[evlatests] Tuning and Polarization at Q-band

[Rick Perley]

    We also tried to determine tuning and polarization across Q-band, 
along with K-band.  For Q, the frequencies attempted ran from 40.025 
through 50.025 GHz. 

    Antennas 11, 13, and 23 were out, as reported earlier.  Antenna 19 
has no receiver.  This left 7 antennas working. 

    Referenced pointing was attempted twice -- both failed, for reasons 
not understood.  The consequence of the failures were easily seen for 
antennas 16 and 24, which clearly wandered well off source during the 
2-hour run. 

    Good fringes were seen for all tunings between 40.0 and 46.0 GHz.  
The two high-frequency pairs (47/48, and 49/50 GHz) fringed weakly -- 
especially weakly at the 50 GHz.  Not especially surprising, given the 
high O2 absorption. 

    Polarization calibration was done, and for the frequencies from 40 
through 48 GHz, reasonable solutions were found.  D-terms are typically 
5% or better -- however, the reliability of this result is certainly 
questionable, given the poor SNR, and uncertain pointing.