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Show t.Edited by G. Dougias Wardrop, iTunor of Radio Mereiianuis;ng. NK Uni Control Receiver R Vf SI $$mi... In Addition to tho Apparatus Given Above, a Small Mica Condenser of .002 Microfarads Capacity Is Placed In the Filament-Ground Lead (C-2). Todny Is the day of the "new" circuits, cir-cuits, writes H. A. Duncan, In the New Tork Globe. New adaptations, novel variations of standard circuits, are being be-ing dally developed and published. Every effort Is being turned toward the Blmple, the easy. One of the Interesting developments In this recent period of "circuits" Is the one shown, which Is probably the original "single circuit-single control" hookup. It will be observed that there , is actually but one variable tuning element, and that is the variable con- denser shown at C-l. There are but two colls to wind, and . as there are no taps at all to take off, the winding Is of the simplest. The primary coil P consists of about 15 turns of No. 22 single or double cotton-covered cotton-covered wire, wound evenly in one layer on a three and a half inch tube. For the secondary winding, 28 turns of wire are used, and this winding Is placed on the same tube as the primary, pri-mary, but about one-quarter of an Inch away. Both windings should progress In the same direction. Tuning Device. As has been explained, there is hut one variable tuning device, the variable condenser C-l, which has a capacity of about .001 mfds., and which is con- nected directly across the winding S. The rest of the components of a regular reg-ular vacuum tube set, the vacuum tube, rheostat, dry cell or storage battery, bat-tery, the high voltage "B" battery, etc., are all shown In the diagram of connections. con-nections. It is Important that the "A" and "B" batteries be connected correctly. The diagram shows the exact polarity of these two units. If, after all of the component parts have been assembled as shown in the diagram, the set will not oscillate, reverse re-verse the connections to the secondary coil. To by-pass the radio frequency currents in the plate circuit, a small 'phone condenser across the 'phones will help, although it is not necessary. With single circuit tuners it is best to use short antennae for sharp tuning. tun-ing. That is to say(, the antenna used with the set should be comparatively compara-tively small, and not over 70 feet in total length. An antenna about 50 feet long will be found to work exceedingly ex-ceedingly well. In fact, the author has used this circuit with an antenna only 20 feet long, made of a wire dropped out of the window, and the tuning on local stations was incredibly sharp for this kind of a tuner. |