Abstract: A welding tool for joining at least two workpieces by friction stir welding includes a pin for applying frictional heat to the workpieces. The pin includes a first pin region formed from a first material and a second pin region formed from a second material.

Abstract: A reactive radio interferer includes a plurality of time synchronized transmitting/receiving lines, each of which is designed to alternately carry out-monitoring phases in order to receive the radio spectrum and interference phases in order to transmit an interference signal on the basis of the radio spectrum received in the monitoring phase. Testing of the reactive radio interferer is performed by having one of the transmitting/receiving lines transmit a test signal within a monitoring phase, the test signal being received and evaluated by at least one other transmitting/receiving line.