Radio Digest (July 1924-Apr 1925)

August 2, 1924 RADIO DIGES T— Illustrated Selective Split Variometer Circuit Halifax, N. S., Canada, to Hastings, Nebraska Accompanying this article is a diagram of a two split variometer hook-up. This circuit can be used with any detector tube. The two variometers should be 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 inter ested 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 placed side by side and about 2 inches apart. The rotor of the first variometer is the primary coil. The rotor of the second variometer is the feedback coil. The stator of both variometers are the secondary coils. The two inner ends are bridged with a 23-plate condenser. — M. J. Rondean, Halifax, N. S. HOOK-UP FOR LOW VOLTAGE TUBE Spare Parts to Keep Set Ready A fully equipped Radio set includes not only the parts actually in use, but tools and spare parts for emergency use. Besides the every-day tools such as pliers, screw drivers and other necessary implements, the Radiophan should be supplied with apparatus that keeps his batteries in good shape at all times, and others that may be substituted when those in use break down. A storage battery charger will more than repay the fan for its cost in saving trips to charging stations, besides cost i<».<i -i» in t Super Crystal New Non-Metallic Housing Eliminates Scratches & Squealing Wonderful • new crystal — hag millions of sensitive spots — long life — cannot short circuit. FITS ANY STANDARD DETECTOB At your dealer — otherwise send purchase price and you will be supplied postpaid. Ask for reflex circuit 120. « /ftas. Freshman (o. Inc. § J| S£cW*>l Condenser s&ocfactt 106 Seventh AvcntM, New York City rt . ■ ■ 4 ym^-ymf* Munn ■ » n\ iW and Re-radiation/ Yo QukkkWlm or lightning < Why pay $10.00 or more to have an aerial spoil the appearance of your home? Antenella eliminates all unsightly wiring, lightning arresters, etc., and precludes the possibility of dangerous grounding on a power line. It also stops "canary bird" reradiation from nearby oscillating sets interfering. ANTENELLA is not only a real distance getter, but also overcomes troublesome static. At your Dealer, otherwise send purchase prire and you will be supplied postpaid. for Circular A-40 resliman(p.lnc. Condenser }&cc/ucts I 106 Seventh Ave., New York of charging. A hydrometer is necessary to keep tab of the battery solution, and a bottle of distilled water is another necessity. The battery should be kept on a rubber or a trap to keep the carpet or floor from soiling. A spare tube should always be on hand, in case one in use burns out. And for the fan who likes to test various hook-ups, test clips can save him from useless soldering jobs. When the fan finally decides on a "permanent" circuit, his electric soldering iron, with its accompanying rosin powder and solder, comes in handy. Condenser Insulation A small insulating bushing set in the metal end plates of a variable condenser mtm&m&mmem m Send 10 cents for Shamrock "Radio Builder's Guide Book" Contains 10 sets you can build from §15 to $50. SHAMROCK MANUFACTiraiNG CO. Dept. 23A, Market St. Newark, N. J. SHAMROCIf ILJrfiFoa SELECTIVE TUNtNG^m^ S^&j^W9^WRKt4£ Dealers Need This* 200% Profit The new FAHNESTOCK Display Case Will stimulate your sales of Fahncstock EaJlo Products. 14 of the most popular styles and sizes are included. Shows the purchaser instantly the correct piece for his set. A constant invitation to buy Fahnestock Products. Dealers aro offered 200% profit on each case, an unusual offer on standard merchandise. Price to Dealer $17.50 West of Mississippi 18.50 Transportation prepaid when money order or check accompanies order. Subsequent orders at regular price of $20.00. Contents Retail for $51.50 Refills will be supplied at the regular 100 lot prices, shown in catalogue, which conies with case, less discount shown on enclosed sheet. Send check or monev order, today. FAHNESTOCK ELEC. CO. LONG ISLAND CITY NEW YORK causes a concentration of the electrostatic field, resulting in large losses. As a consequence such condensers work very poorly compared with those having a larger area of insulation. ilNBIDE'AERIAL i'.CEiLiNGg'^ga . ,...•_ ... j ui.'iiarwngf^ L0Na ■ ', NOT AFFECTED BY WIND, K4W; SNOW OR LIGHTNING ', ; CERTIFICATE OF APPROVAL by on* of Urgrat Radio LABORATORIES .ct . PRICE J» POSTPAID or 55.00 Hud 4 ADDRESSES SET OWNERS : Mr A.k .bout our NOISE KILLER ~BO , , ; INTER-STATE SIGNAL CO., Dept i COLUMBUS, OHIO1; l^ili'iifrt)i'»lVlfi>^.l-»'it^ii««f>n-->Ul-i4fiHi-<Tl^^o<- — U. CORBETTO ABINETO FOR QUALITY Style K — Illustrating special Cockaday (rear slot not included in other cabinets). Prices — Cash with order or C. Genuine Oak or Walnut Mahogany or Size Finish Mahocanj 7x10x8 $3.06 7.\lL'x8 3.24 7x14x8 3.42 7x18x8 3.87 7x21x8 4.23 7x24x8 4.59 7x26x8 4.86 7x30x8... 5.85 $4.50 4.36 5.13 5.80 6.34 6.S8 7.20 8.77 O. D. Genuine Oak or Walnut Mahogany or Size Finish Mahogany x36aS $6.84 $10.26 'X40ac8.. 7x9.. 7.74 5.49 7.56 9.00 8x36x8.. 8x10x8.. 8x26x8.. Corkaday as illus 5.85 11.61 8.23 11.34 13.50 8.23 8.77 Hinged top and grooved front, also hinged to base cabinets in stock at above prices. Mounting boards 25c, above 30" panel 50c. All cabinets nicely moulded top and base. Varnished finish carefully hand rubbed (Adam Brown Mahogany). Accurately made of best kiln dried lumber and well packed for shipment. WRITE FOB FREE BOOKLET illustrating six styles. Special cabinets to order. TERMS— CASH WITH ORDER OR C. O. D. Corbett Cabinet Mfg. Company 1415 East St. 5323 N. Carlisle St. PITTSBURGH, PA. PHILADELPHIA. PA. PERFECT BATTERY SWITCH Retail Price 60c At all Radio Dealers and Jobbers Easily Installed In Any Radio Set The Bradleyswitch is so easily installed that thousands of radio set users are protecting their A-batteries and tubes accidentally burning by putting a Bradleyswitch on the panel. Avoid discharged batteries due to accidental overnight burning of tubes. Be safe and install a Bradleyswitch, now! ALLEN-BRADLEY CO. 290 Greenfield Ave., Milwaukee, Win. Cutting Aerial Length for Slimmer Reception Now that the static season is getting under way, many no doubt are under the impression that they will be unable to enjoy Radio without a set sensitive enough to utilize a loop aerial. There is no doubt but what this type of set is preferred, however, if you have a good regenerative set with one or two steps of audio frequency amplification, with the correct antenna system very good results can be obtained. There is much to be learned about aerials and antenna systems. Experimentation will bring results for your particular set and how to procure the best signal strength. First your outside aerial should be reduced to a single wire not over 100 feet long. Remove the ground connection and connect a single turn of wire around the picture molding of the room as a counterpoise. Very good results can be obtained by connecting a loop in series with a short outside aerial, which should be a single wire 20 to 40 feet long. — Roy Blain, Omaha, Nebr. Bankrupt Stock Cunningham Regenerative one tube long range sets $9.00 Each Formerly sold at $32.50 No Circulars. Order from This Ad. This set with tube, phones, all batteries and aerial complete, dJOl f\{\ ready to use, for ip£*l..\J\J Prepaid while they iasf. S. A. TWITCHELL 1925 Western Av., Minneapolis, Minn. PRE-AMPLIFIER Registered Makes Summer Radio Practical THE TWITCHELL PRE-AMPLIFIER is a powerful Radio Frequency Amplifier attachable to any receiving set. It brines in many distant stations which you cannot hear without it. Brings in with tremendous volume those you now hear only faintly. Makes your set selective. Prevents re-radiation. Price complete with tube $25.00 Shipped Prepaid S. A. TWITCHELL MINNEAPOLIS, MINN. 1925 Western Ave. SENT FREE Tladtol Then Get Our FREE Bulletin No. 94 It shows recent developments and improvements in parts and the kind you must use if you want the best in Radio. Send for this book today. mtmm Quality Unsurpassed— For every known "Hook-Up" ALL GOOD DEALERS SELL THEM $vtm\tr fatlrlt famp&n$ 3810 Ravens wood Ave