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Re: VLF: Carrier on 3675.005 Hz / EbNaut - YES

To: [email protected]
Subject: Re: VLF: Carrier on 3675.005 Hz / EbNaut - YES
From: DK7FC <[email protected]>
Date: Sun, 13 Aug 2017 10:43:25 +0200
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Hello Markus and the DL0AO crew,

My congrats, i confirm the message is correct. That's a first message detection by radio amateurs on frequencies between 3...4 kHz over such a distance.

The phase of that best decode is quite varying. Maybe the phase between day and night is changing by more than 120 deg? That could be another reason for the unsuccessful 24 hour transmissions...
Let us produce more signals and message decodes to get more impressions from that 'new' band: I'm repeating the same message again today. Then we can compare the results and you can try stacking both transmissions. Later we can try longer stacked messages...

73, Stefan

Am 12.08.2017 23:08, schrieb Markus Vester:
It looks like we got a valid decode of Stefan's 16 hour transmission from the DL0AO cardioid antenna. 

I had also attempted an early decode from a file ending 18:12 UT. This one appeared to be even better (rank 0, +2.2 dB carrier EbN0), perhaps because it ended before the QRN increased.

We had no success with the earlier 24 h transmissions on Aug 10th and 11th, neither single days nor both stacked - surely due to much higher QRN levels than today.

BTW Each decode attempt also produced several false hits with relatively good ranking, so a longer CRC might be preferable.

All the best,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Fr, 11. Aug 2017 15:32
Betreff: Re: VLF: Carrier on 3675.005 Hz / EbNaut

...looks like there was no decode from DL0AO from that transmission. It was one of the noisiest days again. I already expected that result and repeated the same message again, running today (24 hours, ending 0 UTC). With Markus' tool to stack the resulting files, they could gain 3 dB by stacking these two transmissions.
Today the noise is much lower. Attached is a RDF spectrogram showing the BPSK as recveived on the tree.

I'm announcing another test, again trying 3 characters, even in a shorter time, avoiding the night time where the SNR is much lower:

f = 3675.005000 Hz
Start time: 12.August.2017  04:00:00 UTC
Symbol period: 80 s
Characters: 3
CRC bits: 7
Coding 16K21A
Duration: 16h
Antenna current: 160 mA

73, Stefan

Am 09.08.2017 16:48, schrieb DK7FC:

An attempt for a first message transfer between radio amateurs in the range 3...4 kHz for an expected distance of 226 km, or 2.77 wavelengths:

f = 3675.005000 Hz
Start time: 10.August.2017  00:00:00 UTC
Symbol period: 120 s
Characters: 3
CRC bits: 7
Coding 16K21A
Duration: 24h
Antenna current: 160 mA

73, Stefan

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