Design of CW amplitrons for space-borne telemetry applications

The requirements for space-borne telemetry transmitters place a premium on high efficiency, small size and low weight. The CW Amplitron, a continuous-cathode, crossed-field, backward-wave amplifier, has many characteristics in addition to high efficiency that suggest its use in space telemetry. The paper describes these characteristics with respect to the intended application. Design considerations of the QKS997 Amplitron, a 25-watt CW S-band amplifier with 20 db gain and greater than 50% efficiency are presented and performance data of tubes built to date are reviewed. A unique rf circuit design is employed which permits near minimum magnet weight and convenient conduction cooling. Low residual phase modulation, insensitivity to environmental conditions, low transmission loss in the off condition, weight close to 1 pound, and cathode loading compatible with long life are other features of the design. Preliminary designs of Amplitrons for other telemetry bands from S- to V-band are also discussed with respect to power level and systems needs at these frequencies.