[evlatests] Continum IF1-IF2 behavior from Wednesday afternoon

[Rick Perley]

    This summarizes all the continuum data taken yesterday afternoon: 

    50 MHz
    2 minutes duration on 3C286, cycling around L, C, X bands
    Default frequencies at each band.
    0.41 second integration/dump. 

    Two hours were spent in this mode.  Ken then followed this with 35 
minutes of standard 10-second continuum observations of 3C345 at C-band. 

    Results:

    The phase jump problem is seen, but only in a few antennas, and 
almost always on IF 2. 
    The behaviors for C and X bands are nearly identical:

          Antennas 1, 11, and 25 each showed one or two jumps, only.
          Antenna 22 showed 6 or 7 jumps at each band -- all in IF 2. 

    Size of the jumps is about 80 degrees. 
   
          Interestingly -- during the 35 minutes on 3C345, at the same 
frequency, but with 10-second integrations, no jumps were seen on any 
antenna. 

    The behavior at L-band is rather different:

            Antennas 1, 5, and 11 had one or two jumps only. 
            Antenna 3 had dozens of jumps, but these are of a very 
different nature, with the phase jumping back and forth.  This 
characteristic is only seen in IF2, and only at L-band. 
             Antennas 6 and 8 each had about 6 jumps.
            Antenna 27 had about 10 jumps. 

    Finally:

       The EVLA antennas showed no IF1-IF2 jumps at any band.  (But -- 
they showed many jumps within each IF -- this problem is for another 
day).  To my recollection, the current IF1-IF2 problem has *never* been 
seen on an EVLA antenna.  (Point of emphasis -- this doesn't mean the 
EVLA phase behavior is perfect -- it only says that whatever changes are 
still going on at a given frequency and IF is reflected in the other IF 
also).