Many years ago, I had a home-brew RTTY TU. It had two 88 mH torroids in the tuned circuits and a differential amplifier as a detector. Occasionally, the received signal would fade below the noise, but the Kleinschmidt teleprinter would keep printing the decoded text. I have tried several current software packages for decoding RTTY signals, and all of them require quite strong signals to decode at all, and very strong signals to provide 100% print.
I was wondering if the decoding method used in WSJT-X for FT8 could be ported to a RTTY decoder. I realize that FT8 has a lower symbol rate, which provides more time to integrate, and incorporates redundancy, which improves accuracy. But the theoretical lower limit for decoding RTTY is something like -5 dB S/N, and the current programs are nowhere near that. If RTTY facilities could be integrated with WSJT-X, not only would the decoding be better, but the log scanning functions of WSJT-X and JTAlert would be better, significantly improving contest operation. I confess I haven't looked at the decoding techniques used by RTTY software, but I suspect, based on performance, that it could be improved. 73, Frank KF6E
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