Dave wrote:

"Cecil Moore" wrote:
What I am willing to discuss in detail is what happens at a Z0-match
point (x) in an antenna system with reflections - something like the
following:

what you are willing to discuss is irrelevent as it has nothing to do with
the original topic which was about what happens in the transmitter.

Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.

For these typical conditions, all voltages and currents are either
in-phase or 180 degrees out of phase at the match point (x), which
makes a power analysis the most simple analysis of all.

that should read "For these specific conditions", those conditions are
hardly 'typical', they are a very exactly contrived example which makes it
easy to compare powers.

No, those are typical conditions, where the ham radio antenna system
is tuned to a Z0-match by a tuner, either external or internal. It is
not a "very exactly contrived example" at all. It is absolutely typical
of any ham radio installation where the final amp sees close to a 1:1 SWR
and that is the great majority. At the Z0-match point at the input of
every properly tuned transmatch, the voltages and currents are either in
phase or 180 degrees out of phase. If you don't know that, it is no
wonder that you label my power analysis stuff as "contrived".
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Dave wrote:

"Cecil Moore" wrote:
What I am willing to discuss in detail is what happens at a Z0-match
point (x) in an antenna system with reflections - something like the
following:

what you are willing to discuss is irrelevent as it has nothing to do
with
the original topic which was about what happens in the transmitter.

Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.


here is the original:

I know that any power not dissipated by an antenna is reflected back to the
transmitter. Then the transmitter "reflects" this reflection back to
antenna, ad nauseum until its all gone. I also know that a short or an open
is required to reflect power and I'm searching for which it is, an open or a
short. I'm inclined to think it's a virtual open but I'm at a loss to
understand that and I wonder if someone has a good explanation or analogy
and some math wouldn't hurt.
tnx
Hank WD5JFR

obviously not about what is going on at some contrived transmission line
joint.


For these typical conditions, all voltages and currents are either
in-phase or 180 degrees out of phase at the match point (x), which
makes a power analysis the most simple analysis of all.

that should read "For these specific conditions", those conditions are
hardly 'typical', they are a very exactly contrived example which makes
it
easy to compare powers.

No, those are typical conditions, where the ham radio antenna system
is tuned to a Z0-match by a tuner, either external or internal. It is
not a "very exactly contrived example" at all. It is absolutely typical
of any ham radio installation where the final amp sees close to a 1:1 SWR
and that is the great majority. At the Z0-match point at the input of
every properly tuned transmatch, the voltages and currents are either in
phase or 180 degrees out of phase. If you don't know that, it is no
wonder that you label my power analysis stuff as "contrived".

of course it is contrived. no one uses loads of those exact impedances, or
lengths of coax like you do.

Dave wrote:

Cecil wrote:
Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.

here is the original:

Are you saying that the original subject was wrong?

of course it is contrived. no one uses loads of those exact impedances, or
lengths of coax like you do.

Dave, have you ever heard of an example? What I posted is one
easy-to-understand example of virtually an infinite number of
possible examples of a Z0-match. If you like, here is another
example of a Z0-match:

XMTR------tuner---unknown length of feedline---unknown load
100W--
--0W

There is a Z0-match at the input of the tuner. All the voltages
and all the currents are very close to in-phase or 180 degrees
out of phase at the input of the tuner. Do you have the balls to
assert that the above configuration is "contrived"?

THE GREAT MAJORITY OF AMATEUR RADIO ANTENNA SYSTEMS ACHIEVE CLOSE
TO A Z0-MATCH!!! That means all the voltages and currents are close
to being in phase or 180 degrees out of phase. I'm sorry that technical
fact hairlips you. Since your hidden agenda is hidden, I can only
guess what it might be.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Dave wrote:

Cecil wrote:
Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.

here is the original:

Are you saying that the original subject was wrong?

no, only that you ignored the body of the message and answered what you
wanted to discuss instead of what was asked.


of course it is contrived. no one uses loads of those exact impedances,
or
lengths of coax like you do.

Dave, have you ever heard of an example? What I posted is one
easy-to-understand example of virtually an infinite number of
possible examples of a Z0-match. If you like, here is another
example of a Z0-match:

XMTR------tuner---unknown length of feedline---unknown load
100W--
--0W

There is a Z0-match at the input of the tuner. All the voltages
and all the currents are very close to in-phase or 180 degrees
out of phase at the input of the tuner. Do you have the balls to
assert that the above configuration is "contrived"?

nope, that is a real world situation, but not the one under discussion.


THE GREAT MAJORITY OF AMATEUR RADIO ANTENNA SYSTEMS ACHIEVE CLOSE
TO A Z0-MATCH!!! That means all the voltages and currents are close
to being in phase or 180 degrees out of phase. I'm sorry that technical
fact hairlips you. Since your hidden agenda is hidden, I can only
guess what it might be.

so which is it, in phase or 180 degrees out of phase???

Dave wrote:
no, only that you ignored the body of the message and answered what you
wanted to discuss instead of what was asked.

Yes, I did. I didn't know anything about the original question so
I kindly offered to discuss something I know something about. If that
is against netnews guidelines, could you show me where it says so?

nope, that is a real world situation, but not the one under discussion.

A 1/4WL matching section is not a "real world situation"? Since when?
Everything I post is a real-world situation except for the obvious,
e.g. one-second long lossless transmission lines.

so which is it, in phase or 180 degrees out of phase???

It depends upon which signal we are talking about and whether the
impedance discontinuity steps-up or steps-down. Assuming the generated
forward wave (a1) has the voltage and current in phase at zero degrees:

For a step-up impedance discontinuity, the s11(a1) reflection term
will have the voltage at zero degrees (and the current at 180 degrees).

For a Z0-match, b1 will be zero so s12(a2) must be equal magnitude
and opposite phase to s11(a1). That puts the reflection from the
load with voltage at 180 degrees (and current at zero degrees).
All interference at port1 is totally destructive for a Z0-match.

The s21(a1) term has voltage at zero degrees (and current at zero
degrees). All interference at port2 is constructive so s22(a2) also
has the voltage at zero degrees (and current at zero degrees).

For a step-down impedance discontinuity associated with a Z0-match,
the phases of the reflected voltages and currents are shifted by 180
degrees and b1 still equals zero.

The above is exactly what happens at the match point at the input
of a tuner. ***Therefore, the great majority of ham radio antenna
systems have the voltages and currents either in-phase or 180 degrees
out of phase at the tuner match point.*** In fact, all a tuner does is
shift the magnitude and phase of the reflected waves from a mismatched
antenna to be equal in magnitude and 180 degrees out of phase with the
reflections from the match point. Therefore, all reflections are canceled
at the match point but not between the match point and the antenna.

This was all explained 64 years ago (when I was two years old) by J. C.
Slater in _Microwave_Transmission_. Why do I have to explain it all over
again?
--
73, Cecil http://www.qsl.net/w5dxp



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On Mon, 24 May 2004 12:49:39 -0500, Cecil Moore
wrote:
I didn't know anything about the original question
Stock answer.

This was all explained 64 years ago (when I was two years old) by J. C.
Slater in _Microwave_Transmission_. Why do I have to explain it all over
again?
Possibly because you so ill understood it then as now?

Richard Clark wrote:

wrote:
This was all explained 64 years ago (when I was two years old) by J. C.
Slater in _Microwave_Transmission_. Why do I have to explain it all over
again?

Possibly because you so ill understood it then as now?

Well Richard, here's your chance. Please enlighten us on J.C.
Slater's meaning of: "The method of eliminating reflections
is based on the interference between waves. ... The fundamental
principle behind the elimination of reflections is then to have
each reflected wave canceled by another wave of equal amplitude
and opposite phase."
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Dave wrote:
no, only that you ignored the body of the message and answered what you
wanted to discuss instead of what was asked.

Yes, I did. I didn't know anything about the original question so
I kindly offered to discuss something I know something about. If that
is against netnews guidelines, could you show me where it says so?

of course it is against guidelines. you were starting a new thread without
changing the subject. in effect hijacking the thread for your own
discussion.


nope, that is a real world situation, but not the one under discussion.

A 1/4WL matching section is not a "real world situation"? Since when?
Everything I post is a real-world situation except for the obvious,
e.g. one-second long lossless transmission lines.

i said it was real world, but it is not what the original thread was about.

Dave wrote:
of course it is against guidelines. you were starting a new thread without
changing the subject. in effect hijacking the thread for your own
discussion.

Of course, it is not against the guidelines as the subject was "Reflected
Power". I simply continued to talk about reflected power, the subject of
the thread. That's a broad subject. Perhaps the originator erred in choosing
that broad of a subject but he chose that subject nevertheless. All of my
postings to this thread have been about reflected power, including this one,
in defense of my postings about reflected power.

i said it was real world, but it is not what the original thread was about.

The original thread was about "Reflected Power". My example was about
reflected power. I might not even have read the text of the original
posting. It would be interesting to know why your agenda requires
diverting the issue away from "reflected power"? What are you afraid of?
--
73, Cecil http://www.qsl.net/w5dxp



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