Hi VLF,
After transmitting carriers for the last 5 days, there are 3 good days
to stack, the others were noisy.
The resulting SNR via start time plot for different carrier length is
attached. With some uncertainty we can say that these days the ideal
start time for the path from DL to VK7 is 17:50 UTC and the message
duration should be between 2.5...3 hours.
This evening i'm going to start an attempt for a 2 character EbNaut
message. With some luck, just 2 days, i.e. 2 stacks will be enough to
get a clear decode.
f = 17470.1000 Hz
Start time: 27.Aug.2018 17:50:00 UTC (daily)
Symbol period: 12 s
Characters: 2
CRC bits: 23
Coding 16K21A
Duration: 02:56 [hh:mm]
Antenna current: 1.2 A
73, Stefan
Am 24.08.2018 14:02, schrieb DK7FC:
Hi Edgar,
Thanks for the spectrogram showing JXN nicely! Here i'm watching NWC
but the SNR is much lower, probably due to the strong QRN we still have
in late August...
I'm going to calculate the weighting factors for the stacking based on
the noise amplitude from 18...21 UTC. And obviously it is not necessary
to transmit until 0 UTC, so i will stop an hour earlier from now on.
Your SpecLab settings are fine as they are. There is no advantage from
a shorter and wider FFT. The observed spectrum width currently allows
to display more than 2000 FFT bins centered on the TX frequency,
allowing to display enough noise arround the peak to demonstrate that
the peak is most unlikely a by-chance peak...
Thanks for last nights txt file. We can produce a first stack from the
two days. Last night is weighted by -1.3 dB. The result is attached. We
can already see a peak of 11.3 dB SNR, not unrealistic but still not
significant enough. The spectrum peak produced from the suggestion of
the Excel plot (Start 17:50 UTC, duration 2 hours) is attached as well.
It shows a higher SNR, which depends on the noise floor calculation (0
dB line). I need to work on this but anyway the peak looks good
relative to the noise already.
Another carrier will follow tonite.
73, Stefan
Am 23.08.2018 23:40, schrieb Edgar:
Hi Stefan,
Based on the past two days signal from JXN, would it improve the chance
of detecting the carrier if the "FFT window time (length)" matched the
time when the signal is at maximum?
The FFT length is now 8.847 hours. The period when JXN signal is white
is about 1.5 hours.
The FFT bin width would be wider, and a larger percentage of bins would
have a stronger signal.
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