Type 13 CMH
Description of the radar set, tactical-technical characteristics
Figure 1: Type 13 CMH height-finder on Malta in World War 2,
photographed by a French soldier
|pulse repetition time (PRT):|
|pulse repetition frequency (PRF):||500 Hz|
|pulsewidth (τ):||0.6 or 1.9 µs|
|peak power:||500 kW|
|hits per scan:|
Type 13 CMH
Type 13 CMH (CentriMetric Heightfinder) was operating in S-Band nodding height-finder. It was the Royal Air Force’s first centimetric radar and was developed to improve height information at Ground Controlled Intercept (GCI) radars.
The prototype used two vertically mounted cheese antennas to give an aperture of 20 feet by 3 feet fed by each a H-plane Sectoral Horn. The narrow vertical beam of 1.5° was nodded vertically from -1° elevation to +20° elevation at 6 cycles per minute. The horizontal beamwidth was 7.5°. The display was an E-scope which was used to measure the height of an aircraft using a nomogram.
The development of the Type 13 CMH started in September 1942 and was put into production in March 1943. There have been several modernizations. The first Type 13 Mk II was operational in early 1944. The Type 13 Mk III and IV were similar to the Mk II. The Type 13 Mk V had a much improved antenna using a single curved parabolic reflector fed by a slotted waveguide (see Marconi S 239).