Radio Digest (Apr 1925-Jan 1926)

June 13, 1925 RADIO DIGES T— Illustrated 21 Simple Shockproof Socket Mountin; Vibrations Stopped by Mounting on Inner Tube The accompanying illustration shows a two gang shock proof socket made of four parts generally found in any amateur Radiophan's shop. This works out and looks very neat if properly made. The 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 drawing shows sockets for floor mounting but the sockets can be supported on brackets as well. Just the thing for WD11, 12 and 199 tubes. Make sure to place mica under the socket bases. This support stops the humming sound when using small tubes, especially amplifiers. — F. W. Steffen, Hartley, Iowa. Expense in Excessive Voltage The use of excessive B battery voltage In the effort to squeeze the utmost volume from a Radio set is a very expensive pleasure. It is the habit of many to employ 90 volts of plate battery and then to detune local stations in order to avoid overloading the loud speaker. This is equivalent to slowing down a motor car by applying the brakes without shutting off the gas. Since most Radio reception is done when tuned to local station, It is frequently possible not only to operate at the lowest filament voltage but at plate voltages of 45 and 67% in• stead of 90. A typical case is that of a well-known make of four tube receiver, equipped with a C battery having one • if tuned Radio frequency. Its eurrrnt drain with 90 volts was 7 milliamperes, PLAN OF TUBE SHOCK ABSORBER 'OOP Strvps but by reduction of plate voltage from 90 to 67 volts the plate current fell to 3 milliamperes, a saving of 57 per cent in plate battery drain. Increasing Tube Life Reduction of filament voltage not only reduces B battery drain but effects a substantial increase in the life of tubes and in A batteries. An overload of 5 per cent above rated voltage cuts in half the life of a tube, while continued operation at 5 per cent below rated voltage may often double the life of a tube. Since A and B batteries and tubes represent most of the upkeep cost of a Radio set it is thoroughly worth while to affect such substantial savings as 50 per cent, readily possible through economical use of plate and filament voltages. Those listeners who find it necessary to get the utmost out of their sets for long distance reception should do so by using high plate voltage, but when listening to local program take advantage of the saving resulting from the use of reduced voltages. Home Battery Truck To prevent the Radio batteries, chargers and testers from having things stacked on CHARGER. top of them the safest place to keep them is under a shelf. A board fitted with "pep Vtff your radio for good summer reception JEFFERSON TUBE REJUVENATOR keeps tubes like NEW/ Y OU can't pet Rood summer reception with weak tubes. All radio tubes weaken with use — especially in summer when burneJ at higher voltage. Keep your radio tubesefficient this summer with the Jefferson Tube Rejuvcnator. Just attach to a convenient electric light socket — "bring back" each tube in 10 minutcsl Repeat once a month — note how it improves reception; DOUBLE! and treblks tube life, and saves batteries. It's wasteful to be without one; it'scconomy to own one. Takes large or small tubcs-201-A, 301-A, UV-199. C-299. Fully guaranteed. Get yours now. At leading stores selling radio. If your dealer can't supply you, send $7.50 to JEFFERSON ELECTRIC MFG. CO. 501 So. Green St., Chicago, 111. Makers of Jefferson Radio. Bell Rinsing and Toy Transformers; Jefferson Spark Coils for Automobile, Stationary and Marine Engines: Jefferson Oil Burner Ignition Coils and Transformers. For Home Use rollers will be a wonderful help in handling these somewhat awkward Radio necessities. Finish the board with acid resisting paint. — Bertha Morey, Ottumwa, Iowa. Single Tube Circuit The illustration herewith shows a hookup with which I have lu.d very good results. My variocoupler is an old style one and it was necessary to place variable condenser C across the secondary in order Z2.\y. to reach the higher wave lengths, but it does not prevent me from getting the lower meters also. If your coupler is wound according to present requirements you can dispense with this condenser. The condenser CI is a plain 23 plate. — Arthur Reglein, Chicago, 111. Adding Selectivity to Set In the construction of the additional coils use one spider web form and wind on two wires, one ten turns more than the other. For instance, if your original tuner coil C has 45 turns, make the coil A 40 turns and coil B 50 turns. Disconnect the input of the set from the usual coil D and make connections as shown. Place an 11-plate or 23-plate variable condenser in the antenna circuit. The coils A and B are tuned simultaneously by the 24-plate condenser F. This automatically tunes out stations having a slightly different wave length on each side of the station wanted and narrows down the static band. If this is properly assembled it will make a very sharp tuner for the regenerative set. — Wi Harvey Merwin, Jensen, Fla. Voltage Regulation A potentiometer is a device which permits a lower voltage to be obtained than that of the source of the current. Its use in Radio receivers is principally in connection with the grid return voltage regulation. It is connected across the A battery and its movable arm goes to the grid connection. Crystal Used as Grid Leak Grid kaks play an important part in the construction and operation of most regenerative sets. An ordinary crystal detector of either the double mineral or the catwhisker type may be used in place of the usual grid leak. A good mineral, when properly adjusted, will work wonders on DX, Through the Locals — > ALLAMAX Reaches Out Every AlL'Amax Set, wherever it may be, brings to its owner his choice of all the beauties in the air. Every day come more and more letters to our office, telling of the long distance reception, almost unlxlicv' able on a threetube set, which has rewarded the owners of All-Amax. Remcmlxr, too, that All-Amax is c<m7f)!etcl;y7?i<mii[t'cl on panel and baseboard. You can wire it in one delightful evening, following simple photographic instructions. ALL-AMAX SENIOR, three tubes and detector ALL-AMAX JUNIOR, one tube and detector . . M2.00 Prlrr, $22.00 ALL-AMERICAN RADIO CORPORATION I . N. KAULAND, President 2640 Coyne Street ^—^xx*+ Chicago ■j)f **r-i— i All-American