What happened
On January 19, 2016, an incident occurred within the Warsaw Flight Information Region (EPWW) involving severe communication disruptions. An air traffic controller at the GAT ACC reported recurring and intense interference on the 125.45 MHz frequency. This frequency is part of a nationwide network of three receivers, one of which is located in Krakow (KRK).
Due to the nature of the interference, the receiver located in Krakow had to be taken out of service periodically because it was introducing significant noise into the system. At approximately 22:20 UTC, the interference caused substantial difficulties in communicating with aircraft crews operating at low altitudes. During this period, the controller was unable to hear the crews clearly and was forced to rely solely on the Krakow radio station for correspondence.
The investigation
The investigation focused on the source of the signal degradation on the 125.45 MHz frequency. Investigators examined the impact of the Krakow receiver on the wider network and noted that the interference was not detectable via the PAŻP (Polish Air Navigation Services Agency) receivers. The matter was subsequently reported to the Office of Electronic Communications (UKE) for further technical assessment.