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Rotor radar system

AN/FPS-6 Height Finder Radar

AN/FPS-6 Height finderTwelve General Electric AN/FPS-6 height finding radars were purchased from the United States government at the beginning of 1952 to augment the aging British Type 13 radars. Height finder radar aerial radiation patterns feature narrow vertical and broad horizontal beam widths. The aerial nods up and down at 20 or 30 cycles per minute and can rapidly slew in azimuth (Azication) to face the bearing of the target that you want to find the height of.

The 12 inch Range Height Indicator (RHI) display shows range against height on a CRT. The required target was marked on the height operators display by a strobe that was initiated from a PPI operator's console. Initiating this strobe caused the height finder radar to swing around to face the target azimuth   The height operator aligned his cursor to the centre of the indicated radar paint on his height display and the height was then calculated by equipment in the Radar Office. The calculated height was then displayed on an indicator adjacent to the operator console requesting the height.

In the lower picture a man is climbing on the slew and tilt mechanism, giving an impression of the antenna size.

The specifications for the AN/FPS-6 were:
Frequency: 2700 to 2900 MHz
Power Output: 5 Mw, peak
Power Source: QK-338A
Range:300 nautical miles
Vertical Coverage: - 2o to + 36o
Vertical Scanning Rate: 20 or 30 cpm
Azimuth Resolution: 3.2 deg
Elevation Accuracy: 1000 ft
Horizontal Beam Width: 3.2 degrees angular
RHI 12" CRT.
Height range: -5000 to + 35,000 ft.
Azimuth range: 0 to 200 miles.
Elev angle marks at 5 deg. intervals.
Input: 120/208V 60Hz AC.
Mfr: GE.
Type: OA-929/FPS-6.


Technical Specs: (According to the Radio Research catalog)

The FPS-6 radar is capable of height determination of targets flying between elevation angles of -2o and +32o for any azimuth throughout 360o

The transmitter develops a peak power of 5 Megawatts at a frequency range of 2.7 to 2.9 GHz. The pulse width is 2 usec at a PRF of 400 PPS.

Maximum indication range is 200 nautical miles with height measurement capability to 75,000 feet. Both ranges are readily expandable.

Data is displayed on two 12 inch RHI indicators and mechanical counter assemblies. The antenna type is a truncated semiparabolic reflector with associated waveguide feed sections. Input power requirements are 208V, 3 phase, 60 Hz.

This radar is also suited for very high power search functions.

The specifications for British operated versions of the AN/FPS-6 were:

Frequency band

E/F band (S-band)


2700 - 2900 MHz

TX power

2.5 MW


250 - 270 pps

Pulse width

4.7 uS


Single channel


FTC (Fast Time Constant)


SG (Swept Gain)


Amplitude Nois Limiting

Vertical coverage

-2o to +32o

Editors note: I am indebted to Kelvin Holmes for providing the technical details of British operated versions of the AN/FPS-6


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Updated 02/02/03

Constructed by Dick Barrett


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ęCopyright 2000-2003 Dick Barrett

The right of Dick Barrett to be identified as author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.