Radio Broadcast (May 1929-Apr 1930)

another contribution to the tube's part in better radio reception. It is fitting that the Raytheon Company which has rendered so much engineering service to the radio industry, should be the first to take a license from the Radio Corporation, which will insure a close cooperation between the laboratories and should result in benefit to the radio industry in general." It is understood that licenses under RCA. tube patents may be granted to other tube manufacturers. As extensive a family of licensed tube manufacturers may grow up as a result of this new RCA policy as has developed in the set field where there are now more than 31 companies producing receivers under RCA licenses. The first RCA set license was granted to Zenith on March 10, 1927. It is interesting to note that the first tube license was granted in the same month, just two years later. The 1929 Vidoreen Kit Receiver One of the Most Popular of the superheterodyne kits is the Victoreen 1929 A.C. receiver. We have received from the Baseboard view of the New Victoreen kit receiver. The neiv tube manufacturing plant of the La Salle Radio Corporation, Chicago, III. George W. Walker Company a description of this a.c. receiver and the following paragraphs describe its major characteristics. In designing the 1929 circuit, it was con sidered advisable to redesign the intermediatefrequency transformers and peak them slightly below former types. Each i.f. unit contains a variable condenser which is tuned to a standard frequency and then sealed at the factory. By this method any four transformers may be used together without the necessity of matching them in sets. With the new r.f. transformers there has also been designed a special oscillator. The oscillator and antenna circuit tune together throughout the broadcast range, although the circuits naturally operate at different frequencies. Very little compensation is, therefore, required. For tuning this receiver a single dial control using two 0.0005-mfd. Render condensers are used. This single dial control unit has no backlash and requires a 360° back-panelilluminated dial. Vernier capacity adjustments are provided for by a small 0.0001-mfd. variable condenser. 227 172 227 172 227 172 227 112 I To Input of 227 1 12 1 ?ower Amplifier To Heaters of T ubes 9,10,11,12 To Heaters 'of Tubes 13,14,15 To 112-A 4 4 4 5 Voitsr^andP"ot? iii iMMJU Plate rectification is used in the 1929 Victoreen AC receiver and in a measure this is responsible for the fidelity obtained. Both the second detector and first a.f. tubes operate with the same grid bias. A plate potential of 90 volts is used on the detector and the first a. f. tube operates from 180 volts. The new Victoreen 327-type filament transformer has been designed to supply the standard a.c. tubes with power at slightly below their rated voltage. As now designed, it is standard only for 50 to 60-cycle current from a standard 108 to 11 2volt line. This transformer comes equipped with the leads all attached to facilitate the wiring. It is designed to supply up to five 227-type tubes from each 2|-volt secondary and two 112A-type tubes from the 5-volt secondary. This circuit uses the 227-type tubes through out the receiver. They reduce the hum to an imperceptible value and also ehminate variation in volume caused by voltage fluctuations. The volume control in the 1929 a.c. circuit consists of a resistor in the common plate re. turn of the i.f. stages. This variable resistor's function is not only to decrease the plate potential but also to provide a high negative bias. This volume control does not change the tuning due to change in the voltage relation in the different circuits and, therefore, readjustment of the dials when the volume is changed is not necessary. The circuit is adaptated for use with a phonograph pick-up unit which is placed in series with the grid return of the second detector. This receiver is also adaptable both for loop or outside antenna. If an antenna is used it is only necessary to remove the loop leads and connect the antenna coupler secondary to the loop posts. In using an antenna, fifty feet including lead-in should be more than ample. The Victoreen power supply is a most important essential with the 1929 Victoreen a.c. circuit as it provides the 90 and 180 volt circuits with voltage regulator tubes. The construction of this receiver is a very simple matter and free blueprints are available giving complete details. These include a point-to-point wiring description and a fullsize template which may be used for laying out the parts. The complete kit of parts for the 1929 Victoreen kit is available from the George W. Walker Co., Cleveland. Price: $141.30. A CORRECTION Schematic of the Victoreen 1929 A. C. Super-Heterodyne. IN the List of Books which was included in Mr. Dunham's article, "What the Serviceman Shoidd Study." March, 1929, Radio Broadcast, page 295, two errors in price occurred. The correct price of H. F. Van Der Bijl's Thermionic Vacuum Tube is $5.00, and Practical Radio Construction and Repairing, by Moyer and Wostrel, lists at $2.50. Both books are published by the McGraw-Hill Book Co., Inc., New York City. • may, 1929 pupc 48 •