[daip] Ringing from BPASS

[Eric Greisen]

Ingyin Zaw wrote:
> Hello,
> 
> The ringing problem I was having seems to be caused by POSSM (instead of 
> the solutions from BPASS). When I look at the scan on which I ran BPASS, 
> with doband 1 in POSSM, I see ringing in baselines to Ant 12 (VLA phased 
> array), strongest in the FD-Y and GB-Y baselines. However, when I apply 
> the BP table with SPLAT to the data and look at the same scan in the SPLAT 
> file with POSSM, it shows no ringing.
> 
> Here are two files for testing:
> (1) BK114A_2145_BP.FITS: contains the scan on which I ran BPASS and 
> the BPASS table (BP 1).
> (2) BK114A_2145_SPLAT.FITS: File (1) with BP1 applied using SPLAT.
> 
> Note: Both files have CL tables from previous calibrations. Applying or 
> not applying a CL table does not change the presence/absence of ringing.
> However, if you'd like to use a CL table, please use CL 7.
> 
> To get the files, please ftp from:
> cfa-ftp.harvard.edu
> USER: anonymous
> PASS: <youremailaddress>
> cd incoming/lincoln


I have looked at your data a bit more.  There seems to be a subtle 
difference between the BP table attached to the fits file with only 
2145+067 (256 chan) and that attached to the fits file containing a 
number of sources.  The BP table attached to the 1-source file causes 
the ringing whether applied by POSSM or SPLIT followed by POSSM on the 
data of the 1-source file or the data of the n-source file.  The BP 
table of the n-source file does not cause ringing when applied to either 
data set which, I suspect, is the cause of your theory that SPLIT fixed 
things.  How the BP table became different is a good question.  Forcing 
the software to ignore the VLBI shifting, the "calibrated" data are 
nearly the same with both BP tables except for the outermost couple of 
channels.

Eric Greisen