[evlatests] More on current L-band from yesterday

[Rick Perley]

    As noted by Ken, a short run was made yesterday, with the variant 
antennas 25 and 28 removed, and the newly available antennas 4 and 8 
in.   The script was the same as Sunday's data:  1m20 second scans on 
the northern calibrator 0217+738, with offsets of 5, 10, 15 and 20 
arcminutes.  The observations were the the late afternoon, and the 
source elevation was very low -- about 25 degrees.  (If subsequent tests 
will be done in afternoon/evening, we need to select a new object). 

    Antenna 8 has no L-band feed.  Antenna 4 fringed nicely. 

    Delays (w.r.t. ea01) are small, except for antenna 4:  +47 nsec. 

   Data quality appears excellent, with essentially no flagging needed, 
other than at the beginning of each scan.  

    The 180 degree 'phase hops' are back!  This is the first time (that 
I know of) that these have been found to occur for scans longer than 1 
minute.  Hopping antennas are:  2, 4, 18, 19, and 24.  Non-hoppers are 
1, 3, 9, and 23.  (As usual, we can't tell which set hops and which does 
not).   Phase hops do not occur on an ~11 minute grid, either.  As 
always, all sub-bands hop by the same amount (180 deg) at the same 
time.  The  time ranges within the hops occurred at:  (uncertainties due 
to off-source observing):

    21:00:17 and 21:01:38
    21:02:57 and 21:04:19
    21:05:36 and 21:06:58
    21:13:39 and 21:15:01
    21:21:42 and 21:23:04
    21:24:21 and 21:25:43
    21:35:04 and 21:36:24
    21:37:43 and 21:39:05
    21:45:46 and 21:47:07

    I followed the usual calibration route (BPASS, CALIB, CLCAL), and 
made images of the on-source object.  No background sources are seen, 
and the usual lumpy artefacts dominate.  Because of all the phase 
hopping, I did not attempt to image the off-axis positions.   As 
reported earlier, there was with this observation some issues with the 
SDM, which might have affected the apparently good data. 

    I think a new observation, at high elevation, with all 12 antennas, 
and with all known bugs repaired, is warranted.  I suggest 3C147 
(0542+498), as a strong source calibrator.  We'll also need a nearby 
weak source, to reveal background structure.