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Cecil,
It's a slow day, so I thought I might take some time to help you out of your dilemma. Q: Where are the missing joules? A: They are associated with the large standing wave supported by the mismatched terminations of your transmission line. As I have pointed out previously, standing waves are not inert. The shape of the wave does not travel down the line, but the fields are changing, and the charges are moving. Within each loop of the standing wave the stored energy simply oscillates between magnetic energy when the current is high and electrostatic energy when the voltage is high. Very basic stuff. The problem in your analysis is the initial axiom that RF waves always move. This is simply incorrect, and it leads to the dilemma you face. Traveling waves are fine if you do the math correctly, but the physical situation is in the form of a standing wave. The model results need to agree or there is a math error. And as many people have pointed out, always add the voltages and currents first and only consider power at the very end of the analysis. Since you are also an optics guru you might want to check into the details of laser cavity operation or Fabry-Perot etalon operation. These are highly mismatched systems with very strong standing wave components along with a little bit of net traveling wave. Definitely related to the problem you posed. 73, Gene W4SZ Cecil Moore wrote: [snip] After steady-state has been reached, the XMTR has output 300 more joules than the load has accepted. A smaller real-world experiment will easily verify that it is a fact that all energy sourced that has not reached the load must necessarily be confined to circulating energy or losses in the transmission line. Question: In the above example, where are those 300 joules of energy located and what is happening to them? We know that 300 joules is wave energy and RF waves always move at the speed of light, i.e. they cannot stand still. So please determine how much energy is moving and in which of only two possible directions. |
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