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Effects of lightning‐induced generation of high‐frequency and microwave radiation are of great interest for studying fundamental physics of lightning and its applications for monitoring of the thunderstorm activity monitoring and protection of equipment against electromagnetic interference. Ultrawideband electromagnetic pulses (UWB EMPs) of spark discharges about 1 m long were detected in a frequency band of up to 10 GHz in laboratory experiments using a cloud of water droplets charged up to the electric potential exceeding 1 MV. Electromagnetic pulses with characteristic front buildup durations from 50 to 100 ps were produced by streamer flashes at the stage of leader propagation and the main stage of the discharge (i.e. the return stroke). Electric and magnetic fields of pulses were measured, and the radiation polarization was determined. The UWB EMP waveforms and the spectra obtained experimentally are consistent with colliding streamer models.