[TowerTalk] N4KG: LIGHTNING STRIKE SURVEY

[force12@interserv.com]

T. A. Russell wrote:

> LIGHTNING  STRIKE  SURVEY
>
> 1 -  Have you ever taken a direct hit to either antennas or towers?

Minnesota: Yes. As best as I could tell, two times. I say both, got 
knocked onto the floor and could smell the ozone. I also watched what 
appeared to be a "cloud" of maybe zinc dust settling to the ground from the 
tower. This tower was the tallest of the two (the shorter one did not get 
hit). It was 105' and the location was the highest hill south of the Twin 
Cities.
	As a parenthetical note, I also had my gin pole draw arcs during a 
snow storm. Fortunately, I was lower than the top of the gin pole. I heard 
several "zaps" and couldn't figure out what it was. Finally looked upward 
into the snow and could see the arcs. They were several feet long. Wasn't 
sure what to do. I did climb down, but not before putting on my outer mits 
("choppers") and making sure only my boots and mitts came in contact with 
the tower. Wasn't sure how much protection the snow suit would offer. Maybe 
this is why I have so little hair.

California: Yes. I think this was a very rare occurance. Came home during a 
rain storm, looked up at the tower (as usual) and noticed an arc hit the top 
of the mast. I continued to watch and counted 15 of these small "strikes" 
within about 5 minutes. Each "strike" was about 20' long (coming from above 
to the mast). They were audible, but no thunder!

>
>
> 2 -  If YES,  was your damage
>
>         MAJOR,     MINOR,    NONE ?

Minnesota: nothing at all. All the gear was connected and the coax selector 
switch was set on bypass to ground.

California: nothing at all. All gear was connected and the coax selector 
switch was set to bypass to ground.



>
>
> 3 - How is your tower grounded?
>
>       Direct burial in ground
>
>       Concrete base with ground rods (number?   How attached?)

Minnesota: 10 copper ground rods around the base. All rods soldered to large 
braid and to each other, and attached to the tower legs using double braid. 
The base of the tower had about 5,000 feet of buried radials, approximately 
equally spaced around the base. They were tied together at the copper ground 
rod "buss."

California: Several copper ground rods attached to the tower base. Inside, 
additional ground rods through the concrete floor (rig was in a separate 
room in the garage area) and braid to the gear. All gear sitting on copper 
mesh (under plexiglass) and braid to everything.


>
>
> 4 - Are your feedlines and rotor/control cables
>
>       Above ground
>
>       At ground level
>
>       Buried

Minnesota:  The coax feedlines ran down a tower leg and then overhead to the 
house. No remote switch(es).

California:  Coax feedlines go through a remote switch at the top of tower 
and are on a single standoff at the top.



>
>
> 5 - How do you protect / isolate your radios / rotor control boxes /
> etc.
> ?
>

Nothing special in either location.




Hope this adds to the collective body of information!

Have a good day and 73,
			Tom, N6BT
			Force 12 Antennas and Systems
			(Home Page   http://www.QTH.com/force12 )



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