@futurebird maybe they explain this in the podcast but wouldn't that end up being a very narrow band of communication, e.g. just a straight line from the source of the supernova through wherever you are and continuing on in the opposite direction. Unless you are basically at the supernova and broadcasting in all directions away from the starting point, that would get a huge area of coverage.
@ReverendMoose @futurebird
It's a tradeoff: A smaller area covered but a higher chance of anyone there paying attention. It also gives you a focus for part of your future searching, (e.g. you actively watch each system for a decade after an immediate response could be arriving).