VLA Test/Observation Coordination Meeting
                           B.G. Clark
                        October 19, 2006

1.  VLA phase jump problem

R. Perley finds that there is a phase jump between the IF pairs
(that is, between IF 1 and IF 2 RCP, say) after a band change and
return to the original frequency.  This does not happen every band 
change, but often enough to be worrisome.  When it happens, it does not
occur on every antenna.  In fact if seems to have a preference of occurring
on antennas 12 and 6.  It is not known what causes this, and in fact, 
moderately strong arguments can be advanced against attributing it to
any of the hardware or software pieces suggested as a possible cause.
The problem is of no concern if you do not change bands.  If you do,
it is taken care of by the procedure (now recommended for EVLA 
compatibility) of always calibrating immediately before and after a band 
change.

It is not now known if this effect occurs on frequency changes within 
the band.

2.  Current maintenance problem.

The Modcomp real-time computers which run the array are currently being
a bit flaky.  This points up that these beasts are getting very old, 
and the people who can fix them are becoming few.  Going to the EVLA
system with modern components is the eventual solution.  For today,
we will just fix the Modcomps (we hope).

3.  EVLA

B. Clark reports that antenna 26 is still very much in a checkout phase;
it now has all 4 IFs, as seen at X band, but the two other receivers
installed (L band and K band) are not seen.