On 15 Oct 2011, at 14:14CEST, Stefan Schäfer wrote:

> Hello Dimitris,
> 
> I think the 450 Ohm you get is mostly caused by the earth electrode 
> resistance. So if you spend e.g. 2 instead of one earth rod, maybe you can 
> get a 3 dB improvement?

The more the better up to 6 or 7 rods.
From cave radio tests we find that the earth rods need to be spaced by 2 or 
more times their depth.

John F5VLF