"Ian White, G3SEK" wrote
... the underlying principle is simply "The RX input takes
whatever it needs from a 50-ohm source, and reflects the rest."
______

The above statement might be read as though there is a threshold voltage
limit above which a receiver will not deliver improved performance.

A receiver amplifies and detects whatever voltage is present at its input
terminals, if just thermal noise. Even if no current flows in the input
stage device itself, the wanted signal voltage present there should be as
high as possible above the thermal noise voltage in order to maximise SNR.

RF