[evlatests] Wednesday 'Stress' Test, 8AM

[Rick Perley]

    Rob requested a check to see if antenna 26's phase behavior had 
returned to normal, following the discovery that the fans were not 
operating, yesterday afternoon. 
    I ran my standard 'stress check', with the following results.  
Antennas 1, 4, and 6 were out of the array.  Referenced pointing was 
successful on all other antennas. 

    A) Issues seen at all bands:

    1) Antenna 26 phase is fine, as reported earlier.f

    2) Antenna 18D phase is 'shredded'.  Rob has already addressed this. 

    3) Global phase jump occurred -- as always -- at L, C, X, K, and Q 
bands, following the P-band observation, which was the only one taken at 
a BW not equal to 50 MHz.   No global jumps were seen when observations 
at L and C bands were repeated (with no change in band). 

    4) The first record of every scan is bad, and unflagged, following a 
band change.  Following this bad record, data are properly flagged (with 
K-band-dependent exception noted below) until the antennas are stablized. 

    5) The last scan I requested in the run executed normally, but was 
followed by an unrequested scan, at the same frequency, with rather 
interesting characteristics:

       - Good data for 8 seconds

       - No data for 11 seconds.

      -  Seemingly good data -- but actually bad, and not flagged, for 9 
seconds.

      - No data for 2 minutes, 10 seconds.
     
       - Visually crappy data, and not flagged, for 7 seconds. 

    B)  Band-Dependent Issues

    1) C-Band:  The EVLA and VLA were mutually incoherent in IF#1 only, 
for the single scan immediately following the P-band spectral line 
observation.  Scans following this one (at other bands) were fine. 

    2) X-Band:  EVLA antenna 11 has sensitivity low by ~20%.  Probably a 
Tsys issue.  Otherwise, all is fine. 

    3) K-Band:  As reported by Emmanuel last week, the EVLA antennas are 
slow to come into equilibrium.  In IFs A and C only, the correlator 
coefficients are too low, and rising, for most antennas, for the first 
~5 seconds of the scan -- following the end of flagging.  Each EVLA 
antenna behaves differently -- some do not show the problem, others show 
it quite spectacularly.  Some reach full amplitude, then decline, and 
rise again.  The K-band observations follow X-band -- I bet K-band runs 
'hot', and X-band 'cold' -- leading to the largest required attenuator 
change. 
       Antennas 19 and 25 have much lowered sensitivity.  Both are due 
to high Tsys (100K for 19, and 200K for 25, on all IFs). 

    4) Q-Band:   No fringes on antenna 17, IFs A and C.  Antenna 13 has 
very poor SNR on all IFs.  Antenna 26 has poor SNR in IFs A and B -- 
probably a system temperature problem. 

    5) L-Band:  Antenna 13A was flagged throughout all scans -- but the 
data appear to be normal. 

    6) P-Band:  Antenna 13 is not functioning correctly.  IFs A and C 
are flagged (and properly so!).  IF's B and D are not flagged, but 
should be!  IF 'B' is weak by a factor of 25.  IF 'D' is weak by a 
factor of four. 
       Antenna 25A is weak by a factor of ~2.5
       VLA antenna 28, in LCP (IFs C and D) is weak by a factor of 6. 
       Antenna 19C is flagged, but the data look fine.