In order to correct for the baseline-based bandpass errors, the visibility data of the strong QSO 3c454.3 needs to be extracted from the uv data applied for antenna-based bandpass correction ( e.g. sgrb228a_rx0.lsb.tsys.bp) using uvaver:
uvaver vis=sgrb228a_rx0.lsb.tsys.bp select='source(3c454.3)' \ out=05aug1bl options=nocal,nopass
Then, using blcal, the baseline-based correction can be drived from 05aug1bl and be applied to sgrb228a_rx0.lsb.tsys.bp:
blcal vis=05aug1bl,sgrb228a_rx0.lsb.tsys.bp \ interval=5000 out=sgrb228a_rx0.lsb.tsys.bp.bl
The output file sgrb228a_rx0.lsb.tsys.bp.bl is the final uv data set which has been applied for the bandpass corrections. Note that blcal assumes a point-source model in the process of corrections for the baseline-based bandpass, i.e. any deviation from point source model of the source in the first input data (05aug1bl) might introduce errors. In addition, the point source used must be strong enough for calculating bandpass corrections with adequate S/N on each of the baselines.
After bandpass calibration, one might check up the spectra for one of the target sources using smauvspec:
smauvspec vis=sgrb228a_rx0.lsb.tsys.bp.bl \ select='source(SgrB2_M),ant(3)(4)' \ axis=freq,both device=/xs nxy=1,1
Fig. 3.9 shows the spectrum of baseline 3-4 for SgrB2_M. Note that the data in the uv data set sgrb228a_rx0.lsb.tsys.bp.bl output from blcal has been applied for all the bandpass corrections and there should no bandpass table attached to this data file. From this point, one can go back to smamfcal for antenna gain corrections.