Western Electric Model 6-B
The Model 6-B is a 1 kilowatt radio transmitter that was manufactured by Western Electric starting in 1928. It consists of an oscillator unit and an amplifier unit. The 6-B is capable of operating from 500-1,500 kHz with wavelengths from 200 to 600 meters. It can run on three-phase 50-60 Hz AC at 220 V or DC at 115 or 230 V.
Components
Oscillator unit
The No. D-87738 oscillator unit contains the crystal oscillator with its associated circuits, temperature control equipment, and two stages of radio frequency amplification.
The Model 6-B utilizes a piezoelectric crystal to control the master oscillator and associated equipment, specifically to maintain the desired frequency. The crystal is a small quartz plate cut with parallel faces to a thickness that matches the frequency of its mechanical vibration.[jargon] The crystal is held at a strictly constant temperature which is required to maintain the same frequency. Model 6-Bs have two crystals; one intended for regular use and one spare.
Amplifier unit
The No. D-87739 amplifier unit contains the audio frequency valve amplifiers, radio frequency power amplifiers with their associated circuits, the antenna coupling, and tuning circuits.
The audio input is amplified in this unit by one amplifier and then used to modulate the second amplifier in the oscillator unit by the second amplifier in the amplifier unit. This second amplifier utilizes Heising modulation,[1] an inefficient but common method of modulation at the time.
Power
Power to the Model 6-B is supplied by two large motor-generator sets. One set features twin 2,000 VDC generators to provide 2,000 and 4,000 VDC to the vacuum tube circuits (the voltage each tube used would differ). The other set provides 25 VDC for the vacuum tube heater filaments and 250 VDC for the vacuum tube bias supply and the excitation voltage for the 2,000 VDC generators.
Microphones
Radio announcers using this transmitter would have used Western Electric double-button carbon microphones.
- ↑ Western Electric Company (1930). No. 6-B Radio Transmitter Instructions for Use.