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## [TowerTalk] Tower Grounding Query!

 To: [TowerTalk] Tower Grounding Query! K7NV@contesting.com (Kurt Andress) Fri, 13 Aug 1999 08:50:37 -0700
 ``` wa4dou@excite.com wrote: > SNIP > 1 )Seems likely that the shorter tower has as much probability of being hit > by lightning at either height(21 vrs. 31 ft.). and even though it will be in > the shadow of the taller tower. I've read over the years that a tower tends > to produce a cone of protection around it equal to a radius of about 2.5 > times the tower height. At 21 ft. high, is it as likely, less likely, to be > struck as the taller tower? If as likely, then i see nothing to desire in > the 21 footer and will opt for the 31 footer. Or would both be less likely > to be hit by virtue of being in the shadow of the 55 footer?( hope the > question is clear!) > Roy, At the Polyphaser seminar I attended a few years ago, it was explained that the "cone of protetction" is not really a cone. For a strike of average strength, the strike leader operates on approximately a 150' radius. The "area of protection" (region of ~ 5% chance of getting hit) can be described by rolling a 300' diameter ball along the ground. Where the ball contacts any part of a atructure, one can expect equal probability of a strike as any other similar points. Anything below the arc of the ball is considered in the protected zone. Lower than average energy strikes operate with smaller radii (reducing the protection zone), larger strikes use larger ones. I think that the prudent approach would be to give both towers the treatment. -- 73, Kurt, K7NV YagiStress - The Ultimate Software for Yagi Mechanical Design Visit http://www.freeyellow.com/members3/yagistress/ -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com Search: http://www.contesting.com/km9p/search.htm ```
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