A demonstration of deeper excision of periodic RFI using 2D DFT. Top panel: spectrogram of a 1.3 s of data from a GMRT observation of the bright pulsar J0437−4715, and with visible contamination by periodic (50 Hz) RFI. Second panel: 2D DFT of the data in the top panel. Third panel: 2D DFT after cleaning the data using RFIClean. Bottom panel: spectrogram after the periodic RFI are identified and excised using the 2D DFT. The red rectangles in the middle panels give the locations corresponding to the spin period of J0437−4715 and its first two harmonics, after taking into account the vertical offset caused by the inter-channel dispersive delays.