RFI mitigation for the Effelsberg-Bonn HI Survey (EBHIS)

A new L-band 7 feed array at the 100-m telescope is used to perform an unbiased, fully sampled HI survey of the whole northern hemisphere - the Effelsberg-Bonn HI Survey (EBHIS). The use of state-of-the-art digital Fast Fourier Transform spectrometers based on FPGAs - superior in dynamic range and allowing fast dumping of spectra - makes it possible to apply sophisticated RFI mitigation schemes. Based on the current status of the survey we discuss the RFI situation at the 100-m telescope and present a fast algorithm to automatically identify RFI in the raw data output from the spectrometer. Using simulations we show that it is feasible to detect more than 95% of all RFI in excess of 1 sigma amplitude with less than 1% false positives.