The SCR-299 was a U.S. Signal Corps mobile military communications unit used during World War II.
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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. To meet these demands, a high-powered radio transmitter was required — capable of infallible voice communications over 100 miles (160 km); self-powered; sturdy enough to work in all conditions, flexible enough to cover a wide range of frequencies; and able to operate in motion or at fixed locations.
Production began in early spring 1942. Out of the various sets sent from U.S. vendors, and after considerable experimentation, Hallicrafters Standard HT-4 transmitter was chosen as the desired radio's basis. The HT-4 transmitter's new version became known as the BC-610 transmitter. The receivers finally supplied were the BC-312 and BC-342, plus the BC-614 (speech amplifier), BC-729 (tuning unit) and BC-211 (frequency meter), along with the PE-95 (power unit). All these became part of the truck-and- trailer unit called the SCR-299 — later better known as the "mobile communications unit."
SCR-299 was updated to version SCR-399, similar to the SCR-299 except it was installed in an HO-17 shelter designed to be mountable in vehicles such as 21⁄2-ton trucks and accompanied by the power unit carried in a K-52 trailer. An air transportable version, the SCR-499 was developed and became standard for the USAAF.[1][2] Hallicrafters Company advertising of the period sometimes used illustrations of the shelter-mounted SCR-399 to describe the achievements of the SCR-299.[3]
On November 8, 1942, amphibious landings of British and American forces for Operation TORCH presented the Signal Corps and the SCR-299 with its first major test of the war. Companies of the 829th Signal Service Battalion assigned to each task force attempted to set up the administrative communications net with SCR-299 truck and trailer radio sets immediately upon landing. The plan was to connect the widely separated landing areas and to communicate with Gibraltar. Unfortunately, the weighty sets had been stowed deep in the holds of the convoy ships and only one could be unloaded in time for use during the initial assault. Luckily, British communications ships filled the gap until the SCR-299's could be landed. Once onshore, the sets provided the chief means of long-distance signals until permanent Army Command and Administrative Network stations could be installed.[4] General Dwight Eisenhower credited the SCR-299 in his successful reorganization of the American forces and final defeat of the Nazis at Kasserine Pass.[5]
Though the original Signal Corps requirements were for communication points up to 100 miles (160 km), under favorable conditions these transmitters made and maintained contact over 2,300 miles (3,700 km) of land and sea.[6] During the North African campaign, a Signal Corps battalion took advantage of the SCR-299 and long distance skywave propagation to establish a direct radio telegraph channel to England. On D-Day an SCR-499 housed in a quarter ton trailer designed to be hauled by a jeep arrived in Normandy via glider and immediately went into service to link between two airborne divisions with Britain.[7] The SCR-299 was also used in the invasion of Sicily and the Allied invasion of Italy.[8]
The SCR-299/399 received fairly heavy use by war correspondents and members of the press corps. During the Normandy landings, the US Second Army and US Third Army Group Communications Team provided SCR-399 sets for transmitting press copy to London. When the Normandy Breakout came, Third Army began moving so fast that there was no possibility of putting in a teleprinter circuit from Third Army headquarters back to London and the SCR-399 became the only means of getting press copy direct to London.[9]
In 1944, a short subject film was produced by the Jam Handy Organization and sponsored by the Hallicrafters Company that showed the construction of the SCR-299 and dramatized its use during World War II.[10][11]
The SCR-299 was a complete mobile HF station on frequencies from 2 to 8 MHz (and 1–18 MHz using conversion kits) with transmitter output of 350 watts. The entire unit came in a K-51 truck except Power Unit PE-95 which was in a K-52 trailer. Power could either be supplied by the Power Unit and a 12 volt storage battery, or 115 volt 60 cycle AC commercial power and two spare 6 volt storage batteries. The power requirement was 2000 watts, plus 1500 watts for heater and lights.
The system could be remotely controlled up to a distance of one mile (1.6 km) using two EE-8 field telephones and W-110-B Wire kit. Remote equipment was provided for remotely keying or voice modulating the transmitter, remotely listening to the receiver, and for communicating with the operator of the station.
Frequency Conversion Kit MC-503 gave coverage down to 1 MHz. Frequency Conversion Kit MC-516 gave coverage to 12 MHz and Frequency Conversion Kit MC-517 gave coverage to 18 MHz. The receiver used a 9-foot (2.7 m) whip antenna and the transmitter used a 15-foot (4.6 m) whip antenna while moving. Alternately, it could use a 21 ft (6.4 m) whip antenna while stationary or a 45 ft (14 m) auxiliary wire antenna for 2.0 to 4.5 MHz coverage.[12]