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[WriteLog] Sound Card Demodulation questions

To: <writelog@contesting.com>
Subject: [WriteLog] Sound Card Demodulation questions
From: jfleming@shelbynet.net (WA9ALS - John)
Date: Mon, 8 Jan 2001 17:37:21 -0500
> I saw K5ZD's comment that "If he could hear the signal, the sound
> card would print it." That was not quite my experience here. The
> print was generally quite good (1171 QSO's!), but there were times,
> especially on the Europeans, where it would just not print. Some
> of these signals were quite loud, but you could hear the flutter
> on them. It's a 3 hop polar path to EU from here. The soundcard
> also had a little trouble with backscatter stations from California.

I think we've all experienced this.  From here on North Caicos, and from
home in Indiana, I have experienced JA's at times and EU lots of times in
marginal conditions when the polar flutter makes the signal difficult to
print, even though it SOUNDS plenty strong.  Prior to this trip I spent a
lot of time trying to figure out what demodulator to use among my available
choices of soundcard/RttyRite, soundcard/RITTY-K6STI, PK-232, or DXP38.

Seemed that nothing was "perfect" - That is, each combo lacked something .
I wanted.  I think the DXP38 and K6STI print the best, especially with
Brian's new filters in v4x.  However, K6STI has to be used with WF1B, and
the DXP38 has no AFC.  After a lot of testing, I decided that RttyRite with
the Wide Band Decode feature engaged approached the print of K6STI or the
DXP.  Thus I went with the soundcard/RttyRite combo to get the AFC.  I
originally planned 2R, and I was going to use the DXP38 on the second radio.
However, due to a last minute problem with my USB serial adapter, I lost 3
ports I was planning to use and ended up going 1R with soundcard/RttyRite.
I couldn't have survived without the wide band decode!  Many times I just
had garbage in the main screen but the wide band decode window had perfect
print!!!

The other problem with the DXP38 besides no AFC is that the delta-f (most
sensitive) tuning mode is SLOW.  In retrospect, I wish I had gone with this:
Use the DXP38 to decode (just in case it's better than RttyRite, and it
might not be).  However, I would have paralleled the audio to the soundcard
and had the RttyRite tuning window open on the screen.  Thus I could use the
RttyRite tuning indicator (fast) to tune the station manually, but get the
print from the DXP if it was better.

The other option I've heard of is just to have RITTY/K6STI running on
another machine and look over at it if your main decoder fails!  HI

Overall, Writelog performed almost flawlessly!  I never had to reboot.  One
time I lost the spectral display and had to restart WL to get it back.  And
very weird, one time I saw a lower case blue "i" print instead of it's
capital!  HI  73
http://www.qsl.net/wa9als/vp5photos.htm



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