A fully automated partial-reflection, spaced antema, winds system has been developed at Birdlings Flat (44°S), using real-time data processing on a miniconputer. This enables almost continuous measurement of the winds between 65km and l00km to be made. Optimal data selection criteria for this location, and the value of simplifications in the data analysis and collection, are examined. The seasonal variation of the prevailing wind is studied in detail. The circulation in the mesosphere is characterized by strong westward winds in summer, and more variable eastward winds in winter. The circulation in the lower thermosphere is in the opposite direction. Long-period wind oscillations are observed throughout the year, and an identification of some of these with atmospheric normal modes, is strongly suggested in summer. Baroclinic instability may also occur in the summer mesosphere. Stratospheric disturbances are found to have significant effects in the 65 - 100 km region. The variation of atmospheric tides with height end season is also examined.