[daip] FILLM curiosity

[Eric Greisen]

Claire asked to have the velocity reference info checked more closely.
A particular experiment used fixed frequency on the first (cal) source
and then , supposedly, tracked frequency on the next source.  I beat
my way through AIPS stuff and got it apparently able to update the SU
table header for the tracking, but then found that the velocity
reference mode was given as

LV LF LV LF

apparently indicating that one IF pair (AC) was tracked and the other
(BD) not tracked.  Can this be the case?  How would the user request
it? 

Thanks,

Eric