Hi Steve,
Thanks once more for your excellent work on the JT65 decoder!!
I have confirmed your results using the test program jt65[.exe]. I then
went ahead and merged your changes into v1.6.1 of WSJT-X; it's now
performing at least as well as the WSJT decoder for the S/N=-24 dB files
produced by SimJT. At the same time, its two-pass algorithm beats all
previous JT65 decoders on any crowded HF band.
I haven't yet decided how best to organize the necessary on-screen
controls to allow user-selection of decoding parameters optimized for HF
or EME-style operation. SVN revision 6038 uses one possible approach.
On the Settings | Advanced tab you can select 2-pass decoding, or not;
the setting defaults to ON. If a band is not crowded so you don't need
the second pass, you can turn it off and decoding will finish more quickly.
Using full-symbol coherent integration is definitely the right thing to
do for JT65A. I had experimented with half-symbol integration because
on EME bands where the B and C sub-modes are used there's enough Doppler
spread that you need either that approach or some post-FFT
smoothing of the spectra.
I haven't yet looked into why it might be that fitting for the "banana
coefficient" a(3), and then ignoring the fitted value, seems to help.
I've got a busy week here -- a conference celebrating the 100th
anniversary of Einstein's general relativity theory -- so I probably
won't get back to this until next week.
-- Joe, K1JT
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