Abstract: Electromagnetic interference ("EMI") is reduced in a CRT video display system by spreading-out the EMI-producing spectra present in the video pixel data and/or clock signals. A clock dropping circuit coupled between the display generator main oscillator and the timing generator periodically phase-modulates the timing generator clock signal such that it comprises N phases, where N.gtoreq.2. As a result, each horizontal line of video data and the horizontal synchronization signals is phase shifted. This dual-shifting effect eliminates display image distortion that would result if only the video signal were shifted. Video distortion is further minimized by deriving the horizontal and vertical synchronizing signals from a common constant clock. EMI energy associated with each clock harmonic is spread by a frequency amount .DELTA.f proportional to the rate of phase change in the clock signal, the rate of phase change exceeding half the bandwidth f.sub.m of a standard EMI measurement reference window.