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Radar in Northern Ireland 1939 – 1945

One rainy afternoon in lockdown, I thought I would do some research on finding evidence for the WW2 radar sites that were once dotted around Northern Ireland. Finding photographic evidence of what were once secret installations is still quite tricky almost 80 years on! I have been fortunate enough to visit some of these sites throughout my years of research, so have some modern evidence of their existence, but others remain illusive. Hopefully this article will help to bring together some of the existing evidence, both photographic and documentary to shed some light on the story.

This article was written based on books and online research during the closure of public records archives in May 2020. I hope to refresh and update this research as I am able to collect more information. If you have anything that you would like to contribute to help inform the information here, you can do so using the contribute form at the bottom of the page. The article is being updated as my knowledge develops.


By 1937, the first five Chain Home (CH) systems were operational across the east coast of England, with a further 13 announced in 1938, and by the start of the war in 1939 there were 19 stations operational. By 1940 CH stations stretched across the UK, including Northern Ireland. The main purpose of radar is in the air defence (AD) role typically operated by the Royal Air Force (RAF), although the Royal Navy operated radar in the land based Coastal Defence (CD) role, and the army operated Gun Laying (GL) radar associated with anti-aircraft gun batteries. Radar was to prove an essential part of the national air defence schemes that would protect our skies, and ground targets.

Belfast incurred heavy losses after being woefully underprepared for the unexpected air raids of 1941. That said, there were already 6 radar stations in Northern Ireland by that time (Blake), but only 24 heavy guns for air defence and one squadron of fighter aircraft based at Aldergrove. After the raids, the strategic importance of Northern Ireland and the fact that being an island nation did not make them a softer target was realised, and defences hurriedly reinforced. The imminent arrival of the Americans into Northern Ireland later in 1941 would see the distribution of a network of radar stations across the country and a “comprehensive system of air raid reporting” essential to assist the inbound fighter squadrons. In late 1941 a radar station was also constructed in the heart of the Belfast shipyard, presumably in support of Coastal Defence (Blake).

Tabulating the deployment of air defences (as detailed by Blake) helps us to see the increased response to the realised vulnerability of Northern Irish industry and population during 1941. Searchlights and barrage balloons were also a key part in the air defence plan of Northern Ireland, but I have not included them in this research.

LocationHeavy Anti-Aircraft Guns (3.7″)Light Anti-Aircraft Guns (40mm)Fighter Squadrons
Belfast (Port)166
Londonderry (Port)4Nil
Larne (Port)44
Aldergrove (Airfield)Nil4245 (Hurricane) Fighter Squadron
Limavady (Airfield)Nil4
Air defences prior to the raids of April 1941 (Blake). A Heavy Anti-Aircraft (HAA) battery typically consisted of 4 guns, so Belfast had four HAA batteries, and the naval ports of Londonderry and Larne each had one.

Later in 1941, after a review of NI air defences, a new Fighter Command Group (No. 82 Group) was formed, headquartered in parliament buildings at Stormont. Three sector stations were subsequently formed at Belfast, Lough Foyle and Lough Erne, each potentially operating up to two fighter squadrons. In the end, no fighter squadron was sent to Lough Erne, and only one moved to Eglinton for the protection of Londonderry. These new sectors were also reflected in the increased ground defences allocated to the areas.

LocationHeavy Anti-Aircraft Guns (3.7″)Light Anti-Aircraft Guns (40mm)Fighter Squadrons
Aldergrove (Airfield)UnknownUnknown
Ballyhalbert (Airfield)NilNil153 (Night Fighter) Squadron
245 (Hurricane) Fighter Squadron
Belfast (Port)566
Eglinton (Airfield)NilNil133 (Spitfire) Fighter Command
Larne (Port)UnknownUnknown
Londonderry (Port)28Nil
Limavady (Airfield)UnknownUnknown
Lisahally (Port)166
Lough Foyle (Port)44
Lough Erne (Air Base)816
The air defences for Northern Ireland had considerably increased by the end of 1942 (Blake)

As the tide turned in Europe, and as the Battle of Britain was won, the need for an integrated air defence network on home shores was reduced. By May 1944 all heavy guns had been removed from the defence of Londonderry, and in August 1944 the last heavy gun was removed from Belfast. Even the earliest anti-aircraft batteries would only have been operational for around 4 years.

Conjecture on the part of the author places the 6 existing pre-1941 radar sites based on their site designations of 59/59A/60A/61/61A/61B. Each main CH site having an associated CH Low (CHL) site to fill in the low level radar gaps of the CH system. While I have no construction dates for these sites were, they appear to have been operational by April 1941. The earliest site to be constructed may have been the radar site at Glenarm which is detailed in Table 3 as being constructed sometime between September 1939 and July 1940. More information on each site is covered later in this article, but they were located at:

Chain HomeChain Home Low
Castlerock 59Downhill 59A
Blackhead 61BGlenarm 60A
Greystone 61Roddens Port 61A
Radar sites operational in Northern Ireland by April 1941.

With the CH system operational around the coast, early warning could be given on the approach of hostile aircraft across the English Channel. Based on the air defences of the time of the first raid, air raid sirens would have sounded, and this would have alerted the modest number of gun crews to man their posts, bearings of approach would have been passed but engaging the targets would have been reliant on visual methods and the use of aiming predictor computers, along with search lights (not co-located with the guns) illuminating the aircraft. It would take the development of technology before anti-aircraft guns would have their own radar (known as Gun Laying radar) to assist them, and before fighter squadrons had a dedicated system to direct them onto the hostile aircraft (called Ground Control Intercept radar).

Early Radar Development

There are some great books and articles on the technological development of radar during WW2, and I won’t go into great detail here, but by understanding how a radar system worked, we can better understand the remains at sites scattered across our country.

Considered technologically primitive in comparison to modern radar systems, the development of what became the Chain Home (CH) network stemmed from a 1935 experiment now known as the Daventry Experiment to assess the feasibility of using radio waves to disable aircraft; they were to design a death ray. While I hope we all appreciate that this never came to fruition, what did transpire was that the detection of reflected radio waves could be used to not only detect aircraft but measure their range from the transmitter, initially out to a range of 8 miles, day or night. And at this moment, Radio Detection, Direction Finding (RDF) was born. It is interesting to note that the term Radio Aid for Detection and Ranging (RADAR) was only devised in 1940 by the United States Navy and not adopted in Britain until 1943, later it appears to have been shortened to Radio Detection and Ranging.

Transmitters emitted a short pulse of 20 μs (micro seconds) at a rate of 50 Hz (50 times a second) on one of four frequencies between 20-55 MHz (or mega-cycles as it was known at the time), later between 20-30 MHz. The power of these pulses was huge, up to 750 kW (kilo-Watts) considering your mobile transmits at around 1 Watt, radar is 750,000 times more powerful! At this level of power, aircraft could be detected at a range of around 100 miles, to an accuracy of about 1 mile. In order to calculate the range of an aircraft, the time was calculated between the transmitted pulse and the received echo.

An output from the range tube of a Chain Home Low (CHL) station showing echoes from a single aircraft at around 50 miles © IWM E(MOS) 1446.

Unlike the scanning radar we know today, the CH network was fixed, so in order to provide adequate coverage the area was floodlit with the pulsed radio energy. However, while the system may have been simple, the coastal CH network proved to be a strength of the system. With this in mind, we can ascertain that there will be a number of features on radar sites, CH at least, that we may find:

  • Transmitter aerials
  • Transmitter building
  • Receiver aerials
  • Receiver building
  • Generator building if the site is not connected to the National Grid.

As the war and technology, progressed, transmitters became smaller and more efficient, and much late-war radar equipment was mobile, contained in trailers, and these systems leave little or no trace in the landscape.

The Chain Home (CH) Network

Chain Home (CH) radar was developed in the 1930s to give Britain an Early Warning (EW) system to detect and react to enemy aircraft approaching from the Continent. It could give a range, bearing and height of suspected hostile aircraft formations. Two designs of CH site were constructed, varying between the east and west coasts of the UK.

East Coast Site Plan

On the east coast, CH sites had four 107m tall wooden transmitter towers, with four smaller 73m receiver towers. The transmitter and receiver wires were strung between these masts, and due to being with reach of enemy bombers, the control buildings were reinforced and covered with earth.

Representative diagram of a typical east coast CH site layout.
A map of east-coast type Chain Home stations across the United Kingdom, including the original sites and those added between September 1939 and July 1940. Glenarm was the only site added in this time in Northern Ireland. Original source of the image is unknown, copy from

West Coast Site Plan

West coast buildings, and those in Northern Ireland, had only two 73m receiver masts and used four guyed steel masts to support the transmitting antenna. The control buildings were also covered in earth and scattered around the site to mitigate the risk of damage to all buildings if attacked from the air. Another variation on some west coast sites was the inclusion of a buried reserve; backup equipment in subterranean buildings.

Representative diagram of a typical west coast CH site layout.

Dobinson also details three levels of CH site construction, those being Advance Chain Home (ACH) for sites that were rushed into operation, Intermediate Chain Home (ICH) where sites had some temporary buildings to support their operations and Final, permanent sites.

Chain Home Low (CHL)

Chain Home Low (CHL) was a system developed from the CD (Coastal Defence) radars that were first installed to detect coastal shipping in 1939, but were repurposed to detect low-flying aircraft. CHL stations of the early war period were simpler than a CH station, usually of two buildings, a transmitter and receiver, sited within 0.5 miles of the coast, and approximately 70 meters apart. Each CHL building had a gantry on which the aerial was mounted. This aerial could be turned manually, changing the direction of the beam. The system was no longer a floodlight system like the CH. Stations constructed after 1941 would have been much simpler, consisting of a single building approximately 15×5.5m in size, with a single, mechanically and continuously rotating aerial.

Radar gantry and aerials, World War II Chain Home Low (CHL) radar station, The Ward, Deerness, Mainland, Orkney Islands. This was known as a 1941 Type CHL station.

Sites constructed or upgraded as part of the expansion in 1941 were known as “1941 Type” sites. Sites that were to be upgraded were not retrofitted with new equipment, but a new station was build along side to 1941 DGW (Director General Works) plans. These newly fitted out sites were known as “1941 Type duplicates” to differentiate them from new builds or sites that had not been upgraded. The new 1941 Type sites consisted of a single array constructed on a 20ft gantry, accompanied by a large 50″x18″ operating building. It was planned that as part of the rolling upgrades to radar stations that each site would accommodate two such stations, alternating between new and older technologies (Dobinson).

Chain Home Extra Low (CHEL)

A system developed in 1942 to detect aircraft out to 30 miles flying between 80 and 200 feet above sea level, CHEL stations were almost exclusively deployed along the east coast fo England. Utilising a scanning beam as opposed to the floodlight method of the CH system, by 1943 a mixture of 4 low level stations, 5 mobile stations and 6 CHEL aerials on towers had been installed.

It appears that Northern Ireland received CHEL upgrades to three existing stations in support of operations running up to Overlord. This happened in around February 1944 and involved Downhill, Glenarm and Greystone.

Ground Controlled Intercept (GCI)

Historic England says “GCI stations were developed by the Air Ministry from 1940 to detect, locate and track enemy aircraft and provide inland radar coverage of Britain. (…) Mobile stations comprised transmitter and receiver aerial arrays mounted on trailers spaced no more than 220ft (67.1 metres) apart, with equipment stored and operations carried out from trucks. (…) Intermediate GCI sites typically comprised a single aerial array mounted on a gantry and a 50ft by 18ft (15.2m by 5.5m) non-metallic operations hut. Additional on-site buildings (often) included a small power house, huts for offices and recreation, and a guard hut for the site entrance.

GCI stations varied in size and facilities from small and highly mobile systems (known as Type 15) through heavier but transportable systems (Type 8) through to the final design of large fixed installations (known as Happidromes or Type 7). The final design of the GCI radar was ready by June of 1941 and the Type 7 was developed to that design in six months. The Type 7 GCI radar provided multiple controlling facilities, an improved aerial, improved height finding and longer range than previous mobile versions (

Delays in delivering Final GCI equipment between 1941 and 1942 resulted in delivery of the “short term improvement programme.” This applied to both mobile and transportable stations; Intermediate Mobile (IM) and Intermediate Transportable (IT) respectively. This taxonomy had history in the upgrading of CH stations in 1940 (Dobinson). At the end of this programme, NI had only one Final GCI station at Ballywoodan.

Anti-Aircraft Radar

In the early days of the war, anti-aircraft radar sets had to be raised off the ground. This was done by means of a radar platform, of which only a few remain in Northern Ireland; Groarty Road, Culmore, Magilligan and Island Magee. These ramps were surrounded by a wire mesh in order to create an artificial horizon (20th Century Defences in Britain, CBA). As technology developed, there was no longer a requirement for the radar platform, and the mobile radar sets could be kept at ground level, often making it difficult to ascertain their presence at a site.

Anti-Aircraft Radar on Orkney 1944 © IWM H 39422

An Integrated Air Defence Network

The strength of UK air defence during WW2 came from the network of components that worked to bring the right resources onto a hostile target. Radar formed part of the early warning network, with Chain Home systems being able to detect potential incursions out to 100+ miles. Notification of any detected aircraft would have been passed back to the filter room at fighter command where multiple sources would have been fused together.

At each one of Northern Irelands three sectors from 1941 onwards, information would also have been received from their GCI radars, visual observations by the Royal Observer Corps (ROC) and there is evidence of one D/F station that would have tracked our own fighters as they intercepted the raiders. From a defensive view, the up to date information about the aircraft would have been passed to barrage ballon units, as well as the light and heavy anti-aircraft batteries and to the scrambled fighters.

An archived image from 2013 that was previously hosted on the RAF website detailing all of the elements that made up the UK air defence system during WW2.

Reference in contemporary literature is made to a ‘triple-service’ system. Not only did the RAF operate RDF or radar for the early warning of aircraft, but still bu 1941 the Army operated low level radar covering beaches identified as possible landing zones, and the Royal Navy operated Coastal Defence (CD) radars. The sites were distinct from the Chain Home (Dobinson) but standardisation was going to become an imperative in 1941.


You can expand the layers and select what sites to view by using the layer tab at the very top left of the Google Maps window. View the map in full screen.

NameDesignationSite TypeSite Survey DateOperation StartOperation EndNotes (page numbers from Building Radar)
AntrimCHMarch 1940Site rejectedN/Ap282, 288
ACH standard equipped with MB2 set
Ballinderry27GMobile GCIAugust 1941October 1941
June 1944 assumed reporting role
July 1944 (dismantled)p393, 523, 541
June 1944 assumed a quasi-CH reporting role during Overlord.
Dismantled immediately in the summer of 1944.
BallycranmoreCHLSeptember 1940N/AN/Ap325
Site wish list, not developed
Ballydonaghy (Bally Donaghy)26GGCIAutumn 1942Summer 1944 all non-Final stations closed.
Blanket closures in effect 1 February 1945
Late 1941Late 1943 / early 1944
Blanket closures in effect 1 February 1945
p418, 522
Recommended for mothballing
Ballywoodan29GMobile GCI
Final GCI (Autumn 1943)
August 1941October 1941
Upgraded to final Autumn 1943
Blanket closures in effect 1 February 1945p395, 487, 523
Assumed a reporting role in May 1944
Bishops Road26GMobile GCIAugust 1941October 1941Summer 1944 all non-Final stations closed.
Blanket closures in effect 1 February 1945
Blackhead61BCD / CHLTransferred from Army in May 1942June 1944 all chain stations in NI to decommission .
Blanket closures in effect 1 February 1945
Castlerock59ACHNovember 1940 (ACH installed)June 1944 all chain stations in NI to decommission.
Blanket closures in effect 1 February 1945
CrossmaglenType 9 MRUApril 1942Summer 1944 (dismantled)p412, 541
CHEL (Feb 1944)
September 1940November 1940
CHEL upgrade February 1944
Exempt from closures on 1 February 1945p325, 345, 419, 524
Received a 1941 Type upgrade.
CHEL upgrade February 1944 pre-Overlord
CHEL (Feb 1944)
May 1940July 1940
Upgraded 1941
CHEL upgrade February 1944
June 1944 all chain stations in NI to decommissionp305, 367
Yagi-equipped single-drive array as opposed to twin gantry.
CHEL upgrade February 1944
CHEL (Feb 1944)
January 1941CHEL upgrade February 1944 Late 1943 / early 1944
Blanket closures in effect 1 February 1945
p412, 522
Substitute for an earlier site planned at Kirkhiston (Kirkistown) Castle.
CHEL upgrade February 1944.
Recommended for mothballing.
Kilkeel78CHJanuary 1941April 1942Late 1943 / early 1944
Blanket closures in effect 1 February 1945
p398, 522
Recommended for mothballing
Lisnaskea28GMobile GCIAugust 1941October 1941Summer 1944 all non-Final stations closedp393
NewtownbutlerMRU (CH)April 1942Late 1943 / early 1944
Blanket closures in effect 1 February 1945
p398, 412, 522
Listed for dismantling
Roddans Port (Roddansport)61ACHLMarch 1941 (under construction)Late 1941Late 1943 / early 1944
Blanket closures in effect 1 February 1945
p355, 365, 418, 522
Recommended for mothballing
Information compiled from Dobinson, Building Radar

Chain Home

By the time of the April 1941 air raids, Northern Ireland had 6 radar stations, presumed to be three pairs of Chain Home and Chain Home Low. As part of the expansion program following the devastating raids, an additional pair of CH/CHL stations appear to have been added, as well as the deployment of GCI stations. From records and aerial photography, I have located the eight CH/CHL stations located around the coast in NI. A number of the sites are in remarkable preserve, while some have very little remaining.

There are a couple of pieces of oral evidence recorded on that suggest there was a “Chain Home radar was operated by the Royal Air Force at Urcher Hill, Crossmaglen.” Another piece of submitted evidence to this website was that there was a “Royal Air Force Chain Home radar station off Lettergreen Road in the townland of Killyroo in Newtownbutler would provide early warning of any Enemy Aircraft approaching over neutral Eire. The Radar Station was commissioned in February 1942.” My understanding is that CH equipment was exclusively deployed by the coast for Early Warning, these two sites are almost exclusive the only two inland CH stations of the war.

Chain Home and Chain Home Low sites plotted in Northern Ireland. Note the dispersion along the coast and the pairing of CH and CHL sites.
NameSite DesignationSite TypeIrish Grid Reference
RAF CastlerockAMES 59CHC 795 344
RAF DownhillAMES 59ACHLC 740 354
RAF BlackheadAMES 61BCHLJ 486 935
RAF GlenarmAMES 60ACHLD 333 133
RAF GreystoneAMES 61CH (associated with CHL at Roddens Port)J 618 719
RAF Roddens PortAMES 61ACHL (associated with CH at Greystone)J 637 656
RAF KilkeelAMES 78CH (associated with CHL at Ballymartin)J 328 147
RAF BallymartinAMES 78ACHL (associated with CH at Kilkeel)J 343 170
RAF CrossmaglenUnknownCHH 919 154
RAF NewtonbutlerUnknownCHH 412 289 (estimated)
Chain Home (CH) Radar sites in Northern Ireland. The number 59/60/61 and 78 suggest that the stations at Kilkeel and Ballymartin were added later in the war.

RAF Castlerock AMES 59

Designated CH59, Castlerock is the original CH station in NI. It was operational by the end of 1940 (Dobinson) and was upgraded to Final equipment in May 1942. It is also in a remarkable state of preservation. The site also operated post-war as a readiness CH station for the newly formed UK Western Sector, with a Sector Operations Centre (SOC) based out of Longley Lane in England. With the development of the ROTOR system, it is thought Castlerock would have become defunct in the 1950s.

The remaining ground buildings and aerial bases at Castlerock CH59.

Scouring the online archives for images, I came across the image below in the Britain from Above collection. Taken in 1952, from some distance away, the aircraft has captured a faint glimpse of what are probably the wooden receiver masts. At this stage, they would have been standing for over 10 years, and may still be operational.

A rare, but faint, image capturing the radar antenna at Castlerock in the distance (far right on the image). Britain from Above XAW045263 taken in 1952

What remains today are the three main operational buildings on site; the transformer building for taking power from the national grid, the large transmitter building and a smaller, possibly receiver building.

An oblique aerial photograph from the RAF dated 14 August 1942 of the Castlerock RX (receiver) site. The accommodation camp can be seen to the left of the image, and the protected equipment buildings on the right. Image kindly supplied by Ian Brown © RAF Museum

RAF Downhill AMES 59A

Downhill, site 59A, was first surveyed in September 1940, with construction of the Chain Home Low station taking place in November of that year. The first site was on the south side of the road, for which a plan exists and has been reproduced below. The main exemption from this plan is the aerials, which would have been erected in adjoining fields. Of this early site, the receiver and transmitter hut blast walls still remain as does the guard room.

1941 plans of the original wartime radar site. This was located on the south side of Bishops Road.

On the north side of the road is the second phase of construction. This took place when Downhill received an upgrade to a Type 1941 CHL station. Here remains a single transmitter/receiver (TX/RX) block along with four plinths on which the legs of the steel gantry stood, with a mechanically rotated aerial known as a “Yagi-equipped single-drive array” mounted on top (Dobinson).

Downhill CHL 59A old site to the south and the new Type 1941 site to the north of Bishops Road.

As was the practice, an upgrade to a station saw the construction of a new set of equipment nearby, as opposed to retaining the old. This may have been to maintain continuity during construction, and also it would most likely have been quicker and cheaper to build from new rather than strip out and modify structures that were often intentionally difficult to access.

RAF Blackhead AMES 61B

Situated behind the lighthouse at Blackhead, the surface buildings appear to remain in good condition. Originally operated by the army as a Coastal Defence (CD) radar, it was handed over to the RAF in May 1942 for integration into the air defence network (Dobinson).

As a combined CD/CHL station, the radar here was ideally situated to plot both surface shipping and low flying aircraft approaching the entrance to Belfast Lough, and may have been staffed by both Army and RAF personnel, but at this stage little more information is known.

Remains of the two surface buildings at Blackhead CD/CHL station (September 2020)
Remains of the two surface buildings at RAF Blackhead CH station © Google Earth

RAF Glenarm AMES 60A

An east-coast design of CH station that had been constructed sometime between the start of the war and July 1940. This CHL station is associated with the CH station at Blackhead. No further information is known.

Image 11: The two surface buildings at RAF Glenarm CHL station.

RAF Greystone AMES 61

The Chain Home radar site at Greystone on the Arcs Peninsula. Both the service accommodation and transmitter building remain in good condition. Plans approved in January 1941, and the staton was listed as under construction in April 1942 (Dobinson). No further information is known.

RAF Roddens Port AMES 61A

The CHL radar station for Greysteel, the appears to remain a single building on top of a hill. Operational in September 1942 (Dobinson). No further information is known.

Image 12: The single building remaining at Roddens Port that may be associated with the Chain Home Low station here. It is co-located with a 1960’s Royal Observer Corps nuclear observation post.
Image 13: Possibly the only remains of Roddens Port CHL site on small hilltop overlooking the coast. This building was probably a generator house given the ventilation louvres under the roof and the large doorway.

RAF Kilkeel AMES 78

Once again the Britain from Above image archive has provided a glimpse of one of the illusive radar stations around the coast of Northern Ireland. From this low level aerial image, we can identify one of the wooden receiver masts in the right of the image, and two of the steel transmitter aerials to the left of the image.

A few of the buildings remain today, including the transmitter house and some of the raised aerial anchors that have been incorporated into a field boundary.

Image 14: Britain From Above XAW052117 Kilkeel Radar, taken in 1953

RAF Ballymartin AMES 78A

A single building remains of the Chain Home Low station at Ballymartin. I have no images of this site other than a Google Street View glimpse of the remaining red brick building in a field. This appears to be the same design as one located at the nearby CH station at Kilkeel. Operational in September 1942 (Dobinson).

Image 15: A Google Street View image of the sole remaining building of the CHL station at Ballymartin.

RAF Crossmaglen

Working from a second hand testimony on another website, a station described as a mobile Chain Home system was located on Urcher Hill, north of Crossmaglen. I first hypothesised this may have been a GCI site, but after publishing this article I managed to procure a copy of Colin Dobinsons Building Radar book, that interestingly lists Crossmaglen, along with Newton Butler as CH stations in April 1942. Not strictly CH stations as we would recognise, they were Mobile Radio Units (MRU) commissioned in February 1942. Crossmaglen and Newtownbutler remained temporary and used mobile equipment (Dobinson).

Some more scouring of online archives led me to a possible site in the right location on Britain from Above aerial photography archive. It is possible that this small cluster of buildings, including a nissen hut. No further information is know, and nothing appears to exist in images of the site today.

An aerial photograph from the Britain from Above archive taken in 1952 (XAW044953) shows what may be the temporary remnants of the radar station referred to.

RAF Newtownbutler

I have not been able to pinpoint or confirm the location of the Newtowbutler CH station, but it is was most likely a Mobile Radio Unis (MRU) commissioned in February 1942 alongside Crossmaglen and remained a temporary station throughout the war. Based on testimony on another website, the site was probably located off the Lettergreen Road.

Ground Controlled Intercept

With the exception of one Type 7 permanent GCI site at Ballywoodan (at RAF Bishopscourt) all the remaining sites in NI seem to have been either mobile or intermediate installations; that is they were either mounted on the back of a vehicle, or they had temporary buildings. While the Ballywoodan site was in use in some form until the 1990s, the remainder present little or no remains. With such a temporary network, establishing dates and times when they became operational and were closed may be impossible to find.

Ballywoodan was also the only ‘final’ or permanent Type 7 site that Northern Ireland had. And it appears that as the air threat to the UK changed in 1944 and beyond, that the non-final or temporary GCI stations were slowly cut, leaving the finals in place (Dobinson). This is suggestive that by mid-1944, the only GCI site in NI was at Ballywoodan.

Map 2: Known Ground Control Intercept (GCI) sites plotted in Northern Ireland to show the even dispersion of the sites across the country. The reports from these sites would have fed directly into an anti-aircraft sector control to co-ordinate a response from fighter aircraft. The sites plotted with grey marks are the two unconfirmed locations at Urcher Hill and Killyroo.
NameSite DesignationSite TypeGrid Reference
Ballinderry27GGCIH 918 794 (estimated)
Ballydonaghy26G (duplicate designation perhaps suggesting the relocation of mobile equipment)GCIC 362 037
Ballywoodan29GGCIJ 576 430
Bishops Road26G (duplicate designation perhaps suggesting the relocation of mobile equipment)GCIC 724 334
Lisnaskea28GGCIH 344 344
Table 5: Radar sites, excluding anti-aircraft Gun Laying (GL) radar.

RAF Ballinderry

No visible remains and no further information is known. Possibly the site of a mobile GCI site.

RAF Ballydonaghy

There are two concrete bases visible in aerial images. Possibly indicating this was an intermediate site; the larger hardstanding on the left for the radar and the smaller base to the right as a crew shelter or control building. The site was operational from at least January 1943 (Dobinson).

Image 16: The remains at Ballydonaghy.

RAF Ballywoodan

The airfield at RAF Bishopscourt became operational on the 1 April 1943, and in the following month the Ground Controlled Intercept station (known as Ballywoodan GCI) became active ( Ballywoodan was the last of 21 operational GCI ‘final’ stations to be constructed and was operational by the summer of 1943 (Dobinson).

The only fixed or ‘final’ GCI site that Northern Ireland seems to have was at Ballywoodan. An exact location doesn’t appear have been established before, but doing some digging I think I can now confirm. The town land of Ballywoodan is to the north of RAF Bishopscourt (Bishops Court). A later remote radar station was established at Killard Point to the east, but this would not have been referred to as Ballywoodan.

Map 3: The town land of Ballywoodan is to the north of the airfield at RAF Bishopscourt. The yellow dot marks the site of the happydrome building.

A recorded oral testimony on noted the presence of an early Type 7 (T7) Mk. I (Ground Controlled Intercept) radar ‘well’ on the airfield. This well was the subterranean control room for the large rotating radar that was mounted on top.

The T7 GCI radar site was the first form of GCI site that employed a single large building as the radar control, known as the Happidrome. While later incorporated into the ROTOR station at Bishopscourt, I believe this building was the original Happidrome control building for the T7 Mk. I GCI radar.

Image 17: The Happidrome building of the Type 7 GCI radar station at Ballywoodan.

Bishops Road

No visible evidence remains, and no further information is known. Possibly a location where a mobile site was located.

RAF Lisnaskea

Tenuously there are two concrete bases visible in aerial images at the end of a concrete track. Possibly indicating this was also an intermediate site; the hardstanding oat the end of the track for the radar and the smaller base to the left as a crew shelter or control building.

Image 18: Possible remains of concrete hardstandings at Lisnaskea for a mobile GCI station in this poor quality aerial image.


At this stage it is impossible to know what equipment was deployed to HAA sites across NI, or indeed if any was. There are still a number of sites that have intact radar platforms; a brick and concrete ramp leading to a raised platform on which a mobile wheeled radar trailer would be parked and operate from. These may have been constructed as a routine measure, or perhaps indeed the equipment was available. At night, the most likely time for enemy aircraft to attack, an HAA battery would be blind without the use of either searchlights or radar. There does not appear to be sufficient searchlight coverage, in particular in the north of the country to give light to the multiple anti-aircraft (both light and heavy) batteries. For those sites that have been destroyed, it is not possible to ascertain wether they also had radar platforms, although later examination of the post-war aerial photographs will answer this question.

Post-war, Heavy Anti-Aircraft defences in Northern Ireland were split into two gun-defended areas (GDA) under Army control, both part of the new 3 Group. The Belfast GDA had the Anti-Aircraft Operations Room (AAOR) in Lisburn (Thiepval Barracks) manned by 51 Brigade, while the AAOR for Londonderry GDA was started at Campsie but construction stopped before it was finished.

NameSite DesignationSite TypeGrid Reference
Culmore Unknown3.7″ HAAC 473 237
GroartyUnknown3.7″ HAAC 396 187
Island MageeUnknown3.7″ HAAD 444 027
MagilliganUnknown3.7″ HAAC 664 372
MalluskUnknown3.7″ HAAJ 295 818
Table 6: Heavy gun sites that are known to have included a radar ramp.

Island Magee HAA Battery

A good example of a self-contained HAA site, Island Magee has a compliment of 4 gun pits for the 3.7″ heavy guns, as well as an ammunition magazine and radar platform. At the bottom of the field are remains of the barrack buildings for the admin of the site and to accommodate the soldiers manning the guns.

Image 19: The site at Island Magee.
Image 20: The radar platform at Island Magee.

Magilligan HAA Battery

This must be one of the best preserved HAA sites in Northern Ireland. Still standing, and in good condition, is the radar ramp for the Gun Laying (GL) radar. There is also a second platform that may have been added later for a new radar trailer that did not need to be raised on a platform.

Image 21: The site at Magilligan is remarkably well preserved.

Mallusk HAA

The site at Mallusk, on the eastern shores of Belfast Lough, was one of the HAA batteries defending the naval port and city of Belfast. It is likely that the gun emplacements were at the top of the image where the housing development is being prepared. In an urban area such as Belfast this is an enduring problem; the expansion of residential or industrial areas forces the removal of sites like this.

Image 22: Due to expanding housing developments, in 2010 only the radar platform and magazine remained, however the radar platform was demolished soon after the aerial images were taken.


At the end of the Second World War there were an estimated 170 permanent radar sites across the UK, but most of this equipment was now old and out of date; the Chain Home system being designed in 1935. The threat was also evolving, and by 1949 the Russians conducted their first nuclear tests and were equipped with long range nuclear capable bombers. It was only a matter of time before they would become a feasible threat. The country needed a new Early Warning (EW) system, and project ROTOR was born.

At huge expense, the country manufactured new radar systems, and set about consolidating the existing radar network to 66. Initially three sites were chosen in NI, Castlerock CH station on the north coast, Killard Point which is near to Ballywoodan GCI site, and in the mid-1950s a new site at Murlough Bay on the north east coast was constructed. By the 1960s all but Killard Point remained operational, and it did so until the 1990s as a civil air traffic control radar station.

As with Chain Home sites, there were loosely two designs of site reflecting the perceived risk of attack and capabilities of the attackers; east coast sites with huge buried and reinforced bunkers, and west coast sites with above ground buildings. All Northern Irish radar sites were of the latter, above ground type.

NameSite DesignationSite TypeGrid Reference
CastlerockUnknownROTORC 795 344
Killard PointUnknownROTORJ 607 433
Murlough BayURBROTORD 213 406
Table 7: Radar sites in NI that are known to have been kept on post-war and included in the ROTOR scheme.

RAF Ballywoodan (Killard Point)

The difference in name I think relates to the new aerial site at Killard Point but the remaining control at Ballywoodan on the site of the wartime GCI radar site.

Two new GCI stations were also proposed as part of the Rotor 3 programme, each equipped with a Type 80 radar and R8 ops block. One at Ballywooden (Killard Point) in Northern Ireland and the other at Wick on the Scottish east coast. It was hoped that The ROTOR 3 programme would be complete by 1957 and all technical aspects were classified as ‘Super Priority’. Until they were completed arrangements were made to use mobile equipment in an emergency.

Much more information is available for the ROTOR network, and we know what radar equipment was stationed at Killard Point and Bishopscourt (Subbrit).

  • Type 84 surveillance radar (RAF Bishopscourt)
  • Type 80 early earning & fighter control radar (Killard Point)
  • Type 93 (Mobile) early earning & fighter control radar (RAF Bishopscourt)

RAF Murlough Bay

There were three sites used post-war as part of the ROTOR project to enhance British air defences against the new Russian nuclear bomber threat. Out of the three, Murlough Bay was chosen as a new build. Completed in 1956 the site was closed in 1958, no accommodation was provided on site and personnel stayed locally. The above ground site must have been bleak in the winter months, but the demise was most likely due to technological advances and that operations between Killard Point and Scottish radar sites could cover the same air space.

We also know what radar systems were deployed at Murlough Bay (Subbrit):

  • Type 14 Mk. IX search radar
  • Type 13 Mk. VII height finder

A VHF transmitter and receiver pair were also constructed near to the main technical site, each with a 90 foot tower. No remains of these remain.

The site is now a Grade B1 listed due to “the surviving fabric is historically authentic and it reflects a brief but significant period in the UK’s military history known as the Cold War and is of national significance in this respect in terms of its defences. Cold War radar sites are extremely rare in N. Ireland, this being one of only three; the others are at Castlerock and Killard Point.


Radar was a secret technology until 1942 when it was announced to the public, and the technical detail remained so for many years after the end of the war. While primitive compared to German technology of the same era, the British use of a network incorporating many elements, of which radar was one, was to prove a strength. Of the many studies that have been done into the Chain Home network, they almost all exclude Northern Ireland. Without covering too much ground again, I think there are some conclusions we can draw from this research:

  • Early in the war Northern Ireland was identified as being critical to the war machine; large naval ports at Belfast, Larne and Londonderry, as well as well established heavy industries such as aircraft and ship manufacture. A modest air defence network existed at this stage, including 6 radar stations; a mixture of three CH and three CHL. Chain Home provided early warning out to sea and were large permanent stations of which large portions still remain.
  • NI was probably deemed a low risk target, being ‘out of reach.’ This was proved wrong during the air raids of easter and spring 1941. Following these, there was an almost doubling of the air defences in the country. By this time the threat had passed and NI would not see attacks on that level again. It was at this stage when GCI stations were introduced, mostly mobile. GCI provided coverage of the inland air space and were mostly mobile or temporary stations of which little or no evidence remains.
  • The arrival of the Americans in 1941 would see an increase in the defences around the port of Londonderry and the newly constructed port at Lisahally. This led to an increase in anti-aircraft guns and a possible expansion of north coast radar capabilities. Heavy anti-aircraft batteries were equipped with radar platforms, but from this alone we can not establish the nature or capability of the equipment.
  • Little or no photographic evidence remains of NI radar sites in the public domain.
  • Two wartime sites continued in operation after the war (Castlerock and Ballywoodan) while new stations were constructed at Murlough Bay and Killard Point during the latter phases of project ROTOR. Only one site was to endure and that was Killard Point.

It would be great to see a comprehensive study completed to record and document the state of NI air defences during the 1939 – 1945 period as this does not appear to have been done before. When I get the opportunity, I will visit the archives at PRONI and the National Archives to see what documentary evidence remains.



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