SCR-268

 Medium Range Searchlight Control Radar Set - A World War II era medium range searchlight control radar set built by Western Electric. Primary use is to provide range, azimuth and height information for approaching enemy aircraft to a variety of gun-laying computers (M-4, M-7, or M-9 directors) and searchlight positioning equipment.

Western Electric began production of SCR-268 sets in 1939, and it entered service in early 1941 some 3,100 sets were eventually built. The SCR-268 was a mobile radar set transported on two trailers or for the SCR-268-B on one trailer and four large trucks. In operation, the set was assembled on one trailer and leveled with outrigger jacks. The antenna pedestal was mounted on the trailer and on that pedestal rotated the antenna, transmitter, receivers and the three operator positions. Of the four attending trucks, one supplied primary power, another supplied the high voltage for the transmitter, and the third carried the antenna components while the fourth transported the remaining radar components and spares. On the ground beside the trailer were placed the keyer and modulator units which drove the transmitter. The high voltage output of the modulator was fed to the transmitter via a set of slip rings inside the rotating pedestal.

The transmitter and receiver equipment was stacked over the three operator positions which were directly over the rotating pedestal. Antenna movement was controlled by three handwheels. The three operator positions, range, azimuth and elevation operators each have a cathode ray tube (CRT) display that indicates when the radar is pointed at the target and when the range, azimuth and height readings could be sent to the gun director and searchlights. Lobe switching was used to provide increased accuracy for the operators.

To provide for identification of friendly aircraft vs enemy aircraft the Identification Friend or Foe (IFF) RC-148 IFF set was provided and its video mixed with the receiver video to indicate when a radar track was friendly.

Thirteen men could install set and obtain approximate data in 2 hrs. Accurate orientation and alignment take 4 more hours. Orientation and alignment were complex and had to be checked daily. A minimum of 5 operators and a Chief Radar Operator were required.

SCR-516
A plan position indicator (PPI) was added to the SCR-269 set and it was then redesignated an SCR-516, low-altitude early-warning radar. The SCR-516 was deployed in 1945 in at least three locations in the Pacific Northwest to combat the Japanese balloon firebomb attack. Additional sets were deployed in California.

SCR-268 Radar


See Also:
 * US Radar Sets

Sources:
 * Radar Tutorial - The SCR-268 Radar (Electronics - September 1945, page 100-109)
 * U.S. Navy - U.S. Radar Operational Characteristics of Radar Classified by Tactical Application FTP 217, page 46

Links:
 * Radomes - Radar Equipment
 * Pacific Eagles - SCR-268 Radar
 * Radio Nerds - SCR-268
 * Wikipedia - Signal Corps Laboratories