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Date: Tue, 3 Jan 2017 04:26:56 -0500
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Subject: RE: VLF: Back on 5.17 kHz / 58 km...
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Paul,

In small VLF horizontal TX antenna simulations (NEC and FEKO) I have noticed that comparatively small inclinations (10 to 15 degrees) from horizontal can in some cases make a substantial difference (5 to 10dB) in far-field signal strength. Not sure how real those NEC/FEKO simulation results are, notwithstanding best efforts on ground parameters and ground model. I guessed that your LWPC simulation of Stefan's 5170 Hz antenna had the LWPC TX antenna inclination parameter set for horizontal; and with the experimental and model results so consistent I couldn’t resist asking. 

Nice to see history in the making with the 5170 Hz tests; well done all.


Speaking of LWPC and hopes/reservations thereof: the (safe) link below provides free download of an interesting first-pass on a new type of LWPC amplitude/phase model for flares/SIDs:
http://www.ann-geophys.net/31/765/2013/
The flare-induced amplitude/phase characteristics in the above model differ somewhat from observations made in:
https://arxiv.org/abs/1603.07300
but both papers have some interesting new perspectives 

73,

Jim AA5BW
 

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson
Sent: Tuesday, January 3, 2017 3:07 AM
To: rsgb_lf_group@blacksheep.org
Subject: Re: VLF: Back on 5.17 kHz / 58 km...


Stefan wrote:

 > f = 5170.000000 Hz
 > Start time: 02.Jan.2017   17:00:00 UTC
 > Symbol length: 40 s
 > Characters: 5
 > CRC 16
 > Coding 16K25A

Received 'HELLO', BER 41.1%, constant reference phase.

Carrier Eb/N0 = +1.0 dB, S/N: 15.57 dB in 22.3 uHz,

A little weaker than expected.

S/N -64.9dB in 2.5kHz after sferic blanking.  Before the blanker, the signal measures -74.8dB after hum removal.


Markus wrote:

 > SpecLab resets the phase of it's GPS-locked signal  > generators at midnight.

Ah, that would explain it, thanks.  Now you mention it, I think we've hit that problem before but I had forgotten.

I measure a phase advance of 131 degrees at midnight.

We had better stick to frequencies that are a whole number of
cycles per day.   That also simplifies coherent stacking of
daily transmissions.

Jim wrote:

 > Was the LWPC TX antenna angle parameter fairly close to  > actual angle?

I'm not sure what you mean there.

--
Paul Nicholson
--