[evlatests] 19 Sept Stress Test

[Rick Perley]

    One of my continuum stress tests was run early this evening.  
Initial results -- from L-band only. 

    Antenna 13 was out of the array. 

    All others (including ea25) fringed, at least in part. 

    a)  Amplitudes:

    ea14 gave no fringes (and was properly flagged) on IFs B and D  
(IF#2). 

    va4 is in a very sad shape.  All four IFs have large and common 
amplitude drops.  These are very fast -- 0.418 msec in duration.  IFs A 
and C drop in a similar manner, as to B and D.  But the two IFs have 
quite independent patterns.   The problem is in amplitude only. 

    One of the 'correlator controller resets' took place in the middle 
of the run.  The symptoms  are always the same:  Bad data, on all 
antennas, at some particular time continues until the next 10-second 
tick.  There are no data for the following 10 seconds, after which all 
is fine.  The bad data are not flagged. 

    Many EVLA antennas have occasional (once per minute, or less) drops 
in amplitude:  11B and D, 18 on all IFs, 24 on B and D. 

    ea17 has two different amplitude levels, on all IFs.  There is one 
drop per 1.67 seconds, approximately.  The drop amplitude is about 15%. 

    None of the amplitude effects noted above have any corresponding 
phase effects. 

    B)  Phases:

    As reported earlier by me, and by Vivek, we have a global EVLA to 
VLA phase jump when scans change -- but only on IFs A and C.  In this 
test, I observed the same source four times at L-band, 50 MHz BW, with 
no change in frequency.  The VLA to EVLA A and C IF phases jumped -- by 
different amounts -- at each scan change.   The jumps in A and C are 
identical. 
    The first jump was by +180 degrees, the second was by +43, and the 
last was by +250 degrees.  As always, I can't tell which array 'jumped'. 

    Antenna 14's phase wandering is gone.