Richard wrote:
I want to put up a "long wire" with the feedpoint at one of the back end
corners of the garden. I need a good RF ground.

If I got a length of 6 foot wide copper sheet and made out of it a
cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards
position
in the ground, the top level with the surface, would that be a good idea
for
trying to acheive a decent RF ground? Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it? Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

Would I still benefit from some radials in the ground?

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky
and a bit sandyish at about 9 inches or so from the surface.TIA.

That might be overkill.. Why not spend the money on a spool of copper
wire and lay radials. For RF purposes, large area of coverage is more
important than low impedance at a particular point. You want to improve
the apparent conductivity of the soil over as much volume as you can.
Think of your grounding system as (partially) a big leaky capacitor to
"the earth".. you want to spread the RF current out over as large an
area as possible, and radials are probably the easiest way to do it.
There's nothing special about how you lay the radials or their length
(they're in dirt, so they're not tuned or resonant.. just wires).