Radio Broadcast (May 1929-Apr 1930)

pull amplification, and an inductor loud speaker. The Model 32 lists at $169.00 and is similar to the 22 except for the loud speaker which is of the moving-coil type. The new StewartWarner Series 900 Consolette, consisting of a table-type receiver and a Stewart-Warner Dyphonic loud speaker, lists at $113. With an electrodynamic loud speaker the combination sells for $123.25. The set utilizes seven tubes plus a rectifier. In the output stage two 245-type tubes are connected in pushpull. The American Bosch Magneto Corporation has announced their new Bosch radio-phonograph combination, Model 30. The new combination uses nine tubes and lists for $475.00. The cabinet is 47| inches high, 36 inches wide, and 9\ inches deep and contains two record racks. The turn table is operated by a General Electric induction motor equipped with an automatic stop. Contained in the cabinet is a Bosch super-dynamic loud speaker. The Simplex Radio Company announces a new eight-tube receiver. The set uses five 227-, two 245-, and one 280-type tubes. The illuminated dial is calibrated in kilocycles. The set contains a phonograph jack and a built-in light-socket antenna. The console model complete with dynamic loud speaker lists at $150.50 less tubes. Miscellaneous New Apparatus The Stevens Manufacturing Corporation announces the design of a new diaphragm utilizing a special shape which is said to decrease distortion produced by ordinary cone diaphragms. The new diaphragm is made of Burtex, which is a special diaphragm material manufactured by this corporation. The Pooley Company, cabinet manufacturers, have designed two special cabinets, models 8200 and 8400, for use with the Atwater Kent Model 46 receiver and the Atwater Kent electrodynamic loud speaker, Model f-2-c. The Thordarson Manufacturing Company manufactures a special transformer, type T-2903, designed for use in conjunction with the moving-coil loud speakers to replace transformers supplied with these units. The Clarostat Manufacturing Company, Inc. manufactures a complete line of wire-wound resistors. Fixed resistors are available in sizes from 1 to 3000 ohms. Center-tapped resistors designed for use across the filament circuits of a.c. tubes are available in either fixed or adjustable types in sizes from 6 to 500 ohms. The Potter Company manufactures a dynamic loud speaker filter, a device designed for use with a.ctype loud speakers to decrease the hum. The filter is connected directly across the field winding. The price is $4.75. The Jensen Radio Manufacturing Company announces a new Imperial model loud speaker, consisting of a Jensen auditorium-type dynamic loud speaker mounted in a special cabinet which acts as a baffle. The cabinet was designed by Everett Worthington. Models for operation on either 110 volts a.c. or d.c. can be obtained. The a.c. Imperial model lists at $100. Louise Homer, Metropolitan Opera Star, listening to the new Victor Radio with Electrola, Model R. E. 45. The Jewell Electrical Instrumep^ Company's new a.c. tube-checker, type 210, operates from the a.c. lines and will check all types of tubes including rectifiers. The panel of the tester carries an a.c. voltmeter, a d.c. milliammeter, and a selector switch to give a.c. potentials of 1.1, 1.5, 2.5, 3.5, and 7.5 volts. Insulated test handles useful to servicemen or in radio laboratories are manufactured by the Metropolitan Mfg. and Electric Company, Chicago. The test handles complete with leads list for $1.25. A new phonograph pick-up has been announced recently by the Best Manufacturing Company. The Best theatre pick-up is counterbalanced so that just enough weight bears on the record for the needle to track perfectly. It is packed in a three-color display box with volume control and a universal adaptor for use with sets not having a phonograph jack. Price, $17.50. The Hoyt Radio Servicer, Model 600, is a compact portable set-tester for making tests on all modern radio receivers. It contains a high-resistance voltmeter for measuring d.c. potentials with voltage scales of 12, 120, and 600 volts. The milliammeter in the instrument has two scales, New Atwater Kent radio cabinet by Pooley. one of 30 and the other of 120 milliamperes. The a.c. voltmeter has three scales, 3, 9, and 150 volts. Provision is made for testing all types of tubes, including rectifiers. A new dynamic loud speaker, Model sp-29, is announced by the Stevens Manufacturing Corporation. To supply field current, a 280-type rectifier tube is used in conjunction with a filter system consisting of 5-mfd. condensers and a 30henry choke coil. The input transformer is arranged so that the loud speaker may be used with all types of power tubes, either singly or in push-pull. Items of Interest The Amrad Corporation manufactures Mershon condensers which are at present being used in the power units of a considerable number of wellknown receivers. Mershon condensers consist of rolled aluminum electrodes in a copper case, these electrodes being covered by an oxide film. These condensers' have the advantages that they provide a large capacity in a small space and they are also self-healing; that is, if they break down due to the application of excessive voltage, they immediately reheal and are not affected permanently by the break down. Mershon condensers are now being used by the following manufacturers: Automatic Radio Mfg. Co., Boston, Mass. Balkeit Radio Co., North Chicago, III. Browning-Drake Co., 110 Brookline St., Cambridge Mass. Colonial Radio Corp., Long Island City, N. Y. Crescent Radio Mfg. Co., Minneapolis, Minn. Crosley Radio Corp., Cincinnati, Ohio DeForest Radio Corp., Toronto, Canada France Mfg. Co., Cleveland, Ohio High Frequency Laboratories, Chicago, 111. Howard Radio Co., South Haven, Mich. Jordan Elec. Mfg. Co., Minneapolis, Minn. National Company. Maiden, Mass. H. J. Power Radio Corp., Medford, Mass. Sleeper Radio & Mfg. Co., Long Island City, N. Y. Sparks-Withington Co., Jackson, Mich. Sterling Mfg. Co., Cleveland, Ohio A. C. Dayton, Dayton, Ohio Luminator, Inc., 1730 South Michigan Ave., Chicago, has issued an interesting catalog describing a portable standing lamp made by them which provides strong indirect illumination for rooms. Irving Davis, of their sales department says many radio dealers are handling this item, selling the product as a sideline. It was announced by Atwater Kent that representatives of 22 radio cabinet makers have arranged to supply a complete fine of cabinets for Atwater Kent sets and loud speakers this year, giving a range of more than 30 different types from the popular priced models to the most elaborate. These cabinet makers expect to furnish their product for more than one million A-K sets during the year, i.e., from May, 1929, to May, 1930. The Charles Freshman Company, Inc., has applied for two television broadcast channels for experimental purposes. The transmitters will be located at the company's new plant at Clifton, New Jersey. The Engineering Division of R. M. A. recommends that, for the convenience of the buyer, the tubes in a receiver be designated to indicate which are strictly" radio" tubes and which are accessory to the performance of the set. Thus, the tubes in an average a.c. set would be indicated 6-1. The first six tubes indicate the measure of performance of the set and the number separated by a dash shows how many rectifier tubes and those used similarly are JUNE • 1929 •