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Re: Keep It Simple Silly



 
To say the hardware does not not get any simpler is perhaps true for the  
number of components, but the complexity within those components is  much greater 
than anything flown before in AMSAT transponders. It's  probably true to say 
that Eagle will use 20,000 transistors to do the same job  as 20 transistors 
in Oscar 7. But it's also fair to say those 20,000  transistors will do a much 
better job.
 
The SDX technology will get its first on orbit test with suitsat2.   That 
will tell us all something about reliability in LEO before launching Eagle  and 
P3E.
In 2009 The SSETI ESEO mission to a higher radiation geostationary transfer  
orbit will include a mode U/S transponder. It converts 435 down to 10.7MHz and 
 that signal can be routed to a software defined transponder or to  a 
conventional linear transponder before being upconverted to 2401MHz.  Hopefully, the 
SDX will perform flawlessly, but should there be a problem,  then the 
satellite can be commanded to bypass the SDX and use a  traditional circuit.
Somewhere along the line an SDX will be designed that is reliable and give  
much better performance than whats been flown in the past.  It's a learning  
curve, there may be problems along the way, but we have moved on since October  
4th 1957 and we need to investigate new technologies and sort out what works 
and  what does not.
 
Happy 50th birthday Sputnik  (I wonder how many valves were inside  that?)
 
David  G0MRF
 
 
 
 
 
 
In a message dated 30/09/2007 16:06:16 GMT Standard Time,  hartzell@gmail.com 
writes:

Even as  a proponent for SDR (and an SDR "user"), the lingering thought
in my mind  regarding SDX in space is survivability.

There is no flight heritage  (yet) for an SDX in space, and there is
quite a bit of complexity with  regards to software and integrated
components (ADCs, DACs, FPGAs, CPUs,  etc.).

But these problems plague analong XPNDRs as well....with the  right
selection of components, de-rating of components, and  rad-hardened
when feasible, chances for success  increase.

73,

Dave
n0tgd

On 9/30/07, David B. Toth  <ve3gyq@amsat.org> wrote:
>
> Patrick: it is too bad that  you were unable to join us here in
> Hartford, CT this weekend for the  TAPR-ARRL DCC ...
> There were many presentations on SDR, some by AMSAT  personnel ...
>
> The hardware does not GET any simpler than in  SDX ... the HUGE
> advantage is that a component with a shifting value  (such as might
> occur in a spacecraft with wide temperature swings)  does not degrade
> the performance/optimization of a device, because if  the hardware
> does age/shift, then that can be compensated for in  software ...
>







   
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