Hi ULF,
More news from the latest experiment on the 101 km band with QRB ~ 65
km.
Yesterday i have been in JN39VH41HL
again and took all the equipment of this ULF experiment home again.
Everything has still been there and in its right place, which was the
first good message. Here's an image showing the coupling of the loop
antenna, 2 turns primary and about 200 turns secondary on a big ferrite
core:
https://dl.dropboxusercontent.com/u/19882028/ULF/20161211_123535.jpg
Even the audio recording process was still running but the USB stick
was almost full. Now i have saved a 29.7 GB raw file containing the
audio data for post processing. This recording is almost 4 days long. 2
SpecLab instances are now running to produce spectrograms in 424 uHz
FFT bin width and 10 minute per pixel scroll rate, using a noise
blanker and a 4 kHz wide filter centered on 2970 Hz.
The accus (5x 7 Ah lead gel) were discharged to 12.17V,
https://dl.dropboxusercontent.com/u/19882028/ULF/20161211_123758.jpg,
so it was the right choice to use these 5 accus.
The single turn vertical loop circumference is about 45m out of 1.5mm^2
cu wire and the captured area is about 70 m^2.
Now, while writing this mail, the first pixels are coming in. So far
the result is looking very very good, the SNR seems to be arround 20
dB, much more than expected! See attachment. I will write a summary
when all the spectrograms and eventual EbNaut decodes are available.
But in the moment it looks most promising that i successfully crossed
65 km distance on the 101 km band, which was the goal. This is the path:
http://no.nonsense.ee/qth/map.html?qth=JN39VH41HL&from=jn49ik00wd
73, Stefan/DK7FC
Am 09.12.2016 15:43, schrieb DK7FC:
After doing a lot of modifications here on the TX side, the effect
still exists. I can't get rid of the unstable phase shown on the VLF
tree grabber.
One thing to mention is that the phase seems to change slowly, no
sudden phase jumps. Thus the peak is 40 dB S/N in 47 uHz. So obviously
there were much less uncorrected phase glitches than expected in the
first moment when i saw the effect.
Just to be sure i downgraded to the last SpecLab version, the one i
used since the last month. But the effect still exists.
Next to note is the i never saw the effect in my last tests. I still
have captures showing a very clear trace on 2970 Hz during the 31 km
experiment. OK that was in September. The QRN levels may have been a
bit higher and the signal was 7 dB weaker. So maybe the effect was just
hidden in the noise?
Next i found that some SpecLab configurations seem to be corrupted by
forth and back installing old (V2.90b2) and new (V2.92b2) version. So i
am now using the old version and a config file that was never opened in
the new version. It all seems to work fine on the TX side but i can
still see the effect. BTW i even disabled the NB and checked if this
makes a change. But thill the same result.
The TX schedule for the experiment is:
07.DEC: TX 2970.000 Hz (antenna current between 105...110 mA
all
the time) since 13:30 UTC. The recording has started about 15 UTC.
08.DEC: EbNaut 5ch, 80s, 8K19A @ 2970.000 Hz starting 7 UTC,
ending 18:22:40 UTC. Then, carrier at 2970.000 Hz. Some interruptions
happened in the late carrier.
09.DEC: 0 UTC starting DFCW-10800 (3h per element), 'dit' at
2969.9975 Hz, 'dah' at 2970.000 Hz. The message is 'FC'. Between F and
C there is a break of 7 hours. In this time, starting 15 UTC: EbNaut
2ch, 68s, 8K19A @2970.000 Hz.
10.DEC: End of DFCW message 'FC' at 13 UTC. Then, EbNaut 5ch,
80s, 8K19A @ 2970.000 Hz starting 13 UTC (repetition of the message of
08.DEC.)
11.DEC: End of EbNaut message at 0:22:40 UTC. Then, carrier
on
2970.000 Hz until 20 UTC. The recording will stopp in the late morning,
due to space limitations of the 32 GB USB-stick.
>From the local recording i tried to decode the 5ch EbNaut message. But
it didn't decode. I just got a '*****' message and a false decode. This
is strange. The dots are quite concentrated in the two horizontal lines
which indicates a stable phase. See attachment. Also the signal peak is
strong and narrow. But in the red field there is nothing to see... This
EbNaut message was transmitted with the new PSK config in SL. It is the
reason why i will repeat the message in the end of the experiment
again, using the old settings and version.
I should have done more pre-tests before starting the experiment. But
now it is running. Well, the main goal is to detect a clear trace of my
signal in a spectrogram running at 300 uHz or so. The signals do not
look bad on the local grabber, not at all, despite the strange
(propagation?) effect. I'm still optimistic...
73, Stefan
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