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Show AFT.- I ("I - v I 1 rX rv,, 1 1 r M ,, -JL o o o cHP - 590V. B45V. A- AB- Three-Tube Receiver Unexcelled for Distance, Volume and Tone. Square Wound Toroidal Coils Give the Circuit Selectivity. Regeneration Is one of the most wonderful things of radio, without which the entire broadcasting situation situa-tion would not have reached its pres- , ent day perfection. But, the regenerative regenera-tive receiver, as such, has almost become be-come extinct because of its radiating qualities which spoil general reception recep-tion for miles around, and because It . is not selective enough to tune through a number of nearby broadcasting stations. sta-tions. Regeneration is a great help to any radio set. When used in a sharp tuning tun-ing receiver it will add sufficient volume to equal a nonregenerative set, using a greater number of tubes. The circuit shown here was devised by engineers of the Ail-American radio corporation to produce a three-tube set, 'employing regeneration and radio frequency ampliacation, combined. The radio frequency makes it a distance dis-tance getter and prevents radiation, and the regeneration produces the volume and sensitiveness required to operate satisfactorily under 1926 conditions. con-ditions. Make Sharper Tuning Set. Toroidal coils make this combination combina-tion possible, by eliminating Interstage coupling. The magnetic field of the transformers is confined in the coils. The toroid coils also prevent the pickup pick-up of local stations by the coils themselves them-selves and make a much sharper tuning tun-ing set. The new Ail-American shielded straight line frequency, condensers con-densers are recommended to prevent crowding of the stations on the lower waves. Only one stage of audio frequency Is provided, and if this be constructed with one of the laboratory model lyric transformers, reproduction of music and speech will be as clear and undistorted as on a one tube set. The regenerative feature Is controlled con-trolled by a small variable condenser of approximately .00015 mfd. that permits per-mits the tubes to be brought gradually gradual-ly up to the point of oscillation, or "hot spot." where reception Is best. The Parts Needed. Few parts are needed, and the set can be assembled with a 7 by 18 or 21-inch panel and cabinet, without crowding. Two controls, an ideal system of tuning a radio set, are used. To construct the receiver you will need the following list of parts: One toroid coupler, type Tl (LI). One toroid coil, type T2 (L2). One universal coupler, type R 140 (L3). Two straight line frequency condensers, con-densers, type C35 (CI and 2). One variable condenser, approximately approxi-mately .00015 mfd. capacity (C3). One audio transformer, type R12 (AFT 1). One large fixed condenser, 0.5 to 1.0 mfd. Three sockets. One grid leak. One .00025 mfd. grid condenser. One 6 ohm rheostat. Binding posts, wire, screws, etc. The UV109 or C299 type of tubes may be used if the rheostat is 10 to 15 ohms. One rheostat controls the three tubes and it is not advantageous to provide a separate rheostat for each tube. The 45-volt "B" battery binding post Is for the detector tube, which should not be of the regular UV200 or C300 type, unless the voltage Is lowered to 22 volts. |