
July 10th 03, 04:43 PM
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wrote:
Assuming that P = V x I, the power is 0, always.
This seems to be at odds with explanation that SGCL#1's power is
dissipated in SGCL#2's circulator load resistor since there is no
energy flowing at the voltage maximum.
Nope, a directional coupler can still separate out the forward
and reflected waves even at voltage and current nulls. Remember,
those voltage and current nulls are only a 'dl' in length as 'l'
approaches zero. Superposition of two waves traveling in opposite
directions has no effect on the individual waves. There are no
reflections except at an impedance discontinuity point which
doesn't exist in the example.
Let's cut the coax at the voltage maximum (where the current is 0).
Nothing changes.
Of course something changes. You have introduced an impedance discontinuity
where none existed before. The forward wave is 100% reflected at
the cut point and of course, the reflected power is dissipated in
the source's circulator load resistor. If you make the two sources
one Hz different in frequency, you can easily observe what happens
when you cut the line. Otherwise, it's the old steady-state Catch-22
coverup in action. :-)
--
73, Cecil http://www.qsl.net/w5dxp
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