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Old February 17th 04, 01:49 AM
w_tom
 
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If in sandy loom, then a single ground rod may not be
sufficient. Neighborhood history will apply. Previous
lightning damage in the last ten years? If so, then the
single point ground may be expanded with more rods; spaced as
Frank suggests and to comply with NEC. Other alternatives
include looping the house with a buried bare copper wire. But
again, this is typically only required for high 'strike
frequency' locations - more a function of neighborhood
geology.

A problem with the water idea is a loose ground rod. A
ground rod must be firm in ground when installed. A loose
ground rod is not earthed. Ground rod is further compromised
if using threaded joints. Ground rod should be monolithic
until well below frost line.

If antenna is not located near to service entrance and
single point ground, then antenna may require its own earth
ground. This in addition to the coax ground. IOW either the
antenna is part of your structure and earthed at the service
entrance ground; or antenna is earthed as if a lightning
rod. If the antenna connection to earth ground is
significantly shorter than connection to service entrance,
then antenna must also have its own earth ground rod located
as directly under the antenna as possible. This so that
lightning takes a short path to earth; does not seek
alternative paths via other items such as chimney or interior
wire.

If installing for commercial broadcaster reliability, then
the inductor from center core is additional protection. But
most industry professionals say the center conductor will leak
sufficiently to the outer shield making no center conductor
connection necessary. IOW that ground block sold in Home
Depot or Radio Shack (to earth only outer shield to single
point earth ground) is more than sufficient protection for
most residences. Again, neighborhood history will apply.
Inductor adds only minor improvement; a function of local
history and other considerations.

Disconnecting to protect equipment is unreliable because
humans are not reliable. Humans are only available only 1 in
three hours - and that assumes humans are home often.
Protection must be installed virtually 24 hours every day and
must be fully sufficient even when using the equipment.
Disconnecting is just convenient extra protection made
unnecessary by properly earthing.

Again, you have soil that typically makes poor earth
grounds. This will be especially a problem if more conductive
earth lies beneath - such as limestone. Ground rod would need
be deeper to make contact with that limestone. If geology
changes beneath building, then that too can create earthing
problems. Point being the best earth ground must be the
single point earth ground.

If using multiple rods, then those rods need be connected by
buried bare copper wire. Some do this by digging a hole, then
driving ground rod into bottom of that hole. A four or six
inch plastic pipe lines the hole. Buried bare copper wire
clamps to earth ground rod AND can be inspected through that
covered plastic pipe. Integrity of that wire to rod clamp is
important.

Forget about salting the earth. Some have lined 'buried
copper wire' trench with better material such as trailings
from a steel mill. This tends to improve the transition from
buried copper wire to earth while not destroying the copper.
Tailings are a superior idea to salt since salt will leach
away before the year is gone. But most don't bother. They
simply bury the wire.

Notice the concept. The most critical and essential feature
of any protection 'system' is defined by that single point
earth ground. The quality of that earth ground and how
connections are made to that central earth ground determines
system effectiveness. Single point grounding is the most
critical component in a protection system.

wrote:
That's a slick idea, we're sandy loam and clay around here. Next
time I sink a ground rod I'll remember the water.

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