"l" == lin8080  <lin8080@freenet.de> writes:

l> Joann Evans schrieb:

Strong, very directional radio waves are easy to generate, and some
parts of the spectrum (do a search on "SETI"+"water hole") are
usefully quiet.

It's my understanding that the Aricebo readitelescope could
communicate with another device like itself on the other side of
the galaxy. If we had the will, we could build something even
bigger/higher gain in free-fall and/or on the Lunar farside. ETs
that have radio at all, likely could do even better.

l> [...]

l> Why not searching in a duple water-frequency? Is there ever a
l> search or a look at 2,8xx Ghz?

You mean like Horowitz & Sagan (1993, <URL:
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993ApJ...415..218H 

)?  They searched "for narrow-band radio signals near the 1420 MHz

line of neutral hydrogen, and its second harmonic" (which is 2840 MHz).

l> Or, wouldn't it be more intelligent to use math. oriented freqs?
l> May be 3,14.., named PI, or e, or phys. constants. It is not known
l> to me, ever heard about such things.

There are a host of suggestions of "magic frequencies."  Mike Williams
has already pointed out a number of these.  Others include near the
peak of the cosmic microwave background and at frequencies related to
emissions from carbon (given its possible importance in life).

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