Re: VLF: Trying the impossible, once more - received by DL0AO and DF9RB

[Markus Vester <markusvester@aol.com>]

Stefan's single character transmission was received well by DL0AO and DF9RB - guess it's ok for everyone to share the decode result now. Note that the export-data from our 31.4 uHz FFTs are slightly shorter than the sequence, producing a little SNR loss. Here are the carrier-based Eb/N0 results:

DL0AO E-W-earthloop in Amberg:
 date       dB
 12th       9.4
 13th      12.1
 14th      12.8
 sum      16.0 (three days stacked with equal weighting)
 sum      16.3 (12th down-weighted by -4.2 dB)

DF9RB urban E-probe in Vilseck:
 date       dB
 12th       3.0
 13th       2.3
 14th     (no data)
 sum      4.0  (two days with equal weighting)

The big downer for myself was that nothing at all was received here in Nuremberg. Even after stacking three days (26.7 hours total, equivalent to 10.5 uHz) and undoing the now-known PSK sequence, not the slightest peak appeared in the noise, implying a combined Eb/N0 of less than -7.5 dB. This means that at 6.47 kHz, my E-field antenna with local railway QRM is at least 24 dB worse than the DL0AO earth loop. Pretty hopeless it seems...

Next I will try to look at the nighttime 16 char transmissions in DL0AO data.

Best 73,
Markus (DF6NM)


-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>;<rd4hu@mail.ru>
Verschickt: Mi, 11. Okt 2017 17:43
Betreff: VLF: Trying the impossible, once more

Hi VLF,

The recent 1 character message on 6470 Hz was received at RN3AUS in nearly 2000 km distance, a land path, with very good Eb/N0. 4 characters would have been possible. That was a night time transmission.
Now since a few days there is a SpecLab instance 'listening' on 6470.1 Hz at RC4HAA in 2877 km distance (LO53CF) from here, configured for EbNaut reception.
The daily 16 character night time transmission is still going on, now 6 days are completed. After 4 days, there was no result at RN3AUS and obviously not at SQ5BPF.

So there is some free time for a next experiment during daytime. Stacking EbNaut messages works very well with the tool by DF6NM. So one could try to get a result over many daytime transmissions.
I have the idea to run a few more single-character transmissions. This is also a good chance for newcomers to get a first decode in EbNaut on VLF.
With some luck, RN3AUS may decode them over the day time path, as well as SQ5BPF. And with even more luck, a decode at RC4HAA?
Trying the impossible:

f = 6470.100000 Hz
Start time: 12.October.2017  06:00:00 UTC
Symbol period: 180 s
Characters: 1
CRC bits: 0
Coding 8K19A
Duration: 9h36min
Antenna current: 300 mA

73, Stefan

sum_EW_12-14w_result.png
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sum_EW_12-14w_sym.png
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