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Old October 19th 04, 03:15 PM
Richard Harrison
 
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CIL wrote:
"---is there anything I can do to fix this?"

Broadcasters have towers that are often struck by lightning. AM towers
sit on base insulators which makes them vulnerable to static buildup
too. Wind carries a static charge which falls out on the tower even when
no lightning is present.

The shape and positions of charged clouds are constantly changing, so
lightning strikes can come from anywhere.

The broadcaster starts his lightning protection at the tower top with a
small lightning rod extending above and beyond the beacon to take the
hit and avoid expensive repairs at the tower top.

Tower guy insulators are doubled and tripled where they connect to the
tower so that static breakdown occurs to the earth instead of at the
tower.

An air gap is installed across the base insulator to bypass a lightning
hit to earth. Often a turn or two is made in the feed to the tower. This
discourages lightning on the feedline and encourages breakdown of the
gap across the insulator.

A static drain choke is often added if needed to provide a d-c path
between the tower and the earth. It is used to bleed off charge which
might build to dangerous levels.

"Lightning elimination" is a name given to mounting a large number of
sharp points around a protected area in an attempt to drain the
atmosphere of charge. The reviews are mixed.

I`ve worked in several broadcast stations hit by lightning nearly every
time a charged cloud passed by. None ever caused significant damage. Al
of the stations had lighted towers but their tower lighting chokes kept
lightning off the a-c power source.

Berst regards, Richard Harrison, KB5WZI

 
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