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Re: Hey Gang... DSP Modems... and EM-04



Hi Dave

If you want to try to work the 1200bps sats, my main tip here is to mention
the difference between 1200BPSK (used on most 1200 sats) and 1200AFSK used
on by far most TNC modems. You'll probably be more than happy with the 9600
birds, though.

The only commercially available TNC/Modem NEW which does nearly all the sats
is the Paccomm TNC-NB96/PSK-1 satellite combo that I'm aware of. It's not
true DSP, however.

I'm currently attempting (make that *thinking about*)  modifying it for use
on UO-36, which it doesn't support out of the box. This should be a small
change to the G3RUH modem components, and an IF wide enough on RX to handle
it. Not sure if the TNC will handle 9600 up/38400 down without some more
surgery though.

The main advantage you get with this combo is that you have 1200 BPSK
available. If a TNC doesn't specifically say it supports this mode, you can
bet it won't! Unfortunately by the time I had a good enough station to
properly copy this mode, LO-19 went ga-ga and sends only CW now. I've had no
success with my limited attempts on AO-16. I can hear it, but it just
doesn't listen to me.

The Paccomm combo does work very well on the 9600 sats. As Laura mentioned,
so should any other 9600 G3RUH TNC. The Paccomm combo also needs a bit of
TLC to get it to work OK IMHO so I put a bit of info on
www.btinternet.com.~hlong to explain briefly what I had to do to get it to
work.

I believe that the LL Grace DSP-12 and AEA (aka Timewave) DSP-1232/DSP-2232
also support 1200BPSK but they're not available new.

Another advantage is that the PSK-1 supports the 400bps RUDAK speed which I
believe may be used sometimes on P3D.

A really great read is the AMSAT Digital Satellite Guide. Off topic, there's
also the best explanation I've seen of why preamps work so well at the mast.

Wisp is a great program. When I first got it working (see
http://www.ne.jp/asahi/hamradio/je9pel which has a great explanation of
setup), it was so weird to see it churning away. You feel as though you
might as well not be there and go and make a cup of tea.

Only problem with the digi sats is that IMHO you really do need those
directional antennas. Nothing big. But than I guess you've got more than
enough with those M2 babies unless they're still caught up in your vertical!

73 & Good Luck Howard G6LVB

----- Original Message -----
From: "David M. Tipton, PhD" <tiptond@psi.com>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, September 18, 2000 2:39 AM
Subject: [amsat-bb] Hey Gang... DSP Modems... and EM-04


> Hi Folks,
>
> I was up in EM-04 last night and tried to activate it with no
> success..  Might have just been too many trees...  I'll be back up there
in
> a month or so.  Anyone know how rare that square is?
>
> Anyway, the real question...  I want to buy a packet modem for digital
> satellite use.  Can anyone recommend one?  What should I be looking for
> anyway?  I don't know much about this aspect of it, but I've seen WISP
> used, and it looks neat.  Additionally, I'd like to try some
expirementation.
>
> I have a sound card in my PC, and wouldn't mind buying a "Rig Blaster" but
> is this type of scenario feasible?
>
> Dave, N8KXA/5
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

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