  We investigate the pc-scale kinematics and kpc-scale radio morphology of the
quasar PG 1302-102, which may harbour a sub-pc separation supermassive binary
black hole system at its centre as inferred from optical variability.
High-resolution radio interferometric measurements obtained with the Very Long
Baseline Array (VLBA) in the Monitoring Of Jets in Active galactic nuclei with
VLBA Experiments (MOJAVE) programme at 15 GHz at 20 epochs spanning 17 years
were analysed to investigate the pc-scale radio structure. Archival
observations with the Very Large Array (VLA) at 1.4 GHz and 5 GHz were obtained
to study the kpc-scale morphology. We find that the pc-scale jet is inclined
within ~2.2 deg to the line of sight and has a half-opening angle of about 0.2
deg. The parameters derived from the pc-scale radio jet are qualitatively
consistent with those obtained from the analysis of the optical light curve of
PG 1302-102. We obtain at least 0.08 for the mass ratio of the two black holes
in the system. We find some indication for a helical jet structure on
kpc-scale, but the directions of the inner and the extended radio jets are
significantly different, obstructing a straightforward connection of the pc-
and kpc-scale jets within the binary scenario.
