Abstract: A primed oscillator for microwave amplification includes a single tank conductor (16) coupled to a coupling conductor (17) by an interdigitated coupler (26). The coupling conductor (17) is connected to the cathode of an IMPATT diode (22) which is triggered by the application of a back-biasing trigger pulse that biases it into its negative-resistance region. When a keying pulse is applied to the IMPATT diode (22), the diode couples power through the interdigitated coupler (26) to the tank circuit (16) to cause oscillations that are initially in phase with any incoming signals, but the frequency of the oscillations is determined by the configuration of the tank circuit (16), not by the frequency of the incoming signal. If the incoming signal is near enough to the resonant frequency, and if the duration of the keying pulses is short enough, the output of the primed oscillator appears to a band-limited receiver to be an amplified version of the input signal.