Frank Malcolm Gager, a retired scientist at the Navl Research Laboratory, died Tuesday at Washington Adventist Hospital after a long illness. He was 72.

A native of Scranton, Pa., Mr. Gager received a bachelor's degree in electrical engineering from Pennsylvania State College in 1928, and a master's degree from Massachusetts Institute of Technology in 1930. He was an instructor in the department of electronic engineering at MIT from 1928 to 1933.

From 1933 to 1943, hw was a professor of electronic physics at Boston College. He then became a staff member of the radio research laboratory at Harvard, where he worked on radar-jamming technology.

In 1945, Mr. Gager joined the Naval Research Laboratory, and from 1946 to his retirement in 1973, he headed the radar techniques branch there. He was considered an authority on over-the-horizon radar, which unlike conventional types of radar is not restricted to line-of-sight ranges. Mr. Gager received the Navy Distinguished Civilian Service Award in 1970.

An enthusiastic amateur radio operator, Mr. Gager had worked as a shipboard radio operator in 1924 and 1925. He was a life member of the Institute of Electrical and Electronic Engineers, and belonged to the American Physical Society, the American Association for the Advancement of Science, and the honorary engineering societies Tau Beta Pi and Eta Kappa Nu.

Survivors include his wife, Myrtle, of the home in Hyattsville; a son, William, of Fairfax; a daughter, Jane Reed, of Tampa; a sister, Frances Terhune, of Viewtwon, Va., and five grandchildren.