Tuning setups of the NOEMA observations. Top panel: Atmospheric transmission curve at the zenith of the NOEMA site for the frequency range covered by our line survey. The red and blue lines show the transmission curves for PWV = 1 mm and PWV = 5 mm, respectively. Middle and bottom panels: Tuning setups, their sky (observed) frequency coverage, and the RMS noise reached in each spectral window for APM 08279+5255 and NCv1.143. For display purposes, we smoothed the spectral resolution to 50 MHz, resulting in an RMS that is five times smaller than the noise level reported in Table 1 for the 2 MHz bins. As expected, the edges of the sidebands and the conjunction channels of the two spectral windows within each sideband exhibit large RMS values.