PULSE CAL TABLE ISSUE:

If you do not use the Pulse Cal data when processing data from the VLBA
correlator you can ignore this.  The pulse calibration is normally done
with the procedure VLBAPCOR (loaded with VLBAUTIL).  It is also invoked
for continuum observations in VLBAPIPE.  The task that does the job is
PCCOR.

A significant number of cases have been found where a few entries in the
PC, or Pulse Cal, table provided with distribution data files from the
VLBA correlator are assigned to the wrong antenna.  Such data can be
spotted by plotting (SNPLT) the pulse cal phases for each antenna.  If
there are sudden jumps on some antenna, there is likely to be
incorrectly assigned data.  That data will probably have a pattern of
phases over channels that matches some other station's normal data.  The
cure is to get rid of the original PC table, download the cal file
(which has a name like bw523cal.vlba.gz) from NRAO, run VLOG, and run
PCLOD to load a new PC table.  Data acquired through that path has not
shown the problem.  To find your cal files, go to
http://www.vlba.nrao.edu/astro/VOBS/astronomy/ and search for the data
on your observation by going to the right month, then the obs code.

It is unlikely that this problem will be fixed for data files from the
hardware VLBA correlator.  The software correlator under development
will likely use a different data path, more like the cal file, for such 
monitor data and should not be subject to the problem.