On Sun, 15 Apr 2007 09:18:28 -0500, Cecil Moore wrote:

Walter Maxwell wrote:
... then coherent fields traveling in a transmission line must also interact,
interfere, or sum.

There is no doubt that Roy is absolutely wrong when he
asserts that coherent EM waves do not interact. Every
time we tune our antenna tuners to zero reflected energy,
we are causing EM waves to interact following the rules
of *linear* interference. All those waves, inductors,
and capacitors within the antenna tuner are operating
within a linear environment. If they weren't, we would
generate lots of harmonics.

Seems to me, the only valid point of argument is whether
a purely virtual impedance is a cause or an effect.

I quote from Terman, 1947 ed. page 109:
"The distance L1 from the load, and the length 'a' of the stub, are so chosen that the reflected wave produced
by the shunting impedance of the stub is equal in magnitude and opposite in phase to the reflected wave
existing on the line at this point as a result of the reflection from the load impedance ZL. Thus, although a
reflected wave is present in the length L1 because of the reflection from ZL, there is no reflected wave on
the generator side of the stub line as a result of the cancellation of the two reflected waves."

I maintain that Terman's statements above agree precisely with my statements introducing this thread, in which
I sum the reflection coefficients of the load and stub reflections to determine the cancellation of the two
reflected waves that result in the impedance match. Call it what you like, the condition at the stub point
totally re-reflects the two sets of reflected waves, but allows total passage of the source waves through the
junction of the main line and the stub.

Seems to me that the only disagreement with my original posting is whether the condition at the stub point can
be called a 'virtual' short circuit. If I'm outvoted on that term how about selecting another term for it that
everyone can agree on. I'm sure there is no disagreement on the wave analysis of the stub matching circuitry.

Walt, W2DU