[amsat-bb] Re: Turn off AGC when receiving BPSK-1000

Andre v Schaijk sats at pe1rdw.demon.nl
Thu Aug 18 09:26:36 PDT 2011

Op 18-8-2011 16:08, Andrew Glasbrenner schreef:
> > From what I have read that is published, the DOD Colony II 3u cubesats are 3 axis controlled and pointable to within a degree or something close to that. As Bob pointed out this isn't a big help for antenna pointing for multiuser LEO sats, but when you read the power production the Colony II sats have, you'll see the application in a HEO orbit. I believe a 3u in HEO with this ability would be an affordable, usuable satellite for AMSAT to launch if we could duplicate the Colony sats abilities.
> 73, Drew KO4MA/p at the corner of No and Where, Oklahoma
> Sent from my iPhone
> On Aug 18, 2011, at 7:47 AM, "Bob Bruninga"<bruninga at usna.edu>  wrote:
>> [Using attitude control]...
>>> We could mount microwave antennas on a nadir-facing
>>> surface and provide consistent, predictable, strong,
>>> wideband signals to ground stations during a pass.
>> The problem with LEO satellites is that a nadir facing antenna does give
>> great gain directly overhead ground stations, but only for about the center
>> 2 minutes of only the one direct overhead pass a day.  The problem with
>> facing antennas "down" on a LEO satellite is that 90% of the users are not
>> "under it", but to the side of it.
>> For example, lets say that we put relatively high gain antennas facing down
>> giving about a 45 degree antenna pattern (say around 10 dB).  Now looking at
>> the total time that ARISSat is above 45 degrees, turns out to be about 3
>> minutes a day or less than 10% of all the time it is in view to any one
>> ground station.
>> But as you say,  it is a great advantage if the objective is to provide a 2
>> minute comm. window to anyone on the planet once a day, then such a design
>> does give as much as 16 dB or so advantage over an omni antenna on a
>> satellite.
>> Anyway, just a thought.
>> Bob, WB4APR
Has anyone ever considered piggybacking on a geosat in a simular way the 
rs11 to 13 did?
Sure you would need a very good lobbyist to get a ride with a multi 
milion dollar broadcast sat and it would only see one continent but it 
will give that continent 24/7 coverage, using 3 cm as downlink it would 
give pleny bandwith for all kinds of experiments and if you can use the 
host sat's powerbus there would also be no power restrictions.

73 Andre PE1RDW

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