Radio detection of ultra high-energy cosmic ray air showers

The LOPES experiment (LOFAR Prototype Station) has been built at the KASCADE-Grande experiment in order to test the LOFAR (LOw Frequency ARray) technology and demonstrate its capability for radio measurements in extensive air showers (EAS). We could for the first time demonstrate by this detector and the coincidence to KASCADE the origin of the radio signal from a geo-synchrotron effect and the coherent nature of the measured signals. After these results we developed the next generation of antennas easy to calibrate, with precise detection of polarization, low power electronics, and trigger with capability of self-triggering. Furthermore the background situation was measured and analyzed at the site of the southern and northern Auger observatory and KASCADE