Probably the most significant research between the wars pertained to radar, an offshoot of radio. Radar is an acronym for radio detection and ranging and was not actually coined until 1940 by the USN. The origin of Army radar research dated back to WWI when Major William R. Blair conducted experiments in sound ranging for the purposes of locating approaching aircraft by the use of their engines. In the 1930s Blair became director of the Signal Corps labs at Fort Monmouth and began investigating the pulse-echo method of detection in the Signal Corps labs.
In December 1936, Signal Corps engineers conducted the first field test of the radar equipment at the Newark, New Jersey, airport where it detected an airplane seven miles away.
By May 1937, Signal Corps demonstrated its still crude radar, the SCR-268, a short-range radar set, for Secretary of War Harry H. Woodring; BG Hap Arnold, Assistant Chief of the Army Air Corps; and others. The Secretary and BG Arnold were impressed and the latter urged development of a long-range version for use as an early warning device. With high-level support, the Signal Corps received money needed to continue its developmental program …

CONTENT By CHAPTER:
    Introduction - EARLY HISTORY OF RADAR
1. INTRODUCTION TO RADAR
2.  CHARACTERISTICS OF RF RADIATION 
3.  RADAR SIGNAL CHARACTERISTICS
4.  RADAR SYSTEM COMPONENTS
5.  RADAR PRINCIPLES
6.  Film - SCIENCE IN ACTION: RADAR (1956; B&W): This TV Show features discussions, demonstrations and an interview with U.S. Air Force Brigadier General James W. Andrew about the uses and technology of radar as an air defense tool.
7.   Film - ON GUARD! THE STORY OF SAGE (1956; COLOR): This movie explains innovations in computer technology as weapons in the Cold War, including radar