Not OP, but “close enough radius” alludes to the fact that earths current radio output would only be detectable in a radius some hundreds of light years away (signal would become too weak past that). And I’m pretty sure our radio signal output is now decreasing in energy. So it becomes increasingly less likely with distance that a radio source would exist that we could currently detect. But I guess this study states that it could detect a theoretical “beacon” that is intentionally incredibly powerful.