On 19-8-2017 12:38, Cursitor Doom wrote:
On Sat, 19 Aug 2017 07:21:33 +0000, gregz wrote:

It's hard enough to communicate with Voyager when two dishes converge.
Horizontally omni broadcast has low energy and complex signals. Forget
it.

Greg

I'd always suspected so. But is there any respectable research to back up
this figure of 1.5 light years?





We know the signal strength (inverse square law), and we
know a lot about noise received from space.
When the noise is drowning the signal, you cannot receive the signal.
So, yes, we know the reception quality for a given transmitter power
and distance.
To reach twice as far you need 4 times as much power, and as distance
increases, you quickly lose that game.