[BC] Lightning and grounded masts

[Phil Alexander]

On 12 May 2005 at 12:29, Cowboy wrote:


>  Shunt fed towers are no gaurantee, nor even a suggestion, of lightning
>  protection.
>  The slant-wire seems to be a better performer than a skirt, however, and
>  sometimes better than a traditional series fed radiator.
> 
>  Among other things.
>  Skirt fed towers generally do worse, and there is much empiracle evidence
>  to suggest that skirts are many things, but lightning protection is NOT one of them !

Cowboy,

How right you are!

IMHO, the biggest problem in this area is that many "intuitively" understand (wrongly)
that there is no problem because the tower is grounded at the base, therefore none of
the usual precautions are taken such as would be standard with a series fed tower.

As I held the blackened ammeter in my hand, the GM said, "B-b-b-but the tower is
grounded. That CAN'T happen."  Wanna bet? <g>

Whereas if it were a series fed tower, there would have been an arc gap (or gaps)
that would have limited the peak voltage to a few KV.

While a slant wire feed does reduce the voltage spike, as compared with the top
of the tower, if there is no gap at the feed point and the tower takes a direct
hit, does anyone want to speculate what happens next? <g>

Phil Alexander, CSRE 
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037




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