Re: LF: More EbNaut 137.777 - TA slot

[Paul Nicholson <vlf0403@abelian.org>]

The best 13:30 decode was

 found rank 0: VO1NA  ps [ 16    0    0  -30  -30]
 re-encode 396/1056 ber 3.75e-01  Es/N0=-12.9 Eb/N0=2.6

but when I plot the symbol amplitudes there's obviously
a steady drift from a frequency offset of about -0.22 mHz,
that's enough to wrap around completely during the 5280
second message.

Restarting the decoder with that frequency offset immediately
gives

 found rank 0: VO1NA  ps [  1  180  180  180  180]
 re-encode 153/1056 ber 1.45e-01  Es/N0=-2.5 Eb/N0=13.0

so we gained 10dB just by getting on the right frequency.
220 uHz makes a big difference!

That was only possible because the signal was actually
strong enough to be visible in the symbol plot.

Been testing the decoder with 131 char messages and it
decodes 77% of messages at Eb/N0 = 0.0 dB with 20k list.
Seems reasonable so maybe there isn't a problem with
a long trellis.

--
Paul Nicholson
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