Hi Ian

I had over 3,500 feet of radials under my HF9VX/w160.

They were buried only about 1 inch deep overall.
I used a meat cleaver and rubber mallet, placing an open eyehook
through the hanging hole on the meat cleaver.
I stretched the wire out first, then let it pass through the eyehook.
As I cut along the edge of the wire to make the hole in the ground,
the eyehook would pull it down below the surface.
The job went fairly quickly!

I used some 12 and some 14 guage insulated solid copper wire, whatever
was on sale the cheapest, hi hi.....

At the antenna base, I drove an 8 foot ground rod, allowing it to stay
above ground about 4 inches.
Each radial came up to this ground rod and made a 90 degree turn
upwards.
I used a cheap pencil flame propane blowtorch and Copper Phosphorus
Bronze brazing rods (low melting point, good adhesion to copper),
affixing each wire to the ground rod.
I then welded an insulated braided 8 guage wire to this for later
connection to the antenna.
After all the radials were in place and welded to the rod, I slipped a
3/4 inch copper pipe over the ground rod and down to the radials and
filled it with silicone caulk.
Then, using a hose I washed out the dirt under the radials around the
ground rod so that I could (after it was dry) get about a 1 inch deep
layer of silicone around the ground rod and ends of all the radials so
that the insulation was covered back about 1 inch and about 1/2 inch
above the copper pipe.

Because the HF9VX has a COIL near ground level, I cut the bottom out
of a vinyl Cylindrical flower pot and slipped this over the antenna
mount and ground rod. It was stuck into the ground about an inch or
two, down to the tops of the radials. To keep grass/weeds from
growing, I also dumped a 4lb box of rock salt into the container.
I used a PVC sleeve over the antenna mount, so the salt would not get
to the aluminum.

TTUL
Gary