Well, I may not be an AGC buff, but it looks like the Corsair II is doing
its AGC similar to what you described for the Omni C. The AGC voltage is
derived after the audio notch filter, and before the audio passband filter.
The darlington in the Omni has been replaced by an op-amp and a bipolar
driver. The three pin diodes are used to shunt the signal into and out of
the 2 stages of IF amplification. The RF gain control sets of operating
point of these 2 stages.
There seems to be two signal paths into the op-amp. One is a conventional
amplifier, with the RC time constants. The other path is through another
op-amp that drives a full wave rectifier, with no apparent RC time
constants. This probably provides the fast attack that keeps that strong
signal from blasting through on its leading edge. That was a problem on
the Omni C that I had before upgrading to the Corsair II.
Hope this answers some questions.
Howard Smith, WA9AXQ
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