At 12/17/2005 11:07, you wrote:
>Bob M. wrote:
>
> >I found that the 17dB gain was way too much for the receiver, and the
> noise level increased dramatically, to the point that I had to tighten
> the squelch settings.
> >
>
>Think about this for a minute, if the noise level increased, the squelch
>circuit would have seen MORE noise and rammed the squelch closed.
>What actually happened is, adding a better device in front of the
>receiver lowered the receivers total noise figure, decreasing the noise
>in the squelch circuit, requiring the squelch pot to be set tighter.
>Very common effect.
Common? Must be another explanation, as you're talking apples & oranges
here w.r.t. noise. Remember this is FM, so more noise power at the front
end doesn't mean more noise at the discriminator unless the limiter isn't
being driven into limiting, which is probably what's happening. But adding
a preamp can only add total noise power, never subtract.
Bob NO6B
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