Constructive interference in radiowave propagation
 

Owen Duffy wrote:
It is a leap to move from "can be thought of as power" or "has the
dimension of power" to your statement (which you attribute to HP AN95-1)
"The beauty of an S-Parameter analysis is that if one squares the
normalized voltages, one gets power." Did AN95-1 state clearly that which
you suggest?

The answer is "yes, they did." But, if you insist, I am willing to
change what HP said to "one gets the dimensions of power, i.e.
joules/second." As an engineer, I am content with getting close
enough but I am always agreeable to accommodating the purists.

Nowhere in Chapter 1 of AN154 do they perform alegebraic operations on
power, the chapter is full of expressions, but they do not use |Sxx|^2.

How about Chapter 2? :-)

I will have to check out that Ap Note. In the meanwhile, maybe
you should take a look at Ap Note 95-1 from which I will quote
one example (there are others) from page 17:

|s11|^2 = Power reflected from the network input divided by Power
incident on the network input. Please adjust your thinking
to agree with HP's.

So not you are superposing power to "yield" a resultant power.

My native language is American English but I cannot parse that
statement. Care to try again, maybe in the Queen's English? :-)

Power density can be added using the scalar intensity, irradiance,
or Poynting vector equations, but POWER CANNOT BE SUPERPOSED!!!
I don't know how many times I have to repeat that statement.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Owen Duffy wrote:
So now you are superposing power to "yield" a resultant power.

I see you corrected your English. :-) The answer is NO, powers
cannot be superposed. There is a specialized equation for adding
powers and it is *NOT* a superposition equation. Born and Wolf
call it the "total intensity" equation with an included
"interference" term. Their words, not mine.

The equation also appears in Dr. Best's QEX article of Nov/Dec
2001 and in "Optics", by Hecht.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
Gene Fuller wrote:
quoting Born & Wolf:
"However, when the definition has been applied cautiously, in
particular for averages of small but finite regions of space or time,
no contradictions with experiments have been found. We shall therefore
accept the above definition in terms of the Poynting vector of the
density of the energy flow."

There's the meat of the quote as far as transmission lines
are concerned. Given that transmission lines are "small but
finite regions of space or time", and since there are only
two possible directions in a transmission line, Born and
Wolf seem to give us permission to do exactly what you
are complaining about. Your concerns about light waves
in three dimensional free space just don't exist for the
primarily single dimensional "space" in a transmission line.
Ideally, the power density exists only between the inner and
outer conductors of the coax.

It does not make any sense to simply add and subtract Poynting vectors
in elementary fashion and expect to get correct results.

Born & Wolf's own words in the quote above provided by you
contradict that assertion.


Cecil,

You conveniently chopped out the part of the B&W quote that matters. You
continue to claim that energy associated with each of the myriad of wave
components that exist at the point of interest must be reconciled. The
correct application of the Poynting theorem, as noted in the full B&W
quote, says that your requirement is not correct. Only the net energy
flow into that small integration volume has any physical reality.

Unless there is a source or sink at the point of interest, the net
energy flow will be exactly zero. Further analysis is futile.
Conservation of energy, specifically the Poynting theorem, does not
support you or anyone else who tries to atomize the waves in an attempt
to balance energy contribution from individual wave components. You are
on your own.

By the way, a very similar statement about the application of Poynting
vectors appears in Classical Electrodynamics by Jackson. This is not
some strange interpretation by a single author.

73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
Gene Fuller wrote:
Why don't you simply stop being such a nitwit. I understand perfectly
what the Java applet is and is not. S-parameters are not a new branch
of science. No one is confused except you.

Before I explained it to you, you obviously had no
clue what that java script represented since you
said it was impossible. Not only is it possible,
it happens every time someone adjusts an antenna
tuner for a match.

Cecil,

By the way, the "nitwit" comment was in reference to dragging global
warming into the discussion. Just a slight bit of a diversion.

8-)

73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Gene Fuller wrote:
You conveniently chopped out the part of the B&W quote that matters.

No, I quoted the part of the B&W quote that matters.

Further analysis is futile.

Gene, are you a Borg?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Gene Fuller wrote:
By the way, the "nitwit" comment was in reference to dragging global
warming into the discussion. Just a slight bit of a diversion.

Speaking of which, the global warming gurus are predicting
global chaos. The fact is that ~130K years ago, the Earth
began 10K years of global warming followed by an ice age.
The temperature 120K years ago averaged two degrees hotter
than it is today. 18K years ago, we began another 10K year
period of global warming that brought us out of the last
ice age and peaked 8K years ago two degrees hotter than it
is today. For the past 8K years, the Earth has been ever
so slowly slipping into another ice age. Al Gore knows
just about as much about global warming as you do about
destructive interference. Are you a Democrat? :-)
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 15, 12:56 pm, Cecil Moore wrote:
Jim, I challenge you to find anything wrong with this S-
Parameter analysis.
It follows exactly Born and Wolf's
intensity equations for constructive interference when
the phase angle between a1 and a2 is 180 degrees and
their magnitudes are equal.

Profound. Wouldn't it be strange if other texts had similar ideas
too?...

Let us know when HP gets around to ammending its S-Parameter treatise
to include the 4th Mechanism of Reflection.

ac6xg

Constructive interference in radiowave propagation
 

Jim Kelley wrote:
Let us know when HP gets around to ammending its S-Parameter treatise
to include the 4th Mechanism of Reflection.

Please wade through the S-Parameter analysis with me,
see for yourself, and suggest an alternative. The
Florida State web page says the energy involved in
wave cancellation is redistributed "somehow". Wave
cancellation is obviously not a simple reflection
from an impedance discontinuity because it does not
obey the reflection rules.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 16, 5:34 am, Cecil Moore wrote:
Jim Kelley wrote:
Let us know when HP gets around to ammending its S-Parameter treatise
to include the 4th Mechanism of Reflection.

Please wade through the S-Parameter analysis with me,
see for yourself, and suggest an alternative. The
Florida State web page says the energy involved in
wave cancellation is redistributed "somehow". Wave
cancellation is obviously not a simple reflection
from an impedance discontinuity because it does not
obey the reflection rules.
--
73, Cecil http://www.w5dxp.com

Hi Cecil,

I really do appreciate your courteous and patient offer. But in fact,
you have already waded us through that so many times it's kinda funny
that you hope it will somehow turn out differently this time. I don't
understand why the S-parameter analysis is controversial - unless
perhaps you're doing something fanciful with it. If not, it's no lo
contendre. The point of contention is only one or two particular
aspects of your energy analysis. By that I mean _your_ energy
analysis, not Eugene Hechts interference equations (and poor choices
of terms), not B&W's Poynting vector discussion, and not the Hewlett-
Packard s-parameter application note. Although you do frequently
quote, paraphrase, and presume to speak on their behalf, those people
do not post your ideas to rec.radio.amateur.antenna.

73, Jim AC6XG

Constructive interference in radiowave propagation
 

On Apr 15, 7:49 am, Gene Fuller wrote:
....

Cecil,

I pointed out a few days ago that the FSU Java applet you lean on so
heavily these days is a simple tutorial device designed by a grad
student and a programmer. As shown, it is physically impossible, since
there is no mechanism in place to cause the waves to suddenly jump
together and interfere.

It is a useful picture showing how sine waves with differing phases add
together; no more and no less. It is a simple matter of mathematics. It
is not a new discovery in the world of RF or optics.

73,
Gene
W4SZ

I have yet to see Cecil, or anyone else, post an example of how waves
can become perfectly collinear, except at an interface: a
discontinuity in a transmission line, a partially-reflecting surface
in an interferometer, ... -- a physical interface of some sort.

I have yet to see Cecil, or anyone else, post an example of perfectly
collinear waves that perfectly cancel over some small finite volume
which do not also cancel perfectly at all points up to their point of
origin: a physical interface. In other words, lacking that example,
I see NO physical evidence that those waves exist beyond that "point
of origin." Specifically, I have not seen an example of a uniform TEM
line on which it is supposed that two waves cancel perfectly over some
distance, but over some other length on the same line with no
interposed interfaces, the two do not perfectly cancel.

I have yet to see Cecil, or anyone else, post an example wherein the
behaviour of a uniform, linear TEM transmission line is not adequately
explained by the propagation constant of the line, the concept that Vf/
If=-Vr/Ir=Zo, Vtotal=Vf+Vr, and Itotal=If+Ir, and the boundary
conditions at any transitions or interfaces.

Whether or not any claims about power and energy formulas are accurate
or not, I don't know. I'd have to be convinced they're actually
useful before I looked at them more closely. So far, I've not been
convinced of their utility. But then maybe I'm just slow. I could
never see how the current at two ends of a wire (with no other
conductive paths between the ends) could be different unless the wire
in between was storing or giving up charge, either, and I was LAUGHED
AT and told that was just flat-out wrong. The laughing didn't seem to
help; I still don't see it.

When I brought up that applet a few days ago, the same thing jumped
out at me, and gave ME a good laugh. Yes, it shows waves cancelling,
but it never shows how they got there.

Cheers,
Tom

This posting (c) 2007; it may be quoted only in its entirety.

Constructive interference in radiowave propagation
 

On 16 Apr 2007 10:07:55 -0700, "K7ITM" wrote:

I have yet to see Cecil, or anyone else, post an example of how waves
can become perfectly collinear, except at an interface: a
discontinuity in a transmission line, a partially-reflecting surface
in an interferometer, ... -- a physical interface of some sort.

Two sources impinging upon each other? If we take a specialized
example of lasers, their being bore sight in opposition. If we take
two antennas, where their -ahem- waves meet, again in opposition.
Nothing physical but the sources are required. As for perfection....

I have yet to see Cecil, or anyone else, post an example of perfectly
collinear waves that perfectly cancel over some small finite volume
which do not also cancel perfectly at all points up to their point of
origin: a physical interface. In other words, lacking that example,
I see NO physical evidence that those waves exist beyond that "point
of origin." Specifically, I have not seen an example of a uniform TEM
line on which it is supposed that two waves cancel perfectly over some
distance, but over some other length on the same line with no
interposed interfaces, the two do not perfectly cancel.

This one is extremely simple to reveal. Those familiar with
microwaves would immediately sputter "Magic T!" Tom, if you have not
seen this offered in several many posts by me, it stands to reason you
must have filters set (but how is it you are reading this?). Of
course, this like the "rat race" coupler (or hybrid ring) all share
the same dynamics. However, for the "Magic T" the cancellation port
is fed by two apparent sources wherein their phases combine to a null
(given the appropriate phases, of course) at this "point of origin."
This may beg what is meant by interface as the "Magic T" is replete in
transmission line arms - however, all are identical in characteristic
Z (a uniformity), all can be Zload matched (a uniformity which then
discards the useful illustration of cancellation), and all are TEM (a
uniformity). As for perfection....

I have yet to see Cecil, or anyone else, post an example wherein the
behaviour of a uniform, linear TEM transmission line is not adequately
explained by the propagation constant of the line, the concept that Vf/
If=-Vr/Ir=Zo, Vtotal=Vf+Vr, and Itotal=If+Ir, and the boundary
conditions at any transitions or interfaces.

Hmmm, those filters must have been a brick wall: In times past I've
offered Soliton waves in fiber optics (TEM lines, of course) wherein
there is no dispersion as would be typically found. This, of course,
stretches the concept of "linear" TEM lines insofar as NONE are! So
much for perfection, or practicality....

Whether or not any claims about power and energy formulas are accurate
or not, I don't know. I'd have to be convinced they're actually
useful before I looked at them more closely. So far, I've not been
convinced of their utility. But then maybe I'm just slow. I could
never see how the current at two ends of a wire (with no other
conductive paths between the ends) could be different unless the wire
in between was storing or giving up charge, either, and I was LAUGHED
AT and told that was just flat-out wrong. The laughing didn't seem to
help; I still don't see it.

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.]

When I brought up that applet a few days ago, the same thing jumped
out at me, and gave ME a good laugh. Yes, it shows waves cancelling,
but it never shows how they got there.

When a sudden galactic Gamma burst hit us in the past, it too was of
unknown origin (meaning no one knew how they got here). Later, we put
up satellites to warn detectors an event was coming so we could
roughly triangulate any new Gamma burst. One such event suggested a
galactic black hole. Back of the envelope calculations have suggested
similar Gamma burst sources (millions of light years away, but bore
sight on us) could obliterate life in an entire solar systems in the
space of milliseconds. Some might call that canceling waves - or a
cosmic laugh.

OK, so admittedly all responses above entail exotic, rare, or strained
examples. Some are ordinary within the context of experience. If all
of your provisos were combined, then yes, nothing would satisify by
virtue of a self-fulfilling definition.

Copy made in accordance with "Fair Use."

73's
Richard Clark, KB7QHC

Constructive interference in radiowave propagation
 

Cecil Moore wrote:


Partially reflective surfaces cannot, by themselves,
reflect 100% of the incident energy.

They can and certainly do when no energy is passing through the
reflecting surface. In such a case the only energy conveyed by the
wave is that which is reflected. The 100% number comes not in a
single bounce, or from a single wavefront. But I don't expect you to
understand this.

The waves existed along with their energy components before
they were canceled.

I believe your misunderstanding probably lies somewhere within that
statement. It does not convey concise meaning.

What happens to those energy components
after the waves are canceled.

Where there are waves, there is energy. Where there are no waves,
there is no energy. Show me the canceled waves.

73, Jim AC6XG

Constructive interference in radiowave propagation
 

On Apr 16, 12:19 pm, Richard Clark wrote:
On 16 Apr 2007 10:07:55 -0700, "K7ITM" wrote:

I have yet to see Cecil, or anyone else, post an example of how waves
can become perfectly collinear, except at an interface: a
discontinuity in a transmission line, a partially-reflecting surface
in an interferometer, ... -- a physical interface of some sort.

Two sources impinging upon each other? If we take a specialized
example of lasers, their being bore sight in opposition. If we take
two antennas, where their -ahem- waves meet, again in opposition.
Nothing physical but the sources are required. As for perfection....

Best stick with transmission lines, and not lasers, but yes, you're
absolutely right. 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. I should
have explicitly stated that qualification, especially in this group.
I should, of course, also specified that all this propagation is
assumed to be in a perfectly linear medium, so someone can now offer a
transmission line made from wire wound around a ferrite core, shunted
by varicap diodes, and we'll have a nice nonlinear TEM line that all
sorts of strange things can happen on.

I have yet to see Cecil, or anyone else, post an example of perfectly
collinear waves that perfectly cancel over some small finite volume
which do not also cancel perfectly at all points up to their point of
origin: a physical interface. In other words, lacking that example,
I see NO physical evidence that those waves exist beyond that "point
of origin." Specifically, I have not seen an example of a uniform TEM
line on which it is supposed that two waves cancel perfectly over some
distance, but over some other length on the same line with no
interposed interfaces, the two do not perfectly cancel.

This one is extremely simple to reveal. Those familiar with
microwaves would immediately sputter "Magic T!" Tom, if you have not
seen this offered in several many posts by me, it stands to reason you
must have filters set (but how is it you are reading this?). Of
course, this like the "rat race" coupler (or hybrid ring) all share
the same dynamics. However, for the "Magic T" the cancellation port
is fed by two apparent sources wherein their phases combine to a null
(given the appropriate phases, of course) at this "point of origin."
This may beg what is meant by interface as the "Magic T" is replete in
transmission line arms - however, all are identical in characteristic
Z (a uniformity), all can be Zload matched (a uniformity which then
discards the useful illustration of cancellation), and all are TEM (a
uniformity). As for perfection....

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...


I have yet to see Cecil, or anyone else, post an example wherein the
behaviour of a uniform, linear TEM transmission line is not adequately
explained by the propagation constant of the line, the concept that Vf/
If=-Vr/Ir=Zo, Vtotal=Vf+Vr, and Itotal=If+Ir, and the boundary
conditions at any transitions or interfaces.

Hmmm, those filters must have been a brick wall: In times past I've
offered Soliton waves in fiber optics (TEM lines, of course) wherein
there is no dispersion as would be typically found. This, of course,
stretches the concept of "linear" TEM lines insofar as NONE are! So
much for perfection, or practicality....

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?
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.


Whether or not any claims about power and energy formulas are accurate
or not, I don't know. I'd have to be convinced they're actually
useful before I looked at them more closely. So far, I've not been
convinced of their utility. But then maybe I'm just slow. I could
never see how the current at two ends of a wire (with no other
conductive paths between the ends) could be different unless the wire
in between was storing or giving up charge, either, and I was LAUGHED
AT and told that was just flat-out wrong. The laughing didn't seem to
help; I still don't see it.

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. 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 have tools that give me an accurate picture
of the distribution of voltage and current on a line as a function of
time, at any point along the line. From these, I can find the power
delivered to loads (a useful, practical quantity that I do care
about). I can calculate the power dissipated as heat as a function of
distance along the line, which in some cases is useful and practical
information. I can easily calculate the steady-state load impedance
presented to a source, given a particular line and load, and again
that's useful, practical information. Give me a practical reason for
caring about "power" in "forward" and "reverse" waves on a TEM line.

When I brought up that applet a few days ago, the same thing jumped
out at me, and gave ME a good laugh. Yes, it shows waves cancelling,
but it never shows how they got there.

When a sudden galactic Gamma burst hit us in the past, it too was of
unknown origin (meaning no one knew how they got here). Later, we put
up satellites to warn detectors an event was coming so we could
roughly triangulate any new Gamma burst. One such event suggested a
galactic black hole. Back of the envelope calculations have suggested
similar Gamma burst sources (millions of light years away, but bore
sight on us) could obliterate life in an entire solar systems in the
space of milliseconds. Some might call that canceling waves - or a
cosmic laugh.

I don't know what that was all about, but it doesn't matter anyway,
since I'm only a figment of Cecil's imagination.

Cheers,
Tom


OK, so admittedly all responses above entail exotic, rare, or strained
examples. Some are ordinary within the context of experience. If all
of your provisos were combined, then yes, nothing would satisify by
virtue of a self-fulfilling definition.

Copy made in accordance with "Fair Use."

73's
Richard Clark, KB7QHC

Constructive interference in radiowave propagation
 

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

Constructive interference in radiowave propagation
 

Jim Kelley wrote:
I really do appreciate your courteous and patient offer. But in fact,
you have already waded us through that so many times it's kinda funny
that you hope it will somehow turn out differently this time.

We have never discussed the point in the analysis that
I would like to discuss next. It will be brand new
territory. What have you got to lose?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 16, 3:38 pm, Richard Clark wrote:
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.

Well, maybe I'm mistaken, but I was under the impression that there
was someone around here who was promoting the idea that two waves
propagating in a linear medium could cancel over some non-zero finite
volume, but not cancel everywhere along their path, even though that
path was uninterrupted by any discontinuities in the medium. Maybe
I'm mistaken, but I was under the impression that there was someone
around here who was promoting the idea that calculations based on
power rather than on voltage and current in a TEM transmission line
offered some inherent value. I posted my original, "I have yet to
see...," statements as a way of saying that I'm not convinced about
the truth of either of those ideas, and it would go a long ways toward
convincing me if someone posted examples. I'm still waiting. I still
don't have a reference that a fiber optic cable is a TEM transmission
line, though I have others that say that it's not. I still don't have
information on whether a soliton wave can propagate in a linear
medium, though I have references that say it is a non-linear
phenomenon that occurs in non-linear media. If you can convince me
that a wavefront coming to a Magic T doesn't see it as an impedance
discontinuity, we could perhaps post more about that--or not.

But so far, your responses make me think you don't disagree with my
implicit suggestions: that it's impossible to distinguish between the
condition of two cancelled waves that somehow still exist (huh?) and
the condition of no wave at all; and that there's precious little
value in doing calculations based on "forward power" and "reverse
power" in TEM lines--qualify that if you want by limiting it to the
frequency range where we find it relatively easy to express what's
going on in terms of voltage and current. That seems a reasonable
qualification in this newsgroup.

Beyond that, you're of course welcome to go off on whatever tangents
you wish. Basenote drift is the expected norm here; I engage in it
all the time myself.

And I still don't exist; I'm only a figment of Cecil's imagination.

Cheers,
Tom

Constructive interference in radiowave propagation
 

K7ITM wrote:
I have yet to see Cecil, or anyone else, post an example of how waves
can become perfectly collinear, except at an interface: a
discontinuity in a transmission line, a partially-reflecting surface
in an interferometer, ... -- a physical interface of some sort.

Please stop the unfair innuendo. You have yet to see me say that
waves can become perfectly collinear, except at an impedance
discontinuity. I have gone out of my way to say reflections
happen only at a physical impedance discontinuity. Waves become
perfectly collinear because of reflections at a physical
impedance discontinuity. I don't know how you can possibly
be confused regarding what I said.

I have yet to see Cecil, or anyone else, post an example of perfectly
collinear waves that perfectly cancel over some small finite volume
which do not also cancel perfectly at all points up to their point of
origin: a physical interface.

Please stop the unfair innuendo. You have yet to see me say that
waves do not cancel immediately at the point of reflection. That's
because they are canceled immediately, like delta-t, after the
reflection. They exist for such a short time that they cannot even
be seen on an o'scope. There existence can only be deduced because
if they didn't exist, nothing would happen at a physical impedance
discontinuity.

I have yet to see Cecil, or anyone else, post an example wherein the
behaviour of a uniform, linear TEM transmission line is not adequately
explained by the propagation constant of the line, the concept that Vf/
If=-Vr/Ir=Zo, Vtotal=Vf+Vr, and Itotal=If+Ir, and the boundary
conditions at any transitions or interfaces.

Not sure what you are getting at. All those waves are associated
with joules/second. I am not trying to replace anything. I am
merely adding an energy analysis to the voltage analysis. The
voltage analysis remains exactly the same as it has always been.

In an S-parameter analysis, if you square any of the normalized
voltage terms, you get joules/sec (power). If you square any
of the voltage reflection or transmission coefficients, you
get the power reflection coefficient. The S-Parameter analysis
seems to have been designed with power in mind. The HP Ap Note
says, "The previous four equations show that s-parameters are
simply related to power gain and mismatch loss, quantities
which ARE OFTEN OF MORE INTEREST than the corresponding
voltage functions." What do you suppose HP meant by, "ARE
OFTEN OF MORE INTEREST" regarding the power components?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Jim Kelley wrote:
They can and certainly do when no energy is passing through the
reflecting surface. In such a case the only energy conveyed by the wave
is that which is reflected. The 100% number comes not in a single
bounce, or from a single wavefront. But I don't expect you to
understand this.

I fully understand it Jim. I'm willing to take the time
to explain it to you with s-parameter examples, but you
have refused to listen. One wonders what you are afraid
of and what you have to lose except face.

Where there are waves, there is energy. Where there are no waves, there
is no energy. Show me the canceled waves.

b1 = s11(a1) + s12(a2) = 0

s11(a1) and s12(a2) are the two waves that are being
canceled. They exist sum to zero. Have you ever done
any phasor or vector addition?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Cecil Moore wrote:


We have never discussed the point in the analysis that
I would like to discuss next. It will be brand new
territory. What have you got to lose?

Time, patience, energy......

As Jack Nicholson once said, "I'd rather stick needles in my eyes".

ac6xg

Constructive interference in radiowave propagation
 

K7ITM wrote:
No, it's about practicality. 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.

Assume you are dealing with light waves in free space
instead of RF waves in a transmission line. Would you
then find intensity (power density) calculations useful?
That's why optical physicists find them so useful.

Tom, are you familiar with an s-parameter analysis?

If so, it seems to me that b1 = s11(a1) + s12(a2) = 0
represent two wave components that immediately cancel
to zero when superposed at the impedance discontinuity.
Would you care to comment?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

K7ITM wrote:
Well, maybe I'm mistaken, but I was under the impression that there
was someone around here who was promoting the idea that two waves
propagating in a linear medium could cancel over some non-zero finite
volume, but not cancel everywhere along their path, even though that
path was uninterrupted by any discontinuities in the medium.

Would you please name the person who said such. It certainly
was NOT me. The waves involved in the cancellation are
canceled so fast that they cannot be viewed on an o'scope.
But if they didn't exist, nothing would happen at an
impedance discontinuity.

Take the s-parameter equation, for instance.

b1 = s11(a1) + s12(a2) = 0

If s11(a1) doesn't exist, then s11 and/or a1 must not exist
either. But s11 and a1 can be measured. So if s11 and a1
exist, does s11(a1) exist only to be canceled or did it
never exist. If s11(a1) never existed, what the heck is
an s-parameter analysis good for?

Maybe
I'm mistaken, but I was under the impression that there was someone
around here who was promoting the idea that calculations based on
power rather than on voltage and current in a TEM transmission line
offered some inherent value.

An energy analysis is not supposed to replace a voltage analysis
but is supposed simply to settle the question, Where does the
energy go? If we assume that in a Z0 transmission line, that
Vfor^2/Z0 = forward joules/sec and Vref^2/Z0 = reflected joules/sec,
the energy analysis falls out from the voltage analysis.

If you don't care where the energy goes, that's cool, but some
of us, like Bruene and Maxwell, do care and have been arguing
about it for decades.

To keep an energy analysis from falling out from the voltage
analysis, we have been told that reflected waves don't exist,
and if they did exist, they would be devoid of energy content.
"I have yet to see" an EM wave that can exist devoid of
energy content.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
K7ITM wrote:
No, it's about practicality. 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.

Assume you are dealing with light waves in free space
instead of RF waves in a transmission line. Would you
then find intensity (power density) calculations useful?
That's why optical physicists find them so useful.

Tom, are you familiar with an s-parameter analysis?

If so, it seems to me that b1 = s11(a1) + s12(a2) = 0
represent two wave components that immediately cancel
to zero when superposed at the impedance discontinuity.
Would you care to comment?

Cecil,

Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Jim Kelley wrote:
Cecil Moore wrote:
We have never discussed the point in the analysis that
I would like to discuss next. It will be brand new
territory. What have you got to lose?

Time, patience, energy......

I'm willing to furnish the bulk of the time and energy.
All you need to do is read my s-parameter analysis and
show me where I am wrong.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

Gene Fuller wrote:
Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

All that may be true, Gene. But don't Maxwell's
equations obey the superposition principle?
What does Maxwell say happens when we superpose
two EM waves out of phase such that destructive
interference occurs? What does Maxwell say
about the energy "lost" to destructive
interference? Where did it go?

Are intensity calculations utterly inadequate
for exploring the details of low resolution
transmission lines? :-) If the intensity
(power) calculations enumerated in the s-
parameter analysis description are utterly
inadequate, why are they used so often?
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On 16 Apr 2007 17:50:10 -0700, "K7ITM" wrote:

On Apr 16, 3:38 pm, Richard Clark wrote:
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.

Well, maybe I'm mistaken, but I was under the impression that there
was someone around here who was promoting the idea that two waves
propagating in a linear medium could cancel over some non-zero finite
volume, but not cancel everywhere along their path, even though that
path was uninterrupted by any discontinuities in the medium.

Hi Tom,

'T'warn't me.

Maybe
I'm mistaken, but I was under the impression that there was someone
around here who was promoting the idea that calculations based on
power rather than on voltage and current in a TEM transmission line
offered some inherent value.

'T'warn't me.

I posted my original, "I have yet to
see...," statements as a way of saying that I'm not convinced about
the truth of either of those ideas, and it would go a long ways toward
convincing me if someone posted examples. I'm still waiting.

'T'was me.

I still
don't have a reference that a fiber optic cable is a TEM transmission
line, though I have others that say that it's not.

That example of the non-TEM fiber optic would be rare species indeed.
I've seen them, but that hardly constitutes the sole species of the
breed.

I still don't have
information on whether a soliton wave can propagate in a linear
medium, though I have references that say it is a non-linear
phenomenon that occurs in non-linear media.

Of course it can propagate in a linear medium. Solitons were first
reported in linear media - water - something like one hundred seventy
years ago. Solitons can induce non-linearity in otherwise linear
media. Solitons also interact in collision with a phase shift
afterwards. Solitons have been applied to data transmission in fiber
optics for a dozen years or more.

Your references are pretty sparse.

If you can convince me
that a wavefront coming to a Magic T doesn't see it as an impedance
discontinuity, we could perhaps post more about that--or not.

Consult Terman. He is quite compelling when it comes to describing
microwave plumbing. This hardly constitutes more than 4 pages total
reading, if you choose to move on beyond the first page of discussion.

But so far, your responses make me think you don't disagree with my
implicit suggestions:

True enough to a point.

that it's impossible to distinguish between the
condition of two cancelled waves that somehow still exist (huh?)

The elliptical huh? seems to be a curious toe in the water for many
here. Strange how a concept draws borders around energy it to make it
"disappear" simply because both contributions cancel. This is like
saying gravity disappears on a 1 square inch patch of earth when the
falling apple has come to rest on the ground. This is also akin to
the misnomer of zero-gravity environment of the astronauts in the
space shuttle.

For example (drawing away from G and towards V), if I were to place
two batteries in series opposition
- + + -
and connect a load to the two free terminals; sure, no current would
flow because there is no potential difference, but that numerical
combination doesn't make the batteries disappear. Yes, the condition
is indistinguishable from a load floating in null space, but we have a
priori knowledge of existing energy that informs us otherwise. If we
choose to be ignorant of the knowledge in that specific locality, the
map of all phase combinations around it will certainly bring it to our
attention again.

Beyond that, you're of course welcome to go off on whatever tangents
you wish. Basenote drift is the expected norm here; I engage in it
all the time myself.

The point of my going into a basenote drift is to present examples
that demonstrate what is necessary to answer your objections (like
providing two sources at one point that cancel on one side, but exist
independently on the other side of an interface). If those who
present their "theories" cannot meet these demonstrated
characteristics, then it is reasonable to reject their claims barring
their offering treatments that are equally compelling.

73's
Richard Clark, KB7QHC

Constructive interference in radiowave propagation
 

Cecil Moore wrote:
Gene Fuller wrote:
Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

All that may be true, Gene. But don't Maxwell's
equations obey the superposition principle?
What does Maxwell say happens when we superpose
two EM waves out of phase such that destructive
interference occurs? What does Maxwell say
about the energy "lost" to destructive
interference? Where did it go?

Are intensity calculations utterly inadequate
for exploring the details of low resolution
transmission lines? :-) If the intensity
(power) calculations enumerated in the s-
parameter analysis description are utterly
inadequate, why are they used so often?

Cecil,

Changing the topic again? So soon?

You made a claim about optical physicists. I pointed out that your claim
is simply not correct. You then start babbling about low resolution
transmission lines. What a surprise!

You seem to be going back and forth about the utility of bringing optics
into the discussion on antennas and transmission lines. I doubt that
many here would expect different physical principles to apply to the two
wavelength regimes. I wonder if there might be a practical reason why
the preferred computational techniques are somewhat different?

The physics does not change, but the mathematical convenience does
change. Yes, that seems to be a recurring theme from me.

8-)

73,
Gene
W4SZ

Constructive interference in radiowave propagation
 

Gene Fuller wrote:
Changing the topic again? So soon?

No, just asking questions, Gene, like any grasshopper
worshiping at the feet of a guru is supposed to.
Please stop avoiding the questions with non-technical
diversions.

Do Maxwell's laws abide by the superposition principle?
It is a question with a simple yes/no answer. If they
do abide by the superposition principle, the forward
wave and reflected wave can be analyzed separately
and then superposed. Every individual wave component,
e.g. s11(a1), s12(a2), s21(a2), and s22(a2) can be
analyzed separately and then superposed. What do you get
when you apply Maxwell's equations to s11(a1)? Hopefully,
the same voltage, current, and energy as any other valid
analysis. If not, there's a distinct problem that needs
to be solved.

You made a claim about optical physicists. I pointed out that your claim
is simply not correct.

And I asked you to explain why it is not correct and
you very carefully avoided answering. One wonders why.

I doubt that
many here would expect different physical principles to apply to the two
wavelength regimes.

My point exactly, Gene. The two fields should agree in
every way (except lingo). If you switch from voltage and
current to EM fields, nothing should change. But when you
admit that, you are forced to admit that voltages and
currents associated with EM waves are bound by a set of
restrictions, one of them being that they must at all
times, travel at c(VF) and cannot, by definition, stand
still as long as they exist as EM waves.

Intensity, irradiance, and Poynting vectors are just
different names for the same physical phenomenon. To
assert that power density in a transmission line doesn't
obey the same rules as light intensity is just nonsense.
The energy content of component waves has been known for
decades in the field of optics and it applies just as
well to RF waves as it does to light waves.

The physics does not change, but the mathematical convenience does
change.

My point exactly! No matter what the mathematical convenience,
(except for the lingo) the two fields should agree in every way.
When they appear to disagree, there is a contradiction somewhere.
Seems to me, in the quest to fit EM waves into the voltage and
current mold, some have forgotten that EM waves are not DC.
--
73, Cecil http://www.w5dxp.com

Constructive interference in radiowave propagation
 

On Apr 17, 12:33 am, Richard Clark wrote:
On 16 Apr 2007 17:50:10 -0700, "K7ITM" wrote:
....
I still
don't have a reference that a fiber optic cable is a TEM transmission
line, though I have others that say that it's not.

That example of the non-TEM fiber optic would be rare species indeed.
I've seen them, but that hardly constitutes the sole species of the
breed.

So give me a reference already. I find lots of references, including
ones that explain the propagation, that talk about TM, TE, hybrid, and
even quasi-TEM mode propagation in a fiber. What boundary conditions
are there in an optical fiber that give TEM mode?


I still don't have
information on whether a soliton wave can propagate in a linear
medium, though I have references that say it is a non-linear
phenomenon that occurs in non-linear media.

Of course it can propagate in a linear medium. Solitons were first
reported in linear media - water - something like one hundred seventy
years ago.

Solitons can induce non-linearity in otherwise linear
media. Solitons also interact in collision with a phase shift
afterwards. Solitons have been applied to data transmission in fiber
optics for a dozen years or more.

Your references are pretty sparse.

Yours seem non-existent. Mine at least did a good job explaining the
phenomena.

From Wikipedia, for example, about solitons:
"The stability of solitons stems from the delicate balance of
"nonlinearity" and "dispersion" in the model equations. Nonlinearity
drives a solitary wave to concentrate further; dispersion is the
effect to spread such a localized wave. If one of these two competing
effects is lost, solitons become unstable and, eventually, cease to
exist. In this respect, solitons are completely different from "linear
waves" like sinusoidal waves. In fact, sinusoidal waves are rather
unstable in some model equations of soliton phenomena. Computer
simulations show that they soon break into a train of solitons."

There is specific mention of the Kerr effect--a nonlinearity in
optical media that support soliton transmission. One of the
references I saw specifically said that solitons are solutions to non-
linear differential equations. Since the equations governing the
behaviour of waves derive from the properties of the propagation
medium, I expect that any medium that can propagate a soliton is
nonlinear. Another reference specifically addressed the nonlinearity
of water as a transmission medium, as a necessary part of its being
able to propagate solitons.



If you can convince me
that a wavefront coming to a Magic T doesn't see it as an impedance
discontinuity, we could perhaps post more about that--or not.

Consult Terman. He is quite compelling when it comes to describing
microwave plumbing. This hardly constitutes more than 4 pages total
reading, if you choose to move on beyond the first page of discussion.

I find nothing in the index of my "Radio Engineers' Handbook" by
Terman under either "Magic" or "Hybrid". Sorry. The three different
coaxial "Magic T" hybrid designs I DID find all do show an impedance
discontinuity: the junction of more than two lines of equal impedance
and/or impedance steps in through-lines. Sorry.

Time to move on.

Cheers,
Tom

Constructive interference in radiowave propagation
 

On 17 Apr 2007 08:30:41 -0700, K7ITM wrote:

On Apr 17, 12:33 am, Richard Clark wrote:
On 16 Apr 2007 17:50:10 -0700, "K7ITM" wrote:
...
I still
don't have a reference that a fiber optic cable is a TEM transmission
line, though I have others that say that it's not.

That example of the non-TEM fiber optic would be rare species indeed.
I've seen them, but that hardly constitutes the sole species of the
breed.

So give me a reference already. I find lots of references, including
ones that explain the propagation, that talk about TM, TE, hybrid, and
even quasi-TEM mode propagation in a fiber. What boundary conditions
are there in an optical fiber that give TEM mode?

Hi Tom,

This is curious request indeed. Can you name any example of light
that is not TEM? Let's see, wikipedia's entry for TEM includes Fiber
Optics as example (along with the sources and illustrations for many
modes). TEM00 is the principle mode of the ubiquitous "single mode"
fiber optic that is laid in the millions of miles every year.

One vendor of Fiber modeling software
http://www.zemax.com
specifically at
http://www.zemax.com/kb/articles/154...MAX/Page1.html
offers:
"ZDC thanks Steve Dods of OptiWave Corporation for supplying the
SMF-28 fiber simulation data used in this article.

"In the article How to Model Coupling Between Single-Mode Fibers
SMF-28 single mode fiber is modeled using data from the
manufacturer's datasheet. The only data provided on the optical
radiation produced at 1.31 is the mode field diameter, which is
stated to be 9.2 ± 0.4 µm.

"As a result, the fiber mode of both launch and receiver fibers
was entered as a Gaussian (TEM0,0) mode of waist 4.6µ. The
resulting fiber coupling calculation agrees well with experimental
measurement."

Corning SMF-28 has been in production for nearly 20 years.

I still don't have
information on whether a soliton wave can propagate in a linear
medium, though I have references that say it is a non-linear
phenomenon that occurs in non-linear media.

Of course it can propagate in a linear medium. Solitons were first
reported in linear media - water - something like one hundred seventy
years ago.

Solitons can induce non-linearity in otherwise linear
media. Solitons also interact in collision with a phase shift
afterwards. Solitons have been applied to data transmission in fiber
optics for a dozen years or more.

Your references are pretty sparse.

Yours seem non-existent. Mine at least did a good job explaining the
phenomena.

To which there is scant difference as nearly every point you recite
has already been anticipated in my earlier post (shown above). Your
rebuttal that water is non-linear is already answered in this same
quote. If this is basenote drift, we are now into the treble clef.

If you can convince me
that a wavefront coming to a Magic T doesn't see it as an impedance
discontinuity, we could perhaps post more about that--or not.

Consult Terman. He is quite compelling when it comes to describing
microwave plumbing. This hardly constitutes more than 4 pages total
reading, if you choose to move on beyond the first page of discussion.

I find nothing in the index of my "Radio Engineers' Handbook" by
Terman under either "Magic" or "Hybrid". Sorry. The three different
coaxial "Magic T" hybrid designs I DID find all do show an impedance
discontinuity: the junction of more than two lines of equal impedance
and/or impedance steps in through-lines. Sorry.

Time to move on.

For others that are not moving on, but interested in the use and
issues of reflection to the source driving a Magic T, I quote work
from Q MEASUREMENTS FOR HIGH-Q CAVITIES
R. A. RAPUANO and J. HALPERN, MIT (1946):

"The heart of this equipment is the "magic T". This is an
eight-terminal network (Fig. 3) in waveguide or coax having
symmetry properties analogous to those of a "hybrid coil".
In the case of an ideal T, power entering the E aria is divided
equally between S1 and S2, both parts being out of phase; none
goes directly to H. Power entering the H arm is divided equally
between S1 and S2, with both parts now in phase; no power goes
directly to E. Power reflected from the loads on S1 and S2,
however, can be coupled from H to E, depending upon the magnitude
and phase of the terminal impedances on S1 and S In the case of
two short circuits the power going from H to E can be caused to
vary from zero to the full amount depending on their position
along the line. If a short circuit is placed on S1 and a resonant
cavity is placed on S2, then the power going from H to E is a
function of frequency. The power reflected back from H is the
difference between the input and the loss due to transmission
through E and absorption in the resonator."

Figure 3 (use fixed font):
S1
||
||
||
H ======== ======== E
||
||
||
S2

where the interior blank space represents the plumbing too difficult
to render here.

I would further offer that Walt is working on a fairly similar
treatment employing the "Rat Race" (alluded to as a Hybrid Coil in the
monograph extract above). The discussion above is germane in that
sense and would be beneficial to those who eventually see his
rebuttals to arguments pressed against him.

73's
Richard Clark, KB7QHC

Constructive interference in radiowave propagation
 

On Apr 17, 2:57 pm, Richard Clark wrote:
....

Richard, it really doesn't much matter to me what modes fiber optic
cable supports. If there are types that support true TEM mode, I'd be
happy to hear about it. So far, though, I've followed links from over
a dozen searches and found NO reference that claims that true TEM mode
is supported by a fiber, be it single-mode or multi-mode. I've gone
to the Wikipedia pages you suggested and other pages there, and found
quite a bit of info about fiber optic cables and their modes. In all
that, I have found no claim that true TEM mode is supported. I
followed the link you provided to the simulation software provider,
and found only that they modeled a particular cable as having TEM 0,0
mode; nowhere could I see a claim that the cable modeled actually
propagates by true TEM mode. The way the article was worded sounded
to me like the TEM entry was an approximation. In my research, the
closest to a claim of true TEM mode I've found has been in one recent
article that says TEM would be the ideal, but the best anyone's been
able to do is quasi-TEM or TEM-like.

You're welcome to think it's true TEM if you wish, of course, but your
saying it, over and over if you wish, isn't going to be nearly as
convincing as if we can find one, even one, ligitimate reference that
claims true TEM.

Cheers,
Tom

Constructive interference in radiowave propagation
 

On 17 Apr 2007 16:38:12 -0700, K7ITM wrote:

You're welcome to think it's true TEM if you wish, of course, but your
saying it, over and over if you wish, isn't going to be nearly as
convincing as if we can find one, even one, ligitimate reference that
claims true TEM.

Hi Tom,

What a hoot. "True" TEM? As distinct from virtual TEM? That is
about as funny as "ligitimate reference." Coining terms is a
wonderful thing if you can collect a royalty for their use.

These growing constraints have all the hallmarks of a shopping list of
suitor objections from the eternal spinster.

I reported TEM00 and offered supporting links. Just call me a liar so
I can regain my dignity. ;-)

73's
Richard Clark, KB7QHC