From: Jonathan Naylor (caao.kofy@goldsys.com)
Date: Fri Aug 16 2002 - 10:13:58 EEST
Hi Jason
> We've been doing similar tests here, trying all the 'new' data
> and weak signal modes. They're designed for EME or MS etc, and
> don't cope very well with scintilations introduded by long
> atmospheric distortion. They work, but if you do a waterfall,
> you can see the signal spread is at least one tone wide so a
> system for tropo would probably work better with less tones.
I remember reading that JT44 was designed for 2m (and lower) and that
any others bands it worked on were a bonus. I know that it has been
used on 23cms EME by a very marginal station, but I doubt it would work
on 3cms EME where the spreading is rather large.
I think that going to 1 minute periods would also be a good step and as
you mention going for less tones with wider spacing. To do a proper
implementation, it would be good to have some data from the 3cms EME
ops on what spreading is like, quantitative rather than qualitative.
> So we're thinking about a new system specifically for tropo
> contacts, your ideas would be appreciated...
My first priority is to get my JT44 program working, and then maybe
FSK441 for MS work. I do think that my work could be the basis of
better things as it uses a C++ framework that is rather flexible. I
also make use of external libraries such as FFTW and libaudiofile to
enable me to get round the tedious bits. BTW I am active on 6cms and
3cms tropo work with quite an effective system.
My JT44 TX program made its first noises last night ! The timings are
right (PTT, sound start and end, etc), but I would like a wav file of
real JT44 sending Z's and/or 0's for me to compare. I don't have real
JT44 here (no Windows) so I am working a little in the dark.
Just shout if you want a snapshot of the code.
> Jason
Jonathan HB9DRD/G4KLX
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