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 = 35 Ohm
137kHz = 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 ground. 
If you are looking at (in effect) a resistance in series with a capacitance, 
that could explain the 1/f effect. 

Regards,
Chris G4OKW

PS - more details can be found in Keller, G.V. & Frishcknecht, F.C. / 
Electrical 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 'capacitance' 
(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 strong 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