[evlatests] S-band PDif wobbles gone from ea16

[Rick Perley]

    I've reported earlier on the (almost) ever-present wobbling of the 
PDif values from ea06 and ea16.    For ea06, the wobbling is seen in 
both polarizations, but in 'anti-phase'.  For ea16, the 'wobbling' was 
only on the RCP side.    For both antennas, the wobbling is not seen in 
the PSum. 

    ea16's S-band receiver was replaced with the spare a couple days 
ago.    I had a test run last night, so can look at the current 
situation.   The PDif values for both polarizations are now beautifully 
steady.  There are no variations on the RCP side.  All is as it should be. 

    Perhaps more curious is that the wobbles in ea06 are barely visible 
on the LCP side (IFs C and D).  They are present in the RCP with the 
usual strength (a few percent of the average).