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From: Fractenna@aol.com
Return-path: <Fractenna@aol.com>
To: seti@sni.net
Subject: Fwd: SETI Re: Are lasers any good?
Date: Wed, 3 Feb 1999 12:59:45 EST
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From: Fractenna@aol.com
Return-path: <Fractenna@aol.com>
To: seti@sni.net
Subject: Fwd: SETI Re: Are lasers any good?
Date: Wed, 3 Feb 1999 11:52:13 EST
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From: Fractenna@aol.com
Return-path: <Fractenna@aol.com>
To: seti@sni.net
Subject: Re: SETI Re: Are lasers any good?
Date: Wed, 3 Feb 1999 10:41:46 EST
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In a message dated 2/3/99 10:18:51 AM Eastern Standard Time, Fractenna writes:
<< > It was because the uplink assumptions were so poor in the Cyclops Report
>that OSETI has been held back for a quarter of a century.
>
> So in actual fact, the laser approach is far superior Of course, if
>it is easier (for an ETI) to generate very large laser powers, the FOM on a
>non-watt for watt basis might be even higher.
>
> Have a look at my diagrams which indicate a 14 dB improvement of a
>symmetrical 10 meter 656 nm link over a symmetrical 300 meter 1.5 GHz link:
>>
Of course, the fun issue is as follows: for a given beam angle which has a
higher FOM? Stuart's 10M dish or the 300M microwave one?
OK, gain goes as wavelength to -2 power; angle as wavelength. Now to get the
same angle for the laser-- and thus 'scoop' up the same region of the sky for
ET's-- I have to make a much smaller mirror; one that's 10,000 times smaller!
It's gain is thus 100,000,000 times less than the 300M dish! It thus is down
80-14 dB= -66dB from the radio. Uh oh!
Thus , even JUST froma gain standpoint, the laser is a contrived situation
which only works when the target is a very small (individual star) angle;
point to point.
Chip
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