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Re: SDR Prototype transponders



I think the SDR/DSP technology is a great way to improve future AMSAT 
linear transponders.

I attended the AMSAT-UK Colloquium and was impressed by Howard G6LVB's 
presentation about STELLA.
I think this should be a must-have feature on future designs as it kills 
any alligator behaviour.
Having worked/trying to work FO-29 and VO-52 this week in late night 
european passes it really is terrible how these birds sound
if a few people are on using high power and ruining it for everybody else...

So it would be great to have such hardware (software) on board of new 
spacecrafts but on the same time I think we're smart enough
to not rush into launching complex technology like this before it is 
tested through and through.


Andre PH7AT


Robert McGwier wrote:

> Right.  The thing I would fight to see happen (and nothing more) is 
> that we be allowed to switch into the P3E existing systems somehow and 
> pick off the IF and essentially replace the analog back end with the 
> QSD/QSE backend.  Again, we are using the QSD/QSE for exactly the same 
> reasons Howard is using it:  very high IP3,  very good dynamic range,  
> unbelievable Q, very low power.  We intendi building the EAGLE 
> transponder "from the SDX out" and to allow an analog back end of less 
> capability to be the "failsafe".   All we can afford to do in P3E is 
> to use the existing IF's and for us to be switched in and out as any 
> other back end and to make this experiment as simple and effective as 
> it can be.   From what I have seen of Howard's design, there are only 
> a couple of things I would change and we can discuss that as we decide 
> who is doing what and what to build.  P3E project management is 
> deciding on the interfaces and the specifications and the rest of us 
> (Howard and the four stooges in DC, etc.) decide whether we can do it 
> electrically, and in time for inclusion in the project.  This is 
> complex.  We have to be controllable by the P3E control mechanisms and 
> interface cleanly with the existing transponder which I believe 
> William is doing.
>
>
> Changing the bandwidth of the QSD/QSE is  . . . . .   changing 4 
> capacitors.  That is all there is to it.
>
> We (four stooges in D.C.) chose to go the "existing hardware out 
> prototype".  We used two SDR-1000's and Linux software running on a 
> 200watt Linux computer!  We are not talking about flying a Mini-ITX 
> Pentium 4 in orbit.  We are doing a demonstration of WHY one wants to 
> do an SDX. Howard chose the "let me do an interface I believe will 
> work with P3E" approach.  He took on the harder job of getting his DSP 
> widget working before he worked on showing the software will work.   
> We need a 50-100 Mhz DSP core to do this job.  So far as I know (such 
> as Howard's TMS32C67) , one has not been subjected to radiation 
> testing.   There is a LOT to do to get such a thing ready for P3E.  We 
> are not fooling ourselves. We will collectively take the specs 
> AMSAT-DL gives us and collectively decide if we can in the time alloted.
> Bob
> N4HY
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