"AndyS" wrote in message
...
As a practical matter, if the background noise heard in the receiver
increases when the antenna is attached, the antenna is good enough.

This implies only that the antenna/receiver *matching* is good enough... yes?

(I'm thinking that you would still sometimes prefer a highly directional
antenna over just a dipole even though both increase the background noise.
I.e., in both cases the antenna matching is good enough, but without the
directionality the antenna itself might not be good enough to eliminate
interference, overloading, etc. from sources other than the one you're
interested in.)