W5DXP wrote:
wrote:
When excited by a sinusoid, no energy moves at the quarter wave points
where the voltage or current is always 0.
You keep saying that and it keeps being a false statement. There is
absolutely nothing magic about sinusoids.
Seems to me that the sinusoidal standing wave with minima and maxima
at the quarter wave points can only arise with single frequency
sinusoidal excitation of the line. Are there other signals which
will produce this result?
"we know" is rather strong. I would strongly suggest that no energy
crosses those points in the line where the voltage and current are
always zero since p(t) is always zero at these points.
What about Ramo and Whinnery's forward Poynting vector and reflected
Poynting vector? Why do you choose to ignore them?
I haven't used them because I don't need them to arrive at an answer.
Basic electricity, a dash of circuit theory, a bit of knowledge of
trigonometry, some basic calculus and the ability to think is all
that is required.
Why make the solution more complex than necessary?
Just to scare off the neophyte?
Not necessarily. Only once the line has been charged, does the energy
move back and forth between the quarter wave points, while not
crossing them.
That has been shown to be a false assertion regarding component waves.
Perhaps. Or maybe component waves are not the answer.
There is no impedance discontinuity to cause any reflections. Therefore,
the waves do not move back and forth.
Do you really believe that the
energy in a bright interference ring is trapped inside the ring? Get
serious!
In this context, we are discussing transmission lines. I make NO
assertions about light, how rings happen, or don't, or whether the
theory and practice of optics is in way analogous to what happens
on a transmission line.
Transmission lines and their understanding can stand on their own
without the help of optics.
....Keith