An antenna combination includes a feed-through having an input side including a connector for coupling to a transmission line connector and an output side including an inner cavity attaching to an aperture in a top surface or a nozzle of a tank. A foam filled dielectric rod antenna is coupled to the output side of the feed-through having a nose portion including a sub-portion within the inner cavity and a rod-shaped portion from beyond the inner cavity to an antenna launch end. The rod-shaped portion includes an outer solid dielectric material including a thickness transition region, wherein a thickness of the solid dielectric material decreases toward the antenna launch end to a constant minimum thickness shell region that extends to the antenna launch end. The outer solid dielectric material defines an inner hollow region. A dielectric foam fill material fills the inner hollow region.