Understanding synthetic radio signals is unnecessary.
Detection of synthetic signals is sufficient to prove intelligence. And electromagnetic waves (light, radio, etc.) propagate at the speed of light, so Alpha Centauri is about four years away.
” propagate at the speed of light, so Alpha Centauri is about four years away.”
Alpha Centauri is a binary system. The chance of intelligent life is remote as planets would likely have a bizarre orbit. As a matter of fact all the closest stars are pretty poor candidates. The good candidates, according to the Hubble discoveries, are a lot further away. (That’s my reading on the data.) Also, the likelihood that we could get there or they could get here in anything like a probable lifetime is very remote. Even if, like turtles, they lived to be 500. And, why would they invest the money (or, whatever they have for an economy?)
Imagine we find porpoises are as intelligent as we are. What do we have to talk about? Perhaps they’d be annoyed by sonar or tuna nets. But beyond that we have nothing to say to each other.