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

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

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.

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

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

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

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

"Ed" wrote in message
. 192.196...

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..

Ever hear that the lightning strike is an oscillating series of
cloud-ground-cloud-ground currents? Sounds not too much like DC.

Sal