KODIAK, Alaska --The U.S. Coast Guard warns all mariners that certain marine television antennas may interfere with the performance of Global Positioning System receivers. The interference can result in inaccurate position information or a complete loss of GPS signals.

This is a potential hazard to navigation, for both the operator of the vessel with the television antenna and for nearby boaters as the interference is not limited to the GPS equipment onboard the vessel with the antenna. In some cases, vessels up to 2000 feet away from an active antenna have reported interference.

The Federal Communications Commission identified the following models of antennas as having potential problems during investigations of GPS interference:

• TDP (Tandy Distribution Products) Electronics – MINI STATE Electronic Amplified UHF/VHF TV Antenna – Models 5MS740, 5MS750, 5MS921
• Radio Shack Corporation – Long Range Amplified Omni Directional TV Antenna – Model 15-1624
• Shakespeare Corporation – SeaWatch – Models 2040 (Code date 02A00), 2050 (Code date 03A00)

If mariners experience outages or degradation of their GPS receiver operation, they should perform an on-off test of their marine TV antenna. If turning off the power to the antenna results in improvement in the GPS receiver performance, the antenna may be the source of interference. In that case, the mariner should contact the manufacturer of the antenna and identify the symptoms.

It is stressed that the GPS interference problem may not be limited to the models listed above. If mariners identify another model with a GPS interference problem, or if turning off the antenna does not improve the GPS receiver performance, the Coast Guard requests they contact the 24-hour Navigation Information Service at nisws@navcen.uscg.mil or (703) 313-5900.

GPS is a satellite-based radio navigation system that permits land, sea and airborne users to determine their three-dimensional position, velocity and time, 24 hours a day in all weather, anywhere in the world.

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