Re: VLF: PSK on 3.3 kHz by cavers

[John Rabson <john.rabson@numeo.fr>]

Using about 4W RF on 87kHz USB, we found that using an earth electrode system underground insted of a small loop gave up to 31dB stronger signal on the surface (Kingsdale Master Cave valley entrance in Yorkshire), and our best cave to surface DX was 1.5km (in the Trou Qui Souffle in the Vercors).

John F5VLF/G3PAI

Cave Radio & Electronics Group, British Cave Research Association

On 19 Jan 2011, at 23:30CET, Markus Vester wrote:

Hi Stefan, thats interesting! Any idea of what's inside that long grey tube? I would presume it's a coil wound around an iron powder or ferrite bar, kind of large loopstick. Reminds me of our recent discussion about possible long and thin high-voltage loading coils...

 

Best 73,

Markus (DF6NM)

 

From: Stefan Schäfer

Sent: Wednesday, January 19, 2011 7:14 PM

To: rsgb_lf_group@blacksheep.org

Subject: VLF: PSK on 3.3 kHz by cavers

VLF,

A friend of me, F1BKM has told me about a recent french VLF experiment
on 3.3 kHz. It seems they crossed 300m in PSK31 at 3.3 kHz.
Many photos are visible at
http://f6kcz.free.fr/Actualites/2011/Carrieres%20Fleury/Carrieres%20Fleury.htm

Looks interesting but an earth loop may be better here. But the system
is very /p!

73, Stefan/DK7FC

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