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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