[TowerTalk] Naive question about lightning protection

[Tom Rauch]

Hi Sylvan,

> Over the past couple of weeks there has been some interesting discussion
> about towers and lightning protection. However, as I recall nothing
> specific was mentioned about the difference between protecting a insulated
> versus and uninsulated tower. Is there a difference in the approach? Is an
> ungrounded insulated tower more or less prone to lightning strikes?
> 
> tnx
> sylvan

Most insulated towers are used with large radial systems. I have 
two large insulated towers, the shortest is 200 ft and the other is 
over 300 feet tall.

What I do is drive a short copper pipe near each tower leg. I bond 
the pipes into the buried radial systems terminating buss.

I bend the pipes so they parallel the legs for a short distance, and 
set the gap just beyond what the transmitter will arc.

The coaxial and lighting leads from the towers go though large 
single-layer air-insulated coils that retard the lightning and isolate 
the leads for RF (so I can feed the towers as verticals). The 
feedwires that feed the towers have a large single turn loop that 
retards lightning and a gap on the network side.

Insulated towers are no more likely to get hit than grounded towers. 
How they are grounded makes no difference in how attractive they 
are as lightning targets, although it certainly can affect the damage 
that occurs after a strike.


73, Tom W8JI
w8ji@contesting.com

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