Radio Digest (July 1924-Apr 1925)

30 RADIO DIGES T— Illustrated February 7 , 1925 Questions and Answers Hetduogen Filter Construction (10706) HES. Pittsburgh, Pa. I am building the hetduogen as described in Radio Digest Mr. Brush stated that ten different niters were constructed before the present one was adopted. I suppose it cost quite a lot of money and time to have perfected so wonderful a circuit. I do not wish to condemn the filter, but would it be possible to use three spider web coils wound on a 2-inch diameter core with 17 prongs? That is, one for the primary and two for the secondary with the special regeneration condenser mounted along side of the secondary? A. — We have your letter of January 8 containing suggestions for the changing of the filter in the hetduogen. If you have ever wound spider web coils you must realize that to put 350 turns on a spider •web form would require a spider web about 7 inches in diameter. Incidentally it would take more than 350 turns to get the same value of inductance on a spider web coil that one gets from winding 350 turns as wound in the filter shown. Of course the spider web could be kept of smaller diameter by using smaller wire, but the D. C. resistance would be so increased that any possible advantage gained from the low loss method of winding would be more than offset. We really feel that in this case a spider web filter is out of the question, but we feel that the honeycomb coils of 400 turns might be used one for the primary and two for the secondary. Multiphone enables five persons to listen with one set head phones. Price $3.50. Write Hinkle & O'Neil, 1314 Union Trust, Cincinnati, Ohio. PATENTS Write for my free Guide Books "How to Obtain a Patent" and "Invention and Industry" and "Record of Invention" blank before disclosing inventions. Send model or sketch of your invention for instructions. Promptness assured. No charge for above information. Clarence A. O'Brien, Registered Patent Lawyer, 2007 Security Bank Building, directly across street from Patent Office, Washington, D. C. Radio Dealers We can make immediate delivery on Federal 141 Style Receivers. CHURCHILL DRUG CO. Burlington, Iowa GO into the RADIO BUSINESS We specialize in Equipping New Dealers with entire stock — ADVICE FREE. Send for Our Radio CATALOG & BARGAIN LISTS Wholesale Only MANHATTAN RADIO CO. 112 Trinity Flace New Yorfc City Large Radio Wall Map r*^> T? r* The very latest up-to-date radio wall A IvHf EL maD 2S bv 34 inches. Shows call letters, locations, wave lengths, and kilocycles of all radio broadcasting stations, U. S., Canada, and .Mexico, relay divisions and radio districts. Also a scale for measuring distance. This wonderful map postage paid, ABSOLUTELY FREE. Merely send us a list of stores in your city which handle radio apparatus. Be sure and give the street address, and if you know the manager's name, give it also. DO IT TODAY before this offer is withdrawn. OZARKA INCORPORATED 808 Washington Blvd. Chicago Scientifically Designed New Karas Harmonik Audio Transformers. low ratio — 100% extra large coils circular shielded — -over size iron core. Karas Harmoniks were used by Mr. Brush to secure best results with his wonderful Hetduogen hook-up that so many radio fans are now enthusiastically building. Price $7.00 each KARAS ELECTRIC COMPANY 4042 North Rockwell St. Chicago, 111. Hetduogen (11317) CBW, Kansas City, Mo. In the December 27 issue the article on the hetduogen has started. If the succeeding articles necessary to build this are to extend over several issues at what cost may I obtain sufficient data to enable me to build at once. In your reply will you kindly advise me at once if the unusual amount of regeneration makes this set noisy. You know regeneration has been abandoned in a number of cases on account of noise. A. — We have your letter of the 26th relative to hetduogen receiver. It is not regeneration itself which makes a set noisy. Regeneration reduces the resistance of the tuning circuit and so increases the sensitivity of the set and the result is that the static over a very great range is brought in which increases the noise in the head phones The same result is to be noted when operating a superheterodyne. Adding Radio Frequency (11316) FHH, Brecky, Sask., Can. Some time ago I asked about adding Radio frequency to my receiving set. I might say that my receiving set is a Westinghouse Radiola IIIA. A. — The best answer we can give to your question is to write to Mr. S. W. Goulden of the Radio Corporation of America, 233 Broadway, New York city. He will be glad to advise you on any additions to be made to Radiola receiver. Write for Our Free Book on Patents — Munn & Co. 643 Woolworth Building, New York City; 518 Scientific American Bldg., Washington, D. C. ; 407 Tower Bldg., Chicago, 111.; 360 Hobart Bldg., San Francisco, Calif.; 215 Van Nuys Bldg., Los Angeles, Calif. 158 GENUINE Foreign Stamps. Mexico War Issues. Venezuela, Salvador and India Service. Guatemala, China, etc., only 5c. Finest approval sheets 50 to 60%. Agents Wanted. Big 72-p. Lists Free. We Buy Stamps. Established 20 years. Hussman Stamp Co., Dept. 153, St. Louis, Mo. Mailing Lists '•., Will help you increase sales V'j, Send for FREE catalog giving counts and prices od thousands of classmetf name q of your best prospective customers-National, State andLocal--Indlvlduals. Professions, Busin_es3_Concern3. ^ ing Stations Indexed with Call Letters, Location ^ Wave Lengths, Power. Handy DX map included E?i1%, RADIO CLOK SALES «^«A^#W^N 1IM-B Crtiieot National Bank Bids. M^sSs^ u.Ai«*,«ai«to c,o * mushy % BOOKLET 'On "Tube Control" tells how to bring in distant stations clear and loud. Just drop a post card to UNITY MFG. CO. 232 North Halsted Street CHICAGO, U. S. A. SOLVED! -The "B" Battery Problem Throw away your "B" Batteries and install a Kellogg Trans-B-former. It gives you "B" Battery current direct from your electric light socket at the trifling cost of onefifth of a cent per hour. Gives better reception — no interferences. Write for details. KELLOGG SWITCHBOARD & SUPPLY CO. Trans-B -Former 1066 W. Adams St., Chicago, HI. Limited Range (10688) EEE, Mead, Neb. I cannot reach high wave lengths with my three circuit regenerative receiver. My aerial is four wires each 22 feet long and 40 feet high. The trouble lies in the length of my aerial, because the same set on my former aerial reception was best on high wave lengths. I cannot change my aerial because of local interference and obstacles so it cannot be lengthened. Is there any way of equiping my set so high wave lengths may be reached? Which is the most simplest way? Also, I am using two metal pipes as masts for the aerial, must they be grounded? A. — The additional wires in your antenna system should be eliminated for they reduce the efficiency of the set. The overall length of antenna system is inclusive of lead-in and ground lead of the single wire. This should be properly insulated from its supports, which are not necessarily grounded. We are suggesting that you connect a 35 or 50-turn honeycomb coil in the grid lead of your secondary circuit to permit of reception on high wave lengths. RADIO LOG BOOKS. Used with any set. Satisfaction guaranteed. Postpaid 25c. Dealers wanted. Roy Stacy, Rockford, 111. Ivory Radio Panel: Grained white "Ivorylite" makes most beautiful set of all. Guaranteed satisfactory. Any size, ^" thick, sent prepaid, 3c per square inch. Sample free. E. P. Haltom, Dept. N, 614 Main St., Fort Worth, Texas. PATENTS SECURED Radio Inventions a Specialty Trade Marks Registered WRITE US Mason, Fenwick & Lawrence Patent and Trade Mark Lawyers Washington, D. C. New York Chicago ESTABLISHED OVER 60 YEARS Matched Transformers For the Ultradyne Circuit 1 Input Transformer and 3 Intermediate ton (\r\ Transformers if^U.UU Low Loss Tuning and Oscillating Coils, * A (\(\ per pair v 1.\J\J Full instructions and Blue Prints furnished with each Kit. Absolutely guaranteed. These transformers are suitable for any Super-Heterodyne circuit. Put up in handsome Kit display box. Special discount to dealers. Prompt delivery. Write for special circular. SYPHER MFG. CO., 1524 Fernwood, Toledo, 0. Users everywhere report Mffraeo Tuned Radio Frequency receivers pick up programs coast to coast; outperform sets three times as costly. Send for proof they are radio's most amazing values in powerful longdistance sets. One tube guaranteed, completely assembled outfit.as illustrated, list $14. 35. Three tube ^guaranteed loudspeaker outfit, list $29.50. SEND POSTAL TODAY for lateet bulletins and special offer. It will interest you. fMIDWEST RADIO CORP'N Ptsmeer Buildere of Seta 437M E. 8th St., Cincinnati, O. The Crystalstat PRICE $050 The Ideal Reflex Detector but equally suitable for crystal sets The Crystalstat embodies the following features: A super-sensitive crystal in an air tight enclosure. A brush cat whisker of gold tinsel strands. A micrometer adjustment by means of which the most delicate adjustment may be had. The multiple contacts of fine gold filaments prevent howling and gives light but sure contact. The crystal is our wonderful Star-ite, the pick of the Earth's best crystal. The Crystalstat attaches through one 5/16" hole in the panel so that only the control knob shows on the face of the panel. Packed in one dozen lots for dealers Ask your dealer to supply you or you may send for one C. O. D. with your money back if not completely satisfied. DEALERS and JOBBERS please get our catalog of crystals and detectors and our liberal distributing proposition. Interference from Neighbors (11314) MOR, Kalamazoo, Mich. By accident I discovered that the vibrations from a battery charger make a constant hum in the receiver. After several experiments I found that the vibrations from the battery charger in the neighborhood can spoil the night's entertainment for the whole neighborhood. Having seen nothing in your paper about this, I thought it wise to call your attention to it. The only remedy I see for it at present is to educate the neighbors not to recharge their batteries during Radio broadcasting hours. A. — In order to overcome the trouble which you report as resulting from the operation of a battery charger in your neighborhood during broadcasting hours, we suggest that you persuade the person or persons operating the charger to erect a wire screen around it and ground the screen, also connect two good quality .5 mfd. fixed condensers across the A. C. line in series and ground the center point. This will do away with much or all of the annoying hum which you have experienced. Men to build radio sets in spare time. Leon Lambert, 501-H Kaufman Bldg., Wichita, Kansas. It's your money and you can spend it for tubes or batteries if you want to; but I can show you how to bring distant stations in on a simple crystal set. Same plans increase range of tube sets also. Copyrighted plans $1.00. Complete parts for long distant crystal sets $5.00. Leon Lambert, 501 Kaufman Bldg., Wichita, Kansas. Send No Money LOG for YOUR Radio Record for all stations TOUR set gets. Spaces for call, city, location on each dial on TOUR set, and remarks. List alphabetical by wave lengths of 500-watt 'stations or over. Log cards in neat, durable rippled binding. Only $1.00. PREPAID if you prefer to pay with order. MONEY REFUNDED if Not Delighted Send Order today — NOW. A postal will do. RADIO PRINTERS, Dept 8412 MENDOTA, ILL. i-RatterV wst JLI Crystal J Gets 1000 Miles on 1-Tube Reflex Sets Get real performance from your reflex set with the Battery Crystal. Operates loud speaker on local stations just like big receiver. You can find more stations and a lot more volume than ever before. The Battery Crystal is the zenith in crystal work — with reflex sets the smoothest performance and greatest volume yet obtained. Send money order or we will ship C. 0. D. The A. H. Miller Radio Co. Special offer to dealers and Set Mfrs. 1255 W. Grand Blvd. Detroit, Michigan Miller Metal CRYSTAL 10 TUBE BRINGS IN THE WORLD" ATLAS MATCHED TUBES INSTRUMENT TESTED Made in all standard types. Guaranteed to function efficiently in the most exacting circuits. Every Atlas Tube is individually instrument tested. Try them 30 days. Money refunded if you are not delighted. At best dealers or direct «b from us. Our guarantee includes safe delivery. 32-° Special Offer At no extra charge, we will furnish selected Atlas Instrument Tested Tubes in matched sets for Reflex, Neutrodyne. Radio Frequency, Superheterodyne or other sets. They will improve the performance of any set. DEALERS: Atlas Matched Sets are in great demand. Write or wire for proposition THE R-S-K CO. 311 Caxton Building 771 Ellicott Square 609 Chamber of Commerce CLEVELAND. 0. BUFFALO, N. Y. PITTSBURGH, PA.