A computer simulation of the Urbana, Illinois, meteor radar is performed to estimate the accuracy of the data analysis procedures in determining upper mesospheric tides. Various wind models such as planetary waves, gravity waves, and turbulence are tested and it is found that for reasonable values of atmospheric variance the two-dimensional standard deviation of the tidal estimator is at most 8 ms−1. The observed variability of the tides at Urbana during March 1980 exceeds the variability of a modeled steady-state tide, and the nature of the observed variability suggests a non-linear interaction of the tide with gravity waves and/or planetary waves. The semidiurnal tide also exhibits phase fluctuations indicating the possible presence of a transient S2,3 mode.