[Lowfer] Opera over night
Garry Hess
k3siw at sbcglobal.net
Sat Dec 21 08:19:54 EST 2013
Ran the deep-search opera32 code all night and it paid off since after
WD2XES went QRT VO1NA showed up, and hung in there until near his
sunrise. No TA but it was a noisy night with storms to the South and
DK7FC was up on 474.2 kHz working WSPR. Tried to run regular opera to
compare to deep search but CPU overload wouldn't allow it (hence the
restart). Have the same Dell XP SP2 PC for a second setup and it runs
both program together fine. Go figure.
sdr-iq1, eprobe2
2013-12-21 10:38:37 VO1NA 2836km 137554.999Hz 5mHz -41.9dBOp 93% 15.7dB
2013-12-21 10:03:38 VO1NA 2836km 137554.999Hz 5mHz -39.5dBOp 99% 18.4dB
2013-12-21 09:28:37 VO1NA 2836km 137555.000Hz 3mHz -40.5dBOp 93% 18.2dB
2013-12-21 08:18:37 VO1NA 2836km 137554.998Hz 3mHz -46.3dBOp 93% 17.2dB
2013-12-21 07:43:36 VO1NA 2836km 137554.999Hz 4mHz -45.6dBOp 99% 18.7dB
2013-12-21 07:08:35 VO1NA 2836km 137554.999Hz 3mHz -38.6dBOp 93% 19.1dB
2013-12-21 06:33:36 VO1NA 2836km 137554.999Hz 2mHz -45.4dBOp 99% 18.1dB
2013-12-21 05:58:35 VO1NA 2836km 137554.999Hz 2mHz -39.6dBOp 93% 19.5dB
2013-12-21 05:23:35 VO1NA 2836km 137554.998Hz 7mHz -44.3dBOp 99% 16.9dB
2013-12-21 04:48:34 VO1NA 2836km 137554.999Hz 4mHz -43.6dBOp 93% 17.7dB
2013-12-21 04:13:34 VO1NA 2836km 137554.999Hz 5mHz -48.1dBOp 98% 17.0dB
2013-12-21 03:38:34 VO1NA 2836km 137555.001Hz 18mHz -49.9dBOp 93% 15.2dB
2013-12-21 02:58:29 WD2XES 1365km 137514.999Hz 3mHz -28.9dBOp 63% 19.4dB
2013-12-21 02:25:33 WD2XES 1365km 137514.999Hz 8mHz -32.8dBOp 100% 20.6dB
2013-12-21 01:52:39 WD2XES 1365km 137514.998Hz 4mHz -34.7dBOp 65% 16.4dB
restart
2013-12-21 01:52:39 WD2XES 1365km 137514.999Hz 2mHz -36.0dBOp 96% 20.3dB
2013-12-21 01:19:43 WD2XES 1365km 137514.999Hz 3mHz -36.3dBOp 89% 19.6dB
2013-12-21 00:46:47 WD2XES 1365km 137514.998Hz 3mHz -30.3dBOp 98% 20.8dB
2013-12-21 00:13:51 WD2XES 1365km 137514.999Hz 2mHz -28.9dBOp 99% 21.1dB
2013-12-20 23:40:55 WD2XES 1365km 137514.998Hz 3mHz -30.2dBOp 90% 20.5dB
2013-12-20 23:07:57 WD2XES 1365km 137514.999Hz 5mHz -29.4dBOp 95% 21.3dB
2013-12-20 22:35:01 WD2XES 1365km 137514.999Hz 3mHz -29.6dBOp 100% 20.9dB
On the subject of how opds works, here are some comments that may be of
interest by Markus, DF6NM, the developer:
Markus Vester
23 Feb
View Source
Andy,
yes I am using the second method. The predefined list of callsigns is
converted to prestored Opera 01 sequences, based on the protocol
description published by Guido PE1NNZ. For any 35 minute time slot, the
received signal is correlated to each of the candidates, and the winning
correlation peak is displayed if it exceeds an SNR threshold (14 dB).
There is no attempt to decode anything, and the program will never come
up with a callsign which was not in the list. In that sense it is really
only a detection tool, but it does provide more than one bit due to
unique identification (eg. 5 bits worth for 32 candidates), along with
precise frequency and time information.
Experiments with simulated incoherent signals (ie. random phase for each
dash) indicate that the correlation process in itself is about 6 dB more
sensitive than the standard 28 bit decoding. This is more or less paid
for by the reduced information content. For coherent transmissions,
another 5 or 6 db are gained by being able to sum up the real complex
amplitude rather than the power of all dashes. Loosely speaking, this
can reduce the equivalent noise bandwidth from the inverse length of a
single symbol (0.125 Hz), down to something proportional to the inverse
of the whole sequence (0.5 mHz).
Best 73,
Markus (DF6NM)
Re: [rsgb_lf_group] Re: 0p-32 correlation results online
What I am not sure about, Markus...
In your software do you actually decode the data in some way, therefore
using knowledge of the Opera signal coding OR....
Do you precode a callsign (your "precalculated templates from a limited
list of callsigns") then correlate the received data against the pattern
generated for that callsign. If this latter is the case, then really
you are decoding just one bit of infomration. The presence or absence
of a known call.
I suspect many readers hoping for an independent Opera are thinking the
first option; but your description makes me think its the latter. In
which case, its certainly not a generalised data communication protocol,
but a weak signal error corrected path checker.
Andy
G4JNT
--
73, Garry, K3SIW, EN52ta, Elgin, IL
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