Site Records

Site Name: RAF Kilchiaran Chain Home Low Radar Station

Kilchiaran Farm
Island of Islay
OS Grid Ref: NR207616

Sub Brit site visit 16th August 2004

[Source: Nick Catford with technical notes on CHL by Howard Toon]

In January 1941 a Chain Home Low radar station became operational at Kilchiaran, on the west coast of the island of Islay.

A chain of radar stations known as Chain Home has been established around the country in 1939 to detect incoming enemy aircraft. Only aircraft at fairly high altitudes could be tracked by this method, however, and low-flying aircraft or surface shipping could not be detected.

To overcome this problem, a second chain, more or less alternating with the first and integrated into the same reporting system, was created and known as the ‘Chain Home, Low’ (CHL). The radars were based on the Coastal Defence radars used by the Army. Initially the Chain Home Low stations required two separate aerials, one for the transmitter and one for the receiver, mounted on 20 foot high gantries, with the equipment housed in a hut underneath each gantry.

A typical Chain Home Low technical block

Since CHL operated on a wavelength of 1.5 metres the aerials were short enough that the arrays could be rotated, using cranks and a chain-driven system from inside the hut.

The operators had to synchronise both aerials but the result was a beam about 25° wide, rather than the floodlight effect of CH. The aerials were not continuously rotated but, instead, were aimed at the target and moved from side to side to get the best reading.

The received echo was displayed on a single trace on a cathode-ray tube. This display gave slant range to target only. Information about possible targets, detected at fairly long range by CH, could be passed to the CHL for tracking at lower levels as well as the CHL feeding information back through the CH stations to the filter rooms.

Late in 1940 single arrays (which combined transmitting and receiving aerials) were introduced. These motorised aerials rotated constantly and gave a continuous reading. This new system also allowed the target to be more accurately detected and allowed multiple targets to be tracked on a single display.

Photo:The CHL technical block
Photo by Persons Name

Initially an AMES Type 2 radar was fitted at Kilchairan although Type 31 and 52 centimetric radars were installed later on in the war, the station closed down in 1945 as part of the contraction of early warning coverage just prior to the end of the war.

RAF Kilchairin was reactivated in the 1950's as part of the ROTOR radar programme which included the building of a new R11 technical block to the east of the old CHL block. The station finally closed in 1958.

The CHL block is the only building surviving on the technical site. The windows and doorways were bricked up following the closure of the station and the building is currently empty and unused although still in good external condition.

The domestic camp was at Kilchiaran Farm, 1.5 kilometres to the south in Kilchairin village, here a number of buildings survive, now put to farm use. One of the buildings, a standby set-house was reused during the rotor period.

A further building and some hut bases can also be seen at Baelach na Caillich, a headland 450 yards to the south west of the technical site. These may be part of the reserve CHL station.

[Source: Nick Catford with technical notes on CHL by Howard Toon]

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