Loop loaded wire antenna

In automatic meter reading (AMR) systems, one embodiment of the prior art comprises: the PCB, the battery and the antenna are held together in a short plastic tube and encapsulated. The antenna and the unit is then put into a metal walled, metal or plastic covered pit, where the antenna part is at the level of the ground plane and slightly lift above the plastic or metal cover through a hole in the lid. The highest level of the unit (antenna) is slightly above the ground level. Antenna radiation is strongly limited by the metal wall and especially the metal cover. In this situation, the antennapsilas size is strictly confined but high radiation efficiency and high gain of the antenna are required.