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DEPARTMENT OF THE NAVY -- NAVAL HISTORY AND HERITAGE COMMAND
805 KIDDER BREESE SE -- WASHINGTON NAVY YARD
WASHINGTON DC 20374-5060
Online Library of Selected Images:
WEAPONS and SENSORS -- RADAR
U.S. Navy Shipboard Radars -- CXAM
In October 1939, following the successful testing of the experimental
XAF radar and several months of educating
private company personnel in radar technology, the Navy contracted
with the Radio Corporation of America (RCA) for six production
versions of the XAF. Deliveries began in May 1940, and during
the summer these were installed on a half-dozen warships: the
battleship California,
aircraft carrier Yorktown,
and heavy cruisers Pensacola,
Northampton,
Chester
and Chicago.
With a large "bedspring" configuration antenna (17-feet
by 18-feet) mounted in a rotating yoke, the CXAM was identical
in configuration to the XAF and, as with the latter, the antenna
could be elevated. At 5000 pounds total installation weight (1200
pounds for the antenna), this radar was suitable only for big
ships. A follow-on effort to build radars with smaller antennas
led, not without technical difficulties, to the SC type that was
entering widespread service when the Pacific War began in December
1941.
The CXAM operated in the relatively long wavelength (1.5 meters,
200 megacycles) "P-Band", with a pulse power of 15 kilowatts.
It could detect large aircraft flying seventy nautical miles away
at 10,000 feet altitude, smaller combat planes at fifty miles,
large ships at sixteen and destroyers at twelve nautical miles.
This long-range performance against aircraft made it most useful
for air search, a role it pioneered for other low-frequency, large-antenna
U.S. Navy shipboard radars that served during the next many decades.
Its elevating antenna was found to be of minimal value for long-range
air search, but it did demonstrate potential for distant UHF communications
and as an over-the-horizon radar. To save weight and similify
design, the Navy's subsequent large wartime search radars, including
the CXAM-1, SA, SC, SK and SR-types, had non-elevating antennas.
The CXAM's distinctive appearance makes it easy to identify
in photographs taken between mid-1940 and early 1943. The cruisers
Chester and Chicago originally carried their CXAM's
antennas atop their mainmasts, but in 1942 these were relocated
to the top of the ships' foremasts. California's radar
was removed in late 1941 or early 1942, while she was under salvage
in the aftermath of the Japanese attack
on Pearl Harbor. This set was reportedly the one installed
on the carrier Hornet
in mid-1942. Northampton's CXAM was replaced by a CXAM-1
sometime before April 1942 and its further career, if any, is
unknown. Those carried by Yorktown, Hornet and Chicago
sank with their ships on (respectively) 7 June 1942, 27 October
1942 and 30 January 1943. Pensacola's and Chester's
were damaged by shock and vibration when those cruisers were torpedoed
in October and November 1942, and, if they survived to return
to the United States, were replaced by more modern radars when
the ships were repaired and overhauled in 1943. The CXAM on Chicago
was undoubtedly the last of its type to see operational service.
Source note: Most of the information in this text is taken
from the following sources: Captain L.S. Howeth, USN: History
of Communications-Electronics in the United States Navy, Chapter
XXXVIII (Washington, D.C., 1963); and Norman Friedman: Naval
Radar (Greenwich, England, 1981).
This page features, and provides links to, a selection of
images concerning the U.S. Navy CXAM type radar.
For additional information on the CXAM type radar, and on
World War II era radar in general, see the Navy Department Library's
"Online Reading Room" presentation:
"
U.S.Radar - Operational Characteristics of Radar, Classified by
Tactical Application" -- publication FTP 217, 1 August 1943.
Click on the small photograph to prompt
a larger view of the same image.
Photo #: 19-N-32465-A
Antenna for CXAM radar
Mounted atop the foremast of USS Chester (CA-27). Taken
at the Mare Island Navy Yard, California, 6 August 1942.
This image is cropped from Photo
# 19-N-32465. See Photo
# 19-N-32465-B for for an different version of this image,
darkened to emphasize the antenna wires.
Photograph from the Bureau of Ships Collection in the U.S.
National Archives.
Online Image: 55KB; 650 x 675 pixels |
 |
Photo #: 19-N-32465-B
Antenna for CXAM radar
Mounted atop the foremast of USS Chester (CA-27). Taken
at the Mare Island Navy Yard, California, 6 August 1942.
This image is cropped from Photo
# 19-N-32465, and has been substantially darkened to emphasize
the antenna wires. See Photo
# 19-N-32465-A for an undarkened version, providing better
details of the antenna structure.
Photograph from the Bureau of Ships Collection in the U.S.
National Archives.
Online Image: 85KB; 650 x 675 pixels |
 |
Photo #: 80-G-12147-A
Antenna for CXAM radar
Mounted atop the foremast of USS Pensacola (CA-24). Photographed
at Sand Island, Midway, 25 June 1942. The antenna is elevated
in its supporting yoke.
This image is cropped from Photo
# 80-G-12147.
Note the forms of men working on the antenna in the center and
toward the left.
Official U.S. Navy Photograph, now in the collections of the
National Archives.
Online Image: 44KB; 650 x 675 pixels |
 |
Photo #: 80-G-312018-A
Antenna for CXAM radar
Mounted on the foretop of USS Yorktown (CV-5). Photographed
during the Battle of Midway, 4 June 1942.
The antenna and its supporting yoke are somewhat obscured by
the upper structure of the foretop, the topmast, the mast's yard
(with a ladder hanging from it and signal balls on two of its
halliards) and the U.S. ensign flying from the mast.
This image is cropped from Photo
# 80-G-312018.
Official U.S. Navy Photograph, now in the collections of the
National Archives.
Online Image: 68KB; 650 x 675 pixels |
 |
Photo #: NH 105858-A
Antenna of CXAM radar
Atop the foremast of USS Pensacola (CA-24), circa early
August 1942.
The smaller antenna of an FC (or Mark 3) fire control radar is
in the lower part of the image, mounted atop the ship's main
battery gun director.
This image is cropped from Photo
# NH 105858.
Official U.S. Navy Photograph, from the collections of the
Naval History and Heritage Command.
Online Image: 54KB; 610 x 765 pixels |
 |
ADDITIONAL VIEWS: Seven ships carried CXAM radars, six (a
battleship, an aircraft carrier and four heavy cruisers) receiving
newly-built sets in 1940 and the last (another aircraft carrier)
getting a second-hand unit in mid-1942. The views listed here
for each ship show the CXAM's antenna as a small part of each
image:
USS California
(BB-44) received the CXAM in mid-1940. It was on board her
during the 7
December 1941 attack on Pearl Harbor and was removed while
the ship was under salvage. Subsequently employed by the U.S.
Army as a shore-based air warning radar on Oahu, in the summer
of 1942 it was reportedly installed on the aircraft carrier Hornet
(see below).
The following photograph shows the CXAM
radar's antenna mounted on USS California:
===>Photo
# NH 64474: USS California sinking on 7 December 1941.
The antenna of her CXAM radar is visible atop her pilothouse (in
the center of the image).
USS Yorktown
(CV-5) had a CXAM atop her tripod mast at least by the beginning
of October 1940. It remained on board the ship for the remainder
of her career, sinking with her during the June
1942 Battle of Midway.
The following photographs show the CXAM
radar's antenna mounted on USS Yorktown:
===>Photo
# 80-G-21931: USS Yorktown arrives at Pearl Harbor,
27 May 1942. The antenna of her CXAM radar is visible on her foretop
(in the image's left center).
===>Photo
# 80-G-13065: USS Yorktown in dry dock at Pearl Harbor,
29 May 1942. The antenna of her CXAM radar is seen edge-on atop
her foretop (in the image's upper left-center).
===>Photo
# 80-G-312018: View on board USS Yorktown during the
Battle of Midway. The antenna of her CXAM radar is visible on
her foretop (in the upper left of the image). For a closeup
view, cropped from this image, see Photo
# 80-G-312018-A.
===>Photo
# 80-G-21666: USS Yorktown listing and abandoned, 4
June1942. The antenna of her CXAM radar is faintly visible on
her foretop (in the image's center).
In the summer of 1942, following the Battle of Midway, USS
Hornet (CV-8)
had a second-hand CXAM (reportedly that removed from USS California
-- see above) installed on her tripod foremast, where it replaced
a smaller antenna, probably that of an SC type. The latter was
remounted on the ship's after mast. The CXAM remained on board
the ship for the remainder of her career, sinking with her during
the October 1942 Battle of the Santa Cruz Islands.
The following photographs show the CXAM
radar's antenna mounted on USS Hornet:
===>Photo
# 80-G-33947: Japanese airplane diving on USS Hornet,
26 October 1942. The antenna of her CXAM radar is visible on her
foretop (in the image's left-center).
===>Photo
# 80-G-34110: Preparing to abandon USS Hornet, 26 October
1942. The antenna of her CXAM radar is seen on her foretop (in
the image's upper left-center). The antenna of a smaller radar,
presumably an SC, is partially visible atop the after mast, in
the top right-center.
===>Photo
# 80-G-40300: Close-up view of USS Hornet's island,
26 October 1942. The antenna of her CXAM radar is partially visible
atop her tripod foremast (in the top left of the image).
The antenna of the CXAM fitted to USS Pensacola
(CA-24) is seen in a number of 1942 photographs. A post-action
view shows that this antenna was missing its mounting a few weeks
after the ship was torpedoed during the Battle of Tassafaronga,
and Bureau of Ships "War Damage Report No. 35" (page
9) states that radar antennas were damaged by flexural vibration
at that time.
The following photographs show the CXAM
radar's antenna mounted on USS Pensacola:
===>Photo
# 80-G-12147: USS Pensacola at Midway, 25 June 1942.
Her CXAM radar's antenna is seen in an elevated aspect atop her
foremast (in the top left-center of the image). For a closeup
view, cropped from this image, see: Photo
# 80-G-12147-A.
===>Photo
# NH 105858: USS Pensacola underway in Hawaiian waters,
circa early August 1942. Her CXAM radar's antenna is seen nearly
edge-on atop her foremast (in the top center of the image). For
a closeup view, cropped from this image, see: Photo
# NH 105858-A.
===>Photo
# 19-N-34705: USS Pensacola anchored in a south Pacific
port, 28 September 1942. The antenna of her CXAM radar is visible
atop her foremast (in the center of the image).
===>Photo
# 80-G-33862: USS Pensacola undergoing battle damage
repairs, 17 December 1942. The antenna of her CXAM radar is missing
from her foremast, and may have been knocked off, or damaged and
subsequently removed, when the ship was torpedoed on 30 November.
The antenna of the CXAM fitted to USS Northampton
(CA-26) is seen in several 1941 photographs. It appears to
have been replaced by a CXAM-1 by April 1942.
The following photographs show the CXAM
radar's antenna mounted on USS Northampton, or show that
it had been replaced by another type:
===>Photo #s NH
94596 and NH
95333: USS Northampton at Brisbane, Australia, 5 August
1941. Her CXAM radar's antenna is visible atop her foremast (in
the top center of these images).
===>Photo
# 80-G-32548: USS Northampton in Pearl Harbor, 8 December
1941. The antenna of her CXAM radar is visible atop her foremast
(in the image's center).
===>Photo
# NH 97808: USS Northampton refueling at sea, April
1942. The radar antenna atop her foremast is that of a CXAM-1,
not a CXAM.
The antenna of the CXAM fitted to USS Chester
(CA-27) is seen in photographs taken in late 1941 and in 1942.
The 1941 photo shows it mounted on her mainmast, while those taken
in August 1942 shows that it had been moved to the top of her
foremast. This radar was replaced by an new SK type when the ship
was repaired after her 20 October 1942 torpedoing.
The following photographs show the CXAM
radar's antenna mounted on USS Chester:
===>A photograph of USS Chester and USS Northampton
operating in Hawaiian waters on 8-12 December 1941, shows that
Chester's CXAM antenna was then mounted atop her mainmast.
We do not have a reproducible copy of this photo, but believe
that it one of several film frames cataloged under National Archives'
Photo # 80-G-21012 (possibly 80-G-21012-S). Contact that
agency concerning the availability of reproductions of this
image, which shows Chester in the foreground (starboard
bow surface view), with Northampton partially visible beyond
her. Chester is painted in what appears to be Camouflage
Measure 2.
===>Photo
# 19-N-32461: USS Chester off the Mare Island Navy
Yard, 6 August 1942. Her CXAM radar's antenna is seen atop her
foremast (in the left portion of the image). ===>Photo # 19-N-32465:
USS Chester at the Mare Island Navy Yard, 6 August 1942.
Her CXAM radar's antenna is seen atop her foremast (in the top
center of the image). For closeup views, cropped from this
image, see: Photo #s 19-N-32465-A
and 19-N-32465-B.
The antenna of the CXAM fitted to USS Chicago
(CA-29) is seen in photographs taken during 1942 and early
1943. Those taken up through August 1942 the year show it mounted
on her mainmast, while in those taken in December 1942 and later
it is at the top of her foremast. This radar was lost with the
ship in late January 1943, and was certainly the last CXAM in
active service by that time.
The following photographs show the CXAM
radar's antenna mounted on USS Chicago:
===>Photo
# 80-G-7293: USS Chicago and other ships at Fiji in
February 1942. Her CXAM radar's antenna is atop her mainmast (in
the right-center of the image). ===>Photo
# 80-G-K-306 (color): USS Chicago and other ships off
Guadalcanal, 9 August 1942. Her CXAM radar's antenna is still
on her mainmast (in the right-center of the image). ===>Photo # 19-N-39220:
USS Chicago at the Mare Island Navy Yard, 14 December 1942.
Her CXAM radar's antenna is seen edge-on atop her foremast (in
the top left-center of the image).
===>Photo
# 19-N-39212: USS Chicago off the Mare Island Navy
Yard, 20 December 1942. Her CXAM radar's antenna is seen atop
her foremast (in the left-center of the image).
===>Photo
# NH 55141: USS Chicago disabled by Japanese torpedoes,
30 January 1943. Her CXAM radar's antenna is seen atop her foremast
(in the center of the image).
NOTES:
To the best of our knowledge, the pictures referenced here
are all in the Public Domain, and can therefore be freely downloaded
and used for any purpose.
Some images linked from this page may bear obsolete credit lines
citing the organization name: "Naval Historical Center".
Effective 1 December 2008 the name should be cited as: "Naval
History and Heritage Command".
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Page made 18 June 2008
Coding updated 11 May 2009