Mike & Reg,
I agree with Reg, mostly. A good 'rule of thumb' (for
me), is put in as many radials as you can before you get
sick and tired of it, then do one more. Considering that
my knees give me problems, that usually works out to ~far~
less than the 'normal' number of radials.
I don't exactly disagree with Reg about the domestic
plumbing being used for an RF ground, but there are a lot
of 'if's about that. The one 'if' that I've had a problem
with is that if the plumbing happens to be shared with
neighbors, you have a direct RF path into their house, and
their electrical appliances, and they usually know just
who's door to pound on. That may have been an isolated
occurence,
but something to keep in mind if the "pounding on the door"
happens.
What kind of wire? The 'best' wire type to use is what
ever you have the most of. And the 'best' way to tell if
there are enough radials is when there is no noticable
improvement after adding the last few that you put in. Then
put in maybe a few more just for the hell of it...
'Doc