A preamble detector for a Bluetooth Long Range includes a receiver for forming baseband samples from Bluetooth packets and a preamble detect controller for enabling and disabling power to the receiver. Where the preamble duration is Tcyc, the preamble detector turns on for a preamble detect time T1 and turns off for a duration T2, where T2=Tcyc−2*T1. A series of hierarchical decisions is made on sequentially increasing intervals of time based on an accumulated correlation result of correlating the baseband samples against a SYNC sequence to power the receiver back down before the end of the T1 period when the accumulated correlation result is below a threshold and continues to a subsequent correlation interval when the accumulated correlation result is above a threshold, where the threshold is established to have at least a 20% false alarm rate for preamble detection.