We present a decentralized connectivitymaintenance algorithm for controlling a group of quadrotor UAVs with limited field of view (FOV) and not sharing a common reference frame for collectively expressing measurements and commands. This is in contrast to the vast majority of previous works on this topic which, instead, make the (simplifying) assumptions of omnidirectional sensing and presence of a common shared frame. For achieving this goal, we design a gradient-based connectivity-maintenance controller able to take into account the presence of a limited FOV. We also propose a novel (to our knowledge) decentralized estimator of the relative orientation among neighboring robots, which is a necessary quantity for correctly implementing the connectivity-maintenance action. We validate the framework in realistic simulations that show the effectiveness of our approach.