Expected coherence improvement ratio as established using the phase rms as measured over the entire bandpass observation compared to the ratio of the dirty image peak flux values of the bandpass source (left) and against the ratio of S/N values from the cleaned images of the bandpass source (centre). The right figure shows the ratio of the dirty image peak fluxes compared with the ratio of the S/N values from the cleaned images. The symbols and colours are as Fig. 4 and the dashed line indicates a 1:1 relation.