On Jun 24, 8:59*pm, Keith Dysart wrote:
But then what explains the reflection at the generator that presents
Z0 to the line?

Your error is in assuming it is a reflection. It is NOT a reflection
which, by definition, involves one wave. It is a redistribution of
energy due to superposition which, by definition, involves two or more
waves. In a system designed to eliminate reflections at the source,
ALL of the redistribution of reflected energy back toward the load is
due to superposition accompanied by interference. From the FSU web
site:

"... when two waves of equal amplitude and wavelength that are 180-
degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the ... energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ..."

Nothing said about *reflection* (involving a single wave). It is all
about the meeting (superposition) of two waves which can cause the
redistribution of energy. It may look somewhat like a reflection but
it is technically NOT a reflection.
--
73, Cecil, w5dxp.com

On Jun 25, 2:13*am, lu6etj wrote:
In a TL, instead, total destructive interference in one point would
mean energy stop flowing from that point forwards (is it OK say
"forwards"?) and reverse its flow direction doubling his value, is it
OK?.

In our ham transmission line systems, the goal is to accomplish total
destructive interference toward the source, i.e. zero reflected energy
incident upon the source. So let's talk about destructive interference
toward the source and constructive interference toward the load.

You name it "redistribution" too, not reflection.

By definition, reflection is something that happens to a single wave.
By definition, superposition involves two or more waves. The
redistribution that I am talking about can include both reflection and
superposition if both are present. Depending upon the system
configuration, both may be present, both may be absent, or one exist
without the other.

Well, my
question was how we can set (devise) an experiment to get such
behaviour in a TL?

I've presented it before and it is a simple Z0-match involving a 1/4WL
matching section.

50w-----50 ohm------+------1/4WL 300 ohm------1800 ohm load

On the source side, rho at '+' is 0.7143

Using a TDR, we can verify that there is indeed a reflection from the
50/300 ohm impedance discontinuity. What happens to that reflection
during steady-state?

What happens to Vfor1(rho) = 50v(0.7143) = 35.7v?

What happens to Pfor1(rho^2) = 50w(0.51) = 25.5w?
--
73, Cecil, w5dxp.com

"Cecil Moore" wrote
...
On Jun 24, 8:59 pm, Keith Dysart wrote:
But then what explains the reflection at the generator that presents
Z0 to the line?

Your error is in assuming it is a reflection. It is NOT a reflection
which, by definition, involves one wave. It is a redistribution of
energy due to superposition which, by definition, involves two or more
waves. In a system designed to eliminate reflections at the source,
ALL of the redistribution of reflected energy back toward the load is
due to superposition accompanied by interference. From the FSU web
site:

"... when two waves of equal amplitude and wavelength that are 180-
degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the ... energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ..."

Nothing said about *reflection* (involving a single wave). It is all
about the meeting (superposition) of two waves which can cause the
redistribution of energy. It may look somewhat like a reflection but
it is technically NOT a reflection.

In the Hertz dipole the reflection take place but in the loop antenna "two
waves of equal amplitude and wavelength that are 180-degrees ... out of
phase with each other meet,"

But the both cases are the same. At the meeting the energy is radiated and
the electrons emitted because in the meeting place the voltage is doubled.

The electronic circuit theory do not use EM.
S*.

On 25 jun, 08:30, K1TTT wrote:
On Jun 25, 7:46*am, lu6etj wrote:





On 24 jun, 17:54, K1TTT wrote:

On Jun 24, 3:25*pm, Cecil Moore wrote:

On Jun 24, 9:20*am, lu6etj wrote:

Oh, I'm so sorry Cecil, I should have written "However I can not
visualize a simple PHYSICAL mechanism/example to generate
such system in a TL". Anyway, your additional info it is very useful to
me. Thanks.

The physical mechanism is the Z01==Z02 impedance discontinuity with
its associated reflection coefficient, rho. We can see that reflection
on a TDR so it is indeed a PHYSICAL mechanism.
--
73, Cecil, w5dxp.com

don't forget the OTHER physical mechanism that is necessary,
superposition... the ability to add voltages, currents, and fields in
linear circuits and media.

I mentioned same comment in another post. We use superposition
principle in two different contexts. Superposition theorem in circuit
theory, and wave superposition. Wave (traveling) superposition deals
with f(t,x,y,z) and usually with puntual magnitudes, E, H, D, B, etc)
while circuit theory deals with a subset f(t) phenomena and with
integrated magnitudes (V, I). Sometimes that becomes a confused
issue

Miguel

NO, superposition is always the same. *it is the linear addition of
currents or fields in a linear media. *it works the same for circuits
as for em waves.

the big problem are the people who confuse the formulas for adding
powers with adding fields or currents/voltages and forget the phase
terms.

the other big problem is keith who seems to want to separate his waves
into separate time and space variables and leaves out the requirement
that wave functions must be dependent on both space AND time.
basically any solution to the wave equations derived from maxwell's
laws must be of the form f(t-x/v). *this leads him to the erroneous
conclusions he gets from trying to compare his batteries to wave
propagation. *this is the same problem people have with standing
waves, they have separate dependence on t and x, so they can't travel
and can't transport energy.- Ocultar texto de la cita -

- Mostrar texto de la cita -

NO, superposition is always the same

I did not say that things were fundamentally different, I said
"context" it is different, as "substraction" in mathematics, you can
not subtract a natural number bigger from a smaller one in natural
field, but you can do it in integer field, we have to apply (comply?)
contextual rules with such operations. Otherwise I agree with what you
say. 73

On 25 jun, 10:00, Cecil Moore wrote:
On Jun 25, 2:13*am, lu6etj wrote:

In a TL, instead, total destructive interference in one point would
mean energy stop flowing from that point forwards (is it OK say
"forwards"?) and reverse its flow direction doubling his value, is it
OK?.

In our ham transmission line systems, the goal is to accomplish total
destructive interference toward the source, i.e. zero reflected energy
incident upon the source. So let's talk about destructive interference
toward the source and constructive interference toward the load.

You name it "redistribution" too, not reflection.

By definition, reflection is something that happens to a single wave.
By definition, superposition involves two or more waves. The
redistribution that I am talking about can include both reflection and
superposition if both are present. Depending upon the system
configuration, both may be present, both may be absent, or one exist
without the other.

Well, my
question was how we can set (devise) an experiment to get such
behaviour in a TL?

I've presented it before and it is a simple Z0-match involving a 1/4WL
matching section.

50w-----50 ohm------+------1/4WL 300 ohm------1800 ohm load

On the source side, rho at '+' is 0.7143

Using a TDR, we can verify that there is indeed a reflection from the
50/300 ohm impedance discontinuity. What happens to that reflection
during steady-state?

What happens to Vfor1(rho) = 50v(0.7143) = 35.7v?

What happens to Pfor1(rho^2) = 50w(0.51) = 25.5w?
--
73, Cecil, w5dxp.com

Sorry. Cecil, I do not catch you (final numeric example), would you
mind give to me a more explanatory/explicit answer? (the rest OK). 73
Miguel

On Jun 25, 8:24*am, Cecil Moore wrote:
On Jun 24, 8:58*pm, Keith Dysart wrote:

Still does not explain why you choose only the positive root.

Of course it does. In the power density equation, choosing the
negative root would lead to a violation of the conservation of energy
principle. When one of the roots is obviously impossible in reality, a
rational person chooses the other root.

You might study why the real power folk prefer three phase to single.
It all has to do with instantaneous power.

I am a "real power folk", Keith. My first EE degree was in power
generation and transmission. Three-phase puts less stress on the
system by eliminating the hills and valleys in the energy flow common
with traveling waves.

That's the time domain. Variation in the instantaneous energy flow.

Not quite
'as useless as tits on a boar hog, or as Hecht said, putting it
mildly: "of limited utility"'.

....Keith

On Jun 25, 9:00*am, Cecil Moore wrote:
On Jun 25, 2:13*am, lu6etj wrote:

In a TL, instead, total destructive interference in one point would
mean energy stop flowing from that point forwards (is it OK say
"forwards"?) and reverse its flow direction doubling his value, is it
OK?.

In our ham transmission line systems, the goal is to accomplish total
destructive interference toward the source, i.e. zero reflected energy
incident upon the source. So let's talk about destructive interference
toward the source and constructive interference toward the load.

You name it "redistribution" too, not reflection.

By definition, reflection is something that happens to a single wave.
By definition, superposition involves two or more waves. The
redistribution that I am talking about can include both reflection and
superposition if both are present. Depending upon the system
configuration, both may be present, both may be absent, or one exist
without the other.

Well, my
question was how we can set (devise) an experiment to get such
behaviour in a TL?

I've presented it before and it is a simple Z0-match involving a 1/4WL
matching section.

50w-----50 ohm------+------1/4WL 300 ohm------1800 ohm load

On the source side, rho at '+' is 0.7143

Using a TDR, we can verify that there is indeed a reflection from the
50/300 ohm impedance discontinuity. What happens to that reflection
during steady-state?

What happens to Vfor1(rho) = 50v(0.7143) = 35.7v?

Using superposition, when you add Vrev2(tau) to Vfor1(rho) you get
zero.
With zero voltage comes 0 energy transfer.

For further learning, do not just examine steady state, but also
examine
how it gets to steady state. Using a lattice diagram, examine what
happens as the first reflection and then each re-reflection arrives at
'+'. Determine how Vrev2(tau) slowly builds to equal Vrev1 and cancels
it, using the simple addition of superposition. While this process is
occurring, there is a Vrev1 which decreases after each round trip in
the second line section.

This is all done with simple addition. No need for products and square
roots.

For further marks, decide whether you should think of Vrev2 as an
infinite sum of reverse waves or is it okay to think of it as one sum
that slowly accumulates.
Which is it really?

Same question for Vfor2.

What happens to Pfor1(rho^2) = 50w(0.51) = 25.5w?

Once you have computed total Vrev1 using simple superposition, it is
easy to compute that the "reverse power", Prev1, is 0.

Do you really need rho^2 to understand what goes on in a transmission
line?

....Keith

On Jun 25, 7:30*am, K1TTT wrote:
On Jun 25, 7:46*am, lu6etj wrote:





On 24 jun, 17:54, K1TTT wrote:

On Jun 24, 3:25*pm, Cecil Moore wrote:

On Jun 24, 9:20*am, lu6etj wrote:

Oh, I'm so sorry Cecil, I should have written "However I can not
visualize a simple PHYSICAL mechanism/example to generate
such system in a TL". Anyway, your additional info it is very useful to
me. Thanks.

The physical mechanism is the Z01==Z02 impedance discontinuity with
its associated reflection coefficient, rho. We can see that reflection
on a TDR so it is indeed a PHYSICAL mechanism.
--
73, Cecil, w5dxp.com

don't forget the OTHER physical mechanism that is necessary,
superposition... the ability to add voltages, currents, and fields in
linear circuits and media.

I mentioned same comment in another post. We use superposition
principle in two different contexts. Superposition theorem in circuit
theory, and wave superposition. Wave (traveling) superposition deals
with f(t,x,y,z) and usually with puntual magnitudes, E, H, D, B, etc)
while circuit theory deals with a subset f(t) phenomena and with
integrated magnitudes (V, I). Sometimes that becomes a confused
issue

Miguel

NO, superposition is always the same. *it is the linear addition of
currents or fields in a linear media. *it works the same for circuits
as for em waves.

the big problem are the people who confuse the formulas for adding
powers with adding fields or currents/voltages and forget the phase
terms.

the other big problem is keith who seems to want to separate his waves
into separate time and space variables and leaves out the requirement
that wave functions must be dependent on both space AND time.
basically any solution to the wave equations derived from maxwell's
laws must be of the form f(t-x/v). *this leads him to the erroneous
conclusions he gets from trying to compare his batteries to wave
propagation. *this is the same problem people have with standing
waves, they have separate dependence on t and x, so they can't travel
and can't transport energy.- Hide quoted text -

I see that the stress induced by considering DC waves is causing you
to misinterpret my writings.

May I suggest an alternate exploration for you. Assuming that you
accept TDR and know how to use Reflection Coefficients to compute
voltage and current reflections, then consider what happens
when a rectangular pulse is launched from a matched generator in
to a transmission line. For simple reflection coefficients like
0, 1, and -1 compute the reflected pulse. For both the forward
and reflected direction compute the voltage and current on the line
before the pulse arrives, as it passes and after it has passed.

Compute the energy in the pulse, and how long a distance it
occupies on the transmission line. Compute the power as the
pulse is passing.

Be sure you know what happens to the pulse when it re-enters
the generator. For simplicity, assume a generator constructed
using the Thevenin circuit.

Make sure all the results are in agreement; especially, the
energy delived by the source and the energy dissipated in the
various resistors.

Now make the pulse longer and longer... until it looks like
a step function. And do the computations again.

Determine if the results agree with those I previously
presented for the DC example.

....Keith

PS: Barring errors, they will.

On Jun 26, 12:22*am, Keith Dysart wrote:
On Jun 25, 7:30*am, K1TTT wrote:



On Jun 25, 7:46*am, lu6etj wrote:

On 24 jun, 17:54, K1TTT wrote:

On Jun 24, 3:25*pm, Cecil Moore wrote:

On Jun 24, 9:20*am, lu6etj wrote:

Oh, I'm so sorry Cecil, I should have written "However I can not
visualize a simple PHYSICAL mechanism/example to generate
such system in a TL". Anyway, your additional info it is very useful to
me. Thanks.

The physical mechanism is the Z01==Z02 impedance discontinuity with
its associated reflection coefficient, rho. We can see that reflection
on a TDR so it is indeed a PHYSICAL mechanism.
--
73, Cecil, w5dxp.com

don't forget the OTHER physical mechanism that is necessary,
superposition... the ability to add voltages, currents, and fields in
linear circuits and media.

I mentioned same comment in another post. We use superposition
principle in two different contexts. Superposition theorem in circuit
theory, and wave superposition. Wave (traveling) superposition deals
with f(t,x,y,z) and usually with puntual magnitudes, E, H, D, B, etc)
while circuit theory deals with a subset f(t) phenomena and with
integrated magnitudes (V, I). Sometimes that becomes a confused
issue

Miguel

NO, superposition is always the same. *it is the linear addition of
currents or fields in a linear media. *it works the same for circuits
as for em waves.

the big problem are the people who confuse the formulas for adding
powers with adding fields or currents/voltages and forget the phase
terms.

the other big problem is keith who seems to want to separate his waves
into separate time and space variables and leaves out the requirement
that wave functions must be dependent on both space AND time.
basically any solution to the wave equations derived from maxwell's
laws must be of the form f(t-x/v). *this leads him to the erroneous
conclusions he gets from trying to compare his batteries to wave
propagation. *this is the same problem people have with standing
waves, they have separate dependence on t and x, so they can't travel
and can't transport energy.- Hide quoted text -

I see that the stress induced by considering DC waves is causing you
to misinterpret my writings.

May I suggest an alternate exploration for you. Assuming that you
accept TDR and know how to use Reflection Coefficients to compute
voltage and current reflections, then consider what happens
when a rectangular pulse is launched from a matched generator in
to a transmission line. For simple reflection coefficients like
0, 1, and -1 compute the reflected pulse. For both the forward
and reflected direction compute the voltage and current on the line
before the pulse arrives, as it passes and after it has passed.

Compute the energy in the pulse, and how long a distance it
occupies on the transmission line. Compute the power as the
pulse is passing.

Be sure you know what happens to the pulse when it re-enters
the generator. For simplicity, assume a generator constructed
using the Thevenin circuit.

Make sure all the results are in agreement; especially, the
energy delived by the source and the energy dissipated in the
various resistors.

Now make the pulse longer and longer... until it looks like
a step function. And do the computations again.

Determine if the results agree with those I previously
presented for the DC example.

...Keith

PS: Barring errors, they will.

why would i want to do all that work? there is no way that my answers
will agree with your misconceptions. you'll just come up with an even
uglier generator to try to make it fit.

oh, and by the way, your fancy 2 generator and 2 resistor 'constant
power' source isn't what you think it is. go back to basic circuits
101 and you will find that any linear network like that can be reduced
to either a simple one source one impedance norton or thevenin
equivalent. in your example it is identical to a 50v voltage source
in series with a 50ohm resistor... deriving the norton equivalent is
left for the student.

On Jun 25, 4:00*pm, Keith Dysart wrote:
That's the time domain. Variation in the instantaneous energy flow.

What you seem to be missing is that the *energy content* of power
(total joules) must be conserved but the instantaneous power (joules/
second) does not have to be conserved as you have argued numerous
times in numerous examples. The only question that needs to be
answered is: In a system designed to eliminate reflections and
interference, does all the reflected energy eventually get dissipated
in the source resistor. The answer is yes because there is nowhere
else for it to go. There is no conservation of power principle and
that includes instantaneous power. So it is irrelevant what/where
instantaneous power might do/go during a single cycle.

Now I understand that instantaneous power dictates some physical
design considerations as in waveguides. But since instantaneous power
does not fall under the conservation of energy principle, it is simply
irrelevant to the present discussion. What happens over a complete
cycle is what is relevant. However, in any and every case, it is
energy that is conserved, not power. How many joules are in that dt
sliver of time when the instantaneous power is 100 watts? It's those
joules that must be conserved, not the instantaneous power.

You didn't answer my previous question. If you measure 100 watts of
instantaneous power at 100 places within an inch of each other, does
that mean there is 10000 watts of instantaneous power in that one inch
of wire? That is the only logical conclusion based on your argument
and assertions. Any argument based on the conservation of power is
doomed to fail. Please get real.

Not quite
'as useless as tits on a boar hog, or as Hecht said, putting it
mildly: "of limited utility"'.

One could argue that tits on a boar hog are not completely useless
and, therefore, instantaneous energy is exactly as useless (or exactly
as useful) as tits on a boar hog. (Hint: Without the existence of the
tit gene in the male, female hogs would probably not have tits.)
--
73, Cecil, w5dxp.com