Three examples of radio spectra. The low-frequency regime is covered by the GLEAM data (small red circles). Because the errors are relatively large, we also provide flux densities by rebinning five frequency channels (large black circles). The other flux densities are taken from the NVSS (black squares), FIRST (red squares), VLASS (red triangles), and GB6 (black triangles). Only data with a similar spatial resolution (i.e., from GLEAM, NVSS, and GB6, all marked with black symbols) are used to obtain the linear fit, which is represented by the green line.