A receiver for isolating a wanted signal in a received signal, the receiver comprising a downconverter for downconverting the received signal in frequency to produce a downconverted signal, a filter with a passband intended for isolating that part of the spectrum of the downconverted signal that contains the wanted signal and a controller that seeks to avoid or reduce the effect of passband intrusion in the form of a negative frequency representation of an interferer, appearing in the spectrum of the received signal, upconverted in frequency to the passband. The invention consists in corresponding methods also.