[daip] Ringing from BPASS

[lincoln greenhill]

Hi Eric,

> 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.

If I assume that an FFT is performed to effect the shift in frequency required
for VLBI data, then the problem be triggered by an erroneous value in
the highest channel of the transform spectrum (lag domain) - perhaps an
array dimension problem?

Best, Lincoln




-- 
Lincoln J. Greenhill               Harvard-Smithsonian Center for Astrophysics
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