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.

This report presents the results obtained from a series of tests and related analyses studying the effect of harmful RF interference on LORAN-C receivers. The effects of interference in the 70 to 130 kHz band on typical LORAN-C receivers were assessed. Recommendations were developed for signal-to-interference ratios and protection boundaries that would permit proper receiver operation during conditions of interference. Keywords include: Radionavigation; RF interference; LORAN-C; CCIR; ITU; International Radio Consultive Committee; and International Telecommunication Union.