Topband: Feeding a Base Insulated Tower

[Tom W8JI]

>I have a couple questions I have never been able to find any direct answer 
>for...  so... out of curiosity...
>
> 1:  I have never found or read any information concerning the best way to 
> feed a base insulated tower.  Is it better to just feed one leg from the 
> matching network or would it be better to feed all three tower legs at the 
> same time... OR... does it even make any difference at all?  Any out there 
> that have tried both ways?
>

I've had a dozen or so series fed towers since 1970. Except for the wire 
length and size from the tower to the matching network, it makes very little 
difference how you feed the bottom.

> 2:  Also..Now there is a static bleed choke across only one leg insulator 
> of the vertical... Is it better with one on each leg across the base 
> insulators?  (each leg is insulated with T10 Garolite solid rod type 
> insulators about 18 in long and milled to fit the Rohn 25 tower legs..  4 
> in. insulated gap left between the upper tower and lower 2ft of tower left 
> out of concrete base.)
> _________________

It makes zero difference.

The static drain can be in the house, at the tower, a resistor, a choke, or 
whatever. All that matters is you have some dc path to ground to prevent 
charging. The charging causes a tic or arc when the voltage exceeds 
insulation at some point.

The dc current is typically in very low microamperes as a storm approaches, 
or the conditions are right (I've measured it several times), but can range 
up to very low milliamperes in severe stuff. The transients from nearby 
strikes can be amperes, but the slew rate is so high they will not go 
through a choke or resistor anyway. Reducing any voltage from close 
discharges takes a close gap or a low impedance RF path.

73 Tom