In common with all wideband ionospheric sounding systems the backscatter technique is susceptible to contamination by radio frequency interference. The eradication of such interference is imperative in systems required to automatically interrogate the backscatter sounder data base. This paper presents the results of the development of an algorithm designed for that purpose. The philosophy guiding the design is presented, together with the results of a computer simulation designed to simultaneously validate the proposed approach and derive an appropriate threshold. Details of the implementation are provided together with data demonstrating the effectiveness. The algorithm is capable of being implemented in any backscatter sounder system featuring an adequate digital signal processing capability.