thebigtower


caradon hill

 


THE CARADON HILL TRANSMITTER is the UHF and DAB main station that serves Central and East Cornwall and some parts of North and West Devon.

It is the primary UHF main station in the south-west of England and accordingly is the highest powered, originally transmitting at a maximum Effective Radiated Power (e.r.p) of 500 kilowatts for UHF analogue and now 100 kilowatts post-Digital Switchover.

Four other main stations, sited at Beacon Hill (South Devon), Huntshaw Cross (North Devon), Redruth (West Cornwall) and Stockland Hill (East Devon), combine (with their dependent relays) to serve the region, whilst primary responsibility for BBC National FM radio transmission in the south-west is held by the North Hessary Tor transmitter.

From it's position on one of the most easterly summits of Bodmin, Caradon Hill originally transmitted ITV on 405-line VHF to the south-west region, a function primarily undertaken jointly with the Stockland Hill transmitter.  (See Television History - VHF)


 

 

 

 

 

 

 

 

 

 

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Aerials (1)>  Aerials (2)>  Buildings 2007 (800 or 1024)>  Buildings 2010 (800 or 1024)>  Supersize Images>  UHF Maps  


DIGITAL SWITCHOVER

As the primary UHF main station in the region, Caradon Hill was the last transmitter group in the south-west to complete the Digital Switchover process.  This was implemented in two stages as follows -

Stage 1 (DSO1) - 12 August 2009

BBC Two analogue on Channel 28 ceased broadcasting permanently and PSB1 multiplex (BBCA) launched on Channel 28.

Stage 2 (DSO2) - 9 September 2009

All other analogue services ceased broadcasting permanently and high powered digital multiplexes launched.

DIGITAL SWITCHOVER WORK

Principal re-engineering work in preparation for Digital Switchover at Caradon Hill commenced in 2007.  Installation of the new ten-tier cylindrical reserve aerial took place between June and September 2007 (See Aerials (1) for images of this work in progress) whilst replacement of the main UHF aerial at the top of the mast was completed in 2008 (See Aerials (2).


 

 

 

 

 

 

 

 

 

 

 

 

Aerials (1) - August 07

 

Aerials (2) - September 08

 

UHF Coverage Maps

 

 

 

 

 (With Summary Images)

 

 

 


TELEVISION HISTORY (VHF)

Caradon Hill was built by the Independent Television Authority (ITA) as the principal of two high-power stations needed to establish an Independent Television (ITV) service in the south-west of England on the 405-line VHF Band III system.

The area the ITA aimed to cover was approximately 150 miles in length encompassing Cornwall and Devon, with some parts of Somerset.  Two areas of high ground dominated the centre of the region, the Bodmin Hills in Cornwall and Dartmoor in South-West Devon, with the latter hosting the existing BBC VHF Band I transmitter at North Hessary Tor.

The topographical characteristics present here were very similar to those the ITA had faced in Northern England, where they had to build separate stations for Lancashire and Yorkshire (Winter Hill and Emley Moor respectively) rather than a single station centrally-placed within the Pennines near the BBC Band I transmitter at Holme Moss.  This was due to the reduced capability of Band III transmission in comparison to Band I when traversing a large area dominated by a central ridge of high ground.

With engineering tests confirming that a single centrally-placed ITA station close to North Hessary Tor was also impractical, the authority had to deviate for the second time from the practice of adjacent siting with the BBC and also had to obtain government permission to build the two stations that were now needed respectively for Cornwall and Devon.

Caradon Hill, the site chosen for the Cornwall transmitter, was located near Launceston on the eastern fringe of the Bodmin Hills. Allocated VHF Channel 12, the station was required to serve parts of West Devon and the whole of Cornwall, extending from Dartmoor's western sectors in the east to Land's End and The Scilly Isles in the west, with some coverage across North Devon also desirable.  The site was 1211-ft (369 metres) above sea level and so a 750-ft (228-metre) mast was deemed sufficient to provide the overall elevation required for transmissions to be carried effectively.  

Two vision transmitters were installed on site, both rated at an actual power of 5kW, along with two sound transmitters both rated at 1.25kW.  Typically, the aerial system was engineered to deliver varying power output according to direction, the highest power of 200kW (vision e.r.p) being directed west-south-west towards Land's End.  Across the north-western arc power was limited to only 10kW and across the southern arc just 25kW, avoiding interference respectively within the service areas of the Dublin and Cherbourg stations which also used Channel 12.

The site of the second ITA station was at Stockland Hill, near Honiton, which served most of Devon as well as parts of Somerset and West Dorset.  Both Caradon Hill and Stockland Hill came into regular operation on 29 April 1961 with the start of the region's ITV service provided by Westward Television.  The combined output from both stations achieved the desired coverage across the majority of the target area, extending the ITV service to approximately 1.5 million people.

One vindication of the decision by the ITA not to build a single station close to North Hessary Tor was the superior coverage from Caradon Hill in comparison to that of the BBC to areas on the western extremity near to Land's End, where reception of the BBC station was sub-standard even with the benefit of VHF Band I, necessitating the construction of a further BBC transmitter at Redruth in 1962.

To the disappointment of the ITA however, the level of coverage they had hoped to achieve across North Devon as a supplement to the primary coverage area did not materialise, due mainly to the power limitations imposed on transmissions in this direction. The areas most affected were along parts of the northern coast and in-land around Barnstaple where transmissions into North Devon from Stockland Hill were also stretched to the limit.  The resolution to this came eventually on 22 April 1968 with the opening of the relay station at Huntshaw Cross.


Aerials (1)>  Aerials (2)>  Buildings 2007 (800 or 1024)>  Buildings 2010 (800 or 1024)>  Supersize Images>  UHF Maps  


 

 

 

 

 

 

 

 

 

 

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TELEVISION HISTORY (UHF)

The use of both Caradon Hill and Stockland Hill for UHF transmission was effectively inevitable from the outset, as it was in other instances of ITA 405-line transmitters with non-adjacent siting to BBC equivalents.

By the very nature of UHF however, the transmission range of Caradon Hill was typically less than that achieved with VHF Band III.  Even with an Effective Radiated Power of 500kW, two and half times higher than the maximum output on Band III, UHF coverage from the station left much of West Cornwall excluded or at best with sporadic reception, requiring an additional UHF main station to be established on the site of the existing BBC transmitter at Redruth.

The first UHF transmitter in service from Caradon Hill was BBC2 from 5 July 1969, bringing UHF-colour to Cornwall for the first time.

In it's capacity of primary UHF main station in the region, Caradon Hill was the designated site for the ITA Colour Control Room (CCR) for the south-west which was constructed within the existing main building in preparation for the start of the ITV UHF-Colour service.

Transmission of BBC1 and ITV in UHF-colour commenced simultaneously from Caradon Hill and Redruth on 17 March 1971 and 22 May 1971 respectively.

The Colour Control Room became operational with the start of the ITV UHF-Colour service and would be responsible for all ITA UHF and VHF television transmitters in the south-west until replacement by the Regional Operation Centre (ROC) at St Hilary in 1980.


Site Building Images

 

 

 

 

East side images from 2007

 

South-West to East images from 2010

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 (800x600 version includes station plates)

 

 

 

(Both sets illustrate the unusual positioning of the digital television transmitter building on the main concourse, blocking much of the front view of the original ITA main building)


STATION INFORMATION


Location:

Caradon Hill, Minions, Cornwall, PL14 5LT

Grid Reference:

SX273707

Landlord:

Arqiva (Legacy: ITA/IBA/NTL Broadcast)

Ground Height:

369m

BBC Region:

South-West

Mast Height ("):

228.9m

ITV Region:

South-West

Aerial Height (*):

603m

 

UHF Tx Number:

13100

(") Main structure height excluding UHF antenna

 

 

(*) Average UHF aerial height above sea level (a.o.d) 

 

 


 CURRENT TRANSMISSIONS

Digital Television 

 

 

 

Analogue Radio (FM)

 

 

 

 

 

 

 

 

 

Service

: Ch/Polarisation/e.r.p

 

 

 Service:

(MHz)

(e.r.p)

PSB1

: 28 / H / 100kW  

 

 BBC Radio Cornwall:

95.2

4.3kW

PSB2

: 25 / H / 100kW 

 

Pirate FM:

102.2

2.5kW

PSB3

: 22 / H / 100kW   

 

 Heart FM:

105.1

2.5kW

COM4

: 21 / H / 50kW 

 

 

COM5

: 24 / H / 50kW 

Digital Radio (DAB)

COM6

: 27 / H / 50kW

 

 

 

 

 

 

 

 

 

 

BBC National (Block 12B)

 

 

 

 

 

Digital One (Block 11D)

 

 

 

 

 

 NOW Cornwall (Block 11B)

 

 

 

 

 

 

PRE-DIGITAL SWITCHOVER UHF TRANSMISSIONS

(Shutdown completed 9 September 2009)

Analogue Television 

 

 

 

Digital Television

 

 

 

 

 

 

 

 

 

Service

  Ch/Polar/e.r.p

 

 

 

 

Service

 Ch/Polar/e.r.p

BBC1

: 22 / H / 500kW

 

 

 

 

Mux1

: 34 / H / 5.0kW

BBC2

: 28 / H / 500kW  

 

 

 

 

Mux2

: 31 / H / 4.0kW

ITV1

: 25 / H / 500kW 

 

 

 

 

MuxA

: 48 / H / 4.0kW

Ch4

: 32 / H / 500kW

 

 

 

 

MuxB

: 21 / H / 4.0kW

Five

: No service

 

 

 

 

MuxC

: 24 / H / 4.0kW

 

 

 

 

 

 

 

MuxD

: 27 / H / 4.0kW

 

 

 

 

 

 

 

 

 


Beacon Hill  Huntshaw Cross  North Hessary Tor  Redruth  Stockland Hill

 

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