Reception of Decca Navigator multipulse and zone identification transmissions by single-channel receivers

Receivers for the Decca Navigator system have recently been developed in which a single, frequency-agile receiving channel, operating under microprocessor control, replaces the five single-frequency channels of a conventional receiver. The paper describes techniques which allow such receivers to utilise the multipulse lane-identification and the zone-identification transmissions of the Decca chain which were designed for receivers with multiple channels. An algorithm is described by means of which the microprocessor calculates zones and zone fractions from samples of the phases of the transmissions received. Operational results, measured under conditions of night-time skywave propagation, are presented which demonstrate that the technique works successfully and that it has certain advantages over conventional methods of multipulse and zone-identification reception.