|To:||Tom Champlin <email@example.com>, firstname.lastname@example.org|
|Subject:||Re: [TowerTalk] Static, Lightening, and protection|
|From:||Doug Renwick <email@example.com>|
|Date:||Mon, 22 Mar 2004 09:10:26 -0600|
Theory is only theory and a starting point for an investigation. Experience is the dominating factor. Tom's experience is opposite to what my experience has been. First I live in an open space and my towers are the highest structure around. Second I have never had any lightning damage in 27 years. My towers are over 100 ft and I purposely make sure the mast extends well above the tower and antennas. The top of the mast is capped to a rounded point and may contain a porcupine. My towers are only grounded below and through the concrete base to 2 ground rods installed before the concrete was poured and attached to the tower legs. I get a lot of static discharge from only my largest tower/array and a wonderful 'cone of protection' for everything around. Somewhere else this may not work. But it sure works here and saves a lot of money and work putting in an elaborate lightning protection system which may or may not be necessary.
Tom Champlin wrote:
No one can predict what lightning will do, regardless of whatever protective mechanism is used, or regardless of the theoretical prowess of the designer. I have observed many hams who have a yagi above their tower, but do not have the 20 foot 2 meter shaft above the yagi who have never had any lightning problems. I also know hams who did have this big lightning rod above their yagi who lost the whole station. After personally inspecting such an installation that had just been hit, I decided to never have anything above the yagi except maybe 5' of mast for the truss. In 13 years, I have never had a hit. I do use heavy solid copper radials and 3 ground rods under the tower to help dissipate a strike should one occur. I also use the Polyphasor coax lightning arrestor which may be of some value.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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