Andy Cowley wrote in message
As I understand it, there is nothing that can work if a direct lightening strike occurs. We are talking megavolts and thousands of amps.
Way beyond anything an amateur could build.

Sure, but for only a short duration. There is plenty the average ham
can do to reduce damage.

The best we can hope for is to dissipate charge build up on the
aerial

Useless....Not much hope in that tactic.

and ensure that there is no more than a kilovolt or so at
the input to the rig caused by the (field) effects of a nearby
strike.

Actually, I think just a run of coax itself will reduce the potential
to a few hundred volts before it gets to the rig.

A spark gap that can conduct a lightening strike would
be the size of a small truck.

A 10 gauge wire can safely conduct a lightning strike to ground. But
you must have a good low resistance connection to ground. If not, the
wire will be burnt toast.

The only way to make sure you have a working station after a
lightening strike on your aerials is to take out good insurance.

Insurance won't do any good for the existing gear. Proper setup to
avoid damage, or disconnecting is a better idea. I take strikes around
here all the time. Two were direct strikes to my mast in the last 4
years. I had no damage at all to anything, and I was sitting 15 ft
from the base of the mast both times at this puter. Didn't flinch at
all. MK