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Bandpass shape not flat after mfcal - interference?

PostPosted: Fri Mar 11, 2011 8:41 pm
by danieljohansson
Sorry for asking a possibly simple question, but I have been struggling with this for a few days and none of my colleagues seem to know the answer.

I'm reducing 7mm data at 30.5 GHz, and I'm having some problems with the bandpass calibration. I used the source 0537-441 as bandpass-calibrator (flux density ~10 Jy @ 30 GHz).

I have attached the before and after-bandpass calibrator diagrams from uvspec to this message.

I perform the bp-cal with mfcal, stokes=xx,yy . The band is almost flat, but there are some "wiggles" at the 5% level, as well as a slope to some of the baselines. In the final spectra on my science target I can see wiggles too, perhaps coming from the bandpass shape.

Here is how the bp-cal looks in pgflag for the 1-3 baseline.
pgflag display for the 1-3 baseline
pgflag_bl13.jpg (258.52 KiB) Viewed 41901 times

These lines may be the reason for the bandpass shape. What can I do to improve?