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Re: [Karlnet] lightening strikes 3 times !!!

To: Karlnet Mailing List <karlnet@wispnotes.com>
Subject: Re: [Karlnet] lightening strikes 3 times !!!
From: John Tully <tully@mikrotik.com>
Reply-to: Karlnet Mailing List <karlnet@WISPNotes.com>
Date: Thu, 23 Sep 2004 17:52:32 +0300
List-post: <mailto:karlnet@WISPNotes.com>
Make sure that your antenna or unit are not the highest point on the tower. Also, you should have a grounded lighting rod on the top of the tower.

Here is a very good link on this topic. It is not going to be cheap to do it right.
http://www.tvtower.com/grounding_and_bonding.html


John
www.mikrotik.com

At 05:42 PM 9/23/2004, you wrote:
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

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