4298Re: [wsjtgroup] Optimization of MS Fresnel zones vs. bit rate & error correction?
- Feb 1, 2008Hi Ross and all,
Ross (N0GSZ) wrote:
> Do any of the WSJT modes use bit rates and error correction codingThe simple answer is no.
> optimized to compensate for signal fluctuations due to constructive and
> destructive interference of specular reflections along a meteor trail?
> If so, at what frequency are Fresnel oscillations presumed to occur?
> Ross N0GSZ
The modes intended for meteor scatter and ionospheric scatter, namely
FSK441 and JT6M, do not include forward error correction.
As for periodic (or quasi-periodic) fading, although they sometimes
occur I have seen no evidence that a modulation scheme could be readily
optimized so as to compensate for it. The fading rate depends on
wavelength and on reflection geometry, so a single solution would be a
compromise at best.
My experience over 8 years of playing with these signals is that a fast
data rate is more important than anything else. FSK441 is thus designed
to use the fastest data rate consistent with the bandwidths of our SSB
-- 73, Joe, K1JT
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