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Re: VLF: Back on 5.17 kHz / 58 km...

To: [email protected]
Subject: Re: VLF: Back on 5.17 kHz / 58 km...
From: Markus Vester <[email protected]>
Date: Mon, 2 Jan 2017 14:50:37 -0500
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> but the signal is spread across 70uHz for some reason

Similar to the Alpha's, SpecLab resets the phase of it's GPS-locked signal generators at midnight. As 86400/4000 = 21.6 is not an integer number, there was a 0.4 cycle (144°) phase step at 0 UT. The discontinuity is clearly visible on Stefan's 424 uHz grabber window. For example, 1.25 or 0.625 mHz offsets would work, but not 0.5 or 0.25 mHz.

Best 73,

-----Ursprüngliche Mitteilung-----
Von: Paul Nicholson <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Mo, 2 Jan 2017 8:21 pm
Betreff: 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
> Duration: 12h, 26m, 40s
> Antenna current: ~ 200 mA

Looks good.

Last night the carrier 2017-01-01_17:00,+44800 at 5169.99975 Hz
measured 0.135 fT but the signal is spread across 70uHz for some
reason. It may decode at Eb/N0 between 3 to 5dB, hard to say.

Allowing for perspective I tweaked the building separation
to 45m and the height of the service rooms to 3.5m to
get 412pF and effective height 13.1m. A little better but still
a long way from 480pF.

Rrad is about 160u ohms so expecting 6.3uW.

LWPC says 0.088 fT daytime and 0.124fT nighttime.

Measured: Daytime average 0.095fT, nightime 0.135fT

I wouldn't rely on either LWPC or my measurements to better than
+/-50% and that is probably generous. But it's nice to see we are
in the right ballpark.

Paul Nicholson

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