One other thing to think about is if the IF gain pot
has been "tweaked" for more gain you will see
degradation of the strong signal handling capability
of the Pegasus (the Jupiter too I would assume). When
the topic of the phantom signals was posted here on
the reflector a month or so ago I did some experiments
where I tried some different settings of the IF gain
pot, sure enough I could aggravate that problem with
ease. And one of the other obvious symptoms was clicks
and crackles from strong off frequency signals in
addition to phantom signals.
And yes there are two AGC loops, presumably then the
factory setting for the IF gain pot is optimized for
each to work within their own ranges properly, if you
bump up the IF gain pot then all bets are off.
Duane
N9DG
--- Mark Erbaugh <mark@microenh.com> wrote:
> Jerry,
>
> Thanks for the reply. In previous correspondence
> with Gary Barbour at
> TenTec, he did tell me that the SMeter reading is
> actually a combination of
> both the analog RF and digital signal levels.
>
> My problem wasn't receiving interference from a
> strong off-channel signal
> (although I do notice that from time to time - when
> the old TenTec 20m net
> was 5 kHz above the Collins net, a couple of
> stations on the Collins net
> caused a crackling noise when I was listening to the
> TenTec net). I suspect
> that in addition to being strong signals, they were
> also a tad wide.
>
> The SMeter was following the audio of the on-channel
> signal. The 75m
> incident I mentioned was with two stations in QSO on
> the same frequency. The
> SMeter acted up for the stronger one, but not for
> the weaker one (although
> the weaker one was still 10 db over S9 - because of
> the SMeter acting up,
> I'm not really sure of the strength of the stronger
> one - it was as least 20
> to 30 db over )
>
> Mark
>
> ----- Original Message -----
> From: "Dr. Gerald N. Johnson, electrical engineer"
> <geraldj@isunet.net>
> To: "Mark Erbaugh" <mark@microenh.com>
> Cc: <tentec@contesting.com>
> Sent: Tuesday, January 28, 2003 22:35 PM
> Subject: Re: [TenTec] Pegasus S-Meter Anomaly
>
>
> > It may be that there are two AVC loops. I'd expect
> one working at RF to
> > protect the A/D from being overdriven, and a
> second one working after
> > detection and filtering to level the audio for the
> speaker. It may be
> > that the simple AVC reading option reads only the
> RF AVC. If so, that
> > could show a strong signal indication while
> receiving a weak signal
> > adjacent to a strong signal, when the strong
> signal was still in the A/D
> > input passband. But the combination of the strong
> RF AVC and weak audio
> > AVC ideally should be indicated as a weak signal.
> >
> > 73, Jerry, K0CQ
> >
> > --
> > Entire content copyright Dr. Gerald N. Johnson,
> electrical engineer.
> > Reproduction by permission only.
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