Radio Digest (Oct 1923-July 1924)

February 9, 192.', RADIO DIGEST — Illustrated 21 How and Why of Super-Heterodyne Receiver Chapter IV — Loop Aerial and Circuit By H. J. Marx WITH the completion of the superaudible transformers and the oscillator, the far) Is prepared to .start work on the assembly of his set. Many are no doubt wondering why there are three input terminals on all the cir cuit diagrams and how the connections are to be made. With super-heterodyne circuits, owing to their ability to pick up weak signals, it has not been necessary to use an outdoor antenna. The loop aerial is amply efficient and by its directional effect makes the best type of energy collector. Loop Aerial Details In the illustration is shown the connection details of a loop aerial. This loop consists of 10 turns of wire, stranded preferred, wound in the form of a singlelayer inductance, on a framework 2 feet square. The turns should be spaced % inch apart. The two outer ends are connected to the two lower terminals, as shown in the diagram. This shunts the .0005-mfd. variable condenser in the input circuit across the loop for tuning. The tapped switch is connected to the top or grid terminal of the circuit. This tapped connection is made at every second turn and permits a variation of the actual energy thrown on the grid. This variation of energy thrown on the grid is of decided importance in improving the efficiency of reception. Outdoor Antenna For cases where the use of outside aerials are desired, the usual method of connecting the tapped secondary of an air core neutrodyne transformer is recommended. This method is shown in the illustration. It is a decided improvement over an aperiodic primary and also avoids the addition of another control if a variocoupler were used. Condenser Efficiency The problem of condenser efficiency is of prime importance. All condensers should The Prices Quoted Below Deliver Goods to Your Door HOW TO ORDER — Write your order plainly; state number, description and price of items wanted. Send Post Office or Express Money Order, persona! check or bank draft. REFERENCES: R. G. Dun, Bradstreet, or Corn Exchange Bank. Now York City. BAKELITE TUBE SOCKETS Moulded of brown bakelite; Binding Post Connections. D99 Standard Type for 201 A, 301A, W.D.12 39c DIM For TJ.V.199, U.V.299, Socket 39c r W.D.ll, C.ll. .39c RADIO SOLDERING IRON Indispensable for the man who builds his own sets. D109 $2.50 D133— Soldering Paste, tube 25 COCKADAY COMPLETE Consisting of 1 Cockaday coll and 7 1 Bheostat pigtail connections 1 Switch Lever 2 .0005 Variable Con 1 Base Board densers 12 Ft. Bus Bar 1 Socket , 7 Switch Points 1 Panel 7x12 7 Marked Binding Poets 2 Dials. 3 in. 1 Jack 1 GMd Leak and Condenser Wiring Diagram and Instructions D-178 — Our Price $9.95 MISCELLANEOUS DI63 Spaghetti Tubing, per yd $0.09 D 164 Synthetic Crystal 30 D 165 Ground Clamps 17 DI66 Black Bubber Binding Posts 05 DI67 Nickel Plated Binding Posts, 2 for 05 DI68 No. 18 Annunciator Wire, half pound coil. .39 D 169 6 ft. Phone Cord with Tips 79 DI70 20 ft. Extension Cord with Tips 1.95 DI7I Wall Insulators, Porcelain 05 DI72 Tubular Porcelain Lead-in Insulators, 6-in. .10 DI73 Reinartz Coil 1.45 D 174 Cockaday Coil 2.42 DI75 2 in. Dial and Knob 25 DI76 3 in. Dial and Knob • 35 DI77 4 in. Dial and Knob 49 FILAMENT CONTROL RHEOSTATS Highest grade of material used, tapered knob. D104— 6 ohm $0.39 D105— 30 ohm 49 D106— 300 ohm Potentiometer. .79 D107— 400 ohm Potentiometer. .79 AMPLITONE LOUD SPEAKERS This speaker will give efficient results when used with any pair of Head Phones; highly nickel plated; 18 inches high. D117 $3-95 WOOD CABINETS Highest grade Mahogany finish Cabinets. Hinged top. These cabinets are being sold at less than one-half — ~. regular value. DS7 Wood Cabinet; panel size 7"xl0". Ea.$2.50 D58 Wood Cabinet; panel size 7"xl2". D59 Wood Cabinet; panel size 7"xl4". D60 Wood Cabinet; panel size 7"xl8". D61 Wood Cabinet; panel size 7"x21". D62 Wood Cabinet; panel size 7"x24" Baseboards (Mahogany Stained) for use with above cabinets 7x10 25c 7x14 35c 7x21 45c 7x12 30c 7x18.; 40c 7x24 50c 2.75 3.00 3.50 3.75 4.00 PLATE CIRCUIT "B" BATTERIES The highest grade of battery made at prices lower than they ever were sold before. D80— 22'/2 Volt Small $1.15 D81— 22yi Volt Medium. 1.45 D82— 22J4 Volt Large.... 1.95 D83— 45 Volt Medium 1.95 D84— 45 Volt Large 2.50 D85— 45 Volt Extra Large 3.50 D86— 360 Hour V/2 Volt Twin Double Duty "A" Battery 75 71 Cortlandt Street NEW YORK, N. Y. America's Greatest Radio Mail Order House ELEVEN NEW YORK STORES be of the highest quality obtainable, with low 1> and also low re ance value Naturally the minimum capacity should be aa low in value as Blble. T of this type are shown in the illustration. These are by no me; available; a nuin laced on the market. The two illustrated, however, show to best advantage the of construction which is characterise high efficiency Seven-Tube Circuit The large illustration shows a se tube sup' lit using two 9 of tK lo frequi (Continued on page 26) RECHARGE YOUR OWN BATTERIES Save Your Batteries, Time and Money OHIO Motor Generator CHARGER A REAL Motor Generator Set Designed and perfected to fill the need for an outfit that will give positive, dependable, lifetime service. It will quickly recharge any three-cell automobile or Radio "A" battery, even when completely exhausted or badly sulphated. Operates quietly, recharges in one-third time usually required and cannot charge in wrong direction, no matter how connected. SPECIFICATIONS Capacity, 6-10 volts, 3-20 amperes; automatic; needs no watching while charging. Cannot be injured by accidently short-circuiting generator leads. Ball bearing Ohio Motor and Generator will run quietly and smoothly thousands of hours without further oiling. Equipped with ammeter and rheostat to con trol charging rate. Long leads permit plugging in practically anywhere. Made of best materials; well finished; mounted on substantial base; weighs 60 pounds. Regularly equipped with 110 v., 60 cycle A. C. Motor; 6-10 volt Generator. Equipped for other service if desired; prices on application. WRITE Ask us why a good motor generator set is the only For Full real way to charge and keep your batteries in condi PARTICULARS tion and how it will save you money, time and trouble. Made by one of the leading electric motor manufacturers of the country. The Ohio Electric & Controller Company 5910 Maurice Ave. CLEVELAND, O. 2-LO, LONDON, ENGLAND ON ONE TUBE Another Record for the ELGIN SUPER-REINARTZ Tuesday, November 27, during the test period between 9 and 9:30 P. M., Rev. E. A. Cole in the residence of J. A. Mclver, of Roodhouse, 111., while operating a set made of materials and in accordance with the hookup furnished by the ELGIN RADIO SUPPLY CO., tuned in 2-LO, London, England, using receivers and but one tube. Later another tube was lighted and the loud speaker used, so that four people could hear the program and concluding announcement. The numbers, time, and the order in which they were played were Officially Confirmed by the St. Louis Post Dispatch in conjunction with the National Association of Broadcasters, who had charge of the tests. (See page 34, St. Louis Post Dispatch, Dec. 2, 1923.) This same hookup has been advertised extensively as the one which brings in stations 2000 miles overland on a loud speaker and one tube; and this has been demonstrated so often as to need no repetition. Send a two-cent stamp for circular giving one, two, and three tube hookup, and price list of parts for this remarkable circuit. Address the ELGIN RADIO SUPPLY CO. 207 Chicago St. ELGIN, ILL.