We here in the communications industry have seen 2 uses for the Received
Signal Strength Indicator. The first is connecting a voltmeter to aid in
aiming a beam. The second is an internally programmable function that serves
to conserve power by reducing output power according to the strength of the
incoming signal on handheld units, it can conserve battery power when 2
handhelds are talking to each other, but it can also cause a handheld to cut
back too far when talking with a mobile. Obviously this feature should be
used with care, only on non-repeater frequencies, and only in applications
which do not use 50w mobile units.
$.02 KF4HAZ - Lonnie
----- From: "Rick C." <rixy@

> Some FM chips might have a pin to provide signal strength indicators by
> measuring saturation of the IF, but I have never seen this line
controlling
> the gain of the RF. Don't forget, we're talking about a Part 15
transmitter
> outputting in the milliwatts, and I can't see this level coming anywhere
> close to overloading the input. And even if there were ample RF energy, it
> would probably overload every stage of the receiver and do more harm of
> environmental exposure rather than attenuating the audio level because of
> IMD. I've taken a walkman up to the base of a 50,000 watt FM tower and
never
> had an audio attenuation problem unless I was listening to an adjacent
> channel. ;-)
>
> If you reference me to a domestic (consumer type) FM receiver model with
AGC,
> I would like to know so I can change my statement as to never seeing an FM
> AGC circuit.
>
> Rick
>
> "Alan B. Pearce" wrote:
>
> > >I've never seen an FM receiver with AGC. RF intensity
> > >should have no effect on FM audio levels. AM however,
> > >this would be true. FM receivers do have AFC to
> > >keep the receiver from loosing lock.
> >
> > Post mixer I would agree with you, but I have seen gain control on the
RF
> > stage to get good IM performance. I seem to recall some early FM IF
chips
> > had a signal strength output to do this.
> >
> > If there is no AGC at all that may even exacerbate the problem if he is
> > feeding a very strong signal into the receiver. The IM resultant may be
> > producing a similar problem.
>

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