From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Wed, 24 Feb 2010 17:33:19 +0100
Thread-Topic: AW: LF: VLF_8.79 kHz_grounding systems
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Subject: RE: AW: LF: VLF_8.79 kHz_grounding systems
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Chris,

the values are measrued with antenna in resonance, so they are "ohmic".
It is the sume of all kind of losses (soil, greenery, coil) and (almost ne=
glectable) the radiation resistance.

73, Rik  ON7YD

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or=
g] namens Chris Trayner [C.Trayner@leeds.ac.uk]
Verzonden: woensdag 24 februari 2010 17:23
Aan: 'rsgb_lf_group@blacksheep.org'
Onderwerp: RE: AW: LF: VLF_8.79 kHz_grounding systems

Hi Rik and others,

Thanks for your contribution.

> if using a short vertical monopole antenna at 9kHz a ground loss of more=
 than 1000 Ohm seems quite realistic to me.
"Ground loss" at my QTH:
500kHz =3D 35 Ohm
137kHz =3D 130 Ohm

Do you mean resistance in the strict sense, i.e. the resistive component=
 of impedance; or in the rough sense, i.e. the ratio between voltage and=
 current, which is actually the modulus of impedance?

I ask because there are capacitance and capacitance-like effects in the gr=
ound. If you are looking at (in effect) a resistance in series with a capa=
citance, that could explain the 1/f effect.

Regards,
Chris G4OKW

PS - more details can be found in Keller, G.V. & Frishcknecht, F.C. / Elec=
trical Methods in Geoprospecting / Pergamon (1966). See in particular chap=
 1 - or probably skim it, as it is detailed and can get a bit boring. Pp.=
 43-55 talk about these capacitive-like effects. The size of the 'capacita=
nce' (capacitance, not its reactance!) even varies with frequency. If you=
 look at the graph on p.52 you may need to reach for a bottle of the stron=
g stuff ;-)

 -----------------------
Dr Chris Trayner
School of Electronic & Electrical Engineering,
The University of Leeds,
Leeds LS2 9JT, United Kingdom
Tel: +44 113 34 32053
Fax: +44 113 34 32032