Abstract: A radar detecting system comprises an antenna for receiving radar signals, a sweep generator for producing a sweep signal over a predetermined range of frequencies and at a predetermined rate and a mixer for mixing the sweep signal with the received radar signal for producing intermediate frequency (IF) signals. A bandpass filter passes only those IF signals within a predetermined frequency band and a detector responds to the IF signals passed by the bandpass filter by producing corresponding output pulses. A control circuit is responsive to a pair of output pulses being produced for each of three successive cycles of the sweep signal and to both the first pulse and the second pulse of each pair of pulses occurring at the same time intervals respectively relative to the corresponding cycle of the sweep signal for producing a warning signal.