Philip Leonard WVØT wrote: > Does anyone run 100wpm ASCII RTY anymore. The story of ASCII operation on HF is interesting because it was one of those issues where there was a strong desire by some hams to have this capability back when we could only use 5 level code such as RTTY. If we could run HF ASCII we would be able to get out of the technology jail.
Within a few days after the FCC approved the use of HF ASCII (1980, typically operated at 110 baud, hams discovered it was not the most practical mode for HF, performing at a much lower level than RTTY and of course, that does make sense when you consider the need for the increased data throughput, but using the same basic waveform. The ARRL had made pretty big technical issue out of being able to run ASCII on HF and, if time permitted, began repeating bulletins with 110 Baud ASCII after the regular RTTY and AMTOR FEC Mode B bulletins. They still do this today even though we have much, much better digital modes available at the same speed and able to send the full ASCII set. I suppose it would be a big decision as to which mode or modes to use, but it seems to me that both AMTOR FEC and 110 Baud ASCII should be dropped and replaced by one superior mode. I expect you would get some disagreement on which mode would be best, but the selective criteria to me would be: - more sensitive than current modes - more robustness from coding gain or FEC - spectrum efficient - similar or faster speed AMTOR mode B has limited character set, 100 baud waveform with 71 wpm, and around -5 dB S/N with perhaps 800 Hz bandwidth. 110 baud ASCII has full character set, 110 wpm, with -2 dB S/N at similar BW. To put it in perspective, RTTY is not that great either with the limited character set, 45 baud at 60 wpm, and -5 to -6 dB S/N with a narrower bandwidth. So which mode would be a reasonable choice today that can match the speed, BW, and work better? Actually, it is not that easy to come up with modes that have the speed of 60 to 100+ wpm since they have typically been optimized for keyboard chatting, not serious messaging. I am betting DominoEX22/FEC might do better and have a throughput of 77 wpm with a baud rate of ~ 22 and with -10 dB S/N and a narrower bandwidth (~ < 400 Hz) than any of the other modes. But it is not commonly available on most sound card software. (It also has good drift tolerance and off tuning tolerance). 73, Rick, KV9U > > >
