The SCR-300 was a portable radio transceiver used by US Signal Corps in World War II. This backpack-mounted unit was the first two way radio to be nicknamed a "walkie talkie".[1]
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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. A series of meetings were held with Signal Corps Engineers at Fort Monmouth, leading to the development of a design which included a single tuning control to tune both the transmitter and the receiver simultaneously and an automatic frequency control to insure clear communication without the need for critical precision tuning on the part of the operator. They also overcame problems of establishing an adequate power supply, a minimum number of crystals, and the fungiciding of the unit to allow it to withstand tropical temperatures and humidity.
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 the war, the first units transported by air for use in the invasion of Italy by the Allied Forces. A sizeable quantity went to the Pacific theatre of war. They made a great contribution in the European invasion where their role in re-establishing order at the conclusion of the Battle of the Bulge have led some to call it the single most useful piece of communications equipment employed in the invasion. Daniel E. Noble, then Motorola's Director of Research, was awarded a Certificate of Merit from the Army for his part in the development of the SCR-300.[2]
The British adopted the design of the SCR-300 for their own use from 1947 as the "Wireless Set No. 31".
Radio Set SCR-300 and SCR-300-A consisted of an 18-vacuum tube, quartz crystal controlled portable FM receiver and transmitter, designated BC-1000 (or BC-1000A), along with batteries and accessories such as the case, handset, and two lengths of whip antenna. It had an innovative tuning that sets both receive and transmit frequency in tandem along with integrated calibration. A squelch circuit was provided to minimize roar in the high-gain circuits when there is no signal. The SCR-300 utilized the frequency band of 40.0 to 48.0 MHz divided into 41 channels of 200 kHz. The transmitter power was 0.3 watts with a range of 3 miles with the longer antenna.[3]
The BC-1000 was used with the same frequency band in the AN/VRC-3 (used in tanks) so the two sets could intercommunicate between armor and infantry. The AN/VRC-3 utilizes the PP-114 Vibrator (electronic) power supply hooked into the vehicle power system.
The entire SCR-300 assembly weighed between 32 and 38 pounds depending on the batteries used (BA-70 or BA-80). The Radio Set SCR-300 was issued with War Department Technical Manual TM 11-242, 15 June 1943 and later dates.[4]