Central cores of compact radio sources are believed to contain supermassive black holes accreting material from their vicinity which produce fast moving plasma in the form of directed beams (jets), with apparent opening angles ≥5° (Rees et al. 1981). In case, the jets are produced and their collimation is established on scales few times the SchwarzschiId radius (2m; m=GM/c2) of the central engine, deflection in particle trajectories in the curved spacetime () would be large enough to widen the beam and thereby reduce the particle density and effective luminosity in the beam (Fig.1).