We report the detailed characterization of a torsional vibration-rotation-tunneling band of the ortho-state of the propane-water dimer in the spectral region near 20 cm(-1) (0.6 THz). This work extends the previously reported studies with more than one hundred new transitions included in a combined fit with the 155 previously reported transitions in both the microwave and terahertz regions for this torsional band. More than six hundred transitions have now been recorded in the interval 500 and 810 GHz. (C) 2014 Elsevier B.V. All rights reserved.