Enhanced or eLoran for time and frequency applications

The US Loran system is undergoing a modernization that will result in an enhanced or eLoran system. As a part of this modernization, three 5071A cesium clocks were installed at each transmitter, and state-of-the-art time and frequency clock measurement and control equipment was installed which uses GPS to steer the ensemble averaged Cs clocks to recover UTC (USNO) within 15 nanoseconds at each transmitter. When the conversion to eLoran is complete, the eLoran system will use time-of-transmission (TOT) control similar to GPS, and add a 9th pulse or Loran data channel (LDC) that will distribute UTC, leap second, and other information from each of the 29 transmitters in North America. eLoran provides performance comparable to GPS for numerous time and frequency applications, so eLoran can act as a traceable, infinite, and independent backup to GPS in these applications. This paper provides an overview of the eLoran modernization program and new eLoran antenna and receiver technology, and data from recent tests, including preliminary studies of Loran performance using H-field antennas located indoors