Standing-Wave Current vs Traveling-Wave Current
 

Roy Lewallen wrote:
3. How do you resolve this with the graphs in Terman and your
explanation of the voltage and current being in quadrature everywhere
along the line?

The standing wave voltage is *ALWAYS* in quadrature with
the standing wave current at all points and at all times.
If the total voltage is not in quadrature with the total
current, there is a traveling wave in the mixture.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Denny wrote:
1. A standing wave is not 'standing' in time... It phase rotates at
the same rate as the excitation frequency...

Yes, but that rotation is occurring at a fixed point on
the wire. The standing wave is not moving - it is just
rotating in a fixed place on the wire. Standing waves
do not flow. They are basically an illusion created by
the superposition of two traveling waves.

2. It is real because I can measure it with a volt meter and I can
extract power from it with a lamp, simultaneously..

You cannot extract steady-state power from standing waves.
You can only extract steady-state power from traveling waves.

However, you can extract transient-state power from standing
waves. That's what happens at key-up - the energy in the
standing wave is radiated after the source is disconnected.

Try this thought... A Tesla coil (automobile spark coil) with no load
on the output is all standing wave voltage and no current - so
according to some has no power... Touch your finger to it...

When you touch your finger to it, it is no longer steady-state.
Standing waves can and do give up their energy as joules/sec
power during transient states. But they change during that
process.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 12:01*am, Cecil Moore wrote:
Richard Harrison wrote:
Keith Dsart wrote:
"Therefore, the forward and reverse waves can not be transferring energy
across these points."

Waves in motion are transporting energy no matter how their constituents
seem to add at a particular point.

We can make Keith's assertion true by the addition of one
word.

"Therefore, the forward and reverse waves cannot be transferring
*net* energy across these points. As Ramo and Whinnery say about
the forward and reflected Poynting vectors:

With an open circuited line, I agree that there is no
net energy transfer at any point on the line. At most
points on the line, there is energy sloshing back and
forth, but netting to zero.

My statement about those 90 degree points where the
voltage or current is always 0 is much stronger: NO
energy transfer.

This follows inexorably from P(x,t) = V(x,t) * I(x,t).

If you disagree with the general applicability of this
equation, please indicate when it can and can not be
applied.

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
And could someone who likes to write "standing
wave power" (Yuri perhaps?) please provide an
unambiguous definition? It does not have to be
the "right" definition, or agreed by all, just
any definition which is unambiguous.

Confusion reigns because of steady-state short cuts.

The power density (Poynting vector) of any EM wave
is ExH. EM waves cannot exist without a power density.

For pure standing waves, ExH = 0. Therefore, a pure
standing wave is technically NOT an EM wave. It
doesn't move and contains no power. In many ways,
it is an illusion.

A standing wave is a math model created in the human
mind as a useful shortcut. Shortcuts do NOT dictate
reality. Reality is supposed to do the dictating.

Standing waves are the results of the superposition
of two traveling waves. Any power extracted comes
from the component traveling waves, not from the
standing waves. For pure standing waves:

ExH = V*I*cos(A) = 0 watts (per unit area)
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Dave wrote:
"Denny" wrote:
1. A standing wave is not 'standing' in time... It phase rotates at
the same rate as the excitation frequency...
If the phase is rotating then V and I are changing - else Feynman is
rotating in his grave...

true, it is 'standing' in space. it does not move along the line.

How can such a signal be used to measure the delay through
a mobile loading coil?

why do i even bother... time to start plonking more of the ones who refuse
to learn and reduce the noise level on here even more.

What you have to do is overcome their programming -
that math models dictate reality, not vice versa.
Just keep dripping on that stone - someday it will
wear away.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Cecil Moore wrote:
Gene Fuller wrote:
Where do you get so many goofy ideas? Do you have any references at
all that support your contention that standing wave energy does not
meet the definition of EM energy? I have been in the wave business
professionally for about 40 years, and I have read many technical
papers, reference books, and text books. I have yet to encounter
anything that indicated the inferior nature of standing waves in the
energy community.

I guess the authors of the textbooks never thought anyone
would be so ignorant as to believe that EM waves can stand
still. :-)

EM waves are photonic in nature must travel at the speed of
light in the medium. A standing wave stands still and oscillates
in place. Therefore, A standing wave is not an EM wave - It is
something else, by definition.

Cecil,

Thanks, you completely confirmed my suspicion. This photonic limitation
is something that exists only in your head.

8-)

73,
Gene
W4SZ

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 9:26*am, "Dave" wrote:
"Keith Dysart" wrote in message

...
On Dec 23, 10:12 am, "Dave" wrote:

Are you really prepared to throw away P = VI?

yes, when the V and I are the superimposed voltage and current that you
insist are the real current and voltage on the line.

They are the real current and voltage. I can measure them
with voltmeters and ammeters.

Directional wattmeters measure the real current and
voltage and perform some arithmetic on these measured
values to display "forward power" and "reflected power".

"Forward and reflected power" are derived from the
real voltage and current.

In my analysis, P(x,t) = V(x,t) * I(x,t) is the equation that means
the power at any point and time can by obtained by measuring the
actual
voltage and current on the line at the point and time of interest.

try to look at it this way. *when you look at the forward and reflected
waves separately it is intuitively obvious how the power calculation shows
the flow along the line with each wave. *however, when you look at standing
waves you get spots every 1/4 wave where either V(x,t) or I(x,t) is ALWAYS
zero... by V*I this means the power at that point is ALWAYS zero. *since
power is just the measure of the flow of energy, and energy can neither be
created nor destroyed then in the traveling wave there can be no energy flow
past those points. *where it is obvious from the individual Vf(x,t) and
Vr(x,t) or If(x,t) and Ir(x,t) that are ALWAYS related by Z0 at every point
on the line that power does flow both directions. *an obvious contradiction

Absolutely. And many readers resolve the contradiction in the
wrong direction.

And then are willing to throw away P = VI.

and if you can't see it by this point i give up.

Are you sure you want to throw away this ability? Are you sure you
want to claim that instantaneous power can NOT be obtained by
multiplying the instaneous measured voltage by the instanteous
measured current?

i want to throw away this falicy and replace it with the real physically
correct calculation.

Throwing this away will invalidate much.

only in your mind.

I have said it enough times now, and hate repeating myself... so you can
live with your poor misguided assumptions and formula. *i have shown the
obvious errors

I'd suggest that remains to be seen.

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
Are you really saying that if I measure the instantaneous
voltage and the instantaneous current then I can NOT multiply
them together to obtain the instantaneous power?

It certainly works some of the time.

If I can not do it all the time, when can I do it?

Actually, "multiply" is ambiguous. You need to take
the *dot product* of the voltage and current to
obtain power.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Cecil Moore wrote:
Keith Dysart wrote:
And could someone who likes to write "standing
wave power" (Yuri perhaps?) please provide an
unambiguous definition? It does not have to be
the "right" definition, or agreed by all, just
any definition which is unambiguous.

Confusion reigns because of steady-state short cuts.

The power density (Poynting vector) of any EM wave
is ExH. EM waves cannot exist without a power density.

For pure standing waves, ExH = 0. Therefore, a pure
standing wave is technically NOT an EM wave. It
doesn't move and contains no power. In many ways,
it is an illusion.

A standing wave is a math model created in the human
mind as a useful shortcut. Shortcuts do NOT dictate
reality. Reality is supposed to do the dictating.

Standing waves are the results of the superposition
of two traveling waves. Any power extracted comes
from the component traveling waves, not from the
standing waves. For pure standing waves:

ExH = V*I*cos(A) = 0 watts (per unit area)

Cecil,

Do you simply make this stuff up in some arbitrary fashion, or is there
a method to your madness?

With such profound statements as, "a pure standing wave is technically
NOT an EM wave", it you might either offer some sort of reference or
start planning your trip to Stockholm.

73,
Gene
W4SZ

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
And P = V * I seems rather fundamental, so V or
I is always 0, then P must always be 0.

Make that *NET* power and you will be correct. There is
zero *NET* power transfer in pure standing waves.

Since Pfor = Pref, then Pfor - Pref = 0
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 9:39*am, "Dave" wrote:
"Keith Dysart" wrote in message

...
On Dec 23, 11:33 am, Roger wrote:

You are basing this conclusion on the observation that Power = V*I, and
because we can not detect V or I at some points in the standing wave,
then V*I is zero at these points. Correct math, but wrong conclusion.
Are you really saying that if I measure the instantaneous
voltage and the instantaneous current then I can NOT multiply
them together to obtain the instantaneous power?

It certainly works some of the time.

If I can not do it all the time, when can I do it?

you can do it when it makes physical sense. *

Can you kindly articulate the rules you use to know
when it is appropriate to use P = V * I?

At a minimum, the rules should cover DC circuits,
AC circuits, and transmission lines with various
excitations and terminations. Be sure that the
rules cover 60 Hz circuits and transmission lines
since this is a common application of P = V * I.

it does not make sense in
standing waves for all the obvious reasons that i have pointed out. *it does
make sense in the individual traveling waves. *just accept what your little
swr meter tells you, it shows the forward power and reflected power, that is
all you need and the only powers that make sense.

And for a challenging use case, please consider two
circuits connected together. The circuits are in black
boxes so you do not know their details, but the voltage
on the connection between the circuits is measured as
10 V RMS at 4 MHz. The current is measured as 0.

How much energy is being transferred between the
circuits?

1) P = VI, so 0.
2) P = VI some of the time, so there is insufficient
detail to answer the question.

Do you choose 1), 2) or perhaps some third answer?

...Keith

PS. The connection between the circuits is very small
so that it is possible that it is part of a
transmission line that continues into each box,
but you can not be sure.

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 10:49*am, Cecil Moore wrote:
Keith Dysart wrote:
Are you really saying that if I measure the instantaneous
voltage and the instantaneous current then I can NOT multiply
them together to obtain the instantaneous power?

It certainly works some of the time.

If I can not do it all the time, when can I do it?

Actually, "multiply" is ambiguous. You need to take
the *dot product* of the voltage and current to
obtain power.

Since the discussion concerns real numbers and not
vectors, "multiply" is exactly correct.

But you haven't answered the hard part of the question.
When does P(x,t) not equal V(x,t) * I(x,t)?

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 10:30*am, Cecil Moore wrote:
Keith Dysart wrote:
And could someone who likes to write "standing
wave power" (Yuri perhaps?) please provide an
unambiguous definition? It does not have to be
the "right" definition, or agreed by all, just
any definition which is unambiguous.

Confusion reigns because of steady-state short cuts.

The power density (Poynting vector) of any EM wave
is ExH. EM waves cannot exist without a power density.

For pure standing waves, ExH = 0. Therefore, a pure
standing wave is technically NOT an EM wave. It
doesn't move and contains no power. In many ways,
it is an illusion.

A standing wave is a math model created in the human
mind as a useful shortcut. Shortcuts do NOT dictate
reality. Reality is supposed to do the dictating.

Standing waves are the results of the superposition
of two traveling waves. Any power extracted comes
from the component traveling waves, not from the
standing waves. For pure standing waves:

ExH = V*I*cos(A) = 0 watts (per unit area)

I am having great difficulty matching the words you
wrote with the request for an unambiguous definition
of "standing wave power".

Are you saying the concept is meaningless?
Or do you think you provided a definition?

I really wanted a definition from someone
who thought the "standing wave power" had
meaning.

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 10:52*am, Cecil Moore wrote:
Keith Dysart wrote:
And P = V * I seems rather fundamental, so V or
I is always 0, then P must always be 0.

Make that *NET* power and you will be correct. There is
zero *NET* power transfer in pure standing waves.

Oooppps. Make that "so *if* V or I is always 0".

And if I had meant *NET* I would have written "net".

Since Pfor = Pref, then Pfor - Pref = 0

Isn't that superposition of power? Something that
most agree is not a legal operation.

In any case, for sure it is 'average' power.

All my examples are using instantaneous power.
If the instantaneous power is always 0, the
average power can not be different.

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

"Keith Dysart" wrote in message
...

Can you kindly articulate the rules you use to know
when it is appropriate to use P = V * I?

it is extremely simple. use traveling waves then V*I works everywhere all
the time. use standing waves and it fails. period, end of story.

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 10:30 am, Cecil Moore wrote:

A standing wave is a math model created in the human
mind as a useful shortcut. Shortcuts do NOT dictate
reality. Reality is supposed to do the dictating.

Standing waves are the results of the superposition
of two traveling waves. Any power extracted comes
from the component traveling waves, not from the
standing waves. For pure standing waves:

ExH = V*I*cos(A) = 0 watts (per unit area)

OH NO! even cecil has it right! carry on cecil, you are more persistent
than i am. i have enough other stuff to do right now... i had some fun
yesterday while the wx was bad here, today there are better things to do,
like scrape ice and sand the driveway, and fix a yagi that got tipped in the
ice/wind last weekend. so you all carry on, i'm sure cecil will set you all
straight now so i'll leave it in his capable hands.

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 11:18*am, "Dave" wrote:
"Keith Dysart" wrote in message

...

Can you kindly articulate the rules you use to know
when it is appropriate to use P = V * I?

it is extremely simple. *use traveling waves then V*I works everywhere all
the time. *use standing waves and it fails. *period, end of story.

What happens on a line that is terminated in a real
impedance that is not equal to Z0?

There are aspects of both travelling waves and
standing waves present on the line.

Is it appropriate to use P = V * I?

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

"Dave" wrote in message
news:cwPbj.1073$ML6.117@trndny04...


you can do it when it makes physical sense. it does not make sense in
standing waves for all the obvious reasons that i have pointed out. it
does make sense in the individual traveling waves. just accept what your
little swr meter tells you, it shows the forward power and reflected
power, that is all you need and the only powers that make sense.


Little SWR meter shows forward AND reflected power in one direction, and
reflected power only in reverse direction. Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart to
calculate SWR, when there are no standing waves and no power in them?
Laying waves or sitting waves???

Seems to me that the PROBLEM is that some consider standing wave to be some
imaginary, stopped, frozen wave, no good, while some of us consider standing
wave to be the result of superposition of forward and reverse waves, that
can be (their components) measured, current heats when flowing through
resistance, voltage "burns" when poor dielectric.
Like there is standing wave current, but no standing wave, huh????
Or are we forgetting that we are dealing with electromagnetic waves?
Can someone sort out the terminology and definitions?

Yuri, K3BU

Standing-Wave Current vs Traveling-Wave Current
 

"Keith Dysart" wrote in message
...

What happens on a line that is terminated in a real
impedance that is not equal to Z0?

There are aspects of both travelling waves and
standing waves present on the line.

Is it appropriate to use P = V * I?

it is always appropriate to use P=V*I on the forward and reflected traveling
waves. it is never appropriate to use it on the standing wave voltage and
current. period... plonk.

Standing-Wave Current vs Traveling-Wave Current
 

Roger wrote:
Roger wrote:
Keith Dysart wrote:
clip ....

In the setup above used for "standing waves"
it can be seen that there is zero power in
the line every 90 degrees back from the open
end. At a zero power point, no energy is
being transferred. Therefore, the forward
and reverse waves can not be transferring
energy across these points. Conclusion:
forward and reverse waves do not always
transport energy.

....Keith

Hi Keith,

You are basing this conclusion on the observation that Power = V*I,
and because we can not detect V or I at some points in the standing
wave, then V*I is zero at these points. Correct math, but wrong
conclusion.

What you are forgetting is that power is also found from Power = V^2/Zo
and Power = I^2*Zo. More accurately, on the standing wave line,
Power = (V^2 + I^2)/Zo. This is why a SWR power meter detects both
current and voltage from the standing wave.

This will also be true on the quarter wave stub, which is really 1/2
wave length long electrically, when you consider the time required for
the wave to go from initiation to end and back to beginning point.
Power is stored on the stub during the 1/2 cycle energized, and then
that stored power acts to present either a high or low impedance to
the next 1/2 cycle, depending upon whether the stub is shorted or open.

I think you did a very good job in building your theory. It was only
at the end (where I think we need to consider additional ways of
measuring power) that we disagree.

73, Roger, W7WKB

Haste makes waste, and errors as well. The standing wave power
equation is incorrect. It should read "Power = V^2 / Zo + I^2 * Zo"

Sorry for any inconvenience, and for the several postings it will
probably stimulate.

73, Roger, W7WKB

Contributing to this news group always carries the risk of making errors
and this was a DUZZY! "Power = V^2 / Zo + I^2 * Zo" IS VERY WRONG AND
SHOULD NOT BE USED AS DESCRIBED. Thanks to several folks for pointing
this out.

I was writing to describe a concept, a concept that was obviously wrong
upon closer examination.

73, Roger, W7KB

Standing-Wave Current vs Traveling-Wave Current
 

"Yuri Blanarovich" wrote in message
...

"Dave" wrote in message
news:cwPbj.1073$ML6.117@trndny04...


you can do it when it makes physical sense. it does not make sense in
standing waves for all the obvious reasons that i have pointed out. it
does make sense in the individual traveling waves. just accept what your
little swr meter tells you, it shows the forward power and reflected
power, that is all you need and the only powers that make sense.


Little SWR meter shows forward AND reflected power in one direction, and
reflected power only in reverse direction. Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart
to calculate SWR, when there are no standing waves and no power in them?
Laying waves or sitting waves???

Seems to me that the PROBLEM is that some consider standing wave to be
some imaginary, stopped, frozen wave, no good, while some of us consider
standing wave to be the result of superposition of forward and reverse
waves, that can be (their components) measured, current heats when flowing
through resistance, voltage "burns" when poor dielectric.
Like there is standing wave current, but no standing wave, huh????
Or are we forgetting that we are dealing with electromagnetic waves?
Can someone sort out the terminology and definitions?

Yuri, K3BU

last time, real simple. there ARE standing current waves. there ARE
standing voltage waves. There ARE NOT standing power waves.

Standing-Wave Current vs Traveling-Wave Current
 

On Dec 24, 11:50*am, "Yuri Blanarovich" wrote:
Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart to
calculate SWR, when there are no standing waves and no power in them?

Why indeed? The decision of Bird Electronic to build
an instrument that measured actual line voltage and
current and then compute forward or reverse voltage
but display the result in watts has lead to enormous
confusion about the nature of forward and reverse
waves.

If only they had decided to display forward or
reverse volts, life would be much better. People
would not have internalized "forward and reverse
power" to such a degree.

On the other hand, it would have then required
more arithmetic to compute actual power.

But they did it, and it can not be undone.

Do you have an unambiguous definition of "standing
wave power" that can be used?

...Keith

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
Except that V(x,t) and I(x,t) are not, in general, related by Z0.

From "Fields and Waves ..." by Ramo & Whinnery, 2nd edition:

V(x,t) = V*e^j(wt-kx) + V'*e^j(wt+kx)

I(x,t) = [V*e^j(wt-kx) - V'*e^j(wt+kx)]/Z0

No. The two wave view is merely an alternate set of expressions
which, when summed (i.e. using superposition), provide the actual
voltage and current on the line. These alternate expressions are
obtained by algebraic maniupulation of the more fundamental
descriptive equations.

Methinks you are confusing cause and effect. The standing
wave is not the cause of the two traveling waves.

In my analysis, P(x,t) = V(x,t) * I(x,t) is the equation that means
the power at any point and time can by obtained by measuring the
actual voltage and current on the line at the point and time of interest.

Make that the *NET* power and you will have it nailed.

Are you sure you want to throw away this ability? Are you sure you
want to claim that instantaneous power can NOT be obtained by
multiplying the instaneous measured voltage by the instanteous
measured current?

When the instantaneous voltage is the sum of two more elementary
voltages (same for current) then you are reporting the *NET*
results, not the underlying component results. The *NET* results
do not dictate reality.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Dave wrote:
try to look at it this way. when you look at the forward and reflected
waves separately it is intuitively obvious how the power calculation shows
the flow along the line with each wave.

This is a very old equation:

Pnet = PLoad = Pfor - Pref = Vfor*Ifor - Vref*Iref

For a pure standing wave it reduces to:

Pnet = Pfor - Pref = 0 or |Pfor| = |Pref|

There is zero net power transfered in a standing wave
so Vtot*Itot*cos(A) = ZERO *at every point* along a
lossless line containing pure standing waves, not just
at the Vtot=0 and Itot=0 points, but *everywhere*.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
With an open circuited line, I agree that there is no
net energy transfer at any point on the line. At most
points on the line, there is energy sloshing back and
forth, but netting to zero.

It is not "sloshing" back and forth unless you consider
the speed of light to be "sloshing". That's EM photonic
energy. If it's not traveling at the speed of light, it
doesn't exist. I would describe the movement of EM wave
energy as "racing" back and forth.

My statement about those 90 degree points where the
voltage or current is always 0 is much stronger: NO
energy transfer.

No *NET* energy transfer because the energy being transfered
in either direction is equal to the other direction. This
would be true of incoherent EM waves and even applies to
any and every type of wave energy.

This follows inexorably from P(x,t) = V(x,t) * I(x,t).

Yes, it certainly does for *NET* power.
Pnet = Pfor - Pref = 0 for ideal standing waves.

If you disagree with the general applicability of this
equation, please indicate when it can and can not be
applied.

It can be correctly applied when the person doing the
applying understands what it really means in reality.

I suggest you take a look at HP's s-parameter AP 95-1.
If you square the normalized s-parameter voltage equations,
you get power directly. The s-parameter equations are
designed that way.

b1 = s11*a1 + s12*a2 standard s-parameter voltage equation

a1^2 = Forward Power incident upon the impedance discontinuity

b1^2 = Reflected Power = (s11*a1 + s12*a2)^2
Power reflected from the impedance discontinuity

When a1^2 - b1^2 = 0

what do you think is the physical meaning of Reflected
Power being equal to:

Pref = (s11*a1)^2 + 2(s11*a1)(s12*a2) + (s12*a2)^2 ???

Do you recognize the irradiance equation from optical
engineering?

Ptot = P1 + P2 + 2*SQRT(P1*P2)cos(A)
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Gene Fuller wrote:
This photonic limitation
is something that exists only in your head.

Good Grief, Gene, I don't have time to teach you
quantum electrodynamics. Go read a book that tells
you about the nature of photons. It is also the
cornerstone of relativity.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
They are the real current and voltage. I can measure them
with voltmeters and ammeters.

They are the *NET* current and voltage. You can separate
them into their elementary components with directional
couplers.

"Forward and reflected power" are derived from the
real voltage and current.

From the *NET* voltage and current by someone who understands
the nature of forward and reflected EM waves.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Gene Fuller wrote:
With such profound statements as, "a pure standing wave is technically
NOT an EM wave", it you might either offer some sort of reference or
start planning your trip to Stockholm.

Gene, here is a true/false quiz for you. If you have a
reference that disagrees with the obvious answers, please
quote it.

1. Is EM wave energy photonic in nature? ________

2. Do photons move at the speed of light in a medium? ______

3. Do standing waves move at the speed of light? _______

If the answers are yes, yes, and no, then standing waves
have been eliminated from the set of EM waves.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
And for a challenging use case, please consider two
circuits connected together. The circuits are in black
boxes so you do not know their details, but the voltage
on the connection between the circuits is measured as
10 V RMS at 4 MHz. The current is measured as 0.

How much energy is being transferred between the
circuits?

Inside each black box is a 50 ohm signal generator equipped
with a circulator and a 50 ohm load resistor. The signal
generators are outputting identical 10 V RMS phase-locked
signals.

Signal generator #1 "sees" the 50 ohm resistor in
signal generator #2 as it's load and supplies 200
milliamp, thus heating up the load resistor.

Signal generator #2 "sees" the 50 ohm resistor in
signal generator #1 as it's load and supplies 200
milliamp, thus heating up the load resistor.

The net voltage is measured as 10 V RMS at 4 MHz.
The net current is measured as 0.

How much energy is being transferred between the
circuits?

Install a one wavelength 50 ohm lossless transmission
line between the two signal generators. Nothing changes
but the standing waves become very visible and measurable.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
When does P(x,t) not equal V(x,t) * I(x,t)?

Any time the angle between V(x,t) and I(x,t) is
not 0 or 180 degrees. The correct equation is:

P(x,t) = V(x,t) * I(x,t) * cos(A)

If you write the above equation as:

P(x,t) = V(x,t) * I(x,t)

then you have implied the *dot product* of those
terms. The *cross product* will give you the wrong
answer. The dot product and cross product are both
ways of multiplying so to be technically correct,
you must specify which method of multiplying that
you are talking about.

When is my bank account zero? When I have drawn out
all the money I deposited. Power is a scalar like
money. If you put in 10 watts and take out 10 watts,
the balance is zero.

If you try to put 10 watts into a load and the load
rejects it, that energy flows in the opposite direction.

P(x,t) = V*I*cos(A) = Pfor - Pref

If Pfor = 10 watts and Pref = 10 watts then
P(x,t), i.e. the *NET POWER* equals zero.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Yuri Blanarovich wrote:
"Dave" wrote in message
news:cwPbj.1073$ML6.117@trndny04...

you can do it when it makes physical sense. it does not make sense in
standing waves for all the obvious reasons that i have pointed out. it
does make sense in the individual traveling waves. just accept what your
little swr meter tells you, it shows the forward power and reflected
power, that is all you need and the only powers that make sense.


Little SWR meter shows forward AND reflected power in one direction, and
reflected power only in reverse direction. Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart to
calculate SWR, when there are no standing waves and no power in them?
Laying waves or sitting waves???

Seems to me that the PROBLEM is that some consider standing wave to be some
imaginary, stopped, frozen wave, no good, while some of us consider standing
wave to be the result of superposition of forward and reverse waves, that
can be (their components) measured, current heats when flowing through
resistance, voltage "burns" when poor dielectric.
Like there is standing wave current, but no standing wave, huh????
Or are we forgetting that we are dealing with electromagnetic waves?
Can someone sort out the terminology and definitions?

Yuri, K3BU



Hi, Yuri,
Cecil and Dave aren't taking resistance into account when they
talk about waves. In other words, they're not writing about real
transmission lines, coils, and such. The only lines they care about are
the ones in their minds: the simple ones where the attenuation constants
are always zero, and current and voltage are always either in phase, or
90 degrees out of phase, and there is never any dielectric breakdown, no
matter the voltage. You can only feel sorry for guys like that.
73,
Tom Donaly, KA6RUH

Standing-Wave Current vs Traveling-Wave Current
 

"Tom Donaly" wrote in message
. net...
Yuri Blanarovich wrote:
"Dave" wrote in message
news:cwPbj.1073$ML6.117@trndny04...

you can do it when it makes physical sense. it does not make sense in
standing waves for all the obvious reasons that i have pointed out. it
does make sense in the individual traveling waves. just accept what
your little swr meter tells you, it shows the forward power and
reflected power, that is all you need and the only powers that make
sense.


Little SWR meter shows forward AND reflected power in one direction, and
reflected power only in reverse direction. Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart
to calculate SWR, when there are no standing waves and no power in them?
Laying waves or sitting waves???

Seems to me that the PROBLEM is that some consider standing wave to be
some imaginary, stopped, frozen wave, no good, while some of us consider
standing wave to be the result of superposition of forward and reverse
waves, that can be (their components) measured, current heats when
flowing through resistance, voltage "burns" when poor dielectric.
Like there is standing wave current, but no standing wave, huh????
Or are we forgetting that we are dealing with electromagnetic waves?
Can someone sort out the terminology and definitions?

Yuri, K3BU

Hi, Yuri,
Cecil and Dave aren't taking resistance into account when they
talk about waves. In other words, they're not writing about real
transmission lines, coils, and such. The only lines they care about are
the ones in their minds: the simple ones where the attenuation constants
are always zero, and current and voltage are always either in phase, or
90 degrees out of phase, and there is never any dielectric breakdown, no
matter the voltage. You can only feel sorry for guys like that.
73,
Tom Donaly, KA6RUH

using any decent coax of a reasonable length and typical amateur power
levels the assumptions we have stated are very close to the actual results.
if you want to examine lossy lines in detail then go ahead, the formulas get
much messier and without proper formula rendering on a newsgroup they are
almost impossible to discuss... and for the concepts that have been proposed
the ideal lossless line case is perfectly acceptable.

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
On Dec 24, 11:18 am, "Dave" wrote:
"Keith Dysart" wrote in message

...

Can you kindly articulate the rules you use to know
when it is appropriate to use P = V * I?
it is extremely simple. use traveling waves then V*I works everywhere all
the time. use standing waves and it fails. period, end of story.

What happens on a line that is terminated in a real
impedance that is not equal to Z0?

There are aspects of both travelling waves and
standing waves present on the line.

Is it appropriate to use P = V * I?

...Keith

And from an earlier post, Keith wrote

"Are you really saying that if I measure the instantaneous
voltage and the instantaneous current then I can NOT multiply
them together to obtain the instantaneous power?

It certainly works some of the time.

If I can not do it all the time, when can I do it?"

You give a good example Keith. It would be correct for measurement at
the load and at every point 1/2 wavelength back to the source from the
load, because the standing wave has the same measurements at these
points. At the 1/4 wavelength point back from the load and every
successive 1/2 wave point back to the source, the equation would also be
correct as demonstrated in Roy's example earlier today.

Excepting for these points, we would also be measuring a reactive
component that could be described as the charging and discharging of the
capacity or inductive component of the transmission line. (Imagine that
we are measuring the mismatched load through a 1/8 wave length long
transmission line, using an Autek RX VECTOR ANALYST instrument) The
inclusion of this reactive component would invalidate the power reading
if we were assuming that the measured power was all going to the load.

I would visualize the situation by saying that at the points mentioned,
the peaks of the traveling waves match as they pass each other going in
opposite directions each cycle. At all other points, the matching is
peak of one plus part of the second, so that the resulting measurement
can always be described as containing a quadrature (or reactive) component.

73, Roger, W7WKB

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
I am having great difficulty matching the words you
wrote with the request for an unambiguous definition
of "standing wave power".

Are you saying the concept is meaningless?
Or do you think you provided a definition?

"Standing wave power" is an oxymoron. There is simply
zero power in standing waves. The dot product of the
net voltage and net current in an ideal standing wave
is always ZERO.

Power (watts) is the measure of energy (joules) passing
a measuring point in one second. One can measure the
forward power. One can measure the reflected power. One
cannot measure any standing wave power because it is
always equal to (Pfor - Pref) which for ideal standing
waves is *always* zero.

If the net energy flow is zero, as it is in ideal standing
waves, the power is zero, by definition, because zero net
joules are flowing. And, sure enough, the standing wave
voltages phasors are *always* 90 degrees away from the
standing wave current phasors and they are not moving left
or right. They are rotating around a fixed spacial point
on the wire.

Standing waves are a very sophisticated illusion.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
And if I had meant *NET* I would have written "net".

Since you are talking about *NET* voltage, *NET*
current, *NET* energy, and *NET* power, don't you
think it would be wise to use the word *NET* (unless
your motive is to obscure)?

Since Pfor = Pref, then Pfor - Pref = 0

Isn't that superposition of power? Something that
most agree is not a legal operation.

No, that is simply an accepted engineering convention
that has been around since long before you and I
were born.

PLoad = (+Pfor) - (+Pref)

The negative sign doesn't mean negative power. It is
simply a directional convention for the Poynting vector
that indicates the direction of energy flow.

A negative sign is often used to denote direction (or
a 180 degree shift).

Dollars going into your bank account and coming out of
your bank account are all the same scalar dollars. The
direction in which they are flowing is denoted by a
plus or minus sign.
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Keith Dysart wrote:
On Dec 24, 11:50 am, "Yuri Blanarovich" wrote:
Why is the Bird wattmeter
calibrated in Watts, measuring power (forward and reverse) and has chart to
calculate SWR, when there are no standing waves and no power in them?

Why indeed? The decision of Bird Electronic to build
an instrument that measured actual line voltage and
current and then compute forward or reverse voltage
but display the result in watts has lead to enormous
confusion about the nature of forward and reverse
waves.

If only they had decided to display forward or
reverse volts, life would be much better. People
would not have internalized "forward and reverse
power" to such a degree.

On the other hand, it would have then required
more arithmetic to compute actual power.

But they did it, and it can not be undone.

Do you have an unambiguous definition of "standing
wave power" that can be used?

...Keith

Hi Keith,
When you take the real part of P = VI*, where
I* is the complex conjugate of the current, you're computing
the power in the transmission line. However, the imaginary
part of VI* doesn't disappear, and you should be aware of
its existence if you're going to put a lot of energy into
said line (unless it's a perfect Cecil//Dave line with no
attenuation etc). Yuri is probably arguing from experience
with real lines. Cecil/Dave are arguing from an idealized,
but flawed understanding of the subject. All of them should
go back to school and study the whole elephant, so they won't
keep making the same mistakes the three blind men made.
73,
Tom Donaly, KA6RUH

Standing-Wave Current vs Traveling-Wave Current
 

Dave wrote:
... today there are better things to do, like scrape ice

Dave, you really should get a self-defrosting refrigerator
so you won't have to scrape ice ever again. :-)
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Cecil Moore wrote:
Gene Fuller wrote:
This photonic limitation is something that exists only in your head.

Good Grief, Gene, I don't have time to teach you
quantum electrodynamics. Go read a book that tells
you about the nature of photons. It is also the
cornerstone of relativity.

Cecil, you couldn't teach anyone quantum electrodynamics if
they put a gun to your head. Quit pretending.
73,
Tom Donaly, KA6RUH

Standing-Wave Current vs Traveling-Wave Current
 

Dave wrote:
"Keith Dysart" wrote:
Is it appropriate to use P = V * I?

it is always appropriate to use P=V*I on the forward and reflected traveling
waves. it is never appropriate to use it on the standing wave voltage and
current. period... plonk.

Arguments like this are usually semantic. Is it possible
that Keith is talking about phasors and you are talking
about scalars?
--
73, Cecil http://www.w5dxp.com

Standing-Wave Current vs Traveling-Wave Current
 

Tom Donaly wrote:
Cecil and Dave aren't taking resistance into account when they
talk about waves. You can only feel sorry for guys like that.

Do you also feel sorry for Slater, Ramo, Whinnery, Johnson,
Chipman, Kraus, and Balanis who all wrote about systems
without taking resistance into account?
--
73, Cecil http://www.w5dxp.com