In a recent work, Matos et al. (1) , studying the unpaired electron wavefunction of the interstitial hydrogen atom ($ center) in SrF showed the convenience of the use of a molecular orbital scheme which takes into account both Pauli repulsion and covalence unambiguously. In this scheme covalence is introduced in a phenomenological manner, only with the 2p orbitals of the first neighbor F-ions, by fitting the experimental result concerning the magnetic dipolar interaction b for the first shell nuclei. There were two main purposes in that work: first, to compare the molecular orbital scheme, widely used in studies of weakly covalent complexes of transition'ion element (2), with the Heitler-London scheme used by Spaeth and Seidel (3) in their study of the H. center in alkali-halides and second, becauses there were different reports for the experimental values of the magnetic hyperfine constants of the second fluorine shell of this defect in SrF2, the authors tried to identify the correct one. In the present note we use the same molecular orbital scheme in the description of the unpaired electron of the defect in CaF and BaF The study of 2 2' the trend of the calculated results for the three crystals can be considered a s a good test f o r this phenomenological procedure.