Waterfall plots of the complex visibilities and their Fourier transform. Top panel: amplitude of the visibilities. The RFI can be seen at 39.78 MHz. Bottom panel: Fourier transform of the visibilities. If the visibilities are dominated by a point source in the array tracking center, then this should be a delta function centered at 0 delay and 0 fringe rate. In this case there is some time variability in the data, which produces a spread along the fringe rate.