[evlatests] General Good Health

[Rick Perley]

    Lest by previous messages discourage everybody, I here report on 
overall system performance, from the tests taken at noon today. 

    Overall, things are working very well!  Data quality is excellent on 
nearly all antennas. 

    Some notes on data at L, C, X, and K bands:

    1) Antenna 25 is not working at any band -- a known problem -- but 
the data are not flagged. 

    2)  Antenna 11, of IFs B and D only, at L-band only, have occasional 
short (0.41 second) dropouts.  The drops are a little longer than this, 
as the records on each side are partially affected.   The partially 
affected records are always low by the same factor on each side of the 
dropout, so the cause is aware of the integration time. 

    3) Antennas 27 and 28, of IFs C and D only, at L-band only, are 
showing notable changes in visibility amplitude -- which are not seen in 
correlation coefficient -- and which are clearly being 'created' by 
erroneous measures of system temperature.  The effect is slow -- 
changing over timescales of seconds to minutes. 

    4) The phases of VLA antenna 12, on IFs A and C, are just crazy.  
This antenna's phase behavior has been noted before by Vivek and me. 

    5)  The well-advertised, and heretofore repeatable global (VLA cf. 
EVLA) phase jumps, seen on IFs A and C when a scan is changed, but with 
no change in frequency or bandwidth, *did not occur* this morning!    
All phases connected perfectly.  (A minor change was made on today's 
test -- the 2nd scan was done with a different integration -- 10 seconds 
in 'solar' mode (translating to 1.67 seconds).  But it's hard to see how 
that could affect phases ...)  Barry says he made no changes to executor 
code since last week, when this global problem occurred on every change 
of scan. 

    6) At C-band, antenna/IF  11D is flagged as bad, but gives good fringes.

    7) At K-band, antenna/IFs 11D and 18B are flagged as bad, but give 
good fringes.