Keith Dysart wrote:
Can you make this all work for a pulse, or a step
function?

Please reference a good book on optical EM waves
for a complete answer. It is *not me* making it work.
It is a body of physics knowledge that has existed
since long before you were born. It should have
been covered in your Physics 201 class. That you
are apparently unaware of such is a display of
basic ignorance of the science of EM waves.

The basic theory applies specifically to coherent
waves (which are the only EM waves capable of truly
interfering). CW RF waves are close enough to ideal
coherency that the theory works well. It would no
doubt work for a coherent Fourier series as well
but I don't want to spend the time necessary
to prove that assertion.

How do you compute
Ptot = Ps + Pr + 2*SQRT(Ps*Pr)cos(A)
for a pulse or a step?

The above equation applies to coherent signals.
It is known not to work when the signals are not
coherent because the angle 'A' never reaches
a fixed steady-state value.

Or is your approach limited to sinusoids?

Again, it is not *my* approach and is described in any
textbook on "Optics" including Hecht and Born & Wolf.
--
73, Cecil http://www.w5dxp.com

On Jan 2, 9:59*am, Cecil Moore wrote:
Keith Dysart wrote:
Can you make this all work for a pulse, or a step
function?

I accept your "NO" and agree that EM waves are
incapable of providing solutions for pulse or
step excitation.

But why don't you just say so clearly.

Please reference a good book on optical EM waves
for a complete answer.

Given that optical EM waves are only capable of
solving a subset of the uses of transmission lines,
it is not obvious why I should study them when
I can invest in learning approaches that will do
the whole job.

It is *not me* making it work.

True. And as you have said, it does not work
for pulses or steps.

It is a body of physics knowledge that has existed
since long before you were born. It should have
been covered in your Physics 201 class. That you
are apparently unaware of such is a display of
basic ignorance of the science of EM waves.

Some who claim to have studied them thoroughly
seem to be constrained by their limitations. Is
that better?

The basic theory applies specifically to coherent
waves (which are the only EM waves capable of truly
interfering). CW RF waves are close enough to ideal
coherency that the theory works well. It would no
doubt work for a coherent Fourier series as well
but I don't want to spend the time necessary
to prove that assertion.

How do you compute
* Ptot = Ps + Pr + 2*SQRT(Ps*Pr)cos(A)
for a pulse or a step?

The above equation applies to coherent signals.
It is known not to work when the signals are not
coherent because the angle 'A' never reaches
a fixed steady-state value.

Or is your approach limited to sinusoids?

Again, it is not *my* approach and is described in any
textbook on "Optics" including Hecht and Born & Wolf.

Well, others more knowledgeable than I in optics
have disputed whether *your* approach accurately
represents those described in the textbooks.

In any case, being applicable only to sinusoids
limits the general applicability to transmission
lines which happily work at DC.

...Keith

Keith Dysart wrote:
Cecil Moore rote:
But why don't you just say so clearly.

I explained why it only applies to coherent
waves. Every model has its limitations, even
yours unless you are presenting a theory of
everything.

Given that optical EM waves are only capable of
solving a subset of the uses of transmission lines,
it is not obvious why I should study them when
I can invest in learning approaches that will do
the whole job.

That's not a given and is in fact a falsehood.
RF waves are a subset of light waves. Perhaps
you are erroneously confusing "light waves" with
"visible light waves".

When a light wave is red-shifted to 10^12 times
its original wavelength, does it cease to be a
light wave? Feel free to answer yes or no.

Well, others more knowledgeable than I in optics
have disputed whether *your* approach accurately
represents those described in the textbooks.

The last resort is an argumentium ad verecundiam,
an appeal to reverence/authority. Who, in particular,
do you consider to be the High Priest of r.r.a.a?

The technical truth will win out in the long run.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
On Jan 2, 9:59 am, Cecil Moore wrote:


Please reference a good book on optical EM waves
for a complete answer.



It is a body of physics knowledge that has existed
since long before you were born. It should have
been covered in your Physics 201 class. That you
are apparently unaware of such is a display of
basic ignorance of the science of EM waves.



The basic theory applies specifically to coherent
waves (which are the only EM waves capable of truly
interfering). CW RF waves are close enough to ideal
coherency that the theory works well. It would no
doubt work for a coherent Fourier series as well
but I don't want to spend the time necessary
to prove that assertion.



Again, it is not *my* approach and is described in any
textbook on "Optics" including Hecht and Born & Wolf.

Well, others more knowledgeable than I in optics
have disputed whether *your* approach accurately
represents those described in the textbooks.

In any case, being applicable only to sinusoids
limits the general applicability to transmission
lines which happily work at DC.

...Keith


It is sadly amusing that Cecil takes so much comfort in optics. The
electromagnetic theory for optics (e.g. somewhere in the vicinity of
visible light) is of course identical to the electromagnetic theory for
HF. The preferred applications and shortcuts are sometimes a bit
different, but that is simply a matter of convenience and of no
importance here.

I have a couple of editions of Born and Wolf, which is a high level
reference and often considered the standard for optics. I have been
unable to find even one mention of "constructive" or "destructive"
interference in their writing. Of course they delve into the topic of
interference in excruciating detail. They don't, however, ascribe any
particular mysticism or magic to interference. It is simply what happens
when the wave fields are superposed.

The more popular accounts, such as the FSU Java applet on interference,
the Melles-Griot web site, and apparently the text by Hecht, stay a bit
further from rigorous analysis. Therefore they resort to handwaving
requirements such as destructive must be balanced by constructive, blah,
blah, blah.

Adding the voltages in the manner you and Roy have done is precisely the
same operation as Cecil's interference method, without the emotional
baggage.

73,
Gene
W4SZ

Gene Fuller wrote:
The
electromagnetic theory for optics (e.g. somewhere in the vicinity of
visible light) is of course identical to the electromagnetic theory for
HF.

Thanks Gene, I never thought you would ever admit that
fact of physics. Now that you have, your entire argument
collapses. If interference can happen in free space, it
certainly can happen in a transmission line.

I have a couple of editions of Born and Wolf, which is a high level
reference and often considered the standard for optics. I have been
unable to find even one mention of "constructive" or "destructive"
interference in their writing.

Try "Optics" by Hecht. He devotes an entire chapter
to interference. Hecht mentions destructive and constructive
interference dozens of times. I can quote page after page
of such if you want me to. Feel free to dispute Hecht if
you want, but that is your problem, not mine.

Of course they delve into the topic of
interference in excruciating detail. They don't, however, ascribe any
particular mysticism or magic to interference. It is simply what happens
when the wave fields are superposed.

Neither do I. It is just what happens when the wave fields
are superposed. The destructive interference must balance
the constructive interference to avoid violation of the
conservation of energy principle.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
The electromagnetic theory for optics (e.g. somewhere in the vicinity
of visible light) is of course identical to the electromagnetic theory
for HF.

Thanks Gene, I never thought you would ever admit that
fact of physics. Now that you have, your entire argument
collapses. If interference can happen in free space, it
certainly can happen in a transmission line.


Cecil,

No one has ever said anything different. No one has ever denied
interference.

You are really grasping at straws now.

73,
Gene
W4SZ

Gene Fuller wrote:
No one has ever said anything different. No one has ever denied
interference.

Denying that you ever argued about something is a first
step in the direction of understanding. Before long, you
will be arguing that you knew all of this stuff long ago.
--
73, Cecil http://www.w5dxp.com