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Signal Corps Radio set SCR-300-A
SCR-300 battery-powered FM voice receiver/transmitter, Motorola, 1940

The SCR-300 was a portable radio transceiver used by US Signal Corps in World War II. This backpack-mounted unit was the first radio to be nicknamed a "walkie talkie".[1]


In 1940, Motorola (then the Galvin Manufacturing Company) received a contract from the War Department to develop a portable, battery powered voice radio receiver/transmitter for field use by infantry units. The project engineering team consisted of Daniel E. Noble, who conceived of the design using frequency modulation, Henryk Magnuski who was the principal RF engineer, Marion Bond, Lloyd Morris, and Bill Vogel. The SCR-300 operated in the 40.0 to 48.0 MHz frequency range, and was channelized. It, along with mobile FM tank and artillery radios such as the SCR-508 (20.0 to 27.9 MHz) and the SCR-608 (27.0 to 38.9 MHz) marked the beginning of the transition from low-HF AM/CW to low-VHF FM for combat-net radio.

The final acceptance tests took place at Fort Knox, Kentucky. The performance of the SCR-300 during those tests demonstrated its capacity to communicate through interference and the rugged quality of the design. Motorola was to produce nearly 50,000 of the SCR-300 units during the course of World War II.[2][3]

The SCR-300 saw heavy use in the Normandy invasion and the Italian campaign. It also became "key equipment" that helped deter confusion in the Battle of the Bulge.[4]

The British adopted the design of the SCR-300 for their own use from 1947 as the "Wireless Set No. 31".[5][6]

War Department Technical Manuals[edit]

  • TM 11-242 for Radio Set SCR-300-A (1945)
  • TM 11-983 for PP-114 Vibrator power supply (1945)
  • TM 11-637 for AN/VRC-3 (1944)

See also[edit]


  1. ^ Magnuski, H. S. "About the SCR-300". Retrieved 2 July 2016. 
  2. ^ Harry Mark Petrakis (1 January 1991). The founder's touch: the life of Paul Galvin of Motorola. Motorola University Press, J.G Ferguson Pub. Co. ISBN 978-0-89434-119-9. 
  3. ^ Christopher H. Sterling (2008). Military Communications: From Ancient Times to the 21st Century. ABC-CLIO. pp. 504–. ISBN 978-1-85109-732-6. 
  4. ^ Bill Yenne, William Yenne. Secret Gear, Gadgets, and Gizmos. Zenith Imprint. pp. 32–. ISBN 978-1-61060-744-5. 
  5. ^ United States. War Dept (1945). Radio Set SCR-300-A, War Department Technical Manual TM 11-242. United States War Dept. Archived from the original on 2005. 
  6. ^ "SCR-300 Backpack Radio". Retrieved 2 July 2016.