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On Jun 15, 1:36*pm, Roy Lewallen wrote:
For all the fluff about photons, optics, non-dissipative sources, and the like, I have yet to see an equation that relates the dissipation in the resistance in one of those painfully simple circuits to the "reflected power" in the transmission line it's connected to. The power density equation containing an interference term is what you need to use and I seriously doubt that, after 5+ years, you are ignorant of that equation. In your food-for-thought, forward/reflected power example, all you have to do is figure out the power in the forward wave and the power in the reflected wave at the source resistor and plug them into the following equation: Ptot = P1 + P2 + 2*SQRT(P1*P2)*cos(A) where 'A' is the angle between the forward voltage and reflected voltage. For instance, if the reflected voltage arrives back at the source resistor in phase with the forward voltage, cos(A) = cos(0) = 1 and there is constructive interference which increases the dissipation in the source resistor. If the reflected voltage arrives back at the source resistor 180 degrees out of phase with the forward voltage, cos(A) = cos(180) = -1 and there is destructive interference which decreases the dissipation in the source resistor. If the reflected voltage arrives back at the source resistor 90 degrees out of phase, cos(A) = cos(90) = 0, and there is no interference and all of the reflected power is dissipated in the source resistor. If you had ever read my energy article, published many years ago, you would know what effect superposition accompanied by interference can have on the redistribution of energy. But you instead said, "Gobbleygook" (sic) and plonked me. Time to pull your head out of the sand. The above power density equation not only agrees with all of your power calculations, it tells anyone who desires to acquire the knowledge, exactly where the reflected energy goes and why it is not always dissipated in the source resistor. -- 73, Cecil, w5dxp.com |
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