Measured visibility “noise” due to the NVSS > 10 Jy sky as seen by the VLA C configuration without primary beam attenuation (left). The two solid curves show the fluctuation level with and without the inclusion of the Sun. The two dashed curves include the effects of time and frequency smearing and are overlaid with representative power-law approximations. Visibility “noise” per solid angle due to the NVSS sky (right). The rms contribution of NVSS sources, normalised to a one square degree field of view, is plotted as function of baseline length. Flux bins from Table 1 are shown individually with the labelled curves. The root squared sum of contributions of the bins <10 Jy is shown as the solid line, together with an overlaid powerlaw fit.