Jim Kelley wrote:
If traveling waves cannot interact in a linear medium, why
does Hecht say they do indeed interact?

It is exactly that kind of misleading terminology that has caused his
text to fall out of favor among many physics faculty.

:-) Please argue with Hecht if he is still alive or with
his ghost if he is not.

You really aren't qualified to speak on behalf of the field of optics,
Cecil.

Oh yes, instead of anything technical, we get an argumentum
ad verecundiam from you, the delusionary diversion gurus use
when they are sure they already know everything. Jim, it is
obvious that you don't even understand the intensity equations
in Born and Wolf. Wade through the S-Parameter analysis that
I have started and I will prove it to you.
--
73, Cecil http://www.w5dxp.com

On Apr 15, 2:03 am, Roy Lewallen wrote:

After a number more frustrating and unresolved collisions with reality,
he wisely quit and got a teaching job. I'm sure he did well in the
academic world.

He doesn't sound like anyone I know that does "well" in the academic
world.

ac6xg

Jim Kelley wrote:
On Apr 15, 2:03 am, Roy Lewallen wrote:
After a number more frustrating and unresolved collisions with reality,
he wisely quit and got a teaching job. I'm sure he did well in the
academic world.

He doesn't sound like anyone I know that does "well" in the academic
world.

:-) You must be an academic. :-)
--
73, Cecil http://www.w5dxp.com

On Sun, 15 Apr 2007 09:18:28 -0500, Cecil Moore wrote:

Walter Maxwell wrote:
... then coherent fields traveling in a transmission line must also interact,
interfere, or sum.

There is no doubt that Roy is absolutely wrong when he
asserts that coherent EM waves do not interact. Every
time we tune our antenna tuners to zero reflected energy,
we are causing EM waves to interact following the rules
of *linear* interference. All those waves, inductors,
and capacitors within the antenna tuner are operating
within a linear environment. If they weren't, we would
generate lots of harmonics.

Seems to me, the only valid point of argument is whether
a purely virtual impedance is a cause or an effect.

I quote from Terman, 1947 ed. page 109:
"The distance L1 from the load, and the length 'a' of the stub, are so chosen that the reflected wave produced
by the shunting impedance of the stub is equal in magnitude and opposite in phase to the reflected wave
existing on the line at this point as a result of the reflection from the load impedance ZL. Thus, although a
reflected wave is present in the length L1 because of the reflection from ZL, there is no reflected wave on
the generator side of the stub line as a result of the cancellation of the two reflected waves."

I maintain that Terman's statements above agree precisely with my statements introducing this thread, in which
I sum the reflection coefficients of the load and stub reflections to determine the cancellation of the two
reflected waves that result in the impedance match. Call it what you like, the condition at the stub point
totally re-reflects the two sets of reflected waves, but allows total passage of the source waves through the
junction of the main line and the stub.

Seems to me that the only disagreement with my original posting is whether the condition at the stub point can
be called a 'virtual' short circuit. If I'm outvoted on that term how about selecting another term for it that
everyone can agree on. I'm sure there is no disagreement on the wave analysis of the stub matching circuitry.

Walt, W2DU

Walter Maxwell wrote:
I quote from Terman, 1947 ed. page 109:
"The distance L1 from the load, and the length 'a' of the stub, are so chosen that the reflected wave produced
by the shunting impedance of the stub is equal in magnitude and opposite in phase to the reflected wave
existing on the line at this point as a result of the reflection from the load impedance ZL. Thus, although a
reflected wave is present in the length L1 because of the reflection from ZL, there is no reflected wave on
the generator side of the stub line as a result of the cancellation of the two reflected waves."

Wouldn't a short-circuit at the mouth of the stub keep
current from flowing in the stub?
--
73, Cecil http://www.w5dxp.com

Jim Kelley wrote:
On Apr 15, 2:03 am, Roy Lewallen wrote:

After a number more frustrating and unresolved collisions with reality,
he wisely quit and got a teaching job. I'm sure he did well in the
academic world.

He doesn't sound like anyone I know that does "well" in the academic
world.

You were lucky. He closely resembled the majority of my college professors.

Roy Lewallen, W7EL

Cecil Moore wrote:

...
:-) You must be an academic. :-)

There is a saying in the world, it exists for good reason; Those who can
DO, those who can't TEACH.

Since I am only a part-time instructor, I can do a little bit.

JS

On Apr 14, 9:52 pm, Cecil Moore wrote:

Does energy being redistributed in new directions really look
like a lack of interaction to you?

Roy is absolutely right, Cecil. Interact is a very poor choice of
terms in this discussion. Would you assert that photons can have an
effect on each other? The fact is, waves and photons can only
interact with matter. If the superposition of waves actually had an
effect on the waves themselves then interference patterns wouldn't
look the way they do. Think about it.

ac6xg

I've mentioned before that readers, like a group of triaged medical
patients, fall into three general categories:

1. Those who have made up their minds and won't have them changed no
matter what you say or what evidence you present;
2. Those who already agree with what you're saying;
3. Those who are willing to read what you say and can be convinced.

Posting for the benefit of groups 1 and 2 is a waste of time, because
there's no difference in anyone's belief or knowledge from the beginning
to the end of the discussion. The third group, however, is worth while.
Unfortunately, the active posters often are composed of the first two
groups, and I see in this discussion that's been entirely the case. So
we're left to hope that the lurkers are taking something away from this.
To the lurkers out the I hope you've read the postings, looked at the
evidence, and reached some conclusions. Better yet, I hope some of you
have been spurred to learn more about the topic, do some investigation
of your own from reputable sources, and gain a deeper understanding of
the fundamentals involved.

I see that my statements that waves don't interact with or reflect from
each other in a linear medium is already being morphed into claims that
I've denied that superposition happens, even though I've been careful to
distinguish the two. So one final request to the lurkers: Read what I
wrote, not interpretations of what I wrote.

I've tried to explain my point in about every way I know how, and
further postings would just become more repetitive. So I'll bow out at
this point, disappointed because I've been totally ineffectual at
communicating my point to the active posters, but with hope that some of
the lurkers have understood. And Walt, I'm especially disappointed that
I've been unable to explain to you what I mean, because I fear that the
interpretive error will detract from and reduce the credibility of your
otherwise exceptional and wonderful works.

Roy Lewallen, W7EL

On Apr 15, 6:53 am, Walter Maxwell wrote:
On Sun, 15 Apr 2007 19:23:56 +1000, Alan Peake
It is interesting to look at a single short pulse propagating along the
TL. At the stub point, the pulse must encounter a discontinuity in
impedance and therefore there will be a reflection. This can been seen
on a TDR. So there is a real reflection from a stub regardless of
whether or not it is a virtual short.
Alan
VK2ADB

I thank you for that, Alan, because, to continue, when the pulse is replaced with a sine wave, there is also a
reflection from the stub.

Hi Walt -

Begging your pardon, but don't TDR's examine the transient response of
a system, rather the steady state response?

ac6xg