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Downhill Radio Navigation Site

The use of radio technology transformed the air war during the Second World War. In a short space of time RADAR was born and fine tuned to detect and track approaching enemy aircraft, radio direct finding (RDF) was used to detect illicit communications, ships and submarines as well as tracking our own aircraft, but the same technology was used to aid navigation of bomber aircraft. This early radio navigation system was called Gee (sometimes written GEE) and for a brief period in 1945 the north coast of Northern Ireland was home to a Gee station.

The use of pulsed radio signals called GEE (Ground Electronic Equipment) was first proposed by Britain’s R. J. Dippy in 1937. His original intent was to use GEE as a homing device to help bomber crews return safely to their base under foul weather conditions.


The Gee chain (a series of Gee transmitters working to form an independent network) was primarily operational over the United Kingdom, and in the early days the system was prone to interference from enemy transmitters so was seen to be unreliable over France and Germany. However, as the allies pushed into Europe, and the source of the interference was removed, mobile stations were established in mainland Europe to help the allied push inland.

The first Gee chain went operational in March 1942 after a period of testing. With an initial focus on the south and east of England, chains were soon deployed across the UK, with a total of eight chains planned, and seven deployed in the United Kingdom by 1945. Down Hill (sic Downhill) was one of three deployed stations in the North Western chain, operational for 6 months in 1945. It was designated “North Western Chain, B Slave Station, AMES 74211” and operated AMES Type 7000 equipment.

‘GEE’ RADAR STATIONS (CH 16519) Original wartime caption: For introduction see CH.16518 A heavy mobile ‘Gee’ station at Euskirchen, near Cologne, photographed from the air during the closing stages of the war in Germany. Copyright: © IWM. Original Source:

United Kingdom GEE Network

ChainMasterSlavesChain MonitorOperational Dates
EasternDaventryClee Hill
Ventor then Gibbet Hill
RAF Great Bromley then BarkwayMarch 1942
SouthernBulbarrow HillTruleigh Hill
West Prawle
South EasternTruleigh HillCanewdon
NorthernBurifa HillScousburgh
Windyhead Hill
Burifa HillLate 1942 – March 1946
South WesternSharpitorWorth Matravers
North EasternRichmond (Yorkshire)High Whittle
18 April 1944
North WesternSaligo BayDown Hill (sic Downhill)
1945 (6 months only)
United Kingdom Second World War Gee network, Wikipedia

The late implementation of a North Western chain highlighted the importance then placed on covering the north-western approaches; the name given to the area of Atlantic Ocean that sits to the west of Ireland and Great Britain that was both vital to the Atlantic convoys from America carrying troops and cargo, but that were also vulnerable to the U-boat “Wolf Packs” and airborne incursion around the top of the Scottish islands. Initially four sites were planned in the winter of 1944/45; Mull, Saligo Bay, Barra and Downhill, with Barra being scrapped by the time of construction later in 1945.

For complete coverage across the Atlantic, a station would be ideally located as far north and west as could be possible on the island of Ireland, but given Irelands neutrality during the 1939 – 1945 “emergency” this was not politically possible, and Downhill was the highest and most north-westerly point within the United Kingdom on which a site could be constructed.

The site at Downhill was less than ideal. In the National Archives of Ireland files, reports that “the damping of signals by the Donegal Mountains” impeded the operation of the post. This issue was investigated in Guarding Neutral Ireland (Michael Kennedy, 2008) who discovered that requests were made by the Air Ministry to site a radar station at Malin Head; the most northernly point on the island of Ireland. What the research uncovered was discussions as early as 1941 to site a chain of radar stations in Ireland, but the Irish governments insistence that they were to be manned by Irish personnel was not found to be acceptable to the British authorities. Not only was there a clear threat from German forces targeting any potential site, but the IRA were likely to attack the station and murder any British personnel found to be working there.After lengthy and detail discussions about how to install a clandestine Gee transmitter on Malin Head, using the existing Napoleonic tower, plain clothes RAF personnel and repainted RAF vehicles, it was conceded that the Site at Downhill would probably be adequate. It was planned to conduct operational tests at Downhill at the start of 1945, but as the war drew to a close the need for the station was diminished and the North Western was drawn down in spring of the same year.

Locating the Site

Downhill is a small seaside village on the north coast of County Londonderry, to the west of the mouth to the River Bann. This is very low lying ground, and unsuitable for a transmitter station. Downhill was however, home to a Chain Home Low radar station, operational from September 1940 until the end of the war. This station was located on the high hilltop above the beach, in the townland of Burren Beg (map below).

While I have not come across an exact location for the Downhill Gee transmitter, I believe this site, where the modern day viewpoint and picnic area is was home to the navigation beacon. OSNI 1:50000

During this research I considered the possibility that the Gee station was co-located with the CHL radar station, as was sometimes the case in England. Existing sites were ideal, having all the necessary infrastructure such as accommodation and power; however the radar station sits lower in the landscape and the presence of an unidentified radar station on the prominent high ground further west has led me to investigate this site.

The Defence Heritage Project is run by Queen’s University in Belfast and has a tenuous Radio / Radar station recorded as being located at Downhill.

The site I believe to be the Gee station is not unknown. An entry was made as part of the Queen’s University Defence Heritage Project (DHP No. 5.00) that suggested a “Radio / Radar (?) station” at this site. It is clear that little further research had been done to establish the validity of the submission. I hope this article provides more information to confirm the operation as a Gee station.

Aerial photographs of the site appear to show the base of a building, and a number of anchor blocks that would be required to secure a mast.

The most recent aerial imagery from 2018 shows the building base, but other features are lost, covered in vegetation.
Google Earth street view of the Gee site at Downhill from August 2011 showing the concrete building base.
The Google Earth images from 2011 are low resolution, but the higher contrast appears to show three anchor blocks in the field adjacent to the building base.

Comparison: Mobile Sites

Another difficulty in identifying a site like this is establishing what equipment to expect. Often as technology developed, the requirements changed and so did the material buildings constructed. Added to this, is the combination of fixed and mobile technology, both of which had been deployed in support of Gee chains. It’s unclear as to what was deployed at Downhill, but the presence of some structures suggests the site was intended to be more than mobile. One image of a mobile Gee site from IWM deployed in mainland Europe shows a large steel lattice mast with associated vehicles parked tightly around the base.

ROYAL AIR FORCE RADAR, 1939-1945. (CH 16520) Low-level oblique aerial of a light mobile GEE station operating in a field near Roermond, Holland. Copyright: © IWM. Original Source

Comparison: Gibbert Hill Gee Station

Another station, this time a fixed slave site in the Eastern Chain at Gibbert Hill, and this is more akin to a Chain Home station; described as having four 240-foot masts and a large number of buildings can also be seen around the site. This was one of the first Gee chains to become operational in 1942 and was a result of experimental work by the Air Ministry. The use of Chain Home towers may have been as a result of modifying CH equipment at an existing site.

ROYAL AIR FORCE RADAR 1939-1945. (CH 16518) Aircraft Navigation and Guidance: Two of the four 240-foot masts of the GEE Ground Radar navigational air station at Gibbet Hill, Hindhead, Surrey. GEE was a navigational system which involved sending synchronised pulses to aircraft from three separate stations in Britain. From the difference in time of arrival of the three pulses, the aircraft’s navigator could determine his position. Copyright: © IWM. Original Source

Comparison: Truleigh Hill Gee Station

On the issue of integration with existing sites or new ones, Building Radar (Dobinson, 2010) informs us that these ground stations were either established at new sites, or existing chain stations “as geography required.” One example given was the Truleigh Hill site, part of the South Eastern chain, where a Gee ground station was constructed among earlier CHL buildings and remained as the site developed into a ROTOR station.

Comparison: Bulbarrow Hill Gee Station

Many of the Gee stations appear to have been demolished or have been complicated by the development of sites, but the Master station at Bulbarrow Hill may be as close to an original station as we can find. There is a large concrete pad for the transmitter or operational building surrounded by blast walls on three sides, along with what can be assumed to be a generator or transformer house, and four concrete pads as foundations for a single large mast.

The blast walls surrounding a concrete pad for the transmitter or operational building. © Mike Searle, licensed for reuse under the Creative Commons licence.



The first possibility is that the Gee station at Downhill was integrated with the existing CHL radar station. While this is possible, there is no evidence of an additional mast having been located here other than the CHL gantry. In addition, the operation and range of the CHL system is such that the cliffs around the coast of Donegal would have not proved a problem, even to the fact that the CHL radar location on slightly lower ground and further east would have been a benefit for coverage around the coast.

With a maximum operational range of around 350 miles, the Gee system would have required placement as high as possible, without physical interruption. The large cliffs and headlands of Donegal are reported to have caused problems with accuracy (most likely due to attenuation and reflection of the radio waves) at long ranges across the Atlantic. Placing the Gee station on higher ground than the CHL station would have been preferred, and we know this was often done.

However, digital comparison and measurement between the transmitter or operational building footprint at Bulbarrow Hill and with the concrete pad at the viewpoint at Downhill suggest they are similar dimensions; 16m long and 5m wide. While the mast foundations are different at both sites, a guyed mobile mast fixed more permanently would offer the same performance at lower cost and effort than a tower mast.

I will continue to research this subject and visit the site at the next opportunity to explore further and put some of the theories to the test.

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