On 16 Apr 2007 14:29:01 -0700, "K7ITM" wrote:

In my mind I was qualifying it as being waves
propagating in the same direction, since the discussion centers around
propagating EM cancelling out in a finite (non-zero) volume, and as
far as I know, there hasn't been anyone suggesting that waves on a
line in opposite directions cancel over a non-zero distance.

Hi Tom,

Then the challenge devolves to a self-fulfilling proposition (which
may be your point at this turn) as it requires two sources to occupy
the same point.

The "Magic T" as I know it is most certainly a physical interface in
the line. It's a four-port network. I'm surprised you'd even think
to mention it as a counter-example. Next you'll be saying that a
Michaelson interferometer (also a 4-port, where one port is commonly
terminated in a full reflection) isn't a physical interface...

Again, you have a self-fulfilling proposition. This has nothing to do
with obtaining a condition of interference, but about filling an
impossible constraint.

Consider, you do not mention where the line begins (or ends) or
otherwise constrain this physically, and yet you can easily dismiss an
example out of hand. It seems it is up to the respondent to feel out
these constraints, much like reading Braille on a waffle iron.

Any issue of "interface" as has been offered by quotes from Terman, or
otherwise bandied about in discussion is that the "interface" presents
a disturbance (a step-wise shift in characteristic Z). There is
nothing, per se, about an interface that disqualifies it from the
study of interference as it is quite obvious power must enter through
a system through some interface.

The "Magic T" and similar devices make every effort to present a
non-perturbing environment to the transmission of waves, otherwise
their utility would be nil.

Also, the "Magic T" offers an excellent solution to your first issue
in that it does present two sources combining at one point whereby
there is total null following. There is absolutely nothing about the
"Magic T" that disturbs the field with discontinuities and would
appear (from the perspective of the energy) as continuous.

Fiber optics are TEM lines??? I find lots of references to the
contrary. Can you give me any showing that they are?

I have to admit I haven't paid any attention to anything you've posted
about Soliton waves. (Do they differe from soliton waves?) Are you
saying they propagate as TEM waves in a linear medium but don't follow
the same rules with respect to linearity that other TEM waves do? Do
they not behave at boundaries in the same way that other waves do?

OK, this is foreign turf for you. I don't think offering a course on
Solitons, fiber optics and TEM waves will change the discussion here.
You asked for examples and they were provided. Do you want to further
constrain to RF below a certain frequency?

How do you create one in a piece of coax? I'm afraid I don't see in
what way they might be an example of something that propagates as a
TEM wave but doesn't obey the rules I'm used to seeing TEM waves obey.

So we are now confined to coax? The refinement of constraints is
painting examples into a corner as we progress.

I don't trust claims, and measurements proving them even less so. If
this statement above is about perfection; then, again, the last word
has yet to be made such that accuracy can be guaranteed. [Even Ohm's
law isn't accurate. Hence any power statement made in regard to it
fails at some digit to the right of the decimal.]

No, it's about practicality.

Practicality when your post is littered with "perfect?" You have
rebutted every practical example offered! Do we now constrain what
practical means or is this about studying the effects of interference?

Convince me that calculations based
primarily on power (or energy) rather than on voltage and current
offer me something useful, with respect to TEM lines, and I might have
a closer look at them.

I presume this challenge is to the general readership.

73's
Richard Clark, KB7QHC