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Old June 16th 10, 07:48 AM posted to rec.radio.amateur.antenna
Owen Duffy Owen Duffy is offline
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First recorded activity by RadioBanter: Dec 2006
Posts: 1,169
Default Where does it go? (mismatched power)

lu6etj wrote in
:

....
For not to work too much, calculations could be reduced to three
resistive Zls, and three lengths of TL. Let me suggest 25, 50 and 100
ohms RLs and 0.5, 0.25 and 0.125 of lambda (to honor Cecil and Roy
papers), Vg voltage = 100 V RMS, Rs 50 ohms, Zo obviously 50 ohms too
(lossless line). Zl=50 ohms and 1/2 lambda TL are for beginners, as
me ;D


Miguel, I gave an expression for power in your simple source circuit in a
recent post, did you see it. Well here it is again:

Prs=(Vs/2-Vr)^2/Rs where Vs is the o/c source voltage, Vr is the complex
reflected wave voltage equivalent, Rs is the source resistance.

If the reflected wave was always, and entirely dissipated in Rs in that
type of source, then Prs=Vr^2/Zo=Vr^2/Rs... but it isn't, see the above
expression.

You can work one case, three cases, three x three cases, but they are not
as complete as the expression above that shows that in the steady state,
Prs is not simply equal to the 'reflected power'.

But if you want, work the cases and report the results here, it is a
trivial exercise. You will accept the results more readily if you work it
our yourself.

Owen