A gaussian frequency shift keying (GFSK) detector comprising a multi-symbol detector; at least three Viterbi decoders, and a timing adjustment module. The multi-symbol detector receives a series of samples representing a received GFSK modulated signal which comprises at least three samples per symbol; and generates, for each set of samples representing an N-symbol sequence of the GFSK modulated signal, at least three sets of soft decisions values, each set of soft decision values indicating the probability that the N-symbol sequence of samples is each possible N-symbol pattern based on a different one of the at least three samples of a symbol being a centre sample of the symbol. Each Viterbi decoder generates, for each N-symbol sequence, a path metric for each possible N-symbol pattern from a different set of soft decision values according to a Viterbi decoding algorithm. The timing adjustment module generates a timing adjustment signal based on the path metrics generated by the Viterbi decoders to adjust the sample timing.