On Tue, 29 Aug 2006 19:50:53 +0100, david@djwhome.demon.co.uk (David
Woolley) wrote:

right on by, stopping only when it hits something. No it is not fast
but it is going. Think HBO, ESPN, CNN, etc.

Modern broadcast satellite TV has very little redundancy, which means it
requires a similar order of magnitude of sensitivity to detect it as it
does to make use of the signal, so the ETI would need antennas that are
of the same order of magnitude of effective diameter (one can go smaller,
because one can integrate the power in the whole bandwidth, over a period,
of time, but the large bandwidth also reduces the ability to reject
natural sources) as one would get by scaling the satellite's antenna by
the ratio of however many light years to just over 0.1 light seconds.

The other problem is that the uplink beam is swept with the earth's
rotation, so will only be on target for a few seconds a day.

Basically, leaked digital TV uplinks make rather poor SETI beacons.

I totally agree with the last part, I have no idea what you are
talking about regarding the antenna size. But my point was that we are
broadcasting something, which is better than nothing, but not by very
much!