Topband: Lightning Protection

[KN4LF, Thomas Giella]

Tom W8JI Said:  The cause of lightning discharge is the large voltage
gradient between earth and a cluster of charged moisture in the air. The
only way to remove the charge is to have an actual path between
the "cloud" and earth.

Thomas KN4LF Says:  Yes it's the large voltage gradient between the earth
and the charged moisture in the air, in other words a cloud or cumulonimbus.
You can remove the built up charge potential between cloud and earth with a
path, in other words a lightning bolt!


Tom W8JI Said: The only thing the whiskers do is create a "ball" of ozone
and  charges around the whiskers, they do not discharge the earth or the
clouds because that ion-cloud never reaches any distance from
the whiskers.

Thomas KN4LF Says: A spline ball drains excessive voltage buildup on the
object it's attached to and the immediate atmosphere near the object within
a few feet but not the earth itself. It takes more then one spline ball to
do the trick though, basically four at the top of a tower and then four more
at each successive tower section joint. This action reduces the chances of
an upward moving leader and reduces chances for a lightning strike. The
reason for the reduction and not elimination is that a nearby strike to say
an unprotected slash pine tree can still side jump to your tower, especially
if spline balls are omitted all the way to the bottom of the tower. I've
been noticing complete rainbow type arcs of spline balls being attached to
the top of new radio towers and electrical transmission line towers here in
Florida. I've contacted these people and they tell me that research info
they have received from the lightning research center here in Florida, say
this works best when it comes to reducing lightning strike frequency.


Tom W8JI Said: An airplane (where the idea came from) is different. In the
case of an airplane the movement of the plane through the charged area
"leaks charges off" and makes the plane come closer to the
potential of the air (and moisture) around the plane. It looks like part of
the sky around the airplane, so far as charges go.

Thomas KN4LF Says: They were not trying to reduce or prevent a lightning
strike to an aircraft but trying to reduce St. Elmo's Fire or plasma or
voltage buildup which creates a constant hiss of QRN on receivers and can
also damage static sensitive microchips in electronic equipment. I've
actually seen little balls of lightning or plasma roll through an aircraft
between a nose and tail covered with St. Elmo's. Aircraft per say don't get
struck by lightning like a tower but actually just fly through a cloud to
ground or cloud to air lightning bolt.


Tom W8JI Said: A tower or building can't do that, because it is earthed. It
is easy to change the charge level in something as small as an airplane, it
is virtually impossible to change the charge level of the earth or an
object connect to the earth.

Thomas KN4LF Says: A small airplane and a tower are the same thing and it
doesn't matter that the object is earthed or not. A typical earth grounded
object will still have a high resistance and inductance to lightning's fast
voltage rise time, which is why even a shunt fed tower will get hit. Tom's
description of a large mat and numerous ground rods for proper grounding is
basically correct, that's why I said in my last post that my four 1/2"
diameter 10 foot ground rods may not be enough, though actually in my
particular case my grounding system has taken lightning strikes safely to
ground this summer. The larger the bolt the less effective a particular
ground system is though.

Under normal conditions the surface of the earth has a negative charge
potential. As a cumulonimbus (thunderstorm) develops, it's base (liquid) is
negative and the earth below it becomes positive and cold lightning
discharges occur. The anvil top or ice portion of the cloud has a positive
charge and is the culprit for hot lightning discharges between it and the
negatively charged ground many miles away, aka bolt from the blue killing
someone on a sunny day.

This will be my last post on the reflector concerning this subject, as there
is nothing further that can be said. Tom and I can just respectfully
disagree with each other. When it comes to lightning and radiowave
propagation I'm a professional. Antenna's? I'm an amateur:<)

P.S. Standard disclaimer, I have no pecuniary interest or ties to the
manufacturers and sellers of spline balls.


73,
Thomas Giella, KN4LF

Plant City, FL
Grid Square- EL88wx
CQ Zone 5
ITU Zone 8

Email: kn4lf@tampabay.rr.com

KN4LF 160 Meter Amateur Radio Resources And More:
http://www.kn4lf.com

Florida Meteorological & Climatic Institute:
http://64.176.157.9/sub/fmci.htm

Giella Website Designs:
http://www.giellawoodsignandwebsitedesigns.com




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