Radio SED fitting to flux density points for example compact and extended sources. Upper panel: SED fitting to flux density points between 1 and 26 GHz for the compact example G032.7441−00.0755 (upper row of Fig. 1). Lower panel: SED fitting to flux density points between 1 and 11 GHz for extended example G035.4669+00.1394 (middle row of Fig. 1) by excluding K-band flux measurements. The best-fitting results for the electron density n_e and physical linear diameter diam are shown in the upper-left corner of each plot. The best-fitting SEDs for the whole sample are available in electronic form at the Zenodo via https://doi.org/10.5281/zenodo. 4293684.