Low-flux density sample experiences an increasing influence of flat-spectrum sources. Top and bottom left: α_1.4/4.85 and α_4.85/10.45 index distribution for the high-flux density sample (HF). Top and bottom middle: α_1.4/4.85 and α_4.85/10.45 index distribution for the low-flux density sample (LF) (two sources – not shown here – have a α_4.85/10.45 below −3). Top and bottom right: α_1.4/4.85 index distribution for the low-flux sources (LF) without and with 10.45 GHz measurements.