[evlatests] C-Band report

[Rick Perley]

    At C-band:

    Antennas 13 and 16 were dead.

    Antenna 14 was up and alive, and performing very well:

    - amplitude and phase stability excellent within any scan.  No 
dropouts of any kind. 

    - the phase changes between scans. 

    - the aipsweights showed 14AB to be 25% better than the best VLA 
antenna, and at
least 50% better than the median VLA antenna.  (Correcting an error made 
in the last
message -- the 'aipsweights' I'm using are the baseline-based ones, so 
the values used here
are proportional to G/Tsys).   However,  for 14CD the situation is the 
reverse -- the
weights show 14 CD to be much worse than the worst VLA antenna.  A 
receiver Tsys
on the LCP side might be the problem.

    - Tsys values for 13 and 16 were ridiculous -- about 1K for 13, and 
hundreds of
thousands of K for 16.
    - Tsys values for 14 looked good -- mid 20s for all IFs.  However, 
this is incompatible
with the large difference in aipsweights between polarizations.  What to 
believe?  Evidence
that the Tsys are o.k. is that the change in Tsys between cal and source 
is what we expect
(about 1K) on all IFs.  But then the large degradation in apparent 
sensitivity on the LCP
side would have to be an efficiency effect.  How can this happen?