[evlatests] Report on AD562 -- Wednesday Morning.

[Rick Perley]

    Dwaraka's third long observation at P-band is mostly a success.  
There are some notable issues:

    1) The first observation was on a strong calibrator, 3C48.  But the 
two arrays were incoherent with each other throughout.  All VLA - VLA 
baselines, and all EVLA - EVLA baselines are fringing strongly.  No 
X-baselines.   This is seen on all four IFs.  This effect usually means 
a small frequency difference between the two arrays.  The problem was 
not seen on any other calibrator observation. 

    2) The problem of having IF 'B' be incoherent between arrays did 
*not* occur on this run. 

    3) Antennas 13, 14, and 26 were left out of the array.  This is 
appropriate for antenna 13, but not for the other two, which indeed have 
P-band receivers.  There is certainly some confusion about antenna 26 -- 
Larry (the current operator) tells me his check sheet shows the antenna 
to be absent a P-band capability.  I can assure everybody that it 
fringes nicely at P-band, as Dwaraka's 2nd run had it included, and it 
worked nicely.  (However, in his first run, it was also kept out of the 
array).   I don't know why antenna 14 was left out of this run -- 
perhaps there is a P-band retrofit underway? 

    4) On the other hand, antenna 16, which does not have a P-band 
receiver, was left in the array.  Most of the data were correctly 
flagged.  However, starting near the end of the run, the correlator data 
from 16 were not flagged (and were of course noise).    

    5) Some detailed flagging notes:  Antenna 17 was correctly flagged 
bad when there were no fringes.  At  12:47 IAT, antenna 17 returned to 
service, and was flagged correctly.  However, at the same time, antenna 
16, which was up to that time flagged correctly, suddenly had its flags 
removed.  Coincidence, I hope? 
    Antenna 24B gave no fringes, but was flagged as good.  Its other IFs 
were fine. 
    As before, antenna 23, all IFs, was hugely erratic in amplitude.  
Chuck K. tells me its power is set 10 times too high.  It would be good 
to have this tended to.