Interestingly enough, when I had a 130 foot tower on the east side of
Galveston Bay on a promontory out in the salt water, I was the highest
structure for miles. I expected to have frequent strikes, but had none
that I know of over a several year period. The lightning favored the
highly conductive salt water over the tower.
Chuck W5PR
On Tue, Aug 11, 2015 at 7:14 PM, Ed Sawyer <sawyered@earthlink.net> wrote:
> Personally, at my QTH which is prominent but not quite hill top. I have 2
> -
> 70 foot towers with 14 feet of extended steel mast. They are 150 feet
> separated. I also used to have a 60 ft tower with 10 ft of steel mast that
> is now down. The trees are generally at the 50 - 55 ft level with a couple
> of trees in the 70 - 80 ft level that are about 150 - 200 ft away from any
> tower. The ground soil in Vermont is about as bad as it gets for
> conductivity. This is significant in my opinion.
>
>
>
> I have had 5 known strikes in the 10 years I have had this station. The
> only known hit to the top of a tower was the short one that is now down.
> It
> showed top and bottom evidence with the classic vaporizing of coax for
> about
> 20 ft away from the base. This tower was ungrounded as it was a 160
> vertical with an isolated base. There was no damage to the tower other
> than
> the fried 40M feed at the top for a south facing beam and the vaporized
> coax
> at the bottom.
>
>
>
> The second strike that actually hit a tower I believe hit the tower 20 ft
> above the ground by striking my 10M yagi fixed to Europe. It fried
> virtually all stack matches on the tower but the only vaporized trail was
> the 10M coax feed which lost 20 ft or so before its charred end appeared.
> I
> saw no rotor, rotor cable, or control cable damage. When I have observed
> top of tower strikes in Texas, it was common for the entire length of
> control cable to melt to the tower or vaporize completely.
>
>
>
> The other 3 known hits have been proximity hits that either hit trees or
> the
> ground and couple significant energy to coax and control cables resulting
> in
> minor damage in the shack (blown diodes etc).
>
>
>
> My experience has been that strikes are very random and do not hit the
> eyeball reference of the highest point, at all. And amazingly are as
> likely
> to strike a nearby tree or the ground as my towers. I think if my towers
> were 200 footers or something, that would be a different kettle of fish.
> Or
> if they were in open fields without trees for a mile. But in many areas,
> the towers being 10 - 30 feet above the averaged tree canopy is not
> uncommon
> and I think we are kidding ourselves on what is going to be more likely to
> get hit in these circumstances. Personally speaking.
>
>
>
> One last thing I have noticed living in Florida, Texas, and Vermont. The
> occurrence of cloud to ground lightning in Texas and Florida is WAY more
> frequent than I observe in Vermont. Cloud to cloud is the norm here.
> Ground strikes the minority. I remember feeling the opposite in Texas and
> Florida. My suspicion is that it's a combination of storm intensity and
> ground resistivity. I think that cloud to cloud charge release is much
> more
> attract in Vermont than in states with much better average ground
> efficiency
> than here.
>
>
>
> Fascinating and extremely important topic for all of us.
>
>
>
> Ed N1UR
>
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>
>
>
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