Hi Robert,

Your reasoning is very valid, and has come up many times in the past (here on alt.sci.seti and on sci.astro.seti).
There were even some aritcles in the press essentially stating that "Earth is vanishing from the ET radar".
Here is some reference to that :
http://www.newscientist.com/article.ns?id=dn6255

Not only do we use more 'cable' than radio for communication, we also are shifting from
the much easier detectable analog TV carriers to digital communications, which carry
much less 'density' in narrow bandwidths; the info is better spread out.
Essentially, we are getting better in using the radio spectrum.

Another trend is that IF we use the radio spectrum, that we use more accurate point-to-point transmissions
than wide area 'broadcasting'.

All these seem to underline that a more advanced civilization will be more efficient in their
use of the microwave spectrum, which seems an obvious thing to do for an 'intelligent' civilisation.

A couple of positive points (my interpretation) :

Apart from TV analog carriers, much of the terrestial and satelite communication would not
be detectable at interstellar distances, regardless of the mode of modulation.
At least not with antenna's smaller than the size of countries..
So we are not 'loosing' that much just yet.

The applications that ARE detectable at interstellar distances are things like planetary radar,
high-power military radar (if not in 'stealth' encryption mode) and possibly weather radar.
And these are things that any intelligent civilization could continue to use for a long time to come.
At least as long as there are comets and asteroids and other debrit flying through the host stellar system,
and as long as there is war and weather...
On top of that, there might be certain applications of which we can only dream, that might require
very high power EM transmissions. As long as there is power and intelligent life, there will probably
be a use for high-power EM transmissions.

Downside is that we currently do not listen for this sort of (unintended, radar) signals.
Almost all SETI programs listen (or look) for deliberately transmitted signals, from some sort of ET beacon.
All signals that are transient (do not repeat easily) or seem to be drifting 'too fast' are discarded as noise.
We are just beginning with this (ETI searching).
The only thing we have evidence for now is that there does not seem to be an extremely powerfull beacon in the Galaxy,
at least not transmitting continuously in narrow bandwidth around 1420 MHz.
But there is plenty of other stuff that we have not even scratched the surface on.

My 2 cts

Rob

"Robert Harris" <reharris1@yahoo.com> wrote in message news:43f808e0.8100812@news20.forteinc.com...

Please excuse me if this question has been discussed before, but I am
new to this group.

Undoubtedly, the most frustrating part of the SETI program to most of
us is its failure to detect any form of intelligence. What I am
wondering is, if the reason for the apparent lack of intelligent
signals might have more to do with the nature of alien communications
than with a shortage of intelligent species.

If other civilizations progressed at all like we did, then they would
have gone through an extremely brief period in which signals were
openly broadcast that could be picked up from great distances.

I don't think there is much doubt, that by the end of this century,
our own broadcast television and radio will be a thing of the past.
Already, we can get a much larger and better selection of radio
stations on the Internet, and television isn't far behind.

But the internet is a combination of cables, tightly beamed laser
signals, and very short range wifi. Correct me if I'm wrong, but none
of our Internet communications could never be heard in other solar
systems, will they?

So, why would we expect alien civilizations to use such primitive and
inefficient technology? If like us, they only used open broadcasting
for about a century, then the odds of us hearing them during such a
tiny window, are astronomically small.




Robert Harris
The JFK History Page
http://jfkhistory.com/