Mystery and intrigue surround local stories of the WWII code-breaking activities of the Gilnahirk Y radio station in Northern Ireland.
Originally established by the Royal Corps of Signals and the General Post Office’s (GPO) radio department, Gilnahirk Y served as one of three radio stations located around the United Kingdom that worked to intercept enemy wireless communications during the war. The station was set up in the unassuming farmland of Castlereagh Hills in Northern Ireland, directly overlooking Belfast. During WWII, the station operated 24 hours a day, seven days a week, every day of the year.
With the same level of importance as today’s internet, radio signals during WWII served as a primary method for military units and government officials to communicate. The GPO worked as the gatekeeper for this technology and was responsible for policing the airwaves under an act from Parliament. When active, Gilnahirk had the capability not only to listen in on all radio transmissions, but also the ability to triangulate with other stations to pinpoint the exact location of those transmissions.
At the time, the government believed Germany and its allies were sending secret agents to the UK to glean information on wartime planning. Gilnahirk Y and similar stations were a first line of defense against this threat. Due to a military shortage of trained radio operators, the government secretly recruited the aid of civilian Hams to listen in on enemy frequencies and report on the top secret information obtained.
These civilian responders were known as the Radio Security Service, or RSS. Under patriotic duty and terms of strict secrecy, RSS members recorded the date, time, frequency, and message of every radio transmission using high-tech radio equipment—much of which was buried underground.
The Belfast Electric Company supplied Gilnahirk Y’s onsite transformer, burying the main cable underground to avoid interference to the radio signal along with a high-grade telephone cable that enabled a broader communication network. In an article written by the BBC, former RSS member Bob King recounts the site’s setup.
The site consisted of a few wooden and nissan huts which were surrounded by a considerable number of very tall telegraph poles dotted about the adjoining fields. These poles were linked together with overhead wire and formed the aerial network which was used to intercept the radio traffic of the time. The wooden huts served a number of roles, but one hut would have contained the main radio room. This consisted of eighteen banks of American HRO radio receivers. These receivers were the Rolls Royce of their day and no signal escaped the fine tuning of an HRO receiver. During the establishment of this station, a Top Secret Marconi-Adcock Direction finding facility was placed into an all metal tank and then the whole thing was buried just below the ground some distance from the main collection of wooden huts. Four thirty foot high telegraph poles were placed, one at each corner of this underground structure.
As the most unusual structure of the setup, the Adcock Direction Finding Equipment consisted of a metal tank buried just below ground level with multiple large directional radio antennas securely attached. The facility was manned by a solitary Ham, and was capable of pinpointing the direction of any wireless broadcast within minutes of accessing the frequency. With the assistance of other UK radio stations, the exact location of the message’s origin could be determined for military benefit. This proved helpful in preventing run-ins with enemy ships, understanding enemy strategies, and protecting civilian lives.
While Gilnahirk Y survived WWII unscathed, the secret location of the Adcock Direction Finding Equipment is still a mystery, with those sworn to protect the site and its equipment committed to secrecy. Attempts to find it have proved hapless. However, you can still see photos of the Gilnahirk Y radio station, years after the war, on Frontline Ulster, a website dedicated to preserving military history.
Or contact GB0GLS on Saturday, May 2, when the special event station commemorates the work of the RSS for its fourth year running. The station will operate on 80/40/20 and possibly 17 meters, depending on conditions, and use SSB and CW modes. GB0GLS will operate between 10:00 and 18:00 hours. QSL cards will be available.
