Distribution of the Effelsberg sources with respect to the radio luminosity, luminosity of [O III] line, and the Eddington ratio. Top row–left panel: distribution of the radio spectral index α_{[4.85–10.45]} with respect to the radio luminosity L_1.4 GHz and the luminosity of [O III] line. Right panel: localization of the Effelsberg sources (low + high flux; orange points) in the plane of L_1.4 GHz and L_[OIII] with respect to the parent sample (grey points). Bottom row–left panel: distribution of steep, flat, and inverted radio spectral indices with respect to the radio luminosity L_1.4 GHz and the Eddington ratio η. Right panel: distribution of the Effelsberg sources (orange points) in the same plane as in the left figure with respect to the parent sample (grey points).