Question about "Another look at reflections" article.
 

"K1TTT" wrote
...
On Jun 2, 2:12 pm, Cecil Moore wrote:

wave function solutions to maxwell's equations are enough to prove
that for me.

Not a loaded question: How do Maxwell's equations applied to a
standing wave prove that the component forward and reflected waves are
moving at the speed of light in the medium? If it can and if I can
understand it, I wouldn't need to use the photon argument.
--
73, Cecil, w5dxp.com

easy, maxwell's equations don't predict standing waves! they are a
product of superposition and the simplest instrumentation used since
they were first discovered.

"Kundt's tube is an experimental acoustical apparatus invented in 1866 by
German physicist August Kundt[1][2] for the measurement of the speed of
sound in a gas or a solid rod. It is used today only for demonstrating
standing waves and acoustical forces."

Heaviside wrote "Maxwell" equations" much later.

EM waves are the angular waves in the solid body. It would not be easy to
instal the mirror in such body.

You do not know that EM waves were stripped away in 1864.
The Maxwell's math is used in machinery to calculate the torsion vibration.
Maxwell predicted it:

"I propose now to examine magnetic phenomena from a mecha nical point of
view, and to determine what tensions in, or motions of, a medium are capable
of producing the mechanical pheno mena observed. If, by the same hypothesis,
we can connect the phenomena of magnetic attraction with electromagnetic
phenomena and with those of induced currents, we shall have found a theory
which, if not true, can only be proved to be erroneous by experiments which
will greatly enlarge our knowledge of this part of physics."

The hipothesis " be proved to be erroneous by experiments" but we have the
excelent math for thr solid body.
S*

Question about "Another look at reflections" article.
 

"Cecil Moore" wrote
...
On Jun 2, 11:48 am, K1TTT wrote:
my differential calculus is a bit rusty, but i don't think that
equation satisfies the basic wave equation.

My calculus is probably a lot rustier than yours but it would be very
important for this discussion if Maxwell's equations do not work for
the standing wave equation. That would essentially prove that the
mashed-potatoes theory of transmission line energy is bogus.

Maxwell's equations are for angular waves in the solid body.
The transmission line and ends of it (antenna) are exactly like the Kundt's
tubes. In the wires is the electron gas.
S*

Question about "Another look at reflections" article.
 

On 3 jun, 13:23, "Szczepan Bialek" wrote:
*"Cecil Moore" ...
On Jun 2, 11:48 am, K1TTT wrote:

my differential calculus is a bit rusty, but i don't think that
equation satisfies the basic wave equation.
My calculus is probably a lot rustier than yours but it would be very
important for this discussion if Maxwell's equations do not work for
the standing wave equation. That would essentially prove that the
mashed-potatoes theory of transmission line energy is bogus.

Maxwell's equations are for angular waves in the solid body.
The transmission line and ends of it (antenna) are exactly like the Kundt's
tubes. In the wires is the electron gas.
S*

Thanks to all

Hey boys! (Cecil, David, Michael, et al) It is very funny and
entertaining, I enjoy your postingss mostly in "read only" mode
because translate not simple mine ones still being a struggle for
me :-)
.....
Cecil, I never studied standing waves with Maxwell equations (except
in usual examples of cavity resonators cases learning classes), I
studied only classic electric differential solution to the
telegraper's equations.

Hi Keith: We tend to think of energy as a "tangible and real" easely
intuited thing "out there" (as a water or horses) but we must not
forget energy is a really elusive CONCEPT devised to explain changes
in physical systems. Familiarity tend us to fetishize concepts, then
we easily can get caught in troubles type = "Where velocity goes when
the car smash?" :-D :-D. We must be carefully with forces, powers,
velocities, etc. in this sense...
Note how Terman prudenty deals with differential solution of
Telegrapher's equations: "This combinatiosn of voltage and current can
be INTERPRETED as a wave train traveling toward receiver" (1)
(capitalized letters by me).

The very term "standing waves" leads to endless Ham controversies
about concept of "wave" word in our context.(wave as "a disturb that
propagates" and wave as pattern-figure-graphics-representation of
interference pattern of voltage/current measured along the TL). This
"wave pattern" (is it correct to write "wavy" pattern?) do not carry
any energy from one place to another on the TL it is not a "wave" in
the other sense (transport phenomena). What do you think?

(1) Terman F.E. "Radio engineering". McGraw Hill.1947 Ed. page 78

73

Miguel Ghezzi - LU6ETJ

Question about "Another look at reflections" article.
 

On Jun 3, 12:51*am, Cecil Moore wrote:
On Jun 2, 11:48*am, K1TTT wrote:

my differential calculus is a bit rusty, but i don't think that
equation satisfies the basic wave equation.

My calculus is probably a lot rustier than yours but it would be very
important for this discussion if Maxwell's equations do not work for
the standing wave equation. That would essentially prove that the
mashed-potatoes theory of transmission line energy is bogus.
--
73, Cecil, w5dxp.com

well, i dug out mathcad that will do the ugly symbolic differentiation
for me. the standing wave equation can not satisfy the wave equation
derived from maxwell's equations as shown in either 'Fields and Waves
in Communications Electronics' section 1.14 or 'Classical
Electrodynamics' section 6.4. Both of them come down to the
requirement that the second derivative wrt space be proportional to
the second derivative wrt time. The proportionality constant is the
velocity squared. In order to satisfy this the equation must be a
function of the form F(t-x/v), the normal representation is the
complex exponential which can be presented in a form like sin(t)cos(x/
v)-cos(t)sin(x/v) the simpler standing wave equation sin(kx)sin(wt)
has the wrong relationship between space and time and therefor can't
be a solution to the wave equation. When i work through the second
derivatives and collect terms it results in something like
Asin(kx)sin(wt)(k^2-w^2) which makes no sense, even in a dimensional
analysis the units don't work.

The easiest explanation though is still the intuitive one, the
solution of the wave equation derived from maxwell's equations results
in the proportionality constant of 1/c^2 which requires the speed of
the wave to be c in the medium where it is evaluated, there is no way
to get that from the standing wave equation since it is obviously
stationary wrt space.

Question about "Another look at reflections" article.
 

On Jun 4, 6:35*am, K1TTT wrote:
The easiest explanation though is still the intuitive one, the
solution of the wave equation derived from maxwell's equations results
in the proportionality constant of 1/c^2 which requires the speed of
the wave to be c in the medium where it is evaluated, there is no way
to get that from the standing wave equation since it is obviously
stationary wrt space.

Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

Such knowledge also has ramifications for the technique of using the
current on a standing wave antenna to try to predict the delay through
a loading coil. If a Maxwell equation analysis of such a condition
yields bogus results, how can simple current phase measurements be
trusted? If the component traveling waves associated with a loading
coil were used in order to obtain a valid Maxwell equation analysis, I
wonder what would be the predicted delay through the coil?
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 4, 2:12*pm, Cecil Moore wrote:
On Jun 4, 6:35*am, K1TTT wrote:

The easiest explanation though is still the intuitive one, the
solution of the wave equation derived from maxwell's equations results
in the proportionality constant of 1/c^2 which requires the speed of
the wave to be c in the medium where it is evaluated, there is no way
to get that from the standing wave equation since it is obviously
stationary wrt space.

Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.


Such knowledge also has ramifications for the technique of using the
current on a standing wave antenna to try to predict the delay through
a loading coil. If a Maxwell equation analysis of such a condition
yields bogus results, how can simple current phase measurements be
trusted? If the component traveling waves associated with a loading
coil were used in order to obtain a valid Maxwell equation analysis, I
wonder what would be the predicted delay through the coil?
--
73, Cecil, w5dxp.com

this becomes MUCH harder to analyze. the transmission line case is
easy because the equations collapse to a single linear dimension, so
you can write your simple standing wave equation with a single sin(kx)
term. in a solenoid, especially a finite length solenoid, and double
especially because the length may be an appreciable fraction of a
wavelength, there is no such simple representation for the fields.
i'm not even sure what software would provide an adequate model of
something like that... the turns are too close for me to trust nec
based programs with out lots more research, and i'm pretty sure finite
element programs like ansoft/maxwell would not be able to handle the
change in current due to length and radiation. measurement of the
currents in coils like that would also be hard because of the radiated
fields and the shielding needed to prevent measurement errors from
probe lengths in the field... i would only trust fiber optic sensed
probes that were small and self contained, at least that way you would
not be distorting the field with probes or trying to cancel out pickup
from probe cables coupling to the antenna.

Question about "Another look at reflections" article.
 

On 4 jun, 14:26, K1TTT wrote:
On Jun 4, 2:12*pm, Cecil Moore wrote:





On Jun 4, 6:35*am, K1TTT wrote:

The easiest explanation though is still the intuitive one, the
solution of the wave equation derived from maxwell's equations results
in the proportionality constant of 1/c^2 which requires the speed of
the wave to be c in the medium where it is evaluated, there is no way
to get that from the standing wave equation since it is obviously
stationary wrt space.

Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.



Such knowledge also has ramifications for the technique of using the
current on a standing wave antenna to try to predict the delay through
a loading coil. If a Maxwell equation analysis of such a condition
yields bogus results, how can simple current phase measurements be
trusted? If the component traveling waves associated with a loading
coil were used in order to obtain a valid Maxwell equation analysis, I
wonder what would be the predicted delay through the coil?
--
73, Cecil, w5dxp.com

this becomes MUCH harder to analyze. *the transmission line case is
easy because the equations collapse to a single linear dimension, so
you can write your simple standing wave equation with a single sin(kx)
term. *in a solenoid, especially a finite length solenoid, and double
especially because the length may be an appreciable fraction of a
wavelength, there is no such simple representation for the fields.
i'm not even sure what software would provide an adequate model of
something like that... the turns are too close for me to trust nec
based programs with out lots more research, and i'm pretty sure finite
element programs like ansoft/maxwell would not be able to handle the
change in current due to length and radiation. *measurement of the
currents in coils like that would also be hard because of the radiated
fields and the shielding needed to prevent measurement errors from
probe lengths in the field... i would only trust fiber optic sensed
probes that were small and self contained, at least that way you would
not be distorting the field with probes or trying to cancel out pickup
from probe cables coupling to the antenna.- Ocultar texto de la cita -

- Mostrar texto de la cita -

Hello and good day all:

I believe perhaps I am not translating/understanding well your posts,
Cecil and David, I post some comments to your consideration.

As I learnt, basic electromagnetic energy propagation Maxwell
equations are satisfied by a traveling wave moving in one direction.
Also I learnt standing waves in a TL results of two of them traveling
in opposite directions (as I understand this is not a questioned point
in this newsgroup), but SW equation it is not a Maxwell eq. solution
but a mathematical result of interference among them. For that reason
directly replacing this one in electroamagnetic energy propagation
Maxwell diff. eqs to satisfy it, do not work, because SW do not travel
anywhere!.
Energy not flowing beyond nodes it is a true, but only for ending
nodes!
Could this be what confuses those who think energy do not cross
INTERNAL TL nodes?

Electromagnetic waves are energy transport phenomenom, SWs not. We can
interpret last ones as a "result of the transport
phenomenom" (interference) = Energy is "trapped" in a resonant ideal
line, as is "trapped" in a resonant ideal cavity, as light ii is
"trapped" in a optical ideal cavity.

Do we see a simple case: If we think in a half wave resonant line we
can interpret/describe its internal state as two traveling waves
(inside system transport) or with a standing wave dynamic interchange
of energy between E and H field without radiation (not transport). In
longer line it is the same: we can describe its internal state a two
waves traveling between end boundaries (transport) or a sistem (line)
located [but not f(x)] energy interchange among magnetic and electric
field. (I said not f(x), because nodes and antinodes are "FIELDS (E
and H) nodes and antinodes", but not "ENERGY nodes or antinodes" (as
we know, where H is 0, E is maximun...)
Seems to me this does not violate any quantum or clasic laws :)

73

Miguel Ghezzi - LU6ETJ

Question about "Another look at reflections" article.
 

On Jun 4, 12:26*pm, K1TTT wrote:
this becomes MUCH harder to analyze. the transmission line case is
easy because the equations collapse to a single linear dimension, so
you can write your simple standing wave equation with a single sin(kx)
term. in a solenoid, especially a finite length solenoid, and double
especially because the length may be an appreciable fraction of a
wavelength, there is no such simple representation for the fields.

Well maybe it is much harder using Maxwell's equations but maybe there
is a simple representation. See what you think about this idea. At the
following web site is an impedance calculator that will yield the
characteristic impedance and velocity factor of a loading coil so the
coil can be analyzed the same way as a transmission line. (We also can
model the whip using EZNEC and, like a transmission line stub, equate
the feedpoint impedance to the impedance of a lossy open-circuit
stub.) We know the Z0 of the whip will be a few hundred ohms.

http://hamwaves.com/antennas/inductance.html

The velocity factor of the specified coil can be calculated from the
axial propagation factor in radians per meter.

So please assume a frequency of 4 MHz and a typical six inch long
bugcatcher loading coil with a Z0 of 3800 ohms and a VF of 0.024. All
losses in/from the coil can be lumped together as if they were normal
transmission line losses. The electrical length of the coil can be
calculated from the physical length and VF. I don't see that it is all
that "MUCH harder to analyze" than a transmission line example with
the same amount of losses.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 4, 1:26*pm, K1TTT wrote:
On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

....Keith

Question about "Another look at reflections" article.
 

On Jun 3, 4:03*pm, lu6etj wrote:
Thanks to all

Hey boys! (Cecil, David, Michael, et al) It is very funny and
entertaining, I enjoy your postingss mostly in "read only" mode
because translate not simple mine ones still being a struggle for
me :-)
....
Cecil, I never studied standing waves with Maxwell equations (except
in usual examples of cavity resonators cases learning classes), I
studied only classic electric differential solution to the
telegraper's equations.

Hi Keith: *We tend to think of energy as a "tangible and real" easely
intuited thing "out there" (as a water or horses) but we must not
forget energy is a really elusive CONCEPT devised to explain changes
in physical systems. Familiarity tend us to fetishize concepts, then
we easily can get caught in troubles type = "Where velocity goes when
the car smash?" :-D :-D. We must be carefully with forces, powers,
velocities, etc. in this sense...
Note how Terman prudenty deals with differential solution of
Telegrapher's equations: "This combinatiosn of voltage and current can
be INTERPRETED as a wave train traveling toward receiver" (1)
(capitalized letters by me).

Terman does seem to be extraordinarily careful with his language.

The very term "standing waves" leads to endless Ham controversies
about concept of "wave" word in our context.(wave as "a disturb that
propagates" and wave as pattern-figure-graphics-representation of
interference pattern of voltage/current measured along the TL). This
"wave pattern" (is it correct to write "wavy" pattern?) do not carry
any energy from one place to another on the TL it is not a "wave" in
the other sense (transport phenomena). What do you think?

I tend to agree. Wave is an overloaded term and this leads to some of
the confusion. There are some phenomena that transport energy which
have a wavy nature. This does not mean that every thing with a wavy
nature is transporting energy.

In particular, it does not mean that when there is a situation in
which
energy is not being transported (e.g. a zero on a transmission line),
that just because the conditions on the line can be described by
decomposing into two waves going in opposite directions, that these
two waves are carrying energy.

Attempting to do this, and believing that these decomposed waves
actually
represent energy flows leads to having to answer questions like "where
does the reflected energy go"? When I first started lurking in this
group
about a decade and half ago, the 'obvious' answer accepted by many was
that it went in to the final and fried the tube. Many have moved
beyond
this simplicity, but some have not yet moved as far as they need to.

....Keith

Question about "Another look at reflections" article.
 

On Jun 4, 10:39*pm, Keith Dysart wrote:
On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. since they
are not real waves that propagate and move energy the P=VI formula is
not correct. you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results.

Question about "Another look at reflections" article.
 

On Jun 4, 7:54*pm, K1TTT wrote:
On Jun 4, 10:39*pm, Keith Dysart wrote:





On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. *since they
are not real waves that propagate and move energy the P=VI formula is
not correct. *you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results

My apologies for being insufficiently precise. Where ever I wrote
P=VI,
please substitute P(t)=V(t)I(t).

That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

....Keith

Question about "Another look at reflections" article.
 

Keith Dysart wrote:
On Jun 4, 1:26 pm, K1TTT wrote:
On Jun 4, 2:12 pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.
definately. another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.



The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

The above example has current but no voltage, There are no storage
elements, only resistors.

Inductance and capacitance are storage elements. You might find those in
a model of a transmission line, but not in this example.



So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

I think you are looking to hard at a small part of the picture and not
seeing what else is going on.

Question about "Another look at reflections" article.
 

On Jun 4, 8:23*pm, joe wrote:
Keith Dysart wrote:
On Jun 4, 1:26 pm, K1TTT wrote:
On Jun 4, 2:12 pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.
definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. *The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

An excellent example. Let's draw it.

A
+----\/\/\------+-----/\/\/\----+
| |
--- -
- ---
| B |
+---------------+---------------+

Between A and B the voltage is zero. I contend that there is no energy
flowing from the left half of the circuit to the right half. To
demonstrate this, compute the energy contributed by the battery on the
left. It is equal to the energy consumed by the resistor on the left.
Similarly for the battery and resistor on the rigtht. No energy flows
across the plane A-B.

If you still disagree, what is the power flowing across A-B?

....Keith

Question about "Another look at reflections" article.
 

"Keith Dysart" wrote
...

I tend to agree. Wave is an overloaded term and this leads to some of
the confusion. There are some phenomena that transport energy which
have a wavy nature. This does not mean that every thing with a wavy
nature is transporting energy.

In particular, it does not mean that when there is a situation in
which
energy is not being transported (e.g. a zero on a transmission line),
that just because the conditions on the line can be described by
decomposing into two waves going in opposite directions, that these
two waves are.

Also each pulse in the wave is carrying energy.

Attempting to do this, and believing that these decomposed waves
actually represent energy flows leads to having to answer questions like
"where
does the reflected energy go"? When I first started lurking in this
group about a decade and half ago, the 'obvious' answer accepted by many was
that it went in to the final and fried the tube.

Members of this Group should know that in microwave oven are the standing
waves, In the Manual is " when the amount of food is small, sharp points and
sharp edges on metal objects can initiate a corona discharge, a "Saint
Elmo's Fire," which behaves the same as a flame and can set fire to the food
and the oven if allowed to continue for long. Aluminum foil can become a
blow torch!"

Each pulse of the both waves travelling in the opposite direction is
carrying energy. The energy cummulate and can destroy the tube or the oven.

Many have moved beyond this simplicity, but some have not yet moved as far
as they need to.

It is important to know that the standing waves are possible only in
compressible medium.
"Maxwell's equations" are for the incompressible electricuty.
S*

Question about "Another look at reflections" article.
 

On Jun 5, 12:19*am, Keith Dysart wrote:
On Jun 4, 7:54*pm, K1TTT wrote:



On Jun 4, 10:39*pm, Keith Dysart wrote:

On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. *since they
are not real waves that propagate and move energy the P=VI formula is
not correct. *you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results

My apologies for being insufficiently precise. Where ever I wrote
P=VI,
please substitute P(t)=V(t)I(t).

That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

...Keith

right, and this brings up another key error that a detailed look at
standing waves points out. go look at one of the animations of
standing waves and you will note that in each cycle they go from tall
peaks to a flat line and then back to peaks. so if you use p=vi what
is the energy in the line when either field is zero from end to end?
if you answer zero, then where did it go? it is obviously impossible
for the energy in the line to go to zero everywhere every half cycle
as that would require propagation faster than light, and some external
place for all that energy to dump to. so calculating power that way
is worthless with standing waves.

The real die hard standing wave fanatics will look closer and realize
they can represent calculate power in each field separately and make
it slosh back and forth between electric fields and magnetic fields.
That representation may be interesting, but is nothing more than
studying the energy stored in a resonant LC circuit. it doesn't go
anywhere, it just alternates between the electric and magnetic fields.

Question about "Another look at reflections" article.
 

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. *The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

you need to go back to circuits 101 and retake the undergraduate lab
intro where they teach you about measuring current and voltage. your
basic problem statement above is malformed since you can not measure
the voltage 'at the center'. voltages always have to be taken between
two points.

now if you REALLY want to be confused, ignore circuits 101 and draw
any circuit with as many components in it as you want as long as there
is only ONE loop. so connect AC or DC sources, inductors, capacitors,
resistors, around in a circle. start measuring voltage across each
one as you go around the circle and add them up. the result will
ALWAYS be zero. (go read about Kirchhoff's laws, here is one
reference http://www.bowest.com.au/library/theorems.html).

Note that of course these do not apply to transmission line problems
or antennas.

Question about "Another look at reflections" article.
 

On Jun 5, 7:42*am, K1TTT wrote:
On Jun 5, 12:19*am, Keith Dysart wrote:
That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

...Keith

right, and this brings up another key error that a detailed look at
standing waves points out. *go look at one of the animations of
standing waves and you will note that in each cycle they go from tall
peaks to a flat line and then back to peaks. so if you use p=vi *what
is the energy in the line when either field is zero from end to end?

We need to carefully understand the meaning of the words. Power is
energy
that is moving; the SI unit is the watt or joule per second. The unit
for energy is the joule.

When the voltage or current is zero everywhere, there is no power,
that
is, no energy is moving. The energy is stored on the line where it
happens
to be. As the voltage or current rises again from zero, the energy is
now moving in the direction opposite to the direction it was moving
before
the line was zero everywhere. At a point where the voltage or current
is
always zero, no energy moves. The energy sloshes back and forth
between
the points in the line that it never crosses.

it just alternates between the electric and magnetic fields

This is true, but the energy also changes location as it does this,
leading
to energy flow (or power), but the energy does not cross any point
where
the voltage or current is always zero.

When the current everywhere is zero, no energy is flowing, and the
energy
is stored as voltage in the capacitance of the line. And those
voltages are
at maximum and will soon begin to decrease as the energy begins to
flow the
other way.

Similarly, when the voltage is zero everywhere, the energy is stored
as
current in the inductance of the line.

....Keith

Question about "Another look at reflections" article.
 

K1TTT wrote:
Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

you need to go back to circuits 101 and retake the undergraduate lab
intro where they teach you about measuring current and voltage. your
basic problem statement above is malformed since you can not measure
the voltage 'at the center'. voltages always have to be taken between
two points.


Funny, Keith understood exactly what I meant. I find it hard to believe
you couldn't figure out the implied reference point. (I.e., what the
supplies were connected to.)


now if you REALLY want to be confused, ignore circuits 101 and draw
any circuit with as many components in it as you want as long as there
is only ONE loop. so connect AC or DC sources, inductors, capacitors,
resistors, around in a circle. start measuring voltage across each
one as you go around the circle and add them up. the result will
ALWAYS be zero. (go read about Kirchhoff's laws, here is one
reference http://www.bowest.com.au/library/theorems.html).


Since you include AC sources, the voltages must all be measured at the
same time. Circuits 101 should tell you that.




Note that of course these do not apply to transmission line problems
or antennas.


Which was part of my point, picking at some details may not lead you to
the proper view of what is going on.

Question about "Another look at reflections" article.
 

On Jun 4, 5:39*pm, Keith Dysart wrote:
... if the voltage or current is always 0,
there must be no energy flowing.

Keith, you keep leaving out the word "net". If the current on each
side of a zero-current point is not zero, all that zero current
measurement means is there is equal energy flowing in both directions
so there is no *net* energy flow. The fact that Maxwell's equations
cannot be used on your condition of interest should be a clue that
something is wrong with your concepts and/or logic. You are
essentially saying that there is no traffic on the Golden Gate Bridge
because the north and south traffic averages out to zero. It is a
faulty concept. That zero net traffic keeps on wearing out the
roadway.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 4, 5:39*pm, Keith Dysart wrote:
So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

Your equation is for DC power. The equation for net AC power is
P=V*I*cos(theta). Since, for a pure standing wave, the net voltage is
always 90 degrees out of phase with the net current, the net power at
ALL points is zero, not just at the I=0 point. cos(theta) is ALWAYS
zero for a pure standing wave whether I=0 or not - so your argument is
moot. For a pure standing wave, P = V*I*cos(theta) is ALWAYS zero. I
or V going to zero cannot make it more zero than it already is.

For a pure standing wave, the forward Poynting vector and the
reflected Poynting vector sum to zero AT ALL POINTS.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 4, 7:19*pm, Keith Dysart wrote:
If, for all time,
the current or voltage is 0, then so is the energy flow.

You left out the word "net" again. Indeed, there is zero *net* energy
flow in a pure standing wave. It is technically not a wave because it
doesn't transfer energy and momentum. The forward and reflected
Poynting vectors can be of any magnitude. They are just equal in
magnitude whatever that magnitude might be.

Keith, could you refresh my memory on those instantaneous power
equations that you once published. Given a forward wave and a
reflected wave, what was your equation for instantaneous power? None
of my references consider EM standing wave instantaneous power to be
important enough to present a mathematical treatment of the subject.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 5, 6:53*am, K1TTT wrote:
... draw
any circuit with as many components in it as you want as long as there
is only ONE loop.

Just a nit - there is a frequency at which the voltages will begin not
summing to zero. That's when it is time to discard the lumped-circuit
model and go to the distributed network model or Maxwell's equations.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 5, 7:08*am, Keith Dysart wrote:
We need to carefully understand the meaning of the words. Power is
energy that is moving;

Correction, it must be moving past a point, not just moving laterally
from an inductance to a capacitance and back. There is zero net
average power anywhere on a wire containing a pure standing wave.
Therefore, there is zero net energy flow anywhere on a pure standing
wave, not just at the zero current and zero voltage points. The
average power in a pure standing wave is zero whether the current or
voltage is zero or not. What is important for power is the phase angle
between the net current phasor and the net voltage phasor which is
always 90 degrees for a pure standing wave. The fact that *power is a
scalar with no negative values* and *the average power is zero*, leads
one to conclude that instantaneous power is just a mathematical
curiosity. Exactly how can the instantaneous power average out to zero
average power if there are no negative values of instantaneous power?
Seems to me to be one of those numerous "undefined" or "indeterminate"
conditions that unfortunately exists in mathematics. When you solve a
quadratic equation for a resistance and get plus or minus 100 ohms, do
you actually start searching for a -100 ohm resistor? Then why, when
you know the average power is zero, do you ask us to go searching for
some negative instantaneous power that doesn't exist?

Since power is energy flow *per unit time*, I don't see how power
calculated over zero unit time can be anything more than a
mathematical curiosity existing in human brains - and unrelated to
reality. When one integrates instantaneous standing wave power over
one cycle and gets anything except zero, one needs to recognize the
error or one's ways.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On 5 jun, 11:22, Cecil Moore wrote:
On Jun 5, 7:08*am, Keith Dysart wrote:

We need to carefully understand the meaning of the words. Power is
energy that is moving;

Correction, it must be moving past a point, not just moving laterally
from an inductance to a capacitance and back. There is zero net
average power anywhere on a wire containing a pure standing wave.
Therefore, there is zero net energy flow anywhere on a pure standing
wave, not just at the zero current and zero voltage points. The
average power in a pure standing wave is zero whether the current or
voltage is zero or not. What is important for power is the phase angle
between the net current phasor and the net voltage phasor which is
always 90 degrees for a pure standing wave. The fact that *power is a
scalar with no negative values* and *the average power is zero*, leads
one to conclude that instantaneous power is just a mathematical
curiosity. Exactly how can the instantaneous power average out to zero
average power if there are no negative values of instantaneous power?
Seems to me to be one of those numerous "undefined" or "indeterminate"
conditions that unfortunately exists in mathematics. When you solve a
quadratic equation for a resistance and get plus or minus 100 ohms, do
you actually start searching for a -100 ohm resistor? Then why, when
you know the average power is zero, do you ask us to go searching for
some negative instantaneous power that doesn't exist?

Since power is energy flow *per unit time*, I don't see how power
calculated over zero unit time can be anything more than a
mathematical curiosity existing in human brains - and unrelated to
reality. When one integrates instantaneous standing wave power over
one cycle and gets anything except zero, one needs to recognize the
error or one's ways.
--
73, Cecil, w5dxp.com

Hi. ¡Good evening (here) to all..!

We need to carefully understand the meaning of the words. Power is
energy that is moving;

Since the energy can be dissipated also transmitted, If we talk in
power FLUX terms (instead power only), I think the issue it would be a
little more understandable because surfaces may have associated
vectors (with "power moving" I believe you are thinking about power
crossing an imaginary surface)
(Note: when I spoke about "unidimensional" nature of a TL space I am
pointing to "degrees of freedom" of energy flux circumscribed to its
physical path, of course).

For the sake of example we could imaginate a coaxial TL provided with
a resistive inner conductor and perfectly conductive outer one. On
such TL perhaps we could clearly visualize power flux vector (Poynting
vector) "slanted" towards inner conductor to "see" -through simple
vectorial decomposition on (over?) the inner wire and pependicular to
it directions both = transmission and dissipative nature of
phenomenom.
At the same time I believe will be also more ease to account for net
power FLUX of opposite directions traveling waves and do not confuse
with net power being zero, leading us to the idea of zero energy
stored in a ideal resonant TL. Note: In my last mensage I forget to
clear that with "resonant line" I was speaking about a section of TL
with its ends open or shorted (or a mix) to force a "chemically pure"
standing wave :)

I believe we always must escape from words as "real" or
"true" (outside of safe environments such mathematics or digital
logic), because "she" easily leads us to the Holy Inquisition
dangers :) Let us the Wave word to be free for jointing with
standing, sine, hand, etc, etc. and do we make efforts to understand
its conceptual meaning on each context :)

73

Miguel Ghezzi - LU6ETJ

Question about "Another look at reflections" article.
 

On Jun 5, 12:08*pm, Keith Dysart wrote:
On Jun 5, 7:42*am, K1TTT wrote:

On Jun 5, 12:19*am, Keith Dysart wrote:
That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

...Keith

right, and this brings up another key error that a detailed look at
standing waves points out. *go look at one of the animations of
standing waves and you will note that in each cycle they go from tall
peaks to a flat line and then back to peaks. so if you use p=vi *what
is the energy in the line when either field is zero from end to end?

We need to carefully understand the meaning of the words. Power is
energy
that is moving; the SI unit is the watt or joule per second. The unit
for energy is the joule.

When the voltage or current is zero everywhere, there is no power,
that
is, no energy is moving. The energy is stored on the line where it
happens
to be. As the voltage or current rises again from zero, the energy is
now moving in the direction opposite to the direction it was moving
before
the line was zero everywhere. At a point where the voltage or current
is
always zero, no energy moves. The energy sloshes back and forth
between
the points in the line that it never crosses.

it just alternates between the electric and magnetic fields

This is true, but the energy also changes location as it does this,
leading
to energy flow (or power), but the energy does not cross any point
where
the voltage or current is always zero.

When the current everywhere is zero, no energy is flowing, and the
energy
is stored as voltage in the capacitance of the line. And those
voltages are
at maximum and will soon begin to decrease as the energy begins to
flow the
other way.

Similarly, when the voltage is zero everywhere, the energy is stored
as
current in the inductance of the line.

...Keith

sorry, you are of course correct that there could still be energy
stored in the fields when the instantaneous power is zero... wrote
that before having enough caffeine this morning.

Question about "Another look at reflections" article.
 

On Jun 5, 1:59*pm, Cecil Moore wrote:
On Jun 5, 6:53*am, K1TTT wrote:

... draw
any circuit with as many components in it as you want as long as there
is only ONE loop.

Just a nit - there is a frequency at which the voltages will begin not
summing to zero. That's when it is time to discard the lumped-circuit
model and go to the distributed network model or Maxwell's equations.
--
73, Cecil, w5dxp.com

agreed in general. the initial premise was a couple resistors and
batteries... this is strictly true only for instantaneous voltages
across lumped components.

Question about "Another look at reflections" article.
 

On Jun 5, 9:42*am, Cecil Moore wrote:
On Jun 4, 7:19*pm, Keith Dysart wrote:

If, for all time,
the current or voltage is 0, then so is the energy flow.

You left out the word "net" again.

Not left out. No need to mention since this is the only energy
involved.

Indeed, there is zero *net* energy
flow in a pure standing wave. It is technically not a wave because it
doesn't transfer energy and momentum.

Certainly a standing wave is not a wave that transfers energy.

Keith, could you refresh my memory on those instantaneous power
equations that you once published. Given a forward wave and a
reflected wave, what was your equation for instantaneous power?

Choose a point on the line. Measure the instantaneous voltage and
current at that point. Multiply them together. You have the
instantaneous energy flow at that point and time. Integrate over
a full cycle (assuming a repetitive signal), divide by the period
and you have the average energy flow.

None
of my references consider EM standing wave instantaneous power to be
important enough to present a mathematical treatment of the subject.

Definitely not of interest for standing waves (which everyone agrees
are not really waves), but any decent text will derive
Pavg=Vrms*Irms*cos(theta) for sinusoids by doing exactly the steps
I mention above.

You are welcome.

....Keith

Question about "Another look at reflections" article.
 

On Jun 5, 10:22*am, Cecil Moore wrote:
On Jun 5, 7:08*am, Keith Dysart wrote:

We need to carefully understand the meaning of the words. Power is
energy that is moving;

Correction, it must be moving past a point, not just moving laterally
from an inductance to a capacitance and back.

Yes, indeed. And so it does. At any point where the voltage or current
is not always 0, energy moves back and forth. This can be readily seen
by computing P(t)=V(t)*I(t) at such a point. P(t) will be a sinusoid
describing the energy flow in the time domain.

There is zero net
average power anywhere on a wire containing a pure standing wave.

Yes, but to understand the details, time domain analysis is a great
asset. You need to move away from just averages to understand what
is going on.

Therefore, there is zero net energy flow anywhere on a pure standing
wave, not just at the zero current and zero voltage points. The
average power in a pure standing wave is zero whether the current or
voltage is zero or not.

True, but the instantaneous power is not.

What is important for power is the phase angle
between the net current phasor and the net voltage phasor which is
always 90 degrees for a pure standing wave. The fact that *power is a
scalar with no negative values* and *the average power is zero*, leads
one to conclude that instantaneous power is just a mathematical
curiosity.

On the contrary. It is computable and measurable.

Exactly how can the instantaneous power average out to zero
average power if there are no negative values of instantaneous power?

There are indeed negative values. These occur when the energy is
flowing
in the other direction, i.e. the direction opposite to that
represented
by positive values of power.

In P(t)=V(t)I(t), when V(t) and I(t) have different signs, P(t) is
negative.

Seems to me to be one of those numerous "undefined" or "indeterminate"
conditions that unfortunately exists in mathematics. When you solve a
quadratic equation for a resistance and get plus or minus 100 ohms, do
you actually start searching for a -100 ohm resistor? Then why, when
you know the average power is zero, do you ask us to go searching for
some negative instantaneous power that doesn't exist?

Ahhhhh, but it does. One does not need to search far if one starts
with
a time domain analysis.

Since power is energy flow *per unit time*, I don't see how power
calculated over zero unit time can be anything more than a
mathematical curiosity existing in human brains - and unrelated to
reality.

Well, this is the basis for calculus...
- instantaneous velocity
- instantaneous acceleration
- instantaneous jerk
- instantaneous voltage
- instantaneous rate of change of voltage
- instantaneous power

All are well understood concepts... and related to reality.

When one integrates instantaneous standing wave power over
one cycle and gets anything except zero, one needs to recognize the
error or one's ways.

In a 'pure standing wave', such integration does result in zero, as
expected. But looking at the time domain details helps reveal the
fine grained behaviour that is obscured when only averages are
considered.

....Keith

Question about "Another look at reflections" article.
 

On Jun 5, 9:29*am, Cecil Moore wrote:
On Jun 4, 5:39*pm, Keith Dysart wrote:

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

My apologies for being too terse for you. Please use P(t)=V(t)I(t)

Your equation is for DC power. The equation for net AC power is
P=V*I*cos(theta).

This simplified form works for sinusoids. It is derived from
P(t)=V(t)I(t),
but loses information since the result is just the average value.

Since, for a pure standing wave, the net voltage is
always 90 degrees out of phase with the net current, the net power at
ALL points is zero, not just at the I=0 point. cos(theta) is ALWAYS
zero for a pure standing wave whether I=0 or not

Well so it appears when you use the simplified form, but if you use
P(t)=V(t)I(t), that is, do a bit of time domain analysis, one finds
that energy is moving back in forth within the line. It only does
not cross those points where V or I is always 0.

- so your argument is moot.
For a pure standing wave, P = V*I*cos(theta) is ALWAYS zero. I
or V going to zero cannot make it more zero than it already is.

The difference will be easy to see if you analyze in the time domain
rather than just using the averages.

....Keith

Question about "Another look at reflections" article.
 

On Jun 5, 6:15*pm, Keith Dysart wrote:
Certainly a standing wave is not a wave that transfers energy.

Since a standing "wave" is not a wave, by definition, doesn't that
give you a clue that you may be being duped by an illusion?
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 5, 1:05 pm, lu6etj wrote:
Hi. ¡Good evening (here) to all..!

We need to carefully understand the meaning of the words. Power is
energy that is moving;

Since the energy can be dissipated also transmitted, If we talk in
power FLUX terms (instead power only), I think the issue it would be a
little more understandable because surfaces may have associated
vectors (with "power moving" I believe you are thinking about power
crossing an imaginary surface)
(Note: when I spoke about "unidimensional" nature of a TL space I am
pointing to "degrees of freedom" of energy flux circumscribed to its
physical path, of course).

For the sake of example we could imaginate a coaxial TL provided with
a resistive inner conductor and perfectly conductive outer one. On
such TL perhaps we could clearly visualize power flux vector (Poynting
vector) "slanted" towards inner conductor to "see" -through simple
vectorial decomposition on (over?) the inner wire and pependicular to
it directions both = transmission and dissipative nature of
phenomenom.
At the same time I believe will be also more ease to account for net
power FLUX of opposite directions traveling waves and do not confuse
with net power being zero, leading us to the idea of zero energy
stored in a ideal resonant TL. Note: In my last mensage I forget to
clear that with "resonant line" I was speaking about a section of TL
with its ends open or shorted (or a mix) to force a "chemically pure"
standing wave :)

I believe we always must escape from words as "real" or
"true" (outside of safe environments such mathematics or digital
logic), because "she" easily leads us to the Holy Inquisition
dangers :) Let us the Wave word to be free for jointing with
standing, sine, hand, etc, etc. and do we make efforts to understand
its conceptual meaning on each context :)

Good day Miguel,

I do not disagree with anything you have written, but I do think it
is much too early to introduce Poynting vectors and lossy conductors
to the discussion.

Some of the posters to this group have basic misunderstandings of
the behaviour of transmission lines and using Poynting to address
these misunderstandings is like trying to use quantum mechanics
to address misunderstandings of Newton’s third law. And it will
be just as unsuccessful.

The basic misunderstanding is believing that a reflected wave
necessarily and always transports energy. Rather than using
basic circuit theory to demonstrate that this assumption is
incorrect, these posters introduce Poynting, optics and
photons to reinforce their beliefs. Believing that a
reflected wave necessarily transports energy then begs the
question ‘where does this energy go?’. At one time it was
a commonly held belief that this reflected ‘energy’ entered
the transmitter and fried the final. This notion has generally
disappeared, but has been replaced by faulty concepts
attempting to explain how the reflected ‘energy’ is re-reflected
so that is does not enter the transmitter. And all this effort
is expended because of a misunderstanding of the nature of
reflected ‘energy’.

Until these basic behaviours are properly understood, optics,
photons and Poynting merely assist with obfuscation.

....Keith

Question about "Another look at reflections" article.
 

On Jun 5, 6:28*pm, Keith Dysart wrote:
There are indeed negative values. These occur when the energy is
flowing in the other direction, ...

Let's take a close look at the illusion that you are seeing and not
comprehending. Observe a snapshot of the instantaneous power envelope
of a traveling wave. It is a sinusoidal envelope with peak
instantaneous power levels and zero instantaneous power levels. When
it is traveling in the forward direction we consider that to be
positive power. When it is traveling in the reverse direction, we
consider that to be negative power. It is only a directional
*convention* not proof that negative power exists. The only waves that
can exist as waves on a transmission line are traveling waves.

Since the forward wave and reverse wave do not interact while Z0
remains constant, they have zero effect on each other and we can just
simply algebraically add the two instantaneous powers to obtain the
net instantaneous power. Thus, when the instantaneous power in the
forward wave is a greater magnitude than the instantaneous power in
the reverse wave, the net instantaneous power is positive. When the
instantaneous power in the forward wave is a lesser magnitude than the
instantaneous power in the reverse wave, the net instantaneous power
is negative. At the point where they are equal, the net instantaneous
power is zero. This is the illusion, based on net instantaneous power,
that you are observing. Please note that net instantaneous power is an
oxymoron. Is it net or is it instantaneous? How can it be both?

All you are observing is that sometimes the instantaneous power in the
forward traveling wave is more, less, or equal to the instantaneous
power in the reverse traveling wave which causes the net instantaneous
Poynting vector direction to alternate. But it is all a moot point
because photons cannot perform the feats of magic that you are
ascribing to them. You are simply being fooled by an illusion based on
the misguided algebraic addition of two separate and distinct
instantaneous powers that you believe are interacting but while Z0
remains constant, they are not interacting in any way and it is
impossible for the photons to change direction without a physical
cause. Your mashed-potatoes version of energy doesn't even obey
Maxwell's equations. Why do you think the concept can possibly be
meaningful?

In "Optics", Hecht says instantaneous power is "of limited utility."
You seem to have discovered that limit, stepped over it, and stepped
in it. :-)
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 5, 6:33*pm, Keith Dysart wrote:
This simplified form works for sinusoids. It is derived from
P(t)=V(t)I(t),
but loses information since the result is just the average value.

Note that P(t)=V(t)I(t) is just Pfor(t) - Pref(t) which loses
information when the subtraction is performed and is not important in
any meaningful way. If, as you say, loss of information is to be
avoided, you should be using Pfor(t) and Pref(t) instead of net P(t).
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 6, 7:54*am, Keith Dysart wrote:
Some of the posters to this group have basic misunderstandings of
the behaviour of transmission lines and using Poynting to address
these misunderstandings is like trying to use quantum mechanics
to address misunderstandings of Newton’s third law. And it will
be just as unsuccessful.

Translation: I object to anything, including technical references and
laws of physics, that shoots my argument down. :-)

The basic misunderstanding is believing that a reflected wave
necessarily and always transports energy.

Please define "transport". An EM wave cannot exist without ExH energy.
If the energy associated with an EM reflected wave is equal to zero,
then the reflected wave cannot be measured and doesn't exist. But we
know that reflected waves do exist just by looking in a mirror -
causing the reflected photonic energy to be incident upon our retinas.
All of the transported energy in the reflected wave in a transmission
line is recovered during the transient state immediately following key
down. Tracking reflected energy from beginning to end result is not
difficult - optical physicists have been doing it for decades. But,
unlike your ideas, their results do not require the violation of the
laws of physics.
--
73, Cecil, w5dxp.com

Question about "Another look at reflections" article.
 

On Jun 6, 9:55*am, Cecil Moore wrote:
On Jun 5, 6:33*pm, Keith Dysart wrote:

This simplified form works for sinusoids. It is derived from
P(t)=V(t)I(t),
but loses information since the result is just the average value.

Note that P(t)=V(t)I(t) is just Pfor(t) - Pref(t) which loses
information when the subtraction is performed and is not important in
any meaningful way. If, as you say, loss of information is to be
avoided, you should be using Pfor(t) and Pref(t) instead of net P(t).
--
73, Cecil, w5dxp.com

In the past you have insisted that only average powers were relevent.
Does this mean you are ready to look at power (i.e. energy flow) in
the
time domain?

If so, you might appreciate
http://sites.google.com/site/keithdysart/radio6.

....Keith

Question about "Another look at reflections" article.
 

On Jun 6, 10:09*am, Cecil Moore wrote:
On Jun 6, 7:54*am, Keith Dysart wrote:

Some of the posters to this group have basic misunderstandings of
the behaviour of transmission lines and using Poynting to address
these misunderstandings is like trying to use quantum mechanics
to address misunderstandings of Newton’s third law. And it will
be just as unsuccessful.

Translation: I object to anything, including technical references and
laws of physics, that shoots my argument down. :-)

A rather poor translation.

The basic misunderstanding is believing that a reflected wave
necessarily and always transports energy.

Please define "transport". An EM wave cannot exist without ExH energy.
If the energy associated with an EM reflected wave is equal to zero,
then the reflected wave cannot be measured and doesn't exist. But we
know that reflected waves do exist just by looking in a mirror -

You do seem to mention looking in the mirror quite frequently, as if
it
had something to do with understanding the behaviour of a
transmission
line.

causing the reflected photonic energy to be incident upon our retinas.
All of the transported energy in the reflected wave in a transmission
line is recovered during the transient state immediately following key
down. Tracking reflected energy from beginning to end result is not
difficult - optical physicists have been doing it for decades. But,
unlike your ideas, their results do not require the violation of the
laws of physics.

My main idea is basic electricity. If the voltage or current is
always 0, so is the power. This does not violate any physics of which
I am aware.

....Keith

Question about "Another look at reflections" article.
 

On Jun 6, 9:45*am, Cecil Moore wrote:
On Jun 5, 6:28*pm, Keith Dysart wrote:

There are indeed negative values. These occur when the energy is
flowing in the other direction, ...

Let's take a close look at the illusion that you are seeing and not
comprehending. Observe a snapshot of the instantaneous power envelope
of a traveling wave. It is a sinusoidal envelope with peak
instantaneous power levels and zero instantaneous power levels. When
it is traveling in the forward direction we consider that to be
positive power. When it is traveling in the reverse direction, we
consider that to be negative power. It is only a directional
*convention* not proof that negative power exists. The only waves that
can exist as waves on a transmission line are traveling waves.

Ahhh. I see part of your problem. You are thinking envelopes.

You need to change your point of view to be a particular point on the
line.
At this point, there is a function that describes the voltage: V(t).
It
may or may not be a sinusoid. There is a function for the current:
I(t).
And from these can trivialy be derived a function for power:
P(t)=V(t)I(t).

When I clip my instantaneous voltmeter across a line and measure 0 for
all time, I can confidently say that no energy is flowing, for there
is
not. I am curious as to what you would answer?

In "Optics", Hecht says instantaneous power is "of limited utility."
You seem to have discovered that limit, stepped over it, and stepped
in it. :-)

Well, Hecht may have his limitations when dealing with Optics, but
there
is no reason to expect these same limitations to apply to circuit
analysis.

....Keith

Question about "Another look at reflections" article.
 

On 6 jun, 18:00, Keith Dysart wrote:
On Jun 6, 9:45*am, Cecil Moore wrote:

On Jun 5, 6:28*pm, Keith Dysart wrote:

There are indeed negative values. These occur when the energy is
flowing in the other direction, ...

Let's take a close look at the illusion that you are seeing and not
comprehending. Observe a snapshot of the instantaneous power envelope
of a traveling wave. It is a sinusoidal envelope with peak
instantaneous power levels and zero instantaneous power levels. When
it is traveling in the forward direction we consider that to be
positive power. When it is traveling in the reverse direction, we
consider that to be negative power. It is only a directional
*convention* not proof that negative power exists. The only waves that
can exist as waves on a transmission line are traveling waves.

Ahhh. I see part of your problem. You are thinking envelopes.

You need to change your point of view to be a particular point on the
line.
At this point, there is a function that describes the voltage: V(t).
It
may or may not be a sinusoid. There is a function for the current:
I(t).
And from these can trivialy be derived a function for power:
P(t)=V(t)I(t).

When I clip my instantaneous voltmeter across a line and measure 0 for
all time, I can confidently say that no energy is flowing, for there
is
not. I am curious as to what you would answer?

In "Optics", Hecht says instantaneous power is "of limited utility."
You seem to have discovered that limit, stepped over it, and stepped
in it. :-)

Well, Hecht may have his limitations when dealing with Optics, but
there
is no reason to expect these same limitations to apply to circuit
analysis.

...Keith

Hi folks, good night (from here).

I do not disagree with anything you have written, but I do think it
is much too early to introduce Poynting vectors and lossy conductors
to the discussion.

Hello Keith, Yes, I understand your comment, I introduced Poynting
vector only because both, energy and power, are scalars and we can not
talk about scalars having direction without get in conceptual
troubles; flux of power instead, have direction because surface vector
presence in its definition gives directive characteristics to power
crossing an imaginary surface.
Slanted flux of electromagnetic power (Poynting) due resistive
conductor simply seems to me a good example of a power flux in a TL
not totally coincident with axial direction to provide a little more
supporting to "directive" notion of Power Flux.
However IMHO power flux do not seems to me more complicated than
power, work, voltage, potential, energy, E and H fields, etc. All of
them -I believe- are not very simple stuff :(, but they are very
funny and interesting, indeed...!! :D. What do you think?
......
Please would you mind tell me why "sine wave" it is not a correct use
of "wave" word. The only dictionary I have = "Oxford advanced
english dictionary of current english defines wave as: "move to and
fro, up and down", I believe also in english there are word qualifiers
(sine, traveling, standing, etc) who specify the precise meaning of
them in diverse contexts. Am I wrong about this?.
.....
Sorry by my insistence about convenience of discuss about "models".
Please let me bring a citation:
"At times, two quite differents models may serve equally well, but
eventually one is usually found to prevail, not because it is right,
but because it is both more convenient and more logically constructed.
After all, models are constructed for convenience in thinking and
recording, not as photographic images of nature"
(From "Electromagnetic Engineering", Ronold W.P. King (PhD), page 94.
McGraw Hill.1946).
.....
I studied "Principle of Conjugates Impedance Matching" in my early
student days and the "mirror reflection" explained by Walter Maxwell
in his article agree with my undestanding about "where the reflected
waves go" because to balance magnitudes it is necessary that they
found a full mismatch on its way (path?) to generator. My own limited
analisis led me to the same notion even without conjugate match if I
calculate Incident and reflected voltages values in a half wave TL (as
my early thread example),
As I said, reading Cecil's web page quarter wave line examples led me
to considerate another possible representations of the problem, in
addition Owen's own ideas about it also made me consider the issue
from another point of view.

Thank you very nuch.

Miguel Ghezzi - LU6ETJ

Question about "Another look at reflections" article.
 

"lu6etj" wrote
...
.....
Please would you mind tell me why "sine wave" it is not a correct use
of "wave" word. The only dictionary I have = "Oxford advanced
english dictionary of current english defines wave as: "move to and
fro, up and down", I believe also in english there are word qualifiers
(sine, traveling, standing, etc) who specify the precise meaning of
them in diverse contexts. Am I wrong about this?.

Sine wave is an ideal wave. The motion to and fro are simmetrical.
In reality no such. The wave source push the medium strongly but it come
back with the lower intensity.
For this reason the wave flow transmits the energy from the source to
distant places.
In fluids take place also the mass flow.
S*