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
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
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?)
In a message dated 30/09/2007 16:06:16 GMT Standard Time, hartzell(a)gmail.com
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.
On 9/30/07, David B. Toth <ve3gyq(a)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 ...