Hi Jim,
Without specifics and saved .wav files it's impossible to comment in any
detail on your false decodes.
When developing the two-pass decoder, we analyzed over a thousand .wav
files in crowded band conditions. The probability of false decodes was
higher for second-pass decodes than for first-pass decodes, but was
still less than 1 percent. We considered that an acceptable price for
the big advantage of many good decodes of very weak, otherwise buried
signals.
False decodes are almost always easy to recognize as such. Roughly half
should be random, garbled free text. The other half will contain things
that look vaguely like two callsigns [or CQ/QRZ/DE ... plus one
callsign], and probably a locator. Usually one or both of the
"callsigns" will have a nonstandard, bogus-looking prefix. There will
*not* be any correlation between the apparent prefix and the locator.
-- 73, Joe, K1JT
On 12/15/2016 3:04 AM, Jim Brown wrote:
> Hi Team,
>
> For several weeks, I've been letting WSJT-X rc3 run overnight on 160M
> while I sleep, and tabulating the decodes the next day. I've been quite
> pleasantly surprised by the activity -- in less than a month, I've
> decoded about 450 different stations running JT65 or JT9. More than a
> dozen are from outside North America, about half of those from western EU.
>
> The reason for this post is that I've also seen a half dozen or so
> decodes that appear to be false. Looking more closely, I see that most
> are second decodes finding the signal underneath another one that
> decodes correctly.
>
> I haven't done enough analysis to say that ALL second decodes are bogus,
> but nearly all of the bogus decodes are on second passes. On each of
> them, I can't find the call on qrz.com, the call often doesn't make
> sense, and the time of day doesn't support propagation to me (near San
> Francisco) from the received grid square. BUT -- the grid square usually
> roughly correlates with the country associated with the call (which is
> usually a non-standard prefix for that country).
>
> 73, Jim K9YC
>
>
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