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Keith Dysart wrote:
To me it was a complete surprise that summing the voltages produces the correct total voltages and, at the same time, summing the powers (which are a squared function of the voltage) also produce the correct result. Why is that a surprise to you? I have been telling you for many days about that special case whe (V1^2 + V2^2) = (V1 + V2)^2 for zero interference This applies equally well to phasors or instantaneous values of voltage. The above special case is what my Part 1 article is all about. Since a 45 degree long transmission line forces the above RMS voltage equation to be true for all values of resistive loads, the *average* reflected power based on RMS voltage values is *always* dissipated in the source resistor. Since a conservation of power principle does not exist, it is perfectly acceptable for destructive interference energy to be stored for part of the cycle and be dissipated later in the cycle. So Pg(t) = Pf.g(t) + Pr.g(t) is always true. Of course it is true but it says absolutely nothing about the dissipation of the reflected power in the source resistor which is the subject of the discussion. The above equation remains always true while the dissipation of the reflected power in the source resistor varies from 0% to 100%. -- 73, Cecil http://www.w5dxp.com |
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