Monitoring of input backoff in time division multiple access communication satellites

A method of measuring input-backoff to an amplifier in a time-division multiple access (TDMA) communication system having a carrier recovery segment and a clock recovery segment prior to a data segment in a traffic burst. A monitoring station transmits a CW pilot signal within the amplifier's bandwidth. In the guard time between bursts, the monitoring station measures the unsuppressed pilot level output by the amplifier. While a ground station is transmitting an unmodulated carrier during carrier recovery or a carrier modulated at the clock frequency during clock recovery, the monitoring station measures the suppressed pilot level, suppressed by the non-linear interaction of pilot and carrier. The amount of pilot suppression is related to the input power back-off of the carrier by a previously measured or a theoretically derived relationship. The carrier-to-suppressed noise ratio is determined by measuring the carrier level during the carrier recovery and by measuring the suppressed noise during carrier or clock recovery through a noise filter centered away from any transmitted signals or their intermodulation products.