First of all Tim, in my mind the CorsairII is a "keeper". And I
am one of those who actually like the operation of the hang
AGC. I much prefer the hang action to AGC that is constantly
changing the gain of the IF. It makes the signals much more
natural with less background noise as Jerry mentions below.
Regarding Jerry's comments, I happen to have an Omni D "C
Series" with the Ron Lee AGC modification. That radio is far
and away the best radio I have ever used with regard to AGC
action. Although the AGC is audio derived it is superb. I have
Ron's write-up describing the design. As I recall, he mentions
many of the same things Jerry points out and he, Ron, designed
a modification to overcome all the deficiencies. That radio
proves that audio AGC can be very effective when properly
applied. It is my understanding [and it may be fokelore] that
Ten Tec used a simplified version of Ron's AGC in the Corsair
II. Maybe someone here knows if that is true.
On 30 Apr 2002 at 8:19, Dr. Gerald N. Johnson, electr wrote:
> Since the RF envelope and the audio envelope in SSB do not correspond,
> audio derived AGC tends to produce a smoother audio output. (Its
> analogous to audio clipping versus SSB RF clipping, where the flat
> tops of the audio clipping lead to spikes in the RF envelope, exactly
> the opposite of that desired for best use of the transmitter amplifier
> stages). Deriving the AGC at audio and controlling mostly gain stages
> before the crystal filter and detector does lead to a problem at the
> attack because there's a bit of signal past the control stages when
> the AGC arrives at the control stages. Part of it is time delay in the
> crystal filter, a little is time delay in the gain stages, some is in
> the post detection low pass filter. Plus the fact that the AGC tends
> to work on peaks and the fastest audio half cycle is going to be 0.2
> millisecond from zero to peak, (2.5 KHz) but the average audio half
> cycle is going to be at least 5 times longer, a millisecond. Leads to
> clicks on the attack side of the incoming signals.
>
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