An algorithm to acquire a desired signal of unknown direction and waveform and to steer nulls to jammers by a process of sequential selection and testing of auxiliary beams in a sidelobe canceller is proposed. The receiver must be able to recognise the desired signal when its input SNR exceeds some given threshold of around 10 dB. For weak desired signals, the achievable output SNRs approach those obtained by the beamformer in the absence of jamming, but a saturation effect occurs as input signal power increases; output SNRs saturate relatively early and become dispersed in value, although remaining quite useable. Performance against jamming in diffuse multipath conditions typical of the urban environment is evaluated with fairly satisfactory results. Comparison is made with the competitive techniques of eigenvector steering and the use of a linearly constrained adaptive beamformer with an augmented sample correlation matrix diagonal.