In low frequency observations the astronomical signal has to compete
with the unwanted effect of interfering sources, which can be
internally or externally generated RFI or strong sources in the
sidelobe. We discuss a few techniques to remove unwanted large scale
undulations resulting from a strong source in the sidelobe or RFI
spots in the data. We give detailed recipes for the data reduction
within AIPS. These techniques were developed during the reduction
of an observation of Coma Berenices with the 74 MHz system of the
VLA (Enßlin et al. 1999 [
1]). They should be used
in combination with the `
Low Frequency Data Reduction
Tutorial' of Kassim & Perley (1999) [
3].
