AI4QJ wrote:

Roy, this is the part I don't understand about some people posting on this
thread. A standing wave does *not* have a phase shift. The standing wave
stays in a single position and oscillates. The forward and reflected waves
are traveling. An excellent conceptualization of we mean by "standing wave"
with its constructive and destructive interference can be seen he

http://www.chemmybear.com/standing.html

My only problem is, you are the antenna software design guru. I know I must
be missing something big here because I would expect you to be telling
"others" this stuff.

You've described a standing wave, but haven't defined any special kind
of current known as "standing wave current". A standing wave isn't a
current, it's the shape of the magnitude of the voltage or current as a
function of position. I'm sure you can find multiple descriptions of
this on the web, with some being correct and well done, some being
totally wrong, and others at all points between. I tend to look to
published texts for accurate information, and currently have about 14
reputable texts involving transmission lines and electromagnetic waves
on my bookshelf. I surely might have missed it, but I don't recall ever
seeing a reference to "standing wave current" in any of them.

The nature of a standing wave is well known. It describes the envelope
of the distribution of voltage or current on a transmission line
resulting from the sum of forward and reverse traveling waves along a
line not terminated in its characteristic impedance. This envelope,
which has a physical periodicity along the line and which is sinusoidal
in shape only if the SWR is infinite, appears to stand still except for
increasing and decreasing in amplitude at the same rate as the traveling
waves which cause it. So "standing wave current" translates to "envelope
of an interference pattern current". There is no special kind of current
known as "standing wave current" because the combination of words is
meaningless.

Traveling waves interfere to cause the standing wave envelope, as I hope
your web references tell you. When you measure the current at some point
in a transmission line, you're measuring the current at that point,
period. Not "traveling wave current" or some other special kind of
current. The current at any point along a transmission line has a
magnitude and a phase relative to an arbitrary reference. Both can be
easily calculated from basic transmission line principles. You can do it
directly or by adding forward and reflected waves to get the total -- if
you get different results by using the two methods, you've done
something wrong.

For the record, I measured some currents in a wire on both sides of an
inductor at the base of an antenna a couple of years ago and posted the
results here. One of the things I measured, with some care, was the
phase angle between those currents. I didn't "mistakenly" measure
"standing wave current". There is no such thing. I measured sinusoidal
currents, which have phase and magnitude, at two points. The
measurements agreed quite closely with results predicted from
conventional theory. I never was able to tell whether they agreed with
Cecil's theory because he kept changing his predictions.

Note the assertion on the graphic that two waves can be at the same place at
the same time (a subject of a different thread), something I agree with :-)

You'll have to run that one by Cecil. He's said many times that
traveling waves bounce off each other when they meet. That behavior
seems to be necessary to support one of this theories.

Roy Lewallen, W7EL