History

The Manchester - Carlisle route formed part of 1959 plans but was mapped as "Sites not yet determined". From Manchester the route was shown via Winter Hill, Garstang, "Gargill" and "Rockcroft". It has not been possible to identify the last two sites. In practice Winter Hill was used, but known by the Post Offfice as Horwich, the next site was moved slightly north west to Heysham and sites were established at Whinfell Common and Two Top Hill - avoiding the National Park but within the wider Lake District. The terrain may have been a factor in the slow completion of this section.

Contract 23549 was awarded to GEC in August 1963. At a value of £430,000 this was one of the most expensive sections of the 1960s network. It's unclear why the cost was significantly higher than other systems with similar numbers of "hops" - the towers and buildings were not normally included so it may be the system was to include a large number of channels from the outset. Carlisle became the point where television and telephony circuits diverged towards Scotland (Kirk o'Shotts) and Belfast, with further links to Pontop Pike. (Other routes tended to start with minimum provision, with further contracts for expansion.) This was a non-competitive award: "On grounds of urgency [GEC] is the only one able to meet the 'required by' date". The L6 GHz system was required to be completed by 1 April 1965. Contract 300506 was awarded in March 1966 for additional channels at a cost of just £35,000, for completion by 1 April 1967. This was a non-competitive contract on the basis the equipment formed part of the system already being provided. By April 1966 the main contract price had risen to £533,138.

The original structures along this section were something of a mixture: Heaton Park would be a relatively short concrete tower, Horwich received a large pyramid-shaped structure and Heysham a relatively short "standard tower". At Whinfell Common a low gantry was sufficient, with a variant of the "standard tower" at Two Top Hill. The elevated ground level at these sites meant tall structures were neither required nor desirable. At Carlisle a new "standard tower" was constructed to give additional capacity. All sites were provided with the standard microwave station building, other than Carlisle where the radio equipment was installed on the upper floor of the repeater station at Harraby. All structures were designed to support pairs of horn antennas, the intention being to allow operation on 4 and 6 GHz bands.

Photos dated October 1967 show two dishes at Two Top Hill, with the horns installed by January 1968; a similar situation is shown at Heysham. Other October 1967 photos show Pye 7 GHz transportable equipment at Carlisle and Whinfell Common - it seems the route operated initially on a temporary basis. Most likely this was to provide links for BBC2 which was avaialble from Black Hill (adjacent to Kirk o'Shotts) by July 1966 - this would have required a link to 625-line standards from Manchester via Carlisle. BBC1 and ITV at Black Hill were available from December 1969, which may reflect progress of work north and south of Carlisle.

Subsequent development appears to have included additional telephony links. By 1984 there were seven vision circuits northbound: two for BBC television, one for EBU ("Eurovision") to Belfast (continuing to Dublin), one for BBC FM radio, two for ITV and one for Channel 4. In the southbound direction: one for BBC "contribution" purposes and two for ITV (switched by BT to serve Border, Grampian, STV and UTV). Four pairs of "protection channels" were operational, suggesting all available bands were in use.

The 1980s migration to a digital trunk network led to the addition of 11 GHz systems, Heysham becoming a "flexibiliy point" and gaining a new route from Northern Ireland via the Isle of Man. As part of this (or during 1970s expansion) the towers at Heysham and Two Top Hill were increased in height. Whinfell Common now has a tower of 1980s design.