Designations

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.

From Naval Radar by Norman Friedman

Fire Control Radars

Mark 3

FC
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

First USA set to use lobing. 16" (40.6 cm) shell splashes could be ranged at 20,000 yards (18,500 m).

Mark 4

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

Effectively, this set was two half-Mark 3 antennas stacked vertically. Could not track low-flying aircraft.

Mark 8

War Status Used by US Battleships, introduced in 1942-43
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

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 with Mark 22 Height Finder

Mark 12
War Status Used on Mark 37 directors, installed 1944.
Purpose Fire Control of 5" (12.7 cm) guns.
Power 100-110 KW
Wavelength 33 cm
PRF 480
Transmitter Dimensions 6 x 6 feet (1.83 x 1.83 m)
Tracking Range 45,000 yards (41,000 m) on for bombers and 40,000 yards (37,000 m) for large ships.
Range Accuracy 20 yards (18 m)
Bearing Accuracy 3 mils
Resolution 300 yards (270 m) and 7 degrees

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")
Power 25-35 KW
Wavelength 3 cm

Used solely to detect low flying aircraft at 0.8 degrees above the horizon. Ranges much as for the Mark 12.

Mark 13

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

This radar could discern individual shell splashes from 16-inch (40.6 cm) projectiles out to over 42,000 yards (38,400 m).

Mark 26

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

Lightweight system for smaller warships.

Mark 27

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

This radar replaced optical rangefinders on the top of battleship control towers.

Mark 28

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

Search Radars

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

Became Operational 1941
War Status Operational
Purpose Surface Search
Wavelength 10 cm
Power Output 70 KW
Range 15.7 nm

Small sized navigational and surface search antenna. Small profile resulted in little mention when ship recognition addressed.

SF-1

Became Operational 1942
War Status Operational
Purpose Surface Search
Wavelength 10 cm
Power Output 150 KW
Range 16 nm

SL

Became Operational 1942
War Status Operational
Purpose Surface Search
Wavelength 10 cm
Power Output 250 KW
Range 21 nm

SO-13

Became Operational 1943
War Status Operational
Purpose Air/Surface Search
Wavelength 10 cm
Power Output 75-200 KW
Range 16 nm Surface/ 35 nm Air

SK

Became Operational 1944
War Status Operational
Purpose Air Search
Wavelength 150 cm
Power Output 250 KW
Range 162 nm

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.

Search Radars on US Battleships of World War II

Compiled by Steve Dyer

BB-33 Arkansas

Years Forward Aft
1942 SRa SC
1944 SRa SK
1945 SK , SRa

BB-34 New York

Years Forward Aft
1938 XAF
1942 SC, SRa SRa
1944 SRa SRa
1945 SK

BB-35 Texas

Years Forward Aft
1938 CXZ
1942 SRa SRa
1943 SRa SC , SRa
1948 SRa SK , SRa

BB-36 Nevada

Years Forward Aft
1942 SRa SRa
1943 SK , SRa SRa
1945 SK , SRa SRa

BB-37 Oklahoma

No radar installed before Pearl Harbor.

BB-38 Pennsylvania

Years Forward Aft
1941 CXAM
1943 SRa SRa , CXAM
1945 SK-2 , SP

BB-39 Arizona

No radar installed before Pearl Harbor.

BB-40 New Mexico

Years Forward Aft
1942 SRa SRa
1944 SK , SRa SRa

BB-41 Mississippi

Years Forward Aft
1944 SRa SK , SRa
1949 ? SPS 8A
1954 SPS 6 SPS 8A
1956 SPS 6 SPS 8B

BB-42 Idaho

Years Forward Aft
1942 SRa SRa
1944 SK SRa

BB-43 Tennessee

Years Forward Aft
1942 SC SRa (before rebuild)
1943 SK SC-2
1945 SK SC-2

BB-44 California

Years Forward Aft
1941 CXAM
1944 SK SP

BB-45 Colorado

Years Forward Aft
1942 SC , SRa SRa
1945 SK, SRa

BB-46 Maryland

Years Forward Aft
1942 SC
1944 SK , SRa SRa

BB-48 West Virginia

Years Forward Aft
1941 CXAM
1944 SK
1945 SK-2

BB-55 North Carolina

Years Forward Aft
1942 CXAM
1943 SK
1945 SK-2 SC-2
1962 SK-2 SP

BB-56 Washington

Years Forward Aft
1942 CXAM
1944 SK
1945 SK-2 SP

BB-57 South Dakota

Years Forward Aft
1943 2 x SRa , SC-2
1944 SK

BB-58 Indiana

Years Forward Aft
1943 SC
1944 SC , SRa
1945 SK

BB-59 Massachusetts

Years Forward Aft
1943 SC-2
1944 SK
1965 SK-2 SC-2

BB-60 Alabama

Years Forward Aft
1942 SC
1943 SK
1945 SK-2 SR
1964 SK-2 SR

BB-61 Iowa

Years Forward Aft
1943 SK, SRa
1945 SK-2, SC-2
1950 SPS-6 SP
1952 SPS-6 SP
1958 SPS-6 SPS-8A

BB-62 New Jersey

Years Forward Aft
May 1943 - May 1945 SK SG (Also SG on forward FC tower)
June 1945 - February 1952 SK-2, SG SP
April 1952 - August 1954 SPS-6, SPS-10 SP
December 1954 - deactivation in 1957 SPS-6, SPS-10 SPS-8A HF
Reactivation in 1967 - deactivation in 1968 SPS-6, SPS-10
Reactivation in 1982 - deactivation in 1990 SPS-49

BB-63 Missouri

Years Forward Aft
1944 SK-2
1947 SK-2 SP
1950 SG-6 SP
1951 SPS-6 SP
1954 SPS-6 SPS-8A

BB-64 Wisconsin

Years Forward Aft
1944 SK
1947 SK SC-2
1952 SPS-6 SPS-8A
1954 SPS-6 SPS-8A
1957 SPS-6 SPS-8A

Sources

  • "Naval Weapons of World War Two" by John Campbell
  • "The Naval Institute Guide to World Naval Weapon Systems 1991/92" and "Naval Radar" both by Norman Friedman
  • "The Evolution of Battleship Gunnery in the U.S. Navy, 1920-1945" article in "Warship International" No. 3, 1991 by William Jurens
  • "Battleship New Jersey" by Paul Stillwell
  • "Battleships of the US Navy in World War II" by Stephan Terzibaschitsch