During an ionospheric heating experiment using the European Incoherent Scatter Heater Facility on 10 July 1999, artificial backscatter was detected by the Scandinavian Twin Auroral Radar Experiment (STARE) 140 MHz coherent radar system. The STARE radar operations included for the first time multipulse observations. The autocorrelation function and power spectrum of the backscattered radar signal were observed to be characterized by a half-power correlation time 13 ± 1 ms or by a corresponding spectral width 47 ± 4 Hz. This spectral width is comparable to the width observed at much lower frequencies, at 46.9 MHz and 21.4 MHz. The spectral width may, in part, result from the spatial extent of the heated region and from the spatial resolution of the radar in connection with spatial gradients in the background electric field. An upper value of the turbulent diffusion coefficient derived from the observations is 4.5 m²/s. It is up to a factor of 10 larger than the classical coefficient. Apart from spatial effects the increase may be caused by increased electron scattering in the plasma waves excited by the heater activity.