[eridius]

SETI isn't just looking for spacefaring civilizations. It's looking for any form of intelligent life. Take us, for example. We've been broadcasting radio signals into space for many years now (basically as a side-effect of broadcasting them to ourselves). Given sufficient time for the radio waves to travel, an alien equivalent of SETI would be expected to recognize them as non-natural.

[0xffff2]

That's not really true (for better or worse). Radio signals attenuate with distance. In the case of omnidirectional signals expanding in a sphere, they attenuate at a rate of 1/r^3. As a result, virtually all of our radio signals intended for terrestrial consumption are basically noise before they even leave the solar system.

[eridius]

The wikipedia page on Path Loss[1] suggests that radio and antenna engineers typically model path loss (in decibels) using the formula

  L = 20 * log10(4 * pi * d / λ)

(where λ is the wavelength and d is the distance between the transmitter and receiver expressed in the same units as the wavelength)

If I'm doing the math right[2], this says that the path loss over 1 lightyear for an 80MHz transmission (which seems to be in the analog TV range?) is something like 330 decibels. Now I'm not sure how strong TV transmissions are, but I'm guessing it's not that strong.

Darn. Seems Futurama and every other piece of mass media that claims that aliens are watching our TV from 80 years ago is wrong.

[1]: https://en.wikipedia.org/wiki/Path_loss

[2] Which is to say, if I'm typing it into Wolfram Alpha correctly.