Hi Paul,
Ah yes, thanks for the additional overview. That is what i expected. Low
noise does not necessariliy mean good Eb/N0. So the amplitude scaling
based on the noise voltage may even be contra-productive. So that makes
it even harder. On sub-9-kHz we can down-scale noisy nights with some
improvement on the stacking.
Maybe there is a corelation to some plot from
http://lasp.colorado.edu/space_weather/dsttemerin/dsttemerin.html ?
We are not on sub-9 kHz, so maybe 17 kHz behaves already a little bit
like LF here? Just a guess without thinking too much.
Doubling the antenna current would mean 48 kV across the wire. That is
is ok for the wire and isolators but not for the coil :-)
I would need twice as much capacity and a different coil, having half
the inductance, then i could double the current...
I hope to comple the 2 characters in <= 5 days.
73, Stefan
Am 18.12.2017 21:45, schrieb Paul Nicholson:
On 12/18/17 20:03, DK7FC wrote:
Thanks Paul for the summary.
Well, 8 days already and it gets worse. I think the phase changes are
not from my side, so it must be the path.
I think i will give up now with this 3 character message. But even a
failed attempt gives us a set of data showing the difficulties and
phase variations.
On the other side, a single character message is to short to let it
be as it is. So i'm trying a new message with just 2 characters
before going down to 5170 Hz.
If possible, i daily feedback is apprechated.
*f = 17470.1000 Hz
Start time: 18.Dec.2017 21:30:00 UTC
Symbol period: 45 s
Characters: 2
CRC bits: 14
Coding 16K21A
Duration: 09:12 [hh:mm]
Antenna current: 1.2 A*
73, Stefan
Ok with that. We're seeing several dB night to night change
in S/N and it doesn't follow the noise floor at Forest.
Relative RMS noise amplitudes in 1Hz band around the signal:
10/11 Eb/N0 = -13.1 dB, noise = 2.12
11/12 Eb/N0 = -6.3 dB, noise = 5.49
12/13 Eb/N0 = -6.8 dB, noise = 3.60
13/14 Eb/N0 = -19.6 dB, noise = 1.75 (stopped 03:40)
14/15 Eb/N0 = -6.0 dB, noise = 2.60
15/16 Eb/N0 = -11.0 dB, noise = 2.54
16/17 Eb/N0 = -14.6 dB, noise = 2.27
17/18 Eb/N0 = -9.9 dB, noise = 3.03 (stopped 04:19)
If anything, noisier nights are giving higher S/N.
Looking at NAA 24kHz, I see variations of the night phase
of up to 80 degrees.
It looks as if stacking repeated signals isn't going to
work so well at these high frequencies. At least it
would need a dB or two devoting to a pilot carrier.
You'll just have to double your antenna current Stefan!
--
Paul Nicholson
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