Radio Digest (Apr 1925-Jan 1926)

RADIO DIGES T— Illustrated June 13, 1925 Questions and Answers Walters' Tuned 3. F. Set (137ST) RCP, Rich Hill. Mo. I desire to build the low loss tuned radio frequency receiver described in your magazine by Mr. George Walters. To quote exactly in part one he said, "It would be possible by the use of switches, to increase the efficiency at the higher wave lengths so that, when one wished to receive stations above 425 meteis, he might throw in more primary turns in the second and third R. F. transformers -which would bring the regeneration almost up to oscillation and the high efficiency of the lower wave lengths would also then be found at higher wave lengths." I would desire to know how many turns to add, how many and how often to take off taps, also what make of A. F. transformers and condensers Mr. "Walters used. A. — We have your letter of May 15th. To obtain the effect which you mention in your letter of May ISth of getting regeneration on all wave lengths in the tuned R. F. set we would suggest that you add 10 more turns to each primary of the second and third transformers and tap these additional 10 turns every two turns which will put a five-point switch on your second and third primaries. When you tune for wave lengths above 400 meters you will find that you can cut in four to six more turns and that when you are tuning to wave lengths above 500 meters you can probably cut in 8 or 10 turns without the tendency to oscillate getting beyond control. Underground Antenna (13760) WFM, Mt. Clare, W. Va, I would like very much to have some information on Mr. E. T. Jones' underground antenna. I am using a Radiola VII B and would like to know what size coil would be the best to use. Also what he means when he says to use lead covered wire for the lead in. I am unable to locate such wire here. I would also like to know how much number 14 rubber covered wire should be used and what space should be left between the wires. I am a constant reader of the Radio Digest and will thank you very much for this information. A. — Practically all of the information available at this time is contained in the two articles by Mr. E. T. Jones which appeared in our March 28th and May 16th issues. Lead covered wire is frequently used in automobile ignition systems and also in the wiring of houses. The wire is enclosed in a tube of lead, and you should be able to obtain it from any distributor of automotive or electrical supplies. If you cannot get information on it locally, we would suggest that you write to the Belden Mfg. company, 23rd and Western avenue, Chicago. The two articles mentioned clearly state how much wire is to be used and you can use any length between 125 and 200 feet of heavily insulated rubber and braid covered wire. The spacing between turns of the flat spiral can be anywhere from Vi to % inch with an outside diameter of two to three feet. This matter of spacing and outside diameter is not particularly important providing the diameter is not less than two feet. A good dependable ground should be used in conjunction with this device and we are quite sure that 90% of your static interference will be eliminated. NEW IDEAS WANTED Well-known Radio Manufacturer, whose products are nationally advertised and sold everywhere, wants new Radio device t<. sell. Will pay outright or royalty for Idea or invention which is really new and saleable. Address Mr. R. F. Devine, Room 1101, 116 West 32nd St., New York, N. T. IMPROVES RECEPTION ' Giyea wonderful results with any radio set. Not attached to, but mereplaced under tho telephone. Price One Dollar. Complete with insulated ni and simple Instructions. At Yvur Dealer or Mailed C.O.D. on 3 days approval. f}Yi> . Antennaphonc Co., 90 West St., N. V. C. ^4^ !/#■ SEND IN YOUR Paralyzed Tubes to be Restored to Health in Our Laboratory Qjj Qf of your worn-out tubes can %JO /O be put in first class condition. n REACTIVATE IJV-201A, C-301A, C-299 and any other thoriated filament Mlas, Magnatron, Q9e Forest, etc. We cannot reactivate tv-2oo. r 300, WD-11 or wd-12 tubes, nor can [vate turned out It Costs Yon Only $1.00 e your tube ho that 11 operates satisfactorily. If we arc not successful, our charge Ll only 25c. Why o for new luhes when we can make yours as Rood as new for only Jl.Oft. MAIL IN YOUR TUBES TO US FOR PROMPT RETURN, Pared Post, C. 0. D. A. O'CONNOR & COMPANY 9703 Euclid Ave. Cleveland, Ohio REGENOFLEX CIRCUIT COMBINATION LIST OF PARTS 2 Variable condensers, .0005 mfd.$11.00 1 Variometer 5.00 Materials for inductance L 1.25 2 Tube sockets @ 1.00 2.00 2 Rheostats @ 1.00 2.00 1 Midget variable condenser 1.75 1 Audio frequency transformer.... 4.50 1 Grid lealr. and mounting' 1.50 Materials for unit 1.2, L3, L4, L5 7.00 2 Fixed mica condensers .00025 mfd 80 1 Fixed mica condenser, .0025 mfd 50 1 Fixed mica condenser, .001 mfd. .40 1 Fixed mica condenser, .002 mfd. .40 1 Fanel 7x18 2.25 1 Cabinet 3.00 Miscellaneous small parts 1.00 Total cost $44.35 THE regenoflex circuit is a unique combination of tuned Radio frequency, reflexing, neutralization and regeneration. That it is perfectly practical has been shown by the many sets utilizing it now in use. While the antenna circuit as a whole is tuned by the condenser CI, the turns in the antenna inductance (L) may be varied to vary the ratio of turns between this coil and the variometer (L-l) the first grid circuit. The turn-ratio may thus be 1 to 2, 1 to 3, 1 to 3 Vz, 1 to 4 without throwing the antenna circuit out of resonance. The grid circuit is tuned to the frequency of the incoming program by the variometer. Neutralization of the capacity feed-back Men to bnild radio sets In spare time. Leon Lambert, 501-H Kaufman Bldg., Wichita, Kansas. Static "HOW TO KEEP STATIC OUT OF YOUR RADIO" New Copyrighted Plans, $1.00 LEON LAMBERT WICHITA, KANSAS of the first tube is accomplished by inductance L3 and capacity C2. It is inductance L2 which, coupled to L4 passes energy to the detector tube connected to L4 and variable condenser C3. Regeneration is accomplished in the detector tube by coupling L5 of its plate circuit to inductance L4. The plate circuit is continued through L6, which is the primary of an audio frequency transformer and the audio frequency component of the energy in this circuit induces energy in L7, the secondary, at audible ferquencies. This secondary, L7, being in the grid circuit of the first tube, this tube again handles the signals, but now at voice frequencies, and passes them into L2 again. These frequencies have no effect on L2, but pass through to the leads labeled "Output," which may go to the phones another audio frequency stage or a pushpull amplifier. While the exact constants of the commercial form of this circuit are not available, they may be approximated. Ll to be wound with 40 turns on a 2% -inch tube tapped every 5 turns; CI to be a .0005 maximum variable condenser; Ll to be a standard variometer with its stator at one end of L, the turns running in the same direction; let C2 be a midget variable; L2 to contain 15 turns and L3 15 turns on the same tube; L4 to have 50 turns and L5 40 turns on a rotor within L4; C3 to be .0005 variable ELLCITE SUPER RADIO RECEIVER. No Tubes, A or B Batteries. Operates Speaker. Clarity, Distance. Write Ellcite Radio Co., Box 193, Buffalo, New York. •A RECHARGEABLE "B"% I WITH A STRONG GUARANTEE '"\ § The SEE-JAY BATTERY has met all tests and = = Is endorsed and recommended by the Washington = = Information Seryice Bureau and thousands of : = satisfied users. Genuine Alkaline connected ele = 5 ments, strictest Government test passed. No \ = drilling or wiring. Connectors crimped under 1,000 : = pound pressure. Save . time, temper and money. : = Essential parts for 100-volt unit, $7; 140-volt, $10. : = Why pay more? Complete assembled batteries, solu = tion separate, shipped dry, 100-volt, 512; 140, $10. : S See-Jay unit sold on money-back guarantee. Write : = for literature and send 20c for improved sample cell. : = SEE-JAY Battery Co., Dept. D, 915 Brook Ave.. : = New York. Mall order service. = | WHOLESALE AND RETAIL ?• 1 1 U > 1 1 1 1 1 1 1 1 1 1 1 J M I M 1 1 1 N » 1 1 1 1 1 1 1 1 1 1 r 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 [ 1 1 1 1 1 1 1 1 1 1 W 1 1 1 1 ] 1 1 1 1 M 1 1 r m up your set with good tubes COME radio fans don't expect much "pep" ^ from their portable sets. "Oh well, only using the small tubes," they explain. But they have quickly revised their ideas when they switched to MAGNATRON DC-199 tubes. You'll never realize how important tubes really are until you adopt MAGNATRONS. Your dealer has them! CONNEWEY ELECTRIC LABORATORIES Magnatron Building Hobofcn, H J and vernier; C4 to be .0025 mfd., C5 to be .001 mfd., C6 to be .002 and C7 to be .00025. The true experimenter will enjoy this circuit. He has the assurance that it wiH work when correctly assembled, the values are nearly right as listed, but considerable experimenting with the reversing of leads to L3 and L5 and the turns on L3 will be necessary. A. B. C. RADIO COURSE (Continued from page 20) which constitutes the other plate of the cell. The electrical connection from the mixture of carbon and manganese dioxide to the positive terminal of the cell is made by means of a carbon rod imbedded in the center. The manganese dioxide is the depolarizer and during the use of the cell this oxide is reduced to a lower state of oxidation. Dry cells as manufactured by different companies differ somewhat, particularly in the construction of the positive plate and the combination of chemicals and materials used in forming the positive plate, but in principle they all are the same. Dry cells are made in a wide range of sizes and shapes to meet certain requirements as to space limitations and the current they will be expected to supply. The larger the area of the plates thegreater the current and amperes-hour' capacity of the cell. That is, a cell with large plates is capable of supplying a larger current without serious effects due to polarization, than a small cell can supply, and it can supply this current for a longer time. The product of the current, times the time in hours that this current is supplied, is called the amperehour capacity of the cell. (Having' shown primary cells as producers of electrical energy from, chemical action, Professor Moreton next week considers storage batteries as containers of that energy. — Editor's Note). If you want a C battery in the audio outfit, connect the P posts on the transformers, run the negative C to this wire and hook the positive side of the C to the negative A battery line. i^L by practical, personal training in the tyeat sfwpi fCOYNE You don'tneed education or experience. COYNEtrained men earn , $60 to $200 a Week ' SSSSr ...Wnk Free Railroad Fare gUZre^'lihti'go' also FREE courses In Radio and Auto Truck and Tractor Electricity. Ask for Big. Handsome FREE BOOK containing 151 actual photos of electrical methods and operations In BLj Shops. COYNE ELECTRICAL SCHOOL Own. A -647 1300 W»»t Morrison Strmt, CHICAGO, ILLINOIS OLD MAN STATIC "KILLED" AT LAST Statichoke Has Startled the Radio World — Insures Clear, Long Distance, Summer Reception. Kansas City, Mo., June 5 (Special) — The long promised invention which insures clear, long distance, "summer radio" without the agony of static, has just been announced here. Radio ex-, perts and fans who have tested this new imported invention, pronounce it marvelous. Awarded Certificate of Merit by Radio News of Canada. In addition to reducing static to a minimum, the Statichoke increases the volume as well as clarity of distant reception, sharpens the selectivity of tuning in, eliminates that harshness of the tubes so noticeable on local loud speaker reception and acts as a safety lightning arrester. The Statichoke somewhat resembles a small transformer, and by a system of coils it allows only the correct current value to enter the set, choking out other high current variation from the aerial, which is passed off through a secondary ground connection. So confident are the American distributors that Statichoke will pive you clear, lonff distance^ summer reception that they hare set aside 25,000 units for initial distribution direct to the radio fans, at a special price of only $2.50 each. If interested write today to Radio Dept.. Imperial Laboratories, 95S5 Coca Cola Bids.. Kansas City, Mo.i and the Statichoke will bo sent you by Insured mail. Write today as this is a special oner and may not appear again.