By observing the ionospheric F region simultaneously in multiple beams with the middle and upper atmosphere radar, we have been able to track the passage of gravity waves and measure their propagation characteristics. Here we investigate the dispersion relation for these waves. This relation varies widely from day to day, even on two successive magnetically extremely quiet days. On average, however, we find that the wave horizontal phase trace speed is about 200 m/s for periods from 60 to 130 min with little variation with solar or magnetic activity. There is some indication that the speed increases slightly from equinox to winter. ¿ American Geophysical Union 1995