The Rest of the Story
 

Keith Dysart wrote:
That is why I pose the question, hoping for someone to
describe the mechanism that the energy for the flow that
is happening now can be borrowed from the future.

Destructive interference would have to happen first.

But what happens if the generator is turned off before
the future arrives? Where did the extra energy come from
then?

There is no extra energy. Constructive interference is
impossible without that supply of energy.

Actually, I have a pretty good grasp of what is happening
in free space, and it is all available to you by extension
from the behaviours of the one dimensional transmission
line. But there is little point in going there until the
transmission line is understood.

It is the exact opposite. There is no point in inventing
new laws of physics for transmission lines if those new
laws don't work in free space.

So please present an example of EM waves reflecting off
of other EM waves in free space. Do you really think the
energy in the standing wave beam of a laser is reversing
direction and momentum every cycle?
--
73, Cecil http://www.w5dxp.com

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Keith Dysart wrote:
The voltage distribution on the line, the current
distribution on the line and the energy distribution
on the line has not changed one iota.

In one case the wave energy changes direction and
momentum at the physical discontinuity. In the
other case, there exists nothing to change the
wave direction and momentum.

This new physical impedance discontinuity has not
had any observable effect. All it seems to change
is the reflection of the unobservable forward and
reflected waves.

Yes, exactly in agreement with the laws of physics.

But the voltage distribution on the line, the current
distribution on the line and the energy distribution
on the line has not changed one iota.

Please present your new laws of physics that allow
EM waves to reflect off of EM waves in the complete
absence of a physical discontinuity. And please
demonstrate such in free space so we can see the
results.
--
73, Cecil http://www.w5dxp.com

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On Apr 9, 9:40*pm, Cecil Moore wrote:
Keith Dysart wrote:
Actually, the transmission line input impedance is quite real,
formed from distributed capacitance and inductance. Like most two
terminal circuits, it can be reduced to simpler form.

I didn't say virtual impedances are not real. I
said they are not causes of anything and are,
instead, effects of superposition incapable of
causing anything in the complete absence of a
physical impedance.

But the distributed capacitance and inductance
are physical impedances.

You have for a long while now, confused cause
and effect. Maybe you should review the three
separate definitions of "impedance" given in
the IEEE Dictionary.

Neither 'virtual impedance' nor 'impedance, virtual'
are in the dictionary (at least the 7th Edition).

...Keith

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On Apr 9, 9:48*pm, Cecil Moore wrote:
Keith Dysart wrote:
As long as you agree that the imputed energy in the
reflected wave is not dissipated in the source
resistor;

My ethical standards will not allow me to lie about
technical facts in evidence. You cannot bully me
into doing so.

When the average interference is zero, all of the
average reflected energy is dissipated in the source
resistor. It is true for all examples of Fig. 1-1.
You have not presented even one example where
that is not a true statement.

But all you have demonstrated is that the imputed
average power in the reflected wave is *numerically
equal* to the average increase in the dissipation
of the source resistor. Which is good, as long as
that is all you claim. Which it some times seems
to be, especially when you qualify with "interference
is zero".

Finer grained analysis shows that the imputed
energy (not average) in the reflected wave is not
dissipated in the source resistor. The trouble
is, sometimes you agree with this (when you
invoke that interference is present), but other
times you don't (see your response to the opening
paragraph). It is this flip-flop that makes your
actual position difficult to discern.

...Keith

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On Apr 9, 9:57*pm, Cecil Moore wrote:
Keith Dysart wrote:
That is why I pose the question, hoping for someone to
describe the mechanism that the energy for the flow that
is happening now can be borrowed from the future.

Destructive interference would have to happen first.

For the example under discussion, the signals start with
'constructive interference'. There has not yet been an
opportunity for desctructive interference, which happens
later. So where does the extra energy at the start come
from?

But what happens if the generator is turned off before
the future arrives? Where did the extra energy come from
then?

There is no extra energy. Constructive interference is
impossible without that supply of energy.

Exactly. This is the problem with your model. The extra
energy (i.e. the energy greater than that in the sum of
the spectral components) is present, but your model does
not have somewhere for this energy to come from.

Actually, I have a pretty good grasp of what is happening
in free space, and it is all available to you by extension
from the behaviours of the one dimensional transmission
line. But there is little point in going there until the
transmission line is understood.

It is the exact opposite. There is no point in inventing
new laws of physics for transmission lines if those new
laws don't work in free space.

There are no new laws of physics. There is just the
opportunity for a better understanding of what is
happening. This better understanding applies in free
space as well. It is just much easier to obtain this
better understanding on the transmission line and then
move to free space.

So please present an example of EM waves reflecting off
of other EM waves in free space.

That was someone elses suggestion, not mine.

Do you really think the
energy in the standing wave beam of a laser is reversing
direction and momentum every cycle?

Why does this thought make you uncomfortable? Is it because
you are trying to commingle the wave explanation with the
partical explanation? These are a duality. You use one
or the other, but not bits from each at the same time.

...Keith

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On Apr 9, 10:02*pm, Cecil Moore wrote:
Keith Dysart wrote:
The voltage distribution on the line, the current
distribution on the line and the energy distribution
on the line has not changed one iota.

In one case the wave energy changes direction and
momentum at the physical discontinuity. In the
other case, there exists nothing to change the
wave direction and momentum.

As I expected, you claim that the situations are
*completely* different. And yet the voltage, current
and energy distributions are identical. There are
no observable differences. And yet you claim they
are *completely* different. And yet there are no
observable differences. And yet....

Tis a puzzle, isn't it.

And we know from circuit theory that we can cut
a conductor carrying no current without affecting
the circuit. Why should it be different here?

This new physical impedance discontinuity has not
had any observable effect. All it seems to change
is the reflection of the unobservable forward and
reflected waves.

Yes, exactly in agreement with the laws of physics.

At least with your interpretation of the laws.

But the voltage distribution on the line, the current
distribution on the line and the energy distribution
on the line has not changed one iota.

Please present your new laws of physics that allow
EM waves to reflect off of EM waves in the complete
absence of a physical discontinuity.

Again, not my claim. But using your previous approach
for analysis, perhaps we should insert a zero length
line of the appropriate impedance to provide the cause
for the reflection, if you insist on a reflection.

And please
demonstrate such in free space so we can see the
results.

...Keith

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Keith Dysart wrote:
But the distributed capacitance and inductance
are physical impedances.

But they are constant, i.e. there is no physical
impedance *discontinuity*. The reflection coefficient
inside a homogeneous piece of transmission line is
(Z0-Z0)/(Z0+Z0)=0, i.e. there can be no reflections.
The reflection coefficient in free space is
(1.0-1.0)/(1.0+1.0)=0, i.e. there can be no reflections
in free space.

Neither 'virtual impedance' nor 'impedance, virtual'
are in the dictionary (at least the 7th Edition).

"Virtual" essentially means that no physical impedor
exists. The virtual impedance definition is covered
by definition (B), the ratio of voltage to current
which *causes* the impedance. A virtual impedance
is an *effect*, not a cause.
--
73, Cecil http://www.w5dxp.com

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Keith Dysart wrote:
Finer grained analysis shows that the imputed
energy (not average) in the reflected wave is not
dissipated in the source resistor.

It is the joules in instantaneous power that must
be conserved, not the instantaneous power. There
is no such thing as a conservation of power
principle yet all you have presented are power
calculations. "Where's the beef?"

How many joules are there in 100 watts of
instantaneous power?
--
73, Cecil http://www.w5dxp.com

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Keith Dysart wrote:
For the example under discussion, the signals start with
'constructive interference'.

If the source is local and capable of supplying energy,
all is well and good as I have said many times before.
But constructive interference in the absence of any
source of energy is impossible.

That is exactly why you need to perform your calculations
with the source removed from the source resistor by one
wavelength of ideal 50 ohm transmission line. If you come
up with a violation of the conservation of energy principle,
something is wrong with your math.

If two coherent signals need constructive interference and
energy is not available, the two signals react as if they
were not coherent, i.e. Ptot = P1 + P2. Physics 201.

Exactly. This is the problem with your model. The extra
energy (i.e. the energy greater than that in the sum of
the spectral components) is present, but your model does
not have somewhere for this energy to come from.

Yes it does - as I have explained about 5 times now. If a
*local source* is present, constructive interference energy
can and often does come from the source. Why do you find
that fact so hard to comprehend? Sources supply energy -
that's what sources do. An ideal local source can react
instantaneously to any energy requirement.

There are no new laws of physics.

On the contrary - there are no existing laws of physics
that allow EM waves to bounce off each other yet that's
what you are proposing. You are inventing new laws of
physics to support your (magical) thinking. So please
produce the theory and proof that EM waves can bounce
off of each other.

That was someone elses suggestion, not mine.

Copout alert! How can *your* reflections at a passive
node occur without EM waves reflecting off of other EM
waves?

These are a duality. You use one
or the other, but not bits from each at the same time.

Keith, you have been willy-nilly mixing bits of the
distributed network model with bits of the lumped circuit
model ensuring that your energy equations will not balance.
You are the absolute worst offender of your own advice.
--
73, Cecil http://www.w5dxp.com

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Keith Dysart wrote:
As I expected, you claim that the situations are
*completely* different. And yet the voltage, current
and energy distributions are identical. There are
no observable differences. And yet you claim they
are *completely* different. And yet there are no
observable differences. And yet....

I did NOT claim that the situations are *completely*
different. I said that some conditions are different
and some conditions are the same. Voltages and currents
are the same yet there is certainly a difference between
an open circuit and a short circuit. Besides, in the
real world, cutting the line would certainly cause
observable differences.

Tis a puzzle, isn't it.

Nope, if you were born without your five senses,
you would feel that way about everything in existence.
Why do you deliberately choose to remain handicapped
by ignorance?

A bit of modulation would cure up the mystery for
you. If any modulation crosses the node, it is a
good bet that wave energy is carrying the
modulation. If phase locked TV signal generators
equipped with circulator load resistors are
installed at each end of a transmission line,
the TV signals can be observed on normal TV
sets crossing the standing wave nodes as if
they didn't exist. Removing the modulation
is unlikely to reverse the laws of physics.

And we know from circuit theory that we can cut
a conductor carrying no current without affecting
the circuit. Why should it be different here?

Please prove that a short circuit and an open circuit
are identical.

Please present your new laws of physics that allow
EM waves to reflect off of EM waves in the complete
absence of a physical discontinuity.

Again, not my claim.

Seems your theory requires such. Please explain how
reflections can occur at a passive standing wave node
without EM waves bouncing off of each other.

Energy and momentum both must be conserved. A causeless
reversal of energy and momentum is impossible whether
it is a bullet or an EM wave.

But using your previous approach
for analysis, perhaps we should insert a zero length
line of the appropriate impedance to provide the cause
for the reflection, if you insist on a reflection.

Please produce an example of
a real world transmission line that would support your
100% reflection. Hint: what would be the Z02
characteristic impedance in the reflection
coefficient equation, (50-Z02)/(50+Z02) = 1.0 ???
--
73, Cecil http://www.w5dxp.com