On Mon, 17 Sep 2018 15:14:02 -0700 (PDT), RichA
wrote:

Radio signals radiate out in a spherical shell. Presuming (because we have no evidence either way) that advanced civilizations would have (if they formed like they did on Earth) started broadcasting 200-500 years ago, and given the number of stars in the vicinity, we'd have picked up something by now. We haven't.

https://www.cloudynights.com/article...-paradox-r3162

We wouldn't expect to be able to detect spherically radiated radio
signals, unless they were from the very nearest stars (and maybe not
even those). And there is little reason to think that alien species
would be broadcasting high power directed beams our way. Our failure
to detect anything tells us almost nothing (which is also the
conclusion of the referenced paper).