Data collected with the AN/TPS-71 relocatable over-the-horizon radar (ROTHR) has been used to validate the RADARC Model. For the first 10 days of January, April, and July, 1200 and 0000 UTC, the vertical ionograms, oblique backscatter soundings, radar ground backscatter amplitudes, and noise levels have been compared with model predictions. The differences between the model and median h'f soundings are small enough to have negligible effect on predictions. The coverage predicted for oblique backscatter soundings agrees well with observed median data except for sporadic E effects which were underestimated. Medians of observed ground backscatter levels agree fairly well with predictions. The actual noise that controlled radar performance was the most significant deviation from the model; all nighttime and January day noise was higher than that predicted, and this was due to spread-in-Doppler clutter appearing as noise.