R&D Report 1984-02 : Intermodulation between VHF/FM broadcast transmitters and the protection of adjacent-band aeronautical services. G.H. Millard Mechanisms are described by which VHF/FM broadcast transmitters can intermodulate and radiate low-level signals which may lie in the adjacent aeronautical services band. Measurements of the levels of intermodulation products at typical stations are given and ways in which these may be reduced in the future are indicated. It is concluded that third-order intermodulation products radiated from the antenna can be kept at least 10dB below the level corresponding to the ITU requirements without undue difficulty.