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Old June 15th 10, 07:23 PM posted to rec.radio.amateur.antenna
Roy Lewallen Roy Lewallen is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 1,374
Default Where does it go? (mismatched power)

Richard Fry wrote:

If reflected power is fictitious, and the number wavelengths of
transmission line of any random impedance compared to the load
connected to it makes no difference in the load seen by the
transmitter, the output power produced by the transmitter, and the
power dissipated in the far-end termination, then what is the reason
you chose a 1/2 wavelength of transmission line in your quoted post?

RF


I chose that length so that the transmission line would have no effect
on the impedance seen by the transmitter. As I've said many times, and
you've continually disagreed with, increased dissipation and/or damage
at the transmitter is due to the impedance it sees, and not by
"reflected power". The example I gave keeps the transmitter load
impedance constant while changing the "reflected power". And it shows
that neither the transmitter nor the load see any changes in dissipation.

If I had chosen a different length line, then changing its Z0 would have
changed the impedance seen by the transmitter, which would have changed
its efficiency by an amount which could have been determined only with
additional knowledge about its characteristics. But replacing the
transmission line with a lumped impedance transforming network would
have exactly the same effect on the transmitter, again illustrating that
the only important factor is the impedance the transmitter sees and not
the "reflected power" in the line it's connected to.

This posting is being made, though, for the benefit of other readers.
I've explained this many times to you before with no noticeable effect
on your understanding.

Roy Lewallen, W7EL