[TowerTalk] Radials

[Rob Atkinson, K5UJ]

Medium wave bc stations routinely rely on their radial system for lighting 
protection (among other things).  A pair of electrodes with a roughly 1/2 
inch air gap is a standard component on their towers, one side bonded to the 
hot tower; the other on the base which is bonded to 4 to 6 inch wide cu 
straps going down the exposed sides of the base pier to the counterpoise 
screen and radials.   Strike energy normally travels out from the contact 
point on the surface of the soil.   In the case where the contact point is 
the tower, the radials help dissipate this energy so less goes where it is 
not wanted.  But the norm for a broadcast radial system is to have bare 
solid no. 8 copper wire buried down about 3 to 6 inches.   Whether or not 
insulated wire on the surface will do anything is something i don't know for 
sure, but my intuation tells me it is better than nothing, or a single 
ground rod (which you should have anyway).    As for radials picking up 
current from a nondirect hit, that's a risk (if it is in fact a risk) that i 
consider worth taking.
by the way, unless the surface is some kind of pavement, or rocky, the 
radials won't stay on the surface indefinitely, so at some point they will 
sink a bit below grade.  if a direct hit doesn't vaporize the wire, it will 
probably breach the insulation at least, so i doubt if it will be much of a 
barrier.

rob / k5uj


<<<Those radials are for RF, not lightning protection.

They may actually gather energy from a nearby strike
and inject it into your system!>>>

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