Beaming and precession in the inner jet of 3C273

We have used all the available VLBI data to determine the kinematical evolution of the inner jet of 3C273. The position angles, velocities and formation epochs of different superluminal components are compatible with a precessing inner jet. The time dependence of the Doppler factor-for this jet is computed and the implications for the gamma-ray emission are discussed. Additionally, the model, when considered along with simultaneous radio and X-ray variability observations provides an upper bound to the Hubble constant (H-0 less than or similar to 80 km/s/Mpc).