[evlatests] EVLA L-band status

[Rick Perley]

    I did a quick test of EVLA capabilities last night.  For this, I 
used the
'fast continuum' mode, observing a calibrator and blank sky, at each of
the EVLA-equipped bands. 

    This is the L-band report. 

    1) Antennas 13 and 16 were dead throughout. 

    2) Antenna 14 came on late, but worked well once on source. 

          however ...

    3)  The system temperature table entries are nonsense for all
three antennas:
          - 0 (precisely) for antennas 14 and 16
          - 1.9 K and 2.1 K for antenna 13 in RCP and LCP, respectively. 

    4) The 'aipsweight' for antenna 14 (after calibration) shows it to be
the least sensitive antenna -- 30% below the best VLA antennas, and
10 to 15% below the median.  (Note that the aipsweights are proportional
to G/Tsys squared, so a 15% loss in aipsweight corresponds to a ~7%
degradation in the G/T ratio.  This can easily be accounted for by the
lower efficiency of the EVLA L-band feed, which is thus not sufficiently
compensated by improved Tsys). 

    5) Phase and amplitude stability within the three observations on a
calibrator were very good -- equal to VLA antennas -- with a
single spectacular exception.  See below.

    6) Within the third calibrator observation, the derived aips gain (a
voltage equivalent) dropped by 6% on a very fast timescale -- 0.5 seconds,
stayed down for 1.3 seconds, then abruptly (in 0.4 seconds) recovered -- 
actually
*over-recovered* to a level 4% *higher* than before, then slowly dropped to
the pre-existing level (over 20 seconds).  There was no corresponding phase
effect, and no change in closure during this event.  It looks like a 
pure amplitude
perturbation.