Standing Wave Phase
 

Keith Dysart wrote:
Well, I know what I mean by 1/4WL and in my
definition there is no way that (46.4 + 10) = 90.

Of course, those are *physical* degrees. We are
talking about *electrical* degrees. It is impossible
to get the reflected wave in phase with the forward
wave unless there is an electrical 90 degree phase
shift.

If you lay the 43.4 degrees out starting at Z=0
toward the load on the Smith Chart and lay the
10 degrees out starting at Z=infinity toward the
source, you will observe the phase shift caused
by the impedance discontinuity.

... the only
way to determine if something is 90 degrees
(according to your definition) is to ask you.

All one has to do is plot it on a Smith Chart
and the number of electrical degrees is obvious.
If you don't know how to use a Smith Chart it
might be time to learn how.
--
73, Cecil http://www.w5dxp.com

Standing Wave Phase
 

On Dec 9, 12:21 am, Cecil Moore wrote:
Keith Dysart wrote:
Well, I know what I mean by 1/4WL and in my
definition there is no way that (46.4 + 10) = 90.

Of course, those are *physical* degrees.

Yes indeed. And they have the benefit of concreteness
and they are easy to account.

We are
talking about *electrical* degrees. It is impossible
to get the reflected wave in phase with the forward
wave unless there is an electrical 90 degree phase
shift.

Except that I have offerred a number of examples
which you, the oracle, have declared are not
90 "electrical degrees".

If you lay the 43.4 degrees out starting at Z=0
toward the load on the Smith Chart and lay the
10 degrees out starting at Z=infinity toward the
source, you will observe the phase shift caused
by the impedance discontinuity.

I, too, can subtract (43.4 + 10) from 90 and get
a number. This does not, by itself, a useful
proposition make.

... the only
way to determine if something is 90 degrees
(according to your definition) is to ask you.

All one has to do is plot it on a Smith Chart
and the number of electrical degrees is obvious.

Please provide your algorithm in sufficient detail
that I can test it against the various examples.

So far, each time you have provided a rule, I
have constructed examples according to the
rule which the oracle has declared are not
90 "electrical degrees". Without a testable
rule that successfully distinguishes those
cases which are 90 "electrical degress"
from those which are not, there is nothing.

Having to ask the oracle does not suffice.

And the Smith chart is insufficient. One of your
examples began with "take the impedance
of 0-j567 and plot it on the chart", which is
okay, but it turned out that how that impedance
was created is important. It had to be a
capacitor (sometimes). No amount of Smith
charting will reveal that detail.

A testable rule, please...

....Keith

Standing Wave Phase
 

Keith Dysart wrote:
Except that I have offerred a number of examples
which you, the oracle, have declared are not
90 "electrical degrees".

If it is 90 electrical degrees then it is 90
electrical degrees. If it is not 90 electrical
degrees, it is not 90 electrical degrees. I don't
know how to make it any clearer than that.

I, too, can subtract (43.4 + 10) from 90 and get
a number. This does not, by itself, a useful
proposition make.

It does if we know the reflected wave undergoes a
180 degree round-trip phase shift or else the
reflected wave would not be in phase with the
forward wave and therefore the feedpoint impedance
would not be purely resistive.

Please provide your algorithm in sufficient detail
that I can test it against the various examples.

It's the same as determining if an antenna is 0.5WL
or 1.5WL or 2.5WL or 3.5WL or ... Do you also have
a problem with that?

If the phase shift end-to-end is 180 degrees, the
device is 90 electrical degrees long.

If the phase shift end-to-end is not 180 degrees,
the device is not 90 electrical degrees long.

So far, each time you have provided a rule, I
have constructed examples according to the
rule which the oracle has declared are not
90 "electrical degrees".

I have provided no rule. Everything is common sense.
If a dipole is 130 feet, it is 1/2WL on ~3.6 MHz.
If the antenna is 403 feet long, it is 1.5WL on
~3.6 MHz. Why do you have a problem telling the
difference between a 130 foot dipole and a 403
foot dipole?
--
73, Cecil http://www.w5dxp.com

Standing Wave Phase
 

Cecil Moore wrote:

...
It does if we know the reflected wave undergoes a
180 degree round-trip phase shift or else the
reflected wave would not be in phase with the
forward wave and therefore the feedpoint impedance
would not be purely resistive.
...


Or, to sum that up in a nut shell, "Does everyone here know we can
reverse the leads on our SWR meter (input goes to output--output goes to
input) and the fwd/ref switch will just work "backwards." (but, readings
should remain the same.)

Indeed, an excellent way to check homebuilt SWR bridges and make sure
they are "balanced."

Regards,
JS

Standing Wave Phase
 

On Dec 9, 3:27 pm, Cecil Moore wrote:
Keith Dysart wrote:
Except that I have offerred a number of examples
which you, the oracle, have declared are not
90 "electrical degrees".

If it is 90 electrical degrees then it is 90
electrical degrees. If it is not 90 electrical
degrees, it is not 90 electrical degrees. I don't
know how to make it any clearer than that.

I suspect you are correct there.

I, too, can subtract (43.4 + 10) from 90 and get
a number. This does not, by itself, a useful
proposition make.

It does if we know the reflected wave undergoes a
180 degree round-trip phase shift or else the
reflected wave would not be in phase with the
forward wave and therefore the feedpoint impedance
would not be purely resistive.

Please provide your algorithm in sufficient detail
that I can test it against the various examples.

It's the same as determining if an antenna is 0.5WL
or 1.5WL or 2.5WL or 3.5WL or ... Do you also have
a problem with that?

I use a measuring tape for that, so there is no
problem. But if I recall correctly, your definition
of 90 degress is not amenable to the use of
measuring tapes.

If the phase shift end-to-end is 180 degrees, the
device is 90 electrical degrees long.

If the phase shift end-to-end is not 180 degrees,
the device is not 90 electrical degrees long.

So far, each time you have provided a rule, I
have constructed examples according to the
rule which the oracle has declared are not
90 "electrical degrees".

I have provided no rule. Everything is common sense.

Everyone thinks they are full of "common sense" and
that few others are. Science is not advanced by claiming
common sense.

If you do not have articulatable rules, then you do
not even have a hypothesis, much less a theory.

If a dipole is 130 feet, it is 1/2WL on ~3.6 MHz.
If the antenna is 403 feet long, it is 1.5WL on
~3.6 MHz. Why do you have a problem telling the
difference between a 130 foot dipole and a 403
foot dipole?

No problem. But I am allowed to use a measuring
tape to answer that question.

And if you wrote a rule using measuring tapes for
this 90 degree stuff, I would have no trouble with it
either.

But if the best you can do is claim "common
sense", you can be sure that my "common
sense" will arrive at different answers than yours.

....Keith

Standing Wave Phase
 

Keith Dysart wrote:
If you do not have articulatable rules, then you do
not even have a hypothesis, much less a theory.

The theory I support is the distributed network
model. It was invented before you or I were born.
I do not have to defend it. If you disagree with
it, you have to prove it false.
--
73, Cecil http://www.w5dxp.com

Standing Wave Phase
 

On Dec 9, 8:50 pm, Cecil Moore wrote:
Keith Dysart wrote:
If you do not have articulatable rules, then you do
not even have a hypothesis, much less a theory.

The theory I support is the distributed network
model. It was invented before you or I were born.
I do not have to defend it. If you disagree with
it, you have to prove it false.

A truly intriguing riposte: completely devoid of
technical content, fails to further the discussion
in any way, and yet deeply revealing about the
thought processes at work.

....Keith

Standing Wave Phase
 

Keith Dysart wrote:
On Dec 9, 8:50 pm, Cecil Moore wrote:
Keith Dysart wrote:
If you do not have articulatable rules, then you do
not even have a hypothesis, much less a theory.

The theory I support is the distributed network
model. It was invented before you or I were born.
I do not have to defend it. If you disagree with
it, you have to prove it false.

A truly intriguing riposte: completely devoid of
technical content, fails to further the discussion
in any way, and yet deeply revealing about the
thought processes at work.

I'm disappointed in you, Keith. You appeared to be
a reasonably intelligent person. Now that you have
apparently performed my suggested experiment and
know that I am right, you try to tuck your tail
and run. I'm disapointed, but not surprised.
--
73, Cecil http://www.w5dxp.com

Standing Wave Phase
 

On Dec 9, 10:14 pm, Cecil Moore wrote:
I'm disappointed in you, Keith. You appeared to be
a reasonably intelligent person.

Thank you. And I continue to be so.

Now that you have apparently performed my suggested
experiment

There is no evidence that I have performed the experiment.
The need for current probes probably means that I will not
be doing so, though you never know. Rest assured that
should I do so, results will be published.

and know that I am right, you try to tuck your tail
and run.

Ahhh, your favourite accusation. You play the game
of last man standing, and when everyone has left
the field (in this case because you had nothing
further technical to add), you convince yourself
that it is because you must be right, and they
must know it. I can't decide if this logic is
more amusing or sad.

Now if you want to recover, make some better
attempts to write the rule. Look back through
the posts for your sentences that begin with
"Can we agree that", or some such. These
were your attempts at a rule. Complete them
to the point that we agree that they are self
consistent and accurately convey your
definition and we will have gotten somewhere.

Your later attempts, which amount to "I
know it when I see it", were not nearly as
good as your earlier ones.

....Keith

Standing Wave Phase
 

Keith Dysart wrote:
Now if you want to recover, make some better
attempts to write the rule. Look back through
the posts for your sentences that begin with
"Can we agree that", or some such. These
were your attempts at a rule. Complete them
to the point that we agree that they are self
consistent and accurately convey your
definition and we will have gotten somewhere.

What is it that you need a rule for? Is it the
electrical length of a stub?

The stub is electrically half as long as the phase
shift undergone by the reflected wave during its
round trip to the open or shorted end and
back to the feedpoint.

If that phase shift in a dual-Z0 stub is the same
as the phase shift in a single-Z0 stub at the same
frequency, the two stubs are the same electrical
length at that frequency.
--
73, Cecil http://www.w5dxp.com