"Richard Clark"

Now, as to your experience of receiving signals on the wrong
frequency, that is a classic situation of image rejection being poor
due to the lack of a tuned front-end (something that dissappeared with
the dinosaurs). If I were to guess on the basis of 40 year old
experience fixing these suckers, your off-frequency signals are
probably shifted by twice the IF frequency of your receiver. The
classical FM IF frequency of 10.7 MHz might apply, but time has
marched on and designers may select their own. This old standard
would argue that you shouldn't experience images except where they
would be out-of-band (the 88-107 band with this IF would force that).


** Hearing the same FM station at more than one spot is still possible even
with a 10.7 MHz IF frequency - if the signal is very strong. The reason
is harmonics of the incoming carrier generated in the RF stage interacting
with harmonics of the local oscillator in the mixer.

Eg:

A 100MHz FM carrier generates a harmonic at 200MHz in the receiver.

When the local oscillator is adjusted to 94.65 MHz, its second harmonic is
189.3 MHz.

The difference frequency is then 10.7 MHz - so goes through to the FM
detector.

In this situation, the FM deviation is doubled so the recovered audio will
be distorted on loud passages.



..... Phil