W5DXP wrote:

wrote:
It is instantaneous voltages which make standing waves.

That's a no-brainer.

It is instantaneous signals which cause distortion in diode
demodulators.

Please define "instantaneous" for us. I suspect it cannot be what
happens in a dt=0 time slot.

With a time varying voltage, for each time t there is a particular
value of voltage. This voltage can be called the instantaneous voltage
to make it clear that it is not the average or RMS or peak or any
of the other voltages which may be of interest with regards to the
signal. Hence the notation v(t) representing the voltage at any
time t.

It is instantaneous voltages and currents which
are added and subtracted in Bird wattmeters.

But the result is rectified and the maximum value is stored on
a capacitor. By definition, a capacitor cannot accept an instantaneous
value of voltage. If it could, it would be called an inductor. :-)

None the less, the original additions and subtractions of voltages
and currents must be done with the instantaneous values for the
proper results to be obtained.

But I notice an instantaneous willingness to reject the value of
instantaneous power.

Please prove that the human brain is capable of instantaneous willingness. :-)

If you will accept proof by example, then simply re-read some of your
posts.

But to reject instantaneous power in a consistent manner, you need to
explain why you do not also reject instantaneous velocity, acceleration,
current, flow or any of the many other interesting things which are a
derivative with respect to time.

Some things logically have an instantaneous value, e.g. voltage. Other
instantaneous values do not seem to be related to reality. Let me use
your mind-f__king techniques on you. So you are saying that all instantaneous
values appearing in any math model anywhere have an associated existence
in reality.

Absolutely not. But I have asked that if you wish to contend that
instantaneous power is of no use while instantaneous current is, that
some rationale be provided. The previous arguments were that it made
no sense because when dt was 0, there was no power. This seemed a weak
argument since a similar argument could be made for the other
instantaneous
value which do seem to be accepted.

Assertion A:
"In a shorted ideal transmission line which has reached steady state,
no energy can cross a voltage or current minimum because
p(t) = v(t) * i(t) and at a voltage or current minimum, the voltage
or current is always zero, so the power is always zero, so there is
no energy flow across a voltage or current minimum."

Assertion B: Since the universe is about 15 billion years older than
our solar system, transmission lines have probably been doing their
thing for billions of years longer than your above statement has existed.

Does this non-sequitor mean that you accept Assertion A and wish to
deflect the discussion?

This conclusion contradicts a commonly held belief:

Yes, and is therefore probably as wrong as can be.

Perhaps, but I observe that you have not yet pointed out the flaw.
Were you to find the flaw in the logic, I would willingly accept
it as false. Merely that the result disagrees with Belief B is
not, by itself, a flaw.

There is absolutely
nothing in physics that prohibits energy from flowing across an area
where power is zero.

I had always understood that power was defined as the rate of energy
flow. If the power is zero, then by definition, there is no flow.
Perhaps your definition of power is different and we should resolve
that before proceeding.

Belief B:
"that in steady-state, energy is flowing along the transmission line
to the end where it is reflected and travels back to the beginning."

Please present a model of how standing waves are possible without forward
waves and reflected waves in a single-source, single feedline, single load
system.

Well, as you agreed near the start of this post (with your statement
"That's a no brainer), it is voltage waves which produce standing waves,
not waves of energy. So Assertion A is not in conflict at all with
standing waves.

Until you do that, you are just, IMHO, blowing smoke.

It is certainly possible that I have made an error in Assertion A. I
observe that you have not yet located that error. But Assertion A
is fairly short and based on the most basic of concepts. It should
be easy to locate and describe the error, if one exists.

Unless you can find an error in the logic of Assertion A, it would
seem reasonable that you re-assess your acceptance of Belief B.

The error in assertion A is that EM light waves cause power nulls
without having any effect on each other whatsoever. And that's exactly
what happens in a transmission line.

Please go through each of the steps of Assertion A and describe the
first one which is in error and why.

Assertion A caused me to reject Belief B and the world did not
collapse:

When you reject the primacy of consciousness in favor of the primacy
of existence, you will understand why your thoughts don't effect reality.
Your thoughts also do not affect much of reality. What happens when you
God-like gurus disagree? - Close to nothing!

This, of course, would not assist with the understanding of the nature
of
'reflected' power.

When you get through with that, consider what happens if time doesn't
really exist and is simply a model of change invented by the human mind.
What happens when you divorce change from the rotation of the earth?

Nor would this.

....Keith

wrote:

Richard Harrison wrote:
When power in each direction is alone measured in each direction,
it`s found there`s no variation in intensity at all.along the line.

So as I try to understand the error in my logic, you are saying that
there can be power, even though the voltage or current is always 0.

Take a look at a light interference pattern. The minimum irradiance
(power) is I1 + I2 - 2*Sqrt(I1*I2). This is called total destructive
interference, i.e. zero power. Yet those two light beams don't even
know each other is there. Their individual power flows are a constant
amplitude and constant direction.

Exactly the same thing holds true for forward and reflected waves. The
"zero power" points are simply the total destructive interference points.
The forward wave is unaffected by the reflected wave and vice versa.
A physical impedance discontinuity is required to cause interaction
between the forward waves and reflected waves. There is no physical
impedance discontinuity at an SWR voltage node in a constant Z0 feedline.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

wrote in message ...
...
But I have asked that if you wish to contend that
instantaneous power is of no use while instantaneous current is, that
some rationale be provided. The previous arguments were that it made
no sense because when dt was 0, there was no power.
....

(Agreeing with Keith...) Of course there MUST be instantaneous power,
because if there is not, then one cannot find energy by taking the
integral of power over time. The instantaneous value may be zero, or
positive, or negative, of course. Or perhaps another way to look at
it is that if energy, which itself is a function of time, is
differentiable, then power must take on instantaneous values.

Cheers,
Tom

Tom Bruhns wrote:
(Agreeing with Keith...) Of course there MUST be instantaneous power,
because if there is not, then one cannot find energy by taking the
integral of power over time. The instantaneous value may be zero, or
positive, or negative, of course. Or perhaps another way to look at
it is that if energy, which itself is a function of time, is
differentiable, then power must take on instantaneous values.

I don't think there is any argument over whether it exists in the math
model or not. My argument is that the concept lacks a lot of usefulness.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

W5DXP wrote in message ...
Tom Bruhns wrote:
(Agreeing with Keith...) Of course there MUST be instantaneous power,
because if there is not, then one cannot find energy by taking the
integral of power over time. The instantaneous value may be zero, or
positive, or negative, of course. Or perhaps another way to look at
it is that if energy, which itself is a function of time, is
differentiable, then power must take on instantaneous values.

I don't think there is any argument over whether it exists in the math
model or not. My argument is that the concept lacks a lot of usefulness.

Ah, I see. Well, consider this: the concept IS useful to me. That's
not an arguable point, as I am the only one who can evaluate it. If
it isn't to you, you don't have to use it. I'll not argue with that.

Cheers,
Tom

wrote:
Are you saying that there can be power when the voltage or current
is always 0? And that this is the error in the sequence of steps
which makes Assertion A false?

There can and does exist component energy when the NET power is zero.
You will understand this when you understand complete destructive
interference in light waves represented by the equation

I1 + I2 -2*Sqrt(I1*I2) equation 9.16, page 388, in the 4th edition
of _Optics_, by Hecht.

Two waves are flowing with unchanging energies and producing an absolutely
black ring, i.e. zero irradiance equals zero power.

Consider again, Assertion A, in more detail this time:

It won't do a bit of good to rehash this until you understand complete
destructive interference. The two interfering waves flow unabated.
You are being fooled by superposition of two waves whose component
energies are completely independent of each other.

All the steps in Assertion A seem correct to me.
Can you help me find the false step which makes Assertion A false?

Yes, I already did that more than once. You will not understand until
you understand how two light beams can cause zero power without even
knowing the other wave is there. There is absolutely no change in
the energy levels in the individual waves during complete destructive
interference.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Actually, all you've got to do to understand this is to realize that
energy is the time integral of power. (Remember that "useless" quantity
of power as a time function?) When you integrate power to get energy,
you get a constant. That constant is the energy present when power = 0,
and it has to be evaluated by knowing something other than just the
power. In a transmission line, that energy is stored in the electric
and/or magnetic fields during the times energy isn't moving (i.e., when
p(t) = 0). Really, math is cool.

Roy Lewallen, W7EL

W5DXP wrote:
wrote:

Are you saying that there can be power when the voltage or current
is always 0? And that this is the error in the sequence of steps
which makes Assertion A false?


There can and does exist component energy when the NET power is zero.
You will understand this when you understand complete destructive
interference in light waves represented by the equation
. . .

W5DXP wrote:
wrote:
All the steps in Assertion A seem correct to me.
Can you help me find the false step which makes Assertion A false?

Yes, I already did that more than once. You will not understand until
you understand how two light beams can cause zero power without even
knowing the other wave is there. There is absolutely no change in
the energy levels in the individual waves during complete destructive
interference.

I conclude from this response that you are unable to detect any
flaws in the logic of steps 1 to 8. Oh well.

....Keith

Keith wrote:
"I conclude from this response that you are unable to detect any flaws
in the logic of steps 1 to 8."

They are contradictory. That`s a fatal flaw.

Volts and amps on a transmission line are manifestations of E&H fields
guided by the line. These fields are generating the volts and amps seen
on the line as the wave travels along its length.

Even a hard short or an open circuit doesn`t annihilate the signal on a
line. The short or open only produces a reflection.

At the open or short, amps or volts are forced to zero. That event
forces the energy which had resided in the H-field or E-field to
temporarily be accomodated in the field which is its partner in
transporting energy. This doubles volts right at the open or doubles
amps right at the short.. This single field is only temporary because in
a very short travel distance, energy is again balanced between the two
fields.

Note that the open or short does not stop energy flow. It just turns it
around as a reflection. This happens at an actual discontinuity. At an
SWR interference point, nothing upsets energy flow at all in a uniform
line. SWR nulls are just demonstrations of commingled waves passing
through each other without serious consequence. For the nth time, were
you to separate the going and coming signals, you would find no
variation in average signal power in either direction along the line at
any point, including the SWR nulls..

Best regards, Richard Harrison, KB5WZI

wrote:
6) From 2) and 5), the power (rate of energy flowing) at quarter
wave points will be 0

The NET power will be zero. The forward power flow vector is NOT
zero and the reflected power flow vector is NOT zero. The NET power
of zero is complete destructive interference in action. It happens
all the time to two light beams whose energies are not affected by
the interference.

7) From 6), the energy crossing quarter wave points is 0

The NET energy crossing quarter wave points is 0. The two component
energies crossing quarter wave points are not 0. They are the
constant forward power flow vector and the constant reflected
power flow vector as explained in Ramo & Whinnery. Their ratio
is the power reflection coefficient. Equation 3, page 350, _Fields_
and_Waves_in_Communications_Electronics_, Ramo, Whinnery, & Van Duzer.

(Pz-)/(Pz+)=|rho|^2

All the steps in Assertion A seem correct to me.

Yes, that is your problem. They are not correct for the two
component energies.

Can you help me find the false step which makes Assertion A false?

Here it is again, for the Nth time. There are two waves flowing in opposite
directions, each possessing its own constant energy, each flowing unopposed
end to end in the transmission line.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----