Factors Limiting UHF Telemetry Systems Operation

Abstract

Demands on the use of that portion of the radio spectrum from 225 MHz to 400 MHz for military tactical operations have made it necessary to vacate the VHF telemetry band from 215 MHz to 260 MHz by I January 1970 and to convert such operations to UHF telemetry bands from 1435 MHz to 1540 MHz and 2200 MHz to 2300 MHz. The environmental, physical, and practical limitations imposed on telemetry system performance when operation is moved from VHF to UHF are described in this paper. The topics which are discussed include path loss, multipath, flame plasma effects, expected Doppler shift and Doppler rates, natural noise limitation, UHF transmitter power and stability, receiving system noise figures, airborne antennas and ground antennas. UHF telemetry operation in support of missions for aircraft, ballistic, orbital, and deep-space vehicles is evaluated mainly through a comparison with similar operations at VHF. The results of this study show that there are no technological factors which limit the instrumentation of an adequate UHF conversion.