10KW L-Band Amplifier Tubes for Efficient and Reliable Troposcatter Communication Transmitter Systems

The purpose of this program was to develop two advanced development model high power amplifier tubes specifically for troposcatter communication application. Varian Associates was awarded a single contract to develop a klystron model tube and a klystrode model tube. Critical elements of the specification for the two tubes were (a) power output l0xw, (b) 10 MHz electronics bandwidth, (c) 750-980 MHz tuning range and (d) efficiency 50%. The challenge for the klystron design was to be able to maintain efficiency in excess of 50% over the full 10 MHz bandwidth. This was accomplished with an eight cavity design. The klystrode challenge required designing a new grid shape that integrates a converging electron beam with a cavity with a minimal magnetic field focusing. Results of the program were that basically most of the performance specifications were demonstrated. However, the klystron showed a sharp drop-off in power at 840 MHz due to a second harmonic cavity mode. The klystrode has considerably less gain than the existing klystron and thus additional RF drive is required.