in my opinion, beating SSB on HF is not the low hanging fruit, VHF is the low hanging fruit...
HF is a much more difficult place to beat SSB. Why ? because SSB operators will work around 0dB SNR but also lose every 3rd or 4th syllable and still get a copy. perhaps 80mS out of every 300mS If the digital channel was losing that much, it might well be unusable because the transitions into the lost syllable are hard and digital, where as the transition into the lost silly-bulls for the analog voice is, well, more analog and less defined. in addition the modem flywheel must work very hard in those condix due to the lack of deep interleaving/ long FEC frames in addition to the modem that really is optimized more for fast acquisition rather than surviving a 25% loss rate. (needing slowe time constants and / or a more robust/ effective /sophisticated predictor on the clock bit recovery) Channels in VHF are usually stationary over a word..... Aurora thought that is much harder! wonder if freeDV would even lock at low SNR. but that is an outlier on usage.... On 8/02/2017 8:00 AM, Bruce Perens wrote: > I should point out that my original evangelism of Open Source digital > voice codecs, which nudged David to revisit his thesis, was directed > toward replacing the ones used on VHF/UHF. We do have definite > performance advantages there given SDR radios rather than FM > modulators and detectors. Adoption of this has been delayed due to the > necessity to manufacture our own radios. > > HF is low hanging fruit in that we don't have to modify the radios. > Beating SSB for DX use is a great metric to pursue, and seems to be > motivating David to do much fruitful research. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
