On Mon, 21 Aug 2006 16:15:01 -0500, 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.

Dual conversion for HF and triple conversion of 2m. There would
not be RF agc on the 2m converter. In FM modes you should see
limiting so agc is behavour is different.

So I started recalibrating. I had stopped because I had trouble with the
noise blanker. In the manual, there is a indication of a test point where
hook a voltmeter, but there is not any test point nor any indication on the
schematic where the exact point is. The transformer is T116, maybe someone
could help. Tomorrow I'll figure out what to do, I think I'll hook the
voltmeter as to measure the voltage rectified, at the gate of the FET.
If you have the schematic (it's freely downloadable in many places) maybe
you could tell if I'm right.

Likely a test point that is not marked on the board. I don't have
a print handy.

Anyway, thankyou very much you want to help troubleshooting my receiver,
but I was using what I noted (increase in noise with AGC on) mainly to
start a general discussion about AGC implementation and effects, and his
future in digital receivers as well as in homebrew very high-end ones. It
has started, and it's very interesting.

Having experimented with recievers since before EE school and still
many decades later I find it challenging. Always looking for and at
new ideas.


Allison