A receiver for a wireless signal transmission system using digital amplitude modulation using a base band signal having a symbol clock frequency, the receiver comprising: an input for connection to an antenna for receiving a wireless signal; a reference generator (208, 210) for generating a local reference frequency signal; a mixer (204, 206) arranged to mix the local reference frequency signal with a received signal to extract the base band signal; a high pass filter (212, 214) arranged to receive the output of the mixer and to suppress a DC component of the extracted base band signal; an amplifier (220, 222) arranged downstream of the high pass filter; an analogue-to-digital converter (224, 226) arranged to convert the output of the amplifier into a digital signal; a digital signal processor arranged to receive the digital signal from the analogue-to-digital converter and configured to extract symbols from the digital signal; and a base band signal rotation detection circuit (240, 440) arranged to detect rotation of the base band signal upstream of the high pass filter and having an output (250, 252) in communication with the digital signal processor, wherein the digital signal processor is further configured to determine a symbol clock phase by generating a coarse estimate of the symbol clock phase using the local reference frequency signal, or a reference frequency signal derived therefrom, and correcting (320, 324) the coarse estimate of the symbol clock phase based on rotations of the base band signal detected (318, 322) by the base band signal rotation detection circuit, to determine that the symbol clock phase corresponds to a full symbol clock period and to output an event signal used in relation to the extraction of symbols by the digital signal processor whenever the full symbol clock period is determined. an input for connection to an antenna for receiving a wireless signal; a reference generator (208, 210) for generating a local reference frequency signal; a mixer (204, 206) arranged to mix the local reference frequency signal with a received signal to extract the base band signal; a high pass filter (212, 214) arranged to receive the output of the mixer and to suppress a DC component of the extracted base band signal; an amplifier (220, 222) arranged downstream of the high pass filter; an analogue-to-digital converter (224, 226) arranged to convert the output of the amplifier into a digital signal; a digital signal processor arranged to receive the digital signal from the analogue-to-digital converter and configured to extract symbols from the digital signal; and a base band signal rotation detection circuit (240, 440) arranged to detect rotation of the base band signal upstream of the high pass filter and having an output (250, 252) in communication with the digital signal processor, wherein the digital signal processor is further configured to determine a symbol clock phase by generating a coarse estimate of the symbol clock phase using the local reference frequency signal, or a reference frequency signal derived therefrom, and correcting (320, 324) the coarse estimate of the symbol clock phase based on rotations of the base band signal detected (318, 322) by the base band signal rotation detection circuit, to determine that the symbol clock phase corresponds to a full symbol clock period and to output an event signal used in relation to the extraction of symbols by the digital signal processor whenever the full symbol clock period is determined.