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

Andrew Glasbrenner glasbrenner at mindspring.com
Thu Aug 18 07:08:06 PDT 2011

>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
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