Re: VLF: 300 mA on 6470 Hz - 1 char decoded at DF6NM

[Markus Vester <markusvester@aol.com>]

Hi Stefan,

thank you for the daytime message. Excellent decodes from both DL0AO antennas but nil here in Nuernberg. This is more like what I had expected.

Best "73",
Markus


-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 6. Okt 2017 12:55
Betreff: Re: VLF: 300 mA on 6470 Hz - 1 char decoded at DF6NM

Hello Markus,

I saw that the night time SNR was much worse than day time SNR. But i would expect that it should work anyway with just 1 character. Maybe there is an error somewhere in the recording or so? Or maybe the phase is doing strange things during the night!

I can send you a 2 character message this afternoon. But 16 UTC the next 16 character message starts. So let's try
f = 6470.005000 Hz
Start time: 06.October.2017  11:00:00 UTC
Symbol period: 20 s
Characters: 2
CRC bits: 8
Coding 16K21A
Duration: 3h33min20sec
Antenna current: 300 mA

73, Stefan

Am 06.10.2017 12:00, schrieb Markus Vester:

Despite truncated data from a 31 uHz instance and severe railroad QRM, I happened to get a correct constant-phase decode from my home antenna.

Best 73,
Markus


-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 6. Okt 2017 11:00
Betreff: Re: VLF: 300 mA on 6470 Hz - 1 char not decoded at DL0AO

Unfortunately the 1-character message was not decoded correctly from DL0AO data. The prior carrier had been well visible during the day, but completely drowned in nighttime QRN. Would you perhaps like to try another short EbNaut message in daylight?

Best 73,
Markus



-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 4. Okt 2017 11:52
Betreff: Re: VLF: 300 mA on 6470 Hz

Hi Paul,

Am 04.10.2017 11:07, schrieb Paul Nicholson:

You may as well use 8K19A or even 4K15A.

If you look at the big table at the end of

 http://abelian.org/ebnaut/ops.shtml

you can see there's no further improvement in success
rate for 6 bit payloads (1 char plus zero CRC = 6 bits).

The reason appears to be the payload is simply not long
enough to make full use of the longer constraint lengths.

OK, so i'm changing to:

f = 6470.005000 Hz
Start time: 04.October.2017  17:00:00 UTC
Symbol period: 240 s
Characters: 1
CRC bits: 0
Coding 8K19A
Duration: 12h48min
Antenna current: 300 mA

For some reason, the signal last night was about 6dB weaker.

Interesting. And for some reason, the signal was much stronger last night at SQ5BPF. Did you see it? What could be the reason? Just the noise blanker / background QRN?
The message will give you/us and 3rd impression about SNR and phase. A 10 deg phase variation between last night and the night before seems already to be quite high, relative to what we observed at 8270. Maybe we will learn a bit about propagation by that.
The 1 char message is for Jacek mainly. The chance for a decode will be high i think. Then i thought i try another (daily) 12 char message for Jacek before we can try the 100 char message. We've already done quite much on that 46 km band, so i wouldn't spend to much time there, 2 weeks maybe. Then QSY to 58 km where we can stretch the record list a bit by transferring 100 chars to you Paul.

73, Stefan

dl0ao_EW10061109-log.txt
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dl0ao_W10061113-log.txt
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df6nm_10061046-log_false.txt
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