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Richard Fry wrote:
"Roy Lewallen" wrote The problem is that the idea of "reflected energy" turning the plates hot is so easy to understand, that people aren't willing to abandon it simply because it isn't true. _____________ But reflected energy/power does exist. For an easy example, such reflections are evident in the picture seen on an analog TV receiver when the match between the transmit antenna and the transmission connected to it is bad enough. In analog TV transmit systems with a typical 500+ foot length transmission line from the tx to the antenna, a 5% reflection from a far-end mismatch can be quite visible, showing as a "ghost" image that is offset from the main image as related to the round-trip propagation time of the transmission line. RF Richard, You are undoubtedly correct, but you have also demonstrated what is really the lifeblood of many arguments in RRAA. You have introduced both transient behavior and multi-frequency behavior. Clearly these are important in the real world. However, the vast majority of models and calculations used as support for RRAA postings are steady-state and monochromatic. Anyone who stayed awake through calculus and differential equations might recall that the equations for steady-state and transient behavior are often quite different. No one denies the existence of reflections. Some people get confused by the mathematics of power and voltage. But a big argument is about the round-trip travel of energy in the steady-state. Some people seem to believe that energy continues to flow back and forth from one end of a (mismatched) transmission line to the other under steady-state conditions, even simultaneously traveling in both directions. (Passing like ships in the night?) Since energy is a scalar quantity, and any given joule is not distinguishable from another, it is not clear how the proponents keep track of the bookkeeping, but they muddle through somehow. 73, Gene W4SZ |
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