LORAN Data Channel (LDC)

This is part of the on-going effort between the Federal Aviation Administration and the U.S. Coast Guard to modernize the LORAN-C system. The LORAN Data Channel (LDC) will provide information using pulse position modulation of the broadcast signal. The proposed pulse position modulation would be used to broadcast up to sixteen message types including but not limited to station identification, absolute time, early skywave warnings, and differential LORAN correction messages. The proposed method will use an additional pulse added one thousand microseconds after the eighth pulse on a secondary transmitting station and between the current eighth and ninth pulses on Master.

The FAA and Coast Guard began conducting LDC on-air tests in July of 2005. The test broadcast will use pulse position modulation of a ninth pulse added one thousand microseconds after the standard pulse group as described above. Throughout the test period the signal will meet all service performance parameters published in the 1994 Specification of the LORAN-C Signal. Users should not experience any tracking errors or service interference from this test broadcast. Users will be notified through Notice to Mariners and Notice to Airmen of any changes to the test schedule and when the testing is completed.


The LDC Description document contains a description of the current signal modulation format. Please note that the format is for research only and will be subject to change. We will continue to update the site as these changes occur.

The following stations will continuously broadcast with LORAN Data Channel Modulation on the rates indicated:

• Jupiter, FL 7980-Y
• Las Cruces , NM 9610-X
• Middletown, CA 9940-X

The following stations will broadcast, between 8:00 AM and 3:00 PM (local times), Mondays thru Fridays, with LORAN Data Channel Modulation on the rates indicated:

• Seneca, NY 8970-X
• Gillette, WY 8290-X
• Grangeville, LA 7980-Y
• Dana, IN 9960-Z
• George, WA 9940-W

Each LORAN station will initially transmit the basic Station Identification/Time message only with exception of LORAN Station Seneca. LORAN Station Seneca will also broadcast differential LORAN corrections for additional research. Each transmitted message will include a “test mode” bit to warn users that the information in the message is for research ONLY. As testing continues, there is a high probability of incorporating additional messages. Each new message will have an indicator that it is for testing purposes only.

Users are encouraged to report any LORAN service degradation or outages that they may experience via the Navigation Information Service (NIS) by calling (703) 313-5900 or by using the NAVCEN web site's Report a LORAN Problem Worksheet. Users should visit this site as well as review their Local Notice to Mariners (LNM) or Notice to Airmen (NOTAM) to obtain the latest information.