Hi, Thanks for an excellent piece of communication protocol both FT8 and FT4. It would be interesting to see how big guns start to use FT4 instead of RTTY. For strong signals RTTY is a bit faster than FT8, but most of the users are not big guns! The bandwidth saving in FT4 is a really big issue, so there will be many more QSOs/min/kHz.
I checked how much timing difference is allowed for a successful decode. It seems that in 23000 successful decodes timing difference is in range -0.5 s to 0.6 s. In FT8 the range is -2.6 s to 2.5 s and 99% of successful decodes are within +/-2 s compared to my timing. I have no idea how much signal strength affects to the result, but for sure in FT4 any practical signal strength increase does not help to extend the range outside the +/- 0.5 s. There are many signals that fall out of that range. So we could recommend clock accuracy +/- 0.25 s or better for FT4. 73, Reino oh3ma
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