Topband: k9ay loop gnd?

[Jim Jarvis]

Folks,

Have just put up a pair of k9ay crossed loops.

Too near my power system, evidently, as I have loud
pwr line noise pickup.  Although I'm seeing SOME f/b and
f/s on the array, it's only maybe 10dB.  

I'll relocate it this next weekend, further from the power
system.  However, I'm wondering about ground system under
the loops.  Using 6' of 3/4" copper tube, into a sandy soil.
Plan to add four 10' radials to that, but not until I move
away from the power noise.

Has anyone had direct experience with sandy soils and AY loops?
Other recommendations?  

Jim n2ea