Message-ID: <5A382C6B.9010202@posteo.de>
Date: Mon, 18 Dec 2017 22:00:27 +0100
From: DK7FC <selberdenken@posteo.de>
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To: rsgb_lf_group@blacksheep.org
CC: Mike Smith <michael.smith20@gmail.com>
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In-Reply-To: <3b563c9c-53bc-4cb8-b31d-991856d17d9f@abelian.org>
Subject: Re: VLF: Transatlantic success East to West
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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
> -- 
>
>