"Richard Harrison" wrote

Jack Painter wrote:
"An awful lot of engineers have accepted the findings already, and
specify blunt-tipped rods on new construction.:

They should specify what works.

Suppose a charged cloud arrives overhead and no lightning immediately
flashes. If the charge is positive, it attracts electrons in the earth
ond other conductors nearby. These electrons strain to reach the cloud,
runnibg through conducting bodies to get closer to the positive charges
overhead. The blanket of air insulates between the charges of opposite
polarity. The field grows faster than these charges are neutralized.
Sooner or later, the air at a high point starts to ionize (form a
conductive plazma). Then, current flow starts with a flash and a bang.
Thunder rolls as air rushes in to fill the void left by burnt
atmosphere.

Suppose that a lightning rod is at a high point beneath the positively
charged cloud as it arrives. Electrons are pulled up to its sharp point
(electrons repel each other, ao they tend to concentrate on the outside
of the rod and find the least outside opposing forces at the tip of the
rod.

To avoid corona formation, some transmitting antennas are fitted with
"corona balls" on their tips. This reduces the strain from a pointed
tip.

On a lucky day, the cloud is discharged without lightning. On an ublucky
day, your lightning rod may get pitted.

Best regards, Richard Harrison, KB5WZI


Hi Richard,

Your example of lightning was the opposite, and very rare, from the normal
occurrence of lightning which is not positive-charged. You can read about
the discovery of this rare form of positive-charged lightning at:
http://www.ee.nmt.edu/~thomas/nyt/ny...lightning.html

As a thunderstorm approaches, preceding its arrival there is a "wave" of
positively charged ions that roll over the landscape like a wave. Buildups
of these positive charged ions do gather on objects, and there is little
favoritism that describes their formation on pointy or rounded objects, they
attach to everything. Upward-flowing streamers are emitted from these
objects as a negatively charged cloud adds its powerful attraction to these
ions. This occurs from human heads, shoulders, lightning rods (of any shape)
and your so-called corona balls that offer no protection from positive-ion
streamer emission whatsoever. I would suggest that in this area, your
recollections of early lightning theory require major updating, since it
seems based in part on radio theory that never applied to lightning in the
first place, however well intentioned many engineers in that field may have
thought it so. Corona balls are examples of the antenna being in the bathtub
and not influencing lightning in the least bit. Some things persist because
people want them too, whether scientific support for them remains or not.
Now, once lightning has broken down and been divided, lessened, etc, then it
begins to take on a shape that fits in the bathtub. Be corona-ball happy
then if you like.

The junk-science of early-streamer-emission (and prevention of sufficient
formation of same to attract a stepped-leader) relies on theories that you
would find can work in the bathtub but have no relevance at all to
lightning, for you see my friend, there are indeed great differences in the
way electricity behaves when it has exponential power behind it. It would
take thousands of Charge-Transfer-Systems (the ESE models) in a single
location to effect a measurable favoritism of attracting or avoiding a
single lightning charge. Yet in the bathtub (which is a very accurate
example of how water does not behave the same as in the ocean) sized
experiments, pointed-tip objects do attract charges. Too bad lightning
doesn't actually behave that way, it would fit those classroom models so
nicely!

A good example of draining a pitifully weak thunderstorm cloud without
experiencing an actual strike, is the St Elmo's fire (and lesser but
physically noticeable yellow air-coloring and even wet skin hair standing
up) that happen on sailboats in a storm. I have experienced the latter
several times, and while lightning struck the water close around, did not
strike the mast by great luck we could say. It was NOT a grounded sail boat
(Morgan, Out Island-41) and the potential from chainplates to waterline
would have been explosive had we been struck. There is no model that I am
aware of in thirty years of reading about this, that explains why a 65'
aluminum (but ungrounded) mast alone on the water in the middle of a
thunderstorm is not struck. And the boat was never struck in countless
exposure to such storms. I add this just to allude to the fact that while we
have learned a lot more about lightning in the last twenty years than we
knew in all of history up to that time, much remains a mystery. I still
find myself out on the water in thunderstorms, and also operate a
communications station without securing during storms, so it is certainly a
field that I have a vested interest in learning more about. I probably
learned more from your brilliant explanations of lightning protection
experience than any fifty other people I have talked with. And although he
lives in a area practically void of lightning, I include Richard Clark in
this category also because he is so well versed in the annals of common
mode, transmission theory, and a very well read liberal indeed. ;-)

In case you're wondering, I have indeed added blunt-tipped lightning rods to
the roofs of my residence. But I am also quite sure that the safety factor
of impalement-avoidance is much more likely than the chances that my roof
will ever be struck, with or without lightning rods. As there are now only
four of the twelve pines which surround my home that have *not* been struck,
somehow the odds seem to be approaching me! Four HF antenna systems are
suspended or attached to three of those "virgin" trees ;-)

73,
Jack Painter
Virginia Beach Virginia