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Old October 19th 04, 09:35 PM
John Franklin
 
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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.

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.


We used to call em "johnny balls" at the base of the AM towers. One
station I was chief engineer of was hit constantly without any damage. NOT
fun to be in the transmitter room when lightning was hitting tho! I felt
like Dr. Frankenstein in my lab during the storms, when I had to go into the
xmitter room.

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.


A static drain choke is an EXCELLENT idea, I have used it on my ham
antennas in the past.

73
WB7FFI