That's an encouraging comment. I will be installing a tower here soon,
and since I live on a rocky hillside and have never been able to drive a
rod any deeper than three or four feet before hitting granite I was
planning to lay out several ground wires radially in however deep a
trench I could manage. I had been thinking of using two or three #4
copper wires for each leg of the tower, but I noticed that 1/2 inch
copper refrigerator tubing is not much more expensive (maybe 20%) per
foot. I roughly calculated the cross sectional area of copper for the
tubing versus the wire and it is approximately the same so the parity in
cost is understandable, but it seems to me that the tubing would make
more sense for lightning protection. Is that an incorrect perception on
my part?
Dave AB7E
Jim Brown wrote:
> On Sat, 21 Jul 2007 22:52:18 -0400, Roger (K8RI) wrote:
>
> While we're discussing the path to ground for lightning, remember
> that the energy in lightning has a broad (several octaves wide) peak
> around 1 MHz, NOT at DC. Resistance to earth of a typical ground rod
> is on the order of tens of ohms, in addition the inductance of any
> wires in between. A good radial system is likely to have a lower
> (capacitive) impedance to earth than that at 1 MHz.
>
> A wire connection the earth electrode certainly serves to minimize
> charge buildup, but most of the fast transient that is lightning is
> likely to be carried by the radial system, not the ground rods.
>
> Jim Brown K9YC
>
>
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