Re: VLF: Transatlantic success East to West

[Markus Vester <markusvester@aol.com>]

Congratulations, great work by Mike, Stefan and Paul! I'm glad to see this happen.

Best 73,
Markus

PS: Secretly in my heart I'm hoping that one fine day we might receive a 17 kHz amateur allocation...


-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Cc: Michael Smith <mike@unixnut.net>
Verschickt: So, 10. Dez 2017 16:26
Betreff: VLF: Transatlantic success East to West

Stefan wrote:

> f = 17470.1000 Hz
> Start time: 07.Dec.2017 21:30:00 UTC
> Symbol period: 60 s
> Characters: 1
> CRC bits: 10
> Coding 16K21A

and

> I transmitted the message last night again [9th]

A good signal at Forest, VA, from the overnight transmission
9th/10th, via Mike Smith's VLF receiver at 37.35348N,79.19450W,
near Lynchburg.

Decoded 'T' with Eb/N0 = +1.5 dB, BER 42.5%, rank 9;

S/N was -36.29 dB in 1Hz;

Reference phase 120,135,120,135;

Congratulations to Stefan DK7FC and Mike KE4RJQ for the
first VLF east-to-west transatlantic message. Distance
is 6817.7 km.

This is a most significant achievement. East to west is some
20dB harder than the other direction!

You can run the decode yourself from the 'vt' file at

http://abelian.org/vlf/dk7fc.171209f4.vt

The file is 4.2 Mbyte, 2 I/Q sample pairs/second.
It was extracted from Mike's raw recording with

vtread -T2017-12-09_21:30,+34590 /data/raw-fb |
vtfilter -h bp,f=17470,w=3000 -h bs,f=16400,w=600 -h bs,f=18300,w=800 |
vtblank -a13 -d0 -t100 -v | vtmult -f 17470.1 |
vtresample -r480 |
vtresample -r2 > dk7fc.171209f4.vt

Decode with:

vtraw -oa dk7fc.171209f4.vt |
ebnaut -dp16K21A -r2 -S60 -k10 -N1 -PS15 -L800 -v -c8 -a50

This was a clean decode with no false detects to get in the
way. The signal is extremely weak but gives an unambiguous
decode.

Please CC Mike in any replies, as he is not on the RSGB
mailing list.

--
Paul Nicholson
--