An apparatus for detecting high frequency interference radiation signals, such as radio frequency emissions, on board a passenger aircraft includes at least two receiver units for receiving and measuring the interference radiation signal, and a monitoring unit for evaluating the signal measurement results. Each receiver unit respectively includes at least one antenna, the monitoring unit includes an interference computer, and a digital data signal transmission path connects the receiver units to the monitoring unit. The interference computer evaluates the data signals received from the receiver units to determine the location of an interference radiation source within the aircraft, and indicates corresponding location and warning information on a display unit connected to the interference computer.