Andrew Nowicki <andrew@nospam.com> wrote in 
news:4093D8E7.18486E80@nospam.com:

Andrew Nowicki wrote:

If the ET lives near a sun-like star and beams to us 1 watt
of microwave signals, his star makes so much microwave noise
that we cannot read the signal unless one beep lasts at least
10^10 seconds (about 300 years).

I have assumed non-directional transmitter (It radiates
microwaves in all directions.) A directional transmitter
has much better energy density and signal-to-noise ratio,
but it may be aimed in a wrong direction at a wrong time.
The latest Scientific American article about the microwave
SETI ends with a pessimistic statement -- interstellar
distances are too vast for this kind of communication.

You refute the previous poster's argument that a focussed transmission of 1 
watt would be sufficient, by counter-arguing that an omnidirectional 1 watt 
system is not good enough?

Are you malicious, or just plain stupid?

For you information, a 1 watt, systemwide-focused, monochromatic 
transmission will outshine the sun at anything more than about half a 
lightyear. At 100 lightyears distance, that 1 watt will outshine the sun's 
radiation at the same frequency by 5 magnitudes! The only real limit 
applicable here is how well they can focus the transmission, and this is 
directly related to how big they are willing to make the transmitter. A 
reasonably advanced civilisation using a solar-system scale transmitter 
(easily done witha few dozen coordinated emitters) can achieve solarsystem-
scale focus up to some 50 000 ly.

Do yourself a favour, and read up some about the subject before you start 
spouting bull again.