[evlatests] EVLA Health Check, Monday AM

[Rick Perley]

    An hour of dynamic time was put to good use this morning, checking 
on EVLA viability. 

    The usual setup -- fast continuum, and spectral line, on a strong 
calibrator. 

    Referenced, and double-referenced pointing was done at C, X, K, and 
Q bands. 

    Results:

    A) Global Observations

    1) All referenced pointing scans worked beautifully.  Even the 
Q-band double-referenced pointing worked on all antenna with working 
receivers. 

    2) Phase stability (on the two-minute timescales I'm using) was 
outstanding, with the single exception of 14C, where the 150-degree step 
is back at P and L bands.  However, the character of this has changed, 
with a least 95% of the observations now in one phase state, and only 
occasional steps to the other state. 

    3) Antenna 26D has its multiple amplitude states back, visible at 
all bands. 

    4) All bandpasses and delays look great. 

    5) Antenna 13D has a 'ramp-like gain' function:  the amplitudes drop 
by ~3% over 30 seconds, then discontinuously return to the higher 
state.  Seen at all bands. 

    6) The usual, uncommon, short and shallow amplitude drops are present. 

    B) Band Specific Observations

    1) P-Band:  Antennas 14, 17, and 23 working on all IFs.  Antenna 21 
has its polarizations reversed. 

    2) L-Band:  Antenna 13B and D (IF #2) was dead.  Antenna 24 B and D 
has a very unstable amplitude, particularly notable on D. 

    3) C-Band:  No fringes from 16, 21, 23 or 26.  I think all of these 
are known to be non-functional or not yet outfitted. 

    4) X-Band:  All 9 antennas working very well.  An peculiar gain was 
seen on 14C and D (i.e., in LCP) whereby they jumped up by 10%, then 
slowly settled back over 15 seconds to normal.  Looks like a rogue Tsys 
value. 

    5) K-Band:  Antenna 23 gave no fringes, but has a receiver.  Antenna 
18 was weak, and the cause is easy to determine -- a failed primary 
reference pointing because of a large (>1 arcminute) elevation error.  
Ken has convinced me that this is due to solar heating.  (Most other 
antennas showed similar offsets, but just a little bit smaller. 

    6)  Q-Band:  No fringes from 17, 21, 23 or 26.   The last two are 
supposed to have a receivers installed -- right?