The Arfon transmitting station is a facility for FM radio and television transmission near the villages of Nebo and Nasareth in Gwynedd, northwestern Wales (grid referenceSH476493). It includes a 308.5 m (1,012 ft) guyed mast with antennas attached at various heights. The mast is surmounted by a television transmitting antenna, which brings the total height of the structure to 317.4 m (1,041 ft), making it the tallest structure in Wales. It is owned and operated by Arqiva.
405-line TV was finally discontinued in the UK in 1985, but it appears that Arfon's VHF transmitters were decommissioned a year early in 1984 and the transmitters themselves were reused for clinical radiotherapy.
More recently, Police and Ambulance communications have been added, in addition to mobile (cellular) telephone antennas. In 1993, Classic FM began using the site for FM coverage of north west Wales in preference to Llanddona (the BBC's regional FM site), partly due to a dispute over BBC charges for sharing fees of its transmitter masts and antennas, but more because Arfon, in conjunction with Great Orme's Head (near Llandudno) gave Classic FM better coverage than the BBC sites.
On 16 November 1998, local commercial radio station Champion 103 launched from studios in Bangor with its transmitter at Arfon.
The primary television service area includes most of Anglesey and central parts of the Llŷn Peninsula, however many viewers in south Dublin and north County Wicklow can also receive Arfon's broadcasts. The radio service area is slightly larger, reaching further down Cardigan Bay towards Tonfanau near Tywyn. 
1982 saw the rollout of the UK's 4th planned UHF television channel. As with all Welsh transmitters, Arfon was required to carry S4C instead of Channel 4 which is broadcast to the rest of the United Kingdom.
After 22 years of VHF television from this site, the service was discontinued in January 1984. On UHF, Arfon was destined only ever to transmit the originally-planned four of the eventual five analogue terrestrial television channels.
There never was a pre-DSO digital TV service from Arfon.
DSO for the repeaters of Llanddona occurred between 21 October & 18 November 2009. In preparation for this, the transmitting antenna at the top of the Arfon mast was replaced in March 2008. This new antenna is slightly taller than the previous one, resulting in the mast's total height increasing to 317.4 metres (1,041 ft) from its previous height of 313.9 metres (1,030 ft).
On 21 October, BBC2 Analogue was switched off, and ITV1 Wales took over its frequency for its final three weeks of service. BBC Mux A took over channel 41 that had just been vacated by ITV.
The analogue television transmissions from Arfon ceased and were replaced by digital transmissions. Unusually for the UK, the digital transmissions from this site are considerably more powerful than is usual practice considering the ERP of the analogue services that they replace.