A fast radio burst leaves its source at every frequency at once, but the ionised plasma it crosses on the way to Earth slows low frequencies down more than high ones. The result — recorded as a "dynamic spectrum" — is a diagonal sweep whose curvature depends only on the dispersion measure (DM), the integrated free-electron column along the line of sight. This simulator renders that dynamic spectrum as a live 3D bar-height grid: frequency channels on one axis, time on the other, signal power as bar height and colour. Dial in a true DM and receiver band (CHIME, ASKAP or Parkes presets), trigger a burst, and watch the characteristic sweep race across the band. Then flip on dedispersion and slide a trial DM to reproduce the exact technique every real FRB and pulsar search pipeline runs: shift each channel by its predicted delay and watch the smear collapse into a single vertical spike the instant the trial matches the truth.