[evlatests] Quick Stress Test

[Rick Perley]

    I ran a quick check of the system this AM.  Due to limited time 
(from Adv. Panel pressures), a careful check by me will not be 
possible.  I quickly checked L and X bands -- brief report below:

    1) L-band.  27 antennas operating.  However, IFs A and C, show on 
most antennas very large (factors of many) gain variations which are 
likely to be due to external interference.  This 'interference' is not 
seen on any of the north arm antennas (except slightly, on the two 
closest to the center), and is strongly seen on all east and west arm 
antennas, with the curious exception of antenna 15, located at E40.    
No explanation for this behavior is offered. 

    2) X-band.  Unsatisfied with L-band behavior as a useful diagnostic 
for system issues, I went to the X-band data.  The situation is much 
better here, in that the large gain variations noted above are absent.  
But there are some issues to note:
       Antenna 5A was flagged bad, but I think the data are actually 
fine, based on a couple of records that 'slipped' through the flagger. 
       Antenna 11A and C are showing occasional Short Shallow Drops 
(SSDs).  No big deal.
       Antenna 13, Ifs B and D have very clear *gain ramps* -- the 
amplitudes decline by about 2% (especially on IF D) over about 5 
seconds, then jump back to the previous level.  The effect is also 
clearly seen at L-band. 
       Antenna 16, IFs A and C have similar gain ramps, but of higher 
amplitude (about 10%), and on shorter timescale.  These ones are *not* 
seen at Lband, for this antennas.
   
       Otherwise, things look good, other than ~minute-long 'gain 
wobbles' of <1% amplitude, that are seen on many antennas (both VLA and 
EVLA), whose origin we will eventually have to track down.   Not a 
significant issue at this time (IMHO).

    I have data for an eager volunteer to review, at all the other 
bands, and which I cannot do at this time due to other pressures.