Site Records

Site Name: RAF Ventnor Chain Home Radar Station

St. Boniface Down
Ventnor
Isle of Wight
OS Grid Ref: SZ568785

Sub Brit site visit 1st October 2004

Following the development of radar at Orfordness and at the Bawdsey Research Station in Suffolk during the mid 1930's, the Air Ministry established a programme of building radar stations around the British coast to provide warning of air attack on Great Britain. A survey was undertaken in 1938 to assess the suitability of the local terrain for Air Defence Radar operations with the first of these new stations coming on line by the end of the year. This network formed the basis of a chain of radar stations called CHAIN HOME (CH).

These stations consisted of two main types; East Coast stations and West Coast stations. The East Coast stations were similar in design to the experimental station set up at Bawdsey in 1936. In their final form these stations were designed to have equipment housed in protected buildings with transmitter aerials suspended from 350' steel towers and receiver aerials mounted on 240' timber towers.

RAF Ventnor - transmitter towers in the foreground

The West Coast stations differed in layout and relied on dispersal instead of protected buildings for defence. Thus the West Coast stations had two transmitter and receiver blocks with duplicate equipment in each. Transmitter aerials were mounted on 325' guyed steel masts with the receiver aerial mounted on 240' timber towers.

Ventnor was one of 20 CH stations authorised in 1937. The site, on St. Boniface Down would give good long range performance but because there was no level ground in front of the masts it wouldn't be capable of height finding.

In order to provide immediate cover an 'advance' station was established using experimental transmitters and receivers installed in temporary hurts. Ventnor was one of eight such locations. Once the 240' receiver towers were completed at the end of October 1938, the station went to an 'intermediate' stage using the experimental equipment and temporary aerials mounted on two of the towers. The intermediate station was operational by 26th January 1939. The station went onto 24 hour watch from Easter 1939 and was put on a war footing on 24th August 1939

During this period, work continued on the final Chain Home installation with the building of four 365' transmitter towers spaced 180ft apart during the summer of 1939. This was later reduced to three. This was because of the urgency involved in the Chain Home programme, the 'state of the art' of prewar radio technology and the shortage of steel. It was originally planned that each station would operate on four spot frequencies in the 50-20 MHz range, (6-15 metre wave length), with the transmitting aerials suspended between the platforms at 50, 200 and 350 feet. However, it was soon found that the radiation pattern was not as good as it theoretically should have been and to overcome the difficulty, a larger curtain array of dipoles and reflectors, suspended on high tensile steel cables slung between towers, was the answer.

At the same time it was decided that four frequencies per station would lead to delays and was, in any event, unduly optimistic of achievement. The number of frequencies was reduced to two in the 30-22 MHz range, (10 -13.5 metre bands). As two suspended arrays could be supported between three towers, (the middle one being common to both arrays), those stations still under construction would have one tower deleted. The fourth tower was dismantled and shipped to Skaw in the Shetlands.

In October 1939 a Chain Home Low station was also planned for Ventnor. This was to be built by the army in a separate compound within the boundary of the Chain Home Station. This station was to be known as Boniface Down with the code number M86.

On 12th August 1940, four CH stations were selected for attack by the Luftwaffe. After causing damage to the radar stations at Dover, Rye and Pevensey the bombers headed for Ventnor where they were intercepted at the start of their raid. The station suffered considerable damage which forced it off the air and most of the buildings were damaged or destroyed; casualties were however light with only one soldier being injured.

Following this raid a mobile installation was brought on to the island and set up at Bembridge. It was operational from 23rd August 1940 and remained in use until the station was repaired. As a result of this attack, it was proposed by the Air Ministry that the majority of Chain Home stations should be provided with reserve equipment, either underground or remotely sited. Buried reserves were provided at the more vulnerable stations (i.e. those on the east and south coast) consisting of underground transmitter and receiver blocks. On some stations the transmitter and receiver buried reserves were together on an adjoining site (often the next field).At others the two buried reserves were separate but located close to their respective above ground building.

Three of the four receiver towers at Ventnor

Many of the West Coast stations had remote reserves some distance from the main station but utilising similar above ground transmitter and receiver blocks. Most stations were powered from the National Grid but they were also provided with generators to cover interruptions in the mains electricity supply. Each reserve would also have a 120' wooden aerial tower. While the reserves were under construction mobile radio units were deployed as reserve stations.

Ventnor was provided with buried reserves located together close to the southern perimeter fence. They were not ready for use until well into 1942.

For further information and pictures of RAF Ventnor click here

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