Postcorrelation radio frequency interference excision at low frequencies

We present examples of radio frequency interference from our experience with editing data from the Very Large Array and Very Long Baseline Array at frequencies of 74 and 330 MHz and discuss postcorrelation excision schemes commonly used at low radio frequencies (<1 GHz), including those employed for targeted observations, as well as broader brush automated schemes appropriate for surveys and other large data sets. We elaborate on the strengths and weaknesses of currently employed procedures, with an eye to providing a summary of existing methods for those developing future, more sophisticated postdetection data editing algorithms as well as new low-frequency instruments such as the Long Wavelength Array and Low Frequency Array.