Cecil Moore wrote:
chuck wrote:
Based on that, it would seem the fairweather field can support corona
formation by itself.

Even though the fairweather current is 13 magnitudes below
the corona current?

My understanding is that a strong
electric field ionizes the air and leads
to formation of a corona. I imagine with
a sufficiently strong field, the corona
current could be in the pA range. At
least I can't imagine why not.


It occurs to me that the current due to charge redistribution could be
rather significant if numerous particles are striking the antenna in a
short time interval.

Maybe aggravated by one element of the dipole being grounded
and the other floating?

I can't comment on that, Cecil. I was
trying to keep the geometry simple with
a single vertical wire. A grounded
vertical wire in the fairweather field
will acquire a charge and charged
particles striking it should not change
the charge on it, but they will cause a
redistribution. That redistribution
doubtless produces a magnetic field as
additional charges flow to/from the earth.

It's a fascinating problem.

73,

Chuck

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chuck wrote:

Cecil Moore wrote:

chuck wrote:

Based on that, it would seem the fairweather field can support corona
formation by itself.


Even though the fairweather current is 13 magnitudes below
the corona current?


My understanding is that a strong electric field ionizes the air and
leads to formation of a corona. I imagine with a sufficiently strong
field, the corona current could be in the pA range. At least I can't
imagine why not.

Here's an exercise that might add some realism. Calculate the amount
of charge a 14 awg 40 meter dipole antenna at 35 feet would have to
accumulate in order to generate a strong enough field to cause a
corona discharge. (Arcing at the feedpoint doesn't count.)

73, ac6xg

Jim Kelley wrote:
chuck wrote:

Cecil Moore wrote:

chuck wrote:

Based on that, it would seem the fairweather field can support
corona formation by itself.


Even though the fairweather current is 13 magnitudes below
the corona current?


My understanding is that a strong electric field ionizes the air and
leads to formation of a corona. I imagine with a sufficiently strong
field, the corona current could be in the pA range. At least I can't
imagine why not.

Here's an exercise that might add some realism. Calculate the amount of
charge a 14 awg 40 meter dipole antenna at 35 feet would have to
accumulate in order to generate a strong enough field to cause a corona
discharge. (Arcing at the feedpoint doesn't count.)

73, ac6xg


OK. So you understand that it is not
necessary that a conductor be charged in
order for a corona to be formed. It
needs only to be placed in a
sufficiently strong electric field.

But if there is no external field
assumed, then the required charge on the
wire would be that which will produce
the requisite field intensity at some
chosen place on the wire.

The "pointier" the place you choose, the
smaller the necessary net charge. Any
charge on the wire will be distributed
over a real wire but concentrated where
there are sharp points.

As the radius of curvature of a "point"
on the wire, such as a dust particle
stuck to it, approaches zero, the
quantity of charge necessary to cause a
corona becomes quite small. That's about
as close as I can come to realism, Jim. ;-)

73,
Chuck

On Wed, 28 Jun 2006 17:08:03 -0700, Jim Kelley
wrote:

Calculate the amount of charge

Hi Jim,

3.3 µC (21 tera-electrons) ±3dB

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 28 Jun 2006 17:08:03 -0700, Jim Kelley
wrote:

Calculate the amount of charge

Hi Jim,

3.3 µC (21 tera-electrons) ±3dB

73's
Richard Clark, KB7QHC

Those numbers are classified!

Richard Clark wrote:
On Wed, 21 Jun 2006 17:50:31 GMT, "Tom Donaly"
wrote:


Notice how he used the Mensa Society post to destroy the discourse?


Hi Tom,

I notice past membership is one of those unprovable positive facts.


there are,
alas, people who are soft-minded enough not only to take him seriously,
but to agree with him as well.


So rare so that Cecil has to offer they support him in secret email.
Even this is about hit counts when your thumb is on the scale. ;-)


I think Roy had the right idea when
he plonked him. The rest of us should probably follow Roy's example.


What's the fun in that? Pick one point and drill down; ignore the
side topics and drill down; discard the tailored citations and drill
down. Everyone of these drillings leads to a dry hole.
win-lose (classic American competition)

And yes, Mike, busting on Cecil is one pursuit here, we will leave it
to you to judge if it is indiscriminant and across the board, or fits
to threads dominated 9:1 by your Rodney King of the antennas.

Well, sometimes dummies like me get caught up in actually thinking that
it is serious discussion. I should know better!

I would suggest that a lot of the antagonists do a little better
though. All the air goes out of an argument when they just bust on
insignificant details.

I had a fellow like that who worked for me once. He wouldn't pay much
attention to the conversation at hand. But he wanted to show he was
involved. So every once in a while he would latch on to a couple words I
was saying, and argue past me on the irrelevantly picked up point.

I guess that is okay in newsgroups. It is the sort of thing that gets
you gone in the workplace.. 8^)


I make the mistake of using these groups as a learning tool, when
perhaps they are really here as mental professional wrestling?

- 73 de Mike KB3EIA -



Gimme another baton! I broke mine!
(classic American entertainment)

73's
Richard Clark, KB7QHC

chuck wrote:
My understanding is that a strong electric field ionizes the air and
leads to formation of a corona.

Yes, but according to the references, fairweather conditions are
not a strong enough electric field to cause corona in the absence
of some other energy source.

I can't comment on that, Cecil. I was trying to keep the geometry simple
with a single vertical wire.

Well, a single vertical wire would have its ground plane grounded
so it might also build up a charge between the inner coax conductor
and outer conductor from wind-driven charged particles. But wouldn't
a ball on top reduce the possibility of corona just like it does
on other vertical antennas?
--
73, Cecil http://www.qsl.net/w5dxp

Jim Kelley wrote:
Here's an exercise that might add some realism. Calculate the amount of
charge a 14 awg 40 meter dipole antenna at 35 feet would have to
accumulate in order to generate a strong enough field to cause a corona
discharge. (Arcing at the feedpoint doesn't count.)

And make it #14 solid wire with rounded ends. I suspect the coax
connector would arc long before any corona appeared. In fact,
corona should be visible at night.
--
73, Cecil http://www.qsl.net/w5dxp

On Wed, 28 Jun 2006 22:20:24 -0400, Mike Coslo
wrote:
Well, sometimes dummies like me get caught up in actually thinking that
it is serious discussion. I should know better!

C'mon Mike, this is coy by half.

Look at the Subject line you've responded to.

How could you possibly have any fantasy of this being a lesson in
flower arranging?

Look at the Subject that drove this critique.

With fully 27 correspondents, only Cecil is churning out the
inconsequential (much different from insignificant) at a ratio of
146:8. With this having increased by nearly double the earlier
observed posting ratio of 9:1, how is you seem to have been
blind-sided? If you genuinely desire to discuss the serious topic of
the Google Hypothesis, I would suggest attention to this climbing
ratio. As a fact, it takes no more than a couple dozen words. A
response would hardly encompass half that.

Beyond that, and for entertainment's sake, I'll move on from the
Rodney King metaphor to Beat Takeshi Kitano's "Zatoichi" (or any of
the 25 earlier movies, or the 100 TV episodes).

73's
Richard Clark, KB7QHC

Cecil Moore wrote:
chuck wrote:
My understanding is that a strong electric field ionizes the air and
leads to formation of a corona.

Yes, but according to the references, fairweather conditions are
not a strong enough electric field to cause corona in the absence
of some other energy source.



That is probably based on the notion
that below a field strength of ~300
volts/meter (Paschen), voltage breakdown
in air is not possible. Fairweather
fields tend to typically be weaker than
that although 200 volts/meter is
sometimes observed.

But Paschen's number assumes parallel
plates, and not sharp electrodes, and
Llewellyn demonstrated sharp electrode
breakdown at 100 volts/meter, a strength
often found in fairweather fields.

There are many other factors that
influence electrical breakdown, such as
ionization of air by naturally occurring
radioactivity (e.g., radon, which would
be another energy source but one which
is usually present near the earth),
atmospheric pressure, etc.

So yes or no? Paschen's law says no. But
Jonassen admits that Paschen's law has
never been tested for non-parallel
electrodes of really small dimensions
and he found it doesn't hold for small
spherical electrodes at separations of a
few cm. Llewellyn reported measurements
below the predicted Paschen minimum for
sharp electrodes.



I can't comment on that, Cecil. I was trying to keep the geometry
simple with a single vertical wire.

Well, a single vertical wire would have its ground plane grounded
so it might also build up a charge between the inner coax conductor
and outer conductor from wind-driven charged particles.

I would think so. And the coax looks
like a capacitor to DC, FWIW.

But wouldn't
a ball on top reduce the possibility of corona just like it does
on other vertical antennas?

It would reduce the possibility of
corona if it has a greater radius of
curvature than whatever it replaced.

73,

Chuck


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