[evlatests] TBRISK Dec 15 UT 2225 to 2303

[Terry Cotter]

Ant 4 has had a very subtle problem with bad baseline phases for a 
while. We are still working on it.

Chris Carilli wrote:
> but not at source changes?
> that would be consistent with what i saw last week.
> band changes lead to phase jumps, but the EVLA
> antennas do not jump together, ie. the phase jump is
> different for ant 14 and 16.
> cc
> 
> Walter Brisken wrote:
> 
>>
>> Yesterday I ran a simple continuum test file that switched between two 
>> sources and three bands in the following order to see when phases did 
>> not return to their correct value.  Except for the 5 minute first scan 
>> all scans were just under 2 minutes long.  Integration times were 3 
>> seconds.
>>
>> First the peculiarities of the data:
>> 1.    L-band IF B was dead on antenna 16.  All other bands/IFs worked.
>> 2.    Antenna 14 IF C had poor amplitude stability at C and X band
>> 3.    (Really weird!) VLA baseline 4-28, all IFs at X-band only were 
>> very noisy (but shows some sign of coherence), but 4-16 and 14-28 
>> looked fine.
>> 4.    Antenna 14, IFs B and D showed (both LL pols) showed no fringes 
>> for first scan, very weak fringes on second scan, and normal strength 
>> on subsequent scans.  IFs A and C were OK.
>>
>> Table of scans
>>
>> 0137+331  CC
>> 0136+478  CC
>> 0137+331  CC 0136+478  CC 0137+331  CC 0137+331  LL
>> 0137+331  XX
>> 0137+331  CC 0136+478  CC 0137+331  LL
>> 0136+478  LL
>> 0137+331  LL
>> 0137+331  XX
>> 0136+478  XX
>> 0137+331  CC
>> 0137+331  XX
>>
>> At every band change phases on EVLA IFs got phase jumps.
>>
>> Plots are available in /home/parallax/evla/tests/20051215 -- the 6 
>> postscript files are VPLOT outputs.  Red is for IF A / C for RR / LL 
>> respectively and Blue is for IF B / D for RR / LL.  No calibration has 
>> been done.
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> 
> 
> 
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