Depending upon your definition of "robust," and, if you are using the modes on HF, with a wide bandwitch (voice width) ARQ mode, it would seem to be Pactor 3 which can adjust the speed to meet varying conditions. Raw speed up to SL6 at 3600 bps which can yield a net user data rate of 2722 bps. With compression, this can yield over 5000 wpm throughput. Of course these are for very good conditions which is necessary for these high speeds. The SL1 slowest speed under the worst conditions, is 200 bps yielding ~ 77 bps and four other levels in between.
The only sound card mode that can match this with good signals was the SCAMP protocol, but it did not have a fall back mode such as P3 had and was abandoned by the Winlink 2000 developer. For other sound card modes, there are few modes that have been designed to approach even a 400 bps rate. Even MT-63 at the 200 wpm rate is well under that speed. AX.25 at 300 baud would not have a good enough throughput, but 1200 baud (10 meters and up) could do this with perhaps a 600 net throughput. I had heard something about the voice codec a while ago and can not remember if this was open source software or not, but it would not be difficult to do this. Many years ago, I assembled a Heath HERO robot kit as a demonstration project for the agency I worked with at the time and it was relatively simple to program speech by using various phonemes. I am not sure how useful this would be though. 73, Rick, KV9U cesco12342000 wrote: > Question to the experts: > > What is the most robust digi-mode with a 400 to 600 bps raw capacity (or > 200 to 300 bps fec capacity) ? > > Is a boosted psk variant the best coice or is mfsk capable of such rates ? > > Other options ? > > Background: > Seems someone has developed a 200bps voice codec. It's a phoneme coder. > The data rate and the description sounds plausible. I dont know if this > will ever be available as "open source" for amateurs, but it would be > intresting to estimate the possibilities of such a codec for DV (digital > voice). > Such a coder could probably beat analog ssb in terms of robustness in > marginal conditions. > > > > > > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/drsked/drsked.php > > Yahoo! Groups Links > > > > > > >
