Effect of increasing f_th at a reference frequency of 3 GHz (top panel) and 6 GHz (bottom panel) on the observed spectral index ${\alpha }_{6\mathrm{GHz}}^{3\mathrm{GHz}}$. Here we consider the simplest radio-SED composed of a thermal and non-thermal component as shown in Eq. (1). The different coloured lines show the effect of increasing the α_nth from the canonical value of −0.8 to up to −1.5. In both the panels the dashed horizontal lines show the value of ${\alpha }_{6\mathrm{GHz}}^{3\mathrm{GHz}}=-0.64$ for f_th = 0.1, and α_nth = −0.8 from Eq. (1). And the dashed vertical line shows the expected value of the thermal fraction at 3 and 6 GHz for such a radio spectrum. We also show our LzLCS observations on this plot in blue points.