PORTSMOUTH, Va. — Boaters will be unable to rely on Global Positioning System equipment and possibly cell phones because of scheduled disruptions from Friday to Sunday that will affect mariners transiting the waters of North Carolina and parts of Florida.

GPS interference testing conducted during an exercise by the Department of Defense will make the GPS signal unreliable and may affect cell phone signals from about 50 to 60 miles off the coast of Cape Hatteras, N.C., and approximately 80 miles out between Jacksonville and Melbourne, Fla.

Disruptions along the North Carolina Coast will affect Albemarle Sound, Pamlico Sound and the Coastal North Carolina area from Currituck Beach Light to Cape Lookout and the IntraCoastal Waterways of North Carolina.

"The Coast Guard fully supports the efforts of the Department of Defense during this important exercise," said Rear Admiral Sally Brice-O'Hara, commander of the Fifth Coast Guard District. "But, we must get the word out to impacted mariners so they can take the necessary precautions to keep themselves safe during this busy boating season."

Mariners should not rely on GPS nor cell phones from June 11 to 20. Plan ahead and use VHF radios to communicate on the water. A cell phone is a good backup communications device, but out on the open water, it is no substitute for a VHF radio.