[Boatanchors] Lightning protection

[Sheldon Daitch]

Unless there is another practice, Rod, as you mention, what I
have seen is a one turn loop in the copper line feed between the
tower and the antenna tuning network.

There is normally a spark gap at the base of the tower, to shunt
any lightning strikes to the ground and the one turn loop has a
slight amount of inductance to reduce the strike transfer into the
tuning house. 

Most tower tuning networks also have an inductor to ground at
the output of the antenna matching network, which normally gives
a DC ground to the tower and provides a path  for the tower
lighting circuits and if a directional array, the path across the
base insulator for the sampling line to the antenna monitor
system.

Sometimes, even the one turn loop is eliminated from the
line connecting the matching network output to the tower.
I've seen this only in high power systems, 500 kW and above,
and my guess is the thinking might be at that power level, the
voltage ratings for the components are substantial enough
that the spark gap at the base keeps the voltage low enough
as to not damage the internal components.


73

Sheldon
WA4MZZ

Revcom wrote:
> Ditto.
>
> Large loop, 2-3 turns of coax after a lightning arrestor helps too, at least 
> in broadcasting.
>
> Rod
> K0EQH
>
>   
>