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Old January 28th 08, 12:45 PM posted to rec.radio.amateur.antenna
Keith Dysart[_2_] Keith Dysart[_2_] is offline
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First recorded activity by RadioBanter: May 2007
Posts: 492
Default Derivation of Reflection Coefficient vs SWR

On Jan 27, 10:26*am, Cecil Moore wrote:
Keith Dysart wrote:
When the generator is matched to the line so that
the reflected wave does not encounter an impedance
discontinuity when it arrives back at the generator
(and therefore is not reflected), ...


On the contrary, it is redistributed back toward
the load in the process of destructive interference
and becomes constructive interference associated
with the forward wave. Whether you call that a
reflection or not, the fact that the forward
power equals the source power plus the reflected
power tells us that reflected power being dissipated
in the source would violate the conservation of
energy principle.


Unfortunately, this is quite wrong. And I continue to
be surprised that you argue that there is a reflection
where there is not an impedance discontinuity.

Some parts of the rest of your post are correct by
coincidence, but since the underlying premise of
reflections where there is no discontinuity is
incorrect, I have snipped it.

But this debate has been had before. You do not want
to understand how the output impedance of a generator
affects a returning signal. I have offerred references
and you have refused to look. I have offerred spice
simulations, and you have refused to look. When the
discussion moves to simpler generators so that the
behaviour can be studied, you will declare them
uninteresting because they do not represent "real
ham transmitters". You will make jokes about 10 cent
resistors, not realizing that is how real test
equipment prevents re-reflection. (How well would
a TDR work, if any substantial amount of the return
was reflected?)

When you decide that you do not want to argue that
reflections occur where there is no impedance
discontinuity, and are willing to study output
immpedance, the learning can begin.

...Keith