On May 30, 12:59*am, lu6etj wrote:
It is difficult to me reconcile superposition principle with
"interaction", because in spanish "interacción" word means: "Action
exerted MUTUALLY between two or more objects, agents, forces,
functions, etc" (capitals are mine) And I learnt two or more
electromagnetic waves can pass one through other by same point of the
SPACE without recognizing themselves (unlike particles that
"collide"), then, by definition, they not interactuate themselves at
all.

What you learned is usually true in free space. Two light waves can
pass through each other at the same point in space without affecting
or interacting with each other because they are *not collinear*. It is
very difficult to align two light beams in free space such that they
are collinear. However, it can be done in an interferometer.

http://www.teachspin.com/instruments...eriments.shtml

But in an RF transmission line, please understand that there is *no
way to keep the RF waves from being collinear* since it is primarily a
one-dimensional space with only two possible directions. Therefore,
any two coherent RF waves traveling in the same direction in an RF
transmission line, will interact and have a permanent effect. For pure
sinusoidal waves, the transmitted wave, the re-reflected wave, and the
constructive interference wave are all coherent and collinear and
merge into a single forward wave flowing toward the load. The
component waves become inseparable.

We do not "see" any standing wave in space when two same path opposite
direction RF rays cross themselves and there is not contradiction. Are
you agree?

Eugene Hecht, in "Optics", describes standing waves of visible light
in free space. I'm not sure that humans can "see" the standing wave
detail because the frequency is so high, but standing waves of visible
light can certainly exist in free space. If you can, please obtain a
copy of "Optics". If one routed a standing-wave of light through a
cloud chamber, it would become visible. I don't know if the human eye
can resolve the high and low interference patterns but I'm sure
instruments could detect it.

In transmission lines instead it is not easy to think that because
more "tangible" standing wave voltages and currents make us think they
are "interacting". What do you think about it?,

Coherent collinear waves traveling the same direction in a
transmission line superpose, merge, and interact. This invariably
occurs at an impedance discontinuity point during interference
immediately after normal reflections have taken place. RF waves
traveling in opposite directions in a transmission line with a
constant Z0, do not interact.

To satisfy the energy conservation principle, isn' it? This produces a
reflection, right?

Walter Maxwell defines it as a reflection. I am a little more careful
and have adopted the following standards from optical physics. A
"reflection" is something that happens to a single wave and
corresponds to a physical reflection coefficient. A "redistribution"
can be a reflection but can also involve interference between two or
more waves. If superposition is involved, I use the word
"redistribution" rather than "reflection". Walt lumps the concepts of
normal reflection with wave cancellation and introduces the concept of
a virtual reflection coefficient. Both approaches work. IMO, mine is
slightly more detailed. In "Reflections", under the 1/4WL matching
stub section, Walt proves that he fully understands the role of
constructive/destructive interference in the redistribution of energy.

Could be classic electrodynamics be right but we are not applying
correctly, and then classic model not become a losser in this matter?

Yes, if w7el would recognize the energy content (V^2/Z0 watts) that
exists in the voltages that he is superposing, he would be able to
track the reflected energy from the load back to the source and then
back to the load as a component of forward power.

I see you do not agree with some Roy Lewallen proposition: do you
agree with Walter Maxwell on this topic?

In his food-for-thought article, Roy neglected to include the effects
of wave-cancellation/interference at the source resistor in his
example. I don't think that Walter Maxwell has expressed an opinion on
this particular subject of dissipation in the source resistor of a
voltage source as specified by w7el. In a real-world amplifier, Walt
asserts that the source resistance is non-dissipative while, for his
food-for-thought examples, Roy specified a dissipative source
resistance designed to eliminate reflections. Again, what he forgot to
include is redistribution of energy due to wave cancellation, a
concept well understood in the field of EM wave optical physics. He
apparently does not understand the mechanism whereby the conservation
of energy principle is honored so he is forced to falsely assume that
reflected energy is not incident upon the source resistor. Nothing
could be farther from the facts of physics as understood for decades
in the field of optical physics. I was taught constructive/destructive
interference energy concepts in my vector analysis classes at Texas
A&M University during the 50's.
--
73, Cecil, w5dxp.com