Re: VLF: EbNaut transmission on 8270.1 Hz again - 73

[Paul Nicholson <vlf0403@abelian.org>]

> I noticed that in ebnaut-rx v0.4d the output with
> best rank seems to persist, rather than the one
> with fewest symbol errors

It actually keeps the decode with the best path
metric.   The other options (best rank, best BER)
don't perform so well on average.   The log file
doesn't show the path metric though, I'll fix that
for the next revision.

With the Viterbi decoder using soft decisions with
Euclidean distance metric, the path metric is equivalent
to the cross-correlation of the signal and the message
symbols.  The decoder is effectively doing a 'deep search'
which tests all possible messages, not just a short list.

I can't convince my decoder to produce anything other
than 'V3' on this one.  Hamming distance between 73 and
V3 is 180.    The differences are pretty evenly spread
through the messages.
--
Paul Nicholson
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