Standing-Wave Current vs Traveling-Wave Current
 

Keith wrote:
"I am surprised that a book on optics would discuss the output impedance
of Thevenin`s equivalent circuits."

Hecht is a physicist.

On page 74 of Terman`s 1955 0pus, he writes:
"According to Thevenin`s theorem, any linear network containing one or
more sources of voltage and having two terminals behaves, in so far as a
load impedance connected across these terminals is concerned, as though
the network and its generators were equivalent to a simple generator
having an internal impedance Z and a generated voltage E, where E is the
voltage that appears across the terminals when no load is connected and
Z is the impedance that is measured between the terminals when all
sources of voltage are short-circuited."

On page 87 of his 1955 opus, Terman writes:
"The vector ratio of E2/E1 of the voltage of the reflected wave to the
voltage of the incident wave at the load is termed the "reflection
coefficient" of the load."

On page 97, Terman writes:
"The standing-wave ratio S is one means of expressing the magnitude of
the reflection coefficient;"

On page 214 of "Schaum`s Outline of College Physics", Bueche & Hecht
write:
"Standing waves---These might better not be called waves at all since
they do not transport energy and momentum.---"

Cecil is vindicated.

Best regards, Richard Harrison, KB5WZI

Standing-Wave Current vs Traveling-Wave Current
 

On Jan 3, 12:04*pm, Cecil Moore wrote:
Keith Dysart wrote:
On Jan 2, 2:48 pm, Cecil Moore wrote:
Keith Dysart wrote:
I assume that you have not provided a reference to support
this assertion because you have not been able to find one.
I provided the reference a number of times and you
chose to ignore it. The reference is the chapter on
interference in "Optics", by Hecht.

I am suprised that a book on optics would discuss the
output impedance of Thevenin equivalent circuits.

The "Optics", by Hecht reference is for destructive
and constructive interference, not Thevenin equivalent
circuits, but your attempt to confuse everyone is noted.

My attempt to confuse!? We were discussing the determination
of reflection coefficients for Thevenin equivalent circuits.

But in another post, you have agreed that there
is a complete lack of references supporting your
position, so the question is now settled and you
can use the standard methodology to compute
reflection coefficient at a generator where
the output impedance is well defined.

Enjoy the new ability to solve problems that
were previously outside your grasp.

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
Cecil Moore wrote:
1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

So it is stored only in the E field.

Wrong! Please reference a book on EM waves. An
EM wave CANNOT have a stationary E-field in an
ordinary transmission line or in free space.

But the important question is: Do you consider it
to be an EM wave when only an E field is present?

No, that violates the definition of an EM wave. If
only an E-field is present in a transmission line or
in free space, it is NOT an EM wave, by definition.

For a single EM wave to exhibit a zero H-field, the
Z0 would have to be infinite which is clearly impossible
for free space or ordinary transmission lines.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
If such analysis is appropriate, then it seems
to me that a pulse can be viewed as a chunk of
charge moving down the line.
Q2. Is this an appropriate view?

No.

Q3. If so, then what happens when two such chunks
of charge collide in the middle of the line?

They don't "collide". Clouds of photons collide
and their behavior is well known.

Q5. If no charge crosses the mid-point, then how
do the pulses, made up of chunks of charge.
pass the mid-point?

How can two water waves pass through each other
while the water molecules are only moving up and
down?
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

On Jan 3, 12:43*pm, Cecil Moore wrote:
Keith Dysart wrote:
Cecil Moore wrote:
1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

So it is stored only in the E field.

Wrong! Please reference a book on EM waves. An
EM wave CANNOT have a stationary E-field in an
ordinary transmission line or in free space.

But the important question is: Do you consider it
to be an EM wave when only an E field is present?

No, that violates the definition of an EM wave. If
only an E-field is present in a transmission line or
in free space, it is NOT an EM wave, by definition.

For a single EM wave to exhibit a zero H-field, the
Z0 would have to be infinite which is clearly impossible
for free space or ordinary transmission lines.

Good answers. Exactly as I expected. Now please
explain the applicability of EM waves to the
state of an open circuited line excited with a
step function, especially after it settles to a
constant voltage (where only an E field will be
present).

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
Q5."If no charge crosses the mid-point, then how do the pulses, made up
of charge, pass the mid-point?"

Radio waves propagate through empty space. No charges are needed for
propagation, but a wire contains free electrons which are urged to move
in-synch by a passing wave. That does not mean they migrate. In the
wire, electrons go nowhere fast. Their motion is mostly in-place. It the
energy which is traveling, not the electrons.

Best regards, Richard Harrison, KB5WZI

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:

[...]

You did not directly answer Q1, but I take if from all the other
responses that you are saying the answer is "no, it is not
appropriate to view a transmission line as distributed capacitance
and inductance and analyze its behaviour using charge stored in
the capacitance and moving in the inducatance?"

That is not what you originally stated.

Taking this invalidates all the subsequent questions since they
are based on the premise that this kind of analysis is
appropriate.

Yes, it does.

Your explanation is easily proven false. Let's suppose it was true.

Suppose it was possible to introduce a pulse of charge onto a
conductor.

Since like charges repel each other, what keeps the pulse together?

In other words, what prevents it from destroying itself?

Then, when the first pulse meets the second, what mechanism allows
them to bounce off each other?

Then, after they have bounced off each other, what mechanism keeps
them together?

[...]

Keith

Regards,

Mike Monett

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
The presence of this poster providing misleading
information makes this group a rather unique learning
environment.

But a learning experience nonetheless. All one has
to do regarding false information is to produce
valid technical references to the contrary.

Ad hominem attacks are not technical references
and the mere assertion that the information is
misleading implies some level of omniscience in
the asserter that is not in evidence.

For the record: The only controversial assertion
that I have ever made is that coherent EM wave
cancellation can cause a redistribution of the
EM energy in the opposite direction in a transmission
line. No one has proved that assertion to be wrong.

A couple of technical web pages assert that wave
cancellation can be the cause of a redistribution
of photonic energy to areas that allow constructive
interference.

Since there is only one other direction available
in a transmission line, the constructive interference
must occur in the opposite direction from the
direction of wave cancellation.

That seems like a no-brainer to me.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

On 22 Dec 2007, 12:57, John Smith wrote:
Cecil Moore wrote:
...
Why is the ignorance level about traveling waves so high
on this newsgroup? It's the result of those inadequate
lumped circuit models.

In Einsteins' spirit, let's have a real look at waves (basically the
KISS rule):

http://www.colorado.edu/physics/2000...ing_wave1.html

you must go to the bottom of each page and click to view the next of the
series.

The standing wave is "driven" by the forward & reverse traveling waves,
yet best thought of as being "separate in existence" (there are a total
of 3 waves!) ... and can only/really exist within strict confines of
design--or, resonance ...

But then, this is nothing new, or, you already knew that ... I just like
the way this is all presented--on those pages, or, even newbies are
introduced to the depth of the argument ...

Regards,
JS

John, There is no way you have a standing wave. I know the books
suggest
that but the books are wrong. When current gets to the top of a
fractional
wave antenna it just does not turn back. It has to wait until half a
period time has
elapsed The turning around point is determined by frequency and
frequency alone regardles of the length of the radiator. I f the
forward time has not run out the current must continue going forward
and that means going down the center of the wire which is resistive
only and does not generate radiation. The current traverses the center
twice and it is when it starts to return on the outside is when
propagation comences. So at no time is the current changing direction
except at a time of half a period. It only has one pulse per period
and that pulse is dependent on the surface content that it traverses.
If it is a full wave where the length equates to half a period then
the capacitance and inductance is comensurate with length.
If it is a fractional wavelength it only radiates when returning on
the surface where the energy storage content is half that of a full
wave
This particular point has arrested the advances in antennas for 100
years just because man does not accept change.
Regards
Art

Standing-Wave Current vs Traveling-Wave Current
 

Mike Monett wrote:
The term "bounce" means they interact. Electromagnetic signals do
not interact. They superimpose. Each is completely unaware and
unaffected by the other.

Except when they are coherent, collinear in the same direction,
equal in magnitude and 180 degrees out of phase. Thensomething
permanent happens as signified by the s-parameter equation.

b1 = s11*a1 + s12*a2 = 0

s11*a1 and s12*a2 are coherent, collinear in the same
direction, equal in magnitude and 180 degrees out of
phase. Their combined energy components are redistributed
in the direction of b2 = s21*a1 + s22*a2

Squaring the above equation results in the power density
irradiance equation from the field of optics.

Preflected = (b1)^2 = (s11*a1)^2 + (s12*a2)^2 + 2*s11*a1*s12*a2 = 0

micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/waveinteractions/index.html

"... when two waves of equal amplitude and wavelength that
are 180-degrees ... out of phase with each other meet, ...
All of the photon energy present in these waves must somehow be
recovered or redistributed in a new direction, according to the
law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, ..."

That certainly sounds like an "interaction" to me.
--
73, Cecil http://www.w5dxp.com