[sliken]

Voyager 1 uses 22 watts and 1970s technology to communicate from 21 light hours away.

Radio encoding has come a long way since then. In particular ft8/js8call uses an encoding that can communicate at over 20 db below the noise floor, allowing communications across the earth with a few watts which involves many 1000s of miles of atmosphere, bouncing (poorly) off the upper atmosphere and the ground many times.

If we launched one an hour at 5% of C (better than today, but much worse than the goals of the project) they would only have to communicate across hops of 3 light minutes, er about half that since 5% of C is the final velocity not the average. Considering voyagers success at 21 light hours and the improvements in encoding that sounds quite feasible.