How much power would such a device need to be detected above background radiation? Would a power source for it last long enough to improve the odds significantly?
It need not be active to send a message. If you build a giant diamond cube or some other gigastructure, it could last for billions (?) of years even after the builders have become extinct. You need it to be detectable at interstellar distances, but the message is simply "we were here once." Maybe you could encode your civilization's knowledge on the gigastructure itself for visitors.