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Tachi-3 Fire Control Radar


Photograph of Tachi-3 radar transmitter antenna
Photograph of Tachi-3 radar receiver antenna
National Archives. Via Nakagawa (1997)


Specifications:


Wavelength     
385 cm
Pulse width
1-5 microseconds
Pulse repetition frequency      
1875 Hz
Power
50 kW
Range 25 miles (40 km) aircraft
Antenna
Transmitter: 5 element Sterba ground array of individual dipoles at 20 feet (6 m) elevation
Receiver: five horizontal dipoles in diamond array
Accuracy Poor
Weight
8800 lb
4000 kg
Production About 150 sets from 1943


The Tachi-3 was a land-based radar. It was known in prototype as the Mark Ta Model 3 (Chijo-yo Dempa Hyotei-ki, 3-gata) and was based in part on a captured British Mark II gunlaying radar from Singapore. Like many Japanese radars, it used separate transmitter and receiver antennas. The transmitter could be electronically steered in altitude but was mechanically steered in azimuth. The receiver used five separate dipole antennas, four of which employed lobe switching to determine altitude and azimuth while the fifth was used to determine range. Each set controlled six 120mm and six 88mm antiaircraft guns.

It was plagued by interference from ground reflection and had poor resolution. As a result, it was to be replaced by Tachi-24, a Japanese version of the German Würzburg, but the war ended before the latter could go into mass production.

It was deployed only to Formosa and the home islands

References

Grunden (2005)

Guerlac (1987)

Nakagawa (1997)


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