John Smith wrote:
Checkout "Reference Data for Radio Engineers", Transmission lines, Mismatch
and Transducer losses. There are formulas there for this case. The
simplification ignores the mismatches at the Tx and Antenna to the line,
which causes about 4.43 dB additional "mismatch" loss, in the case of
50,450, 50. This shows up as VSWR.

There is little actual loss due to the "mismatch loss" since the
system is Z0-matched. Let's add a small length of 50 ohm line.

100W XMTR--50 ohm line---x---1/2WL 450 ohm line----50 ohm balanced load.

Since there are no reflections on the 50 ohm line, the system is Z0-matched
to 50 ohms at point x. (Assume a 9:1 balun at 'x') The 9:1 SWR on the 450 ohm
line causes very little loss and the "mismatch loss" is not really lost because
the forward power on the 450 ohm line is 278 watts, delivering virtually all of
the 100 watts of XMTR power to the load.

It can be illustrated that a steady-state destructive interference event toward
the source due to wave cancellation at point 'x' feeds energy to a constructive
interference event in the direction of the load. This has been understood in the
field of optics for many decades and is how non-glare glass works.
--
73, Cecil http://www.qsl.net/w5dxp



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