The Moel-y-Parc transmitting station is situated on Moel y Parc, a hill in north-east Wales at the northern end of the Clwydian range, close to the town of Caerwys and several kilometres north-east of Denbigh. It was built in 1962/1963 by the IBA to bring 405-lineVHFITV television to North Wales and it has been on the air since 1963. Its original height of 229 m made it the tallest structure in North Wales and it stands on land that is itself about 335 m above sea level. In 1965, VHF television transmissions from the BBC commenced from the site.
VHF television services from both BBC and ITV were discontinued in January 1985 as the 405-line TV system was switched off across the UK as a whole.
Moel-y-Parc's UHF channel allocation made it a "Group B" transmitter, but with the roll-out of the UK's first digital TV services in 1998, a "Group W" wideband aerial was needed. The site reverted to being a "Group B" transmitter at digital switchover (DSO).
Until the mid-1960s, it had been common practice for BBC and ITV transmitters to be hosted from different masts. Moel-y-Parc had been engineered to take both services and be capable of the UHF transmission when they arrived. Additionally (and unusually) the BBC's VHF television transmissions were on Band III as were the ITV's transmissions. Having both services on the same mast meant that the region's viewers only needed one aerial.
This was the final BBC VHF television "main station" to be commissioned. The BBC published a technical report on the mast and its aerials.
As part of the digital switchover, analogue BBC Two Wales ceased transmission on 28 October 2009, followed by analogue BBC One Wales, ITV1 Wales and S4C on 25 November 2009. They were replaced by higher powered digital transmissions.
As a side-effect of frequency-changes elsewhere in the region to do with clearance of the 800 MHz band for 4G mobile phone use, Moel-y-Parc's "Digital 3&4" multiplex was moved from channel 49+ to channel 39+.
In terms of land area and population, Moel-y-Parc delivers a receivable signal to a greater area, and a greater number of potential viewers, in North West England than in its intended coverage area of north-east Wales. Transmissions can be received using standard aerials in Liverpool, parts of Manchester, parts of Lancashire as far north as Blackpool, and Wales-facing coastal areas of Cumbria and the Isle of Man. In the past, some English viewers have erected a second aerial for Moel-y-Parc in order to receive a slightly increased choice of viewing, although this practice has declined with the introduction of satellite television and the reduction in schedule variations between different ITV regions. Liverpool is located directly between the Winter Hill transmitter and Moel-y-Parc, and many Liverpudlians obtain a watch-able picture through the back of their normal TV aerial.
The Welsh stations transmitted from Moel-y-Parc compete with English TV stations transmitted from the Winter Hill, which can be received in the Wrexham area and along the North Wales coast.
Prior to 1963, the only official ITV provider for north-east Wales was Granada Television based in Manchester. Pressure for a distinctly Welsh TV station was one of the driving forces behind the construction of the Moel-y-Parc mast, along with the need to deliver television to the more mountainous interior of Wales, which was out of range of English transmitters. As late as the 1980s, Granada continued to claim north Wales as part of its coverage area. After a series of mergers, Granada and ITV1 Wales are now both part of ITV plc, and competition between the two providers is undoubtedly more muted, however both Granada and ITV1 Wales still provide local news and programmes for those in North Wales. The ITV Regions Official Map distinctly shows the area of North Wales as part of Granada, however for many across North and Mid Wales, it is possible to receive Central (West) via The Wrekin Transmitter. Unlike Granada, these areas are not shown as part of Central's coverage area on the ITV Regions map, and neither are they included as part of the region in Central's weather forecasts .
Moel-y-Parc has always had co-channel interference issues with a number of other co-receivable transmitters such as Llanddona, Storeton, Fenton, Sutton Coldfield and The Wrekin B (see external links). In analogue, Greater Manchester area was also able to receive Welsh channels because the Saddleworth transmitter, a relay of Winter Hill, used the same frequencies as Moel-y-Parc.
By December 2009, more than 6,000 complaints over interference from Moel-y-Parc had been received following the changeover to digital in the Granada TV region Many residents in Wirral and west Cheshire only found Welsh channels including BBC Wales and S4C at the top of their channel listings (instead of BBC North West and Channel 4). Digital UK, the organisation responsible for the switchover, said interference had always occurred and responded by telling consumers to retune their systems manually.