  In their catalogue of pulsars' radio spectra, Swainston et al. (2022, PASA,
39, e056) distinguish between five different forms of these spectra: those that
can be fitted with (i) a simple power law, (ii) a broken power law, (iii) a
low-frequency turn-over, (iv) a high-frequency turn-over or (v) a double
turn-over spectrum. Here, we choose two examples from each of these categories
and fit them with the spectral distribution function of the caustics that are
generated by the superluminally moving current sheet in the magnetosphere of a
non-aligned neutron star. In contrast to the prevailing view that the curved
features of pulsars' radio spectra arise from the absorption of the observed
radiation in high-density environments, our results imply that these features
are intrinsic to the emission mechanism. We find that all observed features of
pulsar spectra (including those that are normally fitted with simple or broken
power laws) can be described by a single spectral distribution function and
regarded as manifestations of a single emission mechanism. From the results of
an earlier analysis of the emission from a pulsar's current sheet and the
values of the fit parameters for each spectrum, we also determine the physical
characteristics of the central neutron star of each considered example and its
magnetosphere.
