Cross modulation is caused by non-linearity in the
RF amplifier or the mixer and results in the transfer
of the amplitude modulation of a strong, unwanted carrier onto
the wanted carrier. Cross-modulation and can be minimised by linear
operation of the RF stage and by increasing its selectivity
to reduce the number of signals entering the receiver. Normally,
cross-modulation problems are confined to the AM broadcast bands and
therefore do not create much of a problem in communication
receivers. Cross-modulation does not occur in an FM receiver, which
is unaffected by amplitude variations in the wanted signal.