[eagle] Re: CAN-Do-Too! ??????????

Jim Sanford wb4gcs at amsat.org
Mon Jul 9 19:47:13 PDT 2007


Bill:
Thanks.

I'm exhausted.  More detailed response tomorrow.  YOu make good points, 
we need to decide how to proceed.

Thanks & 73,
Jim
wb4gcs at amsat.org


Bill Ress wrote:

> Jim Sanford wrote:
>
>> 4.  EMI Spec:  You put a gun to my head, and I'm going to pull out 
>> the MIL-STD, which is probably overkill, but MAYBE NOT.  I'd really 
>> prefer that one of you guiys current in the INDUSTRIAL world take on 
>> this task and come up with something good enough and reasonable.  In 
>> general, I'd like to eliminate as much mass and extra "touch" labor 
>> in the assembly process (multiple shields) as possible.  Bob Davis:  
>> Please weigh in here, if the possible milled modules simplify this 
>> issue, please enlighten us.
>
> Jim, I think an EMI spec pulled out of a MIL-STD would be an over kill 
> effort and likely not representative of "our" real world. What we need 
> is not assumptions but data reflecting what the hardware does. The 
> problem is that we don't have the hardware - and that's my issue. The 
> power distribution circuits are what I call a "top level" subsystem 
> which feeds "everyone." Instead of working on the circuitry that will 
> run from it and trying to "imagine" what we can expect, let's focus on 
> breadboarding the key power distribution circuits and get some hard 
> data so we know what we're working with.
>
> I'll again reiterate (as I have several times in the past) the same 
> thing for the satellite's 10 MHz reference. It's another top level 
> "subsystem" that will feed "all" LO's. Instead of guessing what we'll 
> be working with, let's get it defined too.
>
> (I'm proposing we put that one to bed and use the time tested, well 
> defined, high stability, low noise HP (OK - Agilent) 10811 series of 
> reference standards used in most of their test instruments. If that 
> won't cut it - someone please tell me why!)
>
>> 7.  Requirements:  Bob McGwier is correct, we really did start with a 
>> very top-level requirements document.  It is not perfect (Bob has 
>> hated it from the word go), but can be found on EaglePedia under 
>> Functional Requirements.  It is also in need of updating, after the 
>> October BoD decision.  On my list to do.  Like you, I have finite 
>> energy and time, but it is on my list.  I think John did an EXCELLENT 
>> job of documenting the UHF Receiver requirements based on what he 
>> knew.  The need for an EMI spec was not obvious, but is now, thanks 
>> to Juan's testing efforts and exceptional documentation.  Lou:  
>> Functional requirements for power supplies?  Bob Davis:  Functional 
>> requirements for structure and thermal performance?  etc. etc.....we 
>> have much to do, but I think worthwhile effort.  By the way, I'm 
>> reading (in a few spare minutes here and there) an EXCELLENT book on 
>> requirements management.  When I finish, look for a review of it on 
>> my project management page.  I will also be providing suggestions on 
>> writing "good" requirements, based on that book and my recent 
>> experiences in the day job.
>>
> Yes, we have "top level requirements" for desired satellite functions, 
> operating modes and parameters and link budgets. But again, I think 
> we're sorely lacking in key "system"  performance requirements based 
> on real data  - - -  which can only be obtained by building and 
> testing these key functions.
>
> I'm not a power supply guy, but I'll offer to assist in building and 
> testing the circuits we need to characterize. Lou - point me in the 
> right direction - tell me what you need!
>
> Regards...Bill - N6GHz
>
>


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