Cecil Moore wrote:
Gene Fuller wrote:
Cecil Moore wrote:
Lots of energy is flowing in both directions.
Only the *NET* energy flow is zero.

I guess you still have not gone back to the books to try to understand
what electromagnetic energy is all about. A good review of the
Poynting theorem would help to minimize the sort of nonsense you
spouted above.

You mean like Ramo & Whinnery in "Fields and Waves ..."
2nd edition, page 291? (begin quote)

In such problems we are often most interested in the ratio
of power in the reflected wave to that in the incident wave,
and this ratio is given by the square of the magnitude of
[rho], as can be shown by considering the Poynting vectors:

Pz-/Pz+ = |rho|^2

end quote.

Pz+ is the forward power Poynting vector. Pz- is the reflected
power Poynting vector. The *NET* Poynting vector is the
difference between those two Poynting vectors.

If Pz+ = Pz-, then the net Poynting vector is zero but
the component Poynting vectors still exist. If you disagree,
please take it up with Ramo & Whinnery.

Cecil,

As usual, you have taken something generally accepted as true, and then
you have added your own special spin. You might have noticed that Ramo &
Whinnery did not go into all of the "net" baloney, and neither did HP in
AN-95. That stuff is only in your imagination.

The last I heard, energy is a scalar quantity. In the cases we are
considering, energy is only positive or zero, not negative. How do two
non-negative scalar quantities "flow" past each other, adding up to a
"net" of zero, unless the initial quantities themselves are zero?

I agree that the concepts included in R&W and in AN-95 are widely used.
However, they were never intended to be distorted into your dream world.

The bouncing traveling wave model is an extremely useful mathematical
device. It does not trump physical reality.

73,
Gene
W4SZ

Gene Fuller wrote:
As usual, you have taken something generally accepted as true, and then
you have added your own special spin. You might have noticed that Ramo &
Whinnery did not go into all of the "net" baloney, and neither did HP in
AN-95. That stuff is only in your imagination.

Translation: I don't have the balls to argue with
Ramo & Whinnery and HP over issues that are more than
obvious to any casual initiated observer.

The last I heard, energy is a scalar quantity. In the cases we are
considering, energy is only positive or zero, not negative.

As you well know, the convention is to apply a negative
sign to positive energy flowing in the opposite direction
from the "forward" energy which is arbitrarily assigned
a plus sign. When Ramo & Whinnery say, using Poynting
vectors, that Pz(net) = Pz+ - Pz-, they are not implying
negative power. They are just using the Poynting vector
convention of direction of energy flow in a transmission
line. We are saying the same thing when we say:

P(load) = P(forward) - P(reflected) = P(net)

Transmission lines have the advantage of having only two
directions so '+' can be assigned to one direction and
'-' assigned to the other. It is completely arbitrary -
the signs can be swapped and the results remain the same.

I agree that the concepts included in R&W and in AN-95 are widely used.
However, they were never intended to be distorted into your dream world.

See "Translation" above.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:


As you well know, the convention is to apply a negative
sign to positive energy flowing in the opposite direction
from the "forward" energy which is arbitrarily assigned
a plus sign.

Still using that vivid imagination, I see.

Let's see even one reference that mentions explicitly the concept of
applying a negative sign to positive energy. Not power, not voltage, not
current, not waves, but energy.



73,
Gene
W4SZ

Gene Fuller wrote:
Cecil Moore wrote:
As you well know, the convention is to apply a negative
sign to positive energy flowing in the opposite direction
from the "forward" energy which is arbitrarily assigned
a plus sign.

Let's see even one reference that mentions explicitly the concept of
applying a negative sign to positive energy. Not power, not voltage, not
current, not waves, but energy.

If you keep feigning ignorance like that Gene, you are
going to lose all respect. If the Poynting vector has
a negative sign, as used by Ramo & Whinnery, that sign
is an indication of the *direction of energy flow*,
see quote below.

From Ramo & Whinnery:

The Poynting vector is "the vector giving *direction* and
magnitude of *energy flow*". When Ramo & Whinnery hang a
sign on a Poynting vector in a transmission line, it is
an indication of the direction of energy flow.

For pure standing waves,
"The average [NET] value of Poynting vector is zero
at every cross-sectional plane; this emphasizes the
fact that on the average as much energy is carried
away by the reflected wave as is brought by the
incident wave."

What? Reflected waves "carrying" energy? Shame on
Ramo & Whinnery for contradicting the rraa gurus.

It is impossible to satisfy you, Gene. When I quote
reference after reference about reflected power, you
say power doesn't reflect. When I change it to reflected
energy, you ask for a reference.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Cecil Moore wrote:
As you well know, the convention is to apply a negative
sign to positive energy flowing in the opposite direction
from the "forward" energy which is arbitrarily assigned
a plus sign.

Let's see even one reference that mentions explicitly the concept of
applying a negative sign to positive energy. Not power, not voltage,
not current, not waves, but energy.

If you keep feigning ignorance like that Gene, you are
going to lose all respect. If the Poynting vector has
a negative sign, as used by Ramo & Whinnery, that sign
is an indication of the *direction of energy flow*,
see quote below.

From Ramo & Whinnery:

The Poynting vector is "the vector giving *direction* and
magnitude of *energy flow*". When Ramo & Whinnery hang a
sign on a Poynting vector in a transmission line, it is
an indication of the direction of energy flow.

For pure standing waves,
"The average [NET] value of Poynting vector is zero
at every cross-sectional plane; this emphasizes the
fact that on the average as much energy is carried
away by the reflected wave as is brought by the
incident wave."

What? Reflected waves "carrying" energy? Shame on
Ramo & Whinnery for contradicting the rraa gurus.

It is impossible to satisfy you, Gene. When I quote
reference after reference about reflected power, you
say power doesn't reflect. When I change it to reflected
energy, you ask for a reference.


Cecil,

Still up to your tricks? I ask for reference on a scalar quantity, and
you respond with some stuff about vectors.

If you want to continue to misinterpret the experts and believe that
power, energy, or whatever flows in opposite directions at a single
point at the same time, go right ahead. I suppose such beliefs expounded
on RRAA are quite harmless in the grand scheme of world affairs.

For future reference, however, just remember: Fields first, then power
or energy. That's the way superposition really works.

(By the way, I am not the one who made the point about power vs. energy.
That must have been someone else.)

73,
Gene
W4SZ

Gene Fuller wrote:
For future reference, however, just remember: Fields first, then power
or energy. That's the way superposition really works.

Way back before optical physicists could measure light
wave fields, they were dealing with reflectance,
transmittance, and irradiance - all involving power
or energy. They are still using those concepts today
proven valid over the past centuries. Optical physicists
calculate the fields *AFTER* measuring the power density
and they get correct consistent answers.

Use whatever method works for you but don't try to change
or replace the body of the laws of physics that was in place
before your grandfather was born. Your rejection of those
laws of physics from the past centuries is why you are so
confused today by your steady-state short cuts. It's why
Keith doesn't recognize a 1.0 reflection coefficient when
it is staring him in the face. It's why Roy rejects energy
in reflected waves. Optical physicists have known for
centuries where the energy goes. That RF engineers are
incapable of performing an energy analysis is sad.

Irradiance (intensity) is a power density. Many problems
in physics can be solved without even knowing or caring
about the strength of the fields. Here is one such lossless
line problem for you.

100w--50 ohm line--+--1/2WL 300 ohm line--50 ohm load
Pfor1--|--Pfor2
Pref1--|--Pref2

Without using fields, voltages, or currents: Calculate
the magnitudes of the four P terms above. Using the RF
power reflection-transmission coefficients, please explain
the magnitude of Pref1. If you cannot do that, you really
need to broaden your horizons and alleviate your ignorance.

Quoting HP AN 95-1: "The previous four equations show that
s-parameters are simply related to power gain and mismatch
loss, quantities which are often of more interest than the
corresponding voltage functions."
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
For future reference, however, just remember: Fields first, then power
or energy. That's the way superposition really works.

Way back before optical physicists could measure light
wave fields, they were dealing with reflectance,
transmittance, and irradiance - all involving power
or energy. They are still using those concepts today
proven valid over the past centuries. Optical physicists
calculate the fields *AFTER* measuring the power density
and they get correct consistent answers.

"Way back" is irrelevant. One only needs to open a serious text book on
Optics, such as Born and Wolf, to see how optical physicists perform
analysis today.


Quoting HP AN 95-1: "The previous four equations show that
s-parameters are simply related to power gain and mismatch
loss, quantities which are often of more interest than the
corresponding voltage functions."

I agree with this statement completely (surprised??). S-parameter
analysis is very useful. However, the "corresponding voltage functions"
are equally valid, even if not as "interesting". What you might also
notice in AN 95-1 is that there is no mention of incident and reflected
waves on a transmission line, each carrying energy (or power or whatever
you prefer), and passing like ships in the night.

You like to talk about conservation of energy, implying that your
"powerful" reflected wave model is essential to meeting the conservation
of energy requirement. In fact, your model is a poster child for the
violation of energy conservation. Electromagnetic energy, like any
energy, is a scalar quantity, and it is only positive. It is not
possible to "net" the non-zero energy contributed from your
counter-traveling waves to zero. The direction of the wave propagation
does not change the sign of the energy. Be careful here; energy is *not*
the same as the energy flux or Poynting vector. Don't mix terms that
have totally different units. What *can* be assigned negative values are
the fields. (Voltage and current are not exactly "fields", but they will
work for these transmission line examples.) A "net" of zero volts or
current is exactly what happens at the standing wave nodes resulting
from the counter-traveling waves. After you have done the superposition
correctly, using fields, not energy or power, then you can easily
determine the energy and power state as needed. Conservation of energy
will be automatically satisfied, assuming no mathematical blunders. The
Maxwell equations would be pretty useless if they did not provide
conservation of energy.

For future reference, just remember: Fields first, then power
or energy. That's the way superposition really works.

73,
Gene
W4SZ