Revisiting the Power Explanation
 

On Sun, 01 Apr 2007 18:18:53 GMT, Walter Maxwell
wrote:

Richard, also consider an open-wire transmission line, equal and opposite currents flowing on each wire, and
no common-mode currents. There is zero radiation, because the opposing fields developed by the current flow
cancel. Are you denying that the zero radiation results from interferece?

Hi Walt,

Zero radiation results from a particularly small in relation to
wavelength separation of wires. In a very close proximity, all loads
see the same phase balance (0), hence the combination of these issues
of distance with regard to wavelength render a null in any load remote
from the line you have described.

Also, consider standing waves on on a line, resulting from the superposition of the forward and reflected
waves, where the maximum amplitude results from constructive interference and the minimum amplitude results
from destructive interference. Are you denying the existence of interference in this case?

In a lossless line, you can't tell the difference. In a lossy line,
you have found a load. As any lossy line generally presents the same
loss on a per-length basis, it is obvious that phase combines to
create loss in only certain positions with regard to distance and
wavelength. Mapping will follow the load.

Barring either of these cases, you have to insert a load into the line
to force the interference. Sure, you can anticipate it
mathematically. And certainly it will be borne out in practice with
lossy line melting or arcing at cardinal points. Without that loss -
who cares? Nothing happened or will happen and the waves will never
interact to give a new product as (I imagine we have agreed) this is
linear space.

The operation of TR/ATR tubes in transmission line systems works with
this to force interference to steer radiation. Remove the tubes and
the action ceases. The fields in an identical transmission line
environment cannot do it themselves without that load present. This
is classic RADAR systems topology.

Imagine what this would be like with the "Magic T?"

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

On Sun, 01 Apr 2007 18:30:06 GMT, Cecil Moore
wrote:
Cecil Moore wrote:

Richard, did you unethically edit my posting to make
it appear that I said something different from what
I said?

So, are you still sleeping with Hecht?

Revisiting the Power Explanation
 

On 1 Apr 2007 18:05:39 -0700, "walt" wrote:

On Apr 2, 1:51 pm, Richard Clark wrote:
On Sun, 01 Apr 2007 18:30:06 GMT, Cecil Moore
wrote:

Cecil Moore wrote:

Richard, did you unethically edit my posting to make
it appear that I said something different from what
I said?

So, are you still sleeping with Hecht?

Richard, it's very uncommon, but on this issue I'm having a difficult
time following you. The only reason that I can conclude for my lack of
understanding is that our definition of 'interference' must be
divergent. So I'll just drop the discussion--OK?

Hi Walt,

It's fine, except you were the only lucid respondent in this recent
line of inquiry.

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

On 1 Apr 2007 18:25:19 -0700, "Jim Kelley" wrote:

Also note that 'Watt' isn't a unit of irradiance or current.

Also note that irradiance also demands an area unit. Same old errors.

Maybe absolute braces could gussy up the treatment.

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

Walter Maxwell wrote:
On Wed, 28 Mar 2007 16:26:10 -0700, Jim Kelley wrote:


Hi Cecil -

We've been over this a hundred times already. The only way to get
past it is for you to try to understand that my comment and Eugene
Hecht's are both true. You need to find a way to understand that
there is no contradiction. You could start by noting that Hecht does
not contradict anything that I said. Nowhere does he claim that
interference redirects energy. That's your claim! And I haven't said
that energy isn't redirected. If redirection of energy takes place,
it takes place by reflection - not interference. It's just basic optics.

73, ac6xg


Sorry Jim, but I take exception to your statement, "If redirection of energy takes place,
it takes place by reflection - not interference."

It is the interference between the forward and reflected voltages and beween the forward and reflected
currents that yields the resultant voltage and current values of rho at the matching point which produces
either a virtual short or a virtual open circuit that causes the re-reflection. I have shown this to be true
in my QEX article of Mar/Apr 1998, entitled, "Examining the Mechanics of Wave Interference in Impedance
Matching. It is also Chapter 23 in Reflections 2.

Using the complex values of rho I have shown the magnitude and phase relationships of the aforementioned
voltages and currents at the stub point that result in a virtual open circuit at the stub point to waves
reflected from a 3:1 mismatched load. The result is no reflections on the line between the stub and the
source, but a 3:1 SWR on the line between the mismatched load and the stub. If you don't have a copy of this
article please let me know and I'll send you one via email.

Walt, W2DU

Hello Walt,

Please know that all of my comments are offered with all due respect,
and there is a lot of respect due, and sincerely felt. However,
though the numbers work out as one would expect given the effects
that are observed, cause can only be attributed to
phenomenon which is observed in nature. Electromagnetic
waves can reflect only from real media. Though I admire the procedure
you have devised for describing the complex effects of these
reflections, the attempts to extend those ideas to describe real (not
virtual) physical phenomena are unsupported from a scientific
standpoint. Inference is insufficient proof.

Specifically: The nature of reflective surfaces does not depend on
whether or not steady state has been reached. Their reflectivity does
not change as a function voltage. Their nature does not depend on
things which lie at the other end of the transmission line - even
though the overall performance of the system certainly does. The
nature of reflective surfaces does not depend on how many times the
wave has bounced back and forth since the signal was initiated. These
things are implied by your claim, unfortunately.

In the case of optical media, reflectivity is determined by the
relative indices of refraction of the optical media comprising the
reflective surface. Neither the
indices, nor their ratio changes in response to illumination.
Likewise, the reflective nature of impedance discontinuities on a
transmission line depend entirely on physical constants analogous to
optical indices of refraction. These attributes do not tend to change
when illuminated by RF.

I thought we had covered this ground back a couple of years ago when
the topic of reflections from virtual shorts and opens came up on this
newsgroup. At that time it became clear that certain of the
predictions made under the model did not match well with reality.
For example, the virtual short circuit which can appear at the
entrance to a stub on a transmission line would, according to the
model, prevent the very currents necessary for creating the virtual
condition from entering the stub in the first place. Reflections can
occur only at physical discontinuities, not at a voltage to current ratio.

I was encouraged by the work we did on your transmission line
impedance matching transformer diagram. In that, it seemed we agreed
that the reflective coefficients were constant, were determined by the
characteristic impedance's of the transmission lines, and that steady
state was in fact comprised of the summation of a long series of
multiple partial reflections. And, it correlates exactly with the
descriptions and drawings of the analogous optical phenomena in the
physics texts.

I really admire your work, Walt, but I feel this one point is clearly
inconsistent with nature. Let me hasten to add that I see nothing at
all wrong with making calculations based on this model. Its utility
and beauty lies in its accuracy at the macroscopic level. I also
think that your treatise on interference as it applies to the
reflections found in RF systems is well done. The error I find is in
your notion of interference as a cause of reflection, which I assume
is extrapolated from your notion that virtual shorts and opens cause
reflections, and, that real reflective coefficients may be calculated
from virtual impedance's.

Best Regards,

Jim Kelley

Revisiting the Power Explanation
 

Jim Kelley wrote:
On Mar 29, 7:33 pm, Cecil Moore wrote:
Unless it is located at a
physical impedance discontinuity, absolutely nothing happens
because of the V/I ratio.

The last half of the sentence is absolute correct. The V/I ratio is a
result, not a cause.

Yep, I didn't say that very well. Let me try again.
EM wave energy in a transmission line can only change
directions at a physical impedance discontinuity.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

walt wrote:
Richard, it's very uncommon, but on this issue I'm having a difficult
time following you. The only reason that I can conclude for my lack of
understanding is that our definition of 'interference' must be
divergent. So I'll just drop the discussion--OK?

I am ignorant of any technical words (if they exist)
for what I am about to describe so bear with me.

Interference can have totally different outcomes so I
have to ask, are there different kinds of interference?

For instance, the interference between the forward wave
and reflected wave that causes standing waves has no
effect on either the forward wave or the reflected wave.
In an unchanging Z0 environment, the forward wave and
reflected wave pass like ships in the night. For want
of a better term, I will call this type of interference
"temporary interference".

The other type of interference occurs when reflections
are eliminated at a Z0-match or a non-reflective thin-
film. This is *wave cancellation* between two coherent
waves of equal magnitude and opposite phase traveling
in the same path in the direction. For want of a better
term, I will call that type of interference "permanent
interference" since the two waves are canceled and
disappear. Their energy components are redistributed.

Are there any technical words to differentiate between
the two types of interference?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Jim Kelley wrote:
Cecil Moore wrote:
Note that I is "irradiance", not current.

Also note that 'Watt' isn't a unit of irradiance or current.

Close enough for a laser beam. The unit of irradiance is
watts/unit-area. The square of the radius of the laser
beam times pi can be considered to be the unit area. Thus
the unit area is implied and fixed but not specified.
The same is true for a coaxial transmission line. Given the
line, the unit area term can be dropped without error.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Keith Dysart wrote:
This means that reflecting back into the generator from the
left end of the 75 Ohm line will be the same Pref2 = 229.6 W
that exists on the right side of the 75 Ohm line section.

Since ZERO reflected energy exists anywhere on the
75 ohm line, your assertion doesn't make any sense.

Now consider that the 75 ohm line can be one foot
long and everything is the same as the 1WL of 75
ohm line (except the delays).

If adding one foot of 75 ohm line inside the source
completely eliminates reflections, then the source
impedance doesn't matter at all because all it is
delivering is a voltage.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Richard Clark wrote:
So, are you still sleeping with Hecht?

As a matter of fact, I often fall asleep with
"Optics" clutched between my hands. You really
should try reading it sometime.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Apr 2, 9:40 pm, Jim Kelley wrote:
Walter Maxwell wrote:
On Wed, 28 Mar 2007 16:26:10 -0700, Jim Kelley wrote:

Hi Cecil -

We've been over this a hundred times already. The only way to get
past it is for you to try to understand that my comment and Eugene
Hecht's are both true. You need to find a way to understand that
there is no contradiction. You could start by noting that Hecht does
not contradict anything that I said. Nowhere does he claim that
interference redirects energy. That's your claim! And I haven't said
that energy isn't redirected. If redirection of energy takes place,
it takes place by reflection - not interference. It's just basic optics.

73, ac6xg

Sorry Jim, but I take exception to your statement, "If redirection of energy takes place,
it takes place by reflection - not interference."

It is the interference between the forward and reflected voltages and beween the forward and reflected
currents that yields the resultant voltage and current values of rho at the matching point which produces
either a virtual short or a virtual open circuit that causes the re-reflection. I have shown this to be true
in my QEX article of Mar/Apr 1998, entitled, "Examining the Mechanics of Wave Interference in Impedance
Matching. It is also Chapter 23 in Reflections 2.

Using the complex values of rho I have shown the magnitude and phase relationships of the aforementioned
voltages and currents at the stub point that result in a virtual open circuit at the stub point to waves
reflected from a 3:1 mismatched load. The result is no reflections on the line between the stub and the
source, but a 3:1 SWR on the line between the mismatched load and the stub. If you don't have a copy of this
article please let me know and I'll send you one via email.

Walt, W2DU

Hello Walt,

Please know that all of my comments are offered with all due respect,
and there is a lot of respect due, and sincerely felt. However,
though the numbers work out as one would expect given the effects
that are observed, cause can only be attributed to
phenomenon which is observed in nature. Electromagnetic
waves can reflect only from real media. Though I admire the procedure
you have devised for describing the complex effects of these
reflections, the attempts to extend those ideas to describe real (not
virtual) physical phenomena are unsupported from a scientific
standpoint. Inference is insufficient proof.

Specifically: The nature of reflective surfaces does not depend on
whether or not steady state has been reached. Their reflectivity does
not change as a function voltage. Their nature does not depend on
things which lie at the other end of the transmission line - even
though the overall performance of the system certainly does. The
nature of reflective surfaces does not depend on how many times the
wave has bounced back and forth since the signal was initiated. These
things are implied by your claim, unfortunately.

In the case of optical media, reflectivity is determined by the
relative indices of refraction of the optical media comprising the
reflective surface. Neither the
indices, nor their ratio changes in response to illumination.
Likewise, the reflective nature of impedance discontinuities on a
transmission line depend entirely on physical constants analogous to
optical indices of refraction. These attributes do not tend to change
when illuminated by RF.

I thought we had covered this ground back a couple of years ago when
the topic of reflections from virtual shorts and opens came up on this
newsgroup. At that time it became clear that certain of the
predictions made under the model did not match well with reality.
For example, the virtual short circuit which can appear at the
entrance to a stub on a transmission line would, according to the
model, prevent the very currents necessary for creating the virtual
condition from entering the stub in the first place. Reflections can
occur only at physical discontinuities, not at a voltage to current ratio.

I was encouraged by the work we did on your transmission line
impedance matching transformer diagram. In that, it seemed we agreed
that the reflective coefficients were constant, were determined by the
characteristic impedance's of the transmission lines, and that steady
state was in fact comprised of the summation of a long series of
multiple partial reflections. And, it correlates exactly with the
descriptions and drawings of the analogous optical phenomena in the
physics texts.

I really admire your work, Walt, but I feel this one point is clearly
inconsistent with nature. Let me hasten to add that I see nothing at
all wrong with making calculations based on this model. Its utility
and beauty lies in its accuracy at the macroscopic level. I also
think that your treatise on interference as it applies to the
reflections found in RF systems is well done. The error I find is in
your notion of interference as a cause of reflection, which I assume
is extrapolated from your notion that virtual shorts and opens cause
reflections, and, that real reflective coefficients may be calculated
from virtual impedance's.

Best Regards,

Jim Kelley- Hide quoted text -

- Show quoted text -

Hi Jim,

Thanks for taking the time to write such an insightful response--I
was
expecting it.

At the moment I'm in a hotel in Jacksonville, going through pre-op for
spinal
surgery. I'll be home Wednesday, and that will be the earliest I'll
have the
opportunity to review your comments. So I'll get back with you after
having the
time to review it.

Thanks again, Jim,

Revisiting the Power Explanation
 

Cecil Moore wrote:
Jim Kelley wrote:

On Mar 29, 7:33 pm, Cecil Moore wrote:

Unless it is located at a
physical impedance discontinuity, absolutely nothing happens
because of the V/I ratio.


The last half of the sentence is absolute correct. The V/I ratio is a
result, not a cause.


Yep, I didn't say that very well. Let me try again.
EM wave energy in a transmission line can only change
directions at a physical impedance discontinuity.

Accordingly, the fraction of energy that changes direction at a
physical discontinuity is dictated by the physical constants of the
physical discontinuity; index of refraction in the case of optics;
impedance in the case of transmission lines.

73, Jim AC6XG

Revisiting the Power Explanation
 

Cecil Moore wrote:

Jim Kelley wrote:

Cecil Moore wrote:

Note that I is "irradiance", not current.


Also note that 'Watt' isn't a unit of irradiance or current.

Given the
line, the unit area term can be dropped without error.

In the engineering profession, it would probably mean without job; in
science, without publication.

ac6xg

Revisiting the Power Explanation
 

Jim Kelley wrote:
"The error I find is in your notation that virtual shorts and opens
cause reflections, and that real reflection coefficients may be
calculated from virtual impedances."

Impedance is a voltage to current ratio. A low impedance allows much
current from a low impressed voltage. A high impedance only allows a low
current from a high impressed voltage.

A transmission line with a mismatched load, has a reverse or reflected
wave traveling back from the load in addition to the incident wave
traveling toward and impressed on the load. Both waves, incident and
reflected, have the same voltage to current ratio. It equals the Zo of
the line and is enforced by the construction of the assumed uniform
line.

Superposition of the forward or incident wave and the reverse or
reflected wave produces periodic variations in the combined volts and
amps along the line. The rms values of the constituent volts and amps
are likely very steady. It`s their combination which varies.

High voltage points are high impedance points. Low voltage points are
low impedance points.

Severity of voltage and impedance variations along the line depends on
how different the load impedance is from Zo.

A short or an open on the line can produce segments analogous with
series and parallel resonant LC circuits (which behave as shorts and
opens with respect to impedance for example).

Input impedance of an open circuited line of length less than a quarter
wavelength is capacitive. Input impedance of an open line of length
greater than a quarter wavelength but less than a half wavelength is
inductive.

An open-circuited quarter wavelength of line is practically a short
circuit at its input.

A quarter wavelength back from a line short, its impedance is is an open
circuit, and as above, a quarter wavelength back from an open circuit,
the line impedance is a short circuit.

At a line short circuit, incident and reflected current phasors are
in-phase while the incident and reflected voltage phasors are
out-of-phase.

A quarter wave back from the short, the incident and reflected current
phasors are out-of-phase while the the incident and reflected voltage
phasors are in-phase.

A quarter wave back from a hard short on a good line, the reflected
voltage is equal to and of the same phase as the incident voltage.
Therefore there is no potential difference between the incident and
reflected voltages at this point and the current is zero. This is
analogous to connecting identical battery cells in parallel. No current
flows between them. The same can be said of connecting correctly phased
identical transformer windings in parallel.

High voltage and almost zero net current means the impedance is nearly
infinite. This is similar to a good parallel resonant circuit. It is
almost an open circuit. Quarter wave shorted stubs have been used as
"metal insulators" for line support and other purposes.

I have no problem with "virtual shorts and opens". We so called them and
used them in school when I was there over a half century ago.

Examine RADAR TR and anti-TR circuits for examples of virtual shorts and
opens which automatically route the energy to the right places and keep
it out of the wrong places.

Best regards. Richard Harrison, KB5WZI

Revisiting the Power Explanation
 

On Apr 2, 5:19 pm, Cecil Moore wrote:
Keith Dysart wrote:
This means that reflecting back into the generator from the
left end of the 75 Ohm line will be the same Pref2 = 229.6 W
that exists on the right side of the 75 Ohm line section.

Since ZERO reflected energy exists anywhere on the
75 ohm line, your assertion doesn't make any sense.

Please try again after adding 1 more wavelength of 450
Ohm line between the generator and the 75 Ohm line you
added. Kindly explain where the 'reflected power' on
this new section of 450 Ohm line goes.

Now consider that the 75 ohm line can be one foot
long and everything is the same as the 1WL of 75
ohm line (except the delays).

This would be quite incorrect. The impedance presented to
the generator is quite different. Do recall that by design
the generator has a 450 Ohm output impedance so there is
a physical discontinuity at the connection to the 75 Ohm
line. In this case the 75 Ohm line is acting as an impedance
transformer and its length is very relevent. Make it a
multiple half wavelength and the transformation is unity.
I had assumed that this was why in your first analysis
you chose to add one wavelength of line and state that
this would not alter the steady state response, to which,
of course, I agree, though it quite alters the transient
response.

....Keith

Revisiting the Power Explanation
 

Cecil Moore wrote:
walt wrote:

Richard, it's very uncommon, but on this issue I'm having a difficult
time following you. The only reason that I can conclude for my lack of
understanding is that our definition of 'interference' must be
divergent. So I'll just drop the discussion--OK?


I am ignorant of any technical words (if they exist)
for what I am about to describe so bear with me.

Interference can have totally different outcomes so I
have to ask, are there different kinds of interference?

For instance, the interference between the forward wave
and reflected wave that causes standing waves has no
effect on either the forward wave or the reflected wave.
In an unchanging Z0 environment, the forward wave and
reflected wave pass like ships in the night. For want
of a better term, I will call this type of interference
"temporary interference".

The other type of interference occurs when reflections
are eliminated at a Z0-match or a non-reflective thin-
film. This is *wave cancellation* between two coherent
waves of equal magnitude and opposite phase traveling
in the same path in the direction. For want of a better
term, I will call that type of interference "permanent
interference" since the two waves are canceled and
disappear. Their energy components are redistributed.

Are there any technical words to differentiate between
the two types of interference?

When you think of interference as being the instantaneous sum of waves
at a given position and time, then there is really only one kind of
interference to be had - though there are a variety of results which
can be obtained from it. It is useful to bear in mind that fields,
voltages, and currents are what give physical form to the waves in
transmission lines. Whether in a transmission line, or free space it
is the fields which interfere - not power, or energy.

73, Jim AC6XG

Revisiting the Power Explanation
 

On Apr 2, 7:35 pm, (Richard Harrison) wrote:
Jim Kelley wrote:

"The error I find is in your notion that virtual shorts and opens
cause reflections, and that real reflection coefficients may be
calculated from virtual impedances."


I have no problem with "virtual shorts and opens". We so called them and
used them in school when I was there over a half century ago.

Examine RADAR TR and anti-TR circuits for examples of virtual shorts and
opens which automatically route the energy to the right places and keep
it out of the wrong places.

Best regards. Richard Harrison, KB5WZI

Hi Richard,

If I gave the impression that I have a problem with virtual, or
effective impedances then I apollogize. I tried to make it clear that
the only problem is in improperly attributing cause and effect. While
I am not familiar with RADAR TR or anti-TR, I am quite sure that it is
subject to the same physical laws as any other technology.
Electromagnetic waves reflect only from real physical boundaries. JC
Maxwell took great care to describe exactly how that works. If you
feel that RADAR is somehow exempt from these physical laws, then this
might be an opportunity for us both to review our understanding of the
technology.

Best Regards,
Jim AC6XG

Revisiting the Power Explanation
 

On 3 Apr 2007 07:28:45 -0700, "Jim Kelley" wrote:

Electromagnetic waves reflect only from real physical boundaries.

TR/ATR tubes (by their very description and certainly operation)
fulfill that condition.

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

On 3 Apr 2007 07:28:45 -0700, "Jim Kelley" wrote:

I am not familiar with RADAR TR or anti-TR

Hi Jim, and others similarly unfamiliar,

Radar transmission systems have a wide and diverse design topology
that reveals all of the characteristics in an easy and accessibly
small space. Among these diverse applications are the already
mentioned TRansmit and AntiTRansmit tubes. Also are mode shifters,
polarization shifters, choke joints, directional couplers (classic,
not Bruene), isolators, circulators, and separators - a class that
includes what I alluded to, the "Magic T." This last is something
like the classic Hybrid Coupler.

Within these lines you can add either resistive, conductive or
dielectric windows, steps, vanes, and other configurations to create
tuned sections or transitions between sections. Each and all of such
elements readily reduce to wavelength and transmission line mechanics.
Their scale makes them "hands-on."

Returning to the TR/ATR tubes, they simply reside within the path of
the transmission line at a critical harmonic dimension. They consist
of a glass envelope, much like an acorn tube, and it contains a gas
and a simple spark gap and possibly a third exciter electrode. When a
sufficient electric field causes the gap to discharge, this creates
the short that is reflected to a nearby junction. The exciter
electrode is used with a bias to create a very low threshold for
firing. Needless to say, received signals are of insufficient
amplitude to fire the tube, hence the duplexing action.

This, then, creates a different topology between transmit and receive,
and it keeps the MW peak amplitudes out of the receiver front end as
the receive and transmit signal paths are identical otherwise.

Choke joints are passive in nature, but they also exhibit the use of a
tuned cavity that creates a conductive bridge across an otherwise open
gap between transmission line elements (this is a classic mechanism in
the rotary joint of the turning radar antenna).

The RADAR Transmission line systems offers the student vastly more
about transmission line concepts than the rather boring Lecher lines.

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

Jim Kelley wrote:
Accordingly, the fraction of energy that changes direction at a physical
discontinuity is dictated by the physical constants of the physical
discontinuity; index of refraction in the case of optics; impedance in
the case of transmission lines.

Yes, all explained in my energy analysis article.
Personally, I wish whoever introduced virtual
reflection coefficients had not done so.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Jim Kelley wrote:

Cecil Moore wrote:
Given the
line, the unit area term can be dropped without error.

In the engineering profession, it would probably mean without job; in
science, without publication.

The number of watts inside a coaxial transmission line
is understood by any any rational person to be distributed
over the area of the coax. With a fixed-given unit-area,
the Poynting Vector is customarily given in watts, not
watts/unit-area. The same thing applies to watts within
a laser beam.

You are probably right about published white papers. You
are wrong about the engineering profession. All engineers
need to do is get close enough.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Keith Dysart wrote:
Please try again after adding 1 more wavelength of 450
Ohm line between the generator and the 75 Ohm line you
added. Kindly explain where the 'reflected power' on
this new section of 450 Ohm line goes.

It doesn't leave the 450 ohm line as long as the generator
sees 75 ohms as a load. Here is a similar example:

source---75 ohm line--+--1/2WL 450 ohm line---75 ohm load

Where does the reflected energy on the 450 ohm line go?
Since there is a 75 ohm Z0-match at point '+', it circulates
between the load and point '+'. Decrease the length of the
75 ohm line by one inch until it doesn't exist anymore.
The same conditions continue to exist all during that time.
The reflections at point '+' disappear in the process of
wave cancellation which is a type of permanent interference.

Now consider that the 75 ohm line can be one foot
long and everything is the same as the 1WL of 75
ohm line (except the delays).

This would be quite incorrect.

No, this would be 100% correct. One foot of 75 ohm coax
is enough to establish a 75 ohm environment. A 75 ohm
load on the source is enough to establish a 75 ohm
environment. Please see:

http://www.w2du.com/r3ch19a.pdf
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Jim Kelley wrote:
When you think of interference as being the instantaneous sum of waves
at a given position and time, then there is really only one kind of
interference to be had - though there are a variety of results which can
be obtained from it.

If, as you say, interference is only a result and
not a cause, how can there possibly be "a variety
of results which can be obtained from (interference)"?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Jim Kelley wrote:
Electromagnetic waves reflect only from real physical boundaries.

Is the V/I ratio at the heart of a source a "real
physical boundary"? If not, why not?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Cecil Moore wrote:

Jim Kelley wrote:

Electromagnetic waves reflect only from real physical boundaries.

Is the V/I ratio at the heart of a source a "real
physical boundary"? If not, why not?

Exactly two reasons: mu, and epsilon.

A physical boundary is neither defined by, nor affected by voltage,
current, irradiance, luminosity, power, wealth, energy, phase of the
moon, sun spots, kharma, or even gravitas.

Has this become a new point of contention, Cecil? You've said that
you always claimed that waves only reflect from physical boundaries.
And that's all I'm saying.

73, ac6xg

Revisiting the Power Explanation
 

Jim Kelley wrote:
Has this become a new point of contention, Cecil? You've said that you
always claimed that waves only reflect from physical boundaries. And
that's all I'm saying.

When it comes to a source, I seem to have been wrong
about that. A source seems to create its own physical
boundary.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Apr 4, 9:25 pm, Cecil Moore wrote:
When it comes to a source, I seem to have been wrong
about that. A source seems to create its own physical
boundary.

Truly, you have constructed a world view that is much more
complicated than necessary.

Consider the 75 Ohm resistor at the right hand end of a 75 Ohm
transmission line. The load is matched to the line and there
is no discontinuity and (dare I say it?) no reflection.

Want a generator at that end? Put an ideal current source
in parallel with the 75 Ohm resistor. What do you have but a
generator with a 75 Ohm output impedance. And no discontinuity.

Do all the above with a 50 Ohm resistor. As a load, the 50
Ohm resistor is a discontinuity with reflections. As a
generator it has a 50 Ohm output impedance and there is a
discontinuity.

Is not the symmetry rather enticing? And simple?

And using superposition, you can analyze the incident wave
and its reflection, and along with the generated wave, sum
them to obtain the total system response.

Truly elegant. And all so simple.

....Keith

Revisiting the Power Explanation
 

On 4 Apr 2007 19:02:43 -0700, "Keith Dysart" wrote:

On Apr 4, 9:25 pm, Cecil Moore wrote:
When it comes to a source, I seem to have been wrong
about that. A source seems to create its own physical
boundary.

Truly, you have constructed a world view that is much more
complicated than necessary.

Hi Keith,

That isn't the half of it (without going into your further treatment)
our Cecileo will simply twist this admission of error into glowing
self validation - "and yet it moves."

73's
Richard Clark, KB7QHC

Revisiting the Power Explanation
 

Keith Dysart wrote:
Consider the 75 Ohm resistor at the right hand end of a 75 Ohm
transmission line. The load is matched to the line and there
is no discontinuity and (dare I say it?) no reflection.

Yet that violates the convention that reflected energy
absorbed by the source was never sourced. Why do you
think that convention was adopted in the first place?

Is not the symmetry rather enticing? And simple?

Apparently it has enticed you to ignore reality. This
argument has been raging for a good 20 years now. Some
of the brightest engineers in the world still disagree.
Your simplistic theories are easily disproved by a
bench experiment. Why you cling to them is strange.

And all so simple.

Make that simple-minded.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Richard Clark wrote:
That isn't the half of it (without going into your further treatment)
our Cecileo will simply twist this admission of error into glowing
self validation - "and yet it moves."

When I find myself in an error, Richard, I correct it.
What do you do?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

Cecil Moore wrote:
Keith Dysart wrote:
Consider the 75 Ohm resistor at the right hand end of a 75 Ohm
transmission line. The load is matched to the line and there
is no discontinuity and (dare I say it?) no reflection.

Yet that violates the convention that reflected energy
absorbed by the source was never sourced. Why do you
think that convention was adopted in the first place?

I may have misread Keith's posting. I thought we were
talking about sources. Is the above posting about a
75 ohm load devoid of any source?

Consider a 75 ohm load resistor terminating a 75 ohm
transmission line. There are no reflections and the
system is called "flat". Now add a source at that
load end. There will indeed be both forward and reverse
traveling waves.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Apr 5, 9:37 am, Cecil Moore wrote:
Cecil Moore wrote:
Keith Dysart wrote:
Consider the 75 Ohm resistor at the right hand end of a 75 Ohm
transmission line. The load is matched to the line and there
is no discontinuity and (dare I say it?) no reflection.

Yet that violates the convention that reflected energy
absorbed by the source was never sourced. Why do you
think that convention was adopted in the first place?

I may have misread Keith's posting. I thought we were
talking about sources. Is the above posting about a
75 ohm load devoid of any source?

Consider a 75 ohm load resistor terminating a 75 ohm
transmission line. There are no reflections and the
system is called "flat". Now add a source at that
load end. There will indeed be both forward and reverse
traveling waves.

Yes indeed. And the beautiful part is that you can use
superposition to analyze the two directions independantly.

The forward wave reaches the 75 Ohm termination and there
is no reflection. The reverse wave leaves the 75 Ohm generator
and heads down the line.

The total response at any point on the line is the sum of
the two waves at the desired instant at that point.

This works in all cases:
- The waves can have differing phases.
- The waves can have different frequencies.
- The signals do not have to be sinusoids. It works for all
waveshapes: step, square, pulse, you name it.
- The signals don't need to have the same waveshape, though
the arithmetic becomes quite tedious for complex wave
shapes.

The generality is astounding.

Of course sticking to steady state sinusoids at a single
frequency does offer useful simplifications such as 'effective
impedance', 'forward power' and 'reverse power', but care must
be taken with their application since they are not part of
the general solution.

....Keith

Revisiting the Power Explanation
 

On Thu, 05 Apr 2007 13:00:31 GMT, Cecil Moore
wrote:

When I find myself in an error, Richard, I correct it.

Yourself, or the error? Yes, once again your style shows.

Revisiting the Power Explanation
 

Keith Dysart wrote:
The total response at any point on the line is the sum of
the two waves at the desired instant at that point.

True for any *passive* point on the line. Apparently
not true at the heart of a dynamic active source which
is easy to prove on the bench. Seems to me that based
on real-world bench experiments, we must conclude that
the principle of superposition doesn't apply to sources
because the act of applying DC power to the source
changes the configuration of the system which is a
violation of the principle of superposition rules.
Ramo and Whinnery warn us about attaching any real-
world significance to the power dissipation in an
equivalent source.

Obviously, if any system conditions change when power is
applied the basic rules for the superposition principle
have been violated.

Hopefully, you are beginning to understand why the
convention of 100% rejection of reflected energy
by the source was adopted.
--
73, Cecil, w5dxp.com

Revisiting the Power Explanation
 

On Thu, 05 Apr 2007 11:30:59 -0500, Cecil Moore
wrote:

we must conclude that
the principle of superposition doesn't apply to sources
because the act of applying DC power to the source
changes the configuration of the system which is a
violation of the principle of superposition rules.

.... a variation on "yet it moves" as superposition rules explicitly
state how sources are to be treated.

So much for value in the mea culpas, appologies, admissions and
explanations for errors - paid (in debased coin) to the victims of
accuracy.

Revisiting the Power Explanation
 

Richard Clark wrote:
... a variation on "yet it moves" as superposition rules explicitly
state how sources are to be treated.

But since it leads to a contradiction as far as energy
goes, it must be in error. The raging inferno that is
the source is apparently not transparent to waves traveling
in the opposite direction.
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Thu, 05 Apr 2007 23:13:15 GMT, Cecil Moore
wrote:

Richard Clark wrote:
... a variation on "yet it moves" as superposition rules explicitly
state how sources are to be treated.

But since it leads to a contradiction as far as energy
goes, it must be in error.

Superposition is in contradiction to superposition and is in error!
....classic fulfillment of your hackneyed quote of Galileo. Any fires
of purgation you may feel for not accepting Keith's explanation for
(what you call) sources is your own sin - you may as well condemn the
Church (in a muttering whisper, of course) and go back to your cell of
righteousness.

Revisiting the Power Explanation
 

Richard Clark wrote:
Superposition is in contradiction to superposition and is in error!

It should be easy to prove. Hook up two IC-706's in
series driving a 50 ohm dummy load. Install some
feedback to make them coherent. Turn one off and
one on. Then turn the other off and the other on.
Then turn them both on. Do they satisfy the
principle of superposition?
--
73, Cecil http://www.w5dxp.com

Revisiting the Power Explanation
 

On Apr 5, 12:30 pm, Cecil Moore wrote:
Keith Dysart wrote:
The total response at any point on the line is the sum of
the two waves at the desired instant at that point.

True for any *passive* point on the line. Apparently
not true at the heart of a dynamic active source which
is easy to prove on the bench. Seems to me that based
on real-world bench experiments, we must conclude that
the principle of superposition doesn't apply to sources
because the act of applying DC power to the source
changes the configuration of the system which is a
violation of the principle of superposition rules.
Ramo and Whinnery warn us about attaching any real-
world significance to the power dissipation in an
equivalent source.

Obviously, if any system conditions change when power is
applied the basic rules for the superposition principle
have been violated.

Firstly, the principle of conservation of energy always holds.
I don't think anyone has ever disputed that.

Secondly, about superposition. A sufficient condition for
superposition to hold is that all the components are linear
and time-invariant. Examining the ideal transmission lines
used in our simple examples, this is true and superposition
holds on the transmission line. This is also true for the
components in our simple generators so superposition holds
there as well. And it holds for the system consisting of the
generator and the transmission line.

But as I understand, you have done some analysis which brings
superposition into conflict with conservation of energy and
you have concluded that one of them must be wrong. (And having
had strong success with conservation of energy, you have
chosen superposition to be wrong.)

But there is a third choice. Perhaps there is an error in the
way that you have connected the dots between superposition
and conservation of energy. Perhaps, as a result, superposition
and conservation of energy are not in conflict at all.

And this is indeed the case. Since both are true, the error must
be in how the dots are connected.

I suggest you carefully examine the chain of logic that causes
you to conclude that they disagree. That is the path to resolving
the contradiction.

If you would care to lay out the chain that connects the dots, I
would be happy to attempt to help with locating the misstep.

....Keith

Revisiting the Power Explanation
 

Keith Dysart wrote:
This is also true for the
components in our simple generators so superposition holds
there as well.

I've asked Richard how to hook up two IC-706's in
series to get them to meet the requirements of
the superposition principle. Maybe you can show
us how to do it.
--
73, Cecil http://www.w5dxp.com