Radio Digest (July 1924-Apr 1925)

January 31, 1925 RADIO DIGES T— Illustrated 21 Improvements on De Forest Circuit Old Faithful Sure Fire Hook-up Gives Results While there are numerous circuits and methods of improving same are beingplaced on the market every day they nearly all hinge on the old De Forest WORKSHOP KINKS EARN A DOLLAR— THERE are many little kinks worked out at home that would aid your fellow Radio worker if only he knew about them. There are new hook-ups, new ways of making parts and various unique ways of operating sets that are discovered every day. Radio Digest is very much interested in obtaining such material. Send them in with full details, including stamped envelope, so rejected copy may be returned. The work must be entirely original, not copied. RADIO KINKS DEPARTMENT Radio Digest, 510 North Dearborn St., Chicago regenerative (Armstrong) and most of them use speech improvements with which cost prevents the mere novice from experimenting. This hook-up can be made by any. one familiar with the common regenerative hook-up and can use a few tools. For quiet operation, clarity of music and speech, ease in construction, small first cost and up-keep, the pinkedyne cannot be exceeded for distances on loud speaker reception up to 1,500 miles. After the feed back that may be encountered by too close placing of transformers, tubes, sockets, etc., in a set, the next most troublesome source is the B battery. "When it is considered that the plate circuits meet at the B battery jt is indeed not very difficult to understand that inter-action between stage's is a frequent occurrence. If it were not' for the cost it would be indeed better to .use separate B batteries for each stage and' tube. The arrangement of chokes and condensers, as shown in the piiikedyne, will to a great extent solve this problem and is well worth trying by both the novice and DX hound. The chokes may be the ordinary primaries of the bellringing transformers. The condensers should be two mfd. capacity. The main function of the chokes CH is to prevent the audio-frequency currents from flowing into the B batteries, while they allow the direct current from the B battery to flow to the plate. The condensers C, by-pass the audio TUBE RADIO $ SEI 10 DAY! FREE TRIAL Coast to Coast Direct from Factory to you at Less Than Dealer's Cost JSr^.'.^JfiSS? efficient TUNED RADIO FREQUENCY circuit. Approred by America's Leading Radio Engineers and the Institute of Standards. Easy to operate. Dials can be logged. Tune in your favorite stations instantly, on the same dial numbers every time. No guessing. Mr. Howard, of Chicago, said, "While 6 Chicago Broadcasting Stations were on the air. I tuned in 17 out-of-town stations from 40 to 1 ,000 miles away . on my loud speaker, very loud and clear, aa though they were all in Chicago." * nAc/>r!n4inn> 5 tube setComes completely asl/C9l>rip(IUIli sembled In beautiful mahogany cabinet, size 25x7^jx7lf. Has 2 stages Tuned Radio Frequency, Detector and 2 stages Audio Frequency. Equipped with the highest quality, approved mtandmrd low'loss parts. Genuine Bakelite Panel, Bakelit* dials. Use any standard tubes and batteries. 10 DAYS' FREE TRIAL Don't miss this chance to bay this high grade 6 tube Bet direct from factory. Regular value $100 00. Ourfactory price only $38.50. Send no money. Sign and mail coupon. Pay only $38.50 when delivered, (plus small transportation charges). Try it 10 days. If you are not delighted with results —if you do not consider it equal or better than any $100.00 set, send it back and we will cheerfully refund your money. I METRO ELECTRIC CO. [ 400 N. Michigan Ave., Dent. 79 Chicago, III, (Gentlemen: Ship me on approval your 5 tube long tance radio set. I will pay $38.60 on arrival (plus tr dl«trans Iportation charges) with the understanding that if 1 am not fully satisfied after 10 days' free trial, I may return . it and you will refund my money. Name . Address. City PINKEYDYNE FEED BACK HOOK-UP ;-l — GROUND "A" frequencies that are choked by the chokes CH and allow them to reach the filament but without having to pass through the B battery to do so. The very small coils RFC are merely very small radio-frequency chokes placed in the grid circuits of the two amplifying tubes to block stray radio frequency currents that may reach the amplifier. These chokes are constructed by winding eighteen turns of number 26 wire on a lead pencil and attaching to a piece of cardboard or bakelite for mounting on baseboard or in center of lead concerned. A standard variocoupler has been used with wonderful results. Also a standard low loss 23-plate condenser is used in the aerial circuit. A .00025 grid condenser is used with about a 2 meg. leak. It is worth the using of a vernier rheostat for the detector tube, while one rheostat may be used for the two amplifier tubes if desired with about as good results. One 10 to 1 audio transformer is used in the first stage and a 3 to 1 in the second. Any standard wet battery tube may be used which will detect in detector circuit and amplify in the. amplifying circuits. From 18 to 22% volts B battery for detector and 45 to 67% in amplifying circuit is used, according of course to the kind of tubes used. This can be easily arrived at by trial. Six-volt wet battery is always preferred in this kind of a hook-up. — M. C. Williams, Rantoul, Illinois. Remove Moisture in Coils Broad tuning and weak signals are often the result of moisture collecting in the insulation of the tuning coils. They may Effarsee The "Easy-to-put-up" Aerial Effarsee Portable Antennae — curtain shaped — can bE put up anywhere, indoors or out, in a jiffy, and they will work on all types of sets from superhetrodynes to crystals. Give loud speaker volume on distance with sensitive sets. They improve reception by reducing static and noise. Give you real music. They avoid the trouble of erecting an outdoor aerial. Greatly increased volume is possible when Effarsee is connected in the circuit with outdoor antennae. Dealers use them for demonstrations. Much better than a loop or indoor wire aerial. Three Sizes $1.00, $1.50 and $2.50 If your dealer can't supply you send us the price and we will ship at once. Money back if not satisfied. The Fishwick Radio Company 512 Edwards Building Cincinnati, O. arsee PORTABLE ANTENNAE not feel moist to the hands, but the dampness is there just the same. You will be surprised at the improvement that follows a good drying out in the sunlight or by placing the apparatus near the stove. .50 5*** ACCURATVNE MICROMETER CONTROLS Adjustable Grid Leak Is Made from Rheostat A very efficient grid leak can be made from a discarded rheostat by removing the resistance wire and putting aNheavy BRA55 STRIP MAKES CONTACT ON PENCIL MARK PENCn.rTAB.rC RHEOSWTARM pencil mark in place of it. The arm will make a contact on the pencil mark as it rotates, thus varying the resistance. — G. Ross, Houston, Texas. on They make logs « *tting a W «*^JSve.The ratio Nation" P°SS in Royal Brass tt*isVli*>h $2-50. latin SuveorJ|Sed(24k) 'h;%qTCut|iticrodvne -«opCJr"JSr&t» sell tor knock.dowj *^ex Super $97-50. TV^P. Cabinet ^r Radio &-«• po AP^l||m5othSt.^jg 14i%!"^.^<-> X^l ■ '■' * » ■ftPEXS VE«HIE» No More B Batteries Make Your Own B Current Supply unit and run your set from regular A. C. house current. Easy to hook-up as a crystal set. Operating cost is negligible. Furnishes up to 125 volts B current. No A. C. hum! The Molliformer filters it out. Does not use tubes. Complete essential parts and instructions to make unit $18.50 Individual Parts Sold Separately Write for Literature C. E. JACOBS 2802 N. Kedzie Ave. Chicago The "Goode" Two-o-One A Le Ton d'argeat BY MAIL ONLY 2 .39 Postpaid QUARTER AMPERE AMPLIFIER— DETECTOR RADIO TUBE GUARANTEED SATISFACTORY All "GOODE" Tubes Sold Direct to the Consumer — No Dealer Profits $2.39 6.42 ONE— "Goode" Detector-Amplifier THREE "Goode" Detector-Amplifiers (All postage prepaid) The "Goode" Two-o-One A Tube amplifies or detects. It Is a quarter ampere, ire Yolti, standard baie silvered tube. Send express or postal money order or Mew York draft to — The Goode Tube Corporation Incorporated Owensboro (Dept. A) Kentucky