Walter Maxwell wrote:
On Sun, 30 Jul 2006 16:04:10 -0700, "Bob Agnew" wrote:

Just a nit: You said:

If there are reflections, the voltage
and current are in phase only every 1/4 wavelength.
Actually, if there are reflections, the voltage and current ar NEVER in
phase.

In fact, voltage and current in the reflected wave are ALWAYS 180° out of phase,
while in the forward wave they are always in phase. Thus, along the line they
alternately add and subtract, first reinforcing and then cancelling each other
at every quarter wave, to form the standing wave.

Walt, W2DU

And, if you assume the line is lossless, the voltage and current are in
phase every 90 degrees along the line regardless of the amount of mismatch.

This is easily illustrated with a Smith chart -- choose any point you'd
like, representing an arbitrary load impedance. Then draw a circle
through that point, with the center of the circle at the chart's origin.
Moving clockwise along this circle represents moving along the
transmission line from the load toward the source. You'll cross the
chart's axis, where the impedance is purely real, in a half revolution
(90 degrees of movement along the line) or less, and cross it each half
revolution (90 degrees) from then on.

Roy Lewallen, W7EL