Re: VLF: 15 characters on the 67 km band...

[Markus Vester <markusvester@aol.com>]

Today I finally managed to decode Stefan's 15 character transmission, using DL0AO data from four days, September 10 to 13. This was quite a challenge...

Two tail ends were missing, due to a TX modulation failure on Monday 12:56 UT, and lost data since Wednesday 12 UT due to a forced reboot of the RX PC.

To make use of all available SNR, it was necessary to include both available channels (West cardioid and East-West earth loop), which is equivalent to a weighted sum of E- and H-field antennas. The complex antenna weighting factor had to be optimized separately for each day. Then the four days were again optimally weighted and summed up.

Using the known message, SNR contributions from the four days could be evaluated separately:

     day              Eb/N0
                     dB    power
Sun  0910   -6.21   0.239 
Mon  0911   -6.01   0.251
Tue  0912   -2.98   0.502
Wed 0913   -5.13   0.307
stacked      +0.97   1.250

Stefan, thank you for this message!

Best 73,
Markus (DF6NM)



-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 12. Sept 2017 14:01
Betreff: Re: VLF: 15 charaters on the 67 km band...

I'd like to shorten that transmission experiment a bit. For a decode from Paul or Jacek it may take 2 weeks of daily transmissions. DL0AO however will likely get a decode today, if all works well. After the decode from DL0AO i'd like to stop the test because my new stacked coil is already completed, at least it allows a transmission on 8270 Hz. My larger 3 layer coil allows 700 mA antenna current, the new one allows just 300 mA, i.e. -7.4 dB. Anyway i'd like to test that new coil for the first time. I intend to run DFCW-60000 near 8270.005 Hz. This will allow to see a trace in a 47 uHz spectrogram, for Mike and Luis and DL0AO and maybe even a few more stations. Each 'dit' will take 16 hours.
I'll start in the end of the week but for the newcomers it would make sense to start a RX spectrogram a few days earlier.
An announcement of the carrier transmission will follow during the week...

73, Stefan

PS: Markus, if you can decode the message, you can tell it, it's no secret.

Am 09.09.2017 20:27, schrieb DK7FC:

VLF,

Another EbNaut message which is even more challenging to decode:

f = 4470.005000 Hz
Start time: 10.September.2017  05:00:00 UTC (daily repetition)
Symbol period: 20 s
Characters: 15
CRC bits: 14
Coding 16K21A
Duration: 11h01min20sec
Antenna current: 155 mA

Markus, if you decode it (after stacking 2...3 days), pse don't tell the message here (but your decode details pse). It will be interesting to see if Paul can get it too. Paul, will you try? Or are you still testing the E field antenna?

73, Stefan

dl0ao_sum_W_EW_result.png
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