[amsat-bb] Re: Future radical satellite designs

Robert Bruninga bruninga at usna.edu
Mon Jul 9 06:17:40 PDT 2007

> ...  Our goals are to put together a single 
> ham radio payload in a cubebesat. 

My personal opinion of the most exciting and easy MULTI-USER
transponder is what we have attempted on PCSAT-2 (failed
antenna) which is a 10m SSB uplink receiver for up to 30 PSK-31
users and then a single 2m FM audio downlink.  The more of these
we can fly the better.

They have all these advantages:
1) single channel FM downlink!
2) Multi-simultaneous user uplinks
3) 9 dB downlink advantage over UHF downlink to an HT
4) Receipents only need an HT and laptop to receive all
5) No doppler tuning on downlink
6) No hogging/congestion by FM uplink operators
7) 10m uplink has minimum PSK-31 uplink doppler
8) Uplink doppler can easily be conpensated in software
9) Everyone sees EVERY PSK-31 QSO at the same time
10) Everyone sees same Doppler/Frequency/relationships

Easy to hit with 25W 10 meter SSB rigs (usually available from
radio shack for under $150 when the band is open)...

When satellite comes into view, there you are.  30 simultaneous
users typing away with all being seen at the same time by the
typical multi-user PSK-31 display software.

I think it would be a very exciting transponder.


  Have spoken to 
> several persons in the Amsat NA origination.    They have 
> agreed to do the peer review for us.   As we are week in 
> electronics part of it.   I am a retired aerospace machinist 
> and have for the last three years been doing a lot of the 
> mechanical work for Amsat.    So the mechanical side of it 
> will be easy for us.   On the payload we have not made a 
> final decision.   Here is some of our ideas.
>    1: Leverage from the electronic package that is planned 
> for Suitsat 2.   This our preferred payload.   As it would 
> give us a lot of flexibility with the SDR transponder.   Only 
> problem is when is suitsat 2 going to be ready?   If it is 
> going to take to long our group may not want to wait.
>   2: Would be to build a transponder with hamtronics kits.   
> Upside of this is that all parts are off the shelf and could 
> be easily assembled in few months.   Bob Bruninga has been 
> using them for some time with success.
>  3: Ask someone to build us a transponder who has more 
> experience than us.   On the orbit.   To me the ideal orbit 
> would be an MEO orbit.   To see what that would mean I 
> suggest David's G0MRF 
> http://www.g0mrf.freeserve.co.uk/MEOSAT.htm  website    I 
> have seen some talk on the web that that SpaceX maybe 
> launching cubesats into MEO. Otherwise there seems to be 
> launch availability in LEO.
> Fred KF0AK
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