Spectra of HF-enhanced ion line and upshifted and downshifted plasma lines were obtained by a multiple-pulse technique (9 pulses) and by a technique using pulse-to-pulse correlation (512 pulses) with a short (about 1 ms) interpulse period for high frequency resolution. Observations using the multiple-pulse technique suggest the presence of two different types of spectral features. One type has a spectral width typically greater than 1 kHz, and another type a width much less than 400 Hz, the frequency resolution of the multiple-pulse technique used. Observations using pulses with a short interpulse period show the width of the narrow spectral features to be in the 20- to 60-Kz range. The results are in good qualitative agreement with predictions of the linear theory of parametric instabilities excited by two pumps. Observations of the narrow spectral features can be used to measure the line-of-sight component of ionospheric drift velocities of the electron gas with an accuracy of about 2 m/s.