Re: Transmitting our signal

Wasn't it Rob Dekker who wrote:
>
><carsten_niel@xxxxxxxxxxx> wrote in message news:1135596945.844680.188950@g43g20
>00cwa.googlegroups.com...
>> How about the radar signals from Areceibo, aimed at asteroids ?
>>
>> Regards
>>
>> Carsten Nielsen
>> Denmark
>>
>
>Happy Holidays !
>
>The Seti FAQ mentions that indeed Arecibo (and other) asteroid and
>interplanetary radar signals
>are (in terms of EIRP) among the strongest radio signals ever sent out by
>humans.
>Also, half of the time planetary radar uses CW signals, which means that they
>are
>not just powerfull, but also concentrated in an extremely narrow bandwidth
>(makes detection a lot easier)
>They can be detected by a technology like ours at 100's or even 1000's of LY
>away.
>
>Downside of these transmissions is that they are very highly aimed at the radar
>target asteroid/planet,
>which leaves most of the Galaxy outside their beam at any point in time.
>Second 'problem' is that they transmit very infrequently, and thus signals will
>not repeat
>from any extra-terrestial receiver point of view.
>
>Still, if we receive a weak drifting (due to Doppler) CW signal from the
>direction of a star
>within 1000 LYs or so, it might be an ET planetary radar. Unfortunately, since
>it probably does not
>repeat, we have no way of confirming or ruling out that theory.
>ETIs listening to our transmissions might be in the same situation as we are in
>that respect...

I believe that the situation for planetary radar might be a little worse
than that. The radar beams sweep to follow the path of the planet, so
any detector at another star will only see a single spike as the beam
sweeps past their location. If their situation is anything like ours,
they'll be detecting huge numbers of one-off spikes.

Even if ET has technology that allows them to examine one-off spikes in
much greater detail than we can, there's nothing obvious about the spike
that will identify it as being of artificial origin.

--
Mike Williams
Gentleman of Leisure
.

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