Top: solid line: the RMSF for the frequency sampling of the IC 342 observations. Dashed line: the Gaussian used as the restoring function in the RM CLEAN algorithm. Middle: dashed line: Input spectrum containing a delta function at φ = −15 rad m^-2 and a Faraday slab between +5 and +15 rad m^-2, both with amplitude of 1. Solid line: resulting spectrum using the frequency sampling of the IC 342 observations. The Faraday slab is almost completely depolarized. Bottom: the polarization as a function of λ² for the Faraday slab above. The wavelength range of the LOFAR HBA is between the two dashed lines and the simulated signal in this range is marked in bold.