Re: VLF: A 300 char message?

[DK7FC <selberdenken@posteo.de>]

Hi Markus,

Interesting, i didn't expect such a difference.
It would be interesting to see how the Raspi with the octo-soundcard would perform at DL0AO when all 3 antennas were used. That could make the most difference on Pauls side. And maybe the noise blanker is more effective? Actually we never compared the performance of the NB of SL vs. VLFRXtools.
Our small group is to small to do everything that would be interesting. But we're working on it :-)
BTW we need a public relations department for the VLF stuff. I always think we could be way more public and generate a lot of activity, maybe even by non-amateurs.

73, Stefan


Am 15.11.2017 17:25, schrieb Markus Vester:

Attached screenshots show the unspread spectrum and the time-domain correlation for DF6NM, Nov. 12-13th. Here are Eb/N0 estimates derived from the correlation:

 date    DF6NM  DL0AO (west)

 Nov.      dB           dB

11-12    -10.1      -10.4

12-13     -8.1       -10.9

13-14     -8.8       -10.2

Obviously neither DL0AO nor DF6NM came anywhere near the decode threshold.  Paul's receiver is just awesome...

Best 73,
Markus 


-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 14. Nov 2017 13:30
Betreff: Re: VLF: A 300 char message?

Hi Paul, Stefan,

this is an impressive result!

I want to correlate the message against DL0AO and DF6NM data to see how close we may have got. However copying the result from your email produced only for 298 characters between the quotes - maybe something has been lost in email formatting? 

Best 73,
Markus (DF6NM)


-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di, 14. Nov 2017 12:06
Betreff: Re: VLF: A 300 char message?

Stefan wrote:

> f = 8270.1000 Hz
> Start time: 11.November.2017 17:00:00 UTC
> Symbol period: 6 s
> Characters: 300
> CRC bits: 16
> Coding 4K19A
> Duration: 12:13:36h

> message start delayed by 15 minutes...

Copied

"HELLO PAUL AND THE REST OF THE LF GROUP! WELL, THIS IS THE NEW
LONGEST MESSAGE TRANSMITTED ON VLF. THANKS TO ALL STATIONS WHO
PARTICIPATE IN THE EXPERIMENTS SINCE 2010! VLF IS A GREAT REAGION
IN THE RF SPECTRUM. WHO KNOWS WHAT WE WILL DEVELOP AND DISCOVER
IN THE NEXT TIME :-D 73 DE DK7FC IN JN49IK"

using combined 12th/13th and 13th/14th.

Constant reference phase, Eb/N0 = +1.7 dB, BER 21.4%, list rank 0
S/N -12.40 dB in 1Hz, -46.38 dB in 2.5kHz.

Each night:

11th/12th Eb/N0 = -4.4 dB, phase 101.5 deg, -18.50 dB in 1Hz;
12th/13th Eb/N0 = -2.0 dB, phase 92.5 deg, -16.07 dB in 1Hz;
13th/14th Eb/N0 = -0.6 dB, phase 100.6 deg, -14.73 dB in 1Hz;

Combinations
11/12 + 12/13: -0.1 dB (no decode up to 6E6 list);
12/13 + 13/14: +1.7 dB (decodes BER 21.4% rank 0);
11/12 + 13/14: +0.7 dB (decodes BER 22.6% rank 82);

All three: +2.6 dB;

--
Paul Nicholson
--