An open loop frequency calibration algorithm is employed whereby frequency counters are utilized to provide frequency information concerning the difference in frequency between a local oscillator and a reference signal prior to obtaining phase locked operation of a phase locked loop (PLL). The frequency difference is then used to adjust the local oscillator's frequency to be changed by a value that is proportional to the frequency difference measured. Through adaptive calibration of the local oscillator's frequency prior to closed loop PLL operations, a substantial reduction in the amount of time required to obtain phase/frequency coherent operation of the PLL is realized.