[TowerTalk] Static, Lightening, and protection
w5pr at swbell.net
Tue Mar 23 18:13:53 EST 2004
For years I had a 130' tower with a beam on top on a 1 acre strip of land
almost completely surrounded by salt water on the Texas Gulf Coast. I gamma
matched it for 80/160 and had radials going into salt water in almost all
directions. It was the tallest structure in at least 20 miles. There were
many thunderstorms and I worried that it would attract a lot of lightning,
but it was never hit that I know of. The lightning preferred the salt water
> The "rules" seem to be like this:
> If you want to create "umbrella lightning repellent" protection
> the tower should be as high as possible. Roughly it will protect
> hemisphere with radius of the tower.
The more common 'rule' is that a tower will protect a circle roughly equal
to its height by attracting lightning to itself from the area.
Larger or smaller distances are claimed by some authors. The effect is
dependent on total height and the peak stroke current among other variables.
Low current strokes are known to 'sneak' in the sides and actually hit the
sides of buildings and towers instead of the top. This is because the
streamers from the ground structures are shorter and the attraction of the
opposite charges on the structure pulls the leader closer as it comes down.
High current strokes are less affected by the structures and the streamers
are much longer going up to meet the leader.
David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
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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