Hello:

Expect to put up an outside antenna for listening only (30 MHz and below)

Not sure if it will an Inverted-L or just a long horiz length.

Due to the way the property is laid out, and a few other considerations, I
will have to bring the
coax from the Balun at the end of the antenna (at, or close to, ground
level) back to the house which is about 40 feet away.

The easiest thing for me is to essentially run the coax some distance below
at ground level, and directly under the active, higher, horiz length as it
goes back towards the house.

How far should/must they be separated such that the coax doesn't influence
the active horiz section of the antenna right
above it in any manner ? (listening only antenna).

(my concern I guess is that the coax shield which is grounded will act as
another element, or an artificial ground, or... ?)

Thanks,
B.