Discrepancy among the radiometers of the same frequency in the height of the power spectrum C_ℓ near the first peak. For a discussion of how these values were computed, see the text. Inset: to better understand the linear trend in the 70 GHz radiometers, we have computed the weighted average between pairs of radiometers whose position in the focal plane is symmetric. The six points refer to the combinations 18M/23M, 18S/23S, 19M/22M, 19S/22S, 20M/21M, and 20S/21S, respectively. All six points are consistent with zero within 1σ; see also Fig. 6.