Desperate War of Japan in the Pacific
Imperial German Navy had tried radio detecting experiment in 1912. German Navy developed decimeter 0.8 - 1.5m radar called DT in 1930s. Otherwise a few RN cruisers were equipped with surface radar in spring of 1941.
Krancke, p13

GEMA radar of wave length 0.5m suceeded in detecting a small warship at range of 12km in 1934 and 15km in the end of 1935 by pulsed ocillator. Admiral Graf Spee was equipped with FMG39G of 0.8m wave length, when WWII broke out on Sep 1939. While USS battleship Texus was equipped with 0.8m CXZ, and HMS Rodney with 7m 79Y.
Maru, p79 No694

Specifications of Type 271
Wave length10cm
Power5 - 90kW
Pulse width1.5us
Horizontal beam
Vertical beam20°
AntennaRetangular parabola
Type 271
HMS Suffolk tracked German battleship Bismarck using an experimental surface searching radar in May 1941.
H.M.S. Suffolk sights and chases Bismarck

HMS battleship Prince of Wales's surface searching radar was not operational, when she and IJN flag ship heavy cruiser Chokai came near 50 nm each other at fog midnight.

UK shipbuilt a lot of small escort warships for ASW. Corvette of the Flower class were equipped with a microwave radar, Type 271. First fitted to corvette HMS Orchis in May 1941.
British Naval Radar Equipment of World War II

AI Mk 3 was 200MHz and 20us of pulse width. So the least detecting range was 330m. It was not operational. AI Mk 4 was 130m of the least range and operational in August 1940. 3,000 sets were producted till the end of 1942.
Gunzo, p24 No94
Kouku-ki tousai radar

NRL could detect a flying aircraft using contineous wave at 8,000ft off 10mi in 1930. NRL could generate 10us width pulse in 1934.
Tokuda, p218

TypeWave lengthPower
SC radarUSS Lady Lex
USN developed XAF in 1938, and had already tested XAF radar equipped USS New York in the Caribbean Sea in May 1939. Anti air searching radar CXAM equipped 6 warships including battleship Calfornica, aircraft carrier Yorktown in 1940. Duplexer and PPI (Plain Position Indicator) were developed. The last one was developed by NRL (Naval Research Laboratory) and Western Electric in 1941. FC(Fire Control) radar and FD (Anti Air) radar was developed in 1941. CXAM radar were equipped with 3 USN aircraft carriers in the battle of Midway. USS Yorktown's CXAM detected enemy aircraft of Hiryu off 80km. The photo shows radars on USS Lady Lex. You find a radar like a shape of a fan guard which was a famous CXBL or SM radar. The radar could detect an aircraft flying at low altitude and measure an alitude of enemy aircraft. The direction of enemy aircraft was detected by SK and SC radar. The photo shows a view of USS Long Island's masthead with the SC radar antenna and anemometer on 13 March 1942. As for microwave radar, USN developed 10cm wave length surface searching radar SG in 1942. SG radar worked a range of 35km against a surface vessel compared with 10km of SK[1]
DenshiHeiki, p43-58

US Government commisioned Bell Laboratory to develop a SJ radar in 1938. Bell made a trial in December 1941, and made a trial for submarine in April 1942[2]. Western Electric productioned at once.
Gunyo radar kaihatsu monogatari
Eibei ga micro ha radar wo kyodokaihatsu suru
Beikoku kansen tousai radar no kyusokuna shinpo
Radar(denpa tanshingi)

USA developed a microwave radar in a laboratory. The labo was called the Radiation Laboratory.

    Half of the radar deployed during World War II was designed at the Rad Lab, including over 100 different radar systems (such as the SCR-584 radar), and $1.5 billion worth of radar.
4,000 people worked there at peak.

USN developed varioust type radars.
Radar Development In America
Historic Naval Ships Association

The Oldest Working Radar (1943) - USS COBIA SJ-1 s/n 37

    US aircraft carrier
    USS Cabot (CVL-28)USS California
    USN made CAP system supported by radars well in the the Pacific War. TG58 had 10 CVs, 6CVL, 8 BBs, 16 CLs and dozens of DD in Okinawa Battle. TG58 deployed two radar picket destroyer groups to defend themselves on 18 March 1945. The two picket groups were in the north and the west off 48km of the TG58[5]. The TG58 itself was the east off 150km of Kyushu. Even light aircraft carrier had got CIC (Combat Information Center). IJN never thought of the idea. USN deployed warships offshore 150km of the Zanpa Cape. From 48 to 120 fighters flew an oval path at daytime[4]. US deployed radars at Hedo Cape of Okinawaon on 21 April and Iejima on 23 April[4].
      A view of the island of USS Cabot (CVL-28). USN photo via Floating Drydock. Judging from Air Group 29's (VF-29 & VT-29) scoreboard this picture was probably taken in October (or perhaps November) 1944.

      The curved antenna of the surface search SG radar is seen on the raised circular platform. Forward of and below it is the SC-2 air search radar antenna. A second air search radar (SK) was installed on a stub mast between the pairs of uptakes — all fleet carriers were fitted with two air search sets as insurance against the failure of one of them in combat, and the wide separation of both main radars aboard CVL's often resulted in better radar performance than that enjoyed by the heavier and larger CV's. (c)David Buell

    US battleship
    The photo shows the radar for 5"/38 guns and main guns of USS California

Land radar
IJA finished a flying aircraft detection test using contineous wave officially in 1939. The detection system was called Denpa Keikaiki Ko. The systems were installed in China and Japan. As for early warning pulsed land radars, See land radar.
Tokuda p223

IJN established NRL in 1923 at the same time as well as USN did. Tani of Japanese NRL proposed a radar study in 1936. He judged it important from UK recent patent claims. But his boss refused of the notable comment after the Pacific War. Tani evaluated Yagi aerial array highly. Instead of him, Itoh took up his position. I do not know why Tani would continue the study. It seems that Itoh ignored Yagi's method, though Yagi recommended him to study in Germany. Tani and Itoh graduated University of Tokyo, while Yagi was not a professor of University of Tokyo, but Tohoku University and Tokyo Institute of Technology.
Nakagawa, p29
Gunzo, p94-101, No70
Nihon ga radar kaihatsu wo hajimeru
Differences of Technical Officers of Army and Navy

IJN began to study microwave radar with Shinnihonmusen in 1939. IJN experimented receiving 10cm wave length echo of aircraft carrier Akagi off Tsurumi on 10 October 1940. But IJN was late for developing the practical radar.
Kaigun radar tsurezuregusa
Denpa heiki
Electronics de kanpai sita Kaigun��Kaigun no seisaku shita dentan(radar)

The photo shows warning air radar Type 13 installed ground at Kisarazu in Chiba for experiment. However, The type 13 could not measure direction and altitude of targets. The Antenna was for short wave radio originally.

Warship Radar

    1. Aircraft Carrier
      Syokaku was equipped with an AA radar for the first time among IJN carriers in July 1943. Its radar caught US aircraft at 6045 time far away 145km, and Syokaku controlled CAP in the battle of the Santa Cruz Islands.
      Nakajima, p116

      While USN had already done CAP at the battle of Midway. The CAP was controlled in CIC of aircraft carriers.

    2. Battleship

      Wave lengthPowerWeight
      Type 211.5m5kW850kg
      Type 10310cm2kW-
      A trial radar equipped old battleship Ise and Hyuga each just before the battle of Midway. Ise was equipped with Type 21. Hyuga was equipped with Type 103 which was prototype of Type 22. The size of the antenna of Type 103 was 1.5m diameter and 2m length. It was called maguro (tuna).

    3. Cruiser
      An improved Type 22, which was called Type 22 kai1, equipped IJN heavy cruiser Atago. The radar detected enemy fleet well in the battle of Mariana in May 1943. So the 2nd Fleet could got off chasing US fleet, because the Type 22 kai1 adopted a kind of autodyne circuit invented by JRC (Shinnihonmusen). And replacing low sensivity Type 22 kai1, next Type22 kai2 adopted solid state diode. The kai2 was operational fully in October 1944 at last. It was too late. More than 100 set of kai2 were in stock in the end of the Pacific War.

    4. Destroyer escort
      Type 22Type 13
      A few warnign air radars were equipped with larger warships at first. So submarines, destroyer escorts and destroyers were late, they were busier with escort and patrol than large warships.

      The photos show radars of Shisaka, Hiburi class destroyer escort that was taken on 16 September 1945 at Yokosuka after surrender. Type 22 was a surface searching radar. Type 13 was an air warning radar.
      Sekai no kansen, No.507
      Kaigun 3shiki 1go denpa tanshingi 3gata

    5. Submarine
      Type 22Bridge of I-402
      The photos shows surface searching radar of IJN and USN. The right photo shows Bridge of IJN submarine I-402. The right is Type 13 at the right of the bridge. The radar antenna of warning aircraft was for an airborne radar originally. The antenna was developed by IJN aircraft department. So warship department disagreed the equipment. A submarine captain persuaded Kure Arsenal to equip. The trial equippment happened to be a good result.

      IJN submarine I-58 was equipped with a trial surface searching radar in February 1943. The radar could detect a floating submarine in the front at range 2,000m only. But air warning radar Type 13 of I-58 detected an enemy aircraft the next mission on 3 March 1945. I-58 could be afloat an hour and 10 minutes only during 2 days in April 1945 in the battle of Okinawa. Hashimoto Mochitsura (1909-2000), a captain of I-58 was not afraid of a sudden airborne attack in July 1945. The type 13 helped warning aircraft correct. Type 22 did not detect an enemy, when I-58 suceeded to sink USS heavy cruiser Indianapolis on 27 July 1945. Nor did a radar of Indianapolis. He worked at a submarine maker of previous Kawasaki Heavy Industries, Kawasaki zousen now after the Pacific War.
      Hashimoto p.219, 285, 319, 384

Airborne radar
I do not know the fact that Japanese airborne intercept radars could be effective in combats, though airborne searching radars were useful in some cases. Some IJN Myrt and IJA Nick were equipped with airborne radars. They warned flying enemy aircarft in the south of Shikoku and Honshu before air combats.

IJN and IJA developed independent airborne radars as the same as aircraft guns. Why couldn't IJN and IJA cooprate to develope radars one another? The specifications are as follows,

Specification of Japanese airborne radars
SearchH-62m110kg70km (aircraft)
20-30km (submarine)
SearchTaki-11.5m150kg20km (submarine)-Mar1943-IJA
InterceptFD-20.6m70kg0.5-3km (aircraft)100Aug1944-IJN 302nd kokutai of no use
InterceptTaki-20.8m120kg0.5-3km (aircraft)-Jan1945-IJA 53rd sentaiapplied for 2 aircraft, of no use

IJN made a trial of PPI airborne radar in the end of the war. The radar was called Type 51. Takayanagi of NHK Laboratory proposed at first. Getting 3cm PPI radar equipped with a shotdown B-29, IJN tried wavelength 10cm PPI radar. The trial of the radar tested well on a flying Betty at Misawa Base on 8 August 1945.

However, more than 20,000 US aircraft had been already equipped with 60cm surface searching radar on USN bombers and torpedo bombers by 1943.
Giken p196, p288, p254
Watanabe, p392-393
PPI Hyoji

 Action radars worked important in the sea
DateTimeWeather ActionTypeWarship
1941Mar270500-1040fog and snowDetection of watch cruiserDTAdmiral Sheer
1943Jul200000-1400fogWarning entrance of Kiska BayType22Shimakaze
1944Nov282030-0305cloudy, wind scale 4Track of ShinanoSJArcherfish
1945May160210calm, clear Search and bearing293 PPIVenus

USS Archerfish
Crews of ArcherfishSJ & SD radar
Enright used SJ radar when USS Archarfish chased IJN aircraft carrier Shinano. Then Archerfish sank her. The SJ radar contributed to sink a lot of Japanese merchant ships. The left shows crews of USS Archarfish. The front extreme left man was a radar officer.
Enright Shinano!

IJN Destroyer Shimakaze
IJN Destroyer ShimakazeKimura
Kimura Masatomi commanded withdrawal of 5,200 troops in Kiska. He requested GF a destroyer equipped with a surface searching radar. Shimakaze was the fisrt destroyer with Type22 radar. The photo shows it on the front mast of her, and her full speed trial on 5 May 1943.

Kriegsmarine Admiral Graf Scheer
Kriegsmarine Admiral Graf ScheerHMS Norfolk
Scheer passed the Denmark Strait sucessfully twice. Theodor Krancke commanded her. A mechanic of Scheer broke down to find disorder of her radar, though breaking down was forbbiden.

HMS Destroyer Venus
HMS VenusIJN Heavy cruiser Haguro
HMS Destroyer Venus made a radar contact ranging 60km at first. IJN heavy cruiser Haguro the contact ranging 20km. Destroyer Kamikaze's captain remembered that Haguro speeded up and the distance was more 1km. So Kamikaze speeded up too. The Haguro told the Kamikaze by wireless phone, but Kamikaze could not understand because of noise or something. 5 minutes later or less, Haguro suddenly turned and lighted fired.
Andaman heno yusosakusen
The Sinking of the Haguro

 Scientific background in Japan
Why did Japan fail to innovate wireless technology such as radars, though IJN introduced wireless telegram to messenger ships like Shinano Maru in the Japanese-Russo War. Some authors in Japan writes Yagi array antenna and magnetron invented in Tohoku University. Although they criticize IJN, It seems important why scientists in Japan ignored these inventions in academic societies of Japan, rather than IJN.

Western scientists studied light since Newton for a long time. I think scientific experimental discovery and love were important to stimulate studies for radars. F. W. Herchel found heat effect of infra red in 1800. A. Ampére showed this was electro magnetice wave in 1835. G. Kirchhoff found law of radiation in 1859 and thought concept of black body. Stefan-Boltzmann's radiation law in 1884. Wien's law in 1893. M. Planck integrated L. Rayleigh and J. H. Jeans' law in long wave length and Stefan-Boltzmann's law in short wave in 1896.

I suppose that few scientists studied devices based radiation principle of electron and very few scientists studied propagation in wireless communication. Only NHK laboratory and a few colleges in technology studied it. While US government decided to spend a lot of money in the field of radiation science, though Japan spent much wartime money on China at that time.
Takashima, p15-21

[1] Tokuda, p228
[2] NHK1, p160-163
[3] Okinawa, p118
[4] Okinawa, p124
[5] Okinawa, p56

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