Bart Rowlett wrote:

Jim Kelley wrote:


I think the source of part of the confusion here is that some people
apparently interpret the 'forward power' reading on their meter to
mean the power into their transmission line.


It's not.

I sincerely hope you don't think I was implying that YOU were confused
by such a thing, Bart. ;-)

73, Jim AC6XG

Robert Lay W9DMK wrote:

On Thu, 02 Dec 2004 09:47:54 -0600, Cecil Moore
wrote:


Consider an earlier example made up of lossless lines:

100W XMTR---50 ohm---+---one second long 291.5 ohm---50 ohm load

The voltage reflection coefficient at the load is 0.707. The power
reflection at the load is 0.5, i.e. half the power is reflected.

After steady-state has been reached, the XMTR has output 300 more
joules than the load has accepted. A smaller real-world experiment
will easily verify that it is a fact that all energy sourced that
has not reached the load must necessarily be confined to circulating
energy or losses in the transmission line.

Question: In the above example, where are those 300 joules of energy
located and what is happening to them?

We know that 300 joules is wave energy and RF waves always move
at the speed of light, i.e. they cannot stand still. So please
determine how much energy is moving and in which of only two
possible directions.


Dear Cecil,

Here's my guesses -
The 300 joules of energy decays at a particular rate - i.e., in a
certain interval of time, 63.2% of it will have been converted to and
become dissipated as heat. During that same time interval,Ti, there
will be an equal amount of energy introduced to replenish the amount
lost. In other words, there will be a continuum of energy transferring
into the transmission line to exactly make up for that lost in any
given period of time.

Yep, the point is that the *net* energy in the transmission line will
remain at 300 joules during steady-state. The transmission line is one
second long and the source is sourcing 100 joules/sec. That means that
200 joules of "extra" energy is being stored in the transmission line.
The forward power is 200 joules/sec, 100 joules/sec higher than the
source power. The reflected power is 100 joules/sec. There is exactly
where the 200 joules of energy are stored - half in the forward wave
and half in the reflected wave whose superposition results in the
standing wave.

Eventually, someone will disconnect the source generator at time T2.
However, the load will continue to receive energy for a length of
time, Ti, at which point roughly 63.2% of 300 joules of energy will
have been dissipated in the load. If we wait long enough, 99.9% of the
300 joules will have been dissipated, but it will take forever for the
last little bit to disappear.

It kind of makes you think in terms of "life everlasting", doesn't it?

It probably gets close enough to zero for government work.

Did you see my question on another posting? If one hooks up a 1/4WL
stub to a signal generator, what is the dB loss in the stub? It might
have something to do with your original posting.
--
73, Cecil http://www.qsl.net/w5dxp

Instead of messing about calculating the additional loss due to SWR and then
adding it to the matched loss, I've just had a wonderful idea.

Why not calculate the actual line loss directly and solve all your problems
at one fell swoop.
---
Reg.

On Fri, 3 Dec 2004 19:00:14 +0000 (UTC), "Reg Edwards"
wrote:

Glass half empty theory:
Instead of messing about calculating the additional loss due to SWR and then
adding it to the matched loss, I've just had a wonderful idea.
Glass half full theory:
Why not calculate the actual line loss directly and solve all your problems
at one fell swoop.

Jim Kelley wrote:
It's accurate to say that power is something which itself doesn't
propagate in any fashion, at any wavelength.

I know that's the physicists view, but some engineering views
are slightly different because of a differing definition of
"power". Let's say we have a one second EM pulse containing one
joule of energy traveling along a transmission line with three
joules/sec measuring points. For one second periods in succession,
we will measure one watt at the measuring points. In each case,
the one watt is the same one watt, displaced in time, being
transferred to the load. That one watt appears at the first
measuring point, then at the second measuring point, then at
the third measuring point, and finally heats up the load. It
certainly appears to be associated with the pulse moving from
the source to the load.

That's the way a lot of engineers deal with power, including
all the power company engineers that I know, and that's the way
the IEEE Dictionary deals with power.

Your "tree falling in the forest making no sound" concept
may not be the best approach for the real world.
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:
Instead of messing about calculating the additional loss due to SWR and then
adding it to the matched loss, I've just had a wonderful idea.

Why not calculate the actual line loss directly and solve all your problems
at one fell swoop.

What is the formula for the total dB loss?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil,

I am glad to see you have come around to the correct view that the
"extra" energy is stored in a standing wave.

Now if only we could convince you that mathematically, physically, and
in "reality" there is not the slightest bit of difference between
individual wave components and their superposition result then there
would be real progress.

Oh, by the way, is there some reason you highlight *net* energy? Is
there any other kind? Energy is a scalar, so numerically it can be only
positive or negative, with no phase angle or other vector properties.
Unless part of the energy in your transmission line is negative the net
energy would be the same as the gross energy. (Not including sales tax
and shipping charges.)

I am well acquainted with the concept of negative energy when describing
atomic structure, for example, but I have not heard of negative energy
in transmission lines. Can you explain the distinction you appear to make?

73,
Gene
W4SZ



Cecil Moore wrote:


Yep, the point is that the *net* energy in the transmission line will
remain at 300 joules during steady-state. The transmission line is one
second long and the source is sourcing 100 joules/sec. That means that
200 joules of "extra" energy is being stored in the transmission line.
The forward power is 200 joules/sec, 100 joules/sec higher than the
source power. The reflected power is 100 joules/sec. There is exactly
where the 200 joules of energy are stored - half in the forward wave
and half in the reflected wave whose superposition results in the
standing wave.

Jim Kelley wrote:

It's accurate to say that power is something which itself doesn't
propagate in any fashion, at any wavelength.

Will someone please try to explain to Cecil that engineering is an
application of fundamental physical properties, and that the disciplines
of physics and engineering are not at odds with one another?

thanks,

AC6XG

Gene Fuller wrote:
Cecil,

I am glad to see you have come around to the correct view that the
"extra" energy is stored in a standing wave.

Never have I ever budged from the view that the "extra" energy
is stored in the standing wave components, i.e. in the forward
wave and the reflected wave. What I object to is your merging
of the forward wave and reflected wave as if they were some sort
of homoginized energy. You can prove your beliefs by providing
an example of a standing wave not composed of the superposition
of a forward wave and a reflected wave. I have offered that challenge
before and nobody has stepped up to the plate. Perhaps, you will
be the first. I await with abated breath.

Now if only we could convince you that mathematically, physically, and
in "reality" there is not the slightest bit of difference between
individual wave components and their superposition result then there
would be real progress.

What you are arguing is that there is no difference between a husband
and a wife. They are just two components of a family who merge into
a single entity so either or both may be male or female. Sorry, Gene,
that's not my view of the world. IMHO, it is the *components* that are
important. IMO, you liberals are trying to destroy science and society
all at the same time.

Oh, by the way, is there some reason you highlight *net* energy? Is
there any other kind?

Of course, there is another kind of energy besides net energy. Is there
any difference between a wife and a husband? They are both parents, so
you liberals would argue that there is no difference between them. I
simply don't agree with you.

I am well acquainted with the concept of negative energy when describing
atomic structure, for example, but I have not heard of negative energy
in transmission lines. Can you explain the distinction you appear to make?

It's a convention, Gene. I'm surprised you have never heard of it. ExH
traveling in one direction is positive. ExH traveling in the opposite
direction is negative. The Z0 of a transmission line forces the E-field
to H-field ratio to be Z0, i.e. forces the forward voltage to forward
current ratio to be Z0 - and the same for reflected current. One of my
references shows a Poynting Vector for the forward power and a separate
Poynting Vector for the reflected power, i.e. husbands and wives are not
interchangable!
--
73, Cecil http://www.qsl.net/w5dxp

Jim Kelley wrote:
Will someone please try to explain to Cecil that engineering is an
application of fundamental physical properties, and that the disciplines
of physics and engineering are not at odds with one another?

On the contrary, many of the pure-physics-oriented posters to
this newsgroup have alleged that the IEEE Definitions are Bull$hit
and are to be ignored. Check Google if you don't believe it.

The IEEE Definitions are what engineers abide by. Of course,
the disciplines of physics and engineering are certainly at
odds with one another. For instance, engineers have an altogether
different view of what "work" is, compared to the physicists.
Physicists say no work is done if the starting line and the finish
line are the same for a marathon. Engineers will say: "Then why am
I so friggin' tired?"

The POWER engineers at a POWER generating station operated by
a POWER company simply don't buy into your pure physics BS.
They assume that POWER (joules/sec) leaving a generating station
will, after subtracting losses, make money for the company.
--
73, Cecil http://www.qsl.net/w5dxp