Power spectrum of the measured 70-GHz null maps for the differences D₁₂₋₃₄ (orange) and D₂₄₋₁₃ (light blue). The scatter is dominated by the measurement noise. The error bars are computed from 1000 Monte Carlo simulations from FFP8 noise. Negative values are due to the fact that the noise bias has been removed. For comparison we also plot the systematics-only spectra (red and blue).