[evlatests] AJ329 report, C band, September 18. Note antenna 18 is bad!

[Jim Ulvestad]

Report on AJ329, C band 50 MHz continuum, observed September 18
===============================================================
Note error in X band report yesterday--AJ329 X band was
observed on September 17, not September 18.  C band
was observed on September 18, and is reported here.

Four EVLA antennas used: 13, 14, 16, 18.
10 second integrations, standard VLA C-band frequencies.
1.5 hours of observations.
Note that fluke setting was 100.000000 (default), but
there was still a VLA-EVLA phase jump (see below).

Antenna 14AC and 13BD were both bad at X band, consistent
with Ken Sowinski's report on September 14.

Otherwise, EVLA antennas performed fairly well.  In 11 scans,
there were NO instances of bogus data points in the very first
record, only on EVLA-EVLA baselines that got through unflagged.
I saw no sign of drops in the very last points of the scans or
of the whole observation.

Some time between 10:40:30 and 10:54:30, the EVLA
antennas jumped in phase by about -110 deg. relative to
the VLA antennas (see attachment PHASE.PRT).  In the past,
these types of phase jumps have usually occurred on source
changes, so I suspect the jumps may have been on the change
to or from the target source in between.  Since that is a
very weak source, the individual phases are pseudo-random,
so it's impossible to tell exactly where the jump occurred.
All four IFs jumped together.

There is mild evidence for an additional jump of about 15
degrees on antenna 18 relative to ALL antennas, including
the EVLA and VLA antennas.  Again, see attached PHASE.PRT
There is some other evidence that 18 jumped by 15 degrees
later on against VLA antennas, but not EVLA.
See attachment PHASE2.PRT, where the phase of antenna 18
is shown vs. 6, 13, and 8, located at W8, W12, and W16,
respectively.  It's conceivable that the apparent 15
degree jumps were due to atmosphere, but W8, W12, and W16
are not doing the same thing.  Since these antennas are not
real close to each other in B configuration, I classify
this as a possible oddity to be watched, but it doesn't
look to me like something to spend time on at the moment.

Antennas ranked by AIPS weights below: 1 is best, 24 is worst.  Note that
antennas in the middle are fairly similar; i.e., the 3rd best antenna
and the 10th best antenna typically are not very far apart.

Antenna 18 is much WORSE than at X band, with AIPS weights on
baselines to 18 being a factor of 5 worse than the next worse
antenna in the array.  Antenna 16 RCP is spectacular, much
better than anything else in the array, but LCP is so-so.
The working IFs on 14 (BD) are better than everything
except 16 by a fair amount.  The working IFs on 13 (AC)
are also very good.

13A (RCP) - 2 (behind EVLA antenna 16 only)
13B (RCP) - OUT
13C (LCP) - 1 Tied (with VLA antenna 20)
13D (LCP) - OUT

14A - OUT
14B - 2 (behind EVLA antenna 16 only)
14C - OUT
14D - 1

16A - 1 (great!)
16B - 1 (great!)
16C - 9
16D - 8

18A - DREADFUL
18B - DREADFUL
18C - DREADFUL
18D - DREADFUL