PURPOSE: To perform the measurement of the recovery time of a TR tube as packaged at any time by monitoring and judging changes in the gain control voltage with respect to the delay time when a false target is tracked by operating a gain control circuit with a signal processing section.

CONSTITUTION: A trigger signal A generated synchronizing a high frequency/high power signal generated from a transmitter 5 is received with a signal processing section 8, which controls a false target signal generation circuit 4 so as to generate a high frequency false target signal B of a fixed level delayed by a certain time therefrom. This signal B is inputted into a receiver 6 through a TR tube 3 recovered from a loop coupler 2 and an output signal C is controlled with a gain control circuit 7 to track the distance of a target through a tracking section 10. Therefore, control is performed with a processing section 8 to change the delay time maintaining the signal B at a fixed level and the delay time when the output signal D of the circuit 7 lowers by a fixed value from the initial value is outputted to a display section 9 thereby enabling the measurement of the recovery time of the TR tube 3.