Comparison of the chromatic activity windows for FRB 20121102A (red) and FRB 20180916B (blue). The solid lines represent the power-law fits to the peak phases of each FRB activity window. For FRB 20121102A, the fit is characterised by A_μ = −0.195 ± 0.073 and B_μ = 0.470 ± 0.024 (red line), and for FRB 20180916B, the fit is given by A_μ = −0.186 ± 0.018 and B_μ = 0.475 ± 0.006 (blue line). The shaded regions represent the FWHM of the active windows.