SCR-582

 Search Radar Set - A World War II fixed seacoast artillery microwave radar set designed and built by Radiation Laboratory in Cambridge, Massachusetts. Initially designated the SCR-582 but replaced after production of 55 sets under that designation with the SCR-682A. The SCR-682A was the mobile version but was deployed in fixed locations as well as mobile sites.

SCR-582 Search Radar
Designed to be used as a overall surveillance radar for harbor control and defense by detection of surface craft and low-flying planes. One of the first production radars to incorporate a rotating antenna beam driving a plan position indicator (PPI) to display radar tracks for 360 degrees on a cathode ray tube. The PPI provided a real time display of all radar tracks within the range of the radar.





In addition to the main PPI display, the SCR-582 had a "B" Scope that could display an expanded segment of the main display 4000 yards by 40 degrees to focus in on specific targets. The set was capable of remoting up to four "B" scope displays up to 1,000 yards away from the radar set. The SCR-582 also had a VG remote indicator that could project an image of the main PPI display on a 30" ground glass screen overlaid with an outline map of the coverage area.

In stateside installations, the SCR-582 and the later mobile version SCR-682A were deployed in support of the Harbor Entrance Control Post (HECP) at each of the Harbor Defenses to identify and track approaching surface ships and aircraft. In some cases, the SCR-582/682A radar was installed on top of the HECP itself as shown in the cross-sectional view of the Fort Burnside HECP. The HECPs were sometimes disguised as seaside homes or lighthouses. The photograph of the Fort Dawes HECP shows the HECP in operation.

The role of the SCR-582 in the HECP was both management of harbor traffic and to identify any hostile vessels/aircraft approaching the harbor. The SCR-582 was not accurate enough to control the fire of the harbor gun batteries but it was accurate enough to assign targets to specific batteries. Each of the large caliber gun batteries (6-inch and greater) defending the harbor was to be equipped with a SCR-296A radar capable of tracking and controlling the fire against a single target. Having no general search capability and little ability to discriminate between targets, the SCR-296A transmitter was not to be even turned on until a target had been spotted and assigned or a limited search area had been defined.

All of the early radar equipment supplemented the existing system of shoreline based optical spotting and base end stations. The SCR-582 could provide large surface target detection at a maximum range of 90,000 yards (44 nmi) even in dense fog. This was far beyond the range of either the shore batteries or enemy ships and it followed that the enemy could be identified and engaged at this distance with aircraft or ships.

A major limitation of the SCR-582 was that it had no antenna tilt adjustment and could not detect aircraft at higher altitudes because of this. The set also suffered from a spare parts problem.

SCR-682A
Some of the limitations of the SCR-582 were addressed very quickly with the introduction of the mobile version SCR-682A. Designed as a mobile radar set carried in three 2 1/2 ton, 6 X 6, LWB cargo trucks or two 2 1/2 ton, 6 X 6, LWB cargo trucks, and two 1 ton trailers. Erection time was 3 to 5 hours by a trained crew of five. The initial application was envisioned as mobile fire control for 155mm seacoast battalions and 8-inch railway battalions but it was quickly adapted for fixed locations and placed in HECPs.

The mobile version included a mechanical adjustment for the antenna tilt angle to allow for detection of aircraft at greater altitudes at the expense of surface craft detection. A 5X upgrade of transmitter power extended the range and increased target detection capability. The result was a maximum range of 240,000 yards (118 nmi) and an effective range against surface targets of 35,000 yards (17 nmi). The range accuracy also improved as did the PPI display with more useful display ranges.

Identification Friend or Foe (IFF)
Allied aircraft and ships were equipped with predominantly British MK III IFF transponders and the SCR-582 was integrated with the RC-182 IFF Interrogator. When an RC-182 interrogated the aircraft/ship transponder the transponder replied with a synchronized pulse that altered the PPI display on the SCR-582 indicating which tracks on the display were friendly. The SCR-682 used the RC-282 IFF set.

See Also:
 * US Radar Sets

Sources:
 * , page 411-414.
 * FM 4-96 Seacoast Artillery: Service of Radio Set SCR-582
 * FM 4-97 Service of the Radio Set SCR-682-A

Links:
 * Radomes - Radar Equipment
 * Kodiak Military History Museum - SCR-582
 * Ibiblio - SCR-582
 * Mobile Radar - SCR-682A