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Old March 14th 07, 02:58 PM posted to rec.radio.amateur.antenna
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Posts: 572
Default VSWR doesn't matter?

On Mar 14, 6:53 am, Roy Lewallen wrote:
So any explanation of the effects (such as the red plates
of the mismatched transmitter posed earlier) has to be made without
resorting to the bouncing energy.


That's simply not true. When the load is connected directly to the
source, incident power is often still rejected, it just doesn't
have very far to "bounce". And since it is internal to the source, the
"bouncing" is difficult if not impossible to quantitize.

If you hang a purly reactive load on a source output, it rejects all
the the incident power just like it does at the end of a one-
wavelength long transmission line. If we leave the source output
terminals open, i.e. an infinite impedance, all of the source power is
rejected at the source output terminal, i.e. there is a standing wave
on the internal wire (often coax) connected to the source connector.

In the same way that a source doesn't know whether it is connected to
a transmission line or a lumped circuit, a purely reactive load
doesn't know whether it is connected to a source or to a transmission
line. Either way, it does an immediate rejection of incident power.
Whether the load is connected to a transmission line or directly to a
source, the reflection at the load is a same-cycle reflection. Since
it happens at the load with a transmission line, why are you surprised
that it happens at the load with a source?
--
73, Cecil, w5dxp.com

 
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