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Re: Sound cards for 9600



hobergenix@sbcglobal.net wrote:
> I was wondering what sound cards work well with 9600. Is
> their a list of reccomended cards to use. Or is trying to
> copy 9600 baud with a sound card and software program
> not too successful?

I've had good success demodulating 9600 and 38k4
baud signals with soundcards.  At these speeds it
is not plug-n-play. You need to pay attention to
the audio signal levels and adjust the soundcard
volume controls on the PC so that you don't over
or under drive. This makes the difference between
receiving no packets and receiving lots of packets.
It's easy to adjust by running SNDVOL32.EXE but
use the keyboard arrow keys to move the sliders
up and down. Don't use the mouse.

If you're just getting started at 9600 baud on
satellites, try GO-32.  It has a stronger signal.

For soundcards, I know of only one effort to
seriously test various cards and that was the one
performed by Bob McGwier, N4HY. You can read it
here:

http://www.amsat.org/amsat/archive/amsat-bb/200308/msg00494.html

I have had good results demodulating packets from
the Turtle Beach Santa Cruz and I also used the
soundcard built into an old Toshiba laptop. Some
other laptop soundcards can have mixed results.

For software, if you want to send AND receive at
9600, and if you are running Windows, then try
AGWPE or MixW.

I'm also working on my own receive-only soundcard DSP
modem for 9600 and 38,400 baud. The emphasis is
on receiving satellite telemetry with the idea of
"try harder to receive more of the packets." My
version includes a pair of moving-average peak
detectors, a fractionally spaced equalizer with
decision feedback, and raised cosine filtering.
You can read about it in the 2005 AMSAT Symposium
Proceedings in the paper "A First Look at a New
Soundcard DSP Modem for Satellite Telemetry." I've
made some improvements since I wrote the paper.

Let me know if you have any questions.

Douglas KA2UPW/5
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