There is always lot of emphasis on getting signals out of the noise. From my 9-months hands on experience using pskmail over a 1500 Mile path from Spain to Sweden and from Montenegro to Sweden, noise is not the problem on the amateur bands, as there is always a frequency you can use which gives you fair signal/noise performance.
The problem is QRM. Consisting of PACTOR, MFSK, OLIVIA, PSK31, and on 30 meters also SSB signals coming on frequency during your qso. Normally that qrm is stronger than the server I am working. FEC does nothing to cure that. MFSK e.g. is inferior to PSK63 in that case, provided I use a 100 Hz filter. The only answer is ARQ. Pskmail will wait until the intruder is gone and finish the transfer when the qrm goes away within a certain time frame. My experience has also shown that it is very difficult to keep a frequency for more than say 30 minutes. Normally it won't take more than 10 minutes before a deaf, dumb and blind operator will spoil your fun with a 9+20 signal on top of you. 73, Rein PA0R > -----Ursprüngliche Nachricht----- > Von: digitalradio@yahoogroups.com > Gesendet: 24.08.06 18:24:46 > An: digitalradio@yahoogroups.com > Betreff: RE: [digitalradio] The digital throughput challenge on HF > > Oh my...you are right about the baud rates of MT63...I was going from memory > and I have the written down. > > The only problem with on-the-air testing is that you Never HAVE THE SAME > CONDITIONS and you can do that with a simulator...but then the military > always has a "fly-off" or "shoot-off". > > I have no doubt that the sound card modes can work down into the noise. > G4HPE(?) did some testing which is on the RSGB site under emergency > communications. He used a software simulator and on-the-air testing. MFSK16 > worked way down into the noise. > > KN6KB in this presentation on SCAMP to the DDC in Nov of 2004 showed his > simulator measurements of P I/II/III and I believe MT63. I have the chart > from the presentation that I will send to anyone interested. > > I have to agree that MT63 or anything else needs to have further development > by knowledgeable individuals. Being more of a project manager type than > technical (programmer) type, over the years I have "specialized" one on > tactical HF antennas and overall communications than specific data modes or > programming...I know a little C and C++ ;-). > > I would hope that some hardware mode better then pactor might come along but > also would like to see single and multiple soundcard modes develop that might > rival Pactor speeds. > > 73, > > Walt/K5YFW > http://pa0r.blogspirit.com Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
