Comment Beacon (Score 2) 95
It's worth pointing out that a good way to send a signal would be to have a bright but transient beacon, which doesn't itself transmit information (other than "here I am"), but serves to tell others where to point their high-gain radiotelescopes.
This could be what such a beacon would look like.
Not to mention the power output it would need to send a detectible signal from another galaxy.
From the summary: "bright flashes of radio waves that last only a few thousandths of a second.
A high power for a few milliseconds may not take an enormous amount of energy.