Japanese Radar FK-4
Prototype 19 Ku 1 Model 13

十九試空一号電波探信儀十三型 (19-shi kū-1 Gō Denpa Tanshingi 10-gata ta, Protoype 19 Ku 1 Radio Probe Model 4 The FK-4, was to be a high power, large search radar to be mounted on large patrol planes. Like the FK-3, the FK-4 had two indicators, one for the pilot and one for the radar observer. The project started in June 1944, but was stopped in July 1945 before the first prototype could be completed after it was destroyed by air raids.

Reports of the U.S. Naval Technical Mission to Japan

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Technical Specifications

十九試空一号電波探信儀十三型 / Protoype 19 Ku 1 Radio Probe Model 13
Designation			FK-4
Object			Patrol and Search
Research	started		June 1944
	Finished		July 1945
Operational status			Research stopped
Installation			Large aircraft
Frequency			2 meter / 150 kHz
Power Output (Peak)			20 kw
Pulse Length			20 µs
Repetition Frequency			83 c/s (500 c/s * 1/6)
Weight			unknown
Units build			0 (prototype incomplete)
Transmitter	Oscillation Circuit		Modulated Oscillator
	Oscillator Valve		K-3006 x2
Receiver	Intermed. Freq.		10 mc
	Detector		1st UN-954	2nd SORA
	Local oscillator		UN-955
Scope Representation	Diameter		120 mm
	Scanning Axis		Linear
	Scale		Mechanical
Antenna	Type		Head: Yagi	Sides: Folded Doublet
	Gain		16db	6.5db
	Beam Angle	Horiz.	θƒ = 30°	θƒ = 28°
		Vertical	θƒ = 35°	θƒ = 30°
Max. Range (Max.Effective Scale)			300 km theoretical 150 km against large ships
Minimum Distance			5 km at 1000 m
Accuracy of Range			≃± 5%
Distance Discrimination			5 km
Accuracy of Bearing			± 3°
Angle Discrimination			≃ 60°
No. Of Operators			Radar Technician

Sources

• Defense Technical Information Center. (1945). A Short Survey of Japanese Radar. Volume 1.
• Defense Technical Information Center. (1945). A Short Survey of Japanese Radar. Volume 3.
• Mikesh, R. C. (2004). Japanese aircraft equipment: 1940-1945. Atglen: Schiffer Pub.
• Reports of the U.S. Naval Technical Mission to Japan, 1945-1946. (n.d.) (Vol. E-02 Japanese Airborne Radar).