I received this from another group and have not seen an answer. Anyone care to
comment?

"Good Morning DX List:

Here is the technical question of the day. I have a 70 foot tower, shunt
fed at 31 feet with two parallel lines of #6 plastic coated copper wire. The
lines are approximately 15 inches apart. These lines tie back into the tower
at the high end with pieces of aluminum tubing around .75 in. in diameter,
and are tied together at the bottom which is the feed point. The wires are
each approximately 6" from the tower legs.

The question: Can these lines be considered as one piece of wire, and if so,
what is the combined diameter of the wire? Think back to the days when
"cages" were built to increase the effective diameter of antenna wires.

73,
Mike, W5UC