It seems to me that the choice of monitoring frequencies assumes that a civilization would be transmitting to space for the purpose of announcing their presence. Following this logic, our high powered general communications broadcasts from the past would have never been heard by another civilization. Where am I wrong?

Our very limited search capabilities force us to concentrate our search upon a number of assumptions. The main assumption is that any extra-terrestrial intelligence is deliberately sending out some signal to be heard.

Hence, we are searching in a range of frequencies commonly known as the "water hole", colloquially named after how animals gather around a watering hole in a desert.

See my profile graphic for further details.


Keep searchin',
Martin

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See new freedom: Mageia Linux
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Thank you for the reply. I am familiar with the spectra shown in the graphic. Are we broadcasting into space announcing our presence?

If so, there are those who would question our intelligence. :)

I do understand your reply. I just think the odds for success are greater when searching for practical general communications.

Thank you,

Jim

Thank you for the reply. I am familiar with the spectra shown in the graphic. Are we broadcasting into space announcing our presence?

If so, there are those who would question our intelligence. :)

I do understand your reply. I just think the odds for success are greater when searching for practical general communications.

Thank you,

Jim

Understand your thought process, but at present even our best antenna and receiver isn't sensitive enough to pick up regular signals from more than a wading pool size area of our galaxy. The wide band nature of communications signals causes huge signal losses. Also we humans pollute the radio spectrum at those frequencies making it impossible to pick an ET signal out.

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Thank you for the reply. I am familiar with the spectra shown in the graphic. Are we broadcasting into space announcing our presence?

If so, there are those who would question our intelligence. :)

I do understand your reply. I just think the odds for success are greater when searching for practical general communications.

Thank you,

Jim

No signals from us have the power to even get to the nearest star, currently.

Those signals, regardless of power, continue forever. A signal at 10 light years away is 6db weaker than it is at 5 light years away. Narrow-band signals such as CW are obviously easier to identify. Terrestrial receivers would have a tough time. Space based receivers would be required for such a task.

Those signals, regardless of power, continue forever

But once their power is below int intersteller noise level, the signal is lost.

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No signals from us have the power to even get to the nearest star, currently.

Oooer... Not sure about that...

That might be true for such as terrestrial TV signals and the weaker stuff. However, we also have phenomenally more powerful interplanetary radar (Arecibo and Goldstone for example) and various chirpy military radars that pack a significant electromagnetic punch.

On another much lower frequency, I wonder how far the ionosphere sounding transmissions might reach for their high powers and long transmit times...


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)