[evlatests] Temporal phase drifts

[Vivek Dhawan]

The slow drifts are seen in VLA data as well. There are 2 kinds of
phase variation:

1. purely as a function of elevation, best seen in a run that goes
over many sources in a short time. the C band widar data and C band
VLA data taken in parallel show very similar effects.
A long track probably has this as well, but its mixed in with (2)

2. Slow drifts from the L302 of which there are several versions;
the latest have the drift removed, but its worth someone (Hichem?)
checking if antennas 3,8,9,24,27 have older versions. Also, the
AC and BD drift at different rates if they have different versions
of L302 on the 2 IFs (VLA data).


Also, from the round-trip phase -

Michael Rupen wrote:
>>    Vivek mentioned in the WIDAR Monday meeting that although phases now
>> connect beautifully, there is some evidence of phase drifts.  I've
>> checked this with the 6-hour C-band database that was taken on
>> Saturday.  The results, based on using antenna 28 (N8) as reference:
>>
>>    Antenna 3's phase (both polarizations, all subbands) declines
>> steadily by 60 degrees through the time interval.
>>    Antenna 24's phase (both polarization, all subbands) declines
>> steadily by 70 degrees throughout.
>>    Antennas 8, 9 and 27 all have a similarly-shaped rise in phase by
>> ~20 degrees, occuring over the final hour only.
>>
>>    All other antennas show zero drifts.
>>
>>    Antenna 3 is at E9, antenna 24 at W5, antenna 8 at N1, antenna 9 at
>> E6, and antenna 27 at E3.  There seems to be no simple explanation for
>> these drifts on the basis of array position.
> 
> Is this seen for any antennas in the simultaneous VLA data?
> 
> Have the antennas listed here shown drifts in (e.g.) previous VLA baseline runs?
> 
>          Michael
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