Cecil Moore wrote:
I've been told that this discussion continues in Letters
to the Editor in QEX magazine, to which I don't subscribe
any more. Without knowing the context of those present
discussions, I composed a letter to the QEX editors.
Here it is:

“Where Does the Power Go?” was answered in my magazine article,
“An Energy Analysis at an Impedance Discontinuity in a Transmission
Line”, published by Worldradio magazine and available on my web
page at:

http://www.w5dxp.com/energy.htm

The problem with your paper, Cecil, is the part where you try to
invent the "4th Mechanism of Reflection".

73, Jim, AC6XG

the big confusion factor is using power and energy at all. they are both
derived from the much simpler to handle and understand voltage or current
waves. the biggest problem is that once you change from voltage or current
to power you lose the information necessary to calculate superposition
because you no longer have the phase information from the basic wave
components. this is partly a result of the common use of the swr meter that
measures forward and reflected 'power', everyone thinks they understand how
it works, but very few really do.

"Jim Kelley" wrote in message
...
Cecil Moore wrote:
I've been told that this discussion continues in Letters
to the Editor in QEX magazine, to which I don't subscribe
any more. Without knowing the context of those present
discussions, I composed a letter to the QEX editors.
Here it is:

“Where Does the Power Go?” was answered in my magazine article,
“An Energy Analysis at an Impedance Discontinuity in a Transmission
Line”, published by Worldradio magazine and available on my web
page at:

http://www.w5dxp.com/energy.htm

The problem with your paper, Cecil, is the part where you try to invent
the "4th Mechanism of Reflection".

73, Jim, AC6XG

Dave wrote:
the big confusion factor is using power and energy at all. they are both
derived from the much simpler to handle and understand voltage or current
waves.

But it is hard to answer the "Where does the power go?"
question without using power and energy. BTW, I didn't
start that question. Jon Bloom asked that question in a
Dec. 1994 QEX article as a rebuttal to the information
in "Reflections", by Walter Maxwell.

the biggest problem is that once you change from voltage or current
to power you lose the information necessary to calculate superposition
because you no longer have the phase information from the basic wave
components.

If one knows the length of the transmission line and the
velocity factor, the phases can be deduced. If one is
dealing with a Z0-match, which is most common in amateur
radio, the phase information is trivial because all the
voltages and all the currents are either in-phase or
180 degrees out of phase at the Z0-match point.
--
73, Cecil http://www.w5dxp.com

Jim Kelley wrote:
The problem with your paper, Cecil, is the part where you try to invent
the "4th Mechanism of Reflection".

I wish I had invented it, Jim, but the mechanism of wave
reflection due to interference was well known and under-
stood by optical engineers long before I was born. It's
how non-reflective glass works. Ideally, interference
at the thin-film coating reflects all of the light back
toward the picture behind the glass.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

The problem with your paper, Cecil, is the part where you try to
invent the "4th Mechanism of Reflection".


I wish I had invented it, Jim, but the mechanism of wave
reflection due to interference was well known and under-
stood by optical engineers long before I was born. It's
how non-reflective glass works. Ideally, interference
at the thin-film coating reflects all of the light back
toward the picture behind the glass.

What has been known since long before you were born is that only
direct interaction with matter causes EM waves to reflect. You're far
too modest Cecil. The "4th mechanism of reflection" is completely
your idea! ;-)


73, Jim, AC6XG

Jim Kelley wrote:
What has been known since long before you were born is that only direct
interaction with matter causes EM waves to reflect.

Would you say the changing characteristic impedance between
two waveguides in outer space is a direct interaction
with matter? There is no matter inside the waveguide with
which to interact.

However, I am wondering if I am using the wrong word when
I say interference can cause reflections. Since the same
thing happens with scattering S-parameters, it may be
a 180 degree refraction instead of a 180 degree reflection.
I'll have to take a look at the math.

But no matter what it is called, the results are the same.
"A rose by any other name ..."
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:

[snip]

However, I am wondering if I am using the wrong word when
I say interference can cause reflections. Since the same
thing happens with scattering S-parameters, it may be
a 180 degree refraction instead of a 180 degree reflection.
I'll have to take a look at the math.

Cecil,

You may have taken the first step along the path to enlightenment. It
has been explained previously on RRAA that interference is a result, not
a cause. There are no primary equations related to interference that are
useful for analyzing the exact behavior of a system. Sure, there are
lots of handwaving explanations, but nothing that can actually give real
numbers for fields, currents, or whatever.

If you start with the proper equations for the fields, or voltage and
current if you desire, add in the correct boundary conditions on the
interfaces, and then find the numerical solution, any interference will
appear. No need to make a special case.

If you do this then two positive things will occur.

1. You will be in accord with virtually every mathematician, physical
scientist, optical scientist, and even engineer in applying standard
analysis techniques.

2. All of the worry about missing energy, canceling waves at the
interfaces, etc. simply disappears. It all pops right out from the
proper application of the math, automatically.

73,
Gene
W4SZ

Gene Fuller wrote:
You may have taken the first step along the path to enlightenment. It
has been explained previously on RRAA that interference is a result, not
a cause.

Of course, the Big Bang is the cause of everything,
but what caused the Big Bang?

When one says A causes B which causes C which causes
D, etc., it is not false to say C causes D. There may
be a long line of causes and effects. One step's cause
is the previous step's effect. Interference causes
visible interference rings in a light experiment. And
of course, interference is just one event in a long
line of cause and effect. Without interference, there
would be no interference rings. Without beams of light,
there would be no interference. Without a Big Bang,
there would be no light.

In a line of events, interference is an event that has
a cause and has an effect.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
You may have taken the first step along the path to enlightenment. It
has been explained previously on RRAA that interference is a result,
not a cause.

Of course, the Big Bang is the cause of everything,
but what caused the Big Bang?

When one says A causes B which causes C which causes
D, etc., it is not false to say C causes D. There may
be a long line of causes and effects. One step's cause
is the previous step's effect. Interference causes
visible interference rings in a light experiment. And
of course, interference is just one event in a long
line of cause and effect. Without interference, there
would be no interference rings. Without beams of light,
there would be no interference. Without a Big Bang,
there would be no light.

In a line of events, interference is an event that has
a cause and has an effect.

Cecil,

You just proved the point perfectly. I did not say that interference is
imaginary or that it is not a useful description. I said that
interference is not a primary tool for achieving detailed numerical
solutions. It is a result from such calculations.

Now put your hands down, solve the real equations, and stop all that
mumbo-jumbo about canceling waves and reversing momentum.

8-)

73,
Gene
W4SZ

Cecil Moore wrote:

Jim Kelley wrote:

What has been known since long before you were born is that only
direct interaction with matter causes EM waves to reflect.


Would you say the changing characteristic impedance between
two waveguides in outer space is a direct interaction
with matter? There is no matter inside the waveguide with
which to interact.

Come on, Cecil. You propose a scenario with a change in
characteristic impedance, and then try to pretend there isn't any
matter involved?

I'll have to take a look at the math.

411 - People usually do that _before_ they announce their discovery of
a new natural phenomenon.

But no matter what it is called, the results are the same.
"A rose by any other name ..."

Yes. An enormous blunder is, by any other name..... :-)

73, Jim ac6xg