I believe they used audio derived AGC to get the audio notch in the AGC
Carl Moreschi N4PY
----- Original Message -----
To: "Dr. Gerald N. Johnson, electrical engineer" <firstname.lastname@example.org>;
"TimEnglish" <email@example.com>; <firstname.lastname@example.org>
Sent: Tuesday, April 30, 2002 11:35 AM
Subject: Re: [TenTec] Would like Corsair II comments
> Just curious about the filter delay comment. I always thought the delay
> was in the audio/agc circuit which caused it not to respond as fast as it
> should. Also can you comment on why you think TT used audio agc instead
> of IF agc? I've seen some really simple IF agc circuits that work great.
> Do you suppose it was just a carry over from the Triton/Argo days when cw
> selectivity was dependent on the af filter being in the agc loop?
> -----Original Message-----
> From: "Dr. Gerald N. Johnson, electrical engineer" <email@example.com>
> To: Tim English <firstname.lastname@example.org>
> Date: Mon, 29 Apr 2002 21:54:06 -0500
> Subject: Re: [TenTec] Would like Corsair II comments
> > I see reports that the Corsair II is noisy. It just has lots of gain
> > but
> > the RF stage uses circuitry that should be very quiet. Practically
> > quiet
> > enough for VHF/UHF without a significant preamp.
> > The band pass tuning of the Corsair II works very well, even with only
> > SSB filters it can be cranked down to really narrow for CW. I've hardly
> > ever felt a great need for the narrow filter (which I do have) except
> > to
> > be able to set the pitch of the received signal where I want it at the
> > time. AGC is very good, but more calm on a good antenna with the RF
> > gain
> > backed off. AGC is audio derived so doesn't rise quite as fast as if it
> > was IF derived and strong signals can make a leading edge click because
> > of the crystal filter delays.
> > On 75 with a good antenna I run mine with RF backed to about 3 PM on
> > the
> > knob and the "attenuator" (RF gain knob pulled, actually no RF stage at
> > all) in the circuit. Works really fine. And isn't bothered by the
> > strong
> > signals on adjacent frequencies that bothered my other brands of radio.
> > The filter response also is such that it passes lightning as clicks,
> > doesn't convert lightning to crashes (characteristic of most crystal
> > and
> > mechanical filters) so it works on the low bands in the summertime very
> > well.
> > I'm not interested in any offers for my Corsair II.
> > 73, Jerry, K0CQ
> > --
> > Entire content copyright Dr. Gerald N. Johnson. Reproduction by
> > permission only.
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