Roy Lewallen wrote:
John Popelish wrote:

. . .
That's exactly the difference. But if you measure a single point, you
can't tell whether you are measuring a point on a traveling wave or a
standing wave. Agree?


There seems to be some confusion about just what a standing wave is.

A standing wave is the result of, and the sum of, two or more traveling
waves. There aren't points which are "on" one or the other.

Sure there are. If there is a standing wave on a wire, and you have a
tiny current transformer sensor you can slide along the wire, you can
measure the instantaneous current (or the RMS) at any point along the
wire. If the sensor sits at a single point and sees an AC current,
you have no way, from this one measurement, if this current is the
result of a standing wave (two oppositely traveling equal waves
adding), or a single traveling wave, or any combination of traveling
waves of different amplitudes. You know only the net current at that
point.

If you can
separately measure or calculate the values of the traveling current
waves at any point, you can add them to get the total current (what
Cecil calls "standing wave current") at that point.

That is what I mean by the current at a point.

If you add the
traveling current waves at each point along the line and plot the
amplitude of the sum (that is, of the total current) versus position,
you see a periodic relationship between the amplitude and position. It's
this relationship which is called a "standing wave". It's so called
because its position relative to the line stays fixed. It's simply a
graph of the total current (the sum of the traveling waves) vs. position.

I have no disagreement with this description.