Abstract
This paper deals with the investigation of EM interferences between the FM radio services and a power converter installed on a special purpose vehicle of the fire department. While sporadic interference signals cannot be observed reliably with conventional EMC measurements, real time spectrum measurements are used for the identification of the interference source as well as the coupling path. The investigation finally point out, that a power converter is responsible for the EM interferences radiated by an additional onboard power system. Since the interferences cover a frequency range up to 80 MHz, they are received by the 4 m band antenna and thus disturb the FM radio service due to front door coupling. Furthermore, other radio devices near the command vehicle (e.g. a handheld radio set) will be also disturbed.