In article <3fce13fe$0$42893$c3e8da3@news.astraweb.com>,
JDLind@ix.netcom.com wrote:

Probably bigger, but it depends on how much power you put through it and how
far you want the signal to go. Degredation of the signal could be tremendous
inside the atmosphere (depending on conditions). Also, dark matter in space

That might be the case if it was raining, but most of the radio astronomy
and satellite broadcast calculations I've seen suggest that losses will
not be very great under normal conditions.

will reflect/absorb yet more power. Typically, for something like this, the

This is why the original posting should have been cross-posted and not
multiply posted, as sci.astro.seti has a regular who has written academic
papers on this.  However, my understanding is that the exponential
(absorbtion) component of signal loss is not particularly significant
within the galaxy, at typical radio astronomy frequencies.

signal should originate in orbit to bypass the atmosphere. Understandably,

Whilst there have been suggestions of putting radio astronomy receivers on
the far side of the moon, to block it from man made noise, there hasn't 
been much consideration of putting it outside the atmosphere.  It wouldn't
be of great benefit at SETI frequencies, although it would help at lower
frequencies.  It's generally much much cheaper to build a larger structure
on earth than to go into orbit.

Many people like what is referred to as "the Water Hole." (This is what SETI
searches).  It is between 1.3 -1.7 GHz (if i remember correctly. See

SETI searches from below 1 GHz to optical frequencies.  S@H is
1.42GHz +- 2.5MHz, but SERENDIP, on which it is based is more like
1.42Ghz +- 50MHz and Phoenix goes up to beyond 2GHz.  Berkeley also do
optical SETI.

There are also three deinitions of water hole:
- that between a lower bound set by galactic noise and a higher bound
  set by atmospheric *water* vapour;
- that between the hydrogen hyperfine line and significant hydroxyl lines
  at around 1.6GHz (H + OH = water);
- that in the immediate vicinity of the hydrogen hyperfine line (the
  animals all meet at the water hole).

I'd also point out that the proposed message content is exactly the
sort of message the UN conventions are designed to prevent being sent.
In practice, though, you would need a very long message to send it, as
you would have to introduce a lot of vocabulary first.  It would also
be illegal for amateur radio operators, probably world wide.