[evlatests] Xband switched cal

[Rick Perley]

    Finally -- X-band results.

    At this band, Cyg A increases system noise by about 50%. 

    There are almost no detectable problems with the switched power at 
this band.  Zero offsets can only be seen on two antennas (ea04 in LCP, 
and ea07 in RCP, both at the level of a few millicounts -- less than 
.01% of the power).  Expansion or compression of the PDif values when 
observing Cygnus A is undetectable in nearly all antennas, and in the 
few where it can be seen, it is very small (couple of percent). 

    Antennas with detectable compression or expansion are (all at very 
low levels):
    ea04, LCP (expansion)
    ea07, RCP (compression)
    ea19, RCP (expansion)
    ea26, LCP (compression)
    ea01, RCP (compression).