[evlatests] C-band sensitivity

[Rick Perley]

    Finally, I reviewed the amplitude stability (i.e., dropouts) and 
sensitivity of
the C-band data from last night.

    The peculiar, short (400 msec) dropouts are evident in both 
antennas, with
the same timing characteristics:  occurances are always separated by 10 
seconds,
never last more than one integration, and do not occur on all scans.  
Occurances
between 14 and 16 are not obviously correlated,, but occurances on one 
antenna
are always on all four IFs. 

    Sensitivity, as judged by the calibrated amplitude rms, is 
disappointing:

    Antenna 14 is poorer by about 20 to 30% from good VLA antennas. 

    Antenna 16 is poorer by nearly a factor of two! 

    The baseline 14 x 16 is worse by the product of those factors.  
(There was
only one common working IF in this database). 

    Note that the 6cm EVLA system should be nearly 2 X *better* than
VLA antennas. 

    The reported backend Tsys shows antenna 14 with a Tsys of nearly 40K --
far above the expected value of 24K. 

    Our 6cm sensitivity problems likely have far more to do with the 
receiver
noise than phase stability.