The design, construction and testing of Loran-C from a drifting buoy

Abstract

A low-windage, current-following spar buoy system containing an automatic Loran-C navigation receiver and a single sideband transmitter with associated control circuitry is described. The Loran-C unit acquires and tracks Loran-C signals and, at intervals controlled by an onboard timer, produces a digital message which modulates the transmitter. The transmitter sends this message via a radio telemetry link to a base or ship receiving station where it is decoded. The decoder displays the message contents in the form of Loran-C time differences representing two lines of position, and thus a geographic fix. The system enables the position of the buoy to be tracked as it drifts with the current and thus serves as an instrument in measuring surface and near-surface current transport. A physical description, details of electrical and mechanical design, and test results, are documented in this report. Feasibility of the system was proven, and a pre-prototype system built and tested.