Radio Broadcast (May 1928-Apr 1929)

RADIO BROADCAST Interior vieiv of the new Hollister a. c. -operated super-heterodyne Licensees of Ihe Technidyne Corporation n^HE Technidyne Corporation, 644 BroadA way, New York, headed by Lester Jones, has informed Radio Broadcast of the following licensees under their patents: RECEIVER CIRCUITS Continental Radio Corporation, Fort Wayne, Ind., makers of Slagle Receivers. Sets made by this company embody the so-called "feed-forward" Technidyne circuit. Sparks-Withington Company, Jackson, Michigan, makers of the Sparton Receiver. Sets made by this company employ the Jones "Equase" circuit. The A-C Dayton Company, Dayton, Ohio. A new Technidyne licensee who plan to market a set with the "Equase" circuit during 1929. OTHER LICENSEES Electrad, Inc., New York, manufacturers of the "Royalty" variable resistor under Technidyne patents. A new type of variable resistor developed by the Technidyne Corp. will be marketed by Electrad also. Electro-Motive Engineering Corp., New York, makers of Elmenco fixed resistors. De Jur-Amsco Corporation, New York, makers of fixed resistors under Jones patents. The Hollister AC8 Super-Heterodyne Kit Receiver IN CIRCUIT and general layout the Lincoln Radio Corporation's new kit, the Hollister ac8, is similar to the former Lincoln 8-80 except that the new kit is designed for complete a.c. operation, the original 8-80 being a d.c.-operated set. The Lincoln Corporation advises us that they have obtained excellent results from this set, finding it possible from their location in Chicago to tune-in a station at practically every degree on the dial. A description of the new ac8 has been received from the Lincoln Corporation and the essential details of the circuit are given below. The receiver is tuned by variable condensers independently operated by two illuminated drum dials. All wiring is done beneath subbase, which is composed of bak elite, eliminating possible shorts, and creating good insulation for all component parts. Substantial double-contact sockets are assembled in bakelite base ready for wiring. The tubes employed are as follows: oscillator, 227-type; first detector, a.c. screen-grid tube, 222 a.c.-type; three intermediate stages, a.c. screen-grid tubes, 222 a.c.-type; second detector, 227-type; first audio, 227-type; second audio, 210 or 250-type. The type-101 tunable intermediate transformers are used in the a.f. stages. Heavy copper shells house the transformer windings The new Conamic loud speaker manufactured by the Operadio Manufacturing Co. and variable condenser. The Clough system is used in the audio amplifier. An output transformer — Lincoln No. 107 — ■ may be mounted at right-hand side of base when the set is used with a loud speaker that is not equipped with an output transformer. The output transformer is not included in the standard kit, as the majority of dynamic loud speakers already have an output transformer incorporated in them. The power equipment for the Hollister ac8 is in a very compact crystalline-finished case and it supplies 45 volts, 135 volts, and 450 volts B; 7 J volts a.c, and 2j volts a.c. One 281-type tube is used as rectifier. The operation of the set is simple. The two dials track evenly throughout the broadcast range. A single volume control, composed of a 3000-ohm potentiometer controlling the 45 volts applied to the screen-grid tubes, is the only other adjustment necessary for tuning. List of Paris One No. 102ac oscillator; One No. 103\c antenna; Four No. 101 i f. transformers; One No. 105 a.f. transformer; One No. 106 a.f. transformer; Two .00035-mfd. condenser. Precise; One Sub-base and socket assembly, completely drilled Two Sub-base supports; Two Illuminated drum dials and windows; One Front Lithographed panel; Two Rinding posts; Seven 1-mfd. condensers; One tp-3-m 3000-ohm potentiometer, Carter; Four 3000-Ohm resistors, Electrad; One 2000-Ohm resistors, Electrad; One 1500-Ohm resistor, Yaxley; Two cu60 center-tapped resistors, Carter; One S-M No. 275 choke; One .00015-mfd. condenser with clips, Aerovox; One 2-Megohm grid leak. Aerovox; One Sangamo .00007-mfd. condenser; One .002-mfd. by-pass condenser, Aerovox; One Carter 110-volt a.c. switch; Two Tip Jacks; One Terminal strip, Jones; One Rattery cable, Jones; Two Knobs for potentiometer and switch; One Set hardware and wire; One Set of blueprints; One Small panel for console (optional). The kit of parts for the Hollister ac8 list at $110. The power unit for the set lists at $60. The S-M Screen-Grid A.C. Kit Receiver THE S-M model 720ac Screen-Grid Six is the newest kit being manufactured by the Silver-Marshall Company. H. B. Bandall of this company has supplied us with the following details regarding this new receiver. The model 720 ac is a six-tube a.c.-operated screen-grid receiver, available either as a kit for home assembly or as a custombuilt set. It employs three r.f. stages, each using one of the new 224-type a.c. screengrid tubes, a 227-type detector tube, and two stages of Clough-system a.f. amplification. In the second a.f. stage is found the new 245type power tube delivering over 1.6 watts of undistorted power output. Four tuned circuits, effectively shielded, and controlled by two tuning dials (the antenna-stage condenser is separate from the three-gang condenser tuning the second, third, and detector stages) enables all tubes to be operated at full efficiency and eliminates the loss (or, at best, small gain) attendant upon the usual untuned "dummy" r.f. stage used to permit singlecontrol operation. As both dials track very closely, the two dial feature is not a drawback to simple operation, while it is a very great AntennaM/ 1 mfd. 0.00015 mfd. 2-megohm Grid Leak * 1st. Detector Oscillator 227 Ant.Coll C No.ltar Ml lstlnter.Freq 3rd.lnter.Freq. 4th.lnter.Freq. Trans. No.101 Trans. No.101^ 2nd Inter.Freq. ', 3rd.lnter.Freq. \ lst.Audio Freq. Amp.227 2nd.A.F.Amp. 210or250 Ground Schematic diagram of the Hollister a.c. -operated super-heterodyne _j april, 1929 page 408