Abstract: In order to further study the Doppler characteristic of the ionosphere, mid-latitude HF observations of ionospheric Doppler frequency shift are reported, observing from an experimental installation developed by China Research Institute of Radio Wave Propagation, which operates at a 10-min sampling rate for ionospheric Doppler sounding at a middle latitude site(Qingdao Shandong, China).The unique time-interleaving technique used in this ionosonde provids a Doppler resolution of 0.039 Hz over a Doppler range of ±2.5 Hz at each sounding frequency via fast Fourier transform (FFT) processing. Doppler variations are present throughout the daytime, and a strong correlation exists between the day-time Doppler shift and the rate-of-change of f_oF₂.The ionograms are introduced as observed in the ionospheric disturbance and spread F. The time interleaving technique can be applied to other types of ionosonde as well as to other applications.