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

Bill Ress bill at hsmicrowave.com
Mon Jul 9 19:34:19 PDT 2007


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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