Read before you earth your radio.

http://www.btinternet.com/~g8yoa/qsl/pme.html

http://www.rsgb.org/emc/pdfs/leaflets/emc7protectivemultipleearthingmembers.pdf

If you live in a modern house please do not earth your radio without reading the RSGB link given above.
Protective Multiple Earthing (PME) means that your house does not have an individual earth. So if a fault occurs, even at the local transformer, then your radio could go live as it earths the whole system.
If you are unsure if your house has PME then look at the area of your meter / fuse box & look for a square within a square symbol if you see it then your house has PME.

Interesting stuff Alan. I don't have PME but then again I don't have a shack at home neither. It gives people something to think about and it gets forgotten alot!!!