If you want to read more about experiences with lightning, read on. If you
are tired of the thread, hit the delete key. I have two stories to tell.
In the early 1960s (around 1963 or 1964) I was young and ignorant about
lightning but now I am not so young. I did a field day from my
grandfather's camp house along with two friends, K5ZJK (now NX7K) and K5DEG
(ex. VP2VM and now KV5S). My grandfather's camp house was in the Piney
Woods Forest in East Texas near Roganville, TX. and was surrounded by a
dense growth of pine trees. We borrowed an AC generator, put a windom
antenna in the pine trees and set up on a large screened porch in the front
of the house.
The screened porch used copper screening that covered three sides. The
windom antenna was made from #10 solid copper pulled up into some 70 foot
high pine trees. Since I was young and poor, I used two military insulators
that were given me by a ham stationed nearby at Fort Polk, LA. These
insulators were quite large and about 18 inches long. A windom antenna is a
flat-top antenna fed off-center with a random length wire. We also used #10
solid copper wire as the lead-in wire and routed it through a tiny hole at
the base of the copper porch screening. The Field Day effort went well and
we had a lot of fun. When we shutdown, we removed the equipment, returned
the generator, but we left the antenna.
A few weeks later, my grandfather called me on the phone and said come to
the camp house immediately. He said that someone had broken in and done a
lot of damage to it and he was calling the sheriff. When I arrived the law
was already there looking around. The first thing I noticed was that the
screen porch door had been ripped from its hinges and was laying about 50
feet away from the porch. Then I noticed that the lead-in #10 copper wire
was missing, but the horizonal part of the antenna was still in the air.
However there were many short pieces of #10 copper wire laying in the yard.
Each piece was about 18 inches long and both ends were rounded off implying
it had overheated at that point. When I pointed this out to the sheriff, he
and I agreed that lightning had been the cause of the damage and he left.
I lowered the ends of the windom and I noticed where one of the big
military insulators was charred from a flashover. I was obvious then that
the lightning struck the top of a pine tree, jumped the big insulator, and
followed the windom antenna lead-in to the camp house.
I looked closer to the camp house screen porch and noticed that around the
base of the screening there were a series of large burned holes and these
holes were all spaced about 18 inches apart. It was interesting that both
the lead-in and the screen porch had "hot spots" spaced about 18 inches
apart where melting occured. There was obviously some kind of frequency
cycle occuring at linear spacings during the lightning strike. When the
strike passed the discontinuity of the porch screen door, it blew it from
its hinges to a spot about 50 feet away from the camp house. The only other
odd thing I noticed was that after the strike you could see all the nail
heads through the paint covering on all the south walls of the camphouse.
You couldn't see that before. The pine tree that was struck was on the
south side of the camp house and the horizonal part of the windom stretched
across the top of the camp house.
Story number two is shorter:
Twenty years ago, I lived in Alvin, TX on the Texas Gulf Coast. The ground
conductivity there was absolutely terrific and I had great success with
phased guy wire verticals and a shunt fed tower. I never had any radials on
any of the verticals but I did use a single ground rod on each. For the
shunt fed tower I had three ground rods installed in the bottom of the
tower base hole that were directly attached to the tower legs.
The tower took many direct hits on the tower that were witnessed by my
neighbors but never did any damage to my equipment to speak of. If the
station wasn't in use, I always had the coax disconnected in the shack and
the common distribution panel was grounded. No problems with this set-up
other than losing a Ham-m control box meter once.
Then along came 2 meters and I had to put a vertical up on that band. I
made a coaxial vertical out of a long piece of coax and pulled it up at an
angle to near the top of the tower. It was insulated from the tower because
I didn't want to effect the shunt feeding on 160M. Later, I added a 4
element sidemount for 2 meter antenna and I forgot about the coaxial
vertical hanging up there. It was the only antenna that DID NOT have its
coax routed down the inside of the tower. When I stopped using that antenna
I coiled the end of its coax up and stuck it under an easy chair in the ham
shack to get it out of the way. It stayed there for many years.
Imagine my surprise in 1981 when I was preparing to move to New York and I
moved that easy chair. Under it was a large burn spot in the carpet where
the coax was coiled. The burn spot was about a foot across and I had never
noticed it for all those years nor did I have any idea when it happened. We
may have come close to a real disaster without knowing it. I want to repeat
that this was the only antenna that didn't have its coax routed down inside
the towers and wasn't grounded to a distribution panel in the shack.
I hope you enjoyed my stories.
73, Richard
K5NA@BGA.COM
http://www.realtime.net/~k5na
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