running dogg wrote:

As I understand it, it is the front end transistor(s) that are being
overloaded when somebody talks about "antenna overload". This problem
occurs mostly with cheap portables. Since they are built cheaply, the
front ends are also cheap and do not have the selectivity of a better
quality receiver. Clipping a length of wire to the whip of one of these
portables will pick up images mostly of AM and FM stations that are in
the vicinity of the receiver. For example, I have a cheap Radio Shack
AM/FM radio that is easily overloaded. Just pointing the whip antenna in
the direction of the nearest FM station (about two miles away) is
sufficient to produce images of that station all over the dial. The
problem is not with the whip, it is the front end.

Correct, which includes the first mixer too. Either the front end needs
better preselection using some kind of LC circuits and/or the active
componants (transistors) need to be operated at higher voltages to
provide more 'headroom' from overloading. A good receiver uses both
methods in conjunction with well designed RF amp's and mixers'.


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