A method and frequency converter for a radio rapid frequency signal scanning and including a local oscillator signal synthesis source (112) producing a local oscillator signal (502) with local oscillator bursts (210). The local oscillator bursts (210) contain pulse width modulated RF frequency pulses (602). Each local oscillator burst having, for a pre-determined duration, RF frequency pulses within an effective amplitude above a pre-determined threshold (260). Each local oscillator burst (210) having also has effective amplitude pulse shaping envelope (504) that reduces at least one frequency domain component magnitude (310) of the local oscillator signal (300). A radio frequency mixer (110) receives an RF signal input (104) and the local oscillator signal to produce an output signal (160) at a frequency related to a combination of a frequency of the RF signal input and a frequency of the local oscillator signal.