Revisiting the Power Explanation
 

On Fri, 30 Mar 2007 14:45:56 GMT, Walter Maxwell
wrote:

The part I feel
is contradicted is that when total re-reflection

Hi Walt,

Here I read the subject - reflection.

is caused without a total discontinuity such as a physical
short or open circuit,

Here I read a first condition - no physical manifestation.

it is caused by resultant of the interference between the forward and reflected
voltages and the interference between the forward and reflected currents.

Here I read the causal connection between the subject and the
condition.

However, waves do not mix in a linear space. The proof is the lack of
heterodyning of the RF soup we live in. Further, interference is the
mixing product of at least two sources (waves, what-have-you) in a
load. No load, then no interference.

Unfortunately, to raise the prospects of interference requires that
load, and requiring that load immediately violates the first condition
above - no physical manifestation.

When the phase relationships between
the respective voltages and currents are correctly adjusted to achieve an impedance match, the resultant is
either a virtual short circuit or a virtual open circuit, which causes total re-reflection of the waves
reflected from the mismatched load terminating the line. Consequently, the interferences cause the
re-reflection.

All of this is true in isolation, in fact it describes the actions of
a physical load called an ATR/TR Tube in a RADAR waveguide. When the
right wavelength conditions of a wave and environment meet in the
tube, formerly an open it now conducts to create:
1. A literal short;
2. A short that is found at even quarterwave intervals;
3. An open that is found at odd quarterwave intervals.
The physical and literal short was first necessary as the initiator.
Without the tube, the co-mixing of waves would not have done the job
in isolation.

Are you saying that this explanation of the re-reflection concept is incorrect?

I'm afraid so.

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

Richard Clark wrote:
Cecil Moore wrote:
If the impedance discontinuity between two different Z0s
of transmission lines is not a "load/physical manifestation",
then we can toss out an S-Parameter analysis as invalid.

If frogs had wings, they wouldn't bump their assess a-hoppin'

Well, does the impedance discontinuity between two different
Z0s of transmission line meet your requirement of a "load/
physical manifestation"? Is a characteristic impedance
physical enough for you?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Fri, 30 Mar 2007 16:33:30 GMT, Cecil Moore wrote:

Walter Maxwell wrote:
Well Owen, then how do you explain re-reflection at the souce in the absence of z virtual sc or oc?

I'm not Owen but in S-Parameter terms it is explained by:

b1 = (s11)(a1) + (s12)(a2) = 0

When (s11)(a1) equals -(s12)(a2), there is total destructive
interference in the direction of b1 toward the source. That's
the wave cancellation that is associated with your sc and oc.

Cecil, I know you're not Owen, but my statement to him was a challenge for him to explain in HIS words why he
believes my explanation of the concept is wrong.

When you recite chaper and verse to me you're preaching to the choir, but you knew that.

Walt

Revisiting the Power Explanation
 

On Fri, 30 Mar 2007 16:51:36 GMT, Cecil Moore
wrote:

Richard Clark wrote:
Unfortunately, to raise the prospects of interference requires that
load, and requiring that load immediately violates the first condition
above - no physical manifestation.

If the impedance discontinuity between two different Z0s
of transmission lines is not a "load/physical manifestation",
then we can toss out an S-Parameter analysis as invalid.

If frogs had wings, they wouldn't bump their assess a-hoppin'

Revisiting the Power Explanation
 

Walter Maxwell wrote:
When you recite chaper and verse to me you're preaching to the choir, but you knew that.

Just wanted to provide some support from HP's Ap-Note 95-1
available on the web from:

http://www.sss-mag.com/pdf/hpan95-1.pdf
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Fri, 30 Mar 2007 09:38:20 -0800, Richard Clark wrote:

On Fri, 30 Mar 2007 14:45:56 GMT, Walter Maxwell
wrote:

The part I feel
is contradicted is that when total re-reflection

Hi Walt,

Here I read the subject - reflection.

is caused without a total discontinuity such as a physical
short or open circuit,

Here I read a first condition - no physical manifestation.

it is caused by resultant of the interference between the forward and reflected
voltages and the interference between the forward and reflected currents.

Here I read the causal connection between the subject and the
condition.

However, waves do not mix in a linear space. The proof is the lack of
heterodyning of the RF soup we live in. Further, interference is the
mixing product of at least two sources (waves, what-have-you) in a
load. No load, then no interference.

Unfortunately, to raise the prospects of interference requires that
load, and requiring that load immediately violates the first condition
above - no physical manifestation.

When the phase relationships between
the respective voltages and currents are correctly adjusted to achieve an impedance match, the resultant is
either a virtual short circuit or a virtual open circuit, which causes total re-reflection of the waves
reflected from the mismatched load terminating the line. Consequently, the interferences cause the
re-reflection.

All of this is true in isolation, in fact it describes the actions of
a physical load called an ATR/TR Tube in a RADAR waveguide. When the
right wavelength conditions of a wave and environment meet in the
tube, formerly an open it now conducts to create:
1. A literal short;
2. A short that is found at even quarterwave intervals;
3. An open that is found at odd quarterwave intervals.
The physical and literal short was first necessary as the initiator.
Without the tube, the co-mixing of waves would not have done the job
in isolation.

Are you saying that this explanation of the re-reflection concept is incorrect?

I'm afraid so.

73's
Richard Clark, KB7QHC

Oh, 'cmon Richard, are you saying that if a load reflected wave incident on the source wave doesn't result in
an interference between the two waves? If this is what you're really saying, then it is equal to saying that
the principal thrust of my book Reflections is wrong. Is this what you mean? And are you saying that the
report of the Fl State professors that Cecil referred to is also wrong?

In addition, when the radiation from two dipoles fed from the same source is of the same magnitude and
opposite phase at a point in space, resulting in a null in the radiation pattern at that point, are you saying
that the radiation from the two dipoles is not in interference at that point? If this is what you're saying,
then how is the null in the pattern created?

Walt

Revisiting the Power Explanation
 

Cecil Moore wrote:
Jim Kelley wrote:
But my statement is nevertheless honest, truthful, and factual. What
part of it do you feel is contradicted by physical laws?

I find it strange that Hecht's definition of "interference"
doesn't even mention your alleged cause of the interference,
i.e. superposition. From "Optics", by Hecht in his own
bold italics:

"Optical interference corresponds to the interaction of
two or more light waves yielding a resultant irradiance
that deviates from the sum of the component irradiances."

One might argue that "the interaction of two or more light
waves" is superposition but why didn't Hecht choose
"superposition" instead of "interaction"? And a
"correspondence" of interference to the interaction of
the waves certainly doesn't imply cause and effect. It
seems instead to imply an inseparability between the
interference and the interaction of the waves which
is of course obvious.

Hecht seems to treat the superposition principle as more
of a set of rules to be followed by the interfering waves
than an actual act. FYI, the definition of "superpose"
doesn't mention EM waves at all.

Cecil,

You seem to misinterpret the significance of the "weasel words" used by
your various author-gurus.

An expression such as, "Optical interference corresponds to the
interaction . . .", without any accompanying equations is intended to
give the reader a general feeling for what is going on. Such words do
not imply cause and effect. Nor should those fuzzy expressions be taken
to imply "inseparability" as a rigid requirement.

Interference is merely a convenient description of what happens when
waves meet. There are no equations for "interference"; there are no
units for "interference"; there are no standard symbols for
"interference". Interference is an observation, not a physical law.

Stick to the standard field equations and you will not be misled. I am
confident that somewhere Hecht goes though the standard treatment of
setting up field functions with boundary conditions and then solves the
equations to show what happens at interfaces. Interference can be seen
in the solutions to that problem. I'll bet he does not start with
interference and then proceed to determine the E-fields and H-fields.

Superposition is a basic mathematical concept that applies to linear
systems. It is not necessary to catalog every possible application for
superposition. The fact that your definition of "superpose" does not
mention EM waves is of zero importance in the world. Superposition still
applies even if your dictionary does not know about it.

73,
Gene
W4SZ

Revisiting the Power Explanation
 

Gene Fuller wrote:
There are no equations for "interference";

On the contrary, quoting from "Optics", by Hecht,
page 283, 4th edition: "It follows from Eq.(7.9)
that the resultant flux density is not simply the
sum of the component flux densities; there is an
additional contribution, 2*E01*E02*cos(A1-A2), known
as the *interference term*. The emphasis is Hecht's,
not mine.

Later on page 388: "The interference term becomes

I12 = 2*SQRT(I1*I2)cos(Gamma)"

What does it take to make that look like an equation
to you? Have you ever taken time to read and understand
"Optics", by Hecht?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Richard Clark wrote:
There is absolutely no example of interference that does not rely on a
load to reveal it.

I suspect you would consider blowing smoke through
a region of interference or any other means of detection
to be a "load"? (It is left to the readers to conclude
what it is a load of.)

So the real question is metaphysical: Does undetected
interference exist and if so, how does one prove it?
Reminds me of some of the steady-state arguments.

The students of Aristotle would argue that the interference
exists whether it is detected or not. (A thing is what it
is.)

The students of Plato would argue that the interference
doesn't exist unless it is detected. (A thing is not
necessarily what it appears to be.)
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Fri, 30 Mar 2007 18:19:20 GMT, Walter Maxwell
wrote:

Oh, 'cmon Richard, are you saying that if a load reflected wave

Is not the same statement as your earlier one:
On Fri, 30 Mar 2007 14:45:56 GMT, Walter Maxwell wrote:

The part I feel is contradicted is that when total re-reflection
is caused without a total discontinuity such as a physical
short or open circuit

What is in your "without a total discontinuity" that is now found in
your "load reflected wave?"

Are we to now parse "total discontinuity" as being wholly different
from "partial discontinuity" such that waves suddenly mix from that
difference?

My example of the classic AT/ATR tube evidences EVERY observation you
offer, except it is a necessary load without which those observations
would never appear. If I were to replace its "total discontinuity"
with a weak tube (it exhibits less than total short); it too would
exhibit EVERY observation you offer EXCEPT they would be imperfect or
"partial discontinuities" repeated every quarter wave. It is obvious
that the effect follows the physical load, not the waves (they haven't
changed when the tube went bad). The physical load is the principle
in the process of interference.

There is absolutely no example of interference that does not rely on a
load to reveal it.

73's
Richard Clark, KB7QHC