It is called the rolling ball concept and is based on the fact
that lightning travels down in approximately 150-foot (50 m)
increments known as step leaders. Basically, you roll an
imaginery ball with a radius of that distance around the tower.
Any point which is touched by the circumference can be hit.
Any point underneath this circumference and the tower is in the
96% protected zone. It is 96% because the step leader may be
somewhat less than 150' or 50 m. Also the step leader may not
follow a logical course. Lightning follows the rules of Calvinball
(comic strip Calvin & Hobbes, no longer done). Simply put, the
only rules in Calvinball is that there are no rules and they can
change at any time (kinda sorta like life itself!)
73,
Bob AA0CY
----------
From: Edward Soriano, M.D., DU1OZ, KB3CNO[SMTP:du1oz@writeme.com]
Sent: Thursday, June 25, 1998 9:20 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Protected Land Area
Hi!
My newly installed 40 foot crank up tower is more or less 280 feet away
from a 120 feet tall wood post holding a VHF omni commercial antenna.
Will this high structure protect in a way my crank-up from direct
lightning hits? or
to rephrase the question were there studies done to determine the radius
or area of a land that can be safely protected by a single high grounded
tower with lightning rod?
73 de Ed
Edward Soriano M.D., DU1OZ, KB3CNO
Philippine Islands
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