[evlatests] X-band holography phase

[Rick Perley]

    I reported yesterday on a 'holography' test using 3 different 
BW/Fluke settings, at X-band.  In summary, the 50 MHz BW gave no phase 
irregularities.  The 25 MHz BW gave a single phase jump, of about 120 
degrees.  The 12.5 MHz BW gave three jumps, all of 180 degrees.  All 
jumps occurred in the middle of scans. 

    This morning, I repeated this test, but added two further BW/Fluke 
combinations.  I thus had:

    BW = 50, Fluke = 100, 200
    BW = 25, Fluke = 112.5, 212.5
    BW = 12.5, Fluke = 118.75, 218.75
    BW = 6.25, Fluke = 121.875, 221.875
    BW = 3.125, Fluke = 123.4375, 223.4375.

    The results are quite remarkable (and inexplicable, given the 
history of this exercise) ...

    *** No phase jumps of any kind ****  at any bandwidth! 

    Only one single phase oddity in any EVLA antenna -- antenna 18 had a 
short-duration, parabolic-like phase deviation, lasting perhaps 20 
seconds, which smoothly deviated from the starting value, then smoothly 
returned. 

    Otherwise -- perfection! 

    So -- what are we doing right, suddenly?