[Suicide Junkie]

I just concluded that with a big enough radio antenna one could pick up the first transmissions from our system... and vice versa

Well, broadcasting does send a lot of waste signal into space.

If you want to be communicating over long distances, cheaper and with less interference for others doing the same thing, you start using fibreoptics, and narrow EM beams from satellites and cell towers directly to your customer, rather bLasting it out everywhere...

Propaganda and distress signals are about all you'd want for omnidirectional signals, which unfortunately get the 'ol 1/r^2 fading.