Dear Horst,

Thanks for your post.

> As RX-Antenna for 136 kHz it is not too bad.
> On 500 kHz it does not really work.

Such earth-loop antennas are more or less standard for cave radio. (AFAIK, this 
started when Rob Gill G8DSU decided to try them at a Cave Radio and Electronics 
Group field meeting, and they proved far better than wire loops. The Cave 
Rescue groups later adopted them.) Cave radio is possibly near-field induction, 
but we we using it in north England many years ago and suddenly heard Finbar 
O'Connor on 73kHz from Ireland. Earth spikes certainly can make good antennas.

73,
Chris G4OKW

-----------------------
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