Observations are reported of a new upshifted stimulated electromagnetic emission (SEE) feature, termed broad upshifted structure (BUS). This wideband emission is found to be upshifted by up to 170 kHz above the pump frequency if the pump frequency lies in a frequency range far from a gyroharmonic frequency. The dependence of the BUS feature on the pump frequency and pump power, as well as its temporal evolution, are investigated. The experiments were carried out at the Sura heating facility in Russia by modification of the ionospheric F region, using a HF ordinary mode pump wave.¿ 1997 American Geophysical Union