Empirical distribution of the maximum S/N_PIMA of the fringe amplitude from PIMA fringe-fitting data on the SRT baselines n the C band (top) and K band (bottom) when no signal was present in the chosen search region (blue points). The red curve shows the fitted theoretical probability distribution. The shift in the maximum position is mainly due to the different size of the search space: C band fringe-fitting was carried out first and therefore a larger search space was used than in the K band.