  If we assume that nuclei of extragalactic radio sources contain binary black
hole systems, the two black holes can eject VLBI components in which case two
families of different VLBI trajectories will be observed. Another important
consequence of a binary black hole system is that the VLBI core is associated
with one black hole, and if a VLBI component is ejected by the second black
hole, one expects to be able to detect the offset of the origin of the VLBI
component ejected by the black hole that is not associated with the VLBI core.
The ejection of VLBI components is perturbed by the precession of the accretion
disk and the motion of the black holes around the center of gravity of the
binary black hole system. We modeled the ejection of the component taking into
account the two pertubations and present a method to fit the coordinates of a
VLBI component and to deduce the characteristics of the binary black hole
system. Specifically, this is the ratio Tp/Tb where Tp is the precession period
of the accretion disk and Tb is the orbital period of the binary black hole
system, the mass ratio M1/M2, and the radius of the Binary Black Hole system
Rbin. From the variations of the coordinates as a function of time of the
ejected VLBI component, we estimated the inclination angle io and the bulk
Lorentz factor gamma of the modeled component. We applied the method to
component S1 of 1823+568 and to component C5 of 3C 279.
