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On May 16, 6:03*am, Wimpie wrote:
I am not ignoring a problem (as you suggested), I am just using the right tool to solve a problem. I'm sorry, Wim, that is just not true. When you convert a V/I ratio to a lumped circuit impedance, you are switching models in mid-example and it changes everything in one direction (while keeping conditions the same in the other direction). Switching to a model that doesn't recognize reflections at all when a question about reflections arises is an obvious logical diversion. The lumped-circuit model does not recognize reflected energy and therefore does not allow the tracking of reflected energy. The distributed network/wave reflection model does allow for the tracking of reflected energy and was developed because of the limitations of the lumped circuit model. I will buy your assertion that one can use voltage and current to achieve the same thing if one is careful not to violate the known laws of EM wave physics. In my example, the reflected power on the 100 ohm line is 12.5 watts. The reflected voltage is 35.35 volts. The reflected current is 0.3535. The reflected voltage and reflected current are 180 degrees out of phase so the power is real, i.e. cos(180)=1.0, and the reflected wave has a Poynting vector magnitude of 12.5 watts (per coax cross-sectional area). In my very simple example, there is no reflected power on the 50 ohm feedline yet there is (35.35)(0.3535)=12.5 watts of reflected power from the load incident upon the 100/50 ohm impedance discontinuity. I ask you again: Exactly what phenomenon of EM wave physics causes the reflected wave to *reverse* its momentum and direction of energy flow when the magnitude of the reflection coefficient is 0.3333? As long as you refuse to answer this simple question about such a simple example, this discussion will go nowhere. Cecil, I think you have sufficient knowledge to form an opinion without hiding behind others. You also have the equipment to figure out some things yourself, and I gave some hints to help you. *The only question is, are you willing to do this? If you cannot answer the simple question about what happens to the reflected energy at a simple passive impedance discontinuity, I am not about to trust your assertions about what happens inside an active source. Trying to introduce a more complicated example while refusing to deal with the very simple example that I provided is an obvious and typical logical diversion. Again, I am not going to cooperate in your attempts at diversions. If you don't know why reflected energy reverses momentum and direction at a passive Z0-match, just say so. Here's an easier example: Two EM waves superpose in a Z0=100 ohm environment. Each wave is 100 volts at 1 amp = 100 watts. The phase angle on wave1 is +60 degrees and the phase angle on wave2 is -60 degrees. The superposition results in a new wave of 100 volts at 1 amp = 100 watts with a phase angle of zero degrees. We superposed two 100 watt waves and the result was one 100 watt wave. What happened to the other 100 watts? -- 73, Cecil, w5dxp.com "Halitosis is better than no breath at all.", Don, KE6AJH/SK |
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