We report B3LYP DFT calculations of trans H-bond scalar C-13-N-15 3-bond (3h)J-coupling constants using various basis sets on a model for peptide H-bonds formamide dimer. All four components to the J's (Fermi contact, FC, spin-dipole, SD, paramagnetic spin-orbit, PSO, and diamagnetic spin-orbit, DSO) have been calculated. These calculated couplings are reasonably independent of basis set except for small basis sets and are dominated by the FC terms. Other trans H-bond couplings (one-bond O-17-H-1 (1h)J; and the two-bond C-13-H-1 and N-15-O-17 (2h)J's) have also been calculated by the same methods. Their dependencies upon basis set, relative dominance by the FC terms, and potential utility for peptide structural studies are considered.