[evlatests] Amplitude and Phase Stability

[Rick Perley]

    I have reviewed amplitude and phase stability at L and C bands, for
antennas 13, 14 and 16. 

    Barry's observation that antenna 13 has a phase wind is *confirmed*. 
The phase wind is rather slower than he saw, but is certainly present:  
-25deg/min
at C-band, and -50 deg/min at L-band.  Adjacent VLA antennas showed
negligible phase wind, so this effect is caused by the antenna, not the
atmosphere.    I see from a recent posting that a timing cable was not
connected -- sounds like this could do it? 

    Antennas 14 and 16 have slow phase changes essentially identical to
the adjacent VLA antennas.  All is well with these. 

    As usual, there were big phase jumps between scans at the same
frequency for the EVLA antennas.  I had changed frequencies in between. 

    Amplitudes for antenna 13 (IFs A and C) were normal at L-band.  At
C-band, and despite the use of referenced pointing (which returned rather
suspicious solutions), amplitudes were down by 30%, and fluctuated
significantly.  It looks like we're on the half power point here. 

    When a few minutes of time are available, I'll check out
the state of the system, now that various changes have been made to 13
and 14.