Integral source counts of the TGSS-ADR1, WENSS, SUMSS, and NVSS radio source catalogues, masked with ‘mask d’, as a function of flux density. We fit a function N(> S) ∝ S^−x (top) and a more sophisticated function dN/dΩdS ∝ xS^{−x − κlog₁₀(S/Jy)} (bottom) to the counts, which have equal step width in log₁₀(S/Jy). The fitted range depends on the flux threshold of the survey and extends for each survey over one decade.