[robonerd]

We know of one instance of a civilization broadcasting radio waves. But a Dyson Swarm has never been seen, it's purely speculative at this point. Uncertainty that Dyson Swarms ever exist changes the expected outcome of searching for them.

[analog31]

It's interesting that we're building a poor man's Dyson swarm of sorts. More and more of our communications are conducted along waveguides -- fiber optics -- that leak no signal. Remaining radio signals are being engineered to operate at lower power and be increasingly hard to distinguish from noise. And our long distance power transmission might switch to DC any day now. This took roughly a century from our first radio emanations, so the time frame for picking us up from a distance might be pretty short.

Another civilization might notice the IR signature of chemical changes to our atmosphere, as a clue that we're harboring intelligent life.

They probably assume that if we're smart, we're not going to try to communicate outside of our own solar system by radio. Even with a big enough antenna, radio signals eventually spread out and are governed by the inverse square law. We'd be better off sending out a matter-based container that remains intact along its journey, and can be programmed to engage in short-distance communications at its destination. Such a thing could also steer itself if it receives better information.