Site Records

Site Name: RAF Sopley ('AVO') R3 GCI ROTOR Station

OS Grid Ref: SZ162978

RSG site visit 23rd May 2000

[Source: Nick Catford]

By 1943 the station had evolved into a GCI 'final' with a brick operations blocks, known as a 'Happidrome' (named after a BBC comedy radio programme featuring a farcical music hall where nothing seemed to go as planned and nobody quite knew what was happening - much like a GCI!!) in an adjacent field on the opposite side of the road to the intermediate site.

This consisted of a large brick built control centre with integral machine and plant rooms, a telephone exchange, GPO equipment room and an operations room with intercept cabins in raised galleries around the reporting room floor.

Photo:The reporting room in Sopley GCI final (happidrome). The general situations map (left) is a replica of the operations map at Sector. It displays all information received from the Observer Corps and Filter Room. The local situation map indicates positions of fighter aircraft. The room is overlooked by three cabins; Chief Controller, Fighter Controller and
Anti Aircraft Liaison Officer & Searchlight Controller

The reporting room had two horizontal plotting tables with a vertical 'Tote' board detailing the status of flights and raids which could be viewed from the elevated controller's cabin. One plotting table at Sopley showed the regional situation, the other the local picture.

From the elevated cabin, a Supervisor would oversee the entire situation whilst an Allocator would allocate fighters and intercepts to individual fighter controllers, who would then control the radar interceptions. The controllers and their assistants were situated in cabins behind the controller. There would be direct phone lines to the wider air defence organisation, manned by an assistant.

On the plotting table metal arrows show the position and direction of contacts. WAAF's used metal poles with magnetic tips to manipulate the arrows which were colour coded in coordination with an RAF sector clock with 5 min colour sectors to show the most recent plot information.

If the station was busy, a WAAF supervisor maintained the wall mounted tote board and added additional data to the arrows such as a contact number and a classification of the contact as Hostile or Friendly. The tote board would have listed the local RAF night fighter stations, including Hurn and Middle Wallop, their night fighter squadrons with whom Sopley worked the aircraft available and their status

Room layout of Sopley GCI Final (happidrome)

Detailed layout of equipment and personnel in the operations area of Sopley Final GCI

A standby generator was housed in an adjacent building (standby set house). The final installation had a single rotating aerial array with the transmitter and receiver housed in an underground well beneath.

The station was built for an AMES Type 7 search radar initially operating on a frequency of 209 MHz, and later on 193 and 200 MHz. This was a parallel development of the Chain Home Low (CHL) equipment by the addition of a height-finding capability and a Plan Position Indicator (PPI) display. In a PPI display the cathode ray tube is scanned radially from the centre of the tube face. The bearing of the scan is synchronised to the rotating aerial and the intensity of the beam is modulated by the signals received from the aerial.

The effective range of the GCI station was 90 miles with a range of 30 miles at 1000 feet. In order to provide communication between the controllers in the Happidrome and the intercepting aircraft, two VHF/UHF multi-channel radio transmitter and receiver blocks were built at remote sites to stop interference and swamping of the radio signals by the radar arrays. Sopley GCI also provided information for anti-aircraft (HAA) gun sites.

In 1943 Winkton Airfield was built a short distance to the south east of the radar site. It acted as an advanced landing ground for the 404th Fighter Group of the American 9th Airforce coming into use on 4th April 1944.

Prior to the invasion of Europe in June 1944 Allied use of 'window' had proved a great hindrance to CH, CHL & GCI wavelengths. Therefore high frequency equipment was installed at certain GCI stations where the narrow beam width would reduce the echoes from 'window' to a minimum. This equipment was entitled AMES Type 21 Mk1 and consisted of two equipments: AMES Type 14 Mk 3 and AMES Type 13 Mk 2; both centimetric sets. The former consisted of a PPI unit rotating at 6 rpm and the latter was the associated height finding unit capable of giving a height reading in any direction. 15 GCI stations were thus equipped in early 1944, all being installed and operational by June, RAF Sopley was one of these stations. (Ref: radar in raid reporting App 51)

(Window was a jamming technique consisting of half wavelength strips of aluminium which were dropped in bundles from aircraft; it was shiny on one side and black on the other. When bundles were dropped every strip reacted as an aircraft to German radar)

Click here to continue the history of RAF Sopley

[Source: Nick Catford]

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