Cecil Moore wrote:
The impedance discontinuity is certainly in the cause and effect *chain*
as is the Poynting vector reversal. But simply asserting that the
impedance discontinuity causes the Poynting vector reversal is
a sophmoric begging of the question and leaves out some important
details. A causes B. B causes C. C causes D. You are certainly logically
correct in saying that A causes D, but your statement leaves out some
important intermediate details, namely B and C. (see below)

For instance, the impedance discontinuity causes nothing unless the
source energy exists and is taken into account as a cause. The
question is what are the necessary and sufficient conditions for an
impedance discontinuity to result in a complete reversal of the
(Pz2-) Poynting vector? Since a source is necessary, the source can
be considered as a cause. (The creator of our species can even be
considered as a necessary cause as can the Big Bang.)

Looking at it from a scientific standpoint, the impedance discontinuity
can only directly reverse half the magnitude of the Poynting Vector because
the physical power reflection coefficient is 0.5. So how does the other
half
of the magnitude of the Poynting Vector get reversed? It's all been covered
by the Melles-Griot web page and the Molecular Expressions FSU web page.

In the presence of EM source energy, the impedance discontinuity causes
reflections. One of those reflections reverses half the magnitude of the
(Pz2-) Pointing Vector. That magnitude is (Pz2-)(rho^2).

Two of those reflections engage in wave cancellation. One is (Pz1+)(rho^2).
The other is (Pz2-)(1-rho^2), the other half of the (Pz2-) Poynting Vector.
These two reflections have equal magnitudes and opposite phases and
therefore
cancel. Their energy components reverse direction and head back toward
the load
as explained on the Melles-Groit and Molecular Expressions web pages.

And that's how the (Pz2-) Poynting Vector gets reversed. It's a two-step
process, each step involving half of Pz2- in the above example.

And that folks, is the sound of one hand waving. :-)

In the absence of impedance discontinuities, the transmission line
would appear to be infinitely long and would not produce reflections.


That's true. The impedance discontinuity causes the reflections that engage
in wave cancellation. In steps, it goes like this.

A. Impedance discontinuity driven by a source of EM energy

B. Reflections (implied mismatch)

C. Wave Cancellation (permanent destructive interference)

D. Energy direction and momentum reversal (constructive interference)

A causes B. B causes C. C causes D. This is in any freshman logic book.
You are certainly logically correct in saying that A causes D, but
your statement leaves out some important intermediate details. Those
intermediate details are what this discussion is all about.

Except that D is not caused by, and cannot be caused by C. Only
reflection can cause reflection. The claim that momentum reverses
direction without encountering a physical reflector is a violation of
conservation of momentum.

ac6xg

Cecil Moore wrote:


Waves cannot even exist without energy.


Correction. Waves cannot be created without energy. Electromagnetic
fields can indeed exist without necessarily conveying energy from one
place to another.


Correction. DC electromagnetic fields can exist without conveying energy
but the context is RF EM waves.

Tell us more about DC electromagnetic fields, Mr. Science! :-)

EM wave-fields cannot exist without energy.

Like I said, they cannot be created without energy. They can however
exist without conveying energy from one place to another.

ac6xg

On Tue, 09 Aug 2005 13:56:40 -0700, Richard Clark
wrote:
Hi Walt,

What stopped it if not a physical barrier?

Richard, there is no physical barrier in an antenna array that changes
the shape of the radiated pattern. The barrier is caused only by
destructive wave interference.

but due to the
interference the result was a null

A null is not the absence of energy, but is the combination of equal
and opposing forces. If you were the Ref at a title bout, and stepped
between two punches of equal magnitude; then you wouldn't move very
far, the motions would cancel, but most would doubt you'd be up again
before the "count."

In a title bout two punches of equal magniude are coming from opposite
directions. The energies in the two punches is dissipated in the
noggins of the morons who got into the bout;. The resulting null is in
reducing the already worped brains to zero.

Nulls are evidenced quite clearly in bridges of many designs. They
may balance between huge potentials (energy), but evidence absolutely
no current (or power from energy times current). If you unplugged the
equipment from a bridge, the absence of current would not be an
indication of a null. Nulls within the context of engineering
necessarily carries the implication of energy present.

We're not talking about nulls in bridges, we're talking about energy
controlled in desired directions, reduced in some directions, with the
energy lost in one direction adding to that in another; but you know
this.
in that direction and an increased
amount of energy in the opposite, or forward direction, achieving gain
in that direction?

Linear systems do not exhibit "gain." The combination of forces are
due to the total field in comparison to the region of interest.

Well, Richard, there is no non-linearity in the formation of antenna
radiation patterns. Are you saying there is no 'gain' when energy is
taken from one direction and pushed into another? With respect to
radiation patterns, 'gain' is relative, and not consideredas an
increase in power. But you know that too.

It is by similar simplifications that we have contributors here who
offer that the radials of elevated ground planes do not radiate
energy. Their contribution to producing a power at a remote load may
cancel such that no power is evident, but this does not negate the
radiation nor the energy present.

73's
Richard Clark, KB7QHC

My comments are totally unrelated to elevated ground planes. I'm only
trying to prove to Jim that wave interference DOES cause energy to
shift direction without any aid of a physical entity. The only cause
of the change in direction of energy radiated from an array of dipoles
is wave interference, the interference between the waves emanting from
the different dipoles.

Walt, W2DU

Richard Clark wrote:

On Tue, 09 Aug 2005 17:11:41 -0700, Jim Kelley
wrote:

There is no such thing in reality as a wave that delivers no energy.

See Born and Wolf for examples.


Hi Jim,

This is intriguing for a wave (I presume you were adhering to the
singular). For those who lack these references, do you have any
concrete examples?

73's
Richard Clark, KB7QHC

Hi Richard,

You may recall this came up before. The example I noted was in the
instance of total internal reflection. Page 47, "Principles of Optics"
Born and Wolf. When the angle of incidence with respect to the normal
exceeds the critical angle "no light enters the second medium. All the
incident light is reflected back into the first medium and we speak of
total reflection. Nevertheless the electromagnetic field in the second
medium does not disappear, only there is no longer a flow of energy
across the boundary." They footnote that an elegant experimental
demonstration is described by W. Culshaw and D. S. Jones Proc. Phys.
Soc. B 1954.

It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period. Though there's no uncertainty about the presence of
electromagnetic waves on such a line in the steady state.

73, Jim AC6XG

Walter Maxwell wrote:


My comments are totally unrelated to elevated ground planes. I'm only
trying to prove to Jim that wave interference DOES cause energy to
shift direction without any aid of a physical entity. The only cause
of the change in direction of energy radiated from an array of dipoles
is wave interference, the interference between the waves emanting from
the different dipoles.

Walt, W2DU

The radiation pattern of an antenna is the result of the superposition
of fields either radiated or reflected from REAL surfaces. Energy from
the radiating and reflecting elements travels only in directions where
the resulting superposed fields are not zero. The resulting
interference pattern is simply the plot in 3 dimensional space of where
energy is being directed.

73, Jim AC6XG

Jim Kelley wrote:
Except that D is not caused by, and cannot be caused by C. Only
reflection can cause reflection. The claim that momentum reverses
direction without encountering a physical reflector is a violation of
conservation of momentum.

You missed the point, Jim. The wave indeed does encounter a
physical reflector and indeed cannot happen without the physical
impedance discontinuity. It meets all of your requirements.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

Jim Kelley wrote:
Like I said, they cannot be created without energy. They can however
exist without conveying energy from one place to another.

Please give us your tricky-dicky definition of "convey", Jim.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

Jim Kelley wrote:
It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period.

Use a signal generator with a circulator load as the source. Cause a
noise glitch on the source signal. When will you see the glitch
across the circulator resistor? One cycle later. Reckon where that
glitch went during that one cycle? Man, that's a tough question. :-)
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

On Tue, 09 Aug 2005 22:14:48 -0400, Walter Maxwell
wrote:

We're not talking about nulls in bridges, we're talking about energy
controlled in desired directions, reduced in some directions, with the
energy lost in one direction adding to that in another; but you know
this.

Hi Walt,

What is being discussed is energy. Energy is wholly transparent to
application. The laws for its conservation don't care if you are
shooting marbles or colliding stars. Physics eventually devolves to
very few units of measure and the books balance on both sides of the
event.

in that direction and an increased
amount of energy in the opposite, or forward direction, achieving gain
in that direction?

Linear systems do not exhibit "gain." The combination of forces are
due to the total field in comparison to the region of interest.

Well, Richard, there is no non-linearity in the formation of antenna
radiation patterns. Are you saying there is no 'gain' when energy is
taken from one direction and pushed into another? With respect to
radiation patterns, 'gain' is relative, and not consideredas an
increase in power. But you know that too.

And we both know no energy is created or lost without an atom being
ripped apart. The appeal to antenna "gain" is simply the choice of
where your attention is focused. Energy is neither lost nor created,
nor increased, nor decreased, the concomitant power that results of a
load being exposed to several sources of energy has a resultant. That
resultant expressed in the gain charts presumes there is a continuum
of loads throughout the circle/sphere of the lobes being described.

It is by similar simplifications that we have contributors here who
offer that the radials of elevated ground planes do not radiate
energy. Their contribution to producing a power at a remote load may
cancel such that no power is evident, but this does not negate the
radiation nor the energy present.

73's
Richard Clark, KB7QHC

My comments are totally unrelated to elevated ground planes. I'm only
trying to prove to Jim that wave interference DOES cause energy to
shift direction without any aid of a physical entity. The only cause
of the change in direction of energy radiated from an array of dipoles
is wave interference, the interference between the waves emanting from
the different dipoles.

Elevated ground planes, if they do not fit into the discussion, reveal
that discussion cannot support their characteristics. This is
expressly a failure of that discussion.

Elevated ground planes radiate from the entire structure. What they
radiate is energy. The net sum of those energies, at a distance,
combined into a load, reveal that the contribution of the radials
nullifies in horizontal polarity, and because the relative height
(thickness) of the radials is so small in proportion to the main
vertical element, make very little contribution to the vertical
polarity. Yet and all, every radial element is blasting away in
proportion to its current and radiation resistance. The radials are
pouring energy into the Æther with every effort as the main vertical
element. Reduce this to the barest minimum of two radials and the
results are identical, however, lop off to one radial element, and the
energy balance upsets the apple cart and a horizontal component,
formerly offset by equal opposing energies, appears. That last radial
element had always been radiating energy, it is still radiating
energy.

Optics has been maligned through very poor examples here, but if two
beams of light intersect we have wave interference ONLY if a load is
present at that intersection. A load is a necessarily physical
correlative. Otherwise, these energies have absolutely no
interaction, barring a non-linear medium.

It then follows that waves do not mix freely in and of themselves and
hence they are not causative agents. This has been illustrated by The
Extreme Failure of Poor Concepts in Discussing Thin Layer Reflections.

73's
Richard Clark, KB7QHC

On Tue, 09 Aug 2005 19:36:51 -0700, Jim Kelley
wrote:

There is no such thing in reality as a wave that delivers no energy.
You may recall this came up before. The example I noted was in the
instance of total internal reflection. Page 47, "Principles of Optics"
Born and Wolf. When the angle of incidence with respect to the normal
exceeds the critical angle "no light enters the second medium.

Hi Jim,

OK, and in relation to:

It's also arguable whether any energy is transferred from a source to a
lossless, open circuited, 1/2 wave transmission line after the transient
period.

But:

Though there's no uncertainty about the presence of
electromagnetic waves on such a line in the steady state.

is becoming strained language where so many struggle with English. Is
this to imply there's uncertainty about the presence of light that is
captured by total internal reflection? At the last census of total
cancellation, if it didn't meet a certain percentage it became
invisible. Something like an undocumented worker....

73's
Richard Clark, KB7QHC