Bob Collis wrote:
"What measures beyond un-plugging the antenna from the equipment in the
shack is recommended to prevent damage from static and lightning
damage?"

Commercial services don`t shut down when storm clouds gather. They must
operate despite lightning crashes.

I began working in broadcast plants in 1949. None had any damage despite
frequent direct hits.

First, no lightning made it through a very important item, the tower
lighting choke. Every tower lighting wire on the tower, beacon, side
lights, and neutral has a winding on a big ceramic coil form.

The tower side of these windings must present a high impedance to the
R-F. They have no shunts to ground.

The line sides of these coils have each their bypass capacitors and
thyrite arrestors to ground. It nworks. The power line is free from
serious transients.

Towers sit on base insulators which are shunted with arc-gaps which
rarely if ever fire. Another spot gets all the action. It is the Faraday
screen between the primary and sexcondary of an air-cored R-F
transformer which couples the tower to the antenna system. The Faraday
screen is a comb-like structure of metal fingers grounded securely along
one edge. The tines protrude open-circuit into the air like a row of
soldiers. Coils share an axis on either side of this metal comb. Surface
of this Faraday screen is pock-marked like the surface of the moon. This
is where the lightning finds its way to ground.

Lightning gets an inhospitable reception by the transmitter coax too.
The inside surface of the shield and the outside surface of the inner
conductor have inductance to oppose the lightning (a common-mode
current) and these conductors are tightly coupled along their length.
Shunt capacitance couples the two surfaces too. A transient trying to
make its way down both conductors at once is stiffly rejected.. This
usually triggers a flash over. Transmitters usually have a circuit to
sense this and it momentarily kills the transmitter to prevent follow
through of an r-f arc fed by the transmitter.

Working with VHF transmitters and receivers, I found that the same
princoples used on medium wave radios worked very wel at VHF too. No
lightning damage to transistorized base stations with antennas at the
highest points for miles around.

Best regards, Richard Harrison, KB5WZI