Retired Navy Capt. James Alonzo Madigan Sr., 51, a communications officer and an authority on radio frequency management for Navy fleet operations, died Thursday at Fairfax hospital after a heart attack.

In 1962, Capt. Madigan became head of the radio wave propagation and frequency management publications branch in the office of the chief of Naval Operations.

As such, he was responsible for centralized control of the procurement, assignment and protection of radio frequencies for Navy fleet operations, including radar assignment, and navigation aids. He also was responsible for the acquisition of frequency assignments for Navy satellite systems.

Capt. Madigan was born in Dahlgren, Va. He enlisted in the Navy after graduating from high school and received a fleet apontment to the U.S. Naval Academy at Annapolis, from which he graduated in 1952.

He then earned degrees in communications and electrical engineering from the Naval Post Graduate School in Monterey, Calif.

Capt. Madigan subsequently served as communications officer aboard the Navy's first nuclear-powered surface vessel, the USS Long Beach.

He also served three tours of duty in Vietnam, that last as commanding officer of the Naval Communications Stations at Cam Rahn Bay.

He was commanding officer at the Naval Communications unit in London for four years before returning to this area in 1974.

His last assignment was as director of the Naval Electromagnetic Specutrum Center. He retired in February.

Capt. Madigan then became a senior systems engineer for Science Applications Inc. in Arlington.

He lived in Vienna, Va., and was a member of St. Mark's Catholic Church there.

Survivors include his wife, Jerry, two daughters, Peggy and Kem, all of Vienna; a son James A. Jr., of Philadelphia, and two brothers, Thomas, of Alexandria, and Frank, of Henderson, N.C.

The family suggests that expressions of sympathy be in the form of contributions to the Northern Virginia Chapter of the American Heart Association.