Dr. Lou,
Thanks for the email. After looking at George's website, I was just about
set to order the PSKMETER for my shack as I operate a lot of PSK. However,
one of my rigs is a Pegasus and if the PSKMETER won't work with it, it's
less attactive to me.
I went back to George's PowerPoint presentation and did find the slide where
he mentions turning of AGC. However, that one slide is the only place in
the PowerPoint presentation or in the assembly / operation manual for the
PSKMETER where AGC is mentioned. I'm not sure what George meant by that
comment.
On the Pegasus (and most other radios), the AGC is a function of the
receiver. The AGC reduces the receiver gain to keep strong signals from
overloading the receiver (and your ears).
On the transmit side, most transmitters have an ALC. This has a similar
effect on the tranmitted signal. If you apply a large input audio signal,
the ALC cuts back the drive to the finals in the transmitter to keep from
blowing them up. It seems that since the PSKMETER samples RF, it may be
more concerned with ALC rather than AGC.
What gain control are you talking about on the Pegasus? From the
presentation, it looks like the PSKMETER software attempts to adjust the
sound card line out volume to adjust the transmitted RF waveform. The
Pegasus software doesn't mess with the soundcard at all. I have found a
couple of issues operating PSK31 on the Pegasus. Perhaps one of these may be
causing PSKMETER the problem:
1) The Pegasus mic input level is about 10 times more sensitive that most
rigs. Most rigs need about 50 uV. The Pegasus is happy with 5 uV. It could
be that the PSKMETER can't compensate. For example, it sees the level way to
high and cuts back, but cuts back way too much. Then it sees the level way
to low and boosts it way to much. You may be able to reduce this by padding
the soundcard output before it goes to the Pegasus. I've had good luck with
a 10k Ohm pot. Also note that the line input on the Pegasus isn't really a
line level input. It takes the same input levels as the mic input.
2) I have found the Pegasus very susceptible to ground loops. I have seen
where the same PC / Transceiver interface works fine with one radio, but has
a ground loop as evidenced by severe hum with the Pegasus. I have found that
running a ground from the computer case to the Pegasus ground has helped.
What interface are you using with the Pegasus? Have you been able to work
PSK31 successfully without the PSKMETER?
Let me know how things progress. I'm still interested in the PSKMETER and I
think it has potential.
73,
Mark
----- Original Message -----
From: "Dr. LOU" <madham@verizon.net>
To: <tentec@contesting.com>
Sent: Saturday, July 12, 2003 2:13 PM
Subject: Re: [TenTec] Pegasus AGC.
> Mark I think you will note in George's presentation he states specifically
> to turn OFF your transmitter AGC...I tried the psk meter on my PEGASUS..it
> DON'T WORK as the Pegasus and the psk meter buck heads on the gain
> control....I think GEORGE will agree with this...tnx for your
interest...let
> me know if you find anything else of interest on this subject..have a fine
> day and weekend....73..DR.LOU K3IM
>
>
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