Cecil Moore wrote:

wrote:
Regardless of whether there is an alternative explanation,
you should reject the reflected power model because....
In general, IT DOES NOT WORK.

In general, our feedline losses are low enough that it does
work. In general on HF, we are dealing with near-resistive
Z0's and Z0-matched systems.

There seems to be a bit of a vocabulary problem. The 'general
case' is the one that is more encompassing as in 'general
relativity' when compared to 'special relativity'.

So in your passage above, you are agreeing with my assertion.

In GENERAL, IT DOES NOT WORK.

In the specific case of RF, "our feedline losses are [usually]
low enough that it does work."
In the specific case of HF, "we are [usually] dealing with
near-resistive Z0's and Z0-matched systems."

With which I have no dispute. But that still leaves us with....

In GENERAL, IT DOES NOT WORK.

This strongly suggests a flaw in the model.

As has been aptly demonstrated in another thread, it does
not work for lines with complex Z0.

Actually it does. All one has to do is take the power interference
terms into account.

Exactly my point. So now the net power is no longer the sum of
the forward and reflected power; there is a third term which is
neither the forward nor the reflected power.

In GENERAL, IT DOES NOT WORK.

This, of course, will not prevent you from taking advantage
of it where it does work. But always remember that it ONLY
works in special cases.

With the possible exception of QED, that statement is true of ALL
math models, including yours. Yours only works in the special case
of perfect steady-state conditions

I am unsure what you think my model is. Perhaps you could elaborate?

In any case, my argument is that in GENERAL, the reflected power
model DOES NOT WORK. This is independent of whether I (or anyone)
has an alternative which does work.

....Keith

David Robbins wrote:

i'll agree with that... the ubiquitous 'SWR' meter provides useful
information for real world application, its easy to read, and easy to use.
Just because it may not be reading exactly what the name implies doesn't
reduce its usefulness.

On the one hand, it is still useful for what it does.

On the other hand, poor names have lead many to a mis-understanding of
how it works.

So overall, it has been less useful than if it were not mis-named.

....Keith

pez wrote:

| wrote:
| ...
| As has been aptly demonstrated in another thread, it does
| not work for lines with complex Z0.
| ...

Dear Keith,

Could you tell me please in which thread?

It was a thread started by Roy Lewellan titled "Complex line
Z0: A numerical example" to which I refer.

On the assumption that you have access to and that google will give
the same answer to you that it gives to me, try...

http://groups.google.ca/groups?hl=en...vl2kp2cdlork04

....Keith

On Sun, 21 Sep 2003 15:29:26 -0500, Cecil Moore
wrote:
It is all explained in Chipman's "Transmission Lines". Please take the time
to read it and understand it

:-)

Good example. But let's suppose you've never seen any rectangle that
wasn't square. You've learned that you only need to measure one side
(with a Bird side-meter, undoubtedly) in order to determine the area.
Works fine. Always has. You swear up and down that the area of a
rectangular figure is always the square of one side. Then someone gives
you a rectangle. Worse yet, they claim there's something called a
rectangle, which you've never seen.

It's been really interesting to see how the various participants in this
discussion react to this new concept.

Roy Lewallen, W7EL

Richard Harrison wrote:
Keith wrote:
"Scientists are usually interested in producing models which will allow
them to predict the behaviour of the real world.

True. Models must be adjusted to reality, not the other way around. But,
once the model is verified it becomes useful.

You don`t have to measure the area of a rectangle with a planimeter once
you know that area is the product of the length and width of the
rectangle.

Best regards, Richard Harrison, KB5WZI

Radio913 wrote:

"Scientists" are also human too, and tend to want to disregard or not
even
try to measure data that may contradict their models. This makes them
feel
comfortable that they are "right".

I completely agree.

So can you overcome your "tend[ancy] to want to disregard or
not even try to measure data that may contradict their models."?

I'll think about it after you tell us what you get when you measure the
end of the inductor.

I've been to the lab.

May I suggest that it is now your turn to do so.

Otherwise you are simply adding to the evidence that you are having
difficulty overcoming a "tend[ancy] to want to disregard or not even
try to measure data that may contradict [your] models."

....Keith

Keith wrote:
"Some of the authors you quote are not so convinced of their (waves)
reality."

Symbols merely represent reality but are important to the exchange of
ideas just the same. The effects seen on transmission lines are reliably
explained and predicted by wave action. In one of my physics classes
over a half century ago, the prof asked another student a question about
atoms. The reply was that the student had never been inside an atom.
Neither the prof nor anyone else seemed impressed with the retention of
the student, but the prof agreed that he had never been inside an atom
either, but found atomic theory useful.

Terman is as reliable as anyone I know of, and he says:
"The voltage and current existing on a transmission line as given by
Eqs. (4-6) can be conveniently exprerssed as the sum of the voltages and
currents of two waves, one traveling toward the receiving or load end of
the line, and is called the "incident wave" because it is incident upon
the load. The second wave can be thought of as traveling from the load
toward the generator end of the line; it is termed the "reflected wave",
and is generated at the load by reflection of the incident wave."

Terman has no qualms, it seems, but says "regarded as traveling". Those
aren`t weasel words. Terman is more direct on page one in the opening
sentance:
"Electrical energy that has escaped into free space exists in the form
of electromagnetic waves."

How else could their energy be transferred at the speed of light?

Best regards, Richard Harrison, KB5WZI

Keith wrote:
"---does the reader believe the markings on the scale and think that it
is actually MEASURING the power in a forward and reverse wave?"

The wattmeter markings have been calibrated to indicate watts. One only
must measure a quantity proportional to watts then interpret that
accurately.

A speedometer indicates miles per hour but gets that from electricity
which is proportional to speed. Neither miles nor hours are measured.

Best regards, Richard Harrison, KB5WZI

Cecil,

I don't have a schematic for the Daiwa. So, I don't really know what it was
measuring; but, I think more than likely, the voltage that reached the
meter. If the scale were calibrated in gallons per minute, I might have read
2.5 gallons per minute.

Tam/WB2TT
"Cecil Moore" wrote in message
...
Tarmo Tammaru wrote:
Amen to that. I turned down the power on my transmitter, and measured P
forward and P rev while feeding about 100 feet of unterminated 9913. I
then
REMOVED the coax; i.e. there was nothing connected to the output side of
the
meter. Still measured the same Pf and Pr. (Daiwa meter)

Of course, you were simply getting a same-cycle reflection. The reflected
wave model is consistent. If the open-circuit is at the transmitter
terminal,
all the power is reflected immediately.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Harrison wrote:

Keith wrote:
"---does the reader believe the markings on the scale and think that it
is actually MEASURING the power in a forward and reverse wave?"

One only must measure a quantity proportional to watts then interpret
that accurately.

So true. But the quantities being measured are line volts and line amps
and neither is proportional to incident or reflected watts.

Much happens to the measured voltage and current before the result is
inaccurately interpreted as forward and reverse power.

....Keith

Keith wrote:
"How does Terman first write of the power in these waves?"

I don`t remember chapter and verse anymore. So, I can`t say where Terman
first writes of power in these waves. On page 88 of Terman`s 1955
edition he says:
"At radio frequencies it is nearly always permissible to assume that
omega L R, and omega C G. To the extent that it is true, one can
rewrite Eqs. (4-5) and (4-7) as follows:
Zo = sq rt L/C

This means current is in-phase with voltage in the waves in both
directions.

In-phase volts and amps are real power, not apparent power.

Best regards, Richard Harrison, KB5WZI

Reg,

I was merely agreeing with your comment about reading imaginary SWR on a
nonexistent transmission line. I tried the same thing with the HF
transmitter, which is connected to a Kenwood meter. Same results. In looking
at the Kenwood schematic, it looks like in the absence of any current flow,
it reverts to being a voltmeter, with both diodes getting the same drive.
The thing reminds me of old HP analog voltmeters that always had a dbm
scale. Of course, the dbms were nonsense, unless you were measuring across a
600 Ohm load.

Interesting about you looking at rho max = 1 +SQRT2 10 years before Chipman.
That beats Adler, Fano, and Chu who had it in their 1960 book.

Tam/WB2TT
"Reg Edwards" wrote in message
...
"Tarmo Tammaru" wrote -
"Reg Edwards" wrote -
It is possible to imagine the so-called SWR meter is telling you the
imaginary value of the SWR on a non-existent transmission line. But
it's
hardly of educational value when novices, even experienced engineers,
are
trying to understand what the reading really means. It's as confusing
and
as untruthful as Blair.

Why don't we accept the simple fact that the meter tells us only
whether
the transmitter is loaded with a resistance of a particular value or
not.
Which is no more nor less than what the instrument on the front panel
of your transceiver is provided for.

Then we can forget all about SWR, fwd and reflected power, until
needed
on real ines. Change the name of the meter to TLI.

====================================

Amen to that. I turned down the power on my transmitter, and measured P
forward and P rev while feeding about 100 feet of unterminated 9913. I
then
REMOVED the coax; i.e. there was nothing connected to the output side of
the
meter. Still measured the same Pf and Pr. (Daiwa meter)

Tam/WB2TT

====================================

Tam, what did I tell you ?

Your meter twice indicated the correct valuable information : In neither
case was your transmitter loaded with 50 ohms!

To complete the experiment connect a good, + or - 5 percent, 50-ohm
dummy-load to the meter. At 1.9, 3.8 or 7 MHz you can check the quality
of
the dummy load with a DC ohmeter. The actual DC resistance will depend on
how hot is the dummy load. It can probably be adjusted over an appreciable
range just by varying its temperature.

If the meter indicates an SWR less than about 1.15 then again it provides
the correct valuable information : The transmitter load is in the right
ball park. (Over here, Euro-side, we say in the "right street".)

To calibrate the meter, to make it even more "right", there's a little
preset resistor or capacitor inside the meter box. Twiddle it until a
minimum value of SWR is indicated at 7 MHz when the dummy load is
connected.
Or if the user is accustomed to work mostly at higher frequencies then it
can be twiddled at 21 MHz.

A meticulous amateur, proud of his shack and workmanship, may remove the
redundant SWR scale graduations and paint in their place two coloured
bands,
green = good, red = bad, according to artistic preferences.

Incidentally, to accurately determine transmitter power output just use a
diode+capacitor+DC voltmeter across the dummy load and calculate P =
(V-squared) / 100 watts. At HF it will usually be found to be within +/-
10
percent of what a reputable transceiver manufacturer says it is. And it
can
then be forgotten about. A 10 percent difference in power corresponds to
1/15th of an S-unit.

Tam, I'm sure you're already familiar with the foregoing procedures. I
describe them on these walls for the benefit of novices, CB-ers, etc., and
anyone else who studiously reads through these interminable threads in the
vain hope of learning anything from (Z-Zo)/(Z+Zo).

I have a guilty conscience - it was I who began the rho = 1+Sqrt(2) and
rho
= (Z-Zo) / (Z+Zo) threads. My excuse is that I was measuring and
investigating values of rho greater than unity 10 years before Chipman
issued his book in October 1968. But by then I had migrated to an entirely
different field.
----
Reg, G4FGQ

Keith wrote:
"But the quantities being measured are line volts and line amps and
neither is proportional to incident or reflected watts."

Bird states:
"Where should the wattmeter be inserted? Again referring to the
formulas, we see that the elements extract a voltage proportional to
either Ef or Er, while the total E varies along an improperly terminated
50-ohm line, the component voltages do not. This is simply another way
of saying that the energy in the forward wave remains the same from the
source to the load, where some or all of it is reflected (unless the
load is 50 ohms) and that reflected energy remains constant from the
load back to the source. Our directional power meters can, therefore, be
placed anywhere between the source and the load."

I don`t guarantee a perfect copy of Bird`s Technical Series extract. You
should request your own copy from Bird.

Best regards, Richard Harrison, KB5WZI

wrote:
My interest is with highlighting the lack of generality of the
reflected power model.

Every model, including yours, has limitations and should not be
misapplied.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Harrison wrote:

Keith wrote:
"How does Terman first write of the power in these waves?"

I don`t remember chapter and verse anymore. So, I can`t say where Terman
first writes of power in these waves. On page 88 of Terman`s 1955
edition he says:
"At radio frequencies it is nearly always permissible to assume that
omega L R, and omega C G. To the extent that it is true, one can
rewrite Eqs. (4-5) and (4-7) as follows:
Zo = sq rt L/C

This means current is in-phase with voltage in the waves in both
directions.

In-phase volts and amps are real power, not apparent power.

Maybe. Sort of. Not necessarily.

I agree completely when the volts and amps are the measurable
resultant volts and amps.

But when the volts and amps are contributary terms to a
superposition solution, then, in general (using my definition
of general), multiplying them to produce watts is an
invalid operation since the watts terms can not be superposed
to obtain resultant watts.

It is, I suspect, for this reason that Johnson is fuzzy about
the power in forward and reverse waves; superposition, does
not, in general, apply for power.

The question is, was Terman similarly circumspect?

....Keith

Richard Harrison wrote:

Keith wrote:
"But the quantities being measured are line volts and line amps and
neither is proportional to incident or reflected watts."

Bird states:
"Where should the wattmeter be inserted? Again referring to the
formulas, we see that the elements extract a voltage proportional to
either Ef or Er, while the total E varies along an improperly terminated
50-ohm line, the component voltages do not. This is simply another way
of saying that the energy in the forward wave remains the same from the
source to the load, where some or all of it is reflected (unless the
load is 50 ohms) and that reflected energy remains constant from the
load back to the source.

It is not surprising that they should write this, after all they do
mark their instruments in watts, so they likely believe it.

But is it correct?

Our directional power meters can, therefore, be
placed anywhere between the source and the load."

This part is true.

I don`t guarantee a perfect copy of Bird`s Technical Series extract. You
should request your own copy from Bird.

Since the whole question is about whether what Bird does is correct,
they hardly stand as someone who can resolve the question.

....Keith

Cecil Moore wrote:

wrote:
... the quantities being measured are line volts and line amps
and neither is proportional to incident or reflected watts.

line volts = Vfwd + Vref, line amps = Ifwd + Iref

load power = Vfwd*Ifwd - Vref*Iref at the load

Not with my math....

power = volts * amps
= (Vfwd + Vref) * (Ifwd + Iref)
= Vf*If + Vf*Ir + Vr*If + Vr*Ir

Seems you've lost a couple of terms in there.

This is why, in general (using my definition of general), superposition
does not hold for power. Those extra terms get in the way.

Much happens to the measured voltage and current before the result is
inaccurately interpreted as forward and reverse power.

If you wade through the math you will see why it works for low-loss
feedlines.

You have started to state this caveat.

Does this mean that forward and reverse waves only have power in
the special case of low-loss feedlines?

Where is that example that proves your assertion that reflected waves
don't exist? How do standing waves occur when there are only forward-
traveling waves?

With my model, incident and reflected VOLTAGE waves and CURRENT waves
do exist. This is in common, I think, with most authors on the subject.
And this all works fine since superposition holds for voltage
and current.

What does not exist in general (using my definition of general) is
POWER in these incident and reflected voltage and current waves.
While a power term can be computed, and correct results will be
obtained in some special cases, in general (using my definition
of general), this is an invalid operation because superposition
does not hold for power.

This, I suspect, is the reason that at least one author has
carefully chosen fuzzy words when describing the 'power' in
the waves.

To recap. Everything with the incident and reflected wave model
works as long as you stick to voltage and current waves. It is only
when extended to include power (as done by Bird and others), that
the model starts to deteriorate.

So to get the right answers in the general case (using my definition
of general), compute your forward and reverse voltages and currents.
Use superposition to derive the resultant voltages and currents at
any point on the line and then use p(t) = v(t) * i(t) to compute
the power, which you may then average if you desire.

In the special case of low loss RF, the shortcut of 'regarding'
the waves as having power will produce an answer that is good
enough. But remembering that you have taken a shortcut and
by only 'regarding' the waves as having power, you will indicate
an enhanced understanding of the subject.

....Keith

This is in common, I think, with most authors on the subject.

============================

. . . . . . and 1 million housewives can't be wrong!

Reg Edwards wrote:

This is in common, I think, with most authors on the subject.

============================

. . . . . . and 1 million housewives can't be wrong!

Touche. I generally (using Cecil's definition of general) dislike
appeals to authority (or the masses), but occasionally let them
slip in when dealing with someone who does.

But knowing that you are watching, I will be more cautious in
the future.

....Keith

Keith wrote:
"I agree completely when the volts and amps are the measurable resultant
voolts and amps."

There is a big problem with resultant volts and amps. It is the
resultant variation in amplitude which is position dependent.

The only average variation in forward and reflected powers is a decline
with distance caused by line loss. Power flows at a constant average
rate into, through, and out of a transmission line. Line loss causes
decline in power along a lossy line.

The convenient way to get useful numbers is to separate energy by its
direction of travel and to measure these. A directional coupler is
needed and the Bird among others does this.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Keith wrote:
"I agree completely when the volts and amps are the measurable resultant
voolts and amps."

There is a big problem with resultant volts and amps. It is the
resultant variation in amplitude which is position dependent.

The only average variation in forward and reflected powers is a decline
with distance caused by line loss. Power flows at a constant average
rate into, through, and out of a transmission line. Line loss causes
decline in power along a lossy line.

The convenient way to get useful numbers is to separate energy by its
direction of travel and to measure these. A directional coupler is
needed and the Bird among others does this.

I'm sorry to keep picking away at this one, but it seems to be
necessary...

The statement that a directional coupler can "separate energy by its
direction of travel" involves some unaware assumptions involving
transmission-line theory.

If we're trying to get that theory right, we have to avoid using it
unawarely in order to prove itself... because that way would let us
"prove" just about anything.

A directional coupler only senses the current (directionally) at a
particular location on the line, and the voltage between the two
conductors at that same location. The directional coupler tells us
NOTHING else. We have to be very literal-minded about that.

We cannot determine the reflection coefficient, the SWR, or what is
happening to the energy, without applying some flavor of
transmission-line theory. When the whole discussion is about getting
that theory right, we have to be very careful to avoid unawarely arguing
in circles.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK wrote:
But when there's an alternative model that works whenever yours does,
and still works when yours doesn't, I'll use that one thank you.

Do you use a calculator for 2 x 3 because you need one for
2.34 x 3.45? You are wasting your life if you use Maxwell's
equations for simple EM problems.

Work smarter, not harder!
--
73, Cecil http://www.qsl.net/w5dxp



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wrote:
In-phase volts and amps are real power, not apparent power.

Maybe. Sort of. Not necessarily.

Please give us an example of coherent in-phase voltage and
current waves that didn't require power from a generator.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:
Ian White, G3SEK wrote:
But when there's an alternative model that works whenever yours does,
and still works when yours doesn't, I'll use that one thank you.

Do you use a calculator for 2 x 3 because you need one for
2.34 x 3.45? You are wasting your life if you use Maxwell's
equations for simple EM problems.

Work smarter, not harder!

The smart way is to use the tool that *always* works - especially when
it's no harder to use.

It's not smart to use a tool that only works some of the time *and* has
nothing extra to offer.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Roy Lewallen wrote:
I couldn't help but notice the use of "can be interpreted as" and "can
be thought of", instead of just "is".

Since what "is" changes with human knowledge, most scientific people
avoid asserting absolutes. Quantum Electro Dynamics indicate that EM
fields do not even exist. Most of our present math models are probably
wrong/incomplete and will eventually be obsoleted. I'm sure Terman and
most other technical authors realized that fact of reality.
--
73, Cecil http://www.qsl.net/w5dxp



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On Mon, 22 Sep 2003 16:09:09 +0100, "Ian White, G3SEK"
wrote:

I'm sorry to keep picking away at this one, but it seems to be
necessary...

The statement that a directional coupler can "separate energy by its
direction of travel" involves some unaware assumptions involving
transmission-line theory.

If we're trying to get that theory right, we have to avoid using it
unawarely in order to prove itself... because that way would let us
"prove" just about anything.

A directional coupler only senses the current (directionally) at a
particular location on the line, and the voltage between the two
conductors at that same location. The directional coupler tells us
NOTHING else. We have to be very literal-minded about that.

We cannot determine the reflection coefficient, the SWR, or what is
happening to the energy, without applying some flavor of
transmission-line theory. When the whole discussion is about getting
that theory right, we have to be very careful to avoid unawarely arguing
in circles.

Hi Ian,

It seems every time you come into conflict, you reject other's
statement as issues of circularity and confusion.

A Directional Coupler is principally a transmission line in itself, a
paired one in fact with controlled leakage between the two. There is
nothing inherently restrained in its operation that enforces this
curious complaint of
A directional coupler only senses the current (directionally) at a
particular location on the line, and the voltage between the two
conductors at that same location. The directional coupler tells us
NOTHING else. We have to be very literal-minded about that.
which as a statement means little beyond the obvious coupling that is
necessary. And to state that NOTHING else is told begs the question:
So What? Nothing else was implied, inferred or demanded, and you
offer nothing to illustrate just what it was you objected to. You
call them "unaware presumptions." WHAT presumptions are they?
Certainly not the same observation I quoted just half a dozen lines
above.

The Bird element is indeed a primitive implementation of a Directional
Coupler. It even discards phase information (in fact, it is
unavailable, but it would still be discarded through rectification and
filtering). The Bird element constitutes a three port Directional
Coupler where a four port coupler would return that phase information
(if it were not then immediately discarded through the same
rectification and filtering). The difference between what is
available and what is not is a design choice enforced by the
application of the instrument, not a shortfall of Directional Couplers
as a class of device.

Directional Couplers are literal transmission line components and the
heart and soul of network analyzers.

73's
Richard Clark, KB7QHC

Richard seems to have a great deal of respect for Terman. So I suggest
that he read Terman's explanation of directional coupler operation in
_Radio Engineering_. In the Fourth Edition, at least, he does so without
a single mention of power, let alone "directional" power or "power waves".

Roy Lewallen, W7EL

Ian White, G3SEK wrote:
Richard Harrison wrote:

Keith wrote:
"I agree completely when the volts and amps are the measurable resultant
voolts and amps."

There is a big problem with resultant volts and amps. It is the
resultant variation in amplitude which is position dependent.

The only average variation in forward and reflected powers is a decline
with distance caused by line loss. Power flows at a constant average
rate into, through, and out of a transmission line. Line loss causes
decline in power along a lossy line.

The convenient way to get useful numbers is to separate energy by its
direction of travel and to measure these. A directional coupler is
needed and the Bird among others does this.


I'm sorry to keep picking away at this one, but it seems to be necessary...

The statement that a directional coupler can "separate energy by its
direction of travel" involves some unaware assumptions involving
transmission-line theory.

If we're trying to get that theory right, we have to avoid using it
unawarely in order to prove itself... because that way would let us
"prove" just about anything.

A directional coupler only senses the current (directionally) at a
particular location on the line, and the voltage between the two
conductors at that same location. The directional coupler tells us
NOTHING else. We have to be very literal-minded about that.

We cannot determine the reflection coefficient, the SWR, or what is
happening to the energy, without applying some flavor of
transmission-line theory. When the whole discussion is about getting
that theory right, we have to be very careful to avoid unawarely arguing
in circles.

Ian White, G3SEK wrote:
The smart way is to use the tool that *always* works - especially when
it's no harder to use.

It's not smart to use a tool that only works some of the time *and* has
nothing extra to offer.

The something extra is simplicity. The equations for a small loop, for
instance, are not the full equations but a simplified version. Virtually
all of our often-used equations are simplified versions.

Every electronic instrument we use only works some of the time.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Clark wrote:
Simply put, you lack the meaningful discussion of just what error is
exhibited by any particular issue.

I'm sure that everyone is familiar with the famous light-bending experiment
that proved Newtonian physics wrong and Einstein right. Also, prior to Einstein,
the laws of physics were incorrect with respect to the orbit of Mercury.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Clark wrote:
Hi Ian,

It seems every time you come into conflict, you reject other's
statement as issues of circularity and confusion.

Now that you mention it, that could indeed be a common factor at the
root of this newsgroup's chronically unresolved arguments.

A Directional Coupler is principally a transmission line in itself, a
paired one in fact with controlled leakage between the two.

Some UHF/microwave directional couplers consist of a primary
transmission line (the 'through' line) and a secondary transmission line
for sampling; but not all directional couplers are of this type. Many
types of directional coupler contain no kind of secondary transmission
line. Some have a bridge configuration - for example the Bruene bridge
and the resistor bridge.

At HF through VHF, even the Bird element is better analysed as an
electrically small loop that samples V and I components from the main
line, and not as a section of secondary transmission line. You only need
to consider a Bird element as a secondary transmission line at
frequencies where the loop dimensions are a significant fraction of a
wavelength, so its distributed properties become important.

There is
nothing inherently restrained in its operation that enforces this
curious complaint of
A directional coupler only senses the current (directionally) at a
particular location on the line, and the voltage between the two
conductors at that same location. The directional coupler tells us
NOTHING else. We have to be very literal-minded about that.
which as a statement means little beyond the obvious coupling that is
necessary. And to state that NOTHING else is told begs the question:
So What? Nothing else was implied, inferred or demanded, and you
offer nothing to illustrate just what it was you objected to.

It was all there, but you missed it. Possibly your mind was on your own
reply.

You
call them "unaware presumptions." WHAT presumptions are they?

The presumption is that a directional coupler directly samples power,
when in fact it doesn't. It samples voltage and current separately. The
sampled current is passed through a resistor to develop a second
voltage, and then these two RF voltages are either added or subtracted.
Finally the resultant RF voltage is detected.

Nowhere in this process is there anything that could be described as
directionally sampling power. So any argument about transmission theory
that calls upon that unfounded notion as part of its "evidence" is not
going to get us anywhere useful.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

On Mon, 22 Sep 2003 16:01:21 -0500, Cecil Moore
wrote:

Richard Clark wrote:
Simply put, you lack the meaningful discussion of just what error is
exhibited by any particular issue.

I'm sure that everyone is familiar with the famous light-bending experiment
that proved Newtonian physics wrong and Einstein right. Also, prior to Einstein,
the laws of physics were incorrect with respect to the orbit of Mercury.

Hi Cecil,

Einstein proved apples fall up? What a laugh.

Did Einstein prove
F M · A ?

Einstein's observation
E = M · C²
discounts your jejune platitudes completely.

And how different was Newton's gravity from Einstein's? Simply
exhibited by your failure to respond, shows you lack the meaningful
discussion of just what error is. Cecil, you remain the ever
unreliable correspondent.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Einstein having "changed" what "is" understood of gravity from Newton's
teachings does not invalidate Newton's work

I entirely agree, Richard! (Don't be too surprised :-)

By quantifying the errors in Newton's original 'laws', Einstein actually
*confirmed* that Newtonian mechanics are valid for everyday situations.
The only way Einstein could have found that out was by exploring beyond
Newton, and then looking back.

That's exactly what we're trying to do with the present discussions
about lines with reactive Zo. We're trying to quantify the errors in the
formulae and definitions that we normally use, and we can only do that
by exploring beyond them... very carefully.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Richard Harrison wrote:

Ian says he has a Bird wattmeter. Congratuletions! He has a good
instrument if it is in good shape. I expect his experience has been
satisfactory.

It has indeed, for all practical purposes.

But when we're constructing rigorous bench or thought-experiments to
prove or disprove some aspect of transmission line theory, we have to
remember that, in the very strictest sense, the Bird doesn't actually
measure power.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

On Mon, 22 Sep 2003 22:46:24 +0100, "Ian White, G3SEK"
wrote:
You
call them "unaware presumptions." WHAT presumptions are they?

The presumption is that a directional coupler directly samples power,
when in fact it doesn't. It samples voltage and current separately.

Hi Ian,

A Directional Coupler consists of two transmission lines.
Transmission Lines are the media through which B/H waves migrate
inexorably fixed together. The premise (which you alone bring as a
clouded presumption) that the Bruene bridge somehow works with
independence from this is simply a convenience in discussing its
operation, a convention of discussion at best and not a reality.

73's
Richard Clark, KB7QHC

On Mon, 22 Sep 2003 17:01:54 -0500, Cecil Moore
wrote:
Richard, you really need to learn the difference between an exclusive statement
and an inclusive statement. All you need to ask yourself is, "Did Einstein
ever prove Newton to be wrong?" The answer is 'yes'.

Hi Cecil,

Did Newton ever prove Einstein was wrong? The answer is yes there
too. So where does that leave either of them, and you. You standing
there flat-footed without context as usual.

73's
Richard Clark, KB7QHC

On Mon, 22 Sep 2003 23:05:56 +0100, "Ian White, G3SEK"
wrote:
That's exactly what we're trying to do with the present discussions
about lines with reactive Zo. We're trying to quantify the errors in the
formulae and definitions that we normally use, and we can only do that
by exploring beyond them... very carefully.

Hi Ian,

Too much is given to care, and too little is given to error.

It must have been months ago that this issue of a forced error was
revealed to occur in frequencies of absolutely no interest to the
Amateur for RF Power distribution.

From then on its been a simple ego struggle postured in high tea drama
to give some civil appearance to this tarted up "care." Given no one
has actually said anything original, nor different (and where news of
a virus eclipses this for technical discussion) it proves tedious
without mention of that same discussion of error that would illuminate
the sham in stark relief.

73's
Richard Clark, KB7QHC

Cecil Moore wrote:

wrote:
In-phase volts and amps are real power, not apparent power.

Maybe. Sort of. Not necessarily.

Please give us an example of coherent in-phase voltage and
current waves that didn't require power from a generator.

May I suggest that if you had read the posting to which I
responded and the rest of my response you would have found
exactly the example you are looking for: the forward
voltage and current on a transmission line when a standing
wave is present (and the reflected as well).

....Keith

You never measured the incident voltage. And you refused to measure the
end of the inductor, with the capacitor removed (even with the 15 pF, it should
tell us something about Vi).




This may be true, but are you saying that a capacitor can reflect an
RMS voltage wave that is greater than the one that charges it?

Yes indeed. Resonant circuits achieve this with ease.

...Keith


Absolutely incorrect! If capacitance is defined as Coulombs/Volt, then
how are you getting more coulombs than you put in? Remember, i said Root Mean
Square voltage.

How does a capacitor reflect more power than you feed it?

It's almost time for me to cut out of this discussion, if you still don't
understand me.


Slick

Richard Clark wrote:
On Mon, 22 Sep 2003 17:01:54 -0500, Cecil Moore
wrote:

Richard, you really need to learn the difference between an exclusive statement
and an inclusive statement. All you need to ask yourself is, "Did Einstein
ever prove Newton to be wrong?" The answer is 'yes'.

Did Newton ever prove Einstein was wrong? The answer is yes there
too.

I'll take your word for that being true. So what? The argument was
whether Einstein ever proved Newton to be wrong. He did.
--
73, Cecil http://www.qsl.net/w5dxp



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wrote:
May I suggest that if you had read the posting to which I
responded and the rest of my response you would have found
exactly the example you are looking for: the forward
voltage and current on a transmission line when a standing
wave is present (and the reflected as well).

How did the standing wave get there in the first place? *POWER*
from the generator. You simply cannot have standing waves without
a power source, a forward wave, and a reflected wave.

You are asking us to completely ignore the cause of standing waves.
--
73, Cecil http://www.qsl.net/w5dxp



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