[TowerTalk] Lightning Protection Question

[jimlux]

K1TTT wrote:
> Of course most of us do have 'spark gap' protection at the tower and shack
> end automatically.  Just look at all the short gap paths on so-239's that
> are typically used on baluns and switchboxes, in most cases you are looking
> at 1/4" or less from the center conductor to the case.  That pretty much
> limits the voltage difference at the ends to a couple thousand volts anyway.
> 
> 

Yeah.. but if that gap fires, the connector is (temporarily, at least) 
unusable because of the carbon track.  If the goal of the "tower" 
protection is to reduce hassle having to go an replace/repair relatively 
cheap components (e.g. $10 relays vs $1000 radios), a well designed 
static gap might take the hit, and need no attention later.

(practical note.. breakdown voltage on 1/4" gap along an insulating 
surface is typically about 5-6 kV... the rule of thumb is 1/3 the 
voltage of a free air uniform field gap of the same length, and for air 
it's 71 kV/inch (30kV/cm) in round numbers)