I have been examining the WSJT9.7 and WSJT-X 1.8 waterfalls running
JT65b to try and pin down why some find one preferable to another.
At the moment they are fed with the same 44.1kHz 16bit signals of 144Mhz
sky (well, moon actually ) noise
The noise (a '-26' floor) in WSJT-X appears 'stretched' in the x-axis
compared to the pointillist appearance of the noise ('-33') in WSJT.
This may be the difference in display real estate; it is difficult to
match the time and frequency display dimensions as a result of the
differences in window sizing methods. A ruler shows WSJT-X to have maybe
~25% greater x dimension for the same bandwidth, and there is ~10%
greater y dimension for the same time span.
Even allowing for these differences, the WSJT-X x-axis appears to have
additional 'smearing', which I initially thought to be possibly the
product of some difference in averaging methods.
Looking deeper shows that the palette positioning in each is different:
WSJT-X appeared to me to have a 3-colour range (dark blue, light blue
and yellow); only a line-of-sight local EME signal eventually revealed
red. WSJT appeared to have 4 colours (blue, green, red, white) but
positioned at different levels . I do not know the relative amplitudes
of palette colour positioning but it is possible that the increased
colour granularity of WSJT is improving the subjective appearance, with
WSJT-X using yellow across a wider range - thus joining and thus
'stretching' noise spikes of dissimilar amplitude.
In practice, after a little tweaking, I find the WSJT-X 3-colour
waterfall reveals signals as well as WSJT, just not as 'precisely'. In
addition, if an observer's judgement is skewed by report differences
between the two, it can reinforce the impression that WSJT "shows weak
signals better".
Finally, I have turned off DS (and renamed all the CALL3.txt files) and
so far operation leads me to believe that WSJT-X in my system is
sometimes decoding slightly better than WSJT. This anecdotal evidence is
obviously not as compelling as Charlie's heroic efforts.
73
Pete G4PLZ
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