[evlatests] New WIDAR data

[Rick Perley]

    Michael took lots of data yesterday with the improved WIDAR.  One of 
the datasets included observations of four sources, all near 3C286, 
taken in a more-or-less cyclic fashion, over 90 minutes, each 
observation of each source about 90 seconds long. 

    This is a partial report -- the results of the imaging will come 
along later. 

    The data are, in general, of excellent quality.  The problems noted 
(mostly already known) are:

    1) Antenna 3, subbands 3 and 4, in LCP are still bad. 
    2) Antenna 9, in LCP, seems to have no phase model, or the wrong 
phase model, applied -- phases are spinning quickly (but slowly enough 
to permit calibration).  
    3) Delays (relative to antenna 1) in RCP are typically less than 30 
nsec, except antenna 8, which is 163 nsec.
    4) Delays, in LCP, are larger, typically 70 nsec, except antenna 3 
(190 nsec) and 8 (151 nsec).
    5) Cross polarization delay is now -64 nsec (LCP referenced to 
RCP).  This is quite a bit less than the last time I measured this (-180 
nsec, last month). 
    6) Antenna 1 'went bad' (weak, with random phase) in LCP, on all 
sub-bands, at 23:32:45 IAT.  It came back a few minutes later, but with 
a much reduced amplitude. 

    I could find no zero records (yeah!!!), and few, if any 
'drop-downs'.  Other than the known initial records at the beginning of 
each scan being weak due to antenna motion, the data look very clean 
throughout.  All phases are stable, and connect well.  There may be a 
position-dependent phase change however -- the phase offsets for 
1407+284 (the most distant source from 3C286) are larger than for the 
other two sources, both of which are much closer to 3C286, which I used 
as the phase reference calibrator.  Baseline errors? 

    Plots of the visibility amplitude and phases (using a single 
channel) show no evidence whatever of any oscillations in either 
amplitude or phase.