Radio Broadcast (May 1928-Apr 1929)

New Apparatus An Inside Antenna X3o Device: Indoor Aerial. Consists of a seventyfoot spool of indoor aerial wire, a twenty-five foot length of rubber-covered ground wire, and a ground clamp. The aerial wire is made of stranded copper covered with a brown braid. Manufactured by the Belden Manufacturing Company. Price: $1.35. Application: Designed especially for indoor antennas, the wire is flexible and can be easily wired around a room, over window frames, and because of the neutral brown color of the braid, the wire is practically invisible. Fine New Drum Dial X31 Device: National Type F Velvet Vernier Drum Dial. Dial light is readily removable, and has both terminals insulated from the dial. Dial numbers are engraved on strip. Drum is made of brass, with nickel plating and the dial front is silver plated. The movement has NATIONAL DRUM DIAL absolutely no back-lash. Manufactured by The National Company. Price: $4.50. Application: May be used in constructing any receiver. One of the best drum dials that have been received in the laboratory. A Good Phonograph Pick-Up .x32 Device: Amplion Phonograph Pick-Up Unit. Device is complete with tone arm and volume control. Manufactured by the Amplion Company. Price: $15.00. Application: To be used in conjunction with a phonograph turn-table and an audio amplifier to make possible the electrical reproduction of phonograph records. The tone arm is screwed down on the turn-table bed of the phonograph in such a position that the unit on the end of the tone arm can be correctly placed on a record. The Laboratory's sample of this pick-up has given very satisfactory reproduction of records and it has the advantage over some other pickups that it exerts but slight pressure on the record resulting in less record wear. Resistor for the Screen-Grid Tube X33 Device: Amperite No. 622. Filament-control resistance for screen-grid tubes. When placed in series with the tube filament and a six-volt battery, this resistance will reduce the voltage to 3.3 volts, the correct voltage for a screen-grid tube. Manufactured by the Radiall Co. Price: $\.\o. Application: May be used for filament control of the screen-grid type tubes in a receiver. Amperites for each type of tube are made. Complete data on the different styles available may be obtained by writing the manufacturer through Radio Broadcast. Set Tester of Wide Use X34 Device: Radio Set Tester, A. C and D. C. Model 537. This set tester is designed for the testing of all kinds of radio receivers operated from either alternating or direct current light socket power or from batteries. It will measure the various voltages used in the radio set both at the tube sockets or at any part of the set; it will test continuity of circuits, and test the tubes under the same conditions as exists when in their sockets. All tests can be made by using the voltages normally supplied to the set by its batteries or socket power with no change in connections, so that no auxiliary power supply is required. Socket adapters are supplied so that uv, ux and uy type tubes may be tested. All of these tests are possible using the two meters contained in the instrument, which are an a. c. voltmeter having three ranges 150, 8, and 4 volts, and a d. c. volt-milliammeter which has four voltage ranges, (600, 300, 60, and 8 volts) and two current ranges, (150 and 30 milliamperes). The voltmeter has a resistance of 1000 AMPLION PHONOGRAPH PICK-UP ohms per volt and can therefore be used satisfactorily to measure the output voltages of B power units. Tests on tubes can also be made independent of any radio receiver by connecting a plug supplied with the instrument into a light socket. T) RODUCTS of radio manufacturers whether L new or old are always interesting to our readers. These pages, a feature of 'Radio Broadcast explain and illustrate products which have been selected for publication because of their special interest to our readers. This information is prepared by the Technical Staff and is in a form which we believe will be most useful. We have, wherever possible, suggested special uses for the device mentioned. It is of course not possible to include all the information about each device which is available. Each description bears a serial number and if you desire additional information direct from the manufacturer concerned, please address a letter to the Service Department, Radio Broadcast, Garden City, New York, referring to the serial numbers of the devices which interest you and we shall see that your request is promptly handled. — The Editor. 85 Manufactured by the Weston Electrical Instrument Corp. Price: $100. Application: An essential instrument for the radio dealer and the professional radio service man, for it makes possible the thorough, accurate and rapid testing of a receiver. For the 250 Type Tube X35 Device: Power Equipment for the 250 type tube. The apparatus listed below has been designed for the 250 type tube. This tube requires much more plate current than other types of power amplifier tubes and therefore the apparatus for use with it must be constructed to prevent overheating and saturation effects at high currents. Type 565-B Full-Wave Transformer. Designed for full-wave rectification using two type 281 tubes. The plate voltage winding is 1200 volts with a center tap. There are also two WESTON SET TESTER 7.5-volt secondaries for the filaments of the rectifier and power amplifier tubes. Price: $20.00. Type 565-A Half-Wave Transformer. This transformer is designed for half-wave rectification in conjunction with one 281 type tube. There are four secondaries: one of 600 volts for the plate voltage; two of 7.5 volts each for the filaments of a rectifier and power amplifier tubes; and one of 2.5 volts for the filaments of 226 and 227 type of tubes in case this transformer is incorporated in a complete two or three-stage amplifier. Rated at 200 watts. Price: $20.00. Type 587-A Speaker Filter. A speaker filter that thoroughly insulates the speaker from the high plate voltage and current of the last-stage tube. The choke used is of unusually heavy construction and has an inductance of approximately 15 henries and a continuous current rating of 100 milliamperes. The direct current resistance is 250 ohms. Two microfarad condensers are used on each side to completely insulate the speaker from high voltage. Connections to the input side are in the form of leads while the speaker is connected to two binding posts. Price: $10.00. Type 527-A Rectifier Filter. This unit consists of a combination of two heavy-duty chokes with an inductance of approximately 13 henries each and a continuous current rating of 100 milliamperes and a condenser assembly consisting of a 4-2-4-mfd. combination rated at 1000 volts d. c. The direct current resistance of each choke is 175 ohms. Price: $25.00. All the above apparatus Manufactured by the General Radio Company. Application: This apparatus may be used in