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Old December 28th 07, 11:26 PM posted to rec.radio.amateur.antenna
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Default Standing-Wave Current vs Traveling-Wave Current

On Dec 28, 2:44*pm, Cecil Moore wrote:
Keith Dysart wrote:
I suppose this non-sequitor means that you agree that
an ideal section of transmission line, just like an
ideal inductor and capacitor, will store energy forever
if provided with the appropriate initial conditions,
but do not wish to admit it.


I freely admit that it can happen in your mind (like
leaping tall buildings at a single bound).


Thought experiments do usually occur within the mind.
This one is no different.

I do not
believe it can happen in a real-world situation.


That is good, for it is unlikely, though with superconductors
one might come close.

But
if you can demonstrate lossless transmission lines
and lossless inductors on the bench, be my guest and
probably win a Nobel Prize in the process.


More intrigue. This path has been trod before. Begin
with an experiment using ideal elements. Get
uncomfortably close to some truth. Declare the
experiment invalid because it could not happen
in the "real world".

It would be more valuable were you to confront
the demons rather than take the "real world"
escape.

An intriguing thought experiment is to take several
of these sections with stored energy (with the proper
phase relationship) and connect them together. Do
the reflections present at the ends of the short
sections suddenly disappear when the sections
are connected to form a longer line? Are the
reflections now only occurring at the ends of
the longer section?


Reflections are impossible except at physical impedance
discontinuities. There are zero reflections at a point
in a smooth fixed Z0 section of transmission line. Cut
the line and you get 100% reflection.


That is why it is so intriguing. The voltage and current
conditions have not changed, and yet, befo reflections,
after: none.

That's why your
assertions of "no change" don't make sense.


Are you claiming that the voltages or currents
have changed? Identify a measurable value that has
changed and the proof will be yours.

You would
have us believe that short circuit to open circuit is
"no change"???


If it does not change the circuit conditions, i.e.
voltages or currents.

If that is true, there's "no change"
between a shorted 1/4WL stub and an open 1/4WL stub.


Invalid generalization. We were discussing a specific
circuit, not any old 1/4WL stub.

...Keith
 
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