[TowerTalk] Grounding with Polyphaser lightning arrestors

[Jim Brown]

On Tue, 07 Oct 2008 04:53:25 -0700, jimlux wrote:

>Why not put them hundreds of feet apart then?
>In lightning protection, though, you also want to minimize the length of 
>the wires to the rods (because of the R and L of the wire). And, wire is 
>expensive.

I haven't read the Polyphaser language. BUT: the fundamental reason for 
wide spacing between earth electrodes is that the mutual inductive coupling 
between them reduces their effectiveness. I've seen math developing the 
recommendations for spacing, but don't recall what those guidelnes are. 
Jim's logic is correct -- it's a compromise between inductance in the wire 
connecting the electrodes and the mutual inductance of the rods themselves. 
That's where the Polyphaser recommendations come from, and I'd bet they're 
pretty good. 

73,

Jim K9YC