[evlatests] More on Drop Behavior

[Ken Sowinski]

On Wed, 28 Jun 2006, Rick Perley wrote:

>    Drops were seen at all frequencies on antenna 13 on all IFs, and on
> antenna 18, IFs B and D only.
> No drops were seen on antenna 24.  All drops were 'on the 1s'.

When Rick finished I took a few minutes to look at this
to verify what would happen if the executor were stopped
or phase switching disabled.  I did this by running a
private executro using Xyssstart and running the VLA with
1-2/3 second intgration interval.  When I did this there
were no dropouts at all on antenna 18; the 18BD dropouts
remained.  These came in three varieties which reduced the
amplitude by 1/3, or by 1/20th, or not at all.  The largest
dropout was most prevalent.  The no dropout was very rare.
The dropouts in 18BD stopped when the executor was stopped.
Rick used 0.4 s integrations, but I maintain that the EVLA
knows nothing about the VLA integration interval.

We should keep in mind that the 18BD L302 is not of the same
vintage as those in antenna 13.  This smells of more than one
problem and I was hoping to exercise the failure more on
antenna 13 to see if there were any differences.  I don't see
how to explain that I never see the antenna 13 dropouts when
running Xsysstart while Rick and Walter routinely do when
running their test scripts.