In article <38ce8436-d2a2-44c1-906f-3b1893b6bc48@googlegroups.com>,
 ab1jx <alan01346@gmail.com> wrote:

<snip>

If we're looking for spillover from other planets' normal daily 
communications, I think its useful to look at how we started: spark gap 
transmitters, wavelengths of 200 meters and more. We've only had the ability 
to get above 1 GHz for about half our radio history of 100 years or so. 

I'm pretty sure most varieties of SETI are looking for a beacon or 
similar: a signal that's intended to be detected. The "water hole" is 
thought of as a sort of landmark in the RF landscape. Leaking 
transmissions are unlikely to be detectable over any great range, and as 
you suggest are likely to come from a fairly short period of a 
civilization's development. Choice of frequencies aside, compressed 
digital transmissions are extremely difficult to distinguish from noise 
-- and if we're at all representative, our analogue-signal era won't be 
much longer than a century either.

-- 
Odysseus