SCR-300
Encyclopedia
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...
used by US Signal Corps in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. This backpack
Backpack
A backpack is, in its simplest form, a cloth sack carried on one's back and secured with two straps that go over the shoulders, but there can be exceptions...
-mounted unit was the first two way radio to be nicknamed a "walkie talkie".
History
In 1940, MotorolaMotorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
(then the Galvin Manufacturing Company) received a contract from the War Department
United States Department of War
The United States Department of War, also called the War Department , was the United States Cabinet department originally responsible for the operation and maintenance of the United States Army...
to develop a portable, battery powered voice radio receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
/transmitter for field use by infantry
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...
units. The project engineering team consisted of Daniel E. Noble
Daniel E. Noble
Daniel Earl Noble was an American engineer, and Executive Vice Chairman of the Board emeritus of Motorola,who is known for the design and installation of the nation's first statewide two-way radio...
, who conceived of the design using frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
, Henryk Magnuski
Henryk Magnuski
Henryk Władysław Magnuski was a Polish telecommunications engineer who worked for Motorola in Chicago. He was the inventor of one of the first Walkie-Talkies and one of the authors of his company success in the fields of radio communication.-Early years:Magnuski was born on January 30, 1909 in...
who was the principal RF engineer
Radio frequency engineering
Radio frequency engineering is the analysis and design of circuits at frequencies where transmission lines are comparable to the wavelength. It includes the study of amplifiers, oscillators, mixers, demodulators and antennas. This is relevant to RFID, broadcasting, radar, wireless computer...
, Marion Bond, Lloyd Morris, and Bill Vogel. A series of meetings were held with Signal Corps Engineers at Fort Monmouth
Fort Monmouth
Fort Monmouth was an installation of the Department of the Army in Monmouth County, New Jersey. The post is surrounded by the communities of Eatontown, Tinton Falls and Oceanport, New Jersey, and is located about 5 miles from the Atlantic Ocean. The post covers nearly of land, from the Shrewsbury...
, 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
Fort Knox
Fort Knox is a United States Army post in Kentucky south of Louisville and north of Elizabethtown. The base covers parts of Bullitt, Hardin, and Meade counties. It currently holds the Army Human Resources Center of Excellence to include the Army Human Resources Command, United States Army Cadet...
, Kentucky
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
. 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
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...
. A sizeable quantity went to the Pacific theatre of war. They made a great contribution in the European invasion
D-Day
D-Day is a term often used in military parlance to denote the day on which a combat attack or operation is to be initiated. "D-Day" often represents a variable, designating the day upon which some significant event will occur or has occurred; see Military designation of days and hours for similar...
where their role in re-establishing order at the conclusion of the Battle of the Bulge
Battle of the Bulge
The Battle of the Bulge was a major German offensive , launched toward the end of World War II through the densely forested Ardennes mountain region of Wallonia in Belgium, hence its French name , and France and...
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.
The British adopted the design of the SCR-300 for their own use from 1947 as the "Wireless Set No. 31".
Specifications
Radio Set SCR-300 and SCR-300-A consisted of an 18-vacuum tubeVacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
, 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.
The BC-1000 was used with the same frequency band in the AN/VRC-3 (used in tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...
s) so the two sets could intercommunicate between armor and infantry
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...
. The AN/VRC-3 utilizes the PP-114 Vibrator (electronic)
Vibrator (electronic)
In early electronics vibrators were used in inverter circuits to provide an alternating current electric power supply from a direct current source....
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.
See also
- ARC-5ARC-5The AN/ARC-5 Command Radio Set is a series of radio receivers, transmitters, and accessories used to provide two-way Morse code and AM radiotelephone communication for U.S. Navy aircraft during World War II and the years following. It was an improvement of the Navy's ARA/ATA command set. Similar...
- AN/PRC-6AN/PRC-6The AN/PRC-6 is a walkie-talkie used by the U.S. military in the late Korean War era through the Vietnam War. Raytheon developed the RT-196/PRC-6 following World War II as a replacement for the SCR-536 "handy-talkie". The AN/PRC-6 operates using wide-band FM on a single crystal controlled frequency...
- BC-348BC-348The BC-348 is a compact American-made communications receiver, which was mass-produced during World War II for the U.S. Army Air Force. Under the Joint Army-Navy nomenclature system, the receiver system became known as the AN/ARR-11. -History:...
- BC-654BC-654The SCR-284 was a World War II era combination transmitter and receiver used in vehicles or fixed ground stations.- History :The Crosley Corporation of Cincinnati, Ohio manufactured the Signal Corps Radio set SCR-284 that consisted of the BC-654 and associated support equipment.The BC-654 first saw...
- R-390AR-390AThe R-390A /URR is a general coverage HF radio communications receiver designed by Collins Radio Company for the US military.-History:The R-390A military shortwave radio receiver was the result of a project undertaken by the U. S. Army Signal Corps in 1954 to replace the existing R-390 receiver...
- SCR-299SCR-299The SCR-299 was a U.S. Signal Corps mobile military communications unit used during World War II.-History:The SCR-299 replaced SCR-197 and SCR-597, and was an effort to give a long-range communication advantage to the U.S. Army and its allies...
- Signal Corps RadioSignal Corps RadioSignal Corps Radios were U.S. Army military communications components that comprised "sets". Under the Army Nomenclature System, SCR initially designated "Set, Complete Radio," and later "Signal Corps Radio," though interpretations have varied over time....
- Wireless Set No. 19Wireless Set No. 19The Wireless Set No. 19 was a Second World War mobile radio transceiver designed for the British Army to give armoured troops reliable communications.- Specifications :...
- Vintage amateur radioVintage amateur radioVintage amateur radio is a subset of the amateur radio hobby, considered a form of nostalgia much like antique car collecting, where enthusiasts collect, restore, preserve, build, and operate amateur radio equipment from bygone years, most notably those using vacuum tube technology.Popular modes of...
- AN/PRC-77 Portable TransceiverAN/PRC-77 Portable TransceiverAN/PRC 77 Radio Set is a manpack, portable VHF FM combat-net radio transceiver manufactured by "Associated Industries" and used to provide short-range, two-way radiotelephone voice communication...
- SCR-694SCR-694The SCR-694 was a portable two way radio set used by the U.S. military during World War II. -History:The SCR-694 replaced the SCR-284 and was later replaced by the AN/GRC-9...