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The history of US naval radars is somewhat confusing because of the variety of types of designations employed. These reflect the organizations behind development. During World War II, the US Navy deployed two major radar series: search sets (BuShips) and fire control systems (BuOrd). The former carried over a system consisting of a type letter, eg S (search radar), and a model letter: thus SC is the third US search radar; and SC-S is the fifth modification of SC. The Bureau of Ordnance preferred to use mark numbers, eg Mk 25; modifications within a mark were also numbered, eg Mk 25 Mod 1. However, the earliest fire control radars were also designated under the BuShips system, with the type letter F; thus FH is Mark 8. Such designations were dropped early in the war, but persist on plans drawn as late as 1945. Three letters were generally used to extend series beyond twenty-five (the letter I was not used); thus RAA, RAB and RAG would be the twenty-sixth, -seventh, and -eighth radio receivers. There were only twenty-four search radars, so none required three letters. Lower-case letters (eg 'a' in SRa) indicated field changes. The prefixes 'X' and 'CX' were reserved for the Navy (NRL) and commercially produced experimental or preproduction sets, eg CXAM, the first US naval radar. These series included all types of electronic equipment. The Army used an entirely different class of designations, its radars being numbered in the Signal Corps Radio (SCR) series. One Army radar, SCR-720, was fitted in limited numbers to US warships at the end of the war. The fragmented system thus described did not long outlast World War II. Even during the war it proved difficult for Navy and Army (Air Force) to coordinate airborne radar procurement. Early Navy air radars were designated in the same manner (but not the same series!) as the surface sets, so that ASH was the eighth airborne search radar. However, in February 1943 a new universal system appeared, three letters plus a number (platform-type of equipment, and function). For example, APS-4 was the fourth airborne pulsed (radar) search device. New equipment designed after World War II, even when it was specific to the Navy, fitted this pattern with the prefixes 'S' for surface ships and 'B' for submarine. Generally the multiservice designations are prefixed by the letters 'AN' for Army-Navy, as in AN/SPS-6. |
| War Status: Used by US Battleships,
introduced in late 1941
Installed: Mounted on Main Battery Directors Purpose: Fire Control Power: 15-20 KW Wavelength: 40 cm PRF: 1,640 Transmitter Dimensions: 12 x 3 feet (3.66 x 0.91 m) Tracking Range: 40,000 yards (37,000 m) Range Accuracy: 40 yards (37 m) Bearing Accuracy: 2 mils Resolution: 400 yards (370 m) and 10 degrees Notes: First USA set to use lobing. 16" (40.6 cm) shell splashes could be ranged at 20,000 yards (18,500 m). |
| War Status: Used on Mark 37 and
Mark 33 directors, installed September 1941.
Purpose: Fire Control of 5" (12.7 cm) guns. Power: N/A Wavelength: 40 cm PRF: N/A Transmitter Dimensions: 6 x 6 feet (1.83 x 1.83 m) Tracking Range: 40,000 yards (37,000 m) on for bombers and 30,000 yards (27,000 m) for large ships. Range Accuracy: 40 yards (37 m) Bearing Accuracy: 4 mils Resolution: 400 yards (370 m) and 10 degrees Notes: Effectively, this set was two half-Mark 3 antennas stacked vertically. Could not track low-flying aircraft. |
| War Status: Used by US Battleships,
introduced in l1942-43
Installed: Mounted on Main Battery Directors Purpose: Fire Control Power: 15-20 KW, later 20-30 KW Wavelength: 10 cm PRF: N/A Transmitter Dimensions: 10.2 x 3.3 feet (3.1 x 1 m) Tracking Range: 40,000 yards (37,000 m) on Battleship sized target Range Accuracy: 15 yards (5 m) Bearing Accuracy: 2 mils Resolution: 400 yards (370 m) and 10 degrees Notes: Scanned via pulse-switching. Mark 8 mod 0 could spot 16-inch (40.6 cm) splashes out to about 20,000 yards (18,300 m) and the improved Mark 8 mod 3 could reliably spot 14-inch (35.5 cm) and 16-inch (40.6 cm) fire out to at least 35,000 yards (32,000 m). |
| Mark 12
War Status: Used on Mark 37 directors,
installed 1944.
Notes: Replaced the Mark 4. Had automatic tracking in range and measurement of range rate. Mark 22 Transmitter Dimensions: 1.5 x 6 feet
(0.46 x 1.83 m) [known as the "orange peel"]
Notes: Used solely to detect low flying aircraft at 0.8 degrees above the horizon. Ranges much as for the Mark 12. |
| War Status: Used by US Battleships
and Cruisers
Installed: Mounted on Main Battery Directors Purpose: Fire Control Power: 50 KW Wavelength: 3 cm PRF: 1,800 Transmitter Dimensions: 8 x 2 feet (2.44 x 0.61 m) Tracking Range: 40,000 yards (37,000 m) on Battleship sized target Range Accuracy: 15 yards (5 m) Bearing Accuracy: 2 mils Resolution: 400 yards (370 m) and 10 degrees Notes: This radar could discern individual shell splashes from 16-inch (40.6 cm) projectiles out to over 42,000 yards (38,400 m). |
| War Status: Used on Destroyer Escorts
with Mark 52 FCS
Purpose: Range-only Band: S Power: 50 KW Wavelength: 15 cm Transmitter Dimensions: 36 in (0.9 m) (truncated paraboloid) Tracking Range: Bomber at 10,000 feet is 15,000 yards. Fighter at 1,000 feet is 700-12,000 yards. Range on a ship is 400-25,000 yards. Maximum Tracking range is 27,500 yards. Range Accuracy: 100 yards Notes: Lightweight system for smaller warships. |
| War Status: Standby radar mounted
on Control Towers and sometimes turrets.
Purpose: Range-only Power: 50 KW Wavelength: 10 cm Transmitter Dimensions: N/A Tracking Range: N/A Range Accuracy: 160 yards (146 m) Bearing Accuracy: 6.5 degrees Notes: This radar replaced optical rangefinders on the top of battleship control towers. |
| War Status: Used on Light AA Directors
Mark 33 and Mark 57
Purpose: AA Band: X Power: 30 KW Wavelength: 15 cm PRF: 1,800 Transmitter Dimensions: 45 in diameter (1.14 m) Tracking Range: A fighter could be detected at 15,000 yards (13,700 m). Range Accuracy: 15 yards (14 m) +/- 0.1% of range Bearing Accuracy: 4 mils |
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BB-33 Arkansas 1942 : SRa / SC
BB-34 New York 1938 : XAF /
BB-35 Texas 1938 : CXZ /
BB-36 Nevada 1942 : SRa / SRa
BB-37 Oklahoma No radar installed before Pearl Harbor BB-38 Pennsylvania 1941 : CXAM /
BB-39 Arizona No radar installed before Pearl Harbor BB-40 New Mexico 1942 : SRa / SRa
BB-41 Mississippi 1944 : SRa / SK , SRa
BB-42 Idaho 1942 : SRa / SRa
BB-43 Tennessee 1942 : SC / SRa (before rebuild)
BB-44 California 1941 : CXAM /
BB-45 Colorado 1942 : SC , SRa / SRa
BB-46 Maryland 1942 : SC /
BB-48 West Virginia 1941 : CXAM /
BB-55 North Carolina 1942 : CXAM /
BB-56 Washington 1942 : CXAM /
BB-57 South Dakota 1943 : 2 x SRa , SC-2 /
BB-58 Indiana 1943 : SC /
BB-59 Massachusetts 1943 : SC-2 /
BB-60 Alabama 1942 : SC /
BB-61 Iowa 1943 : SK, SRa /
BB-62 New Jersey May 1943 - May 1945 : SK /
SG (Also SG on forward FC tower)
BB-63 Missouri 1944 : SK-2 /
BB-64 Wisconsin 1944 : SK /
Notes: XAF: Large sized rectangular antenna, first installed in BB New York 1938, later removed. CXZ: Similar to XAF. First installed on Texas, later removed. CXAM: Installed 1940-1 on some US battleships, later removed. SC: rectangular antenna with a greater width. SR : Small sized but longish antenna shaped as an inverted V, installed in older battleships, some arrangements with two antennas were known. SG: Small sized navigational and surface search antenna. Small profile resulted in little mention when ship recognition addressed. SK: Large, rectangular, elongated antenna with headpiece. Mainly used on carriers, destroyers and escorts. Rarely used on battleships. SK-2: Large, round parabolic antenna with wide open work metal grating. Replaced SK in most battleships, cruisers and aircraft carriers by end of war. SP: A smaller sized round parabolic antenna with closer grating, introduced in last part of war as secondary antenna system. Always carried in after position. SG-6: One of the first post war antennas. Installed in limited numbers and soon replaced by SPS-6 SPS-6: One of the larger air-search antennas of the SPS series. Introduced in post war years, installed on numerous ships including Iowa class which were the only battleships to be so equipped. SPS-8A: "Highfinder" surveillance radar system. Installed on Iowa class around 1950, replacing SP. Older version installed on AG-128 Mississippi in 1949 and some aircraft carriers SPS-10: Carried forward with SPS-6 radar. Large rectangular system along with the ECCM frames. SPS-49: Surface Search radar. |
"U.S.
Radar: Operational Characteristics of Radar Classified by Tactical
Application (1943)" at US Naval Historical Center
Modern-day
US Radar Systems listing at FAS