On Fri, 03 Oct 2003 14:58:15 -0500, Cecil Moore
wrote:

Richard Clark wrote:
So, a source exhibiting 200 Ohms Resistive feeding a 50 Ohm line that
is then terminated in a load of 200 Ohms Resistive exhibits what SWR?

Assuming a lossless 50 ohm line, the steady-state SWR is 4:1 no
matter what the source impedance (assuming there exists a source
voltage not equal to zero volts). Steady-state SWR in a lossless
feedline is a constant fixed voltage ratio from end to end.

Hi Cecil,

WRONG!

The method of computation you employ violates Chipman and any other of
a host of authoritative sources on the topic. If you actually
attempted to verify this at the bench you would "perhaps" find it at
only one point, or at harmonic distances (wavelength specific) along
the line. That means you would stand only a couple of percent chance
of that with a random choice. Guesses are not responsive to the
intent and no points are awarded.

I will leave you to discover Chipman's means to find SWR any where
along any line for yourself. You might enjoy the celebrity of being
the second to do so. ;-)

73's
Richard Clark, KB7QHC

Richard Clark wrote:
The method of computation you employ violates Chipman and any other of
a host of authoritative sources on the topic. If you actually
attempted to verify this at the bench you would "perhaps" find it at
only one point, or at harmonic distances (wavelength specific) along
the line.

-sigh- One cannot verify anything about lossless lines on the bench.
The only verifications about lossless lines that are possible have to
be done in one's head because that's the only place lossless lines
exist. One can come close with open-wire line and extrapolate the
results to lossless lines. You see the effects more on coax than on
open-wire line simply because coax is lossier than open-wire line.

I will leave you to discover Chipman's means to find SWR any where
along any line for yourself.

You told me to reference page 139 which I did. All that page talks
about is lossy feedline with a complex Z0. The purely resistive feedline,
given by you in your example, cannot have a complex Z0. So what Chipman
has to say is irrelevant to the problem you posed, i.e. purely resistive
Z0, purely resistive source impedance, and purely resistive load. You
apparently should have posed a complex Z0.

Chipman explains perfectly why the measured SWR may vary with a
lossy line, i.e. with a complex Z0. There are points of conjugate
matching up and down the line where an oscillation takes place. The
oscillation causes extra reflections and re-reflections at the
conjugate match point, an exchange of a third energy between the
capacitive reactance and the inductive reactance at that point,
that affects the SWR readings. But such is not possible with the
purely resistive Z0 that you posed.
--
73, Cecil http://www.qsl.net/w5dxp



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On Fri, 03 Oct 2003 16:12:48 -0500, Cecil Moore
wrote:
One cannot verify anything about lossless lines on the bench.

You can't, that's for sure, and not even with a line so short you
couldn't measure its loss - so what's the point of arguing lossless?

So what Chipman
has to say is irrelevant to the problem you posed

Hi Cecil,

I have already provided quotes, chapter and verse that refute your
statement. No point in going further.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
I have already provided quotes, chapter and verse that refute your
statement.

Here's a quote from Chipman. "These large reflection coefficients are an
example of the phenomenon of 'resonant rise of voltage' in series resonant
circuits... The large reflection coefficients are obtained only when the
reactance of the load impedance is of opposite sign to the reactance
component of the characteristic impedance." You posed a purely resistive Z0.
The "resonant rise of voltage" cannot happen with a purely resistive Z0.
Would you like to pose a complex Z0?
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 04 Oct 2003 10:08:40 -0500, Cecil Moore
wrote:
Here's a quote from Chipman.
....
Would you like to pose a complex Z0?

Hi Cecil,

What for? Random selections of quotation are hardly the basis for
discussion. -Eh- let me take that back, it seems it's the ONLY basis
for discussion.

I note, as posed before, that Ian who "might" hold a copy of Chipman
has yet to respond to my points about its contents. My having offered
chapter and verse, it would seem less than a monumental task to simply
turn to the page and verify my selection, or refute Chipman's
statements. Those who hold him dear seem the least likely to respond
to his teachings.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
I note, as posed before, that Ian who "might" hold a copy of Chipman
has yet to respond to my points about its contents.

I have ordered a copy. From what I have read of Chipman so far,
everything can be explained by achieving a conjugate match at
one point on the transmission line when the reactance looking
in either direction is at a maximum. This is simply a resonance
effect. Here's a bench experiment that might shed some light
on this problem.

source--50 ohm coax--(-j500)--SWR meter--(+j500)--50 ohm coax--50 ohm load

There is a localized high reactive energy exchange through the SWR meter
between the capacitance and the coil but nowhere else on the transmission
line. That has got to have an effect on the SWR reading which is probably
not good. What, exactly, is the big deal? It is just another distributed
circuit problem.
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 04 Oct 2003 17:31:31 -0500, Cecil Moore
wrote:

everything can be explained by achieving a conjugate match at
one point on the transmission line when the reactance looking
in either direction is at a maximum.

Hi Cecil,

I don't know which is funnier: that you have a
one-solution-answers-every-question; or that you have so many of them.

Reach into your bag and present us the conjugate for:
source50---50 ohm feedline---+---150 ohm feedline---load150
or the rather more terse (and simpler - bound to confound):
source=200Ohm(resistive)---50 ohm feedline---load=200Ohm(resistive)



73's
Richard Clark, KB7QHC