Cecil Moore wrote:

Jim Kelley wrote:

It was a tongue-in-cheek reply, Roy. These problems always seem to
end up with a circulator in them at some point - clearly illustrating
what happens under entirely different circumstances. :-)


The circulator, lossless feedlines of unreasonable length,
Time Domain Reflectometers, TV ghosting, etc. are all tools
for illustration purposes. However, a Z0-matched system is
an ordinary configuration in ham radio and is easy to analyze
since no reflected energy is allowed to reach the source. The
conservation of energy and momentum rules dictate where the
energy must go in such a case. We can debate why the reflected
energy is 100% re-reflected but there is no question that it
*is* 100% re-reflected because none reaches the source and
there are only two directions in a transmission line.

I wish we were able to discuss this without it becoming so
confrontational. As I've said to you many times, you've got 98% of this
thing nailed to a tee. But that 2% is a major error from a physical
standpoint. Energy is not flowing in the way you describe it. Power
doesn't flow at all, but that's a different discussion. When the fields
cancel, as in the anti-reflective/impedance matching scenario, energy is
not conveyed in the reflected direction. There is no conservation of
energy problem until you claim that that energy from cancelled waves IS
moving in the reflected direction. Once you make that claim, you're
forced to imagine a way for it to reverse its course, and that's where
the problem lies. We've been over this a hundred times and you just
refuse to accept it. It violates physics. It violates Maxwells
equations. It's wrong, and I hate arguing with you about it, but as a
fellow enthusiast I advise you not to print that part of your article in
QEX. It's an absurdity in the midst of brilliance, not unlike myself. ;-)

73, Jim AC6XG

Jim Kelley wrote:
I wish we were able to discuss this without it becoming so
confrontational.

Me too. Please treat me the way you would like to be treated
and we will get along just fine. Oh, and thanks for the doorknob
caps. I use them now instead of stubs.

As I've said to you many times, you've got 98% of this
thing nailed to a tee. But that 2% is a major error from a physical
standpoint. Energy is not flowing in the way you describe it. Power
doesn't flow at all, but that's a different discussion.

I've been very careful to consider power as the measured energy flowing
past a point even though many others, including the IEEE, present the
Power Flow Vector right along with the current phasor. But as far as
EM wave energy and power are concerned, they are virtually
interchangeable. EM wave energy always travels at the speed of light -
imagine that. :-) The energy in an EM wave can only be stored as an
EM wave traveling at the speed of light as in a delay line. It cannot
be put into an RF battery and used as needed for an old wives' tale.
Walter Johnson recognized the close relationship between EM energy and
EM power and actually presented the "conservation of power" principle in
his book. The only difference between EM energy and EM power is time.
The joules in the joules/sec must be conserved.

When the fields
cancel, as in the anti-reflective/impedance matching scenario, energy is
not conveyed in the reflected direction.

Of course, and I never said it was. That's your straw man left over from
our last argument. If the fields cancel, there is no energy available
for a rearward flow. That's why you cannot measure reflected power in
the coax on a Z0-matched system. All the reflected energy has changed
direction. But we know the internal reflected energy has traveled in
the rearward direction. What altered its momentum in that rearward
direction?

Energy must be conveyed from the far surface or the fields would not
cancel. That's called the internal reflection and its rearward flow
can be detected. Since the internal reflection wave possesses momentum
in the rearward direction, something has to reverse that momentum. We
can disagree on the mechanism that reverses the momentum of the
internal reflected wave, but the wave is there and can be detected.

The entire reason I cannot accept what you say is that you have never
given a reasonable explanation of what happens to the momentum of
the rearward-traveling internal reflection wave. Want to try again?
Please concentrate on that one topic. Resolving the momentum in the
internal reflection wave is the only way to convince me that I am wrong.
I think that is the concept that convinced the QEX editors that I was
right. If one accepts the conservation of momentum principle, then
one has to accept a cause for the reversal of that momentum.

The internal reflection wave is illustrated in section 9.4.1 of
"Optics". It has obviously traveled in the rearward direction across
the width of the thin-film. What happens to its momentum and energy
if it gets canceled?

There is no conservation of
energy problem until you claim that that energy from cancelled waves IS
moving in the reflected direction.

Something has to reverse the momentum in the wave reflected from the
far surface, i.e. the "internal reflection". If you don't know what
that is, reference section 4.3 in "Optics". You have never given a
reasonable explanation of what reverses the momentum of the internal
reflection which, I'm sure you would agree, doesn't appear in the
glare so it had to be reversed. Exactly how was it reversed?

Once you make that claim, you're
forced to imagine a way for it to reverse its course, and that's where
the problem lies.

No, since it is obvious that the momentum of that internal reflection
wave reverses, a reversing mechanism is necessary. I've presented a
mechanism and you haven't.

We've been over this a hundred times and you just
refuse to accept it.

Yes, and you refuse to accept it. Momentum doesn't change by magic.
There has to be a physical reason. I have presented my take on that
physical reason. You have presented no explanation. Between having
an explanation and having none, guess what my choice will be?

Please just explain how the momentum in the internal reflection wave
gets reversed within the boundary conditions of the classical wave
reflection model. No quantum physics, please.

So let's concentrate on that narrow topic of what happens to the
momentum in the internal reflection wave, shall we? Here's a
diagram where 'n' is the index of refraction and the internal
reflection from surface 'B' is shown:

| |
laser--------air----|----thin-film-------|----glass---------
n-1.0 | n=1.2222 | n=1.4938
A --reflection----B

The internal reflection that I have been talking about occurs when
the forward wave in the thin-film encounters surface 'B'. The
reflectance is 0.01 at that surface so one percent of the forward
irradiance will be reflected. It will have momentum in the rearward
direction. Please tell us what alters the momentum of that reflection
such that it doesn't appear as glare at surface 'A' and instead
reverses direction and joins the forward wave.
--
73, Cecil http://www.qsl.net/w5dxp

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