The a.c. ground acts like an antenna for me. It picks up signals induced off
the hot wire (not considering the effect of the parallel neutral wire).

Soil type makes a difference, too. I heard of a guy in the desert using an old
hot water heater filled with rock salt, its sides punctured (Using a gun? I
don't know. G), and then buried. An extension pipe provided the electrical
connection as well as a way to fill the tank with water. It then seeped salty
water which spread.

Bill, K5BY