> Kelly and Jim-
> I'm surprised at the counter-arguments, apparently without
seeing the
> parallels.
> If I work on the stuff without a strap, I can build a
charge difference by
> my natural motion in the air or on a carpet. This can
discharge through the
> component when the distance gets short enough. ( I have
Bill,
Let me re-phrase what Jim said.
Potential difference (voltage) occurs because charges are
not uniformly or evenly distributed.
Charges have to be moved between the two OPPOSITE polarity
points in order to remove the difference in voltage. You
can't just shuffle the charges around on one conductive or
semiconductive media. You must transfer the charges to the
other object.
When you shuffle across the floor with well-insulated shoes,
you become the cloud. As you move across the room, the
electric field between you and the room causes all the
opposite charges that can move to move as near you as they
can, while similar charges move away from you.
When you ground yourself to the environment around you (the
earth and your workbench), the grounding system provides a
path between you and the opposing charges. A current briefly
flows, and then your charge distribution matches the room.
In the case of a tower, the could is the point of
concentration. The earth is a huge charge source or sink,
and charges simply move around so opposing charges collect
below the cloud. When you ground the tower to earth, you
don't do anything at all except make what already is a path
(through leakage resistances) better. There aren't hundreds
of amperes magically flowing up to nowhere, there are
milliamperes of current flowing up where it eventually
"leaks off" as corona, distributing charges out in the
direction....but NOT reaching...the cloud.
Strapping a tower to earth is like you strapping the room to
the room, or strapping you to yourself. You do absolutely
nothing except decrease resistance that allows local charge
distribution, pulled or pushed by the influence of the
nearby charged object, to have a slightly EASIER time
moving.
Strapping yourself to earth (or the bench ground) is the
equal of strapping the CLOUD to earth. Now if you could do
that, you would indeed see hundreds or thousands of amperes
of current and quickly voltage goes to zero because the
charges can freely move between earth and cloud and
equalize.
I know it is tough to swallow the myth that these fuzzy
Christmas tree decorations don't change things, and that the
current isn't hundreds of amperes (Think about power lines
with corona. Imagine if that sizzling represented hundreds
of amperes! Better, think about wooden ships and corona from
wooden masts. We are talking small amounts of current.)
I'm sure as you ground a structure better the odds of a
strike go UP, not down. I'm sure the change is so minor the
effect is lost in random noise.
NASA and other people are sure we can't discharge the cloud
without getting into real trouble. Assuming NASA and other
groups who have studied this are correct, and we can't turn
the voltage on the power supply down, what can we do?
We can make an object blunter, so the charges don't all
pile up in a point and start a streamer.
We can reduce height of a target, so other objects have more
charges pile up in them and become the concentrated area of
electric field.
We can install a taller sharper-point object close by so the
electric field concentrates there and not on our tower.
I used to do communication system work on systems that had
antennas on dozens of tall buildings near the Great Lakes.
When the weather would get nasty, corona from the antennas
would kill the receivers. The solution was the installation
of taller masts with large round balls on top, so the
charges attracted by the difference in potential between the
sky and earth would all pile up in a blunt object and not
leak off in streamers that cause radio noise.
It took me weeks of listening to nonsense about dc grounded
antennas and other nonsense before I can to my senses and
realized what was really going on.
73 Tom
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