History
The location of Ballygomartin initially proved elusive and there seemed to be no modern photos of the site. This seems likely to have been largely due to the political situation in Northern Ireland for much of the time the site was operational. As a key site providing telephone and television links, the station was heavily guarded during The Troubles. Although virtually all traces of the site have been removed a NI Public Record Office file "Protection of Ballygomartin Radio Station" remains closed until 2039.
Ballygomartin was operational by 1939 as a Post Office VHF radio site, linking to Portpatrick (near Enoch Hill). The SHF station dates from 1959 and was initially used to provide an inbound "Network" feed for Ulster Televsion for the station's launch on 31 October. The link was also planned to carry 600 telephony circuits and a spare television link in each direction. (An early provision for BBC televison involved off-air reception at Ballygomartin, but other arrangements were used subsequently.)
As shown below, the initial arrangement used a relatively short tower carrying two dishes, facing Enoch Hill and operating at 4 GHz using STC equipment. By 1967 this had risen to four dishes - presumably a second band had been introduced to give additional capacity for 625-line television links (including the two BBC services) and telephony expansion. At this point the structure appeared more or less "full". All traffic passed to/from Belfast via cable. The nearby Standing Stones site was later used to provide SHF links in directions not feasible from Ballygomartin.
The inclusion of RAF Bishops Court (also known as Killard Point) in the Linesman/Mediator RADAR system required a link to West Drayton which Post Office archive documents suggest was to be operational by late 1968. A tall tower was used at Bishops Court - this does not seem to have been an "easy" path. The radar link may have been diverted subsequently but Bishops Court closed during the late 1980s and Ballygomartin reverted to a "single-ended" site.
During the 1970s Enoch Hill and intermediate sites to Carlisle received new structures and the number of dishes increased signifcantly as additional bands were brought into use. Ballygomartin received a second tower, of the standard "Type 5A", but the original was retained. In the 1980s a new digital link from Belfast was added, running via the Isle of Man. It seems the telephony links via Ballygomartin were subsequently upgraded to 11 GHz digital but most of the television links appear to have remained as anlogue until closure.
As elsewhere, changes in technology led to the decline of the SHF network. In Northern Ireland many sites were completely cleared. At Ballygomartin the decision to vacate and demolish the site may have been a combination of unsuitability for other purposes, environmental considerations and a desire to remove the more overt signs of past military/security measures. Geograph photos from May 2012 refer to the Ballygomartin site as a former Army/SIGINT base and show the remaining fence around the compound with the comment "buildings have recently been demolished". It is unclear whether Ballygomartin was actually a military facility, in the shadow of the SHF site, or simply an important site requiring protection.
Google Earth features an excellent image dated December 2001 showing a group of buildings and the two towers. It seems the original structure possibly carried only one large dish at this stage, with the "Type 5A" supporting perhaps four others. All dishes faced north west. By April 2007 both towers were empty but remained in place as of May 2009. The site clerance probably took place by the end of 2010.