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John Popelish wrote:
But at any point that is not a node in the standing wave pattern, there will be an ordinary AC voltage or current at some amplitude between double the traveling wave amplitude and zero amplitude, and one of two phases (that switch each time you pass a node). Please give us the equation for "ordinary AC voltage or current". No argument. But a standing wave still represents storage of energy in the line, as with any resonant structure, and that stored energy shows up as magnetic fields and electric fields along the line. The big difference is that the magnetic fields bob up and down at some areas and the electric fields bob up and down half way in between those areas. At any given moment, there is a fixed total energy in the combination of all the magnetic and electric fields. No argument, and therefore no need for the "But" in your statement. I agree with you but it doesn't change a thing about the real argument. Exactly. How can you write this, but deny the capacitive current that delivers this electric field energy twice every cycle to all capacitance feeling this voltage swing? I don't deny it - never have - never will. Please stop trying to set up straw men. The discussion has *NEVER* be about what happens during one cycle. The current measured by W8JI and W7EL and reported by EZNEC is RMS current. Instantaneous values are just another straw man diversion. Profiles do not charge capacitance, ... I'm glad you agree. Profiles are maximum RMS envelope values and that is what EZNEC reports. [Standing wave phase] "doesn't rotate at all, and the resultant wave it represents doesn't progress through space - its a standing wave." I suggest you drop talking about phasors, till you understand what cos(wt). Hecht and I have been a little lose with words while assuming the readers have a certain knowledge level. For the uninitiated, When Hecht (or I) say the phasor doesn't rotate at all, we mean the phasor doesn't rotate at all with respect to the source phasor. Any initiated person would know that. The phase of the standing waves doesn't change with respect to the phase of the source signal. Hecht assumed you would know what he meant by that statement. Speaking of "... net transfer of energy, for the pure standing wave there is none." A standing wave does not violate conservation of energy. Exactly my point! Nothing violates conservation of energy. If the RMS forward current in the coil is the same magnitude at both ends and the RMS reflected current in the coil is the same at both ends, the conservation of energy principle is satisfied NO MATTER WHAT THE STANDING WAVE CURRENT TURNS OUT TO BE. What is it about that statement that you don't understand? Storage that must continuously be swapping back and forth from magnetic field energy to electric field energy. When the energy storage is all electric, that implies charges capacitance. Again, nobody has ever been discussing what happens within a partial cycle. Discussion of such is obviously a diversionary straw man. Feel free to find someone else willing to discuss it. It is completely irrelevant to this discussion of RMS envelope values. -- 73, Cecil http://www.qsl.net/w5dxp |
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