Re: arrrghhhh ueing

[Tom Droege <droege@FNAL.GOV>]

Reply to Paul Breed and Alain Maury,

Well, when I started this project I looked for something like the AD9832
(thank you Paul).  I did not find anything I wanted to learn about.  Too
complicated at the time.  The AD9832 is not a bed of roses to an analog 
guy.  The stamp could probably load it, and it is a potentially easy 
product to use.  But looking at page 12 of the data sheet, I see that it
requires some work just to turn it on.  It also comes in a package that
I am not prepared to handle.  

There are a few hundred "items" in the Mark IV design.  I have to keep
each one as simple as possible.  "Simple" means I know about it and 
understand it.  This takes some time for each item I am using.  I have
these nice little stepping motor drivers.  Now they work great.  But I
burned up a bunch before I learned how to make them work great.

Digital DDS devices are not all they appear.  In the end they are only
as good as the crystal.  A typical crystal is only good to about 
3PPM/C. The device I am using is 50PPM/C.  I think I would want to 
temperature compensate either one.  I understand temperature compensation, 
and can probably hold something that I understand to <0.01%.  This is 
all I need.  But I might be using the AD9832 had it been available a
year or so ago when I started the Mark IV design.

A lot of people keep up with all the current devices but never get 
anything out the door.  The trick (I think) is to just set some date
and go with what you have in hand then.  

Tom