Jim Brown K9YC <k9yc@audiosystemsgroup.com> wrote :
> No, the input impedance is NOT irrelevant -- it loads the generator and
> reduces the voltage at the receiver input.
Of course it loads the generator, but nevertheless there is a good reason
why RF noise and sensitivity measurements depend on the "available power"
and not on the "delivered power".
It's common for RF circuits to achieve the best noise figure (i.e. the best
sensitivity) when the input is NOT matched to the generator. That is,
given a fixed amount of the "available power" from the generator, the RF input
is allowed to have arbitrary mismatch (and thus to "consume" only a part of the
"available power") in order to achieve the best possible noise figure.
73,
Sinisa YT1NT, VE3EA
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