On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote:

I think the height of the object relative to it's surroundings, and
it's ability to stream mean more than anything.

Hi Mark,

There's another angle to be observed here. Globally, there is a
potential difference between earth and sky that runs to several
hundred volts per meter, with a current flow on the order of
femtoAmperes per square cM. Not much locally, but for the full
surface area of earth it is the electron conveyor belt charging the
clouds through dust migration.

At this potential and current, absolutely everything is a short
circuit that penetrates the voltage isoclines raising earth towards
the clouds.

73's
Richard Clark, KB7QHC

wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:


One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

Seems to me that the federal government has lots and lots of buildings and
would relatively inexpensively conduct definitive experiments to see what
works and what doesn't in the area of lightning protection.

So far as I know, the feds have done no such thing.

On Oct 16, 8:55*pm, "John Gilmer" wrote:
wrote in message

...
On Oct 15, 10:54 am, Ian Jackson

wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged..
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. * The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

Seems to me that the federal government has lots and lots of buildings and
would relatively inexpensively conduct definitive experiments to see what
works and what doesn't in the area of lightning protection.

So far as I know, the feds have done no such thing.

yes, they have, not that i believe everything the government has said,
but this stuff i do.

this presentation lists several reports by the navy and faa among
other agencies: http://www.docstoc.com/docs/4177489/...-Abdul-M-Mousa

the nfpa and others are quoted here, even though the author is
skeptical: http://www.straightdope.com/columns/...-strikes-again

this one again quotes the onr, nasa, and air force studies as well as
others. http://lightning-protection-institut...ct-fallacy.htm

as far as tesla's stuff, i file it with most of the other experiments
with lightning protection and prevention, if it really worked it would
be used all over the place. the only system that has stood the test
of time is the old franklin rod system, it doesn't prevent strikes,
but it does try to provide a safe route to ground besides through the
protected structure. much of the success of it depends on the quality
of the installer, mostly how well they bond the various wires and how
well they take it to ground.

John Gilmer wrote:
wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.


This is done in some HV test laboratories to avoid flashover to the
ceiling and to make the field more representative of "outdoors".. they
hang a semiconductive curtain in a horizontal plane above the apparatus
which charges up and makes what's above look less like "ground"


There's also the whole thing of surrounding a valuable structure (e.g.
ammunition storage bunker, rocket launch pad) with an array of high
towers with grounded wires from the tops of the towers. While no
guarantee that lightning won't strike elsewhere, it definitely ups the
odds of the protective structure taking the hit.

here's a pictu
http://commons.wikimedia.org/wiki/Fi...launch_pad.jpg

On Oct 16, 10:43*pm, Jim Lux wrote:
John Gilmer wrote:
wrote in message
...
On Oct 15, 10:54 am, Ian Jackson
wrote:

One reason for lightning conductors (and for grounding elevated
conductors, like radio antennas) is that it helps to stop a high
electrostatic charge from accumulating in the air immediately above
them. The intention is to PREVENT a direct lightning strike, rather than
conduct a strike to ground. Of course, if a direct strike DOES occur, an
antenna (and even a stout lightning conductor) may be seriously damaged.
--
Ian

"The only problem with that is that the charge is so quickly
replenished
that I think trying to bleed off the charge is a waste of time."

The turn of the century genius, Testla, patented some lighting protection
devices based on having an insulated "cap" at the highest object on the
protected property. * The "cap" would rise thousands of volts above the
protected structure and this would reduce the tendency of lightning to
strike.

This is done in some HV test laboratories to avoid flashover to the
ceiling and to make the field more representative of "outdoors".. they
hang a semiconductive curtain in a horizontal plane above the apparatus
which charges up and makes what's above look less like "ground"

There's also the whole thing of surrounding a valuable structure (e.g.
ammunition storage bunker, rocket launch pad) with an array of high
towers with grounded wires from the tops of the towers. *While no
guarantee that lightning won't strike elsewhere, it definitely ups the
odds of the protective structure taking the hit.

here's a pictuhttp://commons.wikimedia.org/wiki/Fi...aunch_pad.jpg- Hide quoted text -

- Show quoted text -

yeah, the nasa pads have towers and long sloped wires to try to catch
lightning also.

for hv work we mostly do it outside or in a very tall building (the
octagonal one just left of center in the top picture is open inside
and about 80' tall.
http://www.ewh.ieee.org/r1/schenecta...2007_lenox.pdf

"Richard Clark" wrote
...
On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote:

I think the height of the object relative to it's surroundings, and
it's ability to stream mean more than anything.

Hi Mark,

There's another angle to be observed here. Globally, there is a
potential difference between earth and sky that runs to several
hundred volts per meter,

The Earth has the excess of electrons. The Earth produce the electric field
about one hundred volts per meter. In a suuny day the electrons migrate up
with the heavy ions (aggregates of H2O molecukes).

with a current flow on the order of
femtoAmperes per square cM. Not much locally, but for the full
surface area of earth it is the electron conveyor belt charging the
clouds through dust migration.

This "electron conveyor belt" charge the air. Next the air becomes cooler
and the condensation take place. Clouds appear. The condensation cause the
voltage rise. All types of sparks jump.
Under clouds the electric field has the opposite direction and thousands
volts per meter.


At this potential and current, absolutely everything is a short
circuit that penetrates the voltage isoclines raising earth towards
the clouds.

The high voltagi in the clouds is lowered by the "electron conveyor belt"
and the lightning.

The "electron conveyor belt" is more effective if the Earth have many sharp
needle.
So there are the two possibilities:

1. If "The intention is to PREVENT a direct lightning strike," - many sharp
needle is used,

2. If the intention is to CATCH a direct lightning strike and conduct a
strike to ground - a polished big ball is used.
S*

In message , Szczepan Bialek
writes

"Richard Clark" wrote
.. .
On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote:

I think the height of the object relative to it's surroundings, and
it's ability to stream mean more than anything.

Hi Mark,

There's another angle to be observed here. Globally, there is a
potential difference between earth and sky that runs to several
hundred volts per meter,

The Earth has the excess of electrons. The Earth produce the electric field
about one hundred volts per meter. In a suuny day the electrons migrate up
with the heavy ions (aggregates of H2O molecukes).

with a current flow on the order of
femtoAmperes per square cM. Not much locally, but for the full
surface area of earth it is the electron conveyor belt charging the
clouds through dust migration.

This "electron conveyor belt" charge the air. Next the air becomes cooler
and the condensation take place. Clouds appear. The condensation cause the
voltage rise. All types of sparks jump.
Under clouds the electric field has the opposite direction and thousands
volts per meter.


At this potential and current, absolutely everything is a short
circuit that penetrates the voltage isoclines raising earth towards
the clouds.

The high voltagi in the clouds is lowered by the "electron conveyor belt"
and the lightning.

The "electron conveyor belt" is more effective if the Earth have many sharp
needle.
So there are the two possibilities:

1. If "The intention is to PREVENT a direct lightning strike," - many sharp
needle is used,

2. If the intention is to CATCH a direct lightning strike and conduct a
strike to ground - a polished big ball is used.
S*

In the early days of lightning conductors, I believe that the French
didn't like the nasty pointy things which the British had installed.
Instead, they decorated theirs with fancy balls at the top - with
sometimes disastrous results.
--
Ian

"Ian Jackson" wrote
...
In message , Szczepan Bialek
writes

"Richard Clark" wrote
. ..
On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote:

I think the height of the object relative to it's surroundings, and
it's ability to stream mean more than anything.

Hi Mark,

There's another angle to be observed here. Globally, there is a
potential difference between earth and sky that runs to several
hundred volts per meter,

The Earth has the excess of electrons. The Earth produce the electric
field
about one hundred volts per meter. In a suuny day the electrons migrate up
with the heavy ions (aggregates of H2O molecukes).

with a current flow on the order of
femtoAmperes per square cM. Not much locally, but for the full
surface area of earth it is the electron conveyor belt charging the
clouds through dust migration.

This "electron conveyor belt" charge the air. Next the air becomes cooler
and the condensation take place. Clouds appear. The condensation cause the
voltage rise. All types of sparks jump.
Under clouds the electric field has the opposite direction and thousands
volts per meter.


At this potential and current, absolutely everything is a short
circuit that penetrates the voltage isoclines raising earth towards
the clouds.

The high voltagi in the clouds is lowered by the "electron conveyor belt"
and the lightning.

The "electron conveyor belt" is more effective if the Earth have many
sharp
needle.
So there are the two possibilities:

1. If "The intention is to PREVENT a direct lightning strike," - many
sharp
needle is used,

2. If the intention is to CATCH a direct lightning strike and conduct a
strike to ground - a polished big ball is used.
S*

In the early days of lightning conductors, I believe that the French
didn't like the nasty pointy things which the British had installed.
Instead, they decorated theirs with fancy balls at the top - with
sometimes disastrous results.

Now everywhere are "the nasty pointy things" but most people do not know why
and if they PREVENT or CATCH.
S*

On Oct 21, 2:49*am, "Szczepan Bialek" wrote:


1. If *"The intention is to PREVENT a direct lightning strike," - many sharp
needle is used,

Good luck.

2. If the intention is to CATCH a direct lightning strike and *conduct a
strike to ground - a polished big ball is used.
S*

Good luck.

wrote
...
On Oct 21, 2:49 am, "Szczepan Bialek" wrote:


1. If "The intention is to PREVENT a direct lightning strike," - many
sharp
needle is used,

Good luck.

2. If the intention is to CATCH a direct lightning strike and conduct a
strike to ground - a polished big ball is used.
S*

Good luck.

The above apply to grounded tower.

For:
" But, is there a difference in strike rate between grounded and
ungrounded towers of the same height. I would think that the difference
would be very small, and smaller as the height gets bigger."

You wrote: "I'd rather have a grounded mast struck every 5 years with no
damage,
vs an ungrounded mast struck every 10 years that led to heavy
damage or even burned the house down.
So worrying about that is kind of silly I think, when you know
an ungrounded mast is big trouble if it ever does get hit."

The grounded tower catch the electrons in form of "electron conveyer belt"
and lightning. If the "belt" is efective enough no lightnings. All local
exces of electrons from the cloud flow without lightning. If no the
lightning appears but it is weak (the sum of electrons is the same).

The strike in the ungrouded tower is always strong.
So You are right.
S*