We investigate mode conversion of propagating upper hybrid waves to resonantly excited nonpropagating electrostatic electron cyclotron harmonic (Bernstein) modes and show that it can explain the absence of stimulated emission of sideband electromagnetic radiation from the ionosphere in the kilohertz frequency range less than the input pump frequency when the latter is very close to or at harmonics (third and above) of the electron cyclotron frequency. The results are in good agreement with the ionospheric heating experiments conducted at Troms¿ (Norway) as well as at Arecibo (Puerto Rico). ¿American Geophysical Union 1990