SEPTEMBER, 1924 25 CENTS RAD (Keg. U. S. Put. Off.) www.americanradiohistory.com i RADIO TUBES GHAM AMPLIFIER 0299 TED Bring World Events to Far- Distant Vacation Lands D 4CK- COUNTRY isolation melts into world contact as you tune -in on music, D drama, and the final battles of the Presidential Campaign. CUNNINGHAM TUBE PRICES Make your camp, your cottage, your yacht the center of hospitality and enter- C- 301A-5 Volts 3 Ampere filament $4.00 tainment. C -299 -3 Volts .06 amp. Dry Battery Det. and Perfected Radio will Amp $4.00 do it, and Perfected Radio means the use of Cunningham C -300 -5 Volts Gas Con- Radio Tubes. The Cunningham dry battery detector and amplifier tube, tent Detector $4.00 C- I1 -1.1 Volts .25 amp. type C -299, makes it possible for you to treble your vacation pleasure by use Dry Battery Det. and of a portable receiving set. The special filament in this tube, using a current Amp. Special Base . $4.00 C- 12- Similar to C -I1 with so low that it may receive its supply from standard No. 6 standard dry batteries or even base $4.00 from ordinary flashlight batteries, makes possible this far -reaching application PATENT NOTICE of Radio. Cunningham tubes are covered by patents dated 2- 18-08, 2- 18-12, 12-30-13, The receiving set you now have can be readily adjusted to use this tube and 10- 23.17, 10- 23-17, and be a source of use others issued and pending. and pleasure on your vacation trip. Your dealer can give Licensed only for amateur, you useful suggestions for the purchase or construction of a highly efficient experimental and enter- tainment use in radio com- portable set. munication. Any other use will be an infringement. DATA BOOK Cunningham 40-page Data Book fully explaining care and operation of Radio Tubes now available by sending 10c in stamps to Branch Branch San Francisco office. CHICAGO 182 Second Street, San Francisco NEW YORK www.americanradiohistory.com Orl/tiLetilit Cotto Tone t Headset TOWER'S GIFT TO THE WORLD! Reproduction of All Radio in Cello -tones 40) For years Frank S. Tower played the cello, the richest -toned instrument in the world, giving concerts and recitals throughout Europe and America. With the soft, sweet "cello- tone" clearly in mind, he has successfully manufactured the TOWER'S scientific headset, which accurately reproduces all radio in the same liquid tones. TOWER'S scientific, lightest of all in weight, offers higher resistance, with elimination of distortion. Longer cord (full 5 ft.). Every set tested and approved by licensed radio oper- ators. Every set covered with our money - back guarantee. Order today by post card and we will ship immediately by Parcel Post C. O. D. Our $200,000.00 company stands squarely back of every headset. TIIETOWUZIMG. CO. 98 Dept. E Brookline Ave., Boston, Mass. VT.404'j` Mf4\i`; . , snrfC Tell them that you saw it in RADIO 1 www.americanradiohistory.com Forecast of Contributions RADIO for October Issue Established 1917 cv.9 Published Monthly by the Pacific Radio Publishing Co. G. M. Best will have two articles in addi- tion to his "Queries and Replies" which are ARTHUR H. HALLORAN, Editor universally recognized as containing reliable LAWRENCE MOTT, GERALD M. BEST H. W. DICKOW Associate Editor Technical Adviser Advertising Manager information. One article will deal with the construction of a two -stage choke coil amplifier Branch Offices: Correct Addresses: set costing less than $40.00 and giving distortion - New York City -r7 West 42nd St. Instructions for change of address should be less reception at Chicago -157 E. Ontario St. sent to the publisher two weeks before the high efficiency. The other will Boston -52 Irving Street. date Kansas they are to go into effect. Both old give the characteristics of audio -frequency City, Mo. -11o2 Republic Bldg. and new addresses must always be given. transformers at various frequencies. Rates: Advertising: Issued Monthly, 25c a copy. Subscription Advertising Forms Close on the First of the 6`N price $2.50 per year in the U. S., $3.00 per Month Preceding year elsewhere. Date of Issue. C. M. Jansky Jr. will continue his valuable Entered as second -class matter at the Post Office at San Francisco, Calif. series of articles on radio communication with Copyright 2924, by the Pacific Radio Publishing Co. some specific application of principles already developed. During the summer months, Prof. Address all communications to Jansky, as assistant consulting radio engineer for Pacific Radio Publishing the Signal Corps, has been devoting his time to Co. research work at Camp Alfred Vail, N. J. Pacific Building, San Francisco, California 6'4%3 VOLUME VI SEPTEMBER, 1924 NUMBER 9 1.41 Constructors of home -made sets will be inter- ested in O. B. Scott's details of the design and construction of the regenerative reflex, as well CONTENTS as in E. F. Kierman's directions for winding duo -spiderweb coils for use in the simplified RADIOTORIAL COMMENT 9 Reinartz circuit. THE BRASS POUNDERS OF NIPPON 10 By Volney G. Mathison Bernard Steinmetz explains' several methods RADIO- FREQUENCY WITH THE SINGLE -CIRCUIT for obtaining negative potentials for grids of REGENERATIVE RECEIVER 13 By E. E. Griffin vacuum tubes. THE VACUUM TUBE AS A DETECTOR 15 cap By C. M. Jansky, Jr. Jerome Snyder has a helpful article on the AN IMPROVED REINARTZ RECEIVER 17 theory and use of the hot wire ammeter. By Cessf ord Kerr cva IMPEDANCE VALUES OF AUDIO FREQUENCY TRANSFORMERS 19 The transmitting amateur will find some un- By Gerald M. Best usually good suggestions in several articles. F. Dawson Bliley A SINGLE CONTROL REGENERATIVE RECEIVER 20 tells how to get down to the By Paul Oard lower wavelengths now available for amateur A VARIABLE B BATTERY 21 use. L. W. Hatry discusses the design of the By David P. Gibbons reversed feed -back transmitter. M. Wolf de- RADIO CONSTRUCTION POINTERS 23 scribes a simple method for determining per- By Paul Oard centage modulation in radio telephone sets. PROPER CARE OF STORAGE A BATTERIES 24 F. Bowman passes on some good By H. A. Fischer stuff about a successful loose -coupled transmitting circuit. A HOME MADE SYNCHRONOUS RECTIFIER 25 By Geo. Becker, Jr. William Jackson describes an ideal chemical rectifier. A GOOD FILTER FOR THE AMATEUR TRANSMITTER 27 By C. W. Rados SECRETS ON SUCCESSFUL OPERATION OF TRANSMITTING Harry Diamond analyzes the nature of static TUBES 29 and its elimination. By Don C. Wallace ADJUSTING YOUR SUPER -HETERODYNE 30 By L. H. La Montagne Edward W. Smith presents a simple discussion THE SECOND HARMONIC SUPER -HETERODYNE 31 of the essentials of a good audio -transformer and By L. R. Felder circuit arrangement whereby the output can be IMPROVEMENTS IN THE 45,000 -CYCLE SUPER -HETERODYNE 33 improved in quality. THE GRID LEAK 34 cva By H. Bunch A TRANSMITTER THAT SOLVES THE LOCAL Q R M F. L. Ulrich has an interesting article on a PROBLEM 35 short wave DX receiver oscillating as low as By Franklyn S. Huddy 50 meters. DIGEST OF RECENT RADIO PATENTS 36 C4.9 QUERIES AND REPLIES ON C. W. PRACTICE 37 The fiction feature will be "A Royal Hiatus," By Gerald M. Best a story with a hundred chuckles. You will also WITH THE AMATEUR OPERATORS 40 get a good laugh out of "A Jazzed Up History FROM THE RADIO MANUFACTURERS 42 of Radio." 2 RADIO FOR SEPTEMBER, 1924 www.americanradiohistory.com THE «1\CHRO PnAS TRADE MARK BROADCAST Receiver that marks "It is only When the cold in season cornes that we know another long step forward the pine and cypress to be radio design and establishes a new set evergreens." -Confucius of standards in craftsmanship. In the coming cold season literature be not surpassed by thy Write for neigh bor -set the pace with your Grebe Synchrophase. A. H. GREBE & COMPANY, INC. Van Wyck Blvd., Richmond Hill, N.Y. Western Brunch: 451 East 3rd St., Los Angeles, Cal. Tell them that you saw it In RADIO www.americanradiohistory.com 11111111 I I I I I I I I =, I I I 1 11111 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 111 I I I I 1 11111 I I I I 1 L=' ` 1 =Ç= For Long Distance Rec,,...__.__=,_- ___.,_ .___-=,.. All Crosley Regenerative Receivers licensed under The Crosley Radio Armstrong U. S. Pat. 0/3.149 Corporation owns and operates Broadcasting Station W L W 111111IIIII111111 ¡¡ II IIIIIll1 1IIIIIIIIII1111 1 111111111 1111111111111 111111 1111111111111111111111111111111 IIIIIIIIIIII11I Better-Cost Less III IIIIIIII IIIIIIIIIII IIII III11111II UII IIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIUIIIIh,. Radio Products Tuned Radio Frequency Receivers Crosley A two -tube receiver Model VI with a reputation for Crosley Model X -J The famous Crosley long distance with pronounced clearness. It con- four -tube receiver sists of one stage of Crosley tuned radio frequency consisting of one stage of radio frequency ampli- amplification and a detector. This Crosley com- fication, detector and two stages of audio frequency bination multiplies the receiving range amplification. Probably the greatest single feature of the set of this receiver is its remarkable selectivity. It will tune through powerful local broadcasting stations Crosley Super This two -tube receiver and bring in distant stations VI is so coupled up as to clearly and with great combine volume.