Ratios of S/N and TOA uncertainty values for PSRs J1730−2304, J1744−1134, and J1857+0943 as a function of time. The values are derived from NUPPI pulse profiles observed at 1.4 GHz and calibrated using the SINGLEAXIS method (“no corr.”) and the improved method described in Sect. 2.2 (“corr.”). For each pulsar, the top panel (blue points) shows the ratios of the S/N values and the bottom panel (orange points) shows the ratios of the TOA uncertainties. Individual observations were fully integrated in time, and integrated in frequency to form eight subbands. TOAs were extracted from the observations using the MTM technique. See Sect. 3.2 for additional details about the data preparation.