And another example in point:

From the input to a TV transmit antenna system, tx disconnected, I have
personally measured the far-end antenna system reflections of a 2T sin²
video pulse (0.25 µs H.A.D.) modulated onto a TV channel carrier, and
detected by a vestigial sideband demodulator tuned to that TV channel. A
high-directivity directional coupler at the input to the main line, a
display device, calibrated attenuators, and the time difference between the
incident and reflected pulse enable accurate measurement of the reflection
coefficient of the antenna system.

This was a common practice after a new antenna system installation to
measure and optimize the far-end match for the best quality radiated signal,
and was pioneered by RCA Broadcast Eqpt Div, my employer at the time. More
elegant means are used these days.

When this test shows a 5% pulse return 2 µs after the incident pulse time
(for example), then the same pulse passed through the tx also shows nearly
exactly the same reflection % and time separation -- assuming there is
enough RF delay in the system for the reflection to be resolved in the
demodulated waveform.

As the directional coupler driving the normal demodulator at the TV station
is looking at forward power only, it is clear that the reflection from the
far end of the antenna system has been re-reflected from the TV tx output
stage, and NOT absorbed by it in its "conjugate impedance."

RF