Tom Donaly wrote:
Cecil Moore wrote:
"Reg Edwards" wrote:

Sorry Cec, but I havn't the foggiest idea what you are talking about.


Let me ask it a little differently. We all know what a plot of the
standing
wave current magnitude looks like up and down an open-circuit
transmission
line.

But what does a plot of the associated standing wave current *phase* look
like up and down that same open-circuited transmission line?
--
73, Cecil, W5DXP



By now you should be able to calculate that, Cecil.
73,
Tom Donaly, KA6RUH

Indeed. And I even gave the answer some time ago -- the phase of the
total current (which Cecil seems to like calling the "standing wave"
current) is the same all along the line. That's true only for the case
of a line that's completely short or open circuited. In any other case,
the phase of total voltage and current vary along the line. This can be
easily calculated by adding the values of the forward and reverse
traveling waves at each point to get the total at each point. Or, if
you're lazy, just plug the numbers into the equations you'll find in
_Reference Data for Radio Engineers_ or your favorite reference. Or if
you're lazier yet you can model a transmission line with EZNEC or the
modeling program of your choice and let it tell you what the phase of
the current is at each point along the line. Any of the three methods
will give the same result if done correctly.

As I mentioned before, a plucked guitar string is a good physical
analogy. Each point along the string moves in the same direction at the
same time, showing that the motions at all points along the string are
in phase.

That's very basic transmission line theory. If Cecil really doesn't know
the answer to the question he asked, it's no wonder he has such
conceptual problems with inductors and transmission lines.

Roy Lewallen, W7EL