[evlatests] evla confusion

[Jim Jackson]

I asked Ken about this yesterday.  How likely is it that MIB's could get 
the wrong time from the network?

Jim

At 08:42 AM 2/16/2006, Barry Clark wrote:
> > From evlatests-bounces at donar.cv.nrao.edu  Wed Feb 15 17:51:49 2006
> > Date: Wed, 15 Feb 2006 17:51:38 -0700 (MST)
> > From: Barry Clark <bclark at aoc.nrao.edu>
> > > Certainly the L302s are implicated.  Whether they are misbehaving
> > > on their own or just being mislead is hard to distinguish.  My vote
> > > is that sometimes they choose the wrong heartbeat when commanding
> > > the DDSs.  It is not at all obvious to me how you can get them to
> > > do this.
> >
> > Just getting the wrong heartbeat for the DDS will not affect the 
> amplitudes.
> > Getting the wrong heartbeat for the Walsh functions will not affect the
> > phases (except maybe by 180d).  There are complicated ways for the L302
> > to go wrong, but nothing so simple.
>
>I was wrong.  There is a simple failure that can explain many of the
>phenomena (trying to explain all problems from a single cause doesn't
>work with this machine).  If the MIB software is attaching the wrong
>time label to heartbeat interupts, displacing the walsh function will
>drop the amplitude, and getting one wrong on the timing of the strobe to
>the DDS will jump the phase.  We need to discuss with Pete whether this
>can happen, and how to detect it if it does.
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