Ed,
There is a strange anomaly that makes no sense yet many of us that (especially)
work weak DX observe frequently ... Sometimes when you end up in a R -XX/RR73
loop ("RR/73 loop" or "ACK dance" as you term it) with a station anecdotally
and observationally sometimes sending 73 sequences back manually appears to
break the loop-cycle.
Why ? it makes no sense when logic is analysed or informed thought is applied
to the observation.
Note that it is not restricted to Weak DX - but is more often observed when
both ends have desperation to complete the QSO.
Yet from my direct observation, experimentation and simulation conducted a
couple of back (when on "down time" with research that I was on - and using
earlier on earlier FT8 releases and the "main fork") it is able to be
replicated - yet inconsistently.
There are "theories" that if the data stream is changed slightly then QRM/QRN
effects that interact with signals passed over the decoder can change and
therefore decoding impasses can be broken ...
More likely the observation is just a statistical/probability anomaly. Yet some
Amateurs SWEAR by this method to break impasses; I also admit that I have often
found it to be observationally useful operationally to break a RR/73 loop !
A "revert and hold" over-ride over Tx4 sequencing when Tx5 is selected may be
useful. Yet without mathematical or statistical justification for it - just
observation and anecdote - it will be hard to convince the core developers of
mitigation strategies that can and will consume valuable signal processing
resources.
73
Steve I
VK3VM / VK3SIR
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