Upper panel: spectra of the fluxes of the SZE-21 cm ΔI_mod (in units of μJy and in absolute value with the solid lines) and the SZE for a non-modified CMB ΔI_st (dashed lines). Lower panel: absolute value of the difference between the SZE-21 cm and the standard SZE for a non-modified CMB. Both panels are using for the modified CMB the fiducial model without DM (solid line in Fig. 1). Both panels are for thermal plasma with temperatures kT = 20 (green), 15 (black), 10 (red) and 5 (cyan) keV, and calculated for τ₀ = 5 × 10^-3, θ_c = 300 arcesc, β = 0.75, θ_max = 10θ_c, compared with the SKA-50%, SKA1-low, and SKA 2 sensitivities for 100 kHz bandwith, 1000 h of integration, 2 polarizations, no taper, no weight (thick lines).