TH-3 Microwave Radio System: The Traveling-Wave Tube Amplifier

Traveling-wave tubes are used as the transmitting amplifiers for the T H - 3 radio system. The 464A traveling-wave tube, manufactured by the Western Electric Company for this application, is designed to provide a power output of 11 watts with 33.5 dB of gain in the linear region. As is usual for such devices, the tube is operated at 2 to 3 dB below the maximum power output capability of 20 watts in order to keep intermodulation effects low. Also, it has been designed as a completely packaged device to reduce the number of tests and adjustments that are required at the installation site. The package is designed so that the magnet structure can be reclaimed at the end of the tube life for subsequent reuse. The amplifier, shown in Fig. 1, measures 0.48 X 0.11 X 0.11 meter * Cathodes made from zirconium-additive nickel were used in the Telestar® traveling-wave tube; see Ref. 1. 2223 2224 T H E BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1971 INCH 0 1 Fig. 1--The 464A traveling-wave tube power amplifier.