[Karlnet] lightening strikes 3 times !!!

[LaRoy McCann <lmccann@roachconveyors.com>]

To all,

I have one location where I have had a board zapped 3 times by 
lightening.  It is on a 100 ft tower with a 24db grid antenna.  Both the 
grid and antenna are mounted about 2 ft from the top of the tower. The 
antenna has a lightening arrestor on it. The tower was orginally grounded 
with a single ground rod.  The guy cables anchor with earth screws like the 
power company uses.  The board is mounted in an aluminum box.  Cat5 cable 
down into the house.

After replacing the board the 2nd time I added 2 additional ground rods to 
the tower.

Boom, crack, popped again!

It never harms the radio card, only the board.  So it has to be coming in 
from the ground side.  It never damaged anything else until this last time 
and it also got the guys switch.

I did notice the last time it climbed the tower that it appears that 
someone had painted the tower with a silver paint.  I don't know if it was 
done before of after the tower was put up.  The tower was already up when 
the current owner bought the house.

My thinking is that the paint may be keeping it from conducting thru the 
joints of the tower.  Taking the path of least resistance, it goes thru the 
board, down the cat5 to a ground some where in the house.  Normally the 
guywires will take most of the lightening to ground, but the paint is 
probably preventing that.  I plan on running a separate ground wire from 
the ground clamps at the tower base up to the top of the tower and 
terminate it to the aluminum box.

I also have 2 other installations within 7 to 10 miles from this area, both 
on 100ft towers, and no problems at all. (knock on wood)   One of these 
sites is on a tall hill where they took a lightening strike that wiped out 
other electronics such as copiers and computers, but it did nothing to the 
wireless.

Has anyone else had anything similar happen to them?

Thanks,
LaRoy

_______________________________________________
Karlnet mailing list
Karlnet@WISPNotes.com
http://lists.wispnotes.com/mailman/listinfo/karlnet