the new amateur radio digital voice mode fdmdv, which has a bandwidth of just 1.1 khz, seems from initial tests to produce good results.
fdmdv achieves it's very low bandwidth, just 1.1 khz, by a combination of a low sample rate and having no forward error correction (fec).
i was initially sceptical of the results that could be achieved but i have been impressed with it's performance given the low bandwidth.
while i still believe the mode would benefit from some fec, which would increase the bandwidth to 1.5 khz, it none-the-less delivers very good results mainly because human speech contains a high level of redundancy (you can miss a lot but still understand what's being said).
this new mode scores from having a low latency. traditional digital voice modes have had a significant delay between you speaking and what you say actually being received at the far end due to fec and interleaving overheads.
that being said, the delays in tradionally amateur radio digital voice modes have always been far better than that achieved by commercial broadcast radio systems.
i understand that some bbc trials of dab receivers showed delays of as much as 7 seconds could occur with certain makes of dab radios.
cesco hb9tlk is to be congratulated for developing this new mode.
trevor m5aka
fdmdv - the page also gives details of fdmdv net times
http://n1su.com/fdmdv/fdmdv download also has usage documentation v1.0
http://n1su.com/fdmdv/download.html melp_1400.dll
http://www.ku7pdx.com/files/melp_dll.zip windrm email group
http://groups-beta.google.com/group/windrm
