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

[Paul Nicholson <vlf0403@abelian.org>]

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
--