A miniature and light-weight logger for tracking migrating bats over several months has been developed over the last years. In this publication details about the advanced circuit design and elaborate assembly methods are presented. A RF network is optimized simulatively and experimentally that combines matching, filtering and balancing the transceivers ports to an 3/4 antenna. Subsequently, the densely populated board is assembled in our laboratories. A fixture for fast programming and testing simplifies series production of 150 loggers. Finally, the PCBs are glued to a battery and molded in durable fiber-reinforced epoxy. In summary a sensor node with the size of a 1 Eurocent coin and 2 g is produced.
