Example spectra of a soft sample PS source (top) and a hard sample PS source (bottom). The flux densities of LoLSS (blue square), VLSSr (red circle), LoTSS-inband spectra (purple diamonds), LoTSS (green left-pointing triangle), TGSS (brown right-pointing triangle), NVSS (indigo downward-pointing triangle), and FIRST (pink upward-pointing triangle) are plotted where available. The black curve represents the generic curved model from Eq. (3), which was fitted to the LoLSS, LoTSS, VLSSr, TGSS, and NVSS data points. The power-law fits used to determine α_low and α_high are shown in orange.