From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Naylor Subject: Re: JT44 on Linux Date: Fri, 16 Aug 2002 09:13:58 +0200 Sender: linux-hams-owner@vger.kernel.org Message-ID: <0208160913580C.00798@g4klx> References: <02081415053208.00798@g4klx> <3D5C9B60.4000405@btinternet.com> Reply-To: g4klx@qsl.net Mime-Version: 1.0 Content-Transfer-Encoding: 7BIT Return-path: In-Reply-To: <3D5C9B60.4000405@btinternet.com> List-Id: Content-Type: text/plain; charset="us-ascii" To: Jason Flynn G7OCD Cc: linux-hams@vger.kernel.org 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