[TowerTalk] RE: Grounding, Lightning & corona discharge
Bill Fuqua
wlfuqu00 at uky.edu
Thu Jul 29 11:36:48 EDT 2004
I have some questions, with some answers of my of my own.
1. Where does the charge come from that is being dissipated by the spiderball?
Answer: From an induced charge on the ground that is balanced by the
charge in a near by clouds.
2. How is the discharge produced?
Answer: By what is known as field ionization which requires a very
high field at the tips of the Spiderball's needles.
3. Where do the ions or free electrons that are produced by the corona
discharge go?
Answer: They can not go to ground because ground is at the same
polarity and they can't just dissipate in the air due to the fact that all
atoms in the air are neutral and if they did take on a charge they would
become ions themselves. They spread out and are attracted the opposite
polarity charge source (the cloud). The ions and free electrons produce the
conductive path for current to flow just as in a neon light. They may
produce a large cloud of charged particles around the tower effectively
making it a much bigger target than before. If a number of cosmic ray
tracks cross and produce an ionized trail thru the cloud of charged
particles around your tower, guess where the lighting will go. It will take
the more conductive path to your Siderball thru the ionization cloud around
it .
73
Bill wa4lav
4. Why do cell tower owners use spiderballs?
Answer: They are just as effective as a lightning rod. So it will not
hurt if used in place of a lightning rod unless you believe that they do
work and don't take the other lightning protection precautions.
5. These devices are "Snake Oil" just like the cell phone antennas
enhancers that you put in the battery compartments of the cell phones.
A lot of people buy into the spiderball myth after seeing a little
demonstration using a small toy VanDerGraff generator.
By adding the spider ball to the dome on the top of the generator they
demonstrate the corona and show that it will not produce a large spark as
before. However, all the salesman is doing is discharging the dome which
is insulated from the base of the VanDerGraff and the charge particles then
go to ground. This also reduces the potential (voltage) of the dome of the
VadDerGraff generator and reduces its ability to produce a large spark. A
real test would be to ground the spiderball and think of the dome of the
VanDerGraff as Thunderstorm cloud which is isolated from ground and has
a large electrical charge and large potential above ground. Then you will
still get your sparks and right to the spiderball.
73
Bill wa4lav
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