History
The BBC television transmitter at Rosemarkie entered service in August 1957. Tests by the BBC in 1956 suggested direct reception of the Meldrum transmitter (at Core Hill) would be possible however a subsequent BBC Research report states: "The television and VHF sound transmissions from Meldrum are received at Fochabers [Tor Sliasg?] and fed by GPO microwave link to Rosemarkie". By 1966 a full SHF link seems to have been in place between Granite Hill and Rosemarkie where the Post Office established a separate building with a tower of a similar style to those at Tor Sliasg. Presumably the intention was for the site to provide connectivity beyond that needed for the television transmitter although this may not have developed as envisaged. This 1966 link is assumed to have carried BBC and ITV programme feeds.
Information from BT Archives suggests the ITA transmitter at Mounteagle was fed via cable from Rosemarkie however this (or more likely the SHF link from Granite Hill) was not available for the launch of Grampian Television in September 1961. The ITA was authorised to operate a temporary link at Pikey Hill (to the South of Elgin) with off-air reception of Durris and SHF link to Mounteagle.
Post Office Specification W 6888 (January 1968) covers the requirement for a new link to 625-line colour standards for BBC2, with a completion date of April 1970. BBC2 transmissions commenced on 11 July 1970 but UHF BBC1 and ITV did not enter service until 1973 - possibly due to delays in providing additional links to the new standard. W 6888 confirms the original routing from Aberdeen was via Core Hill and Tor Sliasg - both intermediate sites noted as "non-demodulating repeater stations". The new link was to be either on 2 GHz or the Upper 6 GHz band and new paraboloid dishes were to be provided throughout. It is assumed from archive photos of Tor Sliasg that the 405-line links used horn antennas (most likely at either 4 GHz or Lower 6 GHz). The "new" link was specified as unidirectional with one working and one standby channel, and capable of carrying 960 telephony circuits if required. A final detail was the requirement for the link to be controlled from "Inverness Telephone Repeater Station" (likely to be co-sited with the main exchange) via a 4-wire circuit to Rosemarkie.
Rosemarkie was the end-point of the PO/BT network provision to BBC and ITA/IBA. Other transmitters serving the north and west of Scotland and the Islands were linked either off-air or via "self-provided" links designed and installed by the broadcasters. (The PO/BT and BBC/IBA links, however, converged in a joint venture at Fair Isle.) The reason for the apparent change of policy by the Post Office presumably reflects the high capital cost and the low likelihood that the links might be used subsequently for telephony purposes. In general where the BBC or IBA had been permitted to provide their own links it was on the basis that the Post Office might later "adopt" them for other purposes.
It is unclear whether any link to nearby Daviot was ever established - the latter seems to have been established in the mid-1970s as part of expanded telephony links which appear to have bypassed Rosemarkie and run via Portmahomack. However an additional one-way vision circuit was provided in 1981 for Grampian Television, with SHF link from Inverness exchange to Rosemarkie, assumed to continue via Tor Sliasg to Aberdeen.
Current Ofcom data suggests there is a 6 GHz link between Inverness and Rosemarkie plus two local 18 GHz links. The adjacent broadcast mast carries numerous SHF links for Arqiva and others, with the BT site seemingly little used.