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[TenTec] Ground

To: <tentec@contesting.com>
Subject: [TenTec] Ground
From: rohre@arlut.utexas.edu (Stuart Rohre)
Date: Tue Aug 12 19:03:30 2003
As several have pointed out, one has to evaluate the impedance of the
bonding conductors and apply them only so far as you can still maintain a
low voltage drop between the bonded points.  Thus, it probably is not
practical to bond your barn to your house ground, if the barn is 150 feet
away.   Bonding to the neighbors house grounds is probably not good, not
knowing if he has proper grounding of all his electrical grounds.

If your tower is very remote, say 200 feet away from the shack, it likely
would have to be grounded separately from the shack in the house.   The idea
is to bond things that can be joined by wide, flat, low inductance and
resistance material, to keep overall impedance low for the wide band of
frequencies in the lightning pulse.

Someone provided the example calculation by assuming some current flow and
seeing what the voltage differential would be between two points for a
conductor you are evaluating.  Voltages that are within the clamping
capability of protectors you may install could still be a few hundred volts,
but if your chosen conductor would allow several thousand volts, you will
have damage.  You try to handle the near strikes and surges induced by them;
and direct hits are typically harder to handle for the ham shack.  There
disconnecting everything from antennas and towers when not in use, or storms
threaten, is the only other thing you can do.   A direct strike will go
where it goes.  You can bleed off charge buildup at the top of the tower,
and then at least know you have taken some protective measures.   If you
live in FL or certain other places, you probably get hit more than living in
Southern CA, where it seldom storms.  Other than move, you can only do so
much.  But taking some measures is cheap insurance, and may prove adequate.

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