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Re: Oscar 0



If that is possible, it would not require a very large aantenna to hear it
back on earth.  A gain of about 113 dB will get it to a level where CW will
be possible under good sky conditions.

Scott
AC3A
-----Original Message-----
From: Jim Walls <k6ccc@earthlink.net>
To: amsat-bb@amsat.org <amsat-bb@amsat.org>
Cc: Scott E. Olitsky <solitsky@acsu.buffalo.edu>
Date: Friday, June 23, 2000 8:02 PM
Subject: Re: [amsat-bb] Oscar 0


>"Scott E. Olitsky" wrote (in part):
>
>> Bob did raise a good point which I had neglected.
>>
>>  Although the moon is a very poor reflector, it does capture a large
amount
>> of the signal as it spreads out from earth.  The moon's diameter is about
>> 3475 km.  If you assume a 100% "reflection" from the transponder with a
dish
>> antenna with a surface area of 2m instead of the moon's diameter, the
>> pathloss would  be about -365 dB, much greater than the EME pathloss at
144
>> mhz.  The improvement in reflection adds about 11dB of gain but the
decrease
>> in size adds about 124 dB of loss from the equations that I have seen.
>> Obviously the transponder would have to amplify the signal as well.
>
>No kidding!  I don't know where several people discussing this have gotten
the
>idea that a transponder on the moon would have "100% reflection" (or zero
gain -
>or loss) through it.  I don't really know what the OSCAR satellites have
for
>gain, but any active repeater has gain - LOTS OF IT!  I did grab out my
1994
>ARRL handbook which has a fairly decent set of numbers for calculating link
>budgets for OSCAR-13, and it comes out to just over 150dB (that's not a
typo -
>that One Hundred Fifty dB) of gain through the transponder.  It is
reasonable to
>assume that a transponder on the moon could have somewhere around that much
as
>well.  Due to the path losses, I would not ever expect to be able to have
>handheld coverage using a transponder on the moon, but it should not be all
that
>difficult to get it within the reach of a high end AO-10 class station.
>
>73
>-----------------------
>Jim Walls - K6CCC
>k6ccc@amsat.org
>http://home.earthlink.net/~k6ccc/
>626-302-8515    FAX  626-302-9999
>
>

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