[evlatests] Strange Tsys

[Rick Perley]

    The best suggestion so far for the Tsys effect is dew on the feeds 
-- a clear night, with the DP very close to the air temperature.    
(This is confirmed by a look at the dewar temperatures -- which did not 
change throughout). 
    But we are supposed to have feed heaters to counteract this.  To 
explain what we see, all VLA, and most EVLA heaters would have been off 
during the run at both C and X bands.  But at K-band, it seems they were 
on. 

    Can this -- and did this -- happen?