Roger Sparks wrote:
So, rather than disproving Cecil's premise, you successfully
demonstrated that it was correct in the instantaneous case.

Roger, my premise has nothing to do with the instantaneous
case. I have made no assertions about instantaneous values.
My formula applies *only to average power*. Using that
formula on instantaneous values is an invalid thing to do,
a misuse of the tool.
--
73, Cecil http://www.w5dxp.com

Dave wrote:
"Keith Dysart" wrote:
What is the mechanism that creates the effect we call interference?

superposition.

Not disagreeing - just expanding:
Superposition is certainly necessary but superposition
alone is not sufficient. Superposition can occur with
or without interference.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
So I accept the circuit theory result of
Prs.circuit(t) = 68 + 68 cos(2wt -61.92 degrees)
and conclude that, since the results using Cecil's hypothesis are
different, Cecil's hypothesis must be incorrect.

Keith, please stop using innuendo to try to discredit
me. My hypothesis does NOT apply to instantaneous values,
never has applied to instantaneous values, and never will
apply to instantaneous values. Please cease and desist
with your unethical innuendos.

If you have to stoop to lying about what I have said,
you will only discredit yourself.

My hypothesis is correct for average values of powers
and *applies only to average values of powers* just as
the irradiance equation from optical physics applies
only to average power densities. To the best of my
knowledge, there is no such thing as instantaneous
irradiance.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
To the best of my
knowledge, there is no such thing as instantaneous
irradiance.

The definition of irradiance is the "average energy
per unit area per unit time". Any deviation away
from "average energy per unit area per unit time"
when discussing what I have said is a straw man
diversion, not in the spirit of a good will
discussion.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:


Coherency, non-coherency, and interference is covered well
in "Optics" by Hecht and other textbooks. Optical physicists
have been tracking the EM energy flow for centuries. This
information may be new to you but it is old hat in physics.


Cecil,

You may or may not already know this, but a lot of detailed optical
analysis these days is done with full 3-D electromagnetic simulation,
starting from Maxwell equations and boundary conditions. Interference,
coherence, energy flow, and all of the other stuff you like to discuss
can be *output* from that analysis, but those items are not part of the
input. The "centuries old" optics simply does not get the job done. The
"centuries old" stuff may work in the (impossible) cases where
everything is completely lossless and ideal, but it doesn't give the
right answers in the real world.

73,
Gene
W4SZ

Cecil Moore wrote:


Quoting "Optics", by Hecht, Chapter 12. "Thus far in our
discussion of phenomena involving the superposition of waves,
we've restricted the treatment to that of either completely
coherent or completely incoherent disturbances. ... There is
a middle ground between these antithetic poles, which is of
considerable contemporary concern - the domain of
*partial coherence*.

"Contemporary" is an interesting word choice. Partial coherence has been
recognized for a long time. There is a very widely referenced paper by
H. H. Hopkins on partial coherence in optical imaging systems that was
published in 1950. He did not invent the concept, but he did popularize
the standard formulation still used today. The math is a bit messy, with
4 dimensional integrals and other complications, but numerical solutions
are widely done.

I would be quite surprised if the radar and other RF experts don't use
the same type of analysis.

Oh, by the way, even a completely monochromatic wave can be partially
coherent if the source is extended. Indeed, that is one of the more
common configurations.

73,
Gene
W4SZ

Cecil Moore wrote:
Cecil Moore wrote:
To the best of my
knowledge, there is no such thing as instantaneous
irradiance.

The definition of irradiance is the "average energy
per unit area per unit time". Any deviation away
from "average energy per unit area per unit time"
when discussing what I have said is a straw man
diversion, not in the spirit of a good will
discussion.

The definition of irradiance, according to NIST, is power per unit area.
The standard units are W/m2 or lumen/m2.

You can add average, peak, instantaneous, or whatever you like to
further define your quantity of interest. Such additions, however, are
not part of the standard definition of irradiance.

73,
Gene
W4SZ

On Fri, 07 Mar 2008 15:15:08 GMT
Cecil Moore wrote:

Roger Sparks wrote:
So, rather than disproving Cecil's premise, you successfully
demonstrated that it was correct in the instantaneous case.

Roger, my premise has nothing to do with the instantaneous
case. I have made no assertions about instantaneous values.
My formula applies *only to average power*. Using that
formula on instantaneous values is an invalid thing to do,
a misuse of the tool.
--
73, Cecil http://www.w5dxp.com

I find myself surprised at your insistance that the instantaneous case must be seperated from the average case in our example of waves on a transmission line. Our ability to measure within the confines of the sine wave is much greater than what is possible at optic frequencies so we are led to expect much more than averages.

It is informative to look at each problem from many angles. Keith's method is one way. Another way is to observe that when we begin considering what is happening with the source resistor, we are really bringing the source resistor into the circuit, i.e., bringing the source resistor outside of the 'black box'. Once we do that, we can see that the source prereflection load is not the same as the post reflection load. From this perspective, the equation "PRs = 50w + Pref" becomes a target to which we adjust the source voltage to acheive. We would accomplish that by using your equation but Keith's method.

It seems to me like Keith is using interference, both constructive and destructive, to calculate what the source load would be on the instantaneous basis. To me it seems like a validation of your premise.

Did I misunderstand your premise, and you were really trying to say that the inclusion of a 50 ohm source resistor would prevent the source from ever 'seeing' anything but a 100 ohm load? I don't think that was your intent.
--
73, Roger, W7WKB

Gene Fuller wrote:
You may or may not already know this, but a lot of detailed optical
analysis these days is done with full 3-D electromagnetic simulation,
starting from Maxwell equations and boundary conditions. Interference,
coherence, energy flow, and all of the other stuff you like to discuss
can be *output* from that analysis, but those items are not part of the
input. The "centuries old" optics simply does not get the job done. The
"centuries old" stuff may work in the (impossible) cases where
everything is completely lossless and ideal, but it doesn't give the
right answers in the real world.

Ideal examples are time-honored ways of discussing concepts
and getting away from the vagaries of the real world. If one
understands the ideal examples, one is in a position to then
proceed to understanding the real world. If one fails to
understand the conceptual principles underlying the ideal
examples, one cannot possibly understand the real world.

Your posting seems to reflect your usual sour grapes attitude.
I will expect you to object to every example that uses lossless
transmission lines from now on including ones by Ramo & Whinnery,
Walter Johnson, Walter Maxwell, J. C. Slater and Robert Chipman.
--
73, Cecil http://www.w5dxp.com

Gene Fuller wrote:
The definition of irradiance, according to NIST, is power per unit area.
The standard units are W/m2 or lumen/m2.

Exactly how much power can exist in a zero unit of
time?

You previously objected to things that don't match
the real world. Instantaneous irradiance would rely
on an infinitesimally small amount of time, something
that doesn't match reality very well. One would think
you would therefore object to the concept of instantaneous
irradiance since it cannot be measured in reality and
exists only in the math model in the human mind.
--
73, Cecil http://www.w5dxp.com