System for measuring satellite downlink amplifier linearity includes a pulsed signal generator for selectively generating low duty cycle pulses. A linear transmitter uplink amplifier is provided for amplifying the low duty cycle pulses and generating an uplink signal. An antenna transmits the amplified uplink signal to an orbiting satellite. A downlink amplifier in the satellite generates a downlink signal for re-transmission to an Earth-based antenna. A pulse receiver is provided for receiving the downlink signal and providing information regarding the transfer function of the downlink amplifier. Preferably, a delayed trigger circuit is coupled to the pulse signal generator for activating the pulsed signal generator after a time delay substantially corresponding to the propagation times of the uplink and downlink signals. By altering the duty cycles of the uplink signals while maintaining the peak power level the average powers transmitted to the downlink amplifiers can be changed to modify the power levels of the downlink signals to provide more complete information regarding the transfer functions of the downlink amplifiers.