Ace, WH2T wrote:
"I realized I have to mention that I use an inductive RF coupling -
impedance transformer in my homemade transmatch in order to eliminate a
direct d-c path from the ladder line to the transceiver input."

Lightning is a threat to antennas and to items connected with them.
Static charges may build in a time of clear skies, especially ahead of a
thunderstorm. Guy-wire insulators often flashover to announce a storm
is approaching.

Radio towers in broadcast stations get lightning strikes over and over
again, but loss of equipment or even air time is minimal.

The beacon atop a tower is most exposed, but it is protected by a
vertical metal rod attached to the tower near the beacon and extending
well above it. Often this rod is an 8-ft Copperweld groundrod bolted to
the tower with its tip point skyward. Pits on the rod show it takes
hits. Beacon survival shows it does not take hits. The protection works.

Guy-wire insulators are often doubled or tripled at the tower attachment
points to discourage flashovers here.

An air gap is provided across the tower base insulator. In theory,
lightning ionizes rhe air in the gap and shunts the charge to ground
before it gets into the feeder system. Spacing is usually adjusted to
only slightly wider than the gap will breakdown on the transmitted
signal. I`ve examined many of these ball gaps and horn gaps and seen no
evidence of flashover.

To discourage lightning, a turn or two is often made in the conductor
feeding the tower. I haven`t seen pts on the balls or horn gaps
indicating that the tiny inductance added by a turn or two in the
feedwire does any good.

A static-drain choke which has a very high impedance at the operating
frequency, but has a low d-c resistance, is often connected across the
tower`s base insulator on the line side of the base impedance matching
unit. It may be placed on the tower side of the matching unit if there
is no d-c continuity through the matching unit.

All the stations I`ve worked in had an air-core 1:1 coupling transformer
in the tower matching unit. Primary and secondary share the same axis
but are seoarated by a metal rake which serves as a Faraday screen. It
is a picket fence between the coils. The tines of the rake have no
electrical connection at one end, but the backside of the rake connects
all the tines together and firmly grounds them.

The rake allows magnetic coupling between the coils but prohibits
electric field coupling between the coils. The rake is a very effective
lightning stopper. It is full of pits where lightning has struck.

Best regards, Richard Harrison, KB5WZI