Effect of the gain modulation factor (GMF) on sky and load signals for flight data. The upper and middle panels show 10min of sky and load signals of the LFI27S-11 detector: they are highly correlated with clear signatures of low-frequency noise. After application of the GMF in taking the difference (Eq. (7)), such fluctuations are dramatically reduced, revealing the presence of a sky signal dominated by the CMB dipole (lower panel). Note the change in the y-axis scale.