[evlatests] More on 'Wobbles'

[Rick Perley]

    Barry noticed a possible geometric relation amongst the 
antennas/baselines that I reported on having the 'wobble' present, so I 
looked a little deeper.  There might be something here ...

    Seven baselines showed notable 'wobbles'.  For each of these the 
wobble amplitude reached a maximum -- it's clear that this maximum is 
because the 'wobble frequency' goes through zero, so the loss of signal 
due to the 1 second averaging is minimized. 

    Two baselines had their maximum (zero frequency rate) at transit.  
Both of these baselines are along the north arm.  The zero wobble 
frequency is thus at u = 0, when the fringe rate is zero. 

    Three baselines had their maximum at a large positive hour angle -- 
all three are aligned along the west arm, and again, the minimum wobble 
frequency rate occurs at or near u = 0. 

    Two baselines had their maximum amplitude at a large negative hour 
angle, and (you guessed it!), these baselines lie along the East arm.
    But the relation isn't perfect, for one of these two east-arm 
alignments is actually significantly skewed -- 2 x 10 is E2 x N3, so 
this is an azimuth midway between the north arm and east arm.  The 
maximum wobble amplitude on this baseline, if it should occur at u = 0, 
would have been at 07:28 IAT.  In fact, it was at 05:40 IAT -- nearly 
two hours earlier.