VO1NA 2015-11-29 8K19A 2S 5C
20:00 6.2 dB
20:30 7.0 dB
21:00 3.2 dB
21:30 1.4 dB
22:00 5.4 dB
22:30 no decode
23:00 8.7 dB
Edgar wrote:
> I had been looking at vtmatch.
vtmatch monitors a stream and does a continuous
cross correlation against the template: in other
words a matched filter.
It would be the one to use if you knew what the
message was but not the start times.
Generate a template file for vtmatch with
echo 'TNX PAUL' |
ebnaut -e -r100 -S2 -p8K19A -N8 |
awk '{print $1}' > ref.dat
Here, I've dropped to sample rate 100.
I should then be able to do something like
vtread -T2015-11-28_20:00,+8h /raw | # Get 8 hours of signal
vtfilter -h bp,f=2777,w=2 |
vtmult -f 2777 | # Mix 137777 to baseband
vtresample -r 100 | # Baseband I/Q at 100 samples/sec
vtmatch -t ref.dat > match.vt
Then
vtplot match.vt
should show a good spike whenever the message appears in that 8
hour stream. The spike should be surrounded by auto-correlation
'sidebands' which ought to be quite low compared to the peak.
For some reason it's not quite working, getting the sidebands
but no central spike, even on a simulated signal. Maybe I'm
too tired or there's a bug in vtmatch. I'll look at it again
tomorrow.
--
Paul Nicholson
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