On Mar 5, 1:58*pm, Cecil Moore wrote:
Keith Dysart wrote:
Thus conveniently showing that for this example, the reflected
power is not dissipated in Rs.

The *average* reflected power is certainly dissipated in Rs
because there is nowhere else for it to go. Your instantaneous
power, according to Eugene Hecht, is "of limited utility" which
you have proved with your straw man assertion above.

Hecht seems to have sufficient reputation that I trust that he made
this statement in the context of optics and not in the context of
electrical circuits.

I have made no assertions about instantaneous power. All of
my assertions have been about average power and you have proved
none of my assertions about average power to be false.

True. But analysis using instantaneous power reveals a different
answer.
Which is more likely to be correct?

Here is what you are doing:
Cecil: My GMC pickup is white.
Keith: No, your GMC pickup has black tires.

Your diversions are obvious. Instantaneous power is irrelevant
to my assertions.

Only if you give up on conservation of energy in instantaneous flows.

...Keith

Keith Dysart wrote:
Hecht seems to have sufficient reputation that I trust that he made
this statement in the context of optics and not in the context of
electrical circuits.

EM waves are EM waves, Keith, no matter what the frequency.
EM waves all obey the laws of reflection physics, superposition,
and conservation of energy principle. If you want to prove those
laws to be invalid and replace them with ones of your own design,
be our guest.

But analysis using instantaneous power reveals a different
answer. Which is more likely to be correct?

Analysis using an MFJ-259B on an antenna system reveals a
different impedance than is indicated by a DC ohm-meter.
So what? You used an average power tool, known to be
invalid for instantaneous powers, to incorrectly analyze
instantaneous powers. You are the one who made the error
- not the model. Your error was the (deliberate?) misuse
of the tool in order to try to create your straw man.

Using the power equation, derived from RMS values of
voltage, on instantaneous powers is an invalid thing
to do and will give known erroneous results which are
not the fault of the average power model. The fault is
in the *misuse* of the average power model.

We have already laid your straw man argument to rest
when we discussed the power in standing waves.

1. There is non-zero instantaneous power in standing waves.
2. There is zero average power in standing waves.

Does statement 1 contradict statement 2? Of course not.
They are both true. The same holds true for the present
discussion.

I have a probable explanation for your calculations. I
set the example up such that the average interference
is zero inside the source. It is entirely possible that
localized interference exists within each cycle such
that there is destructive interference for part of the
cycle and constructive interference in another part of
the cycle. In fact, based on the conservation of energy
principle, I am willing to state that is a fact and the
destructive interference magnitude exactly equals the
constructive interference magnitude for each cycle.
--
73, Cecil http://www.w5dxp.com

On Mar 5, 8:06 am, Cecil Moore wrote:
....blah, blah...

So consider the case of a section of lossless uniform transmission
line of characteristic impedance R0, which I write as R instead of Z
since it of course must be real-valued, connected between two sources
S1 at end 1 and S2 at end 2. These sources each have source impedance
R0: they are perfectly matched to the characteristic impedance of the
line. The line is long enough that we can observe any standing waves
that may be on it. (For believers in directional couplers, that can
be short indeed, but it does not need to be short.) Source S1 is set
to output a sinusoidal signal of amplitude A1 into a matched load, on
frequency f1. Similarly S2 outputs a sinusoidal signal A2 into a
matched load at frequency f2, which is distinct from f1.

It is easy to show mathematically, and to measure in practice, that
the amplitude of the frequency f1 is constant along the line, and
similarly that the amplitude of the frequency f2 is constant along the
line. That is to say, there is no standing wave at either frequency.
Energy at f1 travels on the line only in the direction from S1 to S2,
and vice-versa for f2.

That says to me that the energy on the line at f1 is absorbed entirely
by source S2, and the energy at f2 is absorbed entirely by S1, with no
reflection at the boundaries between S1 and the line, and the line and
S2.

At this point, I leave it as an exercise for the reader to interpret
or explain exactly what is meant by "absorbed by." This may involve
understanding that in a Thevenin or Norton simple model of each
source, the energy delivered by the voltage or current source at any
moment in time may not equal that which it would deliver into a
matched load at the same point in the cycle...

Cheers,
Tom

K7ITM wrote:
So consider the case of a section of lossless uniform transmission
line of characteristic impedance R0, which I write as R instead of Z
since it of course must be real-valued, connected between two sources
S1 at end 1 and S2 at end 2. These sources each have source impedance
R0: they are perfectly matched to the characteristic impedance of the
line. The line is long enough that we can observe any standing waves
that may be on it. (For believers in directional couplers, that can
be short indeed, but it does not need to be short.) Source S1 is set
to output a sinusoidal signal of amplitude A1 into a matched load, on
frequency f1. Similarly S2 outputs a sinusoidal signal A2 into a
matched load at frequency f2, which is distinct from f1.

What you have described is a system with two sources which
are incapable of interfering with each other because they
are not coherent. Note that this example bears zero resemblance
to a system where the sources are coherent, i.e. frequency-
locked and phase-locked and therefore, capable of interference.

It is easy to show mathematically, and to measure in practice, that
the amplitude of the frequency f1 is constant along the line, and
similarly that the amplitude of the frequency f2 is constant along the
line. That is to say, there is no standing wave at either frequency.
Energy at f1 travels on the line only in the direction from S1 to S2,
and vice-versa for f2.

Obviously true for non-coherent sources.

That says to me that the energy on the line at f1 is absorbed entirely
by source S2, and the energy at f2 is absorbed entirely by S1, with no
reflection at the boundaries between S1 and the line, and the line and
S2.

Obviously true for non-coherent sources.

Unfortunately, "non-coherent sources" is not the subject of
this discussion. The rules change between non-coherent, non-inter-
fering sources and coherent, interfering sources. I suggest you
reference the "Interference" chapter in "Optics", by Hecht.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Keith Dysart wrote:
Hecht seems to have sufficient reputation that I trust that he made
this statement in the context of optics and not in the context of
electrical circuits.

EM waves are EM waves, Keith, no matter what the frequency.
EM waves all obey the laws of reflection physics, superposition,
and conservation of energy principle. If you want to prove those
laws to be invalid and replace them with ones of your own design,
be our guest.

Cecil,

It is likely that all of these interference-related items you like to
quote from Hecht are cast in an environment of lossless optical
components. The characteristic impedance is set by the index of
refraction of the various layers, but none of the optical layers have
any absorption.

Soooo, how does any of this optical stuff extend to making arguments
about the absorption or re-reflection of energy in the source resistor
for the HF case?

The laws of physics may be inviolate, but it is not quite so clear that
your derived and extended models share the same characteristic.

73,
Gene
W4SZ

On Mar 5, 1:27 pm, Cecil Moore wrote:
The rules change between non-coherent,
non-interfering sources and coherent, interfering sources.

And exactly which part of "linear system" do you fail to understand?

Gene Fuller wrote:
Soooo, how does any of this optical stuff extend to making arguments
about the absorption or re-reflection of energy in the source resistor
for the HF case?

What happens at a flat black interface in optics?
--
73, Cecil http://www.w5dxp.com

K7ITM wrote:
On Mar 5, 1:27 pm, Cecil Moore wrote:
The rules change between non-coherent,
non-interfering sources and coherent, interfering sources.

And exactly which part of "linear system" do you fail to understand?

When two equal amplitude coherent signals are superposed,
the resulting power density can be four times the power
density of one of the single waves due to constructive
interference.

That is not true for two equal amplitude non-coherent
waves of different frequencies. The interference term
averages out to zero so there are no bright rings and
dark rings.

I'm surprised you don't know that.
--
73, Cecil http://www.w5dxp.com

On Mar 5, 5:25 pm, Cecil Moore wrote:
K7ITM wrote:
On Mar 5, 1:27 pm, Cecil Moore wrote:
The rules change between non-coherent,
non-interfering sources and coherent, interfering sources.

And exactly which part of "linear system" do you fail to understand?

When two equal amplitude coherent signals are superposed,
the resulting power density can be four times the power
density of one of the single waves due to constructive
interference.

That is not true for two equal amplitude non-coherent
waves of different frequencies. The interference term
averages out to zero so there are no bright rings and
dark rings.


Yes, yes, you've posted all that a billion times before in this NG.
Now, exactly what part of "linear system" do you fail to understand?

(I might also ask why you're going to so much trouble to be
disagreeable with something that agrees with what you were
posting...but I think I already know the answer to that one.)

Cecil Moore wrote:
Gene Fuller wrote:
Soooo, how does any of this optical stuff extend to making arguments
about the absorption or re-reflection of energy in the source resistor
for the HF case?

What happens at a flat black interface in optics?

And that would be relevant in what manner? Does Hecht discuss
interference at flat black interfaces?

Nobody is questioning the laws of physics or Hecht's writings. Many are
questioning your extensions to your own models. Name-dropping and
invoking the sacred laws of physics do not automatically validate your
models.

Did you ever wonder why all of the basic phenomena, both optical and RF,
were known to the "ancients", yet you are the first one to pull
everything together in this miraculous new version of a reflection model?

73,
Gene
W4SZ