[evlatests] PDif at Q-Band

[Rick Perley]

    At Q-band, all IFs from all antennas give good, reliable values for 
PDif which accurately remove all the clearly evident system gain 
changes.  The only exceptions are clearly caused by pointing errors.  (I 
can state this as I have the referenced pointing solutions in hand, and 
there is an amazing correlation between unusual pointing solutions and 
amplitude loss!  More on this later).