Abstract: A method and apparatus for determining the frequency of an input signal. The input signal and a sampling signal having a sampling frequency f.sub.s to a sampling mixer to produce a first intermediate frequency signal. The first intermediate frequency signal is applied to a detector having a response frequency bandwidth of at least f.sub.s /2 to determine whether the frequency value of the input exceeds a threshold value. The frequency value of the sampling signal is changed from among a plurality of frequency values and applied to the mixer until one of such frequency values results in a second intermediate frequency signal in a predetermined frequency range which is smaller than and lying within the detector bandwidth. The second intermediate frequency signal is applied to a frequency counter which produces a count corresponding to the second intermediate frequency.