| 词条 | Bala transmitting station | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 释义 |
|name = Bala |image = |map_name = Wales Gwynedd |coordinates = {{coord|52.925439|-3.534341|type:landmark_region:GB|display=inline}} |height = {{convert|45|m|ft|0|abbr=on}} |gridref = SH 969375 |built = |demolished = |collapsed = |relay = Moel y Parc |BBC = BBC Wales |ITV = ITV Wales }} The Bala transmitting station is a facility for television transmission sited about 6 km east of the town of Bala in Gwynedd, north Wales. It consists of a self-supporting 45 m lattice steel mast standing on high ground about 310 m above sea level. It is owned and operated by Arqiva. Currently the site provides digital TV to the area. HistoryThe station was built by the ITA in 1967 to provide a 405-line ITV Band III (VHF) TV service for the area, and was officially classed as a relay of Preseli. In December 1974[1] the site became a low power UHF analogue colour television relay of Moel y Parc; at that time carrying BBC One, BBC Two and ITV. S4C was added in 1982. The 405-line TV system was finally discontinued in the UK in 1985, but Bala's VHF transmitters were decommissioned a year early: in 1984. Digital switchover at Bala happened between 28 October 2009 and 25 November 2009, mirroring events at the Moel y Parc parent station. Channels listed by frequencyAnalogue television26 July 1967 - December 1974All the official documentation claims that Bala was originally classed as a relay of Preseli (which is about 130 km to the south west). However, it is likely that the VHF signal from Preseli would not be receivable at the Bala site, and neither would the signal from Preseli's off-air repeater at Arfon due in both cases to considerable obstruction by mountain ranges. The Moel y Parc transmitter is however only 35 km to the north east, and it is line-of-sight to Bala. Logic says that the 405-line signal was therefore sourced from Moel y Parc, but with the official records saying otherwise it is being shown as a relay of Preseli here. There is an argument to say that Moel y Parc was a relay of Preseli in the 405-line era[2] in that the signal for Moel y Parc came in on an SHF link from Arfon, but since Arfon was an off-air relay of Preseli, that would make Moel y Parc an indirect off-air relay of Preseli. But the official records list Moel y Parc as a 405-line main station (with no ITV repeaters).
December 1974 - 1 November 1982With the coming of colour TV on 625 lines, Bala officially became a relay of Moel y Parc, whilst continuing to relay Preseli's VHF transmission.
1 November 1982 - January 19841982 saw the rollout of the UK's 4th planned UHF television channel. As with all Welsh transmitters, Bala was required to carry S4C instead of Channel 4 which is broadcast to the rest of the United Kingdom.
January 1984 - 21 October 2009After 17 years of VHF television from this site, the service was discontinued in January 1984. On UHF, Bala was destined only ever to transmit the originally-planned four of the eventual five analogue terrestrial television channels.
Analogue and digital television28 October 2009 – 25 November 2009There never was a pre-DSO digital TV service from Bala. DSO for the repeaters of Moel y Parc occurred between 28 October & 25 November 2009. As a first step, BBC2 Analogue was switched off, and the digital BBC Mux A took over on that channel.
Digital television18 November 2009 - presentThe analogue television transmissions from Bala ceased permanently and were replaced by digital transmissions.
See also
References1. ^http://tx.mb21.co.uk/gallery/bala.php 2. ^http://tx.mb21.co.uk/info/405/itv/wales_west.shtml External links
3 : Buildings and structures in Gwynedd|Transmitter sites in Wales|Llandderfel |
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