Loran-C is a navigation and timing system with a long and interesting history. In its near half-century existence, it has proven its worth against newer and more technologically advanced navigation system designs. From the work done to improve Loran's capabilities, we look at alternative means of providing navigation solutions to future users while maintaining the current infrastructure. Specifically, we investigate the design implications for a new potential overlay system and possible replacement to Loran-C currently under development at Oak Ridge National Laboratory. The implications for existing users, in terms of performance and reliability, are explored. Through laboratory experiments and computer simulations, we show that interoperability can exist with this new design and legacy Loran receivers with little or no modifications. We also give an overview of previous methods used in interference analysis and their applicability here for wideband PSK signals. Lastly, we suggest some additional work necessary to obtain better quantitative results specific to certain receivers.

The performance of three Loran-C airborne receiver/computer systems was investigated during flights in the U.S. Northeast Corridor to determine the feasibility of using Loran-C signals and equipment to navigate V/STOL vehicles in that area. Flight tests were conducted in a C-130 and DC-6 fixed wing aircraft, and a CH-47C helicopter. Tracking radar was used on several of the flights to determine the airborne Loran-C equipment accuracy. Oscilloscope photographs of the received signals and strip chart recordings of the received 50 kHz to 150 kHz spectrum were used to establish the Loran-C signal, noise, and interference conditions throughout the Northeast Corridor. Test results showed that existing Loran-C signals and the systems did establish aircraft positions from the ground to operating altitudes in the Northeast Corridor. However, the equipment interfering signal rejection ability and reliability were not adequate for immediate operational use. (Author).