yep--sounded like a grounding problem to me..
i recenl.ty had a satellite dish installed and
the installer would not put it in unless i had
an adequate ground rod..so we proceeded to get
a copper rod from the hardware store and pound
it 8 feet into the ground..the wire is not strong
enough to withstand pounding directly so i had
to start the proceedure by taking another heavier
rod and making a hole, then shield the rod with
a larger diameter pipe until it was nearly level
with the ground. Glad you found the solution for
your hum.... now go learn the words!