The new generation of instruments at APEX have large bandwidths, up to 8 GHz per sideband, and many of them are 2SB, which means that you can get the two sidebands simultaneously during the same observation.
These are powerful features which allow the PI to strategically select the tuning frequency of the instrument so that it can cover two, three or more astronomical lines in the same setup.
We have created the instrument setup tool to help PIs finding the right tuning for the science goal of their interest, keeping in mind the large bandwidth. The tool allows to visualise simultaneously the atmospheric transmission over Chajnantor plateau and the frequency span covered by the different instruments. You can select the pwv content of the atmosphere and see where the strong atmospheric absorptions lie within your bandwidth