Analysis of interference between railway and airport

One of the alternatives for the planned Norrbothnia railway (Norrbotniabanan) is by the military airport F21 outside Luleå. The airport has a number of critical systems for flight safety, such as the ILS (Instrument Landing System), radio systems for communication between aircraft and the air traffic control, navigation systems and military radio systems. The object has been to assess the risk that emissions from the railway system may interfere with the various radio and navigation systems. The results show potential impact when a train passes the airport. The assessments are based on two different approaches. For different scenarios, the systems' margin to the permitted interference level have been calculated. The scenarios that have been analysed are: flying enroute with receivers in aircraft and on the ground, landing with receivers in aircraft and on the ground and, finally, when both transmitter and receiver are on the ground. Given the assumptions, the analyses indicate an interference risk in some systems caused by emissions from the railway system. Specifically, the VHF and UHF communications are at risk of not having a high enough margin or no margin at all. The report does not evaluate any measures. In order to reduce the risks, appropriate measures need to be investigate and implemented, for example by changing the positions of transmitter and receiver stations, changing transmitter power or the introduction of better antennas.