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Old February 27th 07, 08:53 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 158
Default tuner - feedline - antenna question ?

Please don't insult our intelligence. If the Bird reads

Of course it is nonsense, but it is a logical development based on Jeff's
words "What you are describing could be called 'transmitted' power or
power delivered into a mismatched load, but that it different from
forward power, or the power delivered by the source" and your words "For
systems



Only a logical development if you selectively snip Owen.

"What you are describing could be called 'transmitted' power or
power delivered into a mismatched load" was referring to "Pload = Pfor -
Pref".

Ok I admit that 'transmitted' power could have been better phrased.

Power may not actually be dissipated in a lossless line but that does not
detract from the fact that there is current flow and a voltage along the
line produced by two distinct and independent waves travelling in opposite
directions. True that the power can only be realised when it encounters a
load, but it is highly pedantic not to regard the reflected signal as having
'power' until it actually encounters such a load. If you extend this theory
to a radiated signal, you could equally say that there is no power
travelling through the aether until it encounters a receiver.

It is naive to believe that reflected power is not dissipated in a matched
source, or partially re-reflected at the source/line interface is not
matched. Again going back to the optics corollary you would not expect a
reflected light signal not to impinge on, and interact with a source.

If you pad out a source with a sufficiently high attenuator such that the
reflected signal will not have significant effect on it, you will see an
increase in dissipation in the attenuators when the load is mis-matched. I
am confident that an attenuator is not having its "load line" changed such
that its dissipation goes up magically just by the same amount as the power
in the reflected wave!! (Of course the dissipation in the load is measurable
as heat).

Adding a circulator to a system will not change "the load line" (if a
transmission line or circulator can have such a thing), but it will cause
the power in the reflected wave to be separated so that it can be monitored
and measured. Surprisingly power monitored in this way ties up with the
notion that power is reflected at a mis-matched load.

73
Jeff



 
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