evenly allocated among the three frequencies. At each frequency the effective observing time on 3C 48 is about 2.6 hours. The data were recorded at four observing frequencies (IFs) at 1.5 GHz and at two frequencies at the other two bands, initially split into 16 channels each, in full polarization mode. The total bandwidth in each case was 32 MHz. The detailed data reduction procedure was as described by Worrall et al. (2004) and was carried out in [aips]{}. We used models derived from our 1996 observations to facilitate fringe fitting of the 3C 48 data. Because the source structure of 3C 48 is heavily resolved at 4.8 and 8.3 GHz, and missing short baselines adds noise to the image, the initial data were not perfectly calibrated. We carried out self-calibration to further correct the antenna-based phase and amplitude errors. This progress improves the dynamic range in the final images.

Polarization calibration was also carried out in the standard manner. Observations of our bandpass calibrator, 3C 345, were used to determine the R-L phase and delay offsets. The bright calibrator source DA 193 was observed at a range of parallactic angles and we used a model image of this, made 