometer into a variocoupler, suit- Benjamin Electric Mfg. Co. able for use in most of the three -circuit 120128 S. Sangamon St. Uniform high inductance, low dis- hook-ups. The amount of inductance tributed capacity and low resistance. in the primary or secondary circuit can Chicago The external field is so slight that it New York: permits placing coils close together be changed instantly by removing one San Francisco: without 247 W. 17th St. Bryant appreciable interaction. coil and plugging in another. 448 St. Single Transformer, $2.50 Manufactured in Canada by the Benjamin Electric With three coils and a 'three -coil Mfg. Co. of Canada, Ltd., Toronto, Ontartol Cle-Ra -Tone Spring mounting, regenerative circuits that re- Supported-Shock- quire a tickler coil can be constructed; Absorbing Sockets with a three -coil mounting and a com- Straight Line Frequency Condensers plete set of coils, dozens of different Eliminates bunching of stations. Spreads the log evenly over the dial. Makes tuning easy. Adjustable turn- ing tension. Compact. A beautiful instrument that not only improves Spring Supported, Shock -Absorbing. reception, but adds to Stop Tube Noises. The greatest aid the good appearance of the set. to non -noisy operation. Contacts always dean. .00025 Mfd., $5.00 00035 Mfd., $5.25 .0005 Mfd., $5.50 75 cents each Brackets Battery An aid to simplification Switch in set construction. Sup- make biv ports the sub- panel,with make and When room underneath for ac- it's "in' it's "off'"oH' ,elimi- cessories and wiring. nating danger of wasteful use of batten,. A THREE -CIRCUIT Tl'Nl :R Plain -70c pair. Adjustable -$1.25 pair 30 cents each By means of three honeycomb coils and a triple coil mounting, an efficient tuner may be built for single -tube operation,

www.americanradiohistory.com 4G apparatus advertised in this maeazi,e has been tested and approved by POPULAR RADIO LABORATORY Page 821 Announcing the new J3e6t-OJJte Triki-Automatic Radio "A" Power Unit

AN "A" power unit combining Prest -O- Lite's fine storage battery with a trickle charger. A unit that can be plugged into an electric light socket, then hooked up to the radio set -and forgotten! It charges itself automatically. It's new. Entirely automatic in action. No switches to operate by hand. Now you can have full storage- battery power for your radio all the time. Power that is noiseless and without the slightest pulsation, the kind of power that brings in the distant stations loud and clear. Never again will you have to bother with a charger. Never again will a run -down "A" battery spoil your radio. A thing of beauty. Look at these new The unit is beautifully finished in deep maroon. Small features and compact. Even in full view under the library table it looks well. The battery. Ample capacity. Extra thick, rugged plates, deep -grooved separators. You'll find further details in the column at the left. But Unusually large acid volume requires in- the main thing is to see it. Go to the Prest -O -Lite dealer's frequent watering. One -piece, leak -proof rubber case, with acid -tight cover. Screw store. There's one near you. Or write us and we will give vent to prevent post seal and double baffle you a lot of interesting facts about this wonderful new "A" leakage and acid spray. power unit. The charger. Built on an entirely new principle. Silent in operation. Adjustable And remember, it is made by a company which has had of individual user. Economical to needs more than twenty years of manufacturing experience. to operate. Nothing to get out of order. years. Nothing to replace. Built to last for THE PREST -O -LITE CO., INc. No bulbs. No elec- No moving parts. INDIANAPOLIS, IND. trolyte. No water or acid to be added. San Francisco No electrodes to wear out. Entirely auto- New York Ltd.. Toronto, Ontario matic. No switches to operate by hand. In Canada: PrestLitc Company of Canada, shuts Built-in power relay automatically RADIO DEALERS SHOULD WRITE AT ONCE FOR FULL DETAILS off the charger when radio is in use and turns it on again when radio is idle. Will operate at any distance from set. Fully enclosed. Entire unit enclosed in beautiful metal case, with hinged cover jiA.1-0-4te and handle.

www.americanradiohistory.com Page R22 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY circuits and variations of circuits can be constructed. A complete set of coils, with from 25 to 1,500 turns, may be purchased, unmounted, for about $16.00. Mounted, they cost a little more. Unmounted roils may be hung on a rod, connected with the circuits by clips and wires, and adjusted with the fingers. The wavebands covered by the Enjoy the Pleasures of Radio This coils overlap to some extent, so the ex- perimenter can cover most of the wave- Christmas Through Hampton - Wright bands in common use without pur- chasing a complete set. THIS great catalog lists hundreds of efficient items One further advantage of the honey- that help you secure fine radio reception. All over comb coil is that it can be packed and carried with little danger of injury. the country radio enthusiasts are using The Hampton -Wright ordinary variometer, composed of a products successfully. Don't delay - write for YOUR stator and rotor, easily may be broken catalog in time for the holiday season. or even mashed flat. The compact honey -comb coil, on the other hand, HAMPTON- WRIGHT, Inc. can be stowed away in a Scout's haver- sack or a travelling bag, with a P. 0. Box 181 hand- INDIANAPOLIS, INC. kerchief or a pair of socks occupying the Specify Catalog No. A -8 hole in the center, and it usually reaches the end of the journey in good condition even though it may have been sat on en route.

To Get that Station Just Below Your Tuning Range SOMETIMES, when your receiver is tuned down to its lower limit, you may hear a station whispering, too faintly to be heard, words that you are sure would be interesting if you could catch them. Or it may hum some bewitching -MAcCME) tune, loudly enough to whet your C ELATSITE musical appetite but too softly to give DEALERS satisfaction. BATTERY When that happens, take one of those AND fixed condensers that may be purchased CABLE anywhere for a quarter and connect it in PROFESSIONAL series with your aerial, as shown in -a silk- covered cable of vari- the colored picture. A series condenser reduces flexible Celatsite wires, ACME the SET - BUILDERS for connicting batteries to set. wavelength of the antenna circuit. Prevents "blowing" of tubes; gives your set an WRITE FOR orderly appearance. Z` mow` LITERATURE Stranded Enameled Antenna AND OUR PRICES ON Best outdoor antenna you can buy. 7 strands of enameled ALLEN -ROGERS copper wire; maximum sur- The face for reception. Prevents LC -27 GUARANTEED KIT corrosion a n d consequent weak signals. The Original Celatsite -ii"ammarlund ' -a tinned, copper bus bar wire with non -inflammable "spaghetti" covering, for hook -ups. 5 colors; o7berts 30 -inch lengths. We also offer the highest grade of H1-0 "spaghetti" tubing for Nos. 10 to 18 wires. 5 colors; 30 -inch lengths. Flexible Celatsite SILVER -MARSHALL Flexible, stranded wire for point -to-point and sub-panel CORBETT CABINETS wiring. Non-inflammable "spaghetti" covering. BROWNING -DRAKE In black, yellow, green, red and brown; a color AMERTRAN for each circuit. Put SAMSON up in 25 -foot coils. Send for folder BRUNO THE ACME WIRE CO., DEPT. P KARAS NEW HAVEN, CONN. A SIMPLE TRICK TO AID IN TUNING The RADIO STAMFORD By connecting a fixed condenser in series SHOP with your aerial, as shown above, may Worth St. Conn. you 20 Stamford f1AKS SETTER RADIO be able to tune in on a station that now I escapes your set.

www.americanradiohistory.com Page 823 All apparatus advertised in this magazine has been tested and approved by POPULAR Rims.) LABORATORY

Send your good wishes and a Tungar too

If he enjoys the radio -surprise him with a G -E Tungar. It will keep batteries fully charged; help him to obtain better reception. Through the years, its helpfulness will be a constant reminder of your greetings. Two ampere, five ampere, or Trickle Charger -your dealer will show you the correct type for any service. They are all made by Gen- eral Electric -they all can be permanently installed, and they all say "good -bye battery charging problem." P. S. Treat yourself to one, too.

Two ampere - charges as two ampere but charg- all 2, 4 or 6 volt "A" and es faster. 14 to 96 volt "B" batter- auto Trickle -charges 4 or 6 ies in series -and volt radio "A"storage bat- too. batteries, teries: four charging rates Five ampere -same range up to one -half ampere.

East of the Rockies 2 ampere Tungar, $18 5 ampere Tungar, $28 Trickle Charger, $12 (60 cycles -HO volts) Merchandise Department General Electric Company Bridgeport, Connecticut

unR F G. U.S.' PAT. OFF. 2 ampere Tu:tgar I BATTERY CHARG ERI Mimi/ Tungar -a registered trademark-is found only on the genuine. Look for it on the name plate. G EN ERAL KL F1CÏRIC

www.americanradiohistory.com Pape s 21 :111 a>paratus advertised in this magasine has been tested and approved by POPULAR RADIO LABORATORY How to Build an "A" and "B" Power -pack for Direct Current (Continued from page 785)

jßRß Tran -Choke Unit A combination of transformer and chokes completely shielded in one unit For Building the RAYTHEON POWER SUPPLY Each unit is supplied with a Raytheon tube Write for Complete Literature Authorised Distributors E. P. Denham. Seattle. Wash. Gray Sales Co. Philadelphia, Pa. S. D. Darmatader. Chicago. III.

ames C. Pope Minneapolis. Min . Industrial Sales Co.. San Francisco AN END VIEW OF THE UNIT FIGURE 4: The three large resistors, that are used in the "A" circuit, are shown here in place. This view also shows how the binding -post strip FORD RADIO & MICA CORP. is mounted. 111 -113 Bleecker St. New York City Figure 3, illustrates how this is done. voltage be 22, then the detector tap The DC supply passes through the should be connected to the end of re- switch S, and then, as a safety measure, sistance RS. The balance of the voltage through a 10- ampere fuse on both sides may then be divided in the same man- of the line. Whatever ripple or fluc- ner. For instance if it is desired to have tuation in current there is present up to 85 volts on the radio-frequency tubes, that point is smoothed out by the chokes then the tap should be connected to the Ll and L2. All condensers in the cir- end of resistance R. The other re- cuit act as a by-pass -for any unevenness sistors, R2 and Rl, will add 25 volts of voltage at those points so that the more for the audio-frequency tubes, output finally comes out as a pure DC making a total of 110 volts available. supply. The resistances, R7 and R8, These voltages were obtained with a provide for a 40 -volt drop for the de- DC supply of 120 volts. For other line tector tube; 113, R4, R5 and R6 furnish voltages, these values will be practically 85 volts, for the radio -frequency tubes; proportional. while R1 and R2 furnish the balance of How to Construct the Unit the voltage output, or a total of slightly Cut the baseboard to the size given less than 110 volts of "B" supply. A in the list of parts and proceed to lay Announcing variety of combinations may be ob- out the instruments. The constructor tained, however, by carefully making should be careful that the layout, after the first of a series of new models connections to the proper resistors. it is finally assembled, will be a con- of The connections shown in the picture venient one for wiring. Figure 1 shows wiring diagram, Figure 3, enable the a good arrangement. Tll lvll llylldLLiTO1 V 1L! constructor to obtain the voltages men- The bank of condensers before mount- tioned above. For the convenience of ing on the board were first turned up- Combined the experimenter who may desire other side-down showing the bottoms of the with the utility of a voltages than those mentioned, smoking is loud the fol- cases with the mounting lugs nearest stand a speaker. lowing data has been Carry it about and have it where compiled. the experimenter. These lugs were all The voltages obtained at any one of soldered together by means of two you want it -on the porch or along the resistances side of your easy chair. in the order they are at lengths of bus bar each connecting a row present placed in the eliminator is given of mounting lugs. Sales offices Loops were made at in Table 1. the ends of the bus bar. The loops SANFORD BROS. Thus, if it is desired that the detector thus provided a means for fastening

CHICAGO . . 30 W. Walton Pl TABLE 1 CHATTANOOGA . . . 615 Broad Street SEATTLE Am Bank Bldg. Resistor R8 R7 R6 R5 R4 SAN FRANCISCO . . . 311 Minna St. R3 R2 Rl Factory: TI BONE'E NF Voltage 22 40 50 70 75 85 100 110 HBoR Y.

www.americanradiohistory.com Pair d25 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY onfide.l

"...... - -- '

PROVEDhave proved the World Radio FORTYThousandTests on different sets Storage "B" Battery satisfactory performance of the good Ferbend"B"Elima 12 Cell -24 Volt inator. 40,000 Ferbend "B" Eliminators are now in use. This wonderful instrument is in its second successful year Proved value. Thousands of users find re- "B" Elim- ception almost magical. Clear, true power of usefulness. Until you have used a Ferbend -instantly and unendingly. Wise economy. inator you have not known the ultimate in radio enjoyment. Sturdy construction -Solid Rubber Case pro- The satisfaction of Ferbend owners is proved again and again-every tection. Recharged for almost nothing. day of every month - by the steady flow of hundreds of unsolicited of this very fine instrument. The few Endorsed and listed as standard by famous testimonial letters from users from all sections reproduced here are merely examples of what every mail brings Radio institutions including Pop. Radio roves beyond a doubt the splendid perform- Laboratories, Pop. Sci. Inst. Standards, of America. This flow of testimonials "B" Elimi- ance, reliability, convenience and long-lasting qualities of the Ferbend Radio News Lab., Lefax. Inc., and other nator. "No Hum " -"More Volume " "Less Static " - "More Clarity'. -"Complete Radio authorities. What more need be - are repeated again and again all through Satisfaction." These reports from users the top" to stay. said? Extra Offer: 4 Batteries in series (96 the testimonials. They prove the Ferbend "B" Eliminator is "over volts) 810.50. USERS ARE ENTHUSIASTIC Calif. Montreal. Qu hee Canada Fort Riley, Kann. Petaluma sold all number with al- I sin highly ellrased with roue yourl B. F'i Ìe valor, gettlna woaderfnl results t El¡uron'Ñt I Ä leo.of of 1 market- Send No Money o[and aeod"reC 4 tsar throve "" It to the baton the marret rngsrdl' prier. lad here demonstrated Michaud. á y, Fiord M.F r. rll I fba to Alfred A. eeetmg W IfIE Clllhh, Slg. net. and nvnin and they all agra wlthme. ship same day order is received, by express i]5 Ml o. Dak. Ambridge. Pennnvlvenla . Rorden. Ya bao for VV Weave marathon delighted with your elim- Sn D.hch C. O. D. Pay expressman after examining have densOnt. OerfEilminator urií,dio inator. Havel bad it Februu r and with your we received It. but I t more than pleased It since Rmdaubl batteries. 5% discount for cash with order. McGRAW. Vhinilnstur and there is no lour Gust- F. I. tterthan any wet battery on the Remember - you save 50% on World int.tmuY n. M. Kromer. Mt Morrie, N. Y La. y Batteries, so send order to -day. New Orleans.rip mont; Ego hasogive `mmore Tbe"n^EnmIn. time ago than best result.. Would o chased eriiel:you part with It with it, Frank J. Mover. // pleased Kllna, 7'IY6- Rreoklyn. N. Y. N.Y. t highly recommend you Eli. 1219 So. Wabash Ave. Dept. 77 Chicago, M. The Eliminator initiator to anyone regardless 1 tttrr4 Maker. of the Famous World Radar "A" Storey Bae4ry l my ( tenle tii thed they expect to Prises d -wa. Ion h ar Awp- JIJ.pa. couldouldw,Macy n eve m ne year.c a epuipped k Solliid beoiernor give Frtb. W G. Stein. gat your radio dials at 288.3 meters for Me World Storage Bat- ¡t ter, Station WSSC. Varlets- NewTalent- Private Interesting. JmsT Sut.lVAN -Director and Announcer = 'CSI -CAW -go ' ' F7BENr kpdatNhBr,CCO tRBs1 i a tlttttllllll ti 1265° PERFECT FILAMENT CONTROL 1 . Z Provides complete COMPLETE '4 noiseless filamentcon- * . Nothing else to buy. Replaces "B" Bat FEI2,BEND^° { 4 trol for all radio tubes ¡ direct from Electric Light ti ;a teries. Operates :- ', withoutchangeof con- Socket on 110-120 volt A.C. lighting circuit. nections. Metal parts e Delivers up to 100 volts. ELIMINAT4R are nickel plated. One hole mounting. Self % containedsw:tchopens { Within Reach of ALL battery circuit when Second successful year -40,000 in use. Amazingly low in price - amazingly high in desired. performance. An unequalled value in radio. Equal or superior to any "B" Elimi- nator regardless of price. We made this claim over a year ago. Today this state- ge`_Bre4ge ment still stands true- proved by overwhelming evidence. Electric Controlling Apparatus % 276 Greenfield Avenue Milwaukee, Wb. NEW IMPROVEMENTS developed and perfected by the Ferbend Electric Co., now give even greater lasting satisfaction to Ferbend users. New solution and new special alloy electrodes make pos- sible a perfect electrolytic rectifier having longer life than any other type of rectifier. FERSENn Ask Your Dealer -or THE FERBEND"B" ELIMINATOR is ap- B `iZVB Send Direct proved and passed by THE PERFECT POTENTIOMETER Tite Company Mee man. If you prefer, we will make shipment the rigid Laboratory Frrhev.l WAVE TRAIS O. if Tests of Radio News. Uses graphite disc resistors which are -the instrumentment w leb direct to you upon receipt of price, or C. P.. has been widely i- 10 days to convince yourself - Popular Radio and t,ted hot never enuótñad, desired. Use for noiseless and not the if unsatisfactory. write us within that time and Radio Broadcast. affected by atmos- and [ Priced at purchase price will be refunded. Use coupon now pheric conditions. $8.50 FERBEND ELECTRIC CO.,419 W. Superior St., Chicago, Ill. Metal parts are nickel plated. One hole mounting. Finish MAIL THIS COUPON TO-DAY! and knob match g Bradleystat. Made in FERBEND ELECTRIC CO., 419 W. Superior St.. Chicago C. O. V. CI Send Literature a 200 and 400 ohm a Send at once. payeatm enclosed. 1:1 Send ratings. Name Address MOM 61101 Paadke I Electric Controlling Apparatus a II City State 276 Grrcenfi ld Av Milwaukee, W g a -...1

www.americanradiohistory.com Page 826 :111 apparatus advertised z i this magazine has been tested and approved by POPULAR RADIO LABORATORY TABLE 2 Filament Current LC -27 in amperes T3 T2 Ti Guaranteed by .75 DEB 90 EB 12.5 1.00 DEB90 DEB90 EB5 Allen- Rogers 1.25 DEB 90 DEB 90 EB 6 1.50 DEB 90 DEB 90 EB 7 Means - 1.75 DEB 90 DEB 90 EB 10 1. That every part is especially selected by the individual manu- assembled block facturer for ALLEN -ROGERS. the to the baseboard. other tubes of t to UX -201 type. Since The resistors Rl to R8, inclusive, each UX- 201 -type tube consumes %- 2. That each part is thoroughly should also be assembled before tested for ALLEN- ROGERS by mount- ampere and the L X -112 type consumes the Radio Electrical Laboratories ing by laying them on the workbench h- ampere of current, the total current under the supervision of R. E. and soldering their ends together in the consumption will be 1% amperes. In Lacault, E. E. proper order. The values of each resistor this manner the amount of current con- 3. That official full size blue may be found by referring to the list of sumed by all the filaments may be prints accompany your complete parts that is printed at the head of this easily determined. The set of parts. filament current article. consumption of each tube is clearly 4. THAT YOUR LC-27, WHEN The resistor block may now be mount- noted on the carton containing the tube. COMPLETED, WILL WORK ed by simply inserting bolts AND SOUND LIKE COCKA- through In the case where the total current con- DAY'S OWN. each end resistor and fastening to the sumption varies from those stated, the base. Before inserting the bolts, slip resistors This is why the complete set of to be used in the receptacles LC-27 parts you get from Allen - a washer under the head of each bolt. will have to be inserted as shown in Rogers, the only direct representa- This will protect the brittle porcelain Table 2. tive of the Committee of 2l Manu- jackets of the resistors. For currents over 2 amperes facturers, carries the following: another Next, mount chokes Ll and L2. receptacle must be placed alongside T3 The snap switch should then be placed and wired in parallel with it. Calling GUARANTEE in line with the chokes and the fuse this added receptacle T4, the resistors WE unreservedly GUAR- block right back of the switch. The are given in Table 3. ANTEE that anyone can arrangement of the base receptacles The power -pack is now ready to con- construct the LC -27 Re- provides a convenient means for placing nect to the receiver. Connect the bind- ceiver to function prop- additional receptacles. ing posts of the receiver to the pack in erly when built by using The next step is to cut and drill the their proper order. It will be noticed a complete set of parts binding -post strip. This strip is fastened that the no binding post is provided for distributed by us. This to the end of the baseboard with three the "B" ( -) minus connection. This is screws after mounting means that if the set the binding posts due to the fact that "B" minus ( -) and built by you does not in the following order, starting from the "A" ( -F) are automatically made in the end'nearest the chokes: "B" Amp. (-f), work as we claim it should "B" apparatusand at thesame time grounded. we will make it do so RI' ( +), "B" Det. ( +), "A" Bat. As a precaution the present ground lead without cost to you, even ( -), "A" Bat. (+). The power -pack of the set should be broken and a .002 mfd. though we should have is now ready for wiring. to .5 mfd. condenser inserted between to rebuild the entire set. How to Wire the Power -pack the ground and the ground lead. With the The best form of attack is to wire the recent popularity of the new power COMPLETE SET out of the way places first, and then to tubes where large "B" voltages OF SPECIALLY TESTED follow with the easier connections. are required it may be necessary to add LC -27 PARTS Refer constantly to the picture wiring "B" battery blocks sufficient to cover the voltage diagram. Use insulated bus bar, such as required. This is only true $85.20 where celatsite, to lessen the possibility of the utmost volume is required. LC -27 Mechanical Kit short circuits. For instance, if a total of approximately 180 volts is necessary add one 45 -volt How to Operate the Unit $12.50 block and one 22% volt block. Of course, The large resistors, R9, RIO and RI1, these should be placed in series with AmerTran Power -Pack are regulators for the supply to the fila- the negative terminal connected with the Kit for LC -27 ment of the tubes. Their vanes, as men- B amp ( +) binding post of the power - tioned in the list of parts, are for a five - pack and with the positive terminal $63.50 tube set having a power tube of the connected to the B Amp. (+) of the This kit carries the regular UX -112 type in the last stage and the receiver. ALLEN -ROGERS guarantee Names of responsible set builders TABLE 3 in your locality will be furnished upon application. Attractive discounts to Jobbers and Filament current Dealers. Send for free descriptive in amperes T4 T3 T2 TI folder 2.00 amperes DEB 90 DEB Direct rep festive of the Committee of 90 DEB 90 EB 3.5 21 Manufacturers 2 .25 " DEB 90 DEB 90 DEB 90 EB 4.25 2.50 " DEB 90 DEB 90 DEB 90 EB 5. Allen - Rogers I n c o r p o r a t e d How to Increase the Range of Kit Head quarters- Your Ammeter and Voltmeter it 8 Easy, 28ís St.. .clew `Yorlt.N^3' IN a Coming issue of POPULAR RADIO Mr. K. B. Humphrey will fell haw to get full value out of these two instruments -without buying new apparatus.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 82; An Amazing New World OF RADIO I Is Now Yours. istance, Quality, Volume, Selectivity - -- a new con- ception of these essentials awaits you with the use of

MADISON - MOORE TRANSFORMERS Stations from afar, which some of the finest receiving sets have failed to re- cord, come in easily with this instrument. Your dials become the magic key to a new and untouched realm of sound and melody. Tone is vastly improved and beautified, the most delicate shadings being faithfully reproduced. Selectivity, always a problem, is no longer difficult. MADISON -MOORE Transformers make every night a radio certainty, for they bring in DX like locals. Stations which the listener never before brought in, frequently come with loud speaker volume with the use of only a two -foot loop. Quality is immensely improved on all reception. Every MADISON -MOORE Unit is subjected to most exhaustive laboratory tests before it is approved for use. Every instrument is precision made and is as nearly perfect, electrically and mechanically, as skill and fine apparatus can make it. Radio Engineers and authorities accord it highest praise.

WHEN YOU HAVE INSTALLED MADISON - MOORE TRANSFORMERS YOU WILL ENJOY THE UTMOST FROM YOUR SET.

C If your dealer cannot supply you, write us J

MADISON -MOORE RADIO CORPORATION 2524 Federal Boulevard Denver, Colorado - U. S. A. READ THE GUARANTEE

MANS0N'«MOOkLJ1se3issert RADIO APPARATUS in the Wicrld! ,-

www.americanradiohistory.com All abbey-edits advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY How Circuit Resistance Affects Selectivity (Continued from page 772)

The TOBE Filter Con- "Little Joe" densers are specified in the COIL 4 This toroid coil consists of a primary and a Lightning Arrester new and deservedly popular secondary that have been wound in spiral Henry Lyford Receiver. shape on a torus form. Especially designed for This is another tribute to Radio Work. Made of the from any station depends directly upon carefully maintained E: porcelain, small, neat, rug- quality of TOBE products. ged and serviceable. Can E' = 2 rfLi 1 be suspended on antenna Now where L is the inductance of the or fastened to wall. coil in henrys; f, the frequency of the incoming signal; i, the current flowing Ask Your Dealer through the coil, and tr, the ratio of the circumference to the diameter of a M'f'd by CIRCLE F MFG. CO. circle. The magnitude of i will depend Trenton, New Jersey upon a number of things. It will be larger, the greater E, is made and when R is made smaller. The expression for i is E 2 The TOBE High -Voltage \/R' + Xx Power -Pack Type Conden- Where E is the voltage set by the sers are especially designed incoming signal, R, the resistance of the for use with the AmerTran circuit, and X, a tuning factor varying as C changes. Power -Pack, and are speci- fied for it. They will not X= 2trfL -C2trf MODEL "C" CHESTI' break down in use. Send Cabinets in stock -have piano hinge and are Combining equations 1 and 2: 10" deep- grooved front top rail being remov- for special literature. 2 rfLE able. Illustration shows gold line wood panel to E'= 3 match. VR2+.X2 Sizes Walnut Only Panel to Match 7x18 -10 $15.00 $1.26 It is apparent that E' can be made a 7x21 -10 17.00 147 7x24 -10 19.00 1.08 maximum if the capacity, C, is so chosen *7x20-10 21.00 1.82 7x30 -10 23 00 2.10 as to make X = O. Then *7x28-11 23 00 1.96 E2srf4 *For Madison Moore Receiver. 4 For s ictorecn Receiver. R This equation brings out the signifi- Walnut Infradyne cance of an abbreviation usually called Cabinet where The TOBE BH BLOCK, R $3000 2 c.a made to be used with the rfL new Raytheon BH Tube. Equation 4 then reads LC -27 Cabinets E The first B BLOCK of its 5 Mahogany or Walnut with Baseboard n kind. Contains one 6 and 1800 As may be seen, v is the governing $ two 4 Mfd. TOBE Filter The LC factor of a circuit because if n is small, -27 cabinets have 23° slope and take N x 26 panel. They are full 10" deep back of the Condensers. E' max., the voltage across the con- panel. denser when turned to resonance, is WRITE FOR folder showing complete LC -27 Price - $11.00 large. Line and other Radio Furniture. It so happens for a narrow band of CORBETT Tobe Deutschmann Co. wavelengths, such as from 200 to 550 CABINET meters, n, for a well designed circuit, is Cambridge .. :. :: Wass. MFG. COMPANY almost constant and is a convenient way St. Marys - - Pennsylvania of rating the value of a coil and con-

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 829

sane A TYPICAL RF TUNING CIRCUIT FIGURE 5: This indicates where the values of E' were taken in order to make the curves shown in Figure 2.

denser when used in receiving broadcast signals. However, if the values of n were taken for a wide band of wave- lengths, the resulting curve would be something like that shown in Figure 4. The dotted line, A, indicates the natural Brad,ahm E period of the coil or the wavelength Btadle_y.unit A No.IO 7500 OHMS where the coil is tuned by the capacity in the winding itself . The region B -C is where the coil should be used, for n is the smallest average value through that range. What a whale of a difference The importance of n will be further brought out by plotting a number of resonance curves. In plotting a reson- a few Bradleyohms make ance curve, a signal of definite and con- stant frequency is assumed and the -in a B- Eliminator! value for E' across the condenser, is calculated for different settings of the MAGAZINES and newspapers have been condenser C. This curve then gives an publishing circuits and instructions for idea of the selectivity of the circuit assembling B- eliminators. Many types of kits when used in a radio receiver, and is have been used, but the outstanding feature has therefore of the greatest importance. been the almost unanimous recommendation to Figure 2 shows such a curve where use Bradleyohm -E for plate voltage control and E' is charted against the capacity of a Bradleyunit-A for the fixed resistor. 500 micromicrofarad (.0005 mfd.) con- Bradleyohm-E The leading manufacturers of B-eliminators have denser. Below the capacity markings For B- eliminator service re- long since adopted Allen- Bradley variable and are given dial readings, zero reading quiring wide voltage control, Bradleyohm E is essential. fixed resistors as standard equipment for their being considered resonance. Four curves It is an oversize Bradleyohm B- with sufficient capacity to eliminators. In fact, the Bradleyohm -E has be- are shown with n = .01 (this would be a handle all normal B- elimina- come almost as universally used in Raytheon tube poor coil), n = .00706, n =.005 (repre- tor requirements. Be sure to ask for Bradleyohm -Eln the B- eliminators as the Raytheon tube itself. The sents a good coil) and n = .0001 (this checkered carton. Your dealer can get them for you. scientifically- treated graphite discs in these re- value could only be obtained with the markable units have never been equaled for aid of regeneration) . silent, stepless plate voltage control so essential Several interesting points are here for the satisfactory operation of a radio set with brought out. First, the smaller the a B- eliminator. value of n the greater the signal strength When you build your B- of the received signals (- n =0.01 gives Bradleyunit-A eliminator, always insist a signal represented by 100 while n = This solid, molded, fixed that Bradleyohm -E and Bradleyunit -A are in- resistor has no glass or her- cluded with kit. You then will be assured of per- .0001 gives a signal 100 times as great). metic sealing in its construe tion. It is a solid unit with fect voltage control. Send for folder "How to Build silver-plated end caps that are not affected by tempera- aB-eliminator "describing seven popular hookups. ture, moisture and age. By all means, use Bradleyunit-A when you need a fixed re- ALLEN -BRADLEY CO. sistor. 276 Greenfield Ave. :: Milwaukee, Wis. Use a-exi-131adir COIL 5 Perfect Radio Devices A compact, multiple -layered coil that is wound in bunched formation.

www.americanradiohistory.com .111 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

The NEW LC-21 F. D. Pitts Company INCORPORATED is the result of experiments by one of radio's most eminent engineers. We Ave. carry all the genuine parts as used by 219A,Columbus Mr. Cockaday in his laboratory model. The LC -27 is one of the best sets you Boston, Mass., U. S. A. have ever heard. 1- Hanunarl und \lid -Line Dual Con - denser .0)1)275 mfd $ 7.50 1- Hanmmrlund \lid -Line Single Con- denser .000275 mfd 4.65 1- Precision Duo-Octaform Coil Set 10.50 1- Amertran Deluxe 1st stage 10.00 1- Amertran DeLuxe 2nd stage 10.00 Merchandising 1- Amercboke 6.00 1- Dubilier s 902 Filter Condenser, 4 mid 5.50 Radio 1- Dubilier s 907 Filter Condenser 1 mfd 60 1- Mar -Co Illuminated Dial 0 -100 3.50 COIL 6 Since 1919 2- Mar-Co Small Controls especially A solenoid coil wound with enamel wire in for LC -27, 0- to 50, 50 to 0 1.50 1- Carter Battery Switch .65 spiral slots on an insulating cylinder. I- Samson Radio Freq. Choke Coi10S5 1.50 3- Dubilier .00025 Condensers 1.05 I-Lynch 4 meg. resistor bi Second, the resistance does not de- I -Lynch single mounting absolute selectivity of the I- Carter Single Circuit small jack termine the DEALERS - send for large 1- Carter resistance 0 to 10,000 ohms 2.111 i circuit, for if the condenser is two divi- and profusely illustrated 12 -Eby Binding Posts 1. "' 5- Benjamin U.X. Sockets 3.7 sions off resonance, the amount of signal catalog on the products of 1- Amperite 1 ampere 1. lu Mechanical hit, consisting of alumi- received Ls the same no matter what the scores of nationally adver- num shields, binding post strip, value of +t. This means that absolute tised radio manufacturers. Tait brackets 12..,l i decorated panel and selectivity cannot be obtained with this circuit, no matter how low the resistance Wholesale Exclusively Complete Parts $85.20 may be. Ready to Wire local station broadcasting Consider a le Corbett Cabinet for $18.00 on a wavelength such that it would be the LC -27 only resonant on the condenser at .00032 whose signal Mail Orders Promptly Filled mfd. Let another station, "Pioneers in the strength at the receiver is only one- tenth as strong, be on such a wave- Distribution of Radio" SUN RADIO CO. length as to be resonant on the con- 64 VESEY ST. NEW YORK denser at .00034 mfd. If we want to hear the weaker station, we naturally set the condenser at .00034 mfd., but we also hear our local station, for the signals from the two are in the ratio 200 to 150. BROADCAST i These figures assume that the coil and condenser have such a resistance that LISTENERS they are represented by curve No. 3. The POPULAR RADIO ATLAS and LOG There is one solution of the problem will give you a list of all the1NEW Broad- casting Stations with wavelengths and which lies in coupled circuits, shown in other necessary information Figure 5, but the adjustments require A Complete Atlas and Station Log considerable skill on the part of the The "POPULAR Remo International Radio Atlas and Gig" will supply you with full in- operator, as he has three controls to formation retarding broadcasting stations of of the setting the United States and ('anada. operate instead one, and This most useful and practical Atlas consists settings of the of 16 p gee. size 12' x 15'. printed on good pa- of one may change the per. from clear type In two colon. and contains operation, CI and a complete sedes of double page maps. includ- other two. In actual ing -The World-The United States -Canada X resonated, and then -North and South America. showing location C2 would be first of principal broadcasting. leading commercial the coupling between I.1m and I.r and governmental radio stations. S Delivers adjusted. This would require resetting SPECIAL FREE OFFER It 'You may have a copy of the "POPULAR RADIO r CI and C2 and this series of operations International Radio Atlas and Loe free. with Full "B" Voltage continued until the best selectivity with POPULAR RADIO for (8) eight months. greatest signal strength is obtained. For Only $2.00 The system is clumsy and has an added PM 42.00 hi bills to the coupon below only half as much If you are a subscriber to POPULAR RADIO your clawvrLar disadvantage that subscription wIl be extended eight months. B- BATTERY ELIMINATOR voltage E' is obtained as with the former Operates from lighting current like tuning arrangement. other household appliances. Uses .Let us now consider the effect of e, or Raytheon rectifying tube. Furnishes Date. the circuit resistance factor, on the POPULAR RADIO. Dept. 122A smooth unfailing plate current with- City. out hum or vibration. quality of the received signals. 827 West 43d St.. New York Enclosed Is my remittance of $2.00 for which you Write the Manufacturer are to enter my subscription (extend my subscrip- tion) for (s) eight months for POPULAR RADIO and send FREE a copy of the 'POPULAR RADIO Inter- i0C national Radio Atlas and Leg." ,Amerkari6leefric O COM DAN Y /sll Name.

State and 64th Streets A TUNING CIRCUIT Address. U. S. A. CHICAGO, FIGURE 6: This diagram shows the theoret- City. Makers of BURNS Speakers ical circuit for the closed oscillating circuit that is generally used in tuning

www.americanradiohistory.com Ail apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 831 To transmit speech_and music so that it preserves its natural quality not only the carrier frequency of .(say) a millión cycles a second must be received, but a band of frequencies from 5,000 to 10,000 cycles plus or minus the carrier. This band is necessary to carry the high over- tones which are so essential to lifelike reproduction. The 10,000 cycles band is marked on Figure 3 by the two dotted lines. Consider curve No. 4. The peak of this curve gives E' = 1000. Notice that the dotted line crosses the resonance curve where E' is approximately 185, so that a note of 10,000 cycles would only experience an amplification of 185 while the low tones would be amplified 1000. This is what is known as the cutting off of side bands which tends to destroy good quality. This tendency is sometimes apparent with a regenerative receiver, when the effective value of resistance may be lowered to an ex- tremely small value. Coil 3, as obtainable in practice, would not have this tendency to clip side bands, but if used in a multiple stage receiver, would probably be as low a resistance coil as should be used. To determine the best shape and type of winding for coils, six standard types were measured. The result of this work is shown in Figure 3 where resistance is charted against wavelength and in Increased Selectivity Figure 4 where n is plotted against wavelength. Coil 5 is a compact, multiple -layered Çreater Distance coil, but it has a high resistance. Some of this resistance is due to the fact that the distributed capacity is large, and dore Volume the coil is being worked too close to its natural period, as may be seen by com- BUT ABOVE ALL- parison with the general o curve Fig- ure 1. Coil 4 is a toroid. The coil proper is long, with a small diameter. Quality of Tone Coils 1 and 6 show up easily as the best of the six. They have spaced wind- On any set from the modest little Crystal Hook-up ings one on a bakelite form, the other to the Super Outfit simply install almost self supporting. It is interesting -you that at broadcast wavelengths it makes little measurable difference whether a THE CARBORUNDUM coil has a bakelite form or whether it. keg. L.a. Pat. Ott. has the form slipped out so as to be self -supporting. STABILIZING DETECTOR UNIT The measurements on circuit resist- ance were taken by the quarter deflec- $3.50 (in U. 3. A.) Dealer or Direct tion method, and a number of them Our Hook -up Book tells you how -send for it checked by means of a vacuum -tube voltmeter; hence it is believed the values The Carborundum given are nearly correct. Company THE CARBORUNDUM It may be hoped that the theoretical COMPANY ' Niagara Falla, N. Y. NIAGARA FALLS, N. Y. resonance curve given in Figure 2 will be rr carefully studied by those who are ex- Sanas OFFICES AND WARRNOtîSRV IN Please send free New York, Chicago, Boston, Philadelphia, Cleveland, Hook perimentally inclined. For, from this, Detroit, Cincinnati, Pittsburgh, -Up Book D-5. it is easy to see how difficult it is to gel Milwaukee, Grand Rapida absolute selectivity on powerful local The Carborundum Co., Ltd., Manchester, Eng. 7 Name stations. , m is th. R.nIM.M Tad. N. Of course, those who have operated sod Ths Csriourundum Oompuly for BID Street o - ulade. ni. tos, Muh i. tb. .wa- receivers know that such is the case, but .,s pe.pn) d Th. C.rtvrv Wum Compaq. they have been prone to lay the blame City State -- on improper design or poor construc- tion.

www.americanradiohistory.com Page 832 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Uncle Sam's New Short -Wave Net MODERN (Continued from page 769) "B"Compact Buy Him One for Christmas

IPYOUwanttotuneinonCS (Complete Satisfaction) at Christ- mas get your radio enthusiast a Modern "B Compact. Improves reception, does away with "B" Bat- WHERE THE ARMY SENDS OUT ITS CALLS teries- connects to a light socket. TO THE AMATEURS The am- The interior of station 2SC; this is one of the headquarters sta- Modern "B" Compact has tions which act as liaison agents for the army. Station 2SC is ple power for sets up to six tubes. on the air every night between 7 P. M. and midnight trans- There are three B+ taps and two mitting on a wavelength of 77 meters. variable voltage controls. from regular mains If your dealer can't supply you, Signal Service Company under the direc- obtain its power the don't accept any substitute but tion of Capt. J. L. Autrey. This is without the usual fluctuating note. is applied to the sur- order direct by mail. station 2SC, designed and built by the When a voltage Signal Corps Repair Shop in Brooklyn faces of a crystal, oscillations of a fre- Price, Complete with for transmission on a wavelength of 77 quency that depend upon the thickness Raytheon Tube meters. It is a duly licensed amateur of the crystal are set up. This phenom- radio station, as are all the stations par- enon is known as the piezo-electro $30.00 ticipating in the Government's amateur action.` (EAerorTHEROCr as) network. The transmitter is housed in a With most crystal- controlled trans- The Modern Electric Mfg. Co. glass case, facilitating easy inspection mitters, the grid to filament potential is Toledo, Ohio and demonstration. Most modern ama- used to actuate the crystal; but this is teur stations are powered by "B" bat- not sufficiently steady for harmonic MODERN "B" POWER UNIT teries; this gives an unfluctuating plate operation. Consequently, a 40 -volt FOR SETE LARGER THAN Sa TUBES Uo.00 East of the Rockies voltage and, consequently, a steady plate battery is used, which greatly im- note. With transmitters as powerful proves the functioning of the device. as 2SC, however, it is not economical to The crystal is one millimeter thick, giving use "B" batteries for plate potential. oscillations of 1934 kilocycles, corre- On the other hand, fading and fluctuat- sponding to a wavelength of 155 meters. ing wavelength is usually encountered The oscillations so generated are used to when plate potential is secured from the actuate two 5-watt VT-2 tubes with the power mains. Station 2SC is unusual, associated tuning .circuits constituting however, in that it has a crystal con- the crystal oscillator. The output of the trolled transmitter; thus it is able to *Described in POPULAR RADIO, November, 1925

THE CIRCUIT DIAGRAM OF THE ARMY TRANSMITTER This drawing shows the electrical connections of the various instruments that go to make up the crystal -controlled vacuum - tube oscillator that is used for short -wave communication between the army and the amateur at station 2SC.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 833 ACTUAL SIZE BLUE PRINTS STANDARD ADMIRALTY MODEL Price $1.00 Per Set LAURENCE M. CO('KADAY has personally super..iped the preparation of Simplified Blue - Norden -Hauck Super -10 prinls Of thirteen of Po POLAR RDIO'S mOst popular eirtult0.. Each set consists of one or more Actual Sise Blueprints: flat a Panel Pat- Highest Class Receiver in the World tern: second, an Instrument Layout: and third, a Picture Wiring Diagram all simplified "The Nordern -Hauck Super -10 is an en- In the fullest sense of the word because and advanced design of Re- The 'panel Pattern can be laid on the tirely new panel and all holes drilled as Indicated. ceiver, representing what we believe to be NORDEN- HAUCK, Inc. No staling to do and so accurate there is Modern Radio no danger of ruining the panel through the finest expression of Philadelphia, U. S. A. faulty calculation. Research Engineering. In point of ex- The Instrument Layout placed on the treme range with tremendous audibility sub -base permita you to Indicate by pin- Gentlemen:- pricks the erect location of every screw. and quality of reproduction the Super -10 The Picture Wiring Diagram ghee is the best Broadcast Receiver that can be Please send me without cost or every Instrument In exact sise. and posi- built today. Wave length range adaptable tion with every wire clearly Indicated from obligation on my part, attractive one contact to the other. With no knowl- 35 meters to 3600 meters with removable illustrated literature describing the edge of radio symbole you can assemble coils." every part and complete your wiring new Norden -Hauck Super -10. with no chance of error. Mail the attached coupon today and we Set No. 4- "Cockaday 4- Cfreuu Tuner with Resistance-Coupled Amplifier" (five tubes, dis - will tell you of a host of features that place I enclose $2.00 for which please tortionlees. two dials. automatic vacuum tube t he Norden -Hauck Super-10 far in advance control, as described In the October 1924 Issue send me, postpaid, complete full size Uf competition. of POPULAR RADIO)., constructional drawings and all data Set No. 6 -"The Cockaday 8-Tube Super - Direct to heterodyne Relier Receiver" (eight tubes. two Write, Telegraph or Cable for building the Super-10. tuning Wets, loop, non -radiating. distortion - lees, as described in January 1925 issue of POPULAR RADIO). NORDEN- HAUCK, Inc. Set No. 12 -"8 -Tube Super-heterodyne tea Neme. Single Control" (as described in October 1925 lasse of POPULAR RADIO). Engineers Marine Building, Philadelphia, Pa., U. S. A. Set No. 14 -"The LC-26 Broadcast Receiver" Address. (as described in December 19251aue of PoPU- Cable Address NORHAUCK LAR RADIO), Set No. 15 -"7'he Orrhophase Receiver" (as described in the February 1928 lieue of POPULAR RADIO). Set No. 16 -"The S-C All -Ware Recefter "(as described In the March 1926 issue of POPULAR l. ONGA r' RADIO). RADIO DEALERS QUALITY PRODUCTS) Set No. 17 -"The Power -pack Amplifier "(as 7 described In the April 1926 Issue of POPULAR RADIO). Set No. 18-"The Implored Raytheon Power - Approved Parts Pack" (as described in the May, 1928, issue of Get new for POPULAR RADIO). the Set. No. 19 -"The New Home Recefrer "(three Eliminators Power Amplifiers tutee. two otages of radlo-frequeney-ampll- ficatIon with crystal detector, as described hi and June, 1926 loue of POPULAR RADIO). 1926 -27 Dongan has perfected transformers Set No. 21 -"The Improved Browning -Drake chokes of several types which are used Receive," (as described in the August, 1926, widely with UX, RCA and Raytheon Issue of POPULAR RADIO). VAN -ASHE Power Set No. 22 -"The LC -27 Broadcast Receiver" Tubes for both Eliminator and (es described in the October, 1926, issue of Amplifiers. POPULAR RADIO.) Catalogue Set No. 23 -"The LC-Sehtor Power- Pack" (as # 2568 issue of described In the November. 1928 ABC Power Unit POPULAR RADIO) Shows all the new- Set No. 24 -"The LC- In.ertnedtate Power - Designed for use Pack" (as described In the December, 1926 est parts, circuits with Raytheon issue of PoIULAR RADIO.) BH tube. Elimi- Full constructional sad parts detalle for and kits -all the nates all bat- these Receiving_ will be found In the teries. Built lato issue of POPULAR RADIO indicated. sturdy good - hard -to -get items black Back issues of POPULAR RADIO will looking be furnished st the rate of 35e copy. set -builders de- metal case. that List $17.50 I z- hourship- POPULAR RADIO mand. Power Amplifier for Home Use -good Use Dongan No. 2567 transformer half wave with UX 216 Department 124 ments -extra B -tube used In conjunction with L'X Power Amplifier tube No. 210. 627 West 43d Street, New York discounts. Mail List $10.00 Dongan transformers available for all standard types of the coupon. power Amplifier tubes. 1 Type H -Audio Transformer 124. POPULAR RADIO, Inc.. Dept. A Super-Transformer for present wave length conditions. 927 West 43d St.. New York City Unusual power and smoothness. List Date...__ $4.50 Enclosed Is my remittance of S. for FANS which kindly send me Blueprint Set (s) consisting Order these and other Dongan parts from your dealer or of Panel Pattern. Instrument Layout and Wiring send to the factory for complete information on con- Diagram as checked below: [UanAsheRadio Co. structing eliminator and power amplifier units. Set Number 4 Set Number 17 MANUFACTURERS Set Number 18 Set Number b of on the latest designe 12 Set Number 19 204NorNl0t1iSTvi¡¡ ST. LOU IS, MO. For a reliable source supply Set Number Dongan otters quantity production on all approved types. Set Number 14 Bet Number 20 For special requirements our engineering department is 15 Set Number 22 Set Number at your service. . _ Bet Numberr 16 G NNumber 23 D Set Number 24 Send Catalogue. DONGAN ELECTRIC COMPANY Name Name. MANUFACTURING 2983 -3001 Franklyn St. Detroit, Mich. Address Address CitY.,._.. Siente.

www.americanradiohistory.com Page 834 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

Accurate Primary Coupling at Every Condenser Setting with the New HAMMARLUND "AUTO- COUPLE"

From a photograph nude for POPULAR RADIO Specified ONE OF THE AMATEUR STATIONS IN THE For the New ARMY RADIO NET Hammarlund- Radio station 3X AN, operated by E. G. Raser al Trenton, N. Roberts Hi -Q J., is one of the many amateur stations that help the army to Receiver maintain communication under all conditions. Three trans- mitters are shown in this layout; 38 -meter and 76 -meter trans- mitters and a 250 -watt emergency broadcasting set is shown THE "Auto-Couple"-Ham - in the background. marlund's latest contribu- tion to radio -is a scientifi- oscillator is supplied to a tuned circuit and in parallel with inductance L-2 that cally correct arrangement of consisting of inductance L-1 with varia- consists of 7 turns of edge -wise copper Space -Wound Coil, " Midline" ble condenser C-4, of .0006 microfarads strip. The meter at the far right meas- Condenser and Aluminum Shield, capacity in parallel with it. Tuning is ures the antenna current and indicates which encloses the complete as- accomplished by adjusting the variable the correct adjustment of variable con- sembly with accompanying tube condenser until the maximum Output is denser C-5. and its socket. secured in the radio-frequency ammeter Because of the size of the tubes used, It gives automatic, graduated in the plate circuit. the filament current is supplied from the primary coupling, assuring maxi- The power amplifier consists of two power mains through a filament trans- mum transfer of energy at every VT-4B tubes in parallel. These are of former equipped with suitable smooth- broadcast wave-length and con- 50 watts capacity each, and secure their ing condensers. trolling undesirable oscillations on plate potential from a 750-volt direct The antenna system, shown on page low waves. the current generator. The relay in the 769, is a single vertical wire reaching up The "Auto-Couple" may be used plate circuit is controlled by the opera- 40 feet directly from the transmitter. in any tuned radio frequency cir- tor's transmitting key. The tuned plate The counterpoise consists of two 60 -foot cuit. circuit is adjusted to 77 meters, half that wires, 8 feet from the ground, forming a of the crystal oscillator, with For the the aid of V of 45 degrees. convenience of set- build- variable condenser ers coils, condensers and shields C-5. Resonance is Station NKF once held undisputed are sold separately. indicated by maximum deflection on the claim to the possession of the clearest antenna ammeter. and steadiest note known to short -wave The Condenser used with the On page 832 are shown the details of radio. But with the advent of 2SC and "Auto-Couple" Coil is the new the transmitter. At the far left is the its crystal -controlled transmitter Hammarlund "Midline" or "S -F- and crystal with its adjustable contact. The many amateur "B" battery- powered L" .00035 (17 plates), or any ammeter indicates other make of condenser of the the point of resonance transmitters which are independent of when same capacity rating having a condenser C-4 in the crystal oscil- power line voltage fluctuation, the short back extension shaft. lator plate circuit is correctly adjusted. wave territory, is now vibrant with The inductance in its plate circuit con- steady, clear signals. Ask Your Dealer About It. sists of seven turns of edge -wise mounted It is anticipated that the various net- Write for Folder conductor seven inches in diameter. works will play their part in the summer The tap P controls the power input to manoeuvres of the various National HAMMARLUND MFG. CO. the power amplifier. Guard and Reserve organizations. Those At the center is a filament 424 -438 W. 33rd Street, New York City voltmeter; interested may communicate with the the variable condenser at the right is in Signal Officer at the Army Corps Area 3o't. 8e#ux landi.a the plate circuit of the power amplifier headquarters in which they are located.

ammarlundPREC/5/ON A New Circuit by Kenneth Harkness In the next issue of POPULAR RAnto -for January-will be published PRODUCTS for the first time the complete constructional details of a new receiver (to be known as the KH -27) that has just been developed by an engineer who is known to experimenters throughout the rownlry.

www.americanradiohistory.com All apparalrß.advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 835

ss].31 with 5 McCullough AC Tubes and Rectron 213 wilhor i taud .Ipeaker LEAD S 'Gem TH E WAY Here is the first successful low- priced set to elim- inate "A" and "B" batteries was waiting for a set that set has won the approval of such eminent EVERYBQ4Ywould ei~lminate "A" and "B" Batteries authorities as Professor Wilcox of the Arm- without being high -priced. Here it is at our Institute of Technology, of Chicago. last. The Cleartone Radio Electric Model This set is the result of five years of exclu- 1 io, operating from the house current and receiving set manufacturing. You using no fluids or acids. And the price in- sive radio will marvel at its tone quality and volume. cluding 5 McCullough AC Tubes and Rec- by tron 213 (without loud speaker) is only And the selectivity, which is attained $231.00. What other set has such advan- two vernier dial controls is exceptionally tages at this figure? acute. The high quality of workmanship will give years of satis- Cleartone Electric Model 110 abolishes insures a set which The by a manu- the battery problem by using McCullough factory service fully guaranteed AC Tubes. They are undoubtedly the facturer of the highest standing in the radio greatest achievement in radio today. The industry. THE CLEARTONE RADIO COMPANY 2427 Gilbert Avenue Cincinnati, Ohio DEALERS Let us tell you how this set will help you do away with losses due to heavy service costs. We have some interesting facts and figures for YOU. CLEARTONE di=s

www.americanradiohistory.com Page Fah All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY If You Want to Read `pubes weaken the Code - (Continued from page 779) Ii asdobatteries secretive enough way of conversing. The foregoing applies mainly to re- l:r ylur Si-t bring in the distant sta- ception-to learning to receive in the tions you got when it was new? Is your code. Transmission on the other hand, volume as great as then? If not, look to your tubes. is naturally but the reverse of reception To keep large oarsman type tubes at highest in that rather than saying to yourself efficiency, attach a Jefferson No. 275 Tube "dah dit dit dit- that's B" when you Charger to the light socket and connect it for 10 minutes, once a month. hear those characters, you say "B- Improved reception -plus longer life of tubes that's dah dit dit dit," and then proceed and batteries -will be worth many times the to make the equivalent on the telegraph price to you. Guaranteed and made only by key. Jefferson. Get one today. Ideal Christmas Gift! Transmission is erroneously thought by a large number to be simple and easy JEFFERSON ELECTRIC to acquire, and that it naturally follows KEEP TUBES LIKE NEW-CHARGE MFG. CO. Largest manufacturen of small transformers with proficiency in reception. Not so. THEM MONTHLYandALLAT ONCE 508 So. Green St. .. ,. Chicago Acquiring a good "fist" as formation of code characters on the key is known among the profession, is a considerable $350 art in itself and one acquired only at by constant and conscientious practice. your dealers In making the characters, we are often told by instructors and text books to place fingers in a certain way in grasp - ing the key knob. Don't do it -hold the key in the most natural manner, so that an even down pressure may be maintained and so that the muscles automatically relax on the up stroke of the key. This will come natural as rson it will be the easiest "feel" to your hand. N You will learn with experience, which °25ube Charger grip answers you best and enables you to send for hours if need be with little arm and hand fatigue. Some who are in favor of the "dit J'end br Law dah" method for instruction in receiv- CHICAGO ing, do not favor it for transmission but RADIO ?íT1Thi* suggest rather that the conventional Get Tour Complete Part. ter All the Newest Cheeks Here "dot and dash" alphabet be used in every Issue of POPULAR it .\uuo and other radio from magazines you will nod the newest circuito of the Radio which to practice transmission. world's greatest radio engineers. You will want to The build these sets from the parts mentioned. BARA- writer does not hold in this. WIK service keeps up to date on all the new As it wrinkles. We have the complete parts for sa these is almost essential that reception and new circuits, complete. ready to ship you the Batteries Instant your order arrives. Take advantage of this transmission be learned together unequalled service. Get what you want- quiek- and at s big saving. No order too large or too small for not individually, the student should not us. 300.000 fans swear by BARAWIK service. SOLID We can please you, too. ONE PIECE he confused by two code charts. While Shed Ware Equipment- Special Amateur Section The Barawik line features this reason a special RUBBER CONTAINERS it is true that be sees the message he is Amateur Department in charge of F. J. Marco. owner of station 9ZA, a nationally famous radio transmitting, he does not see the dots engineer and an authority on amateur work. It presents the latest In short wave equipment, trans- Guaranteed for 2 Years and dashes that form the words of the mitting and receiving supplies and everything for unexcelled necessary for the amateur and experimenter. Spe- FA quality, guaran- message and accordingly must think cial attention has been given to short -wave kits OUS teed long-lived service and Including the B -T, Aero Coll, Silver Marshall un- ill terms of "dit dah" when transmitting R.E.L., etc. It will pay you to get our new varying dependability, Chicago Batter - Guide at once. ies offer the Radio fan an ".A" as well as receiving. Why then should Radio's Newest at Reek-Bottom Prices Power The new 1927 edition of the Barawik Catalo. t hat is backed by years of experience and l e not use the "dit dah" method for and Guide gives a comprehensive listing of the toaster workmanship with the finest I loth purposes? radio sets. parta, kits, supplies and accessories materials necessary in radio. This new Guide contains over available. Endorsed and ap- A great 0.000 items of radio's newest developments, every- proved by leading deal of assistance in learning thing that a real fan will need from the complete Radio and Automo- to factory -built set to the smallest screw, Including tive authorities. Chicago Batteries receive is not to be had from sending labor -saving devices, tools. power supply units. in amplifier equipment, etc. their new non -leak, solid rubber cases to one's self. It is difficult, and in fact Standard equipment of the represent an amazing best known manufacturers value at lowest almost impossible to increase one's at tremendous savings. east. Besides radio -peed ability by listening to one's own amateur line .there is sown PRICES selection of electrical good.. transmitting; a student following appliances. auto RADIO BATTERIES this stories seen. wallatabinstavinginoriee. Solid Rubber Cases procedure will . be greatly benefited at Write for your oft the pag Al.o please I; volts, 100 ampere hours the outset of his studies however, nameeofo her fans. Mail $ 8.79 be- the bandy coupos NOW. t; volts, 120 ampere hours 10.79 cause constant repetition of the letters ti volts, 140 ampere hours 13.50 as he transmits them will enable him SEND NO MONEY form a memory chart of the associated Buy Chicago Batteries direct from the 540 -54S Monroe St. sounds quicker than by reading from the Chicago, U. S. A. manufacturer. Batteries shipped same Mail This Coupon Novel For Free Copy day order is received. Express C. O. D. code chart and endeavoring to memorize Name or 5% discount cash with order. that "A is dit dah." Address MOGUL ELECTRIC LABS. For actual receiving practice, nothing Fan 1216 So. Peoria St. Chicago, Ill. Address is better than a good receiving set for the student gets practice on exactly

www.americanradiohistory.com RADIO LABORATORY Page 837 All apparatus advertised in this magazine has been tested and approved by POPULAR what he will expect to copy over the air. The great drawback here though is that few code transmittals nowadays take A place at a speed of less than eighteen or twenty words a minute and the sounds $7 WEEK will be but a meaningless jumble of dits and dahs to the student who has not yet acquired a reasonable proficiency. Oc- BUILDING casionally, if the student is fortunate enough to own a receiver capable of tuning to 15,000 or 20,000 meters (a RADIO SETS honey -comb set with proper coils is - in your spare time will find a few stations admirable) he of Amer- from necessity caused OIN the Radio Association which, probably ica. Learn how to build and repair by static or other interference, are send- radio sets. The Association will slowly, often repeating each train you -start you out in business if ing very a Licensed Such transmission will you wish. Be the radio "doctor" of your ing you need in preparing for word twice. upwards easily Radio Operator's examination. You much good practice, community. $3 an hour give the student made. Radio offers you a big money- receive the privilege of buying parts at and he need not feel discouraged if he making opportunity right now. wholesale prices. to make money. is not successful in copying "solid," or Earns $500 in Spare Hours You're helped Such practice as this Join the Association Now without error. ..l have at last found myself," writes the more advanced If you're interested in Radio for either pleasure applies of course, to Lyle Follick, Lansing, Michigan, "I have or profit, join the Association without delay, be- student after he has become thoroughly already made over $Soo building radio cause we have a plan whereby your membership Werner Eich- may not -need not -cost you a cent. Only a the sound of each letter, sets after working hours. of these memberships are accept- familiar with writes, "I have limited number improve his speed. For ler, Rochester, N. Y., able. Write now for details. Write before its and desires to made over $5o a week in my spare time." too late. the actual beginner, we must use differ- members are starting radio stores, This Association has prepared a beautiful book Our that gives figure -facts regarding the profit possi- ent methods. increasing their salaries, securing better bilities of the Radio Industry. the purpose of the exam- details of the Special Mem- By far the best practice for a beginner positions, passing radio operator Association, and the money for the most bership Plan. good sender transmit inations, earning big is to have some enjoyable kind of spare -time work. Mail This Coupon a buzzer or other to him by the hour with What a Membership Means practice outfit capable of imitating the FIUDIO ASSOCIATION OF AMERICA A membership in the Radio Associa- Rarenswood Ave., Chicago telegraph signals. Un- up- Dept. C -12.- -1513 sound of wireless tion of America gives you the most Send me your book and details of your fortunately, it is difficult to find among to- date and thorough training in the Special Membership Plan. one's casual friends a radio telegrapher Science of Radio. Name. You're taught how to build and repair or even a good sender in the neighbor- Address. all kinds of sets. You're given the train- City _.State.__.. hood. It is possible that we may find a Morse telegrapher in the vicinity who would be willing to do some sending, but this also is problematical. It is poor practice to have another student, the trans- Potter green as himself, attempt mission, for until he has developed the firm, precise fist of the professional teleg- Condensers rapher, he will not be able to send characters which will have the proper Build the best- sound. For example: while the letter "C" is Socket Power Devices represented on the code chart as "dah -A and B Supply Devices dit dah dit" and we know that a "dah" Power Amplifiers is a character three times the length of the "dit," yet in actual communication Impedance Amplifiers over the air professional operators place a slight slur on the first "dah" making it more like "da -ah" and which has a And are best - tendency to make the letter more dis- Filter Uses tinguishable and less jerky than were For ad- Accuratune the strict interpretation of the code Rectifiers hered to. Thus were the letter "C" By Pass sent exactly as called for, "dah dit dah Recording Dial dit" it would be the equivalent of two Itt simplicity and efficiency has Blocking D. C. together, and might lead cverwhelmed the real radio fans. letter N's run friction grip inures made of best of with a double N. Hence Its positive American to confusion absolute smooth action. materials to full capacity. All the slight drag on the first "dah" by the Graduated from 0 to 100 or professional man. This holds likewise reverse sizes and types. the letter Y- actually "dah dit Sold in three ways. with Dial $2.00 POTTER MFG. CO. but used commercially thus: Recording dah dah" (Ratio 10 to 1) Chicago, Ill. "da-ah dit dah dah." With Micrometer Control 2.75 North The student need not concern him- (Coarse ratio -and 200 to 1) .50 self with these professional formations Illuminated extra however, but learn the code exactly as Send ditect if your Dealer cannot supply you Iftwitter BY PASS AND FILTER called for and it will be found that the Mydar Radio Company slight swing that eliminates the jerki- 5 Campbell St. Newark, N. J. Condensers ness will come with experience and each "Pioneer Mfrs. of Micrometer Dials" student will develop an unconscious

www.americanradiohistory.com Page 838 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY individuality to his style of sending fdtitAttAftft peculiar only to himself. Many an old timer in the professional operating field CARTER can tell from the type of sending to "HI -OHM" Universal which he is listening just which iden- AxLE tical operator is doing the transmission. Volume Control for All Circuits Individual style is bound to develop Producen a uulfunn in any sender -it is as natural as the percent change In re- sistance. The resistance various peculiarities of feature which characteristic curve is mathematically correct make no two human beings exact for all circuits. Resist- Automatic ance element mutative counterparts of one another. pr001 and protected. In- suring long life and un- A warning is in order here however; varving electrical char- acteristics. by all means, let the style develop na- Power 500.000 ohm turally and without conscious effort on Complete ,: your part. One of the greatest 100.0000 pests with knob Control in the radio operating field is the oper- 10.000 - ator who has, by much painstaking effort acquired what he is pleased to New "Midget" term an "exclusive" fist and which is Rheostat variously referred to as the "gulf swing," ALL METAL "Great Lakes swing" or some similar moniker, depending upon which par- smallest made. Self - cooling all metal frame ticular section the operator hails from. absorbs and radiates If the beginner is handicapped by the heat. No moulded parta lack of a good to crack or break. hand sender to transmit Smooth. silent positive to him, he has recourse to a few other contact. Made In all re- methods. Phonograph records sletances.Including new are avail- Half R.MI.A, Standards. able which contain excellent code matter Size transmitted by an excellent hand 50¢ ItININATON INllKI -send- IaAR.IM er; these appear on the records CIA) P:0111:0 at vari- Both items wed in all the popular circuit. 41 1 2 ous speeds from but a few words per Any minute up to the highest commercial Yin dealer can supply speeds. Artificial static and interfer- In Cenada -Carter Radio Co.. Limited, Toronto ence is produced and the records Here is are a gift of gifts for your radilo made to sound for all the world like friends -the latest radio conye- actual radio signals through the head- nience that every set owner will phones. Such practice is excellent and a set of records should want. The Yaxley Automati c be part of the Power Control students equipment. does all the extrae Another practice switching for you. machine is available It takes care to him, and forms good practice for the FREE of your B eliminator or tricks e reason that it is the identical automatic charger or both. When you t urn transmitter by which the U. S. Radio if SIMPLIFIED your set on, the trickle charger Inspectors determine the code ability of is an applicant for off, the B eliminator is on. a radio operator's BLUE PRINTS When license. Such a machine is known you turn the set off, 1 "nu know how helpful. lnterre tine and practi- the PowerPow under the trade name of the "omni- cal POPULAR RADIO Ia. You fully appreciate Control is standing guard graph," and has that at 33.00 a year It is a real bargain. Cun- for yo u. the advantage of offer- aequently It works ing a constant change you should find it eery to convince automatically and with e of subject matter one. two or more of your Mends. who are not out fail inasmuch as the dits and dabs are cut now subscribers. of the unusual value when to turn off the B elimina any oneof theeethirteen into the periphery of aluminum dials Bets of Simplified Blue- tor and turn on the trickle charger. Prints (described on Page 1433) Is offered free which are easily interchangeable. The with their twelve month.' aubncriptlon for omnigraph also has adjustments to per- POPULAR RADIO at the regular price of 33.00. No. 444, Series Type -for use with In addition to the Blueprint, elver to your mit of any speed of transmission. friends we will allow sets with tubes having a current draw you one set free for each equal to or greater In spite of years of research and vari- new subscription you tend us with a 33.00 re- than 6 U. V.- r99 type mittancc. live new subscriptions and remit- ous devised methods, it is agreed tance of Each, $5.00 al- $15.00 would entitle you to five seta most universally that the only way in free. No. 445, Multiple Type which to obtain a mastery of the Only one set of Blueprint,. free with a renewal -for use code subscription whether with any set and especially for sets hay- characters is by constant practice. your own or a Mend's. ing tubes with a current draw lower Teaching the sub -conscious mind while than that of 6 U. V. -199 type asleep is but one POPULAR RADIO. INC., Dept. 123 tubes. of the many ways 437 west 43d Street, evolved to New York City Each, $6.00 attempt to speed up such Enclosed Is my remittance of 1. covering At your instruction, but when all is said and annual eutscriptlona for POPULAR RADIO dealer's. If he cannot supply (names on done, sheet attached). Send me set(e) check al you send his name with constant plugging, for an hour below. your order to or so daily for from five to eight months Set No. 4 Set No. 17 is required to Set No. e Set No. 18 make a good twenty-word n Set No. 12 11 Set No. 10 operator. The man who is really Set No. 14 Set No. 21 Yaxley Mfg. Set No. 15 Set No. 22 Co. intent on learning the code, will ac- Set No. IS Set No.23 Dept. P, 9 So. Clinton cept the inevitablé, buckle down to i ] Set No. 24 Street (See page 833 for description of Sete) Chicago, steady practice and not waste his time Ill. on any of the somewhat dubious Name. methods that may be suggested to him. Address Such a man will make the grade and + . Foreleg palace 80c exra. No extra for Canada. ' graduate a good operator. www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 839 t/t//ptf tt bmuieyrui a //k Marvelous New //u/iut í /ia/ll/ioli//lü'//// REMOTE CONTROL / POWER f SUPPLY with Set Control Button

Type 101X -"B Power" Supply, Raytheon Tube Type Unit operating on house lighting circuit. Three vari- able controls from 180 volte down. Has REMOTE CONTROL feature.

Plug in Trickle Charger here

Unique, Practical and an Exclusive Storad Feature! Here is the kind of Power Supply you have been waiting for -REMOTE CONTROL -the kind that is controlled with one button placed where you want it. Place your eliminator, charger and batteries where you wish -cellar, clothes Type 201AX -'B Power" Supply press, or cabinet -you do not have to touch them to turn them on or off. The and Trickle Charger control button turns off the set and eliminator and turns on the Trickle Charger Combination unit illustrated here, combines Raytheon type "B" Eliminator with Storad at the same time. Trickle Charger. Operates with REMOTE CONTROL. Interchangeable With Other Units You do not have to use all Storad Units to enjoy this REMOTE CONTROL feature. A Storad Trickle Charger will work with any make of eliminator and operate it by REMOTE CONTROL, or you can use a torad 101X "B Power" with another make Trickle Charger and enjoy the same advantages. Raytheon "B Power" 100% Over Capacity work Storad "B Power" Unite having the RF- That's why Stored Power Supply will are Raytheon MOTE CONTROL feature on any -set without hum. Stored Heavy Duty Tube Type. Stored Lrcluaive Circuit (Patent Pending). Units have ample power for UX171 Power Tobe Deutschmann Heavy Duty Condensers are used throughout. Tubes even when used on the largest seta. No More Power Worries Put a Storad on your circuit and your power worries are over. You will have current -lots of it when you want it. Stored Power Supply te the result of three years of research work and one year of actual test. Insist on Storads from your dealer or write us direct. Type 701X Trickle Charger. -. Sufficient capacity for "A" Batteries used with larger sets. Variable Control regulates charginii The Storad Manufacturing Company current from !.y to 1 amp. Has REMOTE CONTROL feature. 2417 Detroit Avenue, Cleveland, Ohio

www.americanradiohistory.com Page 840 All apparatus advertised in this magazine has been tested and approved by POPULAR Rio LABORATORY

630

WHAT READERS ASK CONDUCTED BY DAVID LAY IN justice to our regular subscribers a nominal fee of $1.00 per question is charged to non -subscribers to cover the cost of this service, and this sum must be inclosed with the letter of inquiry. Subscribers' inquiries should be limited to one question or one subject. SHIELDED SIX A Power Tube Without ever, and use a five -volt power tube such Endorsed and approved by Radio as either of those you mention, you can Broadcast, Citizens Radio Call A Storage Battery draw the filament lighting current from Book and many other prominent QUESTION: I have a five-tube, tuned - the alternating current house lighting publications and newspapers. lines through the radio-frequency receiver in medium of a small step - which I use down transformer such as is used to oper- The Shielded Six is one of the highest UX-199 tubes. types of broadcast receivers. It em- This receiver gives good ate doorbells. The transformer should bodies complete shielding of all radio results so far as distance is concerned be one which supplies five volts across the frequency and detector circuits. The secondary terminals, quality of reproduction is real -true to but the volume is insufficient and the or a six-volt trans- former may be used, with a series rheostat the ear. tone quality is poor when set is the at the point marked X in Figure 1. Behind the Shielded Six is adjusted competent for maximum volume. I have . To use this scheme engineering. It is sensitive. Day in with your receiver and day out it will get distance-on constructed one of the Raytheon Power - the wiring of the circuit should be changed the speaker. It is selective. Local packs described in POPULAR RADIO and as shown in Figure 1. The dotted lines stations in the most crowded areas show the old connections which are separate completely -yet there are but as this unit is capable of supplying oper- re- two dials to tune. moved. The filament terminals of the ating voltage for a UX -112 or UX-171 last socket are disconnected from the re- These features -its all -metal chassis power tube, I would like ceiver filament circuit and panel, its ease of assembly, and to use one of and reconnected many others -put it in the small class these tubes in the last audio stage to directly to the secondary terminals of the of ultra fine factory built sets, priced bell -ringing transformer. The improve volume and tone, if is pos- arm of the at several times the Six's cost. it potentiometer, R, which may be a stand- sible to do this without resorting The SM -630 Shielded Six Kit- includ- to the ard 400-ohm instrument, is then con- ing all specified matched and meas- use of a storage battery for the filament nected to the grounded side of the re- ured parts to build this remarkable ceiver "A" battery circuit. Separate receiver -price $95.00. supply. "B" (+) plus and "C" ( minus -FRED STROCH -) leads The 6.33 Essential Kit -contains 4 con- Will have to be provided for the power tube, densers, 4 R.F. transformers, 4 coil ANSWER: It would scarcely be practi- as mentioned above, to allow the sockets, 4 stage shields and the link higher motion -all laboratory matched -price cal to obtain the filament voltage for plate voltage to be supplied to the power $45.00. either of these power tubes from dry cells. amplifier tube and the proper grid -bias The simplest plan to follow would be ( "C" voltage) to the grid of this tube. If Clear and complete instructions, pre- to use a dry-cell power pared by S -M engineers, go with each tube (LTV-120) in your power -pack is capable of supplying kit -or will be mailed separately for the last stage. This little power tube 180 volts, the biasing voltage should be 50c. gives very good results -far better results about 40 volts if a UX -171 tube is used than a UX -199 in the last audio stage. and 12 volts with the UX -112. Best If a plate voltage of 135 volts is supplied results will be obtained with the 11X -171. to this tube the only circuit change nec- In putting the power-amplifier tube into 220 221 essary will be to bring out separate "B" operation for the first time in this circuit, (-}-) plus and "C" ( -) minus leads for turn on the receiver filament and switch this last tube. This is done as shown in on the power to the Raytheon and filament Transformers Figure 1. supply transformers. Then adjust the If you wish to go further than this, how- potentiometer R until no hum is S-M 220 -the big, husky audio trans- heard. former you hear in the finest sets - the only transformer with the rising low note characteristic that means real quality - not only on paper -but when you hear ít- $6.00. S-M 221 is an output transformer that will bring out the low notes on your pres- ent set. It eliminates blasting for practi- cally all good speak- ers- $6.00. All prices 10% higher west of the Rockies.

SILVER -MARSHALL, Inc. HOW AC IS USED ON THE POWER TUBE 841 W. Jackson Blvd. FILAMENT Chicago, U. S. A. FIGURE 1: This diagram shows the changes necessary in a two -stage amplifier to use straight alternating current on the last tube filament. The dotted Unes show the disconnected wires and the heavy black linea show the new connections.

www.americanradiohistory.com Page 841 All apparatus advertised in this magasine has been tested and approved by POPULAR RADIO LABORATORY Greater Distance r IT HOWLS Finer Selectivity doesn't! Greater Power l with ti $RD i SUPER -SENSITIVE L i UNITS INDUCTANCE MC DONALD HOWL ARRESTER, TUNED RADIO FREQUENCY KIT "ft Stops that Howl!" $12.00 Slip one of these live rubber jackets over each trouble. The Aero Coil Tuned Radio Fre- making tube .... and the Howl stops. quency Kit illustrated above will positively improve the performance Remember the name! You can get it for every size tube. of any receiver. Patented Aero It sells for 75c each. Just ask your dealer, or write. eliminates radio Coil construction Agents for the U. S. A. frequency losses and brings tre- Sole Selling U. S. A.. by the mendous improvement in volume, SPARTAN ELECTRIC CORPORATION Manufactured in the PRODUCTS CANADA, LTD. tone and selectivity. 350 West 34th Street, New York City SCIENTIFIC Kit consists of three matched units. "It Stops that Howl!" The antenna coupler has variable primary. Uses .00035 condenser. 8 page color circuit, layout and in- struction sheet for building the supersensitive, 5 tube Aero-Dyne receiver packed FREE with each WARD LEONARD LC-27 75c. each. kit. Extra copies, VIT OHM ALL PARTS IN STOCK 1- Hammarlund mid -line dual condenser, 000275 mfd 57 so 1- fiammariund mid -line single conden- ser..000275 mfd 4.65 I- Precision Duo- Octaform coil set, one antenna coupler and two Interstage couplers io . -.o 1- Amertran De Luxe Oret -stagb trans- /3 actual sir, former lo 0l1 8 1- Amertran De Luxe second -stage trans- io formerf lo fin 1- Amerchoke No. 8.54 6 0n TUNER KIT 1- Dublller No. 902 niter condenser, .4mfd 5.su LOW WAVE 1- Duhller No. 907 Alter condenser, 1 mfd .Pol units you need for 1- Mar -CO. illuminated control, scale 0 The resistor to 100 3 1;1: $12.50 2- Mar -Co small controls for LC- 27.... I I- Carter battery switch ,. 1- Samson radio- frequency choke coil No. Co m p l e t e I y interchangeable. VARION, Raytheon as 1 .. 3-Aerovox mica Axed condensers, .00025 Adapted by experts and amateurs. and AmerTran mid I 0 I- Durham resistor, 4 megohms Range 15 to 13o meters. Includes I -Lynch grid leak mounting 3. Battery Eliminators l- Carter Gem Jack three coils and base mounting, cov- 1- Carter resistance, 0- 10.000 ohms 2 nh NOT affected by moisture, 12 -Eby binding posta I .S0 ering U. S. bands, zo, 4o and 8o 5-Benjamin-- Benjamin UX sockets 3.75 continuous service or 1.10 meters. You can increase the range Mechanical Klt consisting of aluminum overload. Wire wound, vitreous enamelled sbte,ds. binding poet strip. decorated short wave tuner by secur- and 12 :,,I of this reliable resistor. panel Tait brackets ing coils No. 4 and 5. Combined (glass -like) ; the permanently zero temperature co-efficient. range of 15 to 55o meters. Both Non-inductive; LIST PRICE $85.20 coils same base Compact; easy to use; hard to break. interchangeable it or handy supply the Corbett short wave kit and All sizes you need ; separate units; We can also supplied with in various Cabinet for this receiver at $18.00 same condensers. Coil No. kits of units, totalling ti ,75o ohms use the for all approved $4.Oo; Coil No. 5, price $4.00. resistances. Recommended DEALERS 4 price A. C. and D. C. eliminators. 34 years manu- Write for wholesale prices. We are head- are available at your quarters Silver-Marshall These Aero Coils facturing of resistance as specialists. atus asrwell a 79 other lines. dealers. Gd yours today! Send for 52 page "Shure Shots" cata:og. Aero Products, Inc. Ward Leonarmectric Company SHURE RADIO CO. Dept. 104 1-19 S. Well. St. Chicago 1772 Wilson Ave. ` 7l35-af Chicago, Ill.

www.americanradiohistory.com Page 842 AU apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Sparkling in Electrolytic Rectifiers QUESTION: I am using a four-jar Making Radio Better electrolytic rectifier to charge my stor- age "B" batteries but it does not seem to function quite satisfactorily. When by SHIELDING it is in operation there is a great deal of sparkling around the aluminum elec- trode in one of the jars, while the alumi- num rods in the other jars sparkle very SHIELDING is a most impor- little but glow with a greenish tant necessity to get real phosphor - radio results today. Partial escent light of equal intensity all over shielding prevents the immersed part of the rods. Per- undesired haps this description will provide some coupling, disturbing pick -up of inkling as to local signals, increases distance, the cause of the trouble I enhances tone quality. am having. Can you help me out? The Alcoa Radio Shields are --STANLEY FANCHER especially designed for in- Aluminum excels all other metals sertion between stages or in- ANSWER: The brilliant sparkling of struments. in shielding value. The conduc- one electrode in a jar indicates that the tivity of virgin aluminum (high- jar is a "dud." If the electrodes in all of the jars sparkled more less est mass conductivity known), or violently it its easy fabrication, would be an indication that the electrodes make alumi- were too small or the load was too heavy num the cheapest, as well as the for the number of jars used. In your case best metal to use. the other three jars are working properly as indicated by the greenish glow but they Any radio receiver can be shielded are probably somewhat overloaded due to with aluminum with more elec- the failure of the first jar. It is most tro magnetic efficiency, with less likely that your trouble will be eliminated weight and more by replacing both the lead and aluminum cheaply than electrodes in the "dud" jar. Before put- with any other metal. ting in the new electrodes pour the solu- Interest at the radio tion out of the jar, wash the jar thor- Alcoa Radio Shields in the shows was so oughly, and refill with new solution. new A. C. Varian Receiver. great that we invite experts, A "dud" jar is a mysterious marketed in kit form by the thing. A Morison Electric Supply Co.. manufacturers, constructors and multi -jar rectifier may be made up from Inc., 15 Rast 40th St., New amateurs to send for the new and aluminum electrodes and lead electrodes York City. unusual treatise all cut from the same pieces, and with on this subject solution all mixed at one time. Still, when by L. M. Cockaday, E. E. Free the rectifier is put into operation it may be and the Research Engineers of found that some of the jars work perfectly the Aluminum Company of Am- while others are useless. The trouble is erica. Use the coupon below. usually due to impurities in or on the Aluminum Shields of the electrodes and the only sure cure for the can -type give total shielding bad jars is to make themup all over again, to this new Silver- Marshall using new electrodes Receiver. and a fresh solution. When one ar sparkles excessively it is not only working poorly but it puts an ALCOA added strain on the other jars, which have to carry the burden of the poor jar LC F as well as their own. ALUMINUM The "Telephone Antenna" a °D QUESTION: On page 191 of the June, TRADEMARK 1926 issue of POPULAR RADIO Only the Genuine mention Rears this dark is made of an invention that covers the use of a device to be used with an ordi- ALUMINUM COMPANY nary telephone to take the place of an OF AMERICA ordinary antenna. Some time ago, I Pittsburgh, Pa. read an article mentioning the use of a metal plate under the telephone and insulated from it by the felt. Is this the Aluminum Company of America, same idea? Room 2321, Oliver Building, Pittsburgh, Pa. -G. B. SHAWN ANSWER: The only difference is one Gentlemen: of technical construction. The principle of operation of both is the same. The small capacity of the plate to the line corre- Please send me a complimentary copy of the booklet "Aluminum Radio Shields." sponds to the small condenser in series with the lighting wires used in "wired Name wireless." The wires act as guides for the high- frequency wave. Street.. City The signal received in this way is usually not very strong except on local What Circuit do you now use' stations and any disturbance on the line may cause a noise in the receiver compar- able to of What one will you build that the station. The receiver next' should not be used on automatic tele- phones and where there is a local switch- board.

www.americanradiohistory.com Alf apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 843 Justu 30Da an

,

/ 2Díal 5eTube FEADOG,RetailPricer$470°

Yes, Sir ! -you can put a NEW 1927 Model Westingale 5 -tube Radio in your own home and use it to your heart's content on 30 DAYS' TRIAL. Entertain your family and friends. Listen to the music, concerts, sports, news, market reports from stations all over the country. Compare it with other sets for beautiful appearance- wonderful performance and low price -and if you are not convinced that Westingale gives you the greatest measure of Radio satisfaction and the best value for the money -YOU DON'T HAVE TO KEEP IT. AGENTS Big -Powerful -Dependable Wanted -Buy at Cost 5-Tube-Coast to Coast Set Don't buy any Radio until you send the coupon below Right now we want to appoint an for our FREE Catalog, which pictures and describes agent or dealer and place one demon- both the new 1 -Dial and 2 -Dial Models. Why pay strating set in each locality, because we more? Why not get the NEWEST Radio? Why will sell more take chances when all we ask is a 30 -Day Trial at know that each demonstration our risk to convince you that these NEW 1927 sets. This is your chance to get a Westingale Westingale Models are years ahead in powerful

Radio at a big discount and make it pay you big reception -wonderful loud, ' clear tone -hand- money. some appearance -and EASY, simple control? Look at these two distinctive Westingale For a limited time we offer a big reduction way Models- they're the last word in every below retail prices on the FIRST Westingale outfit way. Every late feature -every new worth -while idea is embodied in their makeup. placed in each locality. Anyone can make quick Newest style period type cabinets. Two -tone. sales and big profits in taking orders for West- hand -rubbed Walnut finish. The front panels enhanced with an artistic Spanish Galleon design ingale sets. No radio experience necessary. We embossed in dull gold. these new Westingale spare Models are unsurpassed in appearance- unbeat- show you how. $50 to $100 a week -full or able in performance -and unbeatable in price. time. Our FREE book tells all about it. Don't wait. Mail this coupon now for full par- ticulars. Get noted before you buy. Your Own Radio- -FREE Our FREE Catalog also explains a plan whereby you can put a Westingale Radio in your home on 30 Days' Trial -demonstrate it to your neighbors and friends in your spare time, and get your own set without cost before the trial period is up. Mail the coupon or a post card for our FREE Radio Catalog today. Westingale Electric Co., Be first in your locality to get special discount prices and our FREE Dept. 122 -1751 Belmont Ave., Radio offer. Chicago, Ill., U. S. A. Please send your FREE. Catalog on the New 1927 Westingale Radios. Also full particulars of your Special Discount on the first outfit placed in each locality and your FREE Radio Offer. Westingale Electric Co. Name Dept. 122 1751 Belmont Avenue, CHICAGO Address

www.americanradiohistory.com Page 844 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Volume Control for a must be inclosed on all sides with a Five -tube Receiver shield. This impression was no doubt gained as a result of the pains taken QUESTION: have av five I -tube re- in some manufactured sets to completely ceiver with two stages of tuned-radio- shield the receivers. On the other hand, frequency amplification, detector and the LC-27 Receiver, is described in the two stages of audio-frequency amplifica- October, 1926 issue of POPULAR RADIO tion. The foúr amplifier tubes operate makes use of single aluminum plates through a single rheostat and. there is a between stages as shields. If this par- second rheostat for the detector tube. tial shielding is effective in the LC-27 I have been using the amplifier rheostat receiver, why" do nmañufacturers -go- to as a volume control but this plan has so much trouble to provide complete' not been very successful because the shielding? tone quality becomes poor when -I cut -FRANK GOLDEN the volume down. Can you suggest ANSWER: The amount of shielding re- any other method of controlling the quired by any receiver depends on the volume, which will not involve too much coil 'field strengths and their distribution change in the wiring of the receiver? in each particular case. In the case of the -HAROLD TRIBTEM LC-27 Receiver only two stages of radio- Years of ANSWER: There are two ways of con - frequency amplification are used, as com- trolling the volume to better advantage pared with three and four stages ordinarily Christmas Gift Joy than the method that-you use at present. used in the manufactured receivers which Proper volume control issbest obtained in__ are shjelded: The shielding requirements Buy this for all the family -a `B" the radio-frequency amplifier circuit be- Ali the LC-27 receiver are therefore much eliminator that does away with ALL cause then the audio -frequency amplifier less stringent. Also, the type of coil used "B" batteries and gives constant, will be left working at maximum efficiency in this receiver has a much smaller ex- unvarying power to any set up to 10 at all times and the good tone quality will ternal field than does the ordinary coil. tubes using resistance, transformer or be maintained. a a impedance coupling; one that will If you insert a variable resistance, with operate power tubes, too. a maximum of anywhere from 3000 to How to Become an Amateur 10,000 ohms, in the lead running from the plate circuit of the second radio-frequency Station Operator Warren "B" tube to the 90 -volt tap of the "B" battery, QUESTION: Can you tell me what I you will find that you will have good con- must do before I can install and operate trol over volume without in any way affect- Eliminator ing the tone quality. an amateur transmitting station? I am Another and even more effective method interested in constructing a low -power 150, 90, 673 ;, 45 and 2234 volt taps is to have a separate rheostat to control transmitter, as described in the April, give correct voltage with no variable the radio-frequency tubes. Better still, 1926, issue- of POPULAR RADIO, but I resistances to worry you. Simple, take your audio-frequency tubes off the my license from compact. Free from distortion. No present rheostat, leaving this rheostat to want to obtain the expensive tubes to burn out; no dan- control the radio-frequency tubes only Government first. gerous acids. Can not blow out re- and this serves as a volume control. Put -ALFRED N. HART ceiver tubes from short circuit. Needs in a half -ampere automatic control such ANSWER: You will need an amateur little more attention than your loud as the Amperite or the Brachatat for the station license and also an amateur opera- speaker; costs less than El per year to audio-frequency tubes. The circuit changes tor's license before you can operate your use; easier to hook up than a set of that are necessary to accomplish this are transmitter. As you are a resident of New "B's ". Just plug into light socket shown in Figure 2. The dotted line in- York City you can obtain the necessary and turn on the switch -get full tone, dicates the old lead from the rheostat to forms from the Radio Supervisor of your !Rimless reception without fuss, worry the audio-frequency tubes; this must be district (2nd district) whose office is in or "B" battery expense. removed. The heavy lines show the the Customs' House, Bowling Green, New J. M. Smithson, Lacon, Ill., .aye: -"Have automatic filament control properly con- WARREN 'B' York City. He will send you application put my to every test; find it nected into the circuit of these tubes. If blanks for both of these licenses and will more than claimed. Tried cheaper and more is expensive eliminators -yours is the one to this method followed, there need be no set a date for you to appear at his office buy. Price is right; quality can't be sur- changes in the panel and the wiring passed." for a technical examination and code test. changes will be supple. The automatic The routine and examination will be the filament control may be placed in any same whether you desire to install a radio- Why Pay More Than convenient location on the baseboard of telephone or a radio telegraph transmitter. the receiver. The technical examination is not a $24.75 difficult one and consists of a series of on installation operation 135.00 and up cannot buy more less than How Much Shielding Is questions the and 124.75 cannot buy near as much. WARREN of amateur transmitters. Its purpose is to "B" costs about the same as two sets Really Necessary? demonstrate that you have sufficient "B's" and is built to last indefinitely; knowledge of enable you tronderfully well made of finest materials; QUESTION: I have been under the the subject to to beautifully finished in old gold -an elimina- impression that if shielding is to be handle your apparatus satisfactorily. The tor you will boast about and proudly show to code test consists of transmission and your friends. Shipped complete, all ready to effective it must be complete; that is, reception of Morse (American) code at tse; no extras to buy. 110 V; 60 cycle; AC. radio-frequency Unconditionally guaranteed to do more than each amplification stage the rate of 10 words per minute. claimed or money back. If dealer can't supply send coupon for immediate shipment. Refer - rnce: Central Nat'l Bank, Peoria, Ill. Warren Electric Co. Dept. 0 Peoria, Ill.

31 NY MP A SIMPLE VOLUME CONTROL FIGURE 2: This drawing shows the changes that should be made in a standard radio-frequency set in order to control volume by means of a rheostat on the first two tubes. Notice that an automatic filament DEALERS. control is added in the line that feeds the filaments of the last two tubes Write for proposition. and that an ordinary rheostat is used to control the voltage across the first two tubes of the set.

www.americanradiohistory.com AU apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 345 Build The Outstanding Circuit of the Year HENRY- LYFORD Receiver With the Deliberately Unbalanced Circuit Tt. new unbalanced tenture gives a tre- mendous Increase In sensitivity Without losing selectivity. Its high and low wave length angQe permits you to h t he North e ex- pedltlons, government statear ions and amatPole urs. tuning feature not obtainable with the aver- age circuit Complete parts care - $69.50 fully packed and fully guaranteed .

Complete as Used Parts in the LC -27 Intermediate -PACK POWER Taat I- \'axle)' A1ltimtillie Relay awl tell 444...... S 5.00 1- Flltrex A- CTraneformer, type K -180 5.25 2- Filtres Choke Colls. type K ® $575 13.50 Bridge great distances I -Any approved UX type socket .35 6-Any approved binding poets .00 1- AcracOn condenser block, 14 mfd. 11.00 1- Aeracon filter condenser, .1 mfd. 400 volts 13-C 1.00 The new PRIESS ee9" NINE brings in remote 1- Resistance Unit -type 200- 20,000 ohms total resistance. Tapped to ob- tain correct voltages 5.25 stations with astounding quality even when 1 approved high- current variable - -Any resistance to dtselpate 5 watts, - 2,000 ohms 2.00 of their broadcasting 1- Hardwood baseboard. 7Y.'x18'x54' .85 the locals are at the height 1-Bakelite binding post panel, 35í',x 4y'x3i32, drilled .50 1-Set Popular Radio blue parts 1.00 Connecting wire, screws, etc .50 1-8 ft. twisted silk lamp cord with at- Deep, sonorous bass notes as well as .40 tached plug a violin Complets Parts $47.50 the faintest sounds of - Corselet. Parts as used for LC -27 Receiver $8520 or "howls" Dealers: Write for catalog there are no "squeaks" HEINS & BOLET background noises. Instead a Wholesale and Retail -no 44 Park Place New York tone quality to marvel at. Why Because of its matchless selectivity your set the Priess Nine is ideally suited for ...... use in cities and other congested a - -. needs t.S.S ..., ..0 broadcasting districts -it goes as they IIII. MPEI4ITE 1111, through the locals though I.. one VIE were not there. The set 8.1111 for city use Fourteen years of RADIO experience Enclosed panel operated Priess set. A home loop and built -in loud are back of every speaker. A splendid pi:ce demonstration involves no obliga- of furniture in addition to its radio perfection. tion and is a guarantee of your satis- NINE TUBES give tremen- Because clear reception and faction. Write for names of dealers. dons power. Single dial necessitate control and direct reading long tube life wave length. No outside that delicate and self -ad- aerial. No lightning haz- justable control which only ard. Priess known qual- AMPERITE can give. ity and value. Eliminates band rheostats. -wiring. Simplifies set 6) RDI IARM, Accepted as the only perfect filament control in every ll RAutL)Illllll N 11 N E popular construction set. S 9 Price $1.10 Complete FREE 'Write for "The Radial! Book. "containing the latest popu- "Outstanding radio performance and value lar hook-ups and construction data. to Dept. P. R. -12. on the market today - without exception" dial) eompasy PRIESS RADIO CORPORATION ,4 Qn uaa 688 Broadway, New York 50 MANKLINST.. NEW YORK

Authorized Pries: Dealers show this sign in their windoas Table model $195 : he "SELF ADJUSTING "Rhcattat

www.americanradiohistory.com Pave S 16 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

The obverse of the medal; this original is too- and-one -half inches in diameter. The Popular Radio And Now Medal for Conspicuous Service The Bass Note Circuit every radio amateur to every ama- TOteur experimenter and broadcast lis- tener, who is instrumental in alleviating in a 2-Dial Hook-up human suffering or saving human life, directly through the medium of radio, CLEARER than ever -even more selective -and always that recognition will hereafter be extended in crystal purity of tone -from highest soprano down to deepest, the form of a medal that shall be known richest bass. The same astonishing Daven Bass-Note Cir- as "The Popular Radio Medal for Con- cuit -with new refinement added. spicuous Service." This medal is unique within the realms of radio in that it shall For instance, two tuning dials only-instead of the usually he awarded, not for scientific achievement accepted three. A Radio Frequency choke coil that prevents the or invention, but for service to humanity. radio waves from entering the audio amplifier. A special compensat- ing condenser that increases selectivity, especially in long- distance To insure a fair and unbiased consideration of tuning. And a brand new layout, requiring less base space and a all claims, a Committee of Awards has been ap- smaller, neater panel. pointed that includes five distinguished citizens of international fame. To aasiet this Committee of Awards, an Advisory Committee has been ap- READ "HOW TO BUILD THE BASS -NOTE CIRCUIT" pointed that numbers among its members some A new book that tells you in the simplest, clearest manner of the moat eminent citizens of the United States, including representatives of many of our most dis- how to make yourself a Daven Bass Note Receiver. A wiring tinguished institutions. diagram of an altogether new type shows you quickly how to as- The conditions under which the medal will be semble the parts. Even a boy can follow it clearly. awarded are here specified: 25c per copy at any Daven Dealer's -or 30e by mail. And it's 1. The medal shall be known as the Popular worth ten times that in the new kind of radio reception it will help Radio Medal for Conspicuous Service. you obtain. Get your copy now -while the edition is plentiful 2. The medal shall be awarded, without discrimi- - nation as to sex, age, race, nationality, color or later on you might have to wait for another printing. creed. to thaw radio amateurs. radio experi- menters, broadcast listeners and other non- professionals through whaee prompt and effi- cient action radio is utilised to perform an essen- tial part in the alleviation of human suffering or in the saving of human life within the terri- torial confine. of the United States and its pos- sessions, or in the waters thereof. DAVE 3. The medal shall be awarded by a Committee of Awards that shall not exceed five in num- ber. No member of this Committee shall be an employee, officer or stockholder of Porous RADIO, Ism., nor shall any such employee, BASS NOTE CIRCUIT officer or stockholder have a vote in the de- liberations of the Committee. 4. An advisory Committee, which shall cooperate for COMPLETE Radio Reception with the Committee of Awards and which shall be particularly charged with the responsibility Daven Catalog Free on Request of making recommendations for awards of this medal, shall be made up of men and women who, because of their interest in the public welfare or because of their connection with institutions that are consecrated to public service. are in positions to bring to the attention of the Com- mittee of Awards the exploits of candidates who D.I l "E.Y OLA.STOR DATER NI- DUTY OLASTOR are within their own special fields of activity. the e ' Transparent Resistor, Rperiatly designed 5. The medal will be awarded for services rendered for B- Elimfn since Enduring, noiseless, changeless. afore. Will carry the highest cur. Armistice Day, November 11, 1918. Complete range of resistances. rents knot.. to radio. o. Recommendations for awards may be submitted to the Committee of Awards at any time and by any person. Every recommendation must contain the full name and address of the candi- date, together with a detailed account of the NEW 8th EDITION DAVEN accomplishment on which the proposed award is MANUAL based. and must be accompanied by corrobora- This valuable Book explains tory evidence from persona who have first -hand (aven Amplification in full de- ' n a v È H'r R A D l o' \cO,kPAitAt,dW knowledge of the circumstances and whose tail, and shows hate to apply it statements may be verified to the satisfaction of . ..,,. to your set. 25c at dealers. 30., ., 1Pe.rr'/ov47eAia/:/.r ...seo the Committee of Awards. by mail. 152 SUMMIT ST., NEWARK, N. J. 7. The medal will be awarded to as many indi- viduals as qualify for it and at such times as the Committee of Awards may authorise.

www.americanradiohistory.com 111 apparatus advertised in Mis magazine has been tested and approved by POPULAR RADIO LABORATORY Page 897 V14 Ide THE NEARLY PERFECT TRANSFORMER *P+

The reverse; the name of each recipient will be engraved in the space provided.

S. All considerations not specified herein shall be left to the discretion of the Committee of Awards. Every note .. naturally .. which AU communication. to the Commiase of Awards may be addressed to- The Secretary of the Committee of Awards, Pore - LAR RADIO Medal for Conspicuous Service, 627 the ear can hear! West 43rd Street, New York. Are you permitting your transformers to censor your The Committee of Awards reception ? Are they cutting out those low base notes of the baseviol or the kettledrum? Are they giving proper HIRAM PERCY MAXIM, President of the American Radio Relay League. amplification to the high notes of the piccolo and the E. F.IW. ALEXANDER8ON, Chief Consulting Engineer of the Radio Corporation of America. human voice ? MAJOR GENERAL CHARLES McK. SALTEMAN, Chief Signal Officer of the Army. REAR ADMIRAL W. A. Morrarr, Chief of the Bu- Here is an opportunity for you to get every note to reau of Aeronautics, U. S. Nam'. DR. JOHN H. FINLEY, publicist and Journalist. which you are naturally entitled. Whether you are using Secretary: Dr. E. E. Free, 627 West 43rd Street, New York. a cone or a diaphragm type speaker, Ferranti Trans- formers are suitable. Ask your dealer about Ferranti. Advisory Committee If he does not handle it, write us and we will let you know who does. SENATOR JAMES W. WADSWORTH, JR., of New York. HON. JOHN BARTON PAYNE, Chairman, American FERRANTI, INCORPORATED, 13o W. 42nd St., New York, N. Y Red Cross. ADOLPH LEWISORN, Publicist. JUDGE BEN S. LINDSAY, of the Juvenile and Family Court, Denver, Col. DR. J. MCKEEN CAT-YELL, Past President, Ameri- can Associationf the Advancement ofScience. DR. J. H. DELLINaER, Past President, Institute of Radio Engineers. FARLEY OSGOOD, Past President, American Institute FERRANTI of Electrical Engineers. C. E. GRUNSEY, Paet President, American Society of Civil Engineers. DR. DArroN C. MILLER, President, The American TRANSFORMER Physical Society. W. L. AnnoTT, President, the American Society of Mechanical Engineers. HIGHSPOTS W. J. HOLLAND, President, Carnegie Itero Fund Commission. High amplification ratio For the best avail- GEORGE K. BURGESS, Director, Bureau of Stand- with flat curve. ards. Ferranti brings out the fun. able transformer re- COLIN H. LIVINGSTONE, Past President, Boy Scouts elemental frequency of of America. low tones -none are sults - Ferranti DANIEL C. BEARD, Chairman, National Court of beard merely by Honor, Boy Scouts of America. inference from higher Audio Frequency SARAH LOUISE ARNOLD, President, MISS Girl harmonics. Transformer A.F. 3 Stouts. Every transformer tested DR. W. D. HAGGARD, President, American Medical ten times -all shoe.crt- -ratio 3,Ií to I- Association. cuit turns eliminated. K. A. BICKEL, President, United Press Association. Built by an established SS12. KENT COOPER, General Manager, the Associated manufacturing company Press. with forty years' expe- DAVIS, Vice Westinghouse H. P. -President, Electric rience in the winding of it Manufacturing Company. wire For a transformer DR. VERNON KELLOGG, General Secretary, National coils of fine for Research Council. electrical instruments far superior to the and meters. JESSE LYNCH WILLIAMS, Past President, Authors' use Fer- League of America. Windings have high average, PROFESSOR GEOnoR B. Punt/at, Dean of the Faculty impede nee. ranti A. F. 4 -ratio of Applied Science, Columbia University. Primary shunted with PROFESSOR H. H. SHELDON, Professor of Physics, built-in condenser of 3!í to 1 _.$8.50. New York University. correct capacity. Woe. HAWLEY ATWELL, Grand Exalted Ruler, Order Tested to two volts bet- of Elks. ween primary and sec. PROFESSOR EDWIN B. WILSON, Harmed University, ondary and between National Academy of Science. primary and secondary W. E. HARKNESS, Vice- President, American Tele- and ground phone et Telegraph Company. WILLIAM L. SAUNDERS, President, United Engi- neering Societies. Cot. J. R. NIcQUIOO, Commander, the American 441 Legion. aCJ JOHN R. Moss, President, Eiwania International. THE NEARLY PERFEC RANSFORMER W. D. TERRELL, Chief Supervisor of Radio. Depart- ment of Commerce, Washington, D. C. ri1D1

www.americanradiohistory.com Page 848 .111 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LASORATORV Scientifically Built PIER CE A1In® IN LABORATORIES Complete Assembly THE WORLD'S CONDUCTED BY DR. E. E. Fftl:r: for a Six Tube -Coupled The Use of Radio as an Aid to evidence to prove that radio has any Resistance Vegetable Growth effect at all. The most careful investigation ever WILLIAM BooT, SINGLE MR. of Nottingham, made of these matters was conducted, radio an- DIAL England, erected miniature over a period of eight years, by scientists Receiver over his plants and pro- tennas tomato attached to the United States Depart- duced, so the story rums, the most ment of Agriculture. The results have enormous yields of tomatoes ever ob- been published recently.* Plants of be- tained in his neighborhood. Thus various kinds were grown under a wire gins a story which has gone the rounds network kept charged to a high poten- American newspapers of British and tial. "These experiments do not show," the past few weeks and which during the authors report, "any well -defined has been interpreted as indicating that increase in yield due to electrical treat- mysterious electric energies pulled down ment." out of the ether by a radio antenna have It remains barely conceivable that some remarkably stimulating effect on electric effects of some kind do exist the growth of plants. but are too obscure to be readily per- It is too bad that this is not true. The ceived; certainly there can be no such who his back radio fan decorates yard clear effect as Mr. Boot's experiences with assorted antennas might better would indicate. Probably what hap- the objections of his anti - withstand pened in his case was that some other if he could maintain Front and Interior Panel Viea radio relatives that factor became effective at the same time all those wires was good the presence of that the radio wires were installed over for family garden. Although elec- Build your own set with the his garden. tric currents, such as would be supplied Pierce -Airo Complete As- "Electroeulture. ' by Lyman J. Briggs, A. B. sembly. Save time and by a generator or a battery, have been Campbell, It. H. Heald and L. H. Flint. Bulletin found, in a few experiments stimu- No. 1379, U. S. Department of Agriculture, 34 money. You will possess page., 1926. For sale by Superintendent of Docu- one of the best receivers lating to plant growth, there is no ments, Washington, D. C., price 10 cents. possible to obtain. Audio stage is resistance -cou- pled giving finer tone. Pierce -Airo is a mechani- cally and electrically per- fect product, perfected by United Scientific engi- neers and assures distor- tionless amplification combined with single dial control the two big fea- tures in radio this season. Ask the nearest radio dealer to show you Pierce - Airo TO -DAY.

Pierce -Afro Complete Price Only Assembly with a 7 x 18 Processed Bakelite Panel. Ready for Wiring. '4250

United Underwood & Underwood Scientific Laboratories, Inc. A DELUSION OF RADIO'S RELATION TO PLANTS Mrs. Lulu F. Mc.Manis, an "electronic" practitioner of Kirksville, 80 Fourth Ave., New York Missouri, is reported to believe that radio waves related to the famous "electronic reactions" will measure the arming power of bean seeds. Scientists generally regard this as a mistaken idea.

www.americanradiohistory.com by POPULAR RADIO LABORATORY Page 849 AU apparatus advertised in this magazine has been tested and approved

* YOU CAN BUILD THE NEW SHIELDED H 1- Q

The Hammarlund- Roberts Board of Engineers The Hammarlund-Roberts HI -Q Receiver Is the Joint creation of ten leading engineers. A wealth of experience plus highest reputation for quality warts guarantee unexcelled perfor- mance. Benjamin electric Mfg. Co. Caner Radio Company Durham Resistors Eby Manufacturing e'o_ Hammarlund Mfg. Company Martin- Copeland Co. Radiall- Company (Amperite) (Samson Electric Co. Bangamo Electric Co. Westinghouse Means. ûver5Z000/Ju/lIatlfome You Can Do It Too LAST year 57,453 radio lovers had the fun of building the Hammarlund- Roberts Receiver at home -a wonderful tribute to the genius of America's ten leading engineers who designed this remarkable instrument. The new Hi -Q Receiver is even more wlipderful than our set of last year. A study of its modern features will disclose simple dual tuning, Complete Shielding, Automatic Variable Coupling, high detection efficiency, high power output and utter absence Automatic Variable Coupling of oscillation. A wonderful new feature. Same control oper- ates both tuning condenser and primary colt Hi -Q Receiver will prove that coupling. This gives maximum and equal am- An inspection of any home -built pllpcation and selectivity over entire tuning 5 equal 8. Actual test will prove a range. here for the first time tubes sensitivity equal to that of expensive "Supers." Reception is startling both in distance and power; volume is full and all signals have those rich, undistorted tone qualities which fall like a caress on the most sensitive ear. Save $50 to $100-Build It Yourself When over 57,000 novices have built successful Roberts Re- ceivers, you can build one, too. Send 25c for the "How to Build It" Book or get a copy from your dealer. Follow the simple di- rections, solder a few connections and in a few hours you, too, will have the satisfaction of having built one of the world's finest "How to Build It" Book receivers at less than half the price of factory -made sets not Written by the Hammarlund-Roberts Board of Engineers in very simple A B t' language. nearly so good. Every detail described. numbered and Iia- grammed so that you Cell easily understand It. Send 25c for your copy. (j'Iâmmarlund HiQ aHlhgth ratio f reactance to resistance. The Hi -Q Foundation Set High ratio -Great xelecttvlty-T.oud signals. Tbe'Key to thin wonderful receiver. includes drilled and engraved panel. and euh- panel and all the essentials required to start bilding. Broadway,NewYork Price $10.50. HAMMARLUND-ROBERTS,1182-B

www.americanradiohistory.com RlCf 8500 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY ierlin$ Be Protected Against The Alleged Effect of Radio RADIO Se¢ >trl'n$ Waves on Pigeons theCommonAilments RADIO THE power of homing pigeons INSPECTORS CARE TAKERS to find their way back to the proper dove cote of Radio Reception! in spite of distance and all other ob- stacles is one of .the most mysterious . NO set is so good that it can continue to en- phenomena of Natiue. Equally re- tertain satisfactorily night after night markable is the ability of the migratory Pochet Meier without some servicing and inspection on your part. birds to make long journeys twice a year and yet to return year after year To make it easy to the for every set owner to give the same locality receiver the care it deserves, Sterling Á iBßGry[7 at either end. Many has pro- ó zoologists Pew: 'Viet, duced complete Care-Taking and Inspection have puzzled over these facts Equipment. and no one has been able to formulate a These devices for keeping your batteries and satisfactory theory to account for them. tubes in healthy condition, for locating troubles, The latest attempts to do so have and for promoting better reception, should be a been made in France and involve No.R23 -22g part of your radio NoR-9 aovib/+afinq an filament Meter equipment. essentially mystical TyZlatteryrger effort to relate these abilities of the birds to Write for our helpful literature or see radio waves.* your nearest dealer. The pigeon is supposed to possess some direction- finding apparatus with which such No R -33 The Sterling Mfg. Company waves are perceived or with which Charge Indicator Cleveland, Ohio it is possible to follow the magnetic field of the earth. Advocates of these ideas go so far, even, as to imagine the pigeon's human owner sending out from his body radio waves which the pigeon can perceive and follow at dis- tances of a NoR -403 Trlbq thousand miles. One of the Reactivate advocates of this viewpoint2 cites the famous-and thoroughly exploded - "electronic reactions" of Abrams in support of his contention. It ought to be needless to point out No.R-4oG Unh'eTal Ka R-us tridpel that there is not the slightest real evi- TubeTeyter 7hbeliYroctit6ter dence for these ideas, nor are they even plausible. Dr. Lakhowsky asserts that homing pigeons cannot fiy successfully in the neighborhood of large radio trans- Have You Tubes mitting stations but no convincing evi- You Can't dence is cited that this is true. The way Rejuvenate? in which the pigeon finds his direction is The AETNA TUBE RE- ACTIVATOR often a very real problem which makes efficient tubes of old worn -out ones which greatly ordinary "tune rejuvenators" have been unable deserves intensive scientific work. to revive. This is possible because the AETNA But employs an entirely different method of re-thori- it will do no good to indulge stlon, as in fancies explained below. about The AETNA RE- ACTIVATOR soon pays for PHONE the supposed relations of radio itself by bringing worn -out tubes back to life PLUG MILLIAMMETER and eliminating the necessity of buying new ones waves, "human" or otherwise, to the matter.

*"The Origin of Life, of Radiation and of Living Beings" (in French), by Georges Lakhowsky, Paris. 1926. Borne suggestions are reviewed (with- out approval) by the distinguished scientist Dr. Cb. Maurain in Le Nature (Paris), number 2728, pages 44-45 (July 17, 1926). r' Radiations and Life" (in French). by Jules Regnault. Radio- Electririd (Paris), Volume 7, pages 273 -274 (July 25, 1926).

A New Material for Making Condensers This precision, moving coil instru- THE usual method of constructing ment is made to plug into the loud fixed condensers of metal sheets separ- All the so- called "rejuvenators" on the marke ated by paper today heat the filament by passing a small speaker lead on your set and enables or some other insulator is amount of current through It. The AETNA abandoned TUBE RE-ACTIVATOR heats the Filament at you to adjust your C- battery bias on in a new condenser described a slow, even temperature, and in addition bakes recently the tube externally, which redeposits on the the power tube, for perfect reproduc- to the French Academy of mament some of the thorium that has been driven Sciences onto the side of the glass by use. tion. Instantly attached. A neces- by M. Albert Nodon.* The The shell surrounding the tube is essentially a sary accessory material used is a colloidal solution miniature oven. containing a patented element if you desire the ut- of that furnishes the heat for this purpose. most in quality. oxide of iron in glycerine. This is ab- Works on either 1)-C or A-(' Current. sorbed in the pores of canvas or other Ask your dealer or send us $5.00 for prompt sMO Price -$8.50 mew. If not fully .sdilvJled offer week's total return heavy cloth and is placed between to us for refund. Senator Catalog "Hoyt Meters for Radio" metal plates, preferably of aluminum, Aetna Machine Mfg. Co. which form the terminals. 426 S. Clinton St. BURTON - ROGERS CO. BOSTON. MASS. *Repotted to the Academy at the session of May Chicago 25, 1926. Described in L'Industrie Electrique Saks Dept. for Hoyt Eleetriml In.druntent Co. (Paris), Volume 35, pages 332 -333 (July 25, 1925): also in La Nature (Paria), number 2729. page 60 (July 24, 1926).

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 851 Colloidal solutions consist of very tiny particles of one substance, in this instance the oxide of iron, suspended in another substance. What apparently happens in Nodon's condenser is that Neglect each one of the billions of tiny iron Don't particles acts as an individual condenser plate, the dielectric being supplied by this Vital the glycerine in which these particles are suspended. The capacities obtained Point are very high. Quite modest dimensions for the parts give capacities measured in of thousands of microfarads. However, the charge leaks away in a small fraction of Contact! a second, so the condensers are useful only for high- frequency work. They are suggested for telephone condensers. Whether they have been tried impor- AFEW spare moments, a screw driver, and you have tantly in radio work does not appear. sure, perfect connection between your aerial and lead -in wiry No noise, no soldering, no loss of "distance" due to swinging aerial New Measurements of Radio Intensities or corrosion. Tip -Top cannot work loose. TEE measurements of long -wave radio intensities and of the intensities of Jobbers and Dealers, write us! atmospherics which are made regularly by the United States Bureau of Stand- ards, in Washington, have recently been 25c reported, for 1925, by Dr. Austin.' The JAMES F. DOOLAN results show no very startling depart- MANUFACTURING CORPORATION Eliminates ures from those of previous years. The 36 -42 West 47th St., NewYork Antenna methods used have been compared dur- Noise ing the year with those used for similar purposes by the Radio Corporation of America and by the Bell Telephone Laboratories. The agreement between the different methods proved satis- factory. The 2 Biggest Bargains The familiar Austin -Cohen formula for calculating the intensity of the field DAST received at a given distance and for a FamousxNESSKits given frequency has been modified slightly to bring it more exactly in Better than Ever B ttr,y accord with the whole mass of data now HARKNESS 3 -tube Kit. Most extraor- accumulated. The modification affects dinary outfit of its Bice made. Equals any ordinary 5-tube set. A wizard for distance. + the exponential term e-n. The value of unexcelled in tone quality, 'Complete parts. u is now taken as 4.57 X 10-ód X f".s ONLY $36.00 d is the distance in kilometers and f is the frequency in kilocycles. Contrary to the usual impression of observers on broadcast wavelengths, the Two -Year NEW Guarantee intensity of the atmospheric disturb- Bond LOW ances in 1925 was somewhat less than in in Writing PRICES 1924. This applies, of course, only to Famous the world over for raj- v v enduring performance Solid Rubber Case the long wavelength tested; namely, Another Winner >,lid Rubber Case lasting pro Radio sanen ,,ction against acid or leakage. 6-Volt, 166 -Ampara 12,500 meters. As before, the prevailing $10.00 The Improved 5 -Tube Approved and Listed as 6-Volt, leo- Amoeree direction for atmospherics in summer, at Single Dial Tuning by Leading $12.00 Standard '.volt. 140- Ampare' Washington, is from the southeast, A truly remarkable set, whfch will do every- Authorities $13.00 thing the moat critical fan could demand. including Radio News Labor- Solid Rubber Case which Dr. Austin suggests may mean "a mplicity itself in operation, the lent word in atories, Popular Sci. Inst. Auto Batteries - t ne quality, volume and selectivity. Standards, Pop. Radio Labor- s Volt 11 Plate origin in eastern South America or in 610.00 Complete parte and atories, Radio Broadcast Lab- 8Volt, I3 -Plate Africa. In winter the prevailing direc- Kit simplified instructions 7.50 oratories, Radio in the Home 612.06 and Lefax, Inc. 12 -Volt r - Plat. 814.60 tion is from the southwest, probably the Chassis speal cabinet $55.00 in cabinet, m Send No Money highlands of Mexico. !62.50 set your radlodlalaat Set shown Just state number wanted and for the is in accord," says Austin, we same day order is WorldlStor Storage_ "This Dr. These prices are list. will ship Station WSBC. Dealers -write for received, by express C.O.D. Pay "with the idea that disturbances gen- Jobbers and -alwaysa ways lntere.ttne. attractive discounts. expressman after examining erally originate over land and are most batteries. 5% discount for cash Jerry Sullivan. FREE -A epecial 16 -page Harkness Book with order. Remember, you and Announcer intense in the afternoon and evening in with e mplete illustrations, diagrams, save 59% on World Batteries et c., will he ,,,. hd ,n request. - a. r the regions where the sun passes very so send your order today. BATTERY COMPANY nearly overhead." WORLD THE RADIO GUILD Inc. Dept. 3 "Long Distance Radio Receiving Measure- 1219 S. Wabash Ave. Chicago, III. ments and Atmospheric Disturbances at the Bureau of Standard, in 1925," by L. W. Austin. Journal 241 Market St., Newark, N. J. of the Washington Academy of Sciences (Baltimore, Md.), Volume 16, pages 398 -408 (August 19, 1925).

www.americanradiohistory.com Page 852 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY E1+++++++++++++++++++++++++13 - + -. } T + + The + + + + + + + Intermediate + + + + Power Pack + + + + + + Iil ,+F p'ÿ:l. a ' + + i + +} + + + + + + + + + + + + + + Designed + + + to operate the + l'oderwoel s Underwood + + + TESTING GLASS FOR RADIO -FREQUENCY + LC -27 Receiver + CONDUCTIVITY + + carried + and other + Professor Louise S. McDowell, of Wellesley College, recently + + out, at the Bureau of Standards, tests of the conductivity of different + kinds of glass for radio -frequency currents. A glass plate is floated on + power tube sets + more quicksilver, held in + + liquid quicksilver. On top of the glass is In develo in the Intermediate } place by a copper ring. The glass thus forms the insulator of a con- + Power Pack, MgCockMr. Cockaday ffeels I thatha denser, to which different voltages were applied at frequencies between + + was he has at last Pproduced a B Power + 1000 and 1,000,000 cycles. The power loss in the glass found Supply that is past the experimental to increase markedly at high temperatures, even at the temperature + 1 +} of boiling water. .}, Givingg a constant, uniform current + + of 180 volts at 60 mils. without dis- } lines in the usual way may be seriously + + Special Maps for Radio Use tortion or hum, the Intermediate wrong. It is necessary to take this into + + forgotten, + Power Pack will operate any power } THE fact, too commonly account, Mr. Keen urges, in studying + set. The special 40 volt C bias is + of radio waves + P that the true paths directional radio effects, the direction of + ample for the UX 171 tu bc VVoltage 1 + between one station and another are not taps arc the same as those on standard static and similar problems. + by laying a ruler on a + B batteries. + indicated correctly There are two cures. One is to use a + + is emphasized by Mr. R. Keen, There are no liquids9 or moving + map, globe rather than a flat map. This is engineer, in a recent parts. After being connectedd to your + a British electrical undoubtedly the best procedure if a set, no furtherf attention is necessary. + waves follow the i arficle.e Radio good globe is available. The idea of the 4. Operation cost is less than one -third + rounded surface of the earth. In the T of a cent per hour. i facts thus obtained is far more vivid T absence of disturbances they presum- You can build the Intermediate T than the idea that one gets from a map. {, follow what mariners call a "great ,c, Power Pack in two hours, ready for + ably other cure is to plot out on a map being the The operation, it has been made so simple circle" course, the great circle the directions which great -circle paths and easy to assemble.bl + which can be drawn on the ' shortest line would really take between the stations !l the sphere connecting _ + surface of earth's in which you are interested. These _ No Antenna + thereon. On a globe this is _ + two points will seldom be straight lines. Necessary i perfectly clear. A circle so drawn gives 4. A uniqueV feature of the Intermediate the direct path of the waves correctly 4'' Power Pack is a means providedded in thet e A Carbon -Dust Micropnone .. unit for dispensing with the antenna on a 1' and shows the correct direction of the men- Neutrodyne or any type of(T Tuned edR R. F + THE Reisz microphone, much + Receiver. wave for each of the two stations. tioned recently in radio news from + + But on flat maps things are very dif- Germany, is described in a recent + List of Parts + ferent. In order to represent the curved British patent issued on the device.* + as Used in the Laboratory model + surface of the earth on a flat surface it K -180 $5 ?5 The active material is a layer of fine + 1 Mitresa AC Transformer. t'type + 2 tree Choke ['olio, type K, at 56. 5 13.50 + is necessary, as is well -known, to dis- carbon (coal is mentioned) held 1Ña- A Id Socket, typeYPe48\ L X . I n + dust of + 6 Eby binding pposts fa, tort the shapes and positions of the con- and a i membrane .} 1 Acracon condenserd block,oe 14 m fd 11 fN + between a rubber aeon filter .1 m fd ., 400 of "pro- + 1 Acr condenser, tinents, making some variety of marble. Electrical contact is + volta DC + block H.k". A 1.. tappedppe resistance 5.2s jection" of the real land surface onto the with layer of coal dust by + 1 Central ub Resistance type>Oe 200. 20,- made the + 000 ohms 2.002 011 flat sheet of paper. Mercator's projec- at its + HardwoodH baseboard walnut finish. means of two metal electrodes 1 post panel,1 drilled .50 commonest one used + 1 Bakelite binding + tion, probably the sides. The sound waves are allowed 1 Set Popular Radio blueprints an d con - } structional bookleth kI 1fNl i, on ordinary maps, distorts the polar against the thin rubber dia- + cewtslte connection wire screws. etc. . 0 to beat cord with plug .40 and is exactly accurate ,,+ 1 8 ft. twisted silk lamp + regions greatly phragm, through which they act on 242.50 only at the line of the equator. the layer of coal dust, causing this + 1 Yaxley Automaticatic Relay. Switch No. + + 444 + For small areas, like a city or a to be alternately compressed and re- + + of real shapes and + your drain rann« nippbi you. send cheek or + county, the distortion The microphonic action is + leased. + directions thus pi duced is not impor- evidently the same as in the old carbon B Power Supply + The departure of the real land + Filtrex + tant. microphone, one of the familiar instru- Aver l'awk also, 4, The Intermediate l' + surface from flatness is not great enough y built complete and encased in a beautiful + ments of the early days of telephony. blue. long 4, metal case, finished in Duco midnight + to do harm. But when distances Although much has been claimed for the 4. Guaranteed against mechanical defects. + be off on maps, as they must ,t. Approved by Popular Radin Laboratory. + must laid distortionless qualities of this micro- Dealer, writ e bit- informer, n + in considering radio transmission, the + phone, the principle now disclosed does direction obtained by drawing straight not seem very promising. ,+, CONNER CROUSE CORP. i+, *"Maps and Wireless Wave.," by R. Keen. 'British Patent No. 250,430, filed June 25, 1925. 52 Vanderbilt Avenue, New York + Noted in The Wireless World (London), vol. 1A, + The Wireless World (London), Volume 19, pages tl+++++++++++++++++++++++++El 73-76 (July 21, 1926). page 888 (June 30, 1926).

www.americanradiohistory.com Page 853 All apparatus advertised in this magazine has been tested and approved br POPULAR RADIO LABORATORY Modernize your set QUALITY BEYOND BELIEF WITH with a scientific OWERIZER

Combined `13" Eliminator and Power Amplifier POWERIZED radio reception is so true --so faithful, that the radio entertainers are literally trans- MAIL ported into your own home. Such remarkable reception up to this time has been offered only in the most expensive new Super-Power SAAL Ec- centric Cone o sets. Now YOU can have it by Showing the new SAAL Eo merely attaching a Powerizer to construction in cones. your present set, a centric at the cost of Stylus is scientifically placed SIPIEÀK1E Ifs "B" eliminator alone. Ask the at the umbo of eccentricity nearest Powerizer dealer to dem- togive proportional vibrating areas fot both high and low improvement in radio this year onstrate it TODAY. tones. Cone measures 20 In- The greatest ches in diameter and repro- is the improvement in speakers. In SAAL, RADIO RECEPTOR CO. duces all tones whether the 106 Seventh Ave- New York set is equipped with or with- speakers have been developed to do justice out power amplifier. Price, $25. Junior Model, $15. to the finest radio receivers. All prices slightly higher west of the Rockies. Furthermore, the tone chamber and vi- brating area of SAAL speakers -horn, cone, and pedestal -are scientifically shaped for sound reproduction. The new Ec- centric Cone is different. Its stylus is "off center." Just as the harp and piano have short and long strings for high and low notes respectively, the Ec- centric cone provides a short and long radius ex- SAAL Horn No. 5 to give proper vibrating area for both The broad polished bell is of tremes of sound. This cone reproduces all Ir116111111111" 11111. non -warping Bakelite, the goose neck of cast aluminum tones equally well, without loss of low notes, in crackle gold finish. The horn has no metallic reso- or over - accentuation of high notes. And nance and is guaranteed not or barrel tone. to blast or chatter. Standard completely prevents drum equipment for radio engi- neers in laboratory work. In Horns, SAAL has always been stand- Price $22.50. ard. SAAL Soft Speaker No. 5 is the latest and most popular SAAL Horn ever offered. It requires no adjustments and no additional power for quality reception. It will give 100% satisfaction regardless of the set or equipment with which it is used. The SAAL Pedestal is an ornament to the most beautiful surroundings. Its pure wooden tone chamber, three feet in length, gives exceptionally clear mellow reception. The Pedestal is designed for those who Approved by prefer the tone quality of horn reproduc- tion in a drawing room piece. Keeps the

A Genuine Solder speaker away from the set and eliminates Cl Ilt'AGO SOLDERCOMVA NY harmonics. MICIEVAIMINIn SAAL Pedestal Modernize your set with one of these Tones rise through the 3 -foot wooden tone chamber and scientific SAAL Soft Speakers and get the 5.17 Uhl., emerge from both front and fullest return from radio now. back of the top, hence non - directional. The top is level with your ear when you are seated tuning in. American H. G. SAAL COMPANY walnut finish with inlaid de- sign. Price $38. 1800 Montrose Ave., Chicago, U. S. A.

WORLD FAMOUS MAKERS OF HORNS CONES PEDESTALS

www.americanradiohistory.com Page 854 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

Has c, 0

-- '/\ V

SINGLE CONDENSER A combination straight line wave length and frequency condenser of improved design specially built for those who appreciate fine reception. Capacity .00035 List Price, $3.00

nm Proteeeor óanford'e"Bulletin." RECORDS OF SUDDEN EARTH ELECTRIFICATION The solid line shows the average charge, from the records of Professor DOUBLE CONDENSER Fernando Sanford, al Palo Alto, California, for nine disturbed days in 192,5. The dotted line is the normal course of the earth charge, on un- combination straight line wave disturbed days. The sudden drop of the solid line in the forenoon indi- length and frequency condenser. Each cates the enormous increase of negative charge which the earth receives section capacity .o035. List Price on the disturbed days and which must have significant effects on $6.áo. radio. The cause of this curious phenomenon is unknown. RECOMMENDED BY POPULAR Disturbances of suddenly received an RADIO AND LAWRENCE M. Earth enormous addition of free electrons. This was COCKADAY FOR THE LC-27 CIR- Electricity not accom- panied, in general, by CUIT. THAT the earth usually possesses any marked or a sudden change negative electric charge which in the electric potential com- of the air. Most monly varies during the twenty -four curiously of all, these sudden disturbances hours in a more or less regular manner almost always be- gan in the forenoon, has already been described in POPULAR usually between eight and ten A. M. RADIO, together with some of the pos- It is difficult sible effects which these terrestrial to imagine a cause for these events and electric disturbances have on radio Professor Sanford refrains from transmission and reception.* At several suggesting any. The changes are observing stations in different parts not due to the so -called of magnetic the earth the hour -by -hour variations storms which occasionally sweep across the of the earth's electric potential are earth, causing unusual variations in the direction measured and recorded throughout the of the com- year. pass needle or in the intensity of the earth's magnetic field. One of these stations is at Stanford It is a charac- teristic of these University, California, where Professor magnetic storms that they begin all over Fernando Sanford, heads a terrestrial the earth at the same time. They are believed, electric observatory in which such therefore, to records are kept continuously, be caused by something outside the day and earth, presumably night, by means of recording apparatus. by magnetic dis- turbances in the sun. Since In the most recent report of this obser- Professor TRIPLE CONDENSER Sanford's disturbances of vatory Professor Sanford records a earth charge begin at almost the same hour of the The one condenser exclusively recom- series of curious disturbances of the clock at Palo Alto they mended by Mr. E. M. Sargent for the earth's electric charge which occurred must have either INFRA -DYNE Circuit. some local cause or some The low on nine days included among the days relation to the dielectric losses, exact capacities and elevation of the sun above the horizon mechanical perfection of this conden- in 1925 for which satisfactory records of at that time. - ser makes it the logical choice for one the earth charge are available. f It is impossible to imagine dial receivers of the better class. The characteristic thing about these that the Straight line wave length and sudden increase of the fre- nine disturbed days is that the earth's negative charge quency -Each section capacity .o35 on the earth in potential suddenly showed a marked this fashion would be -List price $9.50. without its effects on radio change toward the negative, as though transmission or reception. Comparative IF YOUR DEALER CAN'T the surface of the soil at Palo Alto had records of SUPPLY YOU. WRITE DIRECT radio conditions have not been kept and ;'Earth Electricity; Does it Affect Radio Recep- probably are not available tion?" Poert.ea RADIO for June. 1926; pages from amateur 111 -113 and 180-181. logs or other sources, since the onset of Gardner & Hepburn, Inc. t "Summary of Observations of Earth Potential, Air-Potential Gradients, and Earth the electric disturbances is 611 Widener Bide., Philadelphia; Pa. Currents for the at an hour Year, 1925," Bulletin of the Terrestrial Electric. when little radio broadcasting would Observatory of Fernando Sanford, Volume 3, 24 be pages, Palo Alto, California. July. 1926. in progress on the Pacific Coast

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 855

ii..t im ' ". rield 303 AtkinsNs Ave. soec;atth in CorMaday Kits S.. HAMMER RADIO CO . Brooklyn, New York Cockaday Sets Now Made Easier to Build by Our New "Ready -to- Wire" Plan 50% of Your Time, Work and Worry SAVED ! All you need do is to connect bus -bar according to diagram, solder and your set is finished. These Kits are sent to you completely mounted, and assembled on a Veneered Mahogany baseboard and genuine bakelite panel, drilled and engraved. Genuine parts used as listed below; exactly as used in Mr. Cockaday's Laboratory Model. COMPARE OUR OFFER! LC -27 BROADCAST RECEIVER !SENIOR AND INTERMEDIATE POWER PACKS 1 Hanuuarlund zdd -Flue dual r° alemier, 1 Samson radio-frequency choke cull* e5 .. $1.50 .000275 mfd i 7.51) 3 Aerovux, mica axed condensers. .00025 I Hammarlund mid -line shytic rundenser, mfd 1.05 .000275 mfd 4.65 I Durham or Daven Resistor 4 meg .50 1 Precision Duo- Octotorm coil set commis- I Lynch Grid Leak Mounting .35 Ing one antenna coupler and two Inter- 1 Carter Gem Jack .25 stage couplers 10.50 1 Carter variable resistance, 0- 10,000 ohms 2.011 I Amertran De Luxe first stage transformer 10.00 12 Eby binding posts 1. SO 1 Amertran De Luxe second -stage trans- 5 Benjamin I/X Sockets 3.75 former 10.00 1 Amperlte No. l 1.10 1 Amerchoke 8854 6.00 Mechanical Kit ¡consisting of aluminum 1 Dublller or Tobe 4 mfd. Filter condenser 5.50 shields. binding poet strip, decorated panel 1 Dublaer filter condenser, .1 mfd .60 and Tait brackets 12.511 1 Mar -Co Illuminated control, scale 0 to 100 3.50 2 Mar-Co small controls scale 6 to 50 and 1.50 READY -TO -WIRE KIT PRICE $85.20 1 Carter Battery Switch .65 LC -27 INTERMEDIATE POWER PACK I Yaxley Automatic Relay Switch No. 444 $5.00 1 Hardwood uaseboard. 7' ' x 18' x )4' $.85 1 }litres A-C Transformer, type K- ISO.... 5.25 I Bakelite panel, 344' x 4I,' s 3/32'. drilled .50 2 Flltrex Choke Coll[, type K. at $6.75.... 13.50 I Set POPULAR RADII) blueprints .. 1.00 1 Na-Md UN type socket .35 Connecting wire. screws. etc.... .5o 6 Eby binding poste .90 1 8 ft. twisted silk cord with attached plug .40 1 Acracon condenser block, 14 mfd 11.00 I Aeracon filter condenser, .1 mfd 1.00 - Right here! 1 Resistance !ilt -type 200 5.25 COMPLETE KIT PRICE ;47.50 1 Centrals° high current variable resistance 200 COMPLETE KIT OF PARTS FOR LC -27 SENIOR POWER PACK ;65.20 You can't go wrong when you use Polymet High Voltage Condensers in sers or power units. Built to withstand t,000 volts permanently, and individually I I Six I Completely Wired Sets Silver Shielded tested for this rating, their obvious superiority. both In Stock Now Kits In Stock Now in workmanship and performance, definitely establishes Polymet's leadership as condenser manufacturen. WE GIVE SERVICE AND GUARANTEE THE OPERATION OF ANY LC -27 KIT OR SET PURCHASED FROM US Write for our interesting special circular which we have prepared on the LC -27 Receiver and also catalogue. Do it now. Authorized service station for the LC-27. DEALERS: WRITE FOR SPECIAL DISCOUNTS

Polymer condensen incorporate finest insulating paper, best foil and specially prepared impregnating compounds. An exclusive, new and improved process renders them non. inductive, with high dielectric re- sistance for long life. ObtainaF'r as individual units or in blocks; in cans or unmounted; with fixed or flexible leads. Capacities .1 to S. Mfd. . 60e to $4.50

Shielded Tuned Radio Transformer, No. 30 POLYMET Raytheon sines coin [$*[* not e 1000 Circuit cawB.ure SICKLES Blocks Diamond -Weave Coils 'l'he new Sickles Shielded Tuned Radio Transformer prevents both outside and local interfer- ence. It is remarkably com- Tested by the Raytheon Laboratories, they have pact, sharp-tuning, sturdy. passed with highest honors and been given an envi- able rating. Sickles Diamond -Weave Coils F1001 .1-C-.1 Mfd. . . $2.00 have established an enviable F1000 14 Mfd. . . . . 0.50 reputation for low distributed capacity, low dielectric losses, Polymer Products are used by over ray high grade receiver and power it manufacturers. There's and large range of frequency reason -Polymet Products have passed their exhaus- with small variable capacity. tive tests! Follow the manufacturers- specify Polymer The ideal coil for the Na -Aid Local- Products-at all good dealen everywhere. ised Control Tuning Unit and the cR Type for Na -Aid Truphon& Assembly. Ilhatrated descriptwnt sent FREE on reggest. There are Sickles Diamond -Weave Every Radio Coils for all leading circuits. Polymet Manufacturing Corporation Need 599 -C Broadway - New York City THE F. W. SICKLES CO. "World's (aryra Afanuf «urea of Radio Emrntial.' 134 UNION STREET Write for data sheet of the SPRINGFIELD :: MASS. Complete CeCo Line No. Coil Prices 30 Shielded Transformer $2.00 each POLYMET 24 Browning Drake 7.50 set C. E. MFG. CO., Inc. 18A Roberta Circuit 8.00 set Providence, R. I. 25 Aristocrat Circuit 8.00 set IIIIIlIIIIIIIIIIIIIIHIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

www.americanradiohistory.com Page 856 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY The Effect of Temperature COCKA DAY/ on Signal Strength (Continued from page 765) greater insulating power than warm LC-27 PANELS air, a difference which is reinforced by the greater dryness of the cold air. It is As used by Mr. Cockaday possible, also, that the ions of the cold in his original Laboratory Model air are enough sparser than in the warm air to produce a difference in the loss suffered by radio waves in traversing it. These ions in the air are believed to

QE.C.ryt V OLamr be swung back and forth, you remem- ber, by every radio wave which passes through the atmosphere. High up in the air, in the region of the famous Heaviside Layer, the ions are so far apart that most radio waves cannot swing them widely enough for neigh- boring ions to collide with each other. Near the surface of the ground, where Mounting Is All YOU Need to Do the air atoms are very close together, We cut, drill and engrave the LC -27 Panel, especially for use the few of them that are ionized are in the Cockaday Receiver. This genuine bakelite panel and its much more likely to knock against each exquisite decorations are guaranteed to be impervious to mois- other, when the waves swing them. A ture. The LC -27 Panel will not warp or otherwise lose its considerable loss of energy from radio waves is believed to be due to this col- shape, no matter how long it remains in service, while $ 00 the lustre of its finish lasts indefinitely. lision of the swinging ions. This is why 9- so much energy is lost by a departing Also the Improved BROWNING -DRAKE Panels $ 50 radio wave just after it leaves the an- in stock, ready for Use. tenna, before it can traverse the lower part of the air and reach the Heaviside CORTLANDT PANEL ENGRAVING CO. region along which it usually travels with very little loss. 79 Cortlandt Street New York City It is conceivable that the tendency of dry, cold air to contain fewer ions than moist warm air may make it a better transmitting medium for radio, so that less loss is experienced on dry, cold -RADIO FANS- Console Cabinets days. But this is not certain, for the ,ou are interested in se- without sets ionization of the air is not dependent 1 curing the very best prices on temperature alone nor can we be on all the new, improved KNOCK- absolutely sure that the loss of energy DOWN KITS for the following re- ceivers- due to ionic collisions in the lower air is the chief loss which radio waves suf- fer, even over the comparatively short LC-27 distances which Dr. Austin's tests refer New and improved to. BROWNING -DRAKE 5 Tube Another group of possible causes con- DAVEN BASS NOTE 5 Tube cerns the upper levels of the air. Ordi- narily,the circulation of the atmosphere, S -M SHIELDED "6" with all of its winds and storms and LC SENIOR POWER PACK cold waves and other changes of tem- KARAS EQUIMATIC perature, is confined to the lower fifteen New Improved or twenty miles. Above this turbulent HAMMARLUND- ROBERTS Hi -Q zone, sounding balloons have shown the of SAMSON T -C 5 Tube existence a relatively quiet layer of air which meteorologists call the "strato- REMLER INFRADYNE 10 Tube These beautiful Console Cabinets have Genuine Walnut 5 ply selected stock for tops, sides as well sphere." The air in this stratosphere RAYTHEON B SUPPLY; AMER- as upper and lower front doors. The legs and minor is very thin and light, being so high POWER parts are selected gum. All finished with genuine TRAN PACK lacquer, hand rubbed, furniture finish. above the earth. It has a temperature and These cabinets are designed to accommodate a nearly constant at about seventy de- all the latest types of A and B elim- radio set, charger, batteries and accessories. grees below zero, Fahrenheit. inators and loud speakers- Cabinet can be had with or without grill or horn. It No. txo cabinets without grill or horn compart- lies, however, well below, in level, those Write to us ment will take a set with panel up to 7x28 -ro' deep. Our price 13t.50. No. tss cabinet with uppermost levels of all, which are sup- before you buy! Frill improved natural tone horn of very good qual- posed to be highly electrified, to carry ity will take receiving set with panel up to 7zX2!5. Remember: All our knockdown kits Our price $34.30 the radio waves and to constitute the are guaranteed to consist of all parts Transportation charges extra. Heaviside Layer. used by original designers. Specify size panel of your set. We can furnish Utah or Burns Units at additional We do not know exactly how far such J and M Radio Co. cost. disturbances as cold waves extend up- Send for catalog showing regular cabinets, Hi-Boy Consoles, Radio Tables and Radio Benches. ward into these stata of the atmosphere. 88 Walker St. One theory of the winter storms so UTILITY RADIO CABINET COMPANY New York City 448 -27th Street .. o Milwaukee, Wis. common in North America and in Europe considers them due to masses of

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page h 57 cold air which slide down from the polar regions and mix slowly but violently with the warmer air of the temperate regions and of the semi- tropics. If this is a true picture of a cold wave, that wave probably extends well up toward the lower surface of the supposedly un- It disturbed stratosphere. It. may even force this lower surface into an upward top bulge or draw it down into a valley. Whether such storms in the lower air can ever reach high enough to affect the Heaviside region, even ever so slightly, we do not know. It would be rash to state that this effect is by any means an impossibility. The truth is, it will be apparent, that we know too little, as yet, about the real nature of the upper levels of our atmosphere to be able to say much about' what does happen in them or about the effects which such things as cold waves and hot spells have on these upper levels. Exploration of the upper air, above ten miles or so from the earth, is difficult and slow. If the tem- perature effects which Dr. Austin finds, originate, as is quite possible, within these higher stories of our earth's attic, it may be some time before we are able to interpret them fully or with assurance. 5 Indeed, it is more than possible that Complete we shall learn new facts about the up- with tube per air from our radio studies, rather than interpreting radio studies by aid of our knowledge of the upper air. Sound- Last quarter -eight minutes to play -score tied - ing balloons will rise only some twenty your favorite has the ball on opponent's twenty or twenty-five miles. Radio waves go like much higher; at least as high as the yard line -first down -ten yards to go -looks Heaviside region, a level hopelessly a touchdown inaccessible to man or to balloons, al- Broadcasting coming in fine-play by play -and though possibly reachable by Professor away. Tubes are not lit -"A" Goddard's suggested explosive rocket. then, it fades Radio investigations like that of Dr. Battery is out -run down. Austin on temperature effects, are likely This cannot happen to those who use the to tell us more of the nature of the upper air and of the effects of surface weather on it than any other scientific pro- cedure that has been advanced and carried out. Meanwhile, the practical conclusion F ßúTÓnáriéN is that the air temperature has a dis- tinct relation to thy signal strength with which radio is transmitted over distances CHARGER in the neighborhood of 150 miles. Much has been done already in correlating This device keeps the "A" Bat- radio reception with the weather, as tery fully charged at all times several recent articles in POPULAR RADIO have described. The tempera- An absolute necessity -fool proof and dependable ture relation discovered by Dr. Austin in every respect. Equipped with a Tungar Rectify- is another fact useful in the same con- ing Tube which supplies a steady charging current nection. to the "A" Battery when the set is not in use. It will not be long, one may imagine, When the radio is in operation the charger is dis- unti! the prediction of radio conditions connected by means of an automatic relay. for a few hours or days in advance will CONNECTION to pre- No LIQUIDS USED -"B" ELIMINATOR be just as possible as it is now Only dict rain or hurricanes or other outstand- Sold by Authorized Freshman Dealers features of the weather. The pos- Write for our new 48 -page book illustrating and describing the ing other apparatus sibility of such forecasts of radio con- entire line of Freshman Masterpiece_Receivers and ditions throughout the world would be the listening radio FRESHMAN CO., Inc. a.. great boon to CHAS. Bldg., CHICAGO public as well as to the commercial Freshman Bldg., NEW YORK -2626 W. Washington companies that handle traffic.

www.americanradiohistory.com Page h5S .411 apparatus advertised in this magazine has been tested and approved by POPOLAR RADIO LABORATORY STOP! Don't Work Without Pay SAVE 100;, OF YOUR TIME AND WORRY Buy any of the RECEIVERS listed below 100% READY -TO -WIRE at BEST MARKET the VERY PAT NO MORE oui-sSRVicS u MAR 100% READY -TO -WIRE RECEIV- ER than you would pay to others for the KNOCKDOWN kit of PARTS.

!FREE! Healy Maier Our PROPOSITION to the Con- RADIO PROGRAMS PRINTED FUR THE BLIND Kumers, known as the GUARAN- The Braille system of printing in raised letters that may be read by TEED - MONEY - SAVER will be touch is employed by the State Institution for the Blind in Berlin, for mailed FREE upon request. enabling the sightless to follow the broadcast features. This blind girl -1f- is mailing the programs to those similarly afflicted. YOU are interested to SAVE TIME and WORRY on any of the latest advertised POPULAR RADIO or other well known RECEIVERS, and POWER -PACKS as listed below, BROADCAST LISTENER WRITE for our PROPOSITION which GUARANTEES you the Comments on the radio programs, methods and technique UTMOST SAVINGS -from the point of view of the average fan An entirely new idea makes it posai- ble for anyone to build the most complicated receiver with factory By RAYMOND FRANCIS YATES Standard Receivers, Cone type Loud- When the Broadcast Studio sity, and grandeur; we can all but feel speakers, A and B-Battery Eliminat- There ors, also Knockdown Receivers and Is Not Needed our presence in a great theatre. Power-Packs at I,, vest ni the country is an unescapable realism to it. It prices. EVERY careful listener can distin- sounds as though the music were being guish the difference between music played in a big, spacious auditorium. Our 100% Ready -to- broadcast from a studio and music Surely, we would not care to experience Wire Receivers and broadcast from a place outside the the illusion that this grand orchestra was Power Packs studio. playing right in our own 12 by 24 living There is to the latter an unmistak- room; that would be a destructive sen- L -C -27-Cockaday Samson T -C- De -Lux able "hollowness" and reverberation. sation. We want to be transmitted to Improved Browning -Drake To overcome this, acoustic engineers the scene and not to have the scene Karas Equomatic have gone to great effort in building brought to us. And that is just what a New Henry Lyford Hammarlund- Roberts Hi -Q studios with cork -covered walls, heavy prepared studio does not do with the DAVEN BASS NOTE carpeted floors and sumptuous draper- larger orchestras. The music sounds Remler Infradyne ies. These devices are used to kill the "cramped;" there is a "deadness" to it Silver Marshall Shielded Six reflection of sound which, the wiseacres that creates an impression of detach- Diamond of the Air sound L- C- Senior Power Pack claim, is a destructive factor in repro- ment; it may be too perfect to L-C- Intermediate Power Pack duction; it is claimed further that per- true. General -Radio Power Pack fection of tone and "naturalness" is pos- In the case of trios and instrumental Raytheon B- Supply Power Pack sible only from a studio built on the solos, perhaps this "studio effect" is principle of a padded cell. desirable, but we are doubtful. We !REMEMBER! That an engineer should claim that would much rather listen to the dinner That all Standard Receivers we perfect pick -up comes only from a place music of WEAF transmitted from the sell are GUARANTEED to be GENUINE'and as REPRESENTED, of this sort is strictly an engineer's busi- dining room of the Waldorf-Astoria IN we also guarantee OUR 100% ness and that we should differ with him, than to an ensemble from a padded cell. in READY -TO -WIRE RECEIVERS to even though it may betray gross ignor- In the latter case, the illusion of "space," be composed of the exact same ance on our part, is strictly our own of being present in a huge dining room, IN parta as used in the laboratory model used by Mr. Cockaday and business. Be that as it may, that's ex- is evidence and that to us is realism. other designers. actly what we are going to do. This Even in this prejudiced frame of -WRITE TODAY- hollowness and reverberation, this dia- mind, we can more than dimly appre- You will only have yourself to blame, bolical "sound reflection" if you will, ciate the technical difficulties involved If you don't write us at once your adds a touch of realism which to us is in transmitting from small studios. To name. necessary to create a perfect illusion. turn an orchestra loose in a small, un- Consumers Service Co. It may be bad engineering; it may be prepared room would be nothing short ('O- OPERATIVE ASS'N bad acoustics. But we like it. It's of a musical tragedy. That is patent.

Direct Buyers for the Consumer natural . It's real. The solution to the whole problem 263 -67 East 24th Street In listening to the Capitol Grand seems to lie in using enormous studios Paterson, N. J. Symphony Orchestra, there is conveyed with carefully regulated acoustical to us with the music a sense of immen- properties. In such a place, a good

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 859

LC -27 KITS AMPLION DRAGON SEND YOUR ORDER IN TODAY! AR19 $42.5o

Parts exactly as used by author in the LC -27 Broadcast Receiver 1- Hammarland mid -line dual condenser. .000275 mid ... $7.511 I- Hammarlund mid -Une single conden- ser.000275 mfd 4.65 1- Precision Dun- Octaform coil set. one antenna coupler and two Interatage couplers 10.50 t- Amertran De Luxe first -otage trans- former 10.00 I- Amertran De Luxe second -stage trans- former 10.00 1- Amerchoke No. 854 6.00 DublllerNo.902 Alter condenser. .4 mid 5.50 1- 1 1- Dublller No. 907 niter condenser. 1 mfd .60 I- Mar-Co Illuminated control, scale 0 1 to 100 3.50 2- Mar-Co small controlo for LC- 27 1.50 .s The most comprehen t -Caver battery switch .65 1- Samson radio-frequency choke coil No. live line of radio re- 85 1.50 3- Aerovox mica Axed condensers. .00025 ti f producersrod in the world mid 1.05 1- Durham resistor. 4 megohms .50 I -Lynch grid leak mounting .35 1-- Carter Gem Jack .25 ! 18 Y i --- itt+t. J'ti_,.... L:_ $[,J: AMPLION 1-Carter resistance. 0- 10.000 ohms 2.00 AMPLION --, 12 -Eby binding poets... 1.811 PATRICIAN 5- Benjamin UX sockets 3.75 CONE 1- Amperlte 1.10 ACI2 $30 AA18 345 Mechanical Kit consisting of aluminum shields, binding poet strip. decorated panel and Tait brackets 12.550 Complete ....$Ó5.2U COMPLETE PARTS FORE 1750 Amplion reproduces the LC INTERMEDIATE POWER PACK 4 Send Money order For immediate delivery entire musical scale ctv with absolute fidelity ,t matter what set you have, you Z l; ,, Stows -no 110 West 42nd Street, New York need an Amplion to bring out its best Downtown Store :: 79 Cortlandt Street THE Amplion Patrician assembles a 48" air - column with the matchless Amplion repro- 221/2v. $2.65 ducing unit in a richly carved mahogany cabinet, 18" x 12" x 9". The Patrician is non - E directional and is notable for the pleasant, V of its tone. U E soft mellowness N R The Amplion Cone is totally different in principle from A L type of reproducer. Its especial superiority lies in A any cone C S its clear, clean -cut reproduction of speech. I T The Amplion Dragon is used as a standard of compari- D I over world. N son in radio experimental laboratories all the G To any radio enthusiast no gift could be more acceptable than an Amplion. Prices range from $12 to $45. "HAWLEY" NEW TYPE Ask your dealer for a demonstration or write to us for interesting Amplion Booklet. 45 volts 95.25, 90 volts $10.00, 1 volts 912.50, 135 volts $14.75, 1575? volts $16.80. 180 volts $19.20. Includes chemical. Noth- ing to purchase extra. Special sises to OF AMERICA order. Family recharged upon any current THE AMPLION CORPORATION including 32 volt systems. Any special de- tector voltage easily had. Operates any 1 to Suite X, 280 Madison Avenue, New York City 10 tube set. Tested and approved by leading authorities, such as Popular Radio Labora- From 1887 A path of brilliant achievement to 1927 tories, etc. Over 4 years sold on a non -red- tape 30 day trial offer with complete refund if not thoroughly satisfied. Further guar- anteed 2 year. Knock -down kits at still greater savings. Complete "Hawley" "B" Battery charger $2.75 Order direct -same day shipments, shipped C.O.D. -simply pay expressman cost on delivery or write for my free literature, testimonials, etc, B. HAWLEY SMITH AMPLION 315 Washington Ave., Danbury, Conn.

www.americanradiohistory.com Page 860 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY soprano could sing with an acoustical background that would give her voice every opportunity to reach its fullest NEW U. X. UNIVERSAL beauty. It is true that the better artists feel annoyingly strange when singing FITS ALL TUBES gore in studios for the first time. They miss that sensation experienced in large wer. auditoriums. "Itgets Some day, perhaps our larger broad- that casters will be able to afford great aud- last itoriums from which to broadcast. To our way of thinking, it will be a great GRID mile" day for radio when they are.

What "Chain Broadcasting" SOCKET Promises to the Fan THE haywire broadcasters, it seems, Because They introduce a minimum of grid - are rapidly coming to the ends of their plate capacity and aid in preventing ropes, which means that within the next objectionable feedback is the reason Mr. John B. Brennan, Tech. Ed. Radio year broadcasting will shake off a,num- Broadcast gives (in November issue) for selecting Airgape for the new four tube 7i,pe ber of its grotesque performers and R. B. Lab. Circuit which contains many settle down into a respectable source of refinements brought forward by the 200A manufacturers of the 1927 season and entertainment years of development work by Mr. Keith The work of consolidating some of the Henney director of Broadcast Laboratory. P OW F_ R better studios has begun; perhaps before At all dealers or direct 60c. this comment has appeared in print, the AIRGAP PRODUCTS CO., Mfr. F. I F.0 1OR WJZ-WEAF chains will have been 11 Campbell St., - Newark, N. J. i brought together into one great system. OWER -and more of it And this is but one of the changes that E THAI GP'9 - that's the biggest thing will occur. WPG, WIP and WGBS in the tube field today! Son - are to be incorporated into a chain, and atron's famous power tubes plans, to say nothing of wires, are being Electrically and are giving new life to thou- laid to bring together other good micro- Mechanically Perfect sands of sets -and new en- phones. joyment to thousands of set The passing of the smaller trans- owners. The very next thing mitting stations will be accomplished you should do is to buy this painlessly and quietly, for the public remarkable power detector will naturally forsake them for the co- -and hear the amazing operative programs offered by the chain improvement in reception stations. It will not only be a matter Sheet Copper which it brings! It's one of a of the survival of the fittest but the family of 25 distinct types passing of a strictly detrimental factor. - The smaller studios cannot, or at least for the world's largest tube line ! they have not, been able to attract the Shielding SONATRON -ize your set! better performers nor can they afford real artists the type of transmission that they are justified in demanding. Their presence on the air has done nothing but Shielding increase interference and lower the gen- eral standard of broadcasting. Prevents aerial radia- Chains of capable stations, on the tion and feedback. other hand, hold out great promise for The higher quality in programs. It is reason- Insulates against in- Sonatron Amplifier able to assume that three to twenty terference from adjoin- -teak 3 'Red, White and Blue stations in a chain can afford, by pool- Matched Power Tubes ing their resources, both technical and ing circuits. Adds three stages of amplification financial, to hire better artists and by to any set, Improves efficiency, even a crystal. One con- so doing to avoid much of the banal nection, made in a moment, and you selectivity and have this source of amazing power stuff that now finds its way to the air. tone and tone. Adds beauty to your set, It seems that the day of the ham radio quality. and makes your batteries last longer. performer is coming to an end. For dry-cell or storage battery sets, $20 complete. At your dealer's. USE SHEET COPPER

OVATION TURI CO- Cak.n. N.wr.d. Nur.rL N. J. De,.. Have You a Pet Radio because it combines low Windsor. Om.C...4 "Uncle ?" resistance with easy work- IF you are much of a listener you've ing qualities. ONATROr probably heard one of the many air. n Ca:). .e "Uncles" on the 4dustÙ.J,near Vuau.treey If you haven't, we don't know how COPPER & BRASS RESEARCH ASSOCIATION .Jaarueer, el the WORLD'S LARGEST TUBE LINE you have managed to escape them. There's "Uncle Robert," "Uncle 25 Broadway - New York Henry, ", "Uncle Gee- Bee," (a dear old

www.americanradiohistory.com Page 861 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY soul) "Uncle Walt" and many, many Uncle Whosits. These men are much given to the use of the word "kiddie" and when the announcers say that the next Build This Set fifteen minutes are to be devoted to the kiddies with dear old Uncle Jack at the of Merit! microphone, you are supposed to capitu- the Standard late to the spirit of the occasion and For more than a year and a half the adjust yourself to Mother Goose and Diamond of the Air has been a favorite the "Story of the Grey Horsey." That with fans. It works on loop or indoor puts you down as a big- hearted Gus or outdoor aerial. making sacrifices in the interests of the kiddies. (Note the human appeal in Licensed under Armstrong Patent 1.113.149. that word ?) tianufactured by Clapp-East ham Co. Just the other day, at the POPULAR exclusively for the Bruno Radio Corp'a RADIo Laboratory, we tuned in on Complete Kit of Parts, with Uncle Robert (WHN). Uncle Bob, Blue Print, Ready to Wire, as "as his little wards fondly call him," by Herman Bernard is one of the greatest kiddie -kar Specified papas in radiodom. Uncle Robert always comes to the studio with a corps of his "little charges" who sing and $37.50 recite for you -providing you are willing. $ Personally we were not willing. Far 3N from it. No sooner had Uncle Robert's "little charges" broken into (and Simplicity, Efficiency and Beauty "broken into" are the right words) one we were a little of their songs than o" speck disappearing in the direction of The Bruno Unitune The name Unitune stands for something new and beauti- the 42nd Street Ferry. actuate two Bruno bakelite intelligently ful in radio -two drums that Really, there is only one shaft straight line frequency condensers, the circuit managed kiddie broadcast that we know being completely assembled and mounted on a frame. A of and that is the Sunday morning period bronze panel plate goes with the unit, used for all the put on by WJZ. That station, contrary popular circuits. to the accepted laws of broadcast- ing, does not employ an Uncle. Its announcers simply read from the funny papers and broadcast music that might appeal to the juvenile imagination. WJZ has exploded the Uncle theory Price and still it manages to attract the atten- tion of thousands of youngsters. $17" A Rare Treat of Old -time Minstrelsy MODEL RF IF you want to spend a pleasant Sun- some time, get the old UNITUNE Model 2C day evening This basic instrument consists of two bakelite shaft of condensers (.0005 mfd. jimmy pipe out and tune in to one the Bruno strsignt line frequency "BRUNO 99" 3 -city. unless otherwise specified), mounted on an aluminum cuit Tuner. wound on minstrels broadcast by WGBS. After two drums, with frame; a bronze panel plate and t luartrite glass and listening to several of them, this de- scale. The condensers are insulated from each other. .specified in the Dia- $11.00 mond of the Air. partment is willing to testify before a UNITUNE Model CC Covers Broadcast band to the effect Consists of one .0005 mfd. bakelite shaft. straight and brings efficiency Congressional Committee line frequency condenser and a three circuit tuner to any circuit. It that WGBS is putting on a series of on one frame, with regular Bruno drum control. mounts with single Price $12.00 hole minstrel shows worth anybody's cigar UNITUNE Model RF $5.50 Consists of the basic condenser frame, Model 2C, store coupons. This and two Bruno LOW LOSS RF transformers. "BRUNO 99 "- Matched R. F. Coil for the 99 you have been in the habit of listen - combination provides two radio frequency stages If Pore. Tuner. Used in the Diamond of the Air and will of the minstrels broadcast and covers a wavelength of 200 to 550 meters. improve any good circuit. All bolts and screws ening to some completely assembled f17Á0 furnished from here and there and from time to UNITUNE Model CF $3.00 of Consists of 2C unit with one fixed RF coupler and time, you will probably accuse us special three winding coil, with fixed primary and BRACKETS-Well made of die-cast aluminum. making such a state- tickler, for use in capacity feedback regenerative Substantial supports. being goofy after 419.00 Simplify wiring. Used is circuits. Price ment. Be that as it may, WGBS UNITUNE Model TIC wfgt! in the DIAMOND OF AIR and the releasing every other Sunday a line of This model is similar to Model RF except that the THE right hand condenser holds a standard BRUNO BERNARD. "nigger talk" that is about as funny as THREE -CIRCUIT TUNER. It is adaptable to a Adjustable Brackets, pair $1.25 completely asses anything that we have ever heard broad- variety of circuits. Price. .Cr night Brackets, pair ...... 1.00 cast -with the possible exception of UNITUNE Model BD Consists of two condensers and two specially wound Mr. MacNamee's rollicking reflections coils designed for use only in the BROW SING- on the Dempsey -Tunney fight. DRAKE circuit. Price SEND IN FOR BOOKLET BUT how do the scientists hope to conquer static when after all these years B. C. L. RADIO SERVICE CO., Inc. they can't make a fussy steam radiator Dept. P :: 221 Fulton Street :: New York City shut up? -Macon Telegraph

www.americanradiohistory.com Page 862 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY

BROADCASTS * of the leading CONDUCTED BY CHARLES L. REESE, "B" Eliminator JR. Will Radio Compete broadcasting 59 manufacturers with the in this country has been (RAYTHEON, Newspapers? largely due to the absence of tax re- of course, included) strictions WHETHER the citizen of the future of this kind upon either trans- *and the roll is growing! mitting or receiving is to have his news served to him via sets; and although it is too radio or must seek it out in the papers much to hope that other state USE OR RECOMMEND and city governments is one of the problems that is beginning will entirely ignore the greatest variable resistor! to loom as broadcasting threatens this golden opportunity for taxation in to an entirely become a serious rival of the daily press. new field they should be made Even now almost all important sporting to realize the hampering influence CLAROSTAT of events are reported for radio such restrictions. the audi- * * ence. The solution will probably be a compromise, in which radio will handle New Laws to Restrict Radio eLAROSTAT covers the "spot" news, the reports of sport Advertising every resistor need. events and all news in which speed of WHEN the radio communication bills that Congress is is an essential, leaving expected to act upon this It is designed for the to the fall eventually papers the more detailed and become law it is almost precision leisurely report certain that control of of events and editorial they will contain two provisions that comment. have been fairly well modulation, regener- * agreed upon; that ation, oscillation, grid all advertising matter that is paid for Radio Beacons for Airplanes directly or indirectly, must be an- action, plate voltage nounced THE first radio beacon of the new frankly as furnished by these type advertisers; and general laboratory which will guide commercial airplanes and that there shall be no dis- crimination in their cross-country flights has just as to charges, terms or serv- practice. ice to advertisers. been completed at College Park, Md. i "THE GATEWAY A tower, seventy feet high, rises from a frame building in which is housed the The First Golf Championship TO BETTER RADIO " radio apparatus; this tower supports a to be Broadcast triangular loop antenna which will emit WHAT is said to be the first a 32 -page book which double-beam broadcast waves. Plans call for a "side- line" report of golf championship chain of these beacon gives accurate instruc- stations, across play was the transmission of matches the continent, spaced 200 miles apart. tions in this year's national amateur golf for the use of * * CLAROSTAT in every championship at Baltrusol by WOR. To Protect Airplane Ten miles of telephone wire formed a conceivable type of cir- Passengers by Radio network over the entire course so that the announcer was able to broadcast cuit is now available. PASSENGERS on French commercial each play as it was made by plugging in It covers all the popular planes will be given all the protection at points along the fairway. that radio types of receivers, B affords. According to a * * recent decree of the French Govern- A Portable eliminators and power ment, every commercial Receiver as an plane that car- Ear- Trumpet amplifiers. May we ries ten passengers and that makes non- stop flights of more than 160 kilometers A RADIO receiver is a useful accessory send you a copy? Price must carry radio equipment and a at a heavyweight championship fight, 25c. skilled operator. according to Jack Poppele, a radio en- * * gineer, who arrived at the Sesquicenten- nial stadium AMERICAN MECHANICAL Local Taxes on Radio Sets for the Dempsey -Tunney fight to find, like many others, that his LABORATORIES, BROADCASTERS may soon be in INC. for a seat was nearly three- quarters of a mile Dept. P.R. shearing if politicians through the coun- one from the ring. Poppele, however, was 285 -287 North 6th St. hole try follow the example set by a Brooklyn, N. little foresighted enough to bring a portable Y. mount town in Kentucky, which has recently radio with him, so, with a wire over his passed an ordinance whereby any CLARO5TAT com- shoulder for an antenna, he listened to mercial or amateur broadcaster residing the ringside broadcasting there must pay of the fight an annual license fee of while he tried to see what $100. The tremendous he could development of in the ring with a pair of binoculars.

www.americanradiohistory.com P.::...... :111All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Pagr YOUR The Abox Filter INDIVIDUAL Real "A" elimir-ation at last. Filters current direct from charger to set- employs an entirely new type condenser. RADIO The first device of its kind ever offered to the public. PROBLEMS SOLVED Contains POPULAR RADIO maintains for the benefit of its readers a Technical Service Bureau and No Laboratory. under the personal supervision of Laurence M. ('ockaday which will, without charge, answer by personal letter any question. or request for information submitted Batteries ybproblem a subscrbb'r. This service is. however, also available to readers, other than subscribers. at the very nominal rate of $1.00 the Inquiry. Cannot run down In writing please confine your questions to one general subject, writing on one tide of the zurear out paper only, and enclose a ,elf -addressed and or stamped envelope. It is possible that your individual problem has been covered in an issue of POPULAR RADIO, and so as an aid to you we endeavor Price to keep a supply of back numbers in stock. The condensed Index below gives a few of the subjects that have appeared recently, look you want $1950 1 this list over and if the information Is covered, we will be pleased to supply back numbers at 36e. a copy. East of Rockies January. 1926 ;. -How to Get the Meet Out of Your LC -26 .. Receiver. -Rome New and Useful Facts About Coils. s -When Your Set Won't Work. Straight -Line- Frequency Condensers. of the tubes. Apparatus. THE Abox Filter is in no sense a for proper operation -What's New In Radio use, 1926 Battery. It is a filter circuit con- It is always ready for immediate eFebruary.-How to Reduce Distortion In Amplification. : -Some Stunt Sets. of a choke coil and two of the even after long idleness. -Important Kinks In Wiring. sisting i -How to Cut Down Your "B" Battery Rill. new Andrews electrolytic condensers There is nothing to wear out. 2 -Hints for Amateurs. 2: March. 1926 which operate on a new principle and It does not deteriorate either in -Why and How the Mllliammeter Increases the Erticlency of Your Set. permit enormous capacity with small use or disuse, and will last for many -What "Inductance" Really le. -uet of Broadcast Stations In the U. S. space, cost and weight. years. f -How to Build the S-C Receiver for Short t. and Long Waves. The Abox Filter handles as much For an explanation of this remark- = April. 1926 development write fordescription S-How to Get an Operator's "Ticket." as five amperes and renders the cur- able -What a Straight -line Frequency Condenser use. Really Is rent absolutely smooth and suitable of its construction and V. -How to Build a Power -pack Amplifier. re -The New "Crystal Pilot" -How to Build and Operate a Low -Power - Transmitter. THE ABOX COMPANY 215 N. Michigan Ave. CHICAGO -The Popular Radio Medal for Conspicuous f Service. Mel. 1926 f -How to Draw Up Your Own "Tuning Graphe." HOG 1 -How to Build the Improved Raytheon ycafi GROUND Power -park. 2 -How to Build an Antenna Mast for $15.00. DISTANCE : -Fifteen Ways to Reduce Static. 7,4. INCREASES D` -Do Your Coils Broadcast? June. 1926 -How to Build the New Home Receiver. -How to Put Up a Good Outdoor Antenna. on your RADIO -How to Get the Most Out of Your Ready - made Receiver. Marvelous newly invented ground gives 100% -Audio-frequency Amplification. How to Get improved reception. Increases power and dis- It Without Distortion. tance. users say. Thousands getting results -Four Aseem- Radio Engineer of Bur- Raytheon Power-peck. like D. 8. Friedman, bung the r lington. Iowa, who writes. "Am very much July. 1926 pleased with way your Ground Hog operates. % so in Summar . t -How to Get the tient Recent! to tune in any stations -The Beet Crystal Set for $13.00. Am now able good -How to Build the Newest Portable "Town with Gale troohle from static. Everyone and Country" Receiver. pleased and delighted. Users report. "Leaks -Four New Combinations of Unite for Aesem- stopped." "Static reduced." "end to Jangling cling the Raytheon Power -Pack. even in midsummer," "Results never dreamed -How to Get the Most Out of Your S-C Re- guaranteed or S celver. nf.' Absolute satisfaction money bock at once. August, 1926 -A New Method of Using Harmonics for De- The New 6 -Tube Always Insured termining Frequencies. Efficiency -Popular Radio Circuits. Only ground on market that has power to -How to Build the Improved Browning -Drake rlraw' and hold moisture thus assuring maxi- Receiver. efficiency at all times. Holds moisture 2 -How to Pick Out a Loudspeaker. mum 1 Out of Your "Town indefinitely. Highly sensitive to radio -How to Get the Moat ]E]L]KÇA\Y ctear,IpoTIrr S. and Country" Receiver. enew Proven vahmbee aid to -Three Vacuum Tubes in One. ful distance rePi ptnm. :1 September, 1926 -Foretelling Radio Reception from th path Donle Truphonic SEND NO MONEY 5 Weather Map. Every radio owner needs a Yale (:round Hog. ee -How to Build an Impedance coupled Am- Audio who plifier. Amplification To introduce. we offer to those act at : -A Radiant Crystal Pilot. once. regular 115.00 size for only $2.00. Send -Popular Radio Circuits. which delivers pure tone in any name today and pay postman $2.00 plus 17e. -How to Simplify Your Set with Automatic volume over the entire tonal postage on delivery. nr send only $2.00 with 1 Filament Controls. postage. -Inside Information on New Radio Reeelverw scale, and the patented Elkay order and save -How to. Wire Your House for Radio. Synauto R. F., which smooths Highest Approval October, 1926 to Bold the New L(-27 Receiver out the tuning over the whole Tested and approved by -How Radio Laboratory -The Radio Road Hog dial from 200 to 580 meters . , . Popular : -Popular Radio Circula and other high scientific radio -Ses That Earn Incomes. is a receiver that will be mod- authorities. You can order -Inside Information on New Radio Receiver,. Fade. em for years to come. direct today with absolute -Why Signals confidence of value and satis- = November, 1926 Completely shielded. Neat. Uni- ._ -How to Build the LC-Senior Power-Pack. Control -the flexibility of 3 dials at faction. -Waves and Wavelengt hs. your finger tips. In brown antique, -Popular Radio Circuits. FREE -Complete description of Ground Parts. Pura- finished mahogany. $125. (Ex- and full details -How to Select Your Radio the Hog, proof of user satisfaction -How to Patent Your Radio Inventions. clusive franchise to Trade). of amazing special offer free on request -Send -How to Snider. The Langbein -Kaufman Radio Co. name today. RADIO Dept. P. POPULAR 62 Franklin Street Raw Haven. Cann. Yale Specialty Department 128 .1 Supply Co. 627 W. 43d St., New York 1. 131 W. RSV , Kansas City, Mo. s-

www.americanradiohistory.com Page 864 .111 apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Radio Saves $22,000 on Made THOUSANDS If the Lecturers' Salaries in the DO Set EDUCATIONAL lectures by radio are World's Builder apparently more attractive to the aver- WHY NOT YOU ? age man Largest Needs It than free lectures given in Radio school buildings and halls, according to PILOT statistics recently compiled in New Parts Plant Makes It York. The Board of Education there Variable condensers Millions of has announced that th e attendance at Fixed condensers Pilot parts free lectures has been reduced so much Midget condensers because Now in use of the information now avail- Rheostats In America able over the radio and other sources Potentiometers In Europe that the number of lectures for the corn- Universal sockets Even in ing year will be drastically curtailed and Vernier dials Far away Aus- the appropriation for the Board of Lec- One -piece dials tralia tures will be reduced from $38,000 to Filament $16,000. switches UI L D Under all kinds Binding posts WITH Of conditions Sub -panel In every type iiritain's Broadcast Empire brackets Of receiver. Two powerful Coil Mounting PILOT new broadcasting sta- Pilot assures brackets tions that are now planned for the two Set builders Snap terminals leading cities of India, Calcutta and and strips RADIO PARTS Products of Bombay, will help to make England's Perfect quality Pilot lights AND rapidly growing radio empire nearly as Adjustograsis That cost vast as her territorial possessions. Aus- Short wave SAVE Less because tralia and plug -in South Africa have for some coils Pilot time had stations Audio transformers MONEY that rivaled England's Radio transformers Makes and sells own in power and range and these two Small knobs More parts new broadcasters in India will complete Lug Jacks At dealers the chain. everywhere Than any other The original plans for the Plugs Manufacturer. stations were laid immediately after the PILOT successful use of broadcastng during ELECTRIC MFG. CO., 100 So. 3rd St., Brooklyn, N. Y. the BRITISH ISLES. general strike in England showed R. A. Rothermel, Ltd.. London AUSTRALIA and NEW ZEALAND United Distributors, Ltd., Sidney BRAZIL and ARGENTINE, Samuel the tremendous value of radio as a Rio Janeiro Meyer, and Buenos Aires means of retailing information to the s>--- s>s>s> sr `-- great mass of the people when all other means of communication fail. s Morison's Has All Parts! A Real Radio Eden THE radio paradise of the world, ac- LC cording to reports from abroad, is INTERMEDIATE Bude -in- Cornwall, a small town in western England where listeners -in are POWER PACK able to tune in American stations at 1 FILTREX A-C Transformer, Type almost any time and where Continental K 180 $5.25 1 Na -ald Socket, Type 481 X .35 broadcasters are received even in the 2 FILTREX Choke Coils, Type K The hot summer $8.75 13.50 months with clear quality t, Eby Binding Poets .90 and loud volume. Visitors to the village I Acracon Condenser Block, 14 mfd 11.00 N 1 Acracon Filter Condenser, .1 mfd report that, for some unexplained 440 volta, D.0 1.00 E reason, signals 1 Hardwood Baseboard, walnut come in better there finish, 7! ¡r x 18" x i r .85 than in any place they have ever been, 1 Hardwick, Field & Leeb Resistance Unit, Type 200 5.25 although in Bodmin, only a few miles 1 Centralab High -current variable away, there resistance. 2,000 ohms total 2.00 is an absolute dead spot, I Bakelite Binding Poet Panel, 3y4 and the nearest broadcaster can z 4,4- z ti,' drilled .50 hardly I Set "Popular Radio" blueprints, and WESTERLAND be heard even on a five -tube set. construction booklet 1.00 SUPER a a Celatsite Connecting wire, screws, -VERNIER etc 50 1 8 ft. twisted silk lamp cord with Sixty-five New Broadcasters attached TUNING Plug 40 DIAL by January $42.50 Gets More Out of Your Set AMERICAN fans will have sixty-five Yazley Automatic Relay Switch, No. 444, BECAUSE: $5.00 extra new stations to listen to before the I. Sharper Tuning (150 -tn-I gear ratio) 2. Quicker Tuning (Instant Jump year is up as a result Morison's Gives You SERVICE! to station) from station of the ruling of 3. Easier WHOLESALE Tuning (stations logged on face of dial the Department of Justice that makes :: RETAIL -no charts or log -books needed) 4. Simple operation (one -knob control) it nearly impossible for Secretary 5. Absolute elimination of backlash movement (worm -gear Hoover to refuse to grant 6. a license to Easy to attach (no holees. toldrill In panel) With any and all applicants. At the Westerland Super-Vernier De. least that can hit the peak of the wave every nmfr dosThis is means better nce the estimate of the Department of ORISO from _Inn, longer freedom Interference-In short, maximum E/f'cJrica/ Supply Co Inc. from your xet. reenita Commerce which still has 650 applica- Ask your tions on its files. The deluge 15EAST40T-' STREET - dealer or order direct of new stations will not be heavier because few NE i-V YORK WESTERLAND CITY CORP. Price of the applicants will be able to get their Dobbs Ferry, N. Y. $2.50 apparatus ready to go on the air Le:ore that time.

www.americanradiohistory.com Page 865 Ill apparatus advertised in this magazine has been tested and approved by POPI'LAR RADIO LABORATORY

fiff/ 1/1113 C:AYAC:11 C./KS -AIIMMIP "UNIVERSAL" FILTER CAPACITOR BLOCK

This new FARADON " Universal" Filter Capaci- tor Block, of 14.2 Mfds. in one container, is for oper- ation in connection with the most generally used Battery Eliminator circuits. It contains important features not heretofore found in grouped filter con- densers. The total capacitance is connected to fixed termi- nals in convenient units, permitting ready wiring as desired. Units to be connected in the circuit where Model WS3750 possible high potential surges may occur are con- structed to withstand a higher voltage than is usually required. Convenience, safety and continued satis- x Z a factory operation are combined in the FARADON Q 4 Filter Block. b 3 3 a (ARC, TY (1.fiil BY-PASS CAPACITORS

Models Capacity Operating Flash Model MFD DC Teat DC No. M 150 500 WS3713 1 150 500 WS3714 2 150 500 WS3715 RELIABILITY Is essential to Satisfaction in By -Pass and Filter Capacitors. Not until a product has successfully passed exacting final electrical and mechan- ical tests is it considered worthy of the "FARADON" trade mark and ready for commercial use. Dependablé, efficient products are the result. U. S. Army, U. S. Navy, Bureau of Standards, General Electric Co., Radio Corp. of America, Tropical Radio Telegraph Co., Westinghouse Electric & Mfg. Co., and Western Electric Co., are some of the large Faradon users. Secure the reliable Faradon Capacitors at your Dealer's. WIRELESS SPECIALTY APPARATUS COMPANY Jamaica Plain Est. 1907 Boston, Mass., U. S. A.

www.americanradiohistory.com Page e 80 .Ill apparatus advertised in this magazine has been tested and approved by POPILAR RADIO LABORATORY Outstanding Program Build A Giant Features of the Month Build Your Own FOOT NOVEMBER 20th to DECEMBER 15th Unit developed and the coming month, November 20th to speaker designed 3 CONE DURINGDecember 15th, the following regular and special by program features are scheduled. This list, which Clyde J. Fitch, noted Big SPEAKER will be augmented monthly as advance information is received, will be published in each issue of this radio engineer. Re- magazine; all broadcast stations are invited to re- sults guaranteed Save port coming program features of outstanding in- 3 Foot terest or importance. Reports should reach the equal to the finest Four -fifths Editor of POPULAR RADIO on or before the 23rd of the month preceding. factory -built speaker of Retail Cost; NOVEMBER or your money back Cone (Eastern Standard Time) if you wish it. Eas- Equals Finest 20; Walter Damroeh, WEAF, 9:15 P.M. Piano Lectures and New York Philharmonie Orchestra. ily assembled; oper- Speaker Made (Also broadcast from WEE! WGR, WFI, ates from any re- Speaker WCAE, WWJ, WSAI, WTAM, WON, KSD, You can build this SENSATION of WCCO and WDAF). ceiver that will work the Radio Shows in one evening at 22; .4 sé P Gypsies, WEAF, 9:00. (Also home yourself, make It equal to a fac- broadcast a speaker; wonderful tory -built speaker: and skeet from WEEI, WJAR WDAF, WRC, WCSH, Radio Show Only with a 3 R. speaker can you get WCAE, WTAM WLITand WWJ). tone quality at any real tone qu ery note of the 23; Auction Bridge instruction, WEAF, 10:00- brew horns In an orchestra, the beata of the bass 10:30 P.M. (Also broadcast from WEEI, volume even with Sensation drum, the low notes of a organ and ALL the In- WCSH, WTAG, WJAR, WCAE, between tones to the highest note of the violin and WGR, power tubes. tae shrill treble of the piccolo. WTAM, WFI, WWJ, WSAI, WON, WOC, But you must choose your unit with care. It IS WCCO and KSD). most important. Insist on it 28; Happiness Boys, WEAF; Si:0 P.M. 27; Walter Damroeh, WEAF; 9:15 P.M. Piano FREE Blue Print Lectures and New York Philharmonic Orchestra. (Also broadcast from WEEI, WGR, WFI, Famous Tun -Bar Unit WCAE, WWJ, WSAI, WTAM, WGN, KSD, sent prepaid on receipt of PPI1I1 Spaker Unit WCCO and WDAF). S7 50, or C. O. D. charges '28; Atwater Kent Hour, WEAF, 9:15 P.M. (Also collect, if you prefer. Free Designed especially to operate a 3 ft cane and to blue print with each work perfectly even with power tithe. Ari/u table to broadcast from WJAR, WEEI, WFI, WCCO, order the audio output of any set. Recommended by lead- WTAM, WON, WCAE, WGR, WOC, for unit; blue print alone, S1. ing radio engineers. Finest seawnuvl steel magnet: WTAG, WWJ and KSD). double pole vibrator: shortest, moo substantial driv- 29; Rolfe 's Patois D'Or Orchestra, WEAF, 11:00 ing rod on any cone speaker unit. A marvel of design and construction. P.M. Your dealer has or can get the PENN Itnit for you. 29; A ct P Gypsies, WEAF, 9:00 (Also broadcast Insist on examining It before you accept any other. from WEEI, WJAR, WDAF, WRC, WCSH, Price. $9.50. If he hasn't the PENN or will not get WCAE, WTAJI, WLITand WWJ). It for Ynu, we will ship you direct. prepaid. on receipt 30; Auction Bridge Instruction, WEAF, 10:00-10:30 of price. Parts complete-- inelnrling 2 sheets of Al- M. (Also hambra F'ONOTEX. PENN Back Rings, Unit P. broadcast from WEEI, WCSH, Mountings, Special Ambrold Cement and PENN WTAG, WJAR, WGR, WCAE, WTAM, Cone Speaker Cone Speaker Unit, only $14.15. WFI, WWJ, WSAI, WGN, WOC, WCCO Construction article, "How to Build a 3 Fr. ('one and KSD). UNIT Speaker for only $14.15" sent for 10e. coin or stamps. 30; Keystones, WJZ, 9:00 P.M. (Also broadcast from WRC and WGY). PENN RADIO 30; Eseready Hour, WEAF, 9:00 P.M. (Also $7.50 SALES CO. broadcast from WEEI WFI WCAE WGN, Direct from maker 104 Fifth Ave. Suite 2077 New York City WWJ, Woe KSD, WJAR, WCCO, WTAM, hi.r f. WGN, WSAI and WTAG). G. lt. l't:NN ,."1 3: t'n. 30; George Olsen's Orchestra, WJZ, 10:45 P.M. TUNBAR RADIO CO. York t'llc Nlw DECEMBER 26 Cortland! St. Desk "R" New York City 1; Eastman Theatre Orchestra, WHAM, 8:30 P.M. (Also from WGY). Q 1; Radio Nature League, WBZ; 8:30 P.M. 2; EskimosEskimos, WEAF; 9:00 P.M. (Also broadcast liv)i asls from WJAR WTAG, WFI, WCAE, WBAI, WTAMW WGR, WWJ, W()C, WCCO, The House KSD and WG1.I). of 30 2; The Zippers, WEAF; 10:00 P.M. (Also broad- cast from WFI, WCAE, WWJ, WGR, WOC, Years' Reputation WCCO, WTAG, KSD, WSAI, WJAR, WGN, Where there is only one quality--the WDAF and WCSH). best -where prompt attention, te- Choose Your Cone 2; Royal Typetoriter flour, WJZ; 9:30 P.M. (Alan as service and practical knowledge broadcast from WGY, WRC and WCAD). hold old customers and make new ones. 3; Happiness Boys, WEAF; 8:00 P.M. Materials 4; Wader Damroeh, WEAF; 9:15 P.M. Piano Carefully Lectures and New York Philharmonic Orchestra. Complete Parts (Also broadcast from WEEI, WGR, WFI, In Building Your Own WCAE, WWJ, WSAI, WTAM, WGN, KSD, COCKADAY'S WCCO and WDAF). 5; Atwater Kent Hour, WEAF; 9:15 P. M. (.1150 NEW RECEIVER broadcast from WJAR, WEEI, WFI, WC'('t i, WTAM, WGN, WCAE, WGR, WOC, WTAG, WWJ and KSD). THE LC -27 3 Foot Cone 8; A & I' Gypsies, WEAF; 9:00. (Also broadcast Parts exactly as used by the au- from WEE!. WJAR, WDAF, WRC, WCSH, WCAE, WTAM, WLIT and WWJ), thor and as de- 6; Rolfe's scribed in October WCADE especially for cone type sprak- Patois D'Or Orchestra, WEAF; 11:00 5.20 ers. ALHAMRRA P.M. Popular Radio, (;J, FON -O -TEX is 7; Keystone's, used by practically all leading cone type WJZ; 9:00 P.M. (Also broadcast speakers manufacturers. This remarkable from WRC and WGY). All Chargea Fully Prepaid 7; Eeeready Hour, WEAF; 9:00 P.M. material has no grain, hence no resonance (Also CORBETT CABINET $18.00 EXTRA point of its own; but resonates uniformly broadcast from WEEI, WFI, WCAE, W(;I1, at all frequencies. WWJ, WOC, KSD, WJAR, WCCO, WTAM, WON, WSAI and WTAG). Price 73c for a Complete Parts sheet 18 a 38 inches. 7: Auction Bridge Destruction, WEAF; 10:00 -10:30 large enough for a 3 foot cone. Ask your P.M. (Also broadcast from WEEI, WCSH, dealer. If he hasn't Alhambra EON -O- WTAG, WJAR, WGR, WCAE, WTAM, THE TEX we will supply you. To the coe of WFI, WWJ, LC -27 WSAI, WGN, WOC, WC('O the number of sheets you need, add $1 for and KSD). Intermediate packing and delivery charges. 7; George Olsen's Orchestra, WJZ; 10:45 P.M. $47aso The SEYMOUR Co.. Desk 101 8; Eastman Theatre Orchestra, WHAM; 8:30 P.M. Power (Also broadcast Pack 325 West 16th Sr. New York City from WGY). 8; Radio Nature League, WBZ; 8 :30 P.M. ALHAMBRA 9; Eskimos, WEAF; 9:00 P.M. (Also broadcast WRITE US for the BEST from WEEI, WJAR, WTAG, WFI, WCAE, WSAI, WTAM, WGR, WWJ, WOC, WCCO, Proposition on These KSD and WGN). 9: The Zippers, WEAF; 10:00 P.M. (Also broad- Popular Kits: cast from WEEI, WFI, WCAE, WWJ, WGR, Woe, WCCO, WTAG, KSD, WBAI, WJAR, Sargent's lnfradyne,Victoreen Super- rON011i. WON, WCAE and WCBH). Het, Improved Browning - Drake, FOR CONE TYPE"LOUD SPEAKERS 9; Royal Typewriter flour, WJZ' 9:30 P.M. (Also broadcast from WGY, WRC and WCAD). Hammarlund- Roberts Hi -Q, Power 10; Happiness Boys, WEAF; 8:00 P.M. 11; Walter Damroeh, WEAF; 9:15 P.M. Piano Pack Amplifier Lectures and Neto York Philharmonic Orchestra. and other standard kits (Also broadcast from WEEI, WGR, WFI, WCAE, WWJ, WSAI, WTAM, WGN, KSD, M. &H.SPORTING WCCO and WDAF). GOODS CO. 12; Atwater Kent Hour, WEAF; 9:15 P.M. (Also 512 Market St., Phila. broadcast from WSAI, WEEI, WFI, WCCO,

www.americanradiohistory.com AU apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 867

You may have wondered why a Radio Set using lupi!Iq;;!úu!IIiJUüppqü!!IÜg4ijglpl''. the NATIONAL BROW N ING -DRAKE TRANSFORMERS perform so G exceptionally well

There are 2 reasons for this

1. SLOT - wound Primary 2. SPACE 'wound Secondary These are the 2 reasons why the NATIONAL BROWNING 'DRAKE TRANSFORMERS are so sensitive and selective. They were developed mathematically by Glenn H. Browning and F. H. Drake after a year of research at Harvard University and are made under Glenn H. Browning s supervision. The NATIONAL TUNING -UNITS comprise these fine coils and the NATIONAL "Equicycle" con, densers (plates developed by Prof. R. F. Field of Harvard University, and Carl A. Hellman of Washington, D.C.) -and the unexcelled NATIONAL VELVET VERNIER DIALS, Type A, Type B, or Type C, the ILLUMINATED DIAL. Price BD- IB,$fo.25 BD- 2B,$14.75 Inductance Coil and Transformer -Separate $8.50 NATIONAL Radio set essentials may be easily assembled into a modem re- BD- ceiving set -sensitive, selective, easy to operate and easy to listen to. la - Send for Bulletin 116 P.R. B D 2 B B E SURE YOU GET T H E GENUINE N RADIO PRODUCTS READY, Pres., Ito Brookline Street, Cambridge, Mass. . NATIONAL CO., INC., Engineers & Manufacturers: W. A. other Radio Products Makers of BroumingDralle Coils and Transformers, Equicycle and Equimeter Condensers, Impedaformers and

www.americanradiohistory.com Page 868 All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY WTAM, WGN, WFI, WCAE, WGR, WOC, WTAG, WWJ and KSD). 12; Rdle's Palais D'Or Orchestra, WEAF; P.M. 11:00 13; A & P Gypsies, WEAF; 9:00. (Also broadcast from WEEI, WJAR, WDAF, WRC, WCSH, 14; Keystonerw WJZ; 9:00 P.M. (Also broadcast from WRC and WGY). 14; Ererrody Hour, WEAF; 9:00 P.M. (Also broadcast from WEEI, WFI, WCAE, WGR, WWJ, WOC K8D, WJAR, WCCO, WTAM, WGN, WSA1 and WTAG). 14; George Olsen's °reheatr°, WJZ; 10:45 P.M. 14; Auction Bridge Instruction, WEAF; 10:00 -10:30 P.M. (Also broadcast from WEEI, WCSH, WTAG, WEAR, WGR, WCAE, WTAM, WFI, WWJ, WSAI, WON, WOC, WCCO and KSD). 15; Eastman Theatre Orchestra WHAM; 6:30 P.M. (Also broadcast from WG'Y). 15; Radio Nature League, WBZ; 8:30 P.M. 15; A R P Gypsies, WEAF; 9:00. (Also broadcast from WEEI, WJAR WDAF, WRC, WCSH, Shining Eyes- WCAE, WTAM, WLITand WWJ). Happy Hearts - Trans -Oceanic Calls Heard POPULAR RADIO has now completed ar- A Resonant Xmas With rangements for forwarding to transmitting amateurs in England, France, Germany, Austria, Ireland and Italy all calls heard The New (QSL) cards that may be addressed to them ../ MU-RAD by American amateurs care of this mag- SIPER - SIX - RECEIVER azine. These cards will be delivered through local agents in those countries, who have or ONE DIAL When the gifts are untied, the can- can obtain knowledge of the present address dles extinguished and the kiddies of the foreign amateurs. Plans have also CONTROL gather 'round at the close of a happy been completed by this magazine for forward- Christmas Day, the soft sweet tones ing to transmitting amateurs in this country of MU -RAD will waft their way in turn all QSL cards that may be addressed into your heart. Faithful reproduc- to them by amateurs from those countries. tion, exquisite tonal qualities, sim- American amateurs are invited to send their plicity of operation -all this is cards to foreign amateurs through this office, yours with the new MU -RAD re- which will not only assure safe delivery MU-RAD ceiver. Ask your nearest dealer for through the special agencies which are thus a demonstration. You may provided, but which will publish a RADIO CORPORATION ex- monthly change your old MU-RAD set for list in a "Trans- oceanic Calls Heard" de- Asbury Park, N. J. new yearly models. partment, Address your cards to the foreign amateurs by call to- numbers and enclose them in envelopes The Calls f` Heard Editor, Battery Testing Simplified POPULAR RADIO 627 West 43d Street, New York and safeguard- i``i ed with com- THE following bination hy- stations were received - drometer and and logged at the amateur station water gauge. of / Know when to Horace L. Pither, 133 Melfort Road, charge when Thornton to add- .water Heath, Surrey, England, on one squeeze of an 0-v -1 receiver using no ground with a bulb does both. single -wire antenna fifty feet long with This is an exclusive IN -A-CAP feature. It extends about 3' above battery, is a twenty-five foot feeder. properly vented so battery can be used U -2CV- September and charged with hydrometer in place. 4, 1926; signal It is not necessary to handle the instru- strength, R6; steady AC note. ment therefore it cannot drip, be mis- placed or broken. Don't ruin your bat- U- 1BIT- September 4, 1926; signal tery when it is so simple to care for. It strength, R5; using AC. insures longer battery life, protects rugs, floors, clothes, and makes certain good U -1AXA- September 4, 1926; signal reception at all times. Tested and ap- proved by leading radio publications. strength, R6-7; good steady DC note, e tion Sold on money back guarantee. 75e calling BZ -1BI. each. Set of three $2.00. Where spare is limited we recommend our special U- 1CKP-September 5, 1926; signal In -A -Cap with patented balls instead of float. 2% above battery. Also strength, R8; good note, very loud; Not where volt meter is Deeetlon used our In -A -Cap calling B-08. Water Gauge set of 3 for 91.00 no float or,balls included. U -1BJK- September 5, 1926; Volume, not noise. signal Tone, not blare. The latest convenience on the market strength, R6; steady note, slight inter- Clear, mellow, perfect reception of every sound our Curved Battery Filler. Replenish from a whisper to a full orchestra. your A Battery, B Battery, Trickle ference. That's what radio enthusiasts everywhere areen- Chargers, Power Unita )oiing with new and Elimina- U -1DI- September 6, 1926; signal the Dulce-Tone, the perfected radio - tors without moving them ,from the talking- machine-speaker. cabinet, the curve strength, R7-8; note steady, very loud. Dulce -Tone, for $10, and your phonograph make does the the finest loud speaker mood can buy. Try It and trick, fits i_ ex.=- A see. Your money back If you re not completely satis- into the tightest fied. At your dealers, or send the coupon. places, also good for f }iiit your automobiles. No ' - -- The following station was received THE GENERAL INDUSTRIES CO. radio should be with- and logged at out one. 0 . the amateur station Fomerty$namedlThe General Phonograph Mfg. Co. os. bulb of 75c. 4 oz. bulb, 65c. A. Jamison, 60 261 Taylor St., Elyria, Ohio 100 amp. hard rub- Clifton Road, Bangor, ber case battery with County Down, Ulster, Ireland, carrying handle, on a Enclosed Is Sl0 for my Dulce -Tone. If I'm not $12.00; one In -A -Cap modified Hartley 0-v-2 receiver. A satisfied after 10 days trial, I'll return It and get my money back. hydrometer and one fifty eight -foot horizontal curved battery filler, Hertz antenna Name free. was used with twenty two-foot leads Street IN -A -CAP HYDROMETER CO. spaced three inches. City State.... 1347 W. 14th Pl., Chicago U- 1AW-August 22, 1926; signal J strength R7; on 30 meters; no fading.

www.americanradiohistory.com All apparatus advertised in this magazine has been tested and approved by POPULAR RADIO LABORATORY Page 869 `fHeavy-Duty RADIOHM

coa Kit Panels With Gold Decoration Simple Control FORMICA is this year providing amateurs through the leading jobbers and dealers with handsomely decorated gloss black of B- Battery panels with gold decoration for the leading kits; Infradyne, Aero- dyne, Bremer Tully Counterphase and Power Six; Browning Drake Eliminator National; General Radio Universal; Victoreen Superheterodyne; Madison Moore Superheterodyne; Camfield Duoformer; St. James GET full efficiency from 8 tube; Karas Equamatic front and sub panels; and H. F. L. your "B" Battery Superheterodyne. Eliminator by installing a Manufacturers are using handsomely decorated Formica panels in dull finish some of them in two colors. Centralab Heavy - Duty Radiohm. Full resistance The FORMICA INSULATION COMPANY variation with a single 4641 SPRING GROVE AVENUE CINCINNATI, OHIO turn of knob, allowing Hear the FORMICA Formica has a Orchestra Tuesday Complete Service on panel marking for proper 9 to 10 Insulating Material over WLW for Radio Manu- setting to provide various facturers voltages. Tested and ap- proved by the Raytheon Laboratories. HAND BOOK Resistance remains per- FREE WITH manent as adjusted (no carbon particles or discs), Popular Radio and remains same for any Kendall Banning. Editor, and Laurence M. cockaday, Technical Editor of POPULAR RADIO. have compiled a book that will prove to knob setting regardless of anyone that he can build a set which will give distance. aelectivity and tone volume. and at the same time a very definite basic knowledge how often adjusted. Bush- of radio. shaft insulated to BUILD YOUR OWN SET ing and AND SAVE MONEY In 'Iiow to Build Your Radio Receiver," withstand 1500 volts. Its you will nod complete speclncatlons, construc- tional diagrams. photographs and Inatructlons smooth and noiseless oper- for building all of the following sets: A $5 Crystal Set will greatly improve The Haynes Single -Tube Receiver ation A Two -Stage Audio -frequency Amplifier The Cockady 4- Circuit Tuner your set. A 5 -Tube Tuned Radio- frequency Receiver The "Improved" Coc kaday 4- Circuit Tuner mailed direct on The Regenerative Super- Heterodyne $2 at your dealer's or Receiver receipt of pace. ADVISORY SERVICE ALSO FREE POPULAR RADIO maintains a big modern lab- oratory with a trained staff of Investigators CENTRAL RADIO under the personal supervidon of Mr. C'ocka- day. Thin Laboratory is always available FREE through our Technical Service Bureau to LABORATOR I ES answer. free to subscribers, by personal letter any problems you encounter which are not answered ID either the "Handbook" or the r::; Radio Catalog 17 Keefe Ave., Milwaukee, Wis. magazine. BEFORE you build or buy a radio be sure to consult ou new 100 Makers of a full line of variable resis- SPECIAL BOOK OFFER You can secure a copy of "blow to Build page catalog -sent to r you free. tances for 69 manufacturers of leading Your Radio Receiver" FREE. and have all the All the latest kits, accessories, and standard sets. privilege@ of the Technical Service Bureau parts -a million dollar radio stock to without additional expense. if you will send a choose from. remittance of 83.00 in full payment of 12 months' eubecrlptlon for POPULAR RADIO. (Or as an alternative, you may have the book and We Save You Money privileges of the Technical Service Bureau with POPULAR RADIO for 7 months only -for $2.00. We handle only brand new appara- A two dollar bill will do.) tus- standard makes that are fully Remember you take no chance-we will guaranteed. QUANTITY sale of refund your money in full if you are not more QUALITY parts explains our low than satisfied. prices. Compare with others and see why thousands of fans look to us as radio headquarters. Write for your POPULAR RADIO copy of this new catalog today. Department 125 Salvage Stock Store 627 West 43rd Street, New York Chicago t1Ó».. ..S: . }t Dept. PR, 509 S. State Street, Chicago, U. S. A.

www.americanradiohistory.com Page 870 All apparatus advertised in this magazineTabe has been tested and approved by POPULAR RADIO Bet LABORATORY Sin le Dial Radio

Retail Price

Wonderful offer direct from the $75 factory! Completely Assembled A perfect working, single dial control, 7 tube receiver. And just to prove ship it to your our claims, we will home for i. days' Imo Mal. Test it under all conditions. Test it for distance, ume and tonal quality vol- Big Discounts - and if you are not convinced that it is the best single dial set you ever heard, return it to to Agents and Dealers the factory. We don't want your money unless you are completely satisfied. 1 III1I 11111 11111 ;11111 11111 l'II '.Ig BIG PROFITS Metrodyne Super-Seven j TO AGENTS AND DEALERS Radio Our Agents and Dealers make big money 1 A single dial control, 7 tube, tuned Easiest set to operate. Only one small selling Metrodyne Sets. You can work all radio frequency set. Approved by knob tunes in all stations, The dial is electric- a or part time. Demonstrate the superiority America's leading radio engineers. Designed ally lighted so that you can log stations in the of Metrodynes right in your home. Metro- and built by radio experts. dark. The volume control regulates the recep- dyne Radios have no Only the highest competition. Lowest quality low loss parts are used. Magnificent, tion from a faint whisper to thunderous volume, wholesale prices. Demonstrating set on 30 1,000 to 3,000 miles on two -tone walnut cabinet. Artistically gilded loud speaker! The Met - days' free trial. Greatest money - making rodyne Super-Seven 1 genuine Bakelite panel, nickeled is a beautiful and efficient opportunity. Send coupon below -or a let- piano receiver, and we are so sure that you will be ter -for our agent's proposition. hinge and cover support. All exposed metal delighted with it, that )ve make this liberal parts are beautifully finished in 24 01,1111111111 11111 11111 11111 11111IIIII 11111 1111111111 11111 1111111111 11111 -k gold. 30 days' free trial offer. You to be the judge. Mail COUPON Below! Let us send you proof of Metrodyne quality F. L. Warnock, Greentown, Ind., writes: "I received the Met - rudyne in g,asi slap and am more tbau pleased with i6 Gut stations 2.000 miles away." o. J. Walker,Walker Mariposa. Calif., writes: "Received my Metro-o dyne Single Dial set O. R. I believe that these one-dial seta are going to be excellent sellers. I had no trouble in tuning in stations enough to satisfy anyone, so you will please send lee another set.' Roy Blooh, San Francisco, Calif., writes: "Very often we travel from New York to the Hawaiian Islands quickly from station to station -by means of the little tuning -knob which operates the electrically -lighted dial. The Metrodyne 30 Single Dial Set is mueh easier to operate than any radio set Days' FREE Trial I've ever seen." We will send you hundreds of similar letters from own- ers who acclaim the Metrodyne as the greatest radio set in the world. A postal. letter or the coupon brings Metrodyne Super -Sias gowl complete information, testimonials, wholesale prices, liberal 31 Another triumph in radio. Here's the new 1927 model Metro. RETAIL PRICE and our day.' free trial Offer. dyne 6 tube long distance tuned radio frequency receiving set. Ap- proved by leading radio engineers of America. Highest grade low loss parts, completely assembled in a beautiful walnut cabinet. METRO ELECTRIC COMPANY w. y 2161.71 N. California Easy to operate. Dials easily logged. Tune in your favorite station Ave., Dept. 139 instantly on same dial readings every time. No guessing. Chicago, Illinois Mr. Howard. of Chicago, said: "While Sve Chicago broadcasting stations Gentlemen: were on the air I tuned in seventeen out -of -town stations. including New NAIL THIS Send me full particulars York and San Francisco on my loud speaker horn, very loud and clear. as COUPON about Metrodyne 6 tube though they were all in Chicago." Mir and 7 tube sets or send a postal or Ietter.Get our and your Io days' Sr.s trial Offer proposition We are one of the pioneers of radio. The success of Metro - before buying a radio. Deal direct with manufacturer - Name dyne sets is due to our liberal 30 days' Irmo trial alter, Save Money. which gives you the opportunity of before buying. trying i Address METRO ELECTRIC COMPANY If sou are interested in AGENT'S prep -^ 2101 -71 N. California 139 place an Ave. Dept. Chicago, Illinois osition, "X" in the square slo I 1

www.americanradiohistory.com CROSLEY RADIO All prices sligbtb higher west of Rocky Mts.

nn -rur '9"0\moi 0 This little double circuit 1 -tube Bet has made long dia Lance records. ß LTTER'' COSTS LESS

4 tube.. Amazing efficiency, Cres- cendon equipped!

The 4 -29 in port able form.

Five tube.. tuned radio frequency. u`non Two cillating radioio frequency ampli- fication, Creacen- dont two stages audio frequency amplification. 5 -tube 538 I TIM MI with the

S tubes.l-dialcon- rol ar n poCrescendon CRES CENDON abwtytubeadapt- abdity. which builds great volume ss on distant stations 6 tubes. True-cas cade amplifica Lion; non -oscilla[ Ing and non -radi Sit down before any ordinary 5 -tube tuned radio frequency sting. set and turn the dials. Some stations will come in clear and loud. Others you will hear but faintly and the manner in which they slip away is exasperating. Then try a Crosley 5-38. From a far -away station come the faint strains of an almost forgotten melody. How n a mahogany it! You turn the Crescendon console. 6- tube keenly you want to hear 6 -60 receiver. suddenly Crosley Musicone and, with a rush of swelling tone, the music speaker, ample compartment for reaches a volume and clarity as though it were broadcast batteries. from a station but a few miles away! Such is the function of the Crescendon -an exclusive Crosley device -a feature of this 5-tube tuned radio frequency set, known as the Crosley 5 -38.

Double drum sta ion selector The Mu ono and In external appearance, too, the set will delight you. room for batteries is by and accessories. beauty of its two -tone mahogany cabinet enhanced art metal trimmings which harmonize in color and design. The dials are recessed behind windows and vernier -con- trolled condensers make tuning easy and accurate.

2-Inchslas.$12.60. radio sets, the famous 5-38 is available Super Musicone, Like all Crosley 14.76. Musicone of mass produc- Dehne,SZI 60.Aleo at extremely low cost -the result Crosley beautiful Muai radio values. console with room tion which has established the world's greatest For batteries and accessorise, as below. President THE CROSLEY RADIO CORPORATION, CINCINNATI -POWEL CROSLEY, Jr., For Catalog". U. S. Patent No. 1.113,149 or under patent Crowley manufactures radio receiving sets, which are licensed under Armstrong station write Dept. 16 applications of Radio Frequency Laboratories. Inc -, and other patent. issued and pending. Owning and operating WLW, first remote control super -power station in America. All prices without accessories.

"THE USE Croeley Features Ing volume. An exclu- furnishes .substantial THE OF POWER sive Crosier feature. frame for mounting SINGL -DIAL PHONED ACUMINATORS" adapt- ALL -METAL elements, produces ex- SELECTOR Power tube 63.00 "CRESCENDON" SHIELDED CHASSIS cellent alignment of Nothing in Crowley Acumina- bilityy marks the condensers shields the _ dio equale permit tun- Crosley 630 "I When, on or- ;orsing in loud and 676 "and "RFL' dinary re ios. units from each other. ove or the - QUALITY prevents Interetage, 'tea ence clear -weak sta- sets. This feature T t passed over typifies Croaky provi- AND BEAUTY straintocatch iprove. the stability of single dial tions \ the circuit. in- and entirely missed by lmon for best radio IN CABINETS astationmile of control. Crosleysingle creases selectivity and drum control enables ordinary single dial reception at moderate AND away. turn of the radios. In tuning high met. This feature is in Crescendon on Crowley This truly great radio eaves costa by stand- you to find the stations CONSOLES this of sought without log powered and local sta- keeping with all that radios instantly swell achievement, found in ardising phase tions they are not used. is most progressive. reception to room -fill- severe! Crueler sets, manufacture. book or "toning"

PIIF.SS OF WILLIAM GREEN. NEW YORK } www.americanradiohistory.com inside-law 1.11"- rj Christmas ka.dio Set HE egtupment is as important as the set. The distance reach of a P çJ`'e set depends a great deal on the tube in the detector socket. The over -all 6xtra !6Ytra! performance of a set depends very 1 much on the tubes in every socket. Gift Id-ezs The volume and tone quality you will get are dependent upon the tube in for Ik,adio fans the last audio stage. In every point, A -spare" Radiotron - genuine RCA Radiotron, of course -of the tubes are as important as the set. the type he uses. And everyone who realizes this in- sists on genuine RCA Radiotrons. A power Radiotron UX -112, UX -171 or UX -210 for bigger volume and finer tone. The research laboratories of RCA, General Electric and Westinghouse A special detector Radiotron UX -200 -A for storage battery have new developed Radiotrons to sets -for longer distance reach. accomplishment, year by year. And the manufacturing skill of these same Ask any dealer all about these Radiotrons-he'll tell you companies keeps RCA Radiotrons which to get. But be sure its a far in the lead to accurate making. genuine RCA Radiotron, if its to be worthy of gift giving.

Be sure, when you buy a radio Christmas RADIO CORPORATION set, that you are getting genuine RCA Radio - trons with it. You can tell by the RCA mark OF AMERICA inside the glass at the top. Or take out the New York Chicago tube, and look at its base. San Francisco PCA Rad iotron MADE BY THE MAKERS OF THE RADIOLA

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