Adaptive antenna for scanning telemetry

The UHF2 band (450-470 MHz) is currently assigned to private mobile radio (PMR). Frequency re-use is obtained by dividing the country into cells (for telemetry and PMR trunking use). This can give rise to inter-cell interference when propagation distances are increased either by geographical features (e.g. valleys) or atmospheric effects (lift conditions). Adjustment of cell sizes and shapes are controlled by the Radio Communications Authority (RA) so interference can be avoided except under extreme conditions. Much more difficult to avoid is interference from transmitters based in Continental Europe which are outside of the RA´s authority. During lift conditions interference from the Continent can be loud enough to cause corruption of the data links. In order to remedy the situation it has been proposed that one could be to alter the reception pattern of the base station, such that it would be desensitised against the interfering signal while maintaining coverage for the outstations. This adaptive antenna approach is exploited by the BNR Interference Reduction Device (IRD). The performance and architecture of the IRD is discussed