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I had this example at the bottom of my posting but you seem to ignore such. So I am moving it to the top of the posting. If you ignore it now, at least everyone will know you couldn't possibly have missed it. You are in a room with a 50 ohm transmission line routed through a hole in one side of the room, across the room, and through a hole in the other side of the room. You don't know which is the source end of the line. A directional wattmeter reads 200 watts forward power and 200 watts reflected power but you don't know which direction is forward. Here's a diagram: 200W-- 2 amps-- hole-------------------50 ohm coax-------------------hole --200W --2 amps Which direction is the standing wave current flowing? If you knew forward current was moving left to right which direction would the standing wave current be flowing? That's not true at all Dave. Most of us know that current is current. Too bad EZNEC disagrees with you as seen in the graphic at: http://www.qsl.net/w5dxp/travstnd.GIF The traveling wave current is virtually the opposite of the standing wave current as can be seen by their different equations. There is no phase information in the standing wave current phase. Yet that is exactly the phase W7EL used to try to measure the delay/phase shift through a coil. DC current is different from AC current. That's why the DC or AC designations are necessary. RF forward current is different from RF standing wave current. That's why the different designations are necessary. It really only flows one direction at any instant of time. Or not at all at a standing wave current node. Too bad we are talking RMS values here which is what EZNEC reports. I'll ask the question of you: If one amp of RF current is flowing in one direction and one amp of RF current is flowing in the opposite direction, which direction does the phasor sum of those two currents flow? We can indeed consider systems as having current that flows two directions at one instant of time, but the results of that better agree with the actual real current that flows only in one direction at any instant of time or they are wrong. The phase of standing wave current is unchanging. It doesn't "flow" in the commonly accepted sense of the word. As Hecht says in "Optics": "This is the equation for a STANDING or STATIONARY WAVE, as opposed to a traveling wave. Its profile does not move through space; it is clearly not of the form Func(x +/- vt)." [Standing wave phase] "doesn't rotate at all, and the resultant wave it represents doesn't progress through space - its a standing wave." If standing wave light doesn't move through space, then standing wave RF also doesn't move through a wire. (I assume we all know current ... does not "drop", ...) EM current does indeed drop exactly like EM voltage drops both according to the attenuation factor. Just one more proof that EM waves are not lumped circuit currents. The only difference in the equation for transmission line voltage and current is the voltage gets divided by the characteristic impedance which is usually a resistive constant. I think the basic problem is Cecil wants to used some definition of current that does not allow models to be freely exchanged and does not produce results that match real world systems. It always has to match. We can't have different results unless someone has an error. Exactly correct and the reason for the different results is your error. In any conflict between the distributed network model and the lumped circuit model, the distributed network model wins every time since it is a superset of the lumped circuit model. This has gone on for perhaps three years now. It is really up to Cecil and Yuri to let it go, since they are the ones who seem to disagree with measurements and accepted theory. On the contrary, it is up to you and others to correct your misconceptions about standing wave current. Your "accepted theory" has holes in it that I could drive my GMC pickup through. -- 73, Cecil http://www.qsl.net/w5dxp |
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