Re: It's a long way to the chemist, etc...
Humans have been emitting radio waves for about 100 years or so.
And we are emitting less and less every year with low power radios, satellites beaming down instead of stuff broadcast everywhere and more and more of what used to be broadcast being transmitted over fibre. In 100 years I doubt we'd be detectable at all.
Another problem is that the same frequencies are used all over the planet for different purposes which is no problem here but from a long way away they will all blur together into a random like noise where any single signal would be as close to impossible to isolate as makes no difference.
The only radio signal that would be detectable over many light years would have to be one broadcast specifically for that purpose and why would anybody do that?