Once the signal is diminished (by inverse square law) to where it is below the background, it becomes undetectable no matter how advanced and sensitive the receiver technology is. Most terrestrial radio emissions quickly become too faint and impossible to detect after just a few light years.

The only possible exceptions are powerful, focused beams in extremely quiet and noiseless regions of the EM spectrum. For example: DEW line radars. Aimed towards the poles to detect Soviet ICBMs. These would sweep a small circle on the celestial sphere every 24 hours as the earth rotates. To an observer, intercepting one of these radars would appear much like the Wow! signal. But since everything in the galaxy is in constant motion the receiver would only be swept by the beam only once.