What Jim suggests is on the right track. Two improvements are: 1)
spread the ground connections over a larger area, like spacing
conventional ground rods at twice their depth, and 2) improve coupling
to earth by encasing each conductor (they need not be the usual rods,
but may be a #6 copper wire, much less expensive) in a few inches of
concrete (or a concrete like material designed with higher conductivity
than concrete) to achieve more surface contacting the ground and also to
act as a larger plate of a capacitor. Rocky ground is not a good
conductor, it is a lossy capacitor; a small area of it is not a very
good ground, but couple into it at lots of points several feet from each
other and you can significantly reduce much of the impedance to low
frequency energy like lightning strikes. Another way to look at it is
to couple, with your copper wires, to as much volume of earth as possible.
73 de WOØW
Jim Shaw wrote:
>Chuck
>Although I have it somewhere, I can't find the 'official reference' to the
>following idea. But I seem to recall the following alternative approach is
>an option for situations where a vertical ground rod is just not possible:
>
>Dig a 10 foot long horizontal trench (assuming you are using a 10 foot long
>ground rod) at the rock table level (3 or more feet down?) and lay the
>ground rod in the horizontal trench then cover and 'compact' the trench.
>For best results, dig several trenches in a hub and spoke pattern and attach
>the ground wire lead to the ends of each ground rod at the hub of the spoke.
>The idea is to ensure lots of soil contact. If you absolutely can't get it
>by going down vertically, then horizontally was the backup plan according to
>his presentation.
>
>Seems like this was presented at the most recent Pacificon by a long time
>utilities (electrical or phone - can't recall) employee who is a 'ground
>expert'. I am almost certain his call is WA6ZAP (at the time, attendees
>commented on the appropriateness of his call to the topic he was
>presenting). As I recall, he lives in the San Francisco East Bay Area
>(Concord, CA??). I suggest you contact him for ideas on how to deal with
>the situation you describe. Probably can get in touch with him via MDARC
>(Mt. Diablo Amateur Radio Club), the Pacificon sponsor.
>
> http://www.mdarc.org/
>
>
>73 de Jim WA6PX
>JGShaw@Alumni.HAAS.org
>
>
>
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