[evlatests] A few PDif problems at C-band

[Rick Perley]

    Overnight C-band data shows the following:

    ea03, in IF 'B':  The PDif values are in three states.  By far the 
most numerous is the center one -- the values look reasonable.  But 
there are small numbers of higher and lower values.   Easy to edit, and 
not a big deal at the moment. 

    ea14, in LCP (all 16 subbands):  There is no switched power at all.  
Only noise, with the expected dispersion.  *** This problem needs to be 
addressed ***

    ea15, in the highest-frequency subband (6.11 GHz), on all antennas.  
The PDif values are very strange, even negative on some antennas.  This 
is clearly due to the RFI in that subband, but for whatever reason, the 
behavior amongst the antennas is highly variable.  More study of this is 
needed.