[evlatests] X-band behavior, and antenna 13 baseline

[Rick Perley]

    I was released from the EVLA Advisory Panel meeting long enough to look
over some fresh (this morning) data taken by Ken.
    Continuum, 10 second averaging.    Tracking 3C84.    The primary 
goal was to
see if antenna 13's position is accurately known.  Duration was a bit 
less than
two hours.  Band = X. 

    1) Phase. 

    All antennas show 50 to 100 degree excusions certainly related to a warm
summer day in A configuration.  Timescales for these are 5 to 10 minutes.

    Antenna 13 looks no different than the surrounding antennas.  A   
critical eye
might detect a slope of ~50 degrees over the two hours, but other 
antennas show
not dissimilar gradients.  We conclude there is no large baseline error. 

    Antennas 14, 16, and 18 phases look fine, well within the norms for 
a day
like today. 

    2) Amplitude

    Antenna 13, IFs A and C are showing a 'bistable' state, with a 'low 
power'
state about 20% below (in power units) the high power state.  About 20% 
of the
records were in the 'low power' state.  IFs B and D were unaffected, and 
showed
excellent stability (much bettern than 1% variations), until near 
transit.  (See below)

    Antenna 14, IF A has an odd oscillatory gain variation, perhaps 2% 
in power,
on timescales of about 3 minutes.  Not seen in the other IFs.    
Otherwise, behavior
is good. 

    A few odd dropouts were seen on EVLA antennas -- rare. 

    All antennas (VLA and EVLA) showed long timescale (many minutes) drops
in gain near the end.  Looks like pointing, but the elevation was only 
75 degrees.
Perhaps wind -- but wind speeds were moderate.