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#11
August 27th 03, 03:01 AM
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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 |
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