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Most of us are well aware of GPS’ role in navigation, timing and frequency applications. Because GPS is vulnerable to intentional, unintentional, and natural interference, the US government is placing increased emphasis on technologies that can mitigate overdependence on GPS in these critical applications. Loran is very complementary to GPS and can backup GPS in multiple applications.

While GPS technology is satellite-based and high frequency, Loran uses ground-based transmitters
and is low frequency. Loran signals are very high-powered, so they penetrate cities, buildings and
densely foliaged areas where low level GPS signals are often blocked. From a practical perspective,
Loran is virtually unjammable because of its high power.

This brief article discusses the perspective that Loran should be viewed as
an excellent complement to GPS, and that combining GPS with Loran would
provide a hybrid national system with capabilities much better than either
technology by itself.

Over the last several years, while the nation migrated away from a sole-means GPS approach to critical infrastructure operations, Loran changed in a substantial way, rapidly evolving into a modern system that can provide unprecedented capabilities as a GNSS backup in numerous critical infrastructure operations. Over these same years, the FAA identified Loran as “the best theoretical backup” to GPS, and rigorous studies of a modern Loran system have removed the “theoretical” qualifier. Today, we are entering a new era for a new Loran, now referred to as “enhanced” or e-Loran. In this brief article, I would like to summarize what is going on and what we might expect in this e-Loran era.

In Europe, Asia, and other areas, there is reluctance to depend on GPS as the primary timing reference
source (PRS) for a critical part of a nation’s infrastructure, hence an alternative PRS, such
as Loran, is highly desirable. Essential requirements for that alternative would be the ability to
provide timing performance similar to that of GPS and to distribute coordinated universal time
(UTC).

Advances in Loran receiver technology, coupled with newer NELS and FERNS chains and
planned upgrades to the North American stations, has made Loran as high a quality primary timing
reference as GPS, and it can be superior in many circumstances. For example, Loran can
provide near Cesium clock quality at the receiver site, can generate UTC, and can penetrate urban
environments difficult for GPS reception. When coupled with a rubidium oscillator, GPS
receiver, or both, a Loran receiver can be integrated into a system that would provide high timing
performance with superior reliability.

Timing data from a new generation Loran receiver will be presented along with predictions of
accuracy improvements that will follow implementation of Cesium clock and UTC synchronization
updates to the CONUS Loran stations. Timing accuracy of standalone GPS timing will be
demonstrated. Finally, performance advantages of integrated Ru/Loran and GPS/Ru/Loran timing
systems will be discussed, and implications of encoding UTC in the Eurofix data stream will
be reviewed..