Everything I have ever read leads me to believe than any baud rate below 40-50 baud is Ok for NVIS operation on HF. The lower the baud rate the better to a point. The more/better (more robust) FEC you have the better change for error free (near error free) copy. There is also a consideration concerning which method of moculating the carrier/signal/tone works best on HF.
I believe that when talking about NVIS type and over-the-pole communications, some quite different conditions exist where the type of modulation, baud rates and FEC for these two signal conditions will differ greatly. What might work very well on NVIS paths may not work well on over-the-pole paths. 73, Walt/K5YFW -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of Vojtech Bubnik Sent: Wednesday, November 01, 2006 3:11 AM To: [email protected] Subject: [digitalradio] New digital mode proposal for CW transceivers Hi gang. I am thinking of learning my SW+40 to talk digitally. I know of only two digital modes that may be exercised on this TRX without any hardware modification: morse and feld hell. The third possibility would be RTTY, but it would need to modify the TRX slightly. Although it may be done on SW+, the VFO pulling will be more dificult on direct conversion rigs, where the frequency shift is dependent on the frequency. The most used digital mode is still morse. The problem with computer decoded morse is that it is usually asynchronous and speed varies. Computers have great dificulty to decode morse signal under bad conditions. I know there have been some synchronous CW experiments, but the SCW mode was not widely accepted, mostly because PSK decoder may decode -3dB weaker signal. But how about modifying PSK31 software modem to send CW modulated signal? As far as my DSP knowledge goes it will be about 3dB worse than PSK31, but the signal will be wider than of PSK31. Never mind, it will be intended for QRP operation. PSK31 symbol speed is too fast for NVIS. PSK31 is hurt baddly by polar flutter. The new CW modulated mode will probably be not too much affected by polar flutter. Am I right? The speed of BPSK31 is about 40WPM. It makes sense to go down to 16 symbols per second to make the mode better for NVIS and still be usable. Or use the same symbol speed 31 and add simple FEC, for example from QPSK31, 2dB will be gained. How about that? Does it make sense to create another mode? 73, Vojtech OK1IAK 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 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/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> 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/
