A. Atwater Kent, Jr., a yachtsman and son of the radio pioneer, died Saturday at St. Mary's Hospital in West Palm Beach, Fla. He was 79. Born on Pine Street in Philadelphia, Kent left high school to work at the Atwater Kent Manufacturing Co. on Wissahickon Avenue, which his father, A. Atwater Kent Sr., had founded. In 1929, he became a vice president in the company, which was known for its high-quality radios. By 1937, however, his father had closed the company rather than allow a unionto organize its workers. Young Kent then opened a manufacturing company, Kent Aircraft and Gauge Co. Kent, who had lived iin Ardmore, was a licensed pilot, but his true love was yachting, son Peter Alexander Kent said yesterday. The Kent family began vacationing in Palm Beach, Fla. about 1917, first at the well-known Breakers Hotel. From there, Kent began exploring the yachting world. The family also spent its summers in Northeast Harbor, Maine. In Philadelphia, Kent strongly supported museums. For example, he donated the flagpoles in front of the Philadelphia Museum of Art many years ago, said daughter Suzanne Kent Hitchcock. He was president of the American Flag House and Betsy Ross Memorial at its inception in 1936. He also was president of the Atwater Kent Museum, which is the Philadelphia history museum named after his father. He was on the board of directors of the Pennsylvania Historical and Museum Commission, as well as the Independence Hall Association from its founding in 1942. He also was the director of the Atwater Kent Foundation. After he retired to Palm Beach, he became president of the Society of the Four Acts, a vestryman in the Church of Bethesda-by-the-Sea and a director of the Bath and Tennis Club. Interested in maritime history, Kent was also a commodore of the Corinthian Yacht Club of Philadelphia and a member of the New York Yacht Club and the Northeast Harbor Fleet in Maine. In addition, he belonged to the Philadelphia Club and the Pennsylvania Society of the Sons of the American Revolution. He was a lifetime member of the Metropolitan Museum of Art, the Philadelphia Museum of Art and the Pennsylvania Academy of the Fine Arts. Survivors: his wife, Hope Parkhurst Kent; six children, Suzanne Kent Hitchcock, A. Atwater 3d, Christopher Brinton, Peter Alexander, Eliot Hewlett and Allison Angelsea de los Reyes; two grandchildren; a sister and a brother.