From left to right, beam maps of A1, A3, the combination of the 1 mm arrays (A1 and A3), and the 2 mm array (A2) are shown in decibels. These maps, which consist of the normalised combination of four beammap scans of bright point-like sources, are in horizontal coordinates. They represent a zoom in the inner part of larger maps that cover a sky area which extends over 10′. The solid lines and arrows highlight some noticeable features. Red circle in the A1 map (first panel): diffraction ring seen in 1 mm maps (the spokes are presumably caused by radial and azimuthal panel buckling (Greve et al. 2010); orthogonal yellow lines in the A2 map (rightmost panel): diffraction pattern caused by the quadrupod secondary support structure (prominently seen in A2 map); yellow arrows in the A3 map (second panel): pattern of three spikes seen in 1 mm maps of unknown origin; yellow arrows in A2 map (fourth panel): four symmetrical spikes of the first side lobes; pink ellipses: four spikes seen in A2 maps.