  Blazars are powerful, variable emitters from radio to gamma-ray wavelengths.
Even though the general picture of synchrotron emission at low energies and
inverse Compton at the high energy end is well established, many important
aspects of these remarkable objects are still not well understood. For example,
even the location of the gamma-ray emission region is still not clearly
established, with some theories locating it close to the black hole/accretion
disk while others place it at parsec scales in the radio jet. Since mid-2007 we
have carried out a large scale monitoring program at 15 GHz using the OVRO 40 m
telescope. We are currently observing about 1700 blazars twice per week. The
sample includes all the Fermi-LAT detected blazars north of declination -20
degrees. Here, we study the existence of correlated variability between these
two bands for 86 sources bright enough to be detected weekly by LAT. The
existence of correlated variability can be interpreted as an indication of a
related spatial locations for the radio and gamma-ray emission, making the
evaluation of its statistical significance a key goal of our program. A study
of the statistical significance of these cross-correlations is presented along
with a discussion of the Monte Carlo simulations used to evaluate them. More
information about the conditions on the radio emission zone can be obtained
through polarization monitoring which tells us about the configuration of the
magnetic fields in this region. To study radio polarization variability we are
building KuPol, a radio polarization receiver for the 12 to 18 GHz band that
will replace the current total power receiver at the OVRO 40 meter telescope.
