Stefan,

> Another idea would be /p earth rods but there are a lot of stones in the soil 
> so it is difficult sometimes.

We have the same problem with cave radios on 87kHz.  In some places it was 
impossible to drive a 1 metre rod, but 3 to six 30cm rods separated from one 
another by at least 60cm worked as well as the 1 m rod would have done.

73
John F5VLF