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tim gorman · August 23rd 06, 08:52 PM posted to rec.radio.amateur.homebrew

Andrea Baldoni wrote:

wrote:

: If we can get back to the original claim of "increased
: noise with AGC applied" we might be able to help Andrea
: some. We don't know what Andrea has for a main receiver
: and interjecting some "badness" remarks by the ARRL about
: a certain IC isn't going to help clarify Andrea's problem.

Sorry for the short answer. The receiver is a Yaesu FR-101 with his
internal 2m converter. Actually, I'm doing some recalibration but I didn't
found at now nothing really out. I just noted that, mostly noticeable in
FM mode (by noise increasing) but present in all modes looking s-meter,
the response of the IF was not a gaussian with a flat top. In the center
there was a little decreasing area. If you tune it perfectly, you had a
sligtly less signal than little up or down in freq.

................ snip ...........................

Ciao,
AB

Are you sure you are seeing an AGC problem? What you describe above, with
slightly less signal in the center, is typical of a *filter* with dip in
the middle of the passband. This is *not* a result of increased signal
strength causing more AGC and thus more noise when the receiver is tuned to
exact center on a signal. It is the result of a filter design choice (lower
cost) or the result of the filter tuning (tuned for better shape at the
edges which causes more dip in the middle).

Without knowing more about the receiver I can't make any guesses as to what
is in play here but I question if this is an AGC artifact.

tim ab0wr