Thanks Paul (and Renato and Wolf!), very well!
The carrier on 5170.001250 Hz is still on the air and will run until 18
UTC.
Since it appears that you and Jacek are the only ones trying to receive
my EbNaut, i'll stay at 16K25A, just to use the better code gain.
And since the last ~ 24 hour experiment was running so well, let's try
48 hours! Maybe it leads to a 30 0 30 0 phase pattern:
f = 5170.000000 Hz
Start time: 07.Jan.2017 20:00:00 UTC
Symbol length: 64 s
Characters: 20
CRC 16
Coding 16K25A
Duration: 45h, 30m, 40s
Antenna current: ~ 225 mA
The first time i used your calculator
(http://abelian.org/ebnaut/calc.php?sndb=-63&snbws=2500&snmps=&code=16K25&sp=64&crc=16&nc=20&submit=Calculate
) to chosse the number of characters and the symbol length BEFORE the
transmission :-)
With your given RAM, how many characters can you decode in 16K25A? And
how long does the decode process take then?
These 2 day long transmissions mostly failed on 6.47 kHz, or gave poor
results. Stacked single day transmissions were a better choice. For a
50 or 75 character message on 5170 Hz we may have to use the same
technique.
I'm often thinking about the old VLF propagation graphs
https://dl.dropboxusercontent.com/u/19882028/VLF/fig_02_25a.png (what
was the original paper where it comes from?) which make more and more
sense to me! On 5170 Hz we already see a real advantage of lower QRN
relative to 8270 Hz or 6470 Hz. According to the graphs, the optimum
frequency should be arround 4 kHz because the QRN from far away is
attenuated much more whereas the poor propagation on that frequency is
not so much expressed for 'short' (1000 km) distances. And BTW, 4 is a
very nice number, isn't it!? Sooner or later someone has to do
something near 4 kHz! I would be curious to see how this band (e.g.
4270 Hz or 70 km!) behaves. I can imagine that it is the best choice,
even in summer or especially in summer!
When looking on the todays 'wideband' window (the upper one on
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html)
we can see that we are already diving below the QRN :-)
73, Stefan
Am 07.01.2017 05:09, schrieb Paul Nicholson:
Decoded '73 DK7FC' from Cumiana (Renato Romero, vlf15, 504.6km)
with constant ref phase, Eb/N0 = 0.6, S/N 16.16 dB in 11.8 uHz,
-67dB in 2.5kHz.
Very strong at Bielefeld (Wolf Buescher, vlf6, 303.8km)
Eb/N0 11.6dB, 27.17 dB in 11.8 uHz, -56.1dB in 2.5kHz,
constant reference phase.
Here, improved my decode to 3.9dB when I remembered to use the
-a option which normalises the amplitude by the average noise.
I am not seeing much day/night phase shift at any site. Some
measurements on the carrier will be the next job.
--
Paul Nicholson
--
|
|
