thebigtower


divis

 

**ALL PAGES UPDATED/ADDED JANUARY 2014**


THE DIVIS TRANSMITTER is the main high-power UHF and BBC National FM/DAB station that serves the counties of Armagh, Antrim and Down in Northern Ireland.

Sited just outside Belfast, it is the primary UHF/FM main station in Northern Ireland and was originally the country's main BBC 405-line television transmitter, coming into operation in this capacity in July 1955.  As such, it was the first permanent television transmitter to be established within Ireland.

Although one of three UHF main stations in Northern Ireland, it is the only one to feature a stayed mast, the other stations at Brougher Mountain and Limavady both utilising smaller self-supporting towers.  Stayed masts are however located at the UHF relay stations at Londonderry and Strabane (respectively former BBC and ITA 405-line relays) and at Black Mountain, the former ITA 405-line main station that is sited adjacent to Divis.

The Divis station is located in a range of hills directly overlooking Belfast to the east, in an area which for many years was controlled by the Ministry of Defence, until it was sold in 2004 to the National Trust and subsequently opened to the public.  It is sited between the peaks of Divis Mountain and Black Mountain and is ironically closer to the latter than the transmitter that is named after it.


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THE MAST AND DIGITAL SWITCHOVER

The original Divis mast from 1955 is a square cross-section lattice stayed structure, typical of those sited on stations originally constructed by the BBC as medium-power installations for their 405-line television network.  It stands at a height of 141.7 metres (465-ft) before the addition of the main UHF aerial aerial at the top.

The main UHF aerial is a ten-tier multi-panel arrangement which was installed in 1992, replacing the original GRP-cylinder-based aerial system that had been in use since 1967.  (See Aerials page).

Having first come into operation in July 1955, the Divis mast is the longest serving in the UK for the purpose of providing continuous television from a main transmission site, earlier masts having been replaced or located on sites not used for broadcasting UHF.

In January 2009, it was confirmed that Divis would join Black Hill, Caldbeck, Rowridge and Tacolneston in requiring a new mast to support the aerial systems needed for Digital Switchover.  The new structure originally had a projected height of 192.7 metres (632-ft) but in the event this has been built to a lesser height of 156.8 metres (544-ft), possibly because of aviation restrictions due to proximity to Belfast International Airport.  Furthermore, it would seem that the new mast is complementing rather than replacing the original mast, the earlier structure apparently being retained.  This decision seems to be connected to the life expectancy of the main UHF antenna on the original mast which, having only been installed in 1992, is likely to remain of serviceable use for at least another ten years.  Exactly how transmission of the UHF service is split between the two masts is still to be clarified.

Had the original mast at Divis been decomissioned, the honour of longest serving television mast would have passed soon after to Pontop Pike at which site the structure became operational in November 1955.


 

 

 

 

 

 

 

 

 

 

 

 

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DIGITAL SWITCHOVER IMPLEMENTATION

Northern Ireland was the last region in the United Kingdom to undergo the switch from analogue to digital and was completed across all transmitters within the region simultaneously.  The process was implemented at Divis as follows -  

Stage 1 (DSO1) - 10 October 2012

BBC2 analogue (Channel 27) closed, Mux 1 (Channel 29) closed, new PSB1 (BBC A) multiplex launched on Channel 27.

Stage 2 (DSO2) - 24 October 2012

All remaining analogue and pre-switchover digital multiplexes closed and replaced by other Public Service Broadcast (PSB2/PSB3) multiplexes and Commercial (COM4/COM5/COM6) multiplexes.

The shutdown of the analogue services at Divis commenced with BBC1 at 11.30pm on 23 October 2012.  This was at the end of a special one-off BBC1/UTV simulcast programme entitled 'The Magic Box' which looked at the history of television in Northern Ireland.  This was followed by a formal announcement regarding the imminent analogue closure in Northern Ireland which also briefly observed the end of analogue television nationwide.

The switch-off at Divis was ceremoniously performed by Dame Mary Peters which featured briefly in subsequent local and national news broadcasts.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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TELEVISION HISTORY

Divis was opened by the BBC on 21 July 1955 as their permanent 405-line Band I transmission facility serving Northern Ireland. It superceded the temporary station at Glencairn, which was one of two transmitters (the other being Pontop Pike) to be rushed into operation on 1 May 1953, in time for the televised Coronation of Queen Elizabeth II.  Although the BBC had by this time already obtained the Divis site, the need to construct the long access road was the primary factor preventing its immediate use for a provisional installation.

Divis was designated as a medium-power transmitter, on which type of installation the second phase of BBC Band I stations were based.  In this respect, Divis was grouped with permanent installations at Meldrum, North Hessary TorPontop Pike, Rowridge, Sandale and Tacolneston.  Transmissions from Divis were on VHF Channel 1 at a peak output of 35kW vision e.r.p.  

In due course, a number of relay stations were established across Northern Ireland to enhance coverage from Divis, most notably at Brougher Mountain in County Fermanagh, the latter being the site of a future UHF main station.

In the meantime, the Independent Television Authority (ITA) built their equivalent 405-line VHF Band III station close to Divis. Located at Black Mountain quarry, less than two miles to the south-west, this came into operation on 31 October 1959 and utilised a taller 750-ft mast.

Divis however became the UHF main station for Belfast and surrounding area with BBC2 the first regular service commencing 18 March 1967.  Colour UHF transmitters for BBC1 and ITV came into operation in September 1970.  


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SITE INFORMATION


Location:

Hannahstown, County Antrim, BT17 0NG

Grid Reference:

J286750

Landlord:

Arqiva (Legacy: BBC/Crown Castle/NGW)

Ground Height:

365.8m

BBC Region:

Northern Ireland

Old Mast Height:

141.7m

ITV Region:

UTV

New Mast Height:

156.8m

 

 

UHF Tx Number:

10700


  CURRENT TRANSMISSIONS

Digital Television

 

 

 

Analogue Radio (FM)

 

 

 

 

 

 

 

 

 

Service

: Ch/Polarisation/e.r.p

 

 

 Station:

(MHz)

(e.r.p)

PSB1

: 27 / H / 100kW 

 

 

BBC Radio 1:

99.7

250kW

PSB2

: 21 / H / 100kW 

 

 

BBC Radio 2:

90.1

250kW

PSB3

: 24 / H / 100kW 

 

 

BBC Radio 3:

92.3

250kW

COM4

: 23 / H / 50kW 

 

 

BBC Radio 4:

96.0

250kW

COM5

: 26 / H / 50kW

BBC Radio Ulster:

94.5

250kW

COM6

: 29 / H / 50kW

 

 

Classis FM:

101.9

250kW

 

 

 

 

 

 

 

 

 

 

 

Digital Radio

 

 

 

 

 

 

 

 

 

BBC National (Block 12B)

 

 

 

 

 

 

 

PRE-DIGITAL SWITCHOVER UHF TRANSMISSIONS

(Shutdown completed 24 October 2012)

Analogue Television 

 

 

 

Digital Television

 

 

 

 

 

 

 

 

 

Service

  Ch/Polar/e.r.p

 

 

 

 

Service

 Ch/Polar/e.r.p

BBC1

: 31 / H / 500kW

 

 

 

 

Mux1

: 29 / H / 2.3kW

BBC2

: 27 / H / 500kW  

 

 

 

 

Mux2

: 33 / H / 2.3kW

ITV1

: 24 / H / 500kW 

 

 

 

 

MuxA

: 23 / H / 2.3kW

Ch4

: 21 / H / 500kW

 

 

 

 

MuxB

: 26 / H / 2.3kW

Ch5

: No Service - transmitted from Black Mountain

 

MuxC

: 48 / H / 2.0kW

 

  

 

 

MuxD

: 34 / H / 1.6kW

 

 

 

 

 

 

 

 

 


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