On Thu,1/15/2015 5:23 PM, Donald W. Kane via RFI wrote:
NEC requires minimum 6 ft. between ground electrodes..for better
performance minimum 2X electrode length (e.g. 16 ft for 8 ft rods).
The concern with rod spacing is that there is inductive coupling between
them, with reduces their combined effectiveness. Spacing equal to their
length is considered a minimum, 1.5-2X is better. The other tradeoff is
the inductance of the connecting wires, which is why 2X is probably a
practical maximum. Many years ago, I attended grounding workshop where
the teacher obsessed on ground electrode length and spacing for 4 hours,
complete with the math.
73, Jim K9YC
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