Jack wrote:
"My HF antennas consist of 3 long wires and 1 dipole suspended from and
between pine trees, all some 80 feet in the air."

I worked for years in a shortwave broadcasting plant. One building
contained 12 transmitters, 8ea. 50KW, and 4ea 100 KW, plus several lower
powered transmitters.

We had dozens of antennas which included several curtain antennas for
each of 3 frequency ranges, low, medium, and high. The curtain array
requires 4 towers for support. It has 4 dipoles in a radiating plane,
all driven in-phase. It has 4 reflecting dipoles in a parallel plane
directly behind the radiators. Height of the drive point of the array,
its midpoint, was about 1-WL, or about 165 feet as I recall. That makes
the tower height well over 300 ffeet at 6 MHz. For economy, the curtains
for a particular frequency range are hung from a double row of towers
which support curtains on both sides.

The transmission lines from nearly all antennas, curtains, rhombics, or
whatever, are brought into a cross-bar switching area so that any
transmitter can be connected to any antenna.

Transmission lines are all open-wire spaced at about 15 inches, or more,
for a 600-ohm impedance if memory serves. Where the antenna line enters
the switching area, boomerang arc gaps provide a flashover-point
opportunity, line-to-line, and line to ground.This works.

Open wires, like coax, have a high common-mode impedance. This tends to
make a gap more conducive than the transmission line. Use large ground
wires to keep inductance and resistance low. This keeps voltage drop low
and handles the kiloamps for the short period of the surge.

Best regards, Richard Harrison, KB5WZI