Jerry, the Kachina 505DSP used a similar combination AGC arrangement
and provided a separate control for adjusting the degree of AGC
control in the front end, etc.
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489 IC-765 #2349 IC-756 PRO #2121 IC-756 PRO2 #3235
----- Original Message -----
From: "Dr. Gerald N. Johnson, electrical engineer"
<geraldj@isunet.net>
To: "Mark Erbaugh" <mark@microenh.com>
Cc: <tentec@contesting.com>
Sent: Wednesday, January 29, 2003 10:50 AM
Subject: Re: [TenTec] Pegasus S-Meter Anomaly
> It would be logical to me for the RF AGC to be fast while the audio
AGC
> was slow and for the RF AGC to be faster on strong signals to
protect
> the A/D better. The DSP always works better with the strongest
signal
> that doesn't clip going in. So when there is a lot of RF gain
reduction,
> its expedient to drop the AGC rapidly so that a weak signal
following
> the strong signal isn't lost in digitizing noise. Yet there still
has to
> be a fast attack to protect the A/D from being driven into clipping.
> When you over drive the A/D the clipping is BRICKWALL hard.
>
> It would be nice if the displayed AGC were a smart combination of RF
and
> audio AGC with the result slowed to the audio time constant. You
could
> probably do that in software based on AGC reading. E.g. integrate
the
> values with a couple seconds time constant, especially above the
signal
> level that you see showing syllabic variations.
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