On 4/12/2012 11:26 AM, Drax Felton wrote:
> How come few houses of modern construction have lightning rods if they were
> such an important invention?
Virtually all industrial installations have them on all buildings and
distillation towers.
Where I worked *all* the buildings (except single story offices)
including new construction had them. There's over a Billion (Yes that's
with a "B")dollars of facility recently finished that has them.
When I put my 45G up about 10 years ago, nearly all
tutorials/instructions on grounding, including grounding kits suggested
that the ground cable be gently curved (dressed) away from the base of
the tower and said to avoid any sharp bends. I think they recommended a
minimum bend radius of 6 to 8 inches. I don't see that listed any more.
However, even a tiny increase in inductance should be avoided. I've
seen lightning get off a grounded tower part way down. I've seen it
jump to the guy wire and then get off after only 20 or 30 feet.
The high amperage builds a tremendous magnetic field with an opposing
EMF. Combined with the rapid rise time it quenches the current flow and
the lightning seeks an easier path, not necessarily physically shorter.
73
Roger (K8RI)
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