It is well known that intense HF-radiowaves of the ordinary mode transmitted from the ground enhance plasma waves near the reflection height in the ionosphere. These enhancements are observed as an increase in the returned power of radars having a wavevector equal to one half the wavevector of the enhanced plasma waves. It is expected that strong Landau-damping will suppress such enhancements if k&lgr;D≂0.25 (k and &lgr;D correspond to the wavevector of the Langmuir wave and the Debye-length) which was the case for Langmuir-waves detected by the EISCAT/UHF radar during a recent HF-modification experiment at Tromsϕ. Enhanced plasma waves were observed unexpectedly at a low heater frequency of fHF=2.76 MHz. Enhancements at this frequency were not observed during previous attempts and were believed to be damped too strongly to be observable. The observed power threshold can marginally be matched with theory under the assumption of low but not unreal electron and ion temperatures. The observed spectra indicate that the interaction is more intricate than expected under the given conditions.