Interference cancellation for a UHF telemetry system

UHF telemetry systems, used by the public utility companies to monitor outlying installations, are subject to interference from continental Europe during periods of anomalous propagation (ducting). The situation is particularly serious in the south-east corner of the UK where at certain times between April and October, network outage can exceed 60%. This paper describes an equipment which has been designed to restore near-normal operation to such systems in the presence of interference. The equipment is effectively a 2-element adaptive array, using analogue interference cancellation techniques. The self-contained unit requires an additional directional antenna to provide a sample of the interference, but is otherwise easy to install and maintain. It offers a low cost solution in the interim period before frequency re-allocation is implemented in the next century