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

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).
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