Visibility amplitude versus time at different calibration stages. The amplitudes on the ALMA-LMT baseline observing a 4 Jy point source are shown. The coloured data points represent the 64 channels spanning 2 GHz before calibration, with a time resolution of 1 s. After amplitude calibration, the visibilities are averaged in frequency and down to a time scale of 10 s (grey points). Network calibration is then applied to the averaged data, with a solution interval of 10 s (black points). The amplitude attenuation factors exp(τ) at the centre of the band for the two stations are overplotted as blue lines.