Comparison of dipole amplitudes observed at different frequencies for the TGSS-ADR1, WENSS, SUMSS, and NVSS masked with ‘mask d’. A function f(ν) = A(ν/1 GHz)^m is fitted to the dipole amplitudes (solid lines), which results in A = (2.16 ± 0.53)×10⁻² and m = −0.51 ± 0.15 with χ²/d.o.f. = 1.23. Results of a power law and constant dipole amplitude fit excluding the TGSS are shown as dashed-dotted and dotted lines, respectively. Simulations for each survey coverage with the CMB dipole (dashed line) are shown as open symbols.