It has a 235.4 metres (772 ft) high guyed steel lattice mast (just one foot taller than Britain's tallest skyscraper, 1 Canada Square). It was constructed in 1962 by the IBA to transmit ITV405-line television with transmissions commencing on Band III channel 8 from antennas at 559 m (1,835 ft) above sea level. The triangle of antenna arrays aimed beams of signal towards Pembrokeshire, another lobe was directed towards western Carmarthenshire and a northward beam covered south western Ceredigion. The northward beam from the site also fed the transmitter at Arfon in North Wales.
The Welsh region ITV programming was initially provided by Teledu Cymru which was taken over by TWW in 1964, and eventually HTV Wales who took over from 1968.
In 1971, three protesters from Cymdeithas yr Iaith Gymraeg were jailed for "conspiring to trespass" after gaining access to the site compound and climbing the lower section of the mast. This was part of a series of protests in Wales aiming to get a dedicated Welsh-language TV channel established. The campaign was eventually considered to have been mostly successful with the establishment of S4C (Sianel 4 Cymru) eleven years later.
The site was uprated in 1973 to transmit UHF625-linePAL analogue television channels, starting with BBC1, BBC2 and HTV Wales, with S4C being added in late 1982. The VHF channel 8 transmissions were discontinued in January 1985 as 405-line TV in the UK was phased out. Channel 5 started analogue TV transmissions in 1997. Six digital TV multiplexes were added in 1998 and the site kept this configuration until 2009 when all analogue television signals were permanently switched-off.
Channel 5 started broadcasting on UHF channel 37. A fifth analogue TV channel was outside the design specifications of the British UHF transmitter plan and this forced the use of out-of-band channel 37 which was supposed to be kept clear of transmissions.
This was the initial roll-out for digital television using the DVB-T system. The transmitter frequencies and power outputs were chosen not to interfere with the UHF TV channels, but to be received with the same aerial-group. The QAM constellations and number of carriers were changed around 2002 after the collapse of ITV Digital as the service was taken over by the Freeview consortium.
BBC Two Wales on channel 40 closed after 36 years of service, and HTV Wales was moved from channel 43 to the vacated channel 40 for what would be its final month of service.
Multiplex 1 on channel 47+ was renamed BBC A and moved to channel 43+ (which had just been vacated by analogue HTV Wales). In addition to the power increase to 20 kW ERP, it was reconfigured to 64QAM and 8k carriers, which resulted in a service area similar to the old analogue transmissions but with much more bandwidth available than Multiplex 1 ever had.
For the duration of the switchover, all the channels carried on Multiplex B were duplicated on this new PSB1 multiplex.
All remaining analogue television was shut down after 36 years of service. The pre-switchover low-power digital transmissions (apart from Arq A and SDN) were upgraded to full power and configured to 64QAM and 8k carriers, with some frequency changes and with new names for the multiplexes:
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, Preseli's "Arqiva B" multiplex was moved from channel 49- to channel 39+ and the "BBC B" multiplex was moved from channel 50+ to channel 40+.