Dave wrote:

"Ed" wrote in message
. 192.196...


If you're talking lightning, you're talking RF!

73, Roger


Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?

lightning has MANY frequencies from DC to many MHz.


DC to daylight in fact. Well, light at least. 8^)

- 73 de Mike N3LI -

On Fri, 25 Sep 2009 09:28:46 -0400, Michael Coslo
wrote:

lightning has MANY frequencies from DC to many MHz.


DC to daylight in fact. Well, light at least. 8^)

And all this radiation happens because of a severe lack of
equilibrium.

Art can't fool Mother Nature.

73's
Richard Clark, KB7QHC

If you're not convinced after reading the responses, turn on your
radio the next time a lightning storm is anywhere nearby -- or for
that matter, anywhere within skip propagation range. Then explain how
it is your radio is hearing DC.

Roy Lewallen, W7EL


I think we're arguing semantics on this. I spoke in pure terms... there
is no argument that Lightning itself is a DC current. The fact that it is
so short may bring the other RF issues to play, but that is not where my
thoughts were when speaking on the DC issue..


Ed

In article . 196,
Ed wrote:


If you're talking lightning, you're talking RF!

73, Roger


Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed




.

Well, actually Lightning is a Pulse of DC, which causes ANY conductor
that it reaches to "RING" which is then AC, as it dissipates...
So, it has Both components.....

Ed wrote:
If you're not convinced after reading the responses, turn on your
radio the next time a lightning storm is anywhere nearby -- or for
that matter, anywhere within skip propagation range. Then explain how
it is your radio is hearing DC.

Roy Lewallen, W7EL


I think we're arguing semantics on this. I spoke in pure terms... there
is no argument that Lightning itself is a DC current. The fact that it is
so short may bring the other RF issues to play, but that is not where my
thoughts were when speaking on the DC issue..


Ed

Semantics are important when the goal is communication.

Lightning induces extreme currents in nearby conductors, and radiates
strong fields covering a wide portion of the radio spectrum, both
characteristics of its RF content. High voltage DC transmission lines,
for example, don't. While you could correctly call lightning "pulsed
DC", it's certainly not correct to say it "isn't RF". As other folks
have pointed out, effective lightning protection requires a solid
understanding of its RF nature.

Roy Lewallen, W7EL

wrote in message
...
In article ,
Owen Duffy wrote:

Roy Lewallen wrote in
:

Ed wrote:

Roger, Lightning is DC. How could it be " RF " if it has no
"frequency" ?


Ed

If you're not convinced after reading the responses, turn on your radio
the next time a lightning storm is anywhere nearby -- or for that
matter, anywhere within skip propagation range. Then explain how it is
your radio is hearing DC.

Roy Lewallen, W7EL


Indeed Roy, rather than argue that lightning doesn't contain AC
components, one could more cogently argue that it is *not* DC.

It is evident that many hams treat lighting as DC in the design of their
lightning protection system (eg small conductor diameter, sharp bends,
loops, u-turns etc in down conductors), but if you pick up the simplest
models for analysing a lightning down conductor, they treat it as excited
by a double ramp current, and the down conductor as an inducance.

Such a model is not a DC model.

Owen

Lightning is pulsed dc. The pulse can be examined by fourier analysis,
as every sophomore electrical engineering student knows, revealing that
the lightning pulse is made up of a superposition of ac waves of many
frequencies.

One can get away with explaining some things about lightning using
simple dc analysis but most of the interesting stuff requires ac
analysis.

And then there is the business of a nearby lightning strike raising the
voltage of ground lines so that during the strike; they are no longer at
ground potential. This requires ac analysis with impedances rather than
resistances.


.... and the mayhem that can ensue to wired services, such as telephone, when
a structure at a transmitting station on a hill is struck!

Chris

On 25 Sep 2009 17:09:06 GMT, Ed
wrote:

I think we're arguing semantics on this. I spoke in pure terms... there
is no argument that Lightning itself is a DC current.

Only in the sense that for 100nS a 160M transmission is DC current.

73's
Richard Clark, KB7QHC

(Dave Platt) wrote in
:

In article ,
Michael Coslo wrote:

Only concern I would have is that the electrical connections are
properly made. AL's talent for oxidizing has been a problem in the
past with house wiring.

A good point.

The National Electric Code has some fairly specific requirements for
how grounding system connections must be made. Soldering is not
permitted, as the high temperatures which can occur at such
connections during a lighting strike can blow the soldered connection
apart.

I always laughed about this requirement, because if you have THAT much
energy present to do this, you're going to have much bigger problems than
that soldered joint.

Jeff Liebermann wrote in
:

On 22 Sep 2009 23:19:40 GMT, Ed
wrote:

QUESTION: Are aluminum ground systems becoming common? Are they
reliable, even after absorbing some heavy strikes? Any other
comments?
Ed K7AAT on the Oregon Coast

I've never seen any that use aluminum wire. Everything I've seen and
what little I've done was copper wire for both mountain top and home
grounding.


You can come to Florida where you'll find the lightning supression systems
on the buildings here all use about a 1" aluminum rope to interconnect all
the spikes and tie into the building ground.

73,

Bruce

"Cecil Moore" wrote in message
...
Ed wrote:
Lightning is DC. How could it be " RF " if it has no
"frequency" ?

Fourier analysis of pulsed DC?

Sorry, I swore of that stuff as soon as I passed the final.