I'm not sure I accept this argument. Its true, we've been broadcasting radio and microwaves into the Galaxy for about a century now, but the speed of light suggests we've not really made our presence known very effectively. Some of our signals, like Dew Line radar emissions, may be audible over the noise a hundred years out or so, but I suspect ET won't be exposed to Desi and Lucy or the Honeymooners, even if they were able to decode our TV scans. Up to a hundred light years, not only is there
unlikely to be an audience, the signal will be too weak to stand out above the static, no matter how sensitive ET's receivers are.

Some of our deliberate transmissions, broadcast on tight beams from big radio telescopes, have the potential to be picked up hundreds, even thousands of light years away. But it is highly unlikely there will be an alien civilization listening when our signal flashes by. Its not so much a question of technology as it is one of dumb luck.