Radio Digest (July 1924-Apr 1925)

16 RADIO DIGES T— Illustrated August 23, 1924 R. F. AND REGENERATION (Continued from page 7) this amount. Connect this part of the filament circuit and try the tube illumination. If you have a volt-meter, use enough resistance to put 5 volts on the filaments. The tap to the other jack is taken at such a point that the voltage remains at 3 when all four tubes are lighted. All tubes together take 1-ampere, and the resistance of the unit should then be just about 1 ohm, and the tap is placed quite near the end, or just a quarter of the way down. The voltmeter may be used again here. This makes any adjustment of the voltage unnecessary, and when the battery falls low, the set will indicate the fact by its lower volume and disinclination toward oscillation. The C Battery This is an important item. The use of the C battery not only results in better amplification, but it cuts the B battery current in half and thus makes the B battery last twice as long as it would without it. Isn't that a real saving? The grid return leads of all the amplifier tubes are brought to the negative terminal of the C battery. You will note that the binding posts are distributed along the rear of the subpanel! Small holes are drilled at corresponding points in the rear of the cabinet and all connections made from the back. This keeps unsightly wires away from the front and in that way improves the set's appearance. With all connections made and checked carefully, set in the cabinet, tubes inserted and batteries, etc., in place, you are ready to put the set into action. First of all, insert the phones in the first jack, thus lighting three tubes. Set the coil L-l at about 45 degrees, and the tickler at the non-oscillating position. Then vary coil L-3 until the Radio frequency tube is on the verge of oscillation but not quite oscillating. The condensers should tune at approximately the same settings for the same wave length, and the coupling between L-l and L-2 adjusted for good volume, but not so closely that the antenna absorption prevents oscillation of the detector or makes the dial settings of condenser C-l very different from those of, C-2. The set is well adapted for antennae of various capacities, and will function well when connected to the electric lighting or telephone circuit through a .001 or .002 fixed condenser. With this form of antenna, the coupling will have to be re Nirjyt : Crystals of Quality Trade Mark Beg. (J. S. Patent Office. The B-JIETAL Loud Talking Crystal was the first really standard crystal offered under a reliable "complete satisfaction guarantee." and it sprang into immediate popularity, remaining at present in its third season, the best seller of any standard priced and quality crystal. B -METAL has kept pace with developments and has constantly been improved by the use of purer base materials, scientific treatment, and more care in inspecting and testing. The quality has gone up 1007o and the price is still 50 cents. No premiums are offered to Bell BMETAL, nor can Genuine B-METAL Crystals bo bought at less than standard price. If your dealer cannot supply you, send to us. We will send one only to anyone writing U3 and agreeing to pay promptly if satisfied. We want every Badlo owner to know what B-METAL Crystals are. Write today. Dealers and Jobbers please get our proposition iMimmhiMrWmsm 14»ri. 525 WOODWARD AVENUE DETROIT. MICHIGAN, dticed considerably on account of the relatively large capacity. Reception Range The set is extremely selective, especially on condenser C-2, and should tune through local stations successfully for stations of but slight difference In wave length. In New York City, for instance, KGO of Oakland is heard repeatedly with the set illustrated, without interference from locals or from Ti'LW or WSAI, only 3 meters different. KGO is on 312, while the Cincinnati stations are on 309. Of course, it may not always be possible to tune out WDAP if you live in Chicago and hear WKAQ, Porto Rico, even though the latter be a little "off wave." However, the circuit will be surprisingly sharp, nevertheless, for the regenerative feature improves the selectiveness wonderfully, and in this respect, selectivity is usually superior to that of a three control Radio frequency set, .as the neutrodyne. The ease of its operation, the absence of complicated controls, and the long range are recommendations aplenty for the tuned Radio frequency and regeneration combination. Its selectivity makes the receiver a pleasure to operate, for it's often but a half degree's touch of the vernier from one station to another. THIRTY-MINUTE A-B-C (Continued from page 13) Phantom or aerialless operation, coast to coast range, requires two good stages of Radio amplification or sometimes threat ahead of a good detector and two stage audio amplifying set. (Perhaps one of the most difficult things to do is to choose a receiving set suitable to your needs and what you can afford to pay for it. Mr. Edelman will tell you about this in the next issue. It will aid many a newcomer in Radio. — Editor's Note.) The Reader's View Tuning Aerials I notice many items in Radio Digest regarding the number of turns for the primary of a coupler, particularly the discussion in the issue of August 11. The following may be of interest: The amateur seems to forget that there is nothing mysterious nor arbitary in Build a FADA 5 tube Neutrodyne Receiver You can assemble one in a few hours. For distance, selectivity and loud speaker volume there's nothing better. The FADA 5-tube Neutrodyne outfit No. 167-A contains everything needed — the finest Neutrodyne parts that can he purchased. The FADA. "How to Build It" booh malr.es everything as simple as A, B, C. Buy the original FADA No. 167-A in the sealed package, $65.60. F. A. D. ANDREA, INC. 1581 Jerome Ave. New York FLa d i o The Kellogg New Eleven Plate Condenser The Kellogg Switchboard & Supply Company in keeping abreast of radio developments has found that the amateur and radio experimenter are interested in a condenser with vernier capable of being tuned from one to ten micro-microfarads. The Kellogg No. 610 condenser is designed to provide a vernier of minute capacity and that can be used as a bias. It also provides the greatest degree of efficiency in circuits requiring grid, micrometer or biasing condenser. Unnecessary wiring is eliminated when using this condenser. The number of pieces of apparatus to build a set is reduced. If your dealer does not carry Kellogg, write us giving his name. USE— IS THE TEST NO. 610 KELLOGG SWITCHBOARD 8 SUPPLY COMPANY 1066 "W. Adams St. CHICAGO, ILL. tuning. It is precisely like putting weights on one pan of a scales to balance a substance in the other pan. With a set and an aerial the latter acts as one weight, and the turns on the coupler act as additional weights. You put on weight after weight, or turn after turn, until it balances, or in other words is in resonance with the incoming wave. It is evident that the number of turns you add will depend on the value of the aerial. If your aerial is long and high, with several wires, it will be "heavier"; hence you will need but a few "weights" or turns to balance up. Below are some data as to tuning various aerials. It should be remembered that two aerials of exactly the same dimensions may not have exactly the same value. Very small aerial, 32 feet long, 12 feet high single wire, tunes to 400 meters with 57 turns on tube 4*4 inches diameter. Tunes to 517 meters with 86 turns. Medium aerial, 80 feet long, 35 feet high, single wire, tunes on 400 meters with 30 turns. Tunes on 517 meters with 48 turns. Larger aerial, 90 feet long, 50 feet high, single wire, tunes on 517 meters with 38 turns. Same aerial except with three wires spaced 3 feet apart, tunes on 400 meters with 18 turns. Tunes on 517 meters with 31 turns. In general, if your aerial is at least 80 feet long and at least 35 feet high, you will need at least 48 turns to tune 517 meters, more to reach 545 meters. Such an aerial should have a coupler wound with about 60 turns on the primary. If your aerial is under 50 feet long and less than 30 feet high, your coupler, using a tube 4% inch in diameter, should have not less than about 75 turns, in the primary. If the primary is wound with taps so that single turns may be cut in, or even three turn steps, no condenser will be needed in the primary, for crystal reception of local broadcasting; merely the coupler, crystal and phones are needed. With an aerial 90 feet long and 50 feet high, single wire and such an outfit I can hear WWJ or WCX local stations 40 feet from the phones in another room on a crystal. On exceptionally good nights this outfit brings in WGY, Schenectady, or WDAP, Chicago. ♦ 'A^ofRstiimiK^ioService' -THE ACCENT IS ON SEKV1CE" 14-16 Vesey St. NEW YORK VARIOCOtTPLERS $3.50 Workrite 180° Silk Wound $2.95 3.50 Fisher, Large, 90° '.. 2.75 2.75 Fisher. 180° 2.25 4.25 Special Bank Wound Coupler for Haynes Circuit (with diagram) 3.25 7.00 Ambassador Coil (with diagram) 5.50 VARIOMETERS $3.50 Workrite _ $2.95 5.00 Pathe Moulded 2.25 3.50 Fisher, Large 2.85 CONDENSERS $2.00 E. C. 11 plate $1.05 2.25 E. C. 23 plate 1.35 2.75 E. C. 43 plate „ 1.65 VERNIER CONDENSERS $4.00 E. C. 2 3 plate $2.25 5.00 B. C. 43 plate 2.95 PHONES $18.00 DR. SEI8T IMPORTED "SUPER «ft Qfk HEADSET" _...«<>0"~u S12.00 N. & K., Imported „ $6.90 The above items are just a few of our numerous attractive priced articles, which are contained in our BULLETIN OF RADIO PARTS. Gladly sent to you upon request. We are headquarters for "Radion" and "Bakelite Dilecto" Panels. The best panel material available. Mail orders promptly attended to. Will ship C. 0. D. unless remittance accompanies order. Dealers Need This The new FAHNESTOCK Display Case Will stimulate your sales of Fahnestock Eadio 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 are 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 Id catalogue, which comes with case, less discount shown on enclosed sheet. Send check or money order, today. FAHNESTOCK ELEC. CO. LONG ISLAND CITY NEW YORK As for the turns on the rotor — for crystal sets used for local broadcasting I have found that the rotor gives best results when wound with about 80 to 100 turns of about Number 28 to Number 36 wire; no phone condenser is then needed. I have had Kansas City on it. — F. C. Sutter, Detroit, Mich. Squealers Your very interesting periodical is looked for eagerly each week. You are now running a helpful series of articles on operating different makes of Radio receiving sets. I am prompted to repeat, of what use are all these things without "charity," and charity in this case means — if the user is not especially instructed to avoid re-radiation. Not enough stress is laid on this subject. I beseech your good offices to induce the manufacturers themselves to furnish with each machine instructions — and it should be fastened to the detector rheostat as a printed tag or tacked to the cover, or in some way brought forcibly to the operator's notice — how to avoid reradiation. Explain it to him first and foremost. Impress it on him that his set may be taken away from him if he allows it to oscillate. Inform him how he can tell if it is oscillating — by touching his finger to the bare aerial, or by the squeals when he moves a dial; tell him the whole story, and have each salesman impress the same thing on the purchaser. Single circuit tuners are not the only offenders, I am confident. About every night a new Radio recieving set is started up and for half the evening everyone else within a half mile has his entertainment spoiled. Most of the offenders would not do so if they knew any better, but no one impressed it on them. I hear folks tell how their children, little tots whom they wouldn't trust with their phonograph, can and do run the Radio set! Ye gods, just think of the helpless crowd of neighbors, doomed for a while, etc. You know the quotation. Get after them. Thanks.— E. Z. Lane, Mechanics Falls, Me. Take sufficient precautions to prevent crossing of storage battery terminals or wires. mmnnmmimi ■iwMjAVsi^siiy. Guaranteed .,M /,,, Send ; «fr , «j,Wfln«> '% am— a— — eaaaaw *** PERFECT BATTERY SWITCH = A Compact = Battery Switch The Bradleyswitch is a beautifully finished radio battery switch. It is extremely essential in sera using UV-199 tubes, to be sure the battery circuit is open when the set is put away. Easily installed. Pays lor itself many times in longer battery life. Try one today! ALLEN-BRADLEY CO. 290 Greenfield Ave., Milwaukee, Wis.