History
Also known as Harraby, the SHF site at Carlisle developed adjacent to an existing exchange and repeater station on cables from Manchester to Scotland. The first radio installation appears to have been for Tyne Tees Television in 1958 (on air January 1959). The ITV "network" feed arrived at Carlisle via cable from Manchester and was sent by SHF link to Newcastle via Hopealone and Pontop Pike. At this stage a 175 ft tower was provided and the equipment was in a timber building pending construction work. In 1959 a link to Belfast (Ballygomartin) was added for Ulster Television (on air October 1959). This ran via Riddingshill and, as with the Tyne Tees link, was one-way initially. Provision was also made for telephony over the same route, added in the early 1960s.
The BBC television transmitter at Sandale (1956) was fed initially from a temporary site at Slippy Stones and later via Hopealone. The Northern Ireland service had an independent arrangement, therefore Carlisle was not involved with BBC programme feeds at this stage. Border Television established studios nearby with a tramsmitter at Caldbeck (on air September 1961). It is possible an SHF link was provided initialy but network diagrams from the 1970s show Caldbeck connected via cable. Around the same time Grampian Television started broadcasts to the north of Scotland, the "network" feed running via cable to Glasgow, along with that previously provided for STV (1957). By the early 1960s Carlisle was thus a significant place within the Post Office vision network serving ITV.
The BBC link from Hopealone was subsequently diverted via the Television Network Switching Centre (TV NSC) at Carlisle with the Sandale transmitter probably fed via cable. The SHF site, however, expanded significantly as further vision circuits were required for ITV towards Scotland and for BBC2 distribution. An initial step was the installation of a "small" horn antenna in 1961 - allowing the use of the 6 GHz band towards Scotland - but in 1967 the tower was replaced, with "large" horns facing Riddingshill and Two Top Hill. (A temporary SHF link from Manchester to Kirk o'Shotts is understood to have been in operation by around 1963.)
Documents in the CPRE archive suggest a concrete tower was considered for Carlisle but in the event an unusual project was attempted - a "Standard Tower" would be built over the existing structure. It is unclear how service was maintained once the new steelwork started to obstruct the antennas underneath but eventually the transition was completed and the old tower dismantled. One element did not go to plan: waveguides for some of the planned horn antennas were obstructed by parts of the tower! This led to the use of dishes (which do not require straight, vertical, waveguide) at the upper level. The "new" tower appears to have carried antennas facing Riddingshill, Hopealone and Two Top Hill only for the first few years.
Due to the original choice of routing, traffic to Belfast and Scotland was constrained by the shared link to Riddingshill. In the 1970s this bottleneck was removed by adding a new site at Wharrels Hill and diverting the Belfast route. This initially seems geographically "wrong" but it had been the practice to allow approximately 90 degrees separation between main routes and therefore a site south west from Carlisle was needed. This new route to Belfast was probably in service by 1975. A minor link was added around the same time - to the BBC Sandale transmitter but for stereo FM rather than television. For BBC televsion remote switching was provided at the TV NSC (controlled from Manchester) - this was later used to allow a small studio in Carlisle to broadcast local new via the Caldbeck transmitter.
In the 1980s the main telephony links were migrated to 11 GHz digtal systems but we understand the television distribution to Belfast remained analogue (except for Channel 4). By 2009 most of the large dishes had been removed, except those facing Riddingshill, which remained until late 2011.
