Tachi-6 Early Warning Radar

Photograph of Taichi-6 radar transmitter antenna
Photograph of Taichi-6 radar receiver antenna
National Archives. Via Nakagawa (1997)


Wavelength 441, 416, 394, or 375 cm
Pulse Width 10-70 microsecond
Pulse Repetition Frequency     
500 or 1000 Hz
Power 50 kW
Range 125 miles (200 km) aircraft group
Nondirectional box or crossed dipole transmitter
Dipole array receiver
22,000 lb
10,000 kg
Production 350 sets from 1942-6

The Japanese Tachi-6 early warning radar, also described by some Allied sources as the CHI Mark 229 and originally designated by the Japanese as Type B Fixed Early Warning Device (Chotampa Kei-kai-ki Otsu, Yochi-yo), saw wide operational use in the war. It had remarkable range for its very simple design, consisting of a nondirectional transmitter strung to a tree and up to four separate receiving antennas sheltered in tents and rotated by hand. The Japanese considered it their most reliable and important early warning radar. Examples were captured at Noemfoor and Wewak, and it became known as the Wewak Radar to the Allies. It had almost no altitude determination capability and was awkward to install in remote locations.

Grunden (2005)

Guerlac (1987)

Nakagawa (1997)

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