[evlatests] Some WIDAR testing results

[Michael Rupen]

This sounds like the sort of phase jumps Vivek has been seeing in long
observations of single sources.  We'll have to sort those out before
dealing with multiple targets.  Vivek will present those results at
tomorrow's testers' meeting.

A few other comments are interleaved below.

>    Six sub-bands at a single polarization were provided (Michael will
> have to explain why there were not eight).


We have 37 working chips accessible on the Baseline Board (BlB).  Currently 
I've got things set up the simplest way possible, which uses one chip per
baseline per subband.  4 antennas ==> 6 baselines; 37/6 = 6 1/6, so
we get 6 subbands with 1 chip left over (set to do autocorrelations
at the moment).


>    The identification of the antennas in the AN table is incorrect:
> Antenna 1 is actually 17 (on W48), antenna 2 is actually 18 (on N16),
> antenna 3 is actually 23 (on E72), and antenna 4 is actually 26 (on N48).


This is a known limitation of moving from the Science Data Model (SDM) to 
AIPS.  We can either transfer the antenna pad (e.g., W48), or the antenna name 
(e.g., EA17), but not both.  The pad location seems more interesting, so 
that's what we're sending at the moment.


>    Antenna 3 (actually 23) gave perfectly zero amplitude (i.e. neither
> signal nor noise) for sub-bands 1, 2, and 3.


This is a known problem, due to the difficulties with Station Board
(StB) 2, which is hooked up to antenna 23.  I've tweaked the correlator
setup so we should get 4 subbands from now on, with only 1 and 2 gone,
but do not propose going further than that.


>    CALIB was then run to determine the antenna-based amplitude and
> phases for each observation.  There was difficulty in determining
> solutions for sub-bands 1, 2, and 3 -- very likely a result of there
> being only three functioning antennas.


It may help to explicitly flag those subbands for antenna 3 (= 17).
In at least one of the subbands I believe the data are neither missing nor
identically zero, but rather some tiny value; if so this could easily
muck up both BPASS and CALIB.



>    Examination of the calibrated phases showed normal distributions
> about zero degrees and unit flux -- good, but not overwhelming evidence
> that closure is being well maintained.  (Only 'good', because the SNR is
> not as high as we need to do an exact test).


Note that CLPLT plots the closure quantities directly; though it has not
been exercised to nearly the extent of programs like CALIB.



Cheers,

            Michael