>To be honest, using a high speed baud rate modem on HF and then encoding >it to > >slow down the effective bps, seems the exact opposite of what is > normally done > >with slower baud rate and higher order modulation to get the higher > throughput.
Rick, The actual BPS rate for 188-110B is 7200, for 188-141B it is 375. Higher order modulation is being used to get higher throughput. In the case of 188-110B you have in some cases much heavier use of FEC, redundancy and training. The question remains about the symbol times. We know that 300 baud packet is not useless on HF, although it is not optimized. I would like to re-conduct the experiments that were run in 2002 where the baud rate of HF packet was reduced. This time perhaps leaving the shift at 200 Hz and reducing the Baud rate to 100. I think however the long QSB will still be the major contributing factor to failure of packets. Since you have to decode the entire frame and get a good CRC, you are better off with short frame times. So far this has been the case with my QSO's using 188-141A. The shorter the message, the better the chance of success. Anyone for some 100 Baud packet? 73, Mark N5RFX 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/
