Effect of ℓ_max parameter on 30 GHz TT white noise spectrum. We deconvolve the same data set with ℓ_max = 50, 100, 200, 400. To reduce scatter, we divide each spectrum by the white noise map spectrum, and show them in dimensionless units. The plot is based on 40 Monte Carlo realizations. The smooth lines in same colour show the predicted noise bias, constructed from harmonic white noise covariance matrix, for ℓ_max = 50, 100, 200. To bring them into units comparable with the Monte Carlo spectra, we divide them by the white noise level 3.2180 × 10^-15 K² (from Table 3). The last 2−5 unreliable multipoles are excluded for clarity.