Intermodulation study. Intermodulation products: Satellite ground antennas

A description of tests, observations, problems and results of work performed to reduce the intermodulation products generated in the 5-horn feed of a 60-foot diameter parabolic antenna. The goal was to produce feed components that generated intermodulation products at levels below -140 dBm while subjected to 10 kW CW of total power in any combination of carriers. The receive band was 7.25 to 7.75 GHz; the transmit band was 7.9 to 8.4 GHZ. The study was conducted in three phases: The determination of intermodulation levels as a function of total power, proportional power between carrier, waveguide current densities, vacuum, and test configuration; Specific problems encountered in fabricating waveguide devices, specifically flanges, seams, materials, tuning methods, and the degeneration of these factors with time; An effort to obtain specific intermodulation-free components, particularly stable filters and flanges.