[evlatests] S-band PDif variations on ea06L and ea16R

[Rick Perley]

    A (hopefully) useful addendum:

    The anti-symmetric variations are only seen in the AC IFs.  That is, 
only in ea06C and ea16A.  
    There may be a very faint version of this on the B-D side, but it is 
at the 1% level, or less.  This suggests that the phenomenon is not 
created in the receiver. 

    A minor correction:  The amplitude of the effect in ea06C is 5%, not 
10% are reported yesterday.