Francis Cooper South, 71, a retired technician with the John Hokpins Applied Physics Laboratory, died of cerebral arteriosclerosis Monday at the Fairland Nursing Home in Silver Spring.

He retired about 1971 after 30 years with the laboratory. In World War II, his work had been concentrated on the audio proximity fuse, which was first used by the Navy against Japanese planes in 1943.

Born in Princeton, N.J., Mr. South [WORD ILLEGIBLE] and operated one of first crystal radios in that area. He was a hem radio operator for many years.

He came to Washington about 1940, and worked briefly with the Carnegie Institute of Terrestial Magnetism before joining the Johns Hopkins Laboratory.

Mr. South was past president of the Rock Creek Amateur Radio Association a member of the Quarter Century Wireless Association and a trustee, of the Foundation for Amateur Radio.

He is survived by his wife, Dorothy, of the home in Wheaton; a son, Frank C. Jr, of College Park; a daughter, Mary Ann Li, of White Oak; two sisters, Mrs. Warren S. Stone, of Bathesda, and Mrs. James M. Tunnell Jr., of Wilmington, Del., and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.