Normalized sideband gain as a function of LO frequency and mixer bands (different colors)  −    G_ssb = 0.5 corresponds to equal gain in USB and LSB. The different gases used are indicated by the different symbols: ¹²CO circles; ¹³CO squares; CH₃CN diamonds; H₂O upward pointing triangles; OCS downward pointing triangles. Measurements in horizontal polarization have a black outline. The filled boxes delineate all data falling within the first and third quartiles. See text for caveats.