Analytical and numerical techniques are used to model multifrequency amplitude scintillation data recorded in the equatorial region at Ascension Island. In particular, the behavior of the temporal coherence interval of multifrequency amplitude scintillation recorded at VHF, L band and C band is studied. The data cover a wide range of perturbation strengths corresponding to scintillation indices (S4) in the range 0.05–0.25 at C band (4 GHz). The dependence of the 50% decorrelation interval of the amplitude fluctuations on wave frequency and scintillation intensity is compared to analytical and numerical simulation results that are computed using a phase screen model. The observations are found to agree closely with simulated scintillation generated using a two-component power law spectrum model for the ionospheric irregularities. A simple inverse relationship is found to exist between the correlation interval of saturated scintillations at VHF and the perturbation strength as measured by the C band scintillation index. The result is shown to be consistent with analytical results based on an asymptotic approximation to the covariance function for intensity scintillations.