Owen Duffy wrote:
Take an example of the 50 ohms load discussed, and an electrical half
wave of 70 ohm line connected to a transmitter designed for a 50 ohm
load. The transmitter behaves exactly as if that line were 50 ohms.
Though there is a reflected travelling wave on the line, it does not
travel back to the PA anode where it is absorbed and converted to
heat.

Of course not. Destructive interference redirects the energy
back toward the load at the impedance discontinuity. The same
thing happens with a 1/4WL thin-film on non-reflective glass.
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73, Cecil http://www.w5dxp.com