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Subject: [worldcruising] RE: HELP ssb receivers
From: Bruggeman, Jan (janb@XXX.XXX)
Date: Thu Dec 07 2000 - 03:51:35 EST
Hello all,
I'm back to this newsgroup after some time, also because of my second
sailing trip.
I read a question about how to receive weather fax etc...
simplest solution:
- radio receiver: sangean, sony 7600 or better. The radio MUST be able to
receive short wave (freq 150 Khz to 30.000 Khz in SSB modulation (USB and
LSB that is) and must be tunable to 0.1 Khz precize. You do not see that
freq so precise on a sony 7600, but it can do it, you're only working "in
the dark". Best with a radio that uses an external antenna, which can be
just a long wire: a (back)stay
- decoder:
* hamcomm decoder. make it yourself with about 6$ worth of parts,
description of it is in the help function of the (dos) hamcomm software.
* your soundblaster card.
- software: best solution for me is still to run these under dos on an old
computer (I still use a 486 / 33 mhz). Dos because it's single tasking: only
does one thing at a time, does'nt get interupted.
* hamcomm : to decode text messages: navtex, (am)tor, ...
* wvfax : to decode graphical messages: weather fax, ...
* many more programms to be found on the web
The weakest point in this simple solution will be your radio, which has to
stay tuned on a frequency for duration of reception, or some 20 minutes. All
radio's tend to shift a little, this is no problem for voice messages
because these are "broadband", and if your receive frequency drifts a
little, you'll only notice an increase/decrease in tone of the received
voice. Fax is "narrow band", and when your radio drifts away a little, it
does not receive the fax signal anymore. I was only able to "get the feeling
at receiving faxes" while using a sony 7600 (which remains a very desirable
radio, but receiving faxes is a bit beyond what that radio is supposed for)
Stepping into receiving radio fax is a (very good) start at radio
operations, which ends up in taking a Ham radio license. Do remember that
professionals had a separate radio officer on board: handling radios can
become a full time job !
see my website (and many many others, which are better :-)) for some more
details. Feel free to ask any more questions.
mvg,
Jan Bruggeman - ON4AIN
mail: jan@XXX.XXX
web: http://jan.bruggeman.com
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