Apparatus for and method of measuring radio frequency signals

Apparatus for detecting and measuring the values of radio frequency (RF) signals comprises two intermediate frequency (IF) channels having mixers fed by local oscillators (LO) with output frequencies having a predetermined frequency difference. The LO frequencies are selected to produce IFs from overlapping or coincident RF bands which are higher and lower, respectively, than the LO frequencies. The outputs of the mixers are measured in identical frequency discriminators, respectively, and the outputs of the discriminators are compared by logic circuits which determine the presence of signals in either or both of the channels and the value of the corresponding RF signal. This receiver eliminates the need for an RF preselector for the superheterodyne process and thereby broadens the RF bandwidth receiving capability of the system.