A slot-based low Intermediate Frequency (‘IF’) radio receiver comprises an IF local oscillator for producing I and Q IF local oscillator signal components in phase quadrature, I and Q mixer channels for mixing the input signal with the I and Q IF local oscillator signal components to produce I and Q IF signal components. The IF local oscillator includes frequency alternation means for causing the IF local oscillator frequency to alternate a plurality of times during each frame between first and second values, one of which is greater and the other smaller than the desired carrier frequency of the input signal so as to reduce the effect of adjacent and alternate interferers. The phase of the baseband local oscillator is alternated in synchronism with the alternation of the IF local oscillator frequency.