[evlatests] X-Band Sensitivity, over the weekend

[Rick Perley]

    I've carefully reduced the fast-continuum data taken Saturday 
morning.  Observations
were made of a strong calibrator, 3C147, and an adjacent piece of blank 
sky, at
X-band. 

    The relative sensitivities of the antennas were determined by 
looking at the amplitude and
phase rms while on the strong source, and the amplitude rms while on 
blank sky. 

    All results give the same story:  Antennas 14 and 16 were notably 
worse than
good VLA antennas, at X-band.  The increase in rms was by a factor 1.5 to 2
for baselines with 14 or 16 against a good VLA antenna, and by a factor 
nearly
4 for 14 against 16.  This was true for all four IFs. 

    So this sounds bad.  However, there *may* be a simple explanation.  In
reviewing the back-end Tsys values, I see that both antnnas 14 and 16 have
reported Tsys values between 65 and 140 K (depending on IF).  These are
too high by a factor of 2 to 4.  Most VLA antennas are near 35K. 

    Why the high Tsys for the EVLA antennas at X-band?  I have no answer.
The weather was clear at the time.