[BC] Lightning and grounded masts

[Cowboy]

On Wednesday 11 May 2005 20:59, Clive Warner wrote:
> > Actually, Grounded towers don't do much better. It seems that when the
>
> charge
>
> > travels down the tower to ground, it induces voltage in the outrigger
>
> wires.
>
> > -D
>
> Well, let's see if I can put some figures to that assertion.

 And you did quite well, with one criticle error.....

 And it is....

> The mast end is earthed,

 It may appear grounded at visual observation of the obvious, but it is
 some number of degrees, and some turns ratio above ground, and
 therefore your voltage calculation is actually in series with, and additive
 to, the lightning voltage at that point on the tower, stepped up by the
 transformer effects of transmission line theory !

 ONE end of the tower is grounded, but that's not even ( electricly ) close to where
 the shunt tap is located.

 In all my years, dating back to a casual conversation with Mr. Franklin
 one stormy afternoon in Philly, the Congressman agreed that this was not intuitive,
 and tried to use that as a basis to sell me one of his "Franklin Rods" !
 ;-)

 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.

On Wednesday 11 May 2005 12:41, DANA PUOPOLO wrote:
> Actually, Grounded towers don't do much better. It seems that when the
> charge travels down the tower to ground, it induces voltage in the
> outrigger wires.

 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 !

 In my eons of experience, bottle brush disipators do appear to work, and I generally
 install them immediately below the Franklin Rods !