[evlatests] feature of VA mode scans on the VLA

[Amy Mioduszewski]

I did a test (ty010b) of switching between VS and VA modes on the vla yesterday. 
  The test was at C-band on a very bright source (BLLac), so had very high SNR, 
and used 3 sec averages.  Every time I switch to VA mode, it takes 2 
integrations to phase up, then for 3 integrations all the phases are 0, then for 
3 integrations all the phases jump to another value, then after those 
integrations the phases come back to 0 for the rest of the scan.  Attached is 
plot showing this as well as the amplitudes.  The jump is also different on the 
different IFs.  It happens in all the VA scans in the project and with all types 
of antenna pairs.  I know that the phases are applied at 10 second intervals, 
could the second application somehow be getting the wrong correction?

Amy
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