[evlatests] L-band 'RSRO' amplitude and phase stability

[Rick Perley]

    The short 'wideband' test from Sunday evening has now been reviewed 
for phase and amplitude stability. 

    In general, the news is very good.  I utilized subbands 4 and 7 for 
this analysis, as the widespread RFI make full analysis tedious.  All 
indications are that these two subbands represent the others well.  
Subband 4 is from the 'AC' IF pair, and is centered at 1448 MHz.  
Subband 7 is from the 'BD' IF pair, and is centered at 1840 MHz. 

    1)  Amplitude stability. 

    * Three antenna showed time variable gains on all IFs -- these are 
clearly due to shadowing.  I had imported the 'uvflg' file sent my 
Michael, but apparently the shadow flags are now present.  (I thought 
they were supposed to be?)
In reviewing the messages offered by 'UVFLG' (which reads the 'uvflg' 
file), I see the only flagging messages are for 'subreflector error', 
'not on source', and 'focus'.  Nothing about shadowing.  (Also, these 
messages do not identify the antenna, IF, or time -- it would be very 
useful if they would!). 

    * Antenna ea12 has dramatic variability on IF 'C' only -- from 0.1 
to 1 dB.

    * Antenna ea25, has *spectacular* (3 dB or more) variability on IFs 
A and B only (RCP). 

    * Antenna ea28, on IFs C and D (LCP) has one scan where the 
amplitudes vary by factors of 50% or more on 1-second timescales, yet 
the phases are stable and normal.  (Weird!) 

       Other than these, all operating antennas gave excellent stability. 

    2) Phase stability. 

       * Antenna ea11, in IFs BD only had a single 150 degree phase jump 
in the middle of the run.

       * Antenna ea14, in IFs B and D only, had a small 20 degree phase 
jump within a few minutes of the beginning of the run. 

       * Antenna ea25, in IFs A and B (RCP) had large phase jumps, which 
match the spectacular amplitude changes noted above (meaning, they occur 
at the same time). 

       * Antenna ea08, on IFs A and C has a 160 degree phase jump, also 
within a few minutes of the beginning. 

    Some antennas showed a ~10 degree phase difference between the flux 
calibrator (3C295) and the target soruce (J1822-0938) -- these are 
separated by more than 1 radian.