Marcus wrote:
> The equispaced lines are presumably from Loran-C Anthorn,
> their frequencies are exact multiples of 50000 / 6731 Hz.
Thanks, I was wondering about those. The tx is 155km from
here. Those sidebands might turn out to be useful markers.
Domenico wrote:
> Initial transmission at 22.00 [CET!] will contains 22
> characters at 1 s/symbol
Decoded easily: Eb/N0=7.5 ber=0.19 decode time 22 seconds
Quite a strong signal, the BPSK was actually visible on the
spectrogram!
I got no decode of the following hourly transmission with
6 chars, 3 second symbols. I did not try any time or
frequency offsets, or any impulse blanking. Seems to be
quite a lot of impulse noise, appear not related to sferics.
I suppose local interference, switching transients.
Carrier measurement:
http://abelian.org/tmp/lf151023c.gif
21dB S/N in 3.33 mHz.
Spectrum peaks at 137502.241338 Hz +/- 1uHz.
The 20:00 UT 22 char message doesn't decode when I use
137502.241338 for the frequency, so spectrum peak is
not a good guide.
Plugging 21dB and 300 seconds into the carrier measurement
on the signal calculator page
http://abelian.org/ebnaut/calc.php?sndb=22&snbws=&snmps=300&code=8K19&sp=1&L=1&nc=22&submit=Calculate
predicts Eb/N0 = 7.48 for the 22 char 1 second symbols, which
is close to the Eb/N0 = 7.5 of the actual decode.
Dropping the power by 10dB and changing to 3 seconds, 6 chars,
http://abelian.org/ebnaut/calc.php?sndb=12&snbws=&snmps=300&code=8K19&sp=3&L=1&nc=6&submit=Calculate
gives Eb/N0 of 4.14 dB which should easily decode.
So, I have some investigation to do!
--
Paul Nicholson
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