In satellite positioning, a linear combination of 2 signals is used to eliminate the error due to the background ionosphere. State-of-the-art semi-codeless techniques rely on cross-correlation of the signals received at LI and L2. Thus it is important to determine how well these signals are correlated. Lack of correlation will also introduce range error in the 2-frequency correction. A significant factor in reducing this correlation is scintillation resulting from propagation through time-varying small-scale irregularities in the ionosphere. In the paper the estimated errors of the 2-frequency range determination and the correlation coefficients of the phases at 2 different frequencies are presented depending on the strength of the electron density fluctuations for 4 different pairs of frequencies (L1/L2, L1/L3, L2/L3, L1/L5). The results show that their dependence on the variance of the electron density fluctuations diverges from a linear relationship, the stronger are scintillation effects.