Two possibilities:

1. Try a ground plate. They have the same surface area as the rod, but you
still have to bury it. However, you will still have to find an area you can
dig a hole 1' x 1.5' x (as deep as you can get it, but deeper than 3' should
not be necessary.) How is the moisture in the earth? If it's dry, you have
yet another problem.

2. Buy a 1/2" x 10' copper pipe, thick wall. Solder on a tee (sideways) and
cap the top side, and mount a hose fitting on the perpendicular opening and
attach your garden hose. Cut the 'drilling' end of the pipe off on a slight
angle. (30 degrees?) Now, use a rubber mallet and some finesse, turn on the
water and see if you can coax it down as far as possible. If you hit a big
flat rock surface, you're buggered, but if with a little luck you might get
at least 8+ feet of it into the earth.

Good luck!

Pat