Hello Paul, Mike, VLF,
What an exciting achievement. My congrats to Mike for his sensitive
well working VLF RX. I guess it is his best DX of a man made signal :-)
Also big thanks to Paul, without his contribution we woudn't be there
now, apart from all the software tools! It is always a cooperative
success! That's what we need in this world!
What next?
A longer message should be tried. Since i'd like to continue on 5170 Hz
with RN3AUS, i just try a 3 character message next on 17470.1 Hz. I'll
stay at 16K21A, so that people with an older PC also have a chance to
decode the message.
When east-to-west is 20 dB harder than the other direction, how far
could we go towards the east? Does someone from JAPAN read this
email and likes to try a serious attempt to detect a short message over
the 9000 km land path?
And what about stations in VK or/and ZL? There is no
impossible and this is a total new territory for us. There is a lot to
discover.
BTW i am in contact with UA0SNV. Yesterday he told me he was outside
and installed a 120m long wire while it was -30 C outside :-) Heroic!
Currently i'm playing a bit in QRSS-600, see the grabbers. If someone
likes to detect it...
For tonite i would start the new 3 charcter message on the TA path.
With 3 good days we could make it!:
f = 17470.1000 Hz
Start time: 10.Dec.2017 22:00:00 UTC
Symbol period: 40 s
Characters: 3
CRC bits: 16
Coding 16K21A
Duration: 09:36 [hh:mm]
Antenna current: 1.2 A
73, Stefan
Am 10.12.2017 16:22, schrieb Paul Nicholson:
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
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