Multiple waveform repetition frequency (WRF), is introduced in this paper as a solution to the range/Doppler ambiguity in HF FMCW radars. The proposed pattern requires switching of WRFs while the target is being illuminated. The Chinese remainder theorem provides a rule for the selection of the WRFs which is determined by the maximum required unambiguous Doppler coverage. However, for HF radars other considerations with regard to ionospheric clutter need to be accounted for. The paper presents the necessary criteria for selecting the multiple WRFs and an example for sea-state application.