Radio Broadcast (May 1929-Apr 1930)

RADIO BROADCAST employed. By totalling the two figures the entire number of tubes employed is apparent. The General Electric Company has sold to the Russian government the world's largest high-voltage rectifier. This giant rectifier is of the mercury-vapor type and supplies an output of 758 kilowatts at 15,000 volts. Eighteen mercury-vapor rectifier tubes are used. The sale was negotiated under a contract calling for several items of radio apparatus including a 20-kilowatt short-wave transmitter. Dudley Wilcox, teasurer of the Ajax Electrothermic Corp., Trenton, N. J., advises us that he has available for presentation before engineers' clubs or societies copies of a film dealing with highfrequency electric furnaces. The film shows the melting and pouring of metals in charges of from one ounce to several pounds, clearly indicating the method of operation and the way in which electricity is applied in the furnace charge. Effective April 1, the Radio Corporation announces, loud speaker No. 103 is reduced in price to $30 and No. 106 to $65. This is a reduction of $7.50 and $23.00, respectively. Of Enginering Interest The E. F. Johnson Company, of Waseca, Minnesota, sells a complete line of microphones and accessories, transmitting tubes, inductances, insulators, and filter condensers. The microphone is of the stretched-diaphragm, two-button, carbon type and lists at $67.50. The Silver-Marshall Company's public-address amplifier, type 690, is designed to supply sufficient power, when fed by a microphone, a radio set, or phonograph pick-up, to operate up to twelve dynamic loud speakers, according to the manufacturer. The amplifier employs three a.f. stages. The first audio arnolifier tube is a type 227, in the second stage ?26type tubes are used in push-pull, and in the output stage are two 250-type tubes in push-pull. The amplifier is stated to have a comparatively flat characteristic from 50 to 5000 cycles. Price, completely wired, $245.00. A calibrated level indicator panel has been designed by J. E. Jenkins and S. E. Adair. The net price, complete except for tubes and batteries, is $250.00 f.o.b. Chicago. The panel gives a wide Joseph L. Ray, vice president and general sales manager, R. C. A. range of level readings from — 10 db to +20 db in steps 2 db deep. The panel is exceedingly useful in determining the output of an amplifier or in making a frequency characteristic run. The input transformer in the device has a flat characteristic up to 6000 cycles. It has the advantage over other level indicating systems that it is direct reading and that it produces practically no change in load when its own settings are altered. DATA ON INTERFERENCE PREVENTION Circular letter No. 182 issued by the Bureau of Standards, Department of Commerce, Washington, deals with elimination of certain types of interference with radio reception which have been found serious in some areas. Some subjects covered are power line induction, sparking apparatus, location of interference sources, commutators, bell ringers, and smoke precipitators. new stromberg-carlson set The Stromberg-Carlson Company's ner; receiver, No. 641, contains several improvements in design that result in better detection and audio reproduction. Three stages of r.f. amplification using the new a.c. screen-grid tubes are used. From these tubes tremendous amplification is obtained and there is impressed on the input to the power detector an r.f. voltage at least thirty times greater than would be obtained from an r.f. amplifier using three 227-type tubes. The power detector has a linear characteristic which eliminates distortion obtained from ordinary "square-law" detectors. The output of the detector feeds into a 245-type power tube. The use of only one a.f. stage not only improves the quality by eliminating some possible distortion in the audio amplifier but also results in less a.c. hum. The receiver is single controlled and is equipped with a phonograph pick-up jack. BRUNSWICK BUYS BREMER-TULLY The Bremer-Tully Company, of Chicago, has been purchased by the Brunswick-Balke-Collender Company. This brings to Brunswick licenses to use patents controlled by BCA, Meissner, Hazeltine, and Latour. The new line of Brunswick radio sets and Brunswick radiopanatropes will "establish price levels to insure Brunswick dealers a mass market opportunity so essential to successful merchandising," it was announced. HILER AUDIO SYSTEM LICENSEES The Zenith Radio Corporation, of Chicago, is the only receiver manufacturer licensed to use the Ililer audio system. Parts and accessory manufacturers who are now licensed are: General Radio Company, Ford Radio and Mica Corporation, American Specialty Company, Leslie F. Muter Company, and Kenneth Harkness, Inc. \ V III Mill 1 mm * *«*• 1. i .-»-.. * ■ , V / .■■"?* ' /*" J The winner in the Ludlow Radio Company' s "Oldest Set Contest." price of ux-245 reduced Effective April 15, the price of the new power-amplifier Radiotron, the ux245, was reduced from $4.25 to $3.50, the Radio Corporation announced. "Although this tube was announced during the early part of March," officials of the Radio Corporation state,' "it has already created a demand in excess of preliminary production estimates. The resultant increase in the production schedule has effected a corresponding reduction in cost of manufacture, making the new price possible." A WISCONSIN DEALER'S NOVEL CONTEST An interesting contest was held recently in Madison, Wis., by the Ludlow Radio Company. M. H. Ludlow, president, called for the registry of the oldest set in town. The first prize was a complete a.c. receiver. "The prize-winning set will be kept as a curiosity," said Mr. Ludlow, "and through the contest we gained a number of prospects for new sets." Some of the oldtimer sets which were registered in the contest were Radiola 3, Clapp-Eastham C23, Grebe CR-9, deForest, Custer Airbug, and A.. C. Gilbert. Radio Broadcast was asked to act as adviser in deciding the contest. We should be interested to hear from other dealers who have successfully carried out similar contests with details of the re • JUNE • 1 929 •