Tag: Channel 10

South and South-East England

Southern

  • CHILLERTON DOWN
  • Population within measured contours: Primary 1.91 mn, Secondary 0.53 mn, Fringe 0.52 mn. Total 2.96 mn.
  • Channel: Band III Channel 11 (vertically polarised)
  • Vision Carrier Frequency: Actual 204.75 Mc/s
  • Sound Carrier Frequency: Actual 201.25 Mc/s
  • Effective Radiated Power: Vision 100 kw maximum. Sound 25 kw maximum.
  • Power of Transmitters: Vision (peak white) 4 kW. Sound (carrier) 1 kW
  • Heights above sea level: Site 550 ft. Mean aerial 1,250 ft.
  • Location: 1° 19′ 40″ W, 50° 38′ 55″ N.
  • DOVER
  • Population within measured contours: Primary 0.50 mn, Secondary 0.57 mn, Fringe 0.27 mn. Total 1.34 mn.
  • Channel: Band III Channel 10 (vertically polarised)
  • Vision Carrier Frequency: Nominal 199.75 Mc/s. Actual 199.7135 Mc/s
  • Sound Carrier Frequency: Nominal 196.25 Mc/s. Actual 196.1985 Mc/s
  • Effective Radiated Power: Vision 100 kw maximum. Sound 25 kw maximum.
  • Power of Transmitters: Vision (peak white) 4 kW. Sound (carrier) 1 kW
  • Heights above sea level: Site 450 ft. Mean aerial 1,175 ft.
  • Location: 1° 14′ 58″ E, 51° 6′ 40″ N.

Chillerton Down (Channel 11) and Dover (Channel 10)

Company: Southern Television

Chillerton Down was the first of the two stations built to serve the south and south-east coastal areas of Britain. It was designed to cover central southern England, the important agricultural and holiday area along the coast from Weymouth in the west to Brighton in the east, together with the great ports of Southampton and Portsmouth and, inland, the county of Hampshire and adjoining parts of Dorset and Wiltshire. A BBC Band I station existed at Rowridge, on the Isle of Wight. In conformity with the Government’s policy the Authority decided if possible to build its Band III station close to Rowridge. The site selected was on Chillerton Down, 550 ft. above sea level on the south side of the island. Opposition to a second television mast on the island was raised on grounds of amenity. However, the alternative of building at Rowridge a more massive and commanding tower to carry both the ITA and BBC television services and the BBC’s VHF sound services proved even less welcome, and the Authority’s proposal to use Chillerton Down for a slim 750 ft. mast was accepted.

Chillerton Down
Chillerton Down

The transmitting aerial has a semicircular power-radiation pattern, oriented to direct 100 kW in both directions along the coast as well as landwards, but radiating very low power across the English Channel to prevent interference with the services of Radiodiffusion-Télévision Francaise. Chillerton Down went into service on 30th August 1958 and serves the intended area well.

The sister station at Dover presented unusual problems. The general requirement was to serve the south-east corner of England not covered by Chillerton Down or Croydon. The site of the station was determined by the need to serve Folkestone and Dover, which lie at sea level under high cliffs. The solution was to build the station on the high cliff road linking the two towns. Church Hougham, 450 feet above sea level, was used and from a 750 ft. mast a signal could be directed into both towns. At the same time the station had to link up with the service area of Chillerton Down beyond Eastbourne, 5o miles west along the coast. 100 kW was sufficient to provide an adequate service for Eastbourne and the intermediate coastal towns, and there were no inhibiting power restrictions. Northward, to serve the towns on the Thames estuary not covered by Croydon, 10 kW to 20 kW e.r.p. was adequate. However, viewers in France had to be protected from interference to their reception of the signal from the Rouen station. Calculations showed that Dover must restrict its power to less than 1 kW over an arc of 90° towards the French Coast. It was no mean task to construct a transmitting aerial to do this, and at the same time to radiate 100 kW westward. Test transmissions were made for many weeks, during which the Authority’s engineers developed a measuring technique, using a helicopter, to check the the radiation pattern of the transmitting aerial. This difficult operation accomplished, Dover went into service on full power on 31st January 1960.

West and North Wales

WWN

  • PRESELY
  • Population within measured contours: Primary 0.091 mn, Secondary 0.134 mn, Fringe 0.356 mn. Total 0.581 mn.
  • Channel: Band III Channel 8 (horizontally polarised)
  • Vision Carrier Frequency: Nominal 189.75 Mc/s. Actual 189.75675 Mc/s
  • Sound Carrier Frequency: Nominal 186.25 Mc/s. Actual 186.27 Mc/s
  • Effective Radiated Power: Vision 100 kw maximum. Sound 25 kw maximum.
  • Power of Transmitters: Vision (peak white) 5 kW. Sound (carrier) 1.25 kW
  • Heights above sea level: Site 1,100 ft. Mean aerial 1,835 ft.
  • Location: 4° 39′ 35″ W, 51° 56′ 30″ N.
  • ARFON
  • Population within measured contours: Primary 0.83 mn, Secondary 0.033 mn, Fringe 0.027 mn. Total 0.143 mn.
  • Channel: Band III Channel 10 (horizontally polarised)
  • Vision Carrier Frequency: Nominal 199.75 Mc/s. Actual 199.74725 Mc/s
  • Sound Carrier Frequency: Nominal 196.25 Mc/s. Actual 196.2605 Mc/s
  • Effective Radiated Power: Vision 10 kw maximum. Sound 2.5 kw maximum.
  • Power of Transmitters: Vision (peak white) 2 x 0.5 kW. Sound (carrier) 2 x 0.125 kW
  • Heights above sea level: Site 950 ft. Mean aerial 1,925 ft.
  • Location: 4° 16′ 10″ W, 53° 1′ 10″ N.
  • MOEL-Y-PARC
  • Population within measured contours: Primary 0.132 mn, Secondary 0.145 mn, Fringe 0.057 mn. Total 0.334 mn.
  • Channel: Band III Channel 11 (vertically polarised)
  • Vision Carrier Frequency: Nominal 204.75 Mc/s. Actual 204.75675 Mc/s
  • Sound Carrier Frequency: Nominal 201.25 Mc/s. Actual 201.27 Mc/s
  • Effective Radiated Power: Vision 25 kw maximum. Sound 6.25 kw maximum.
  • Power of Transmitters: Vision (peak white) 2 x 0.5 kW. Sound (carrier) 2 x 0.125 kW
  • Heights above sea level: Site 1,115 ft. Mean aerial 1,815 ft.
  • Location: 3° 18′ 48″ W, 53° 13′ 15″ N.

Presely (Channel 8), Arfon (Channel 10), and Moel-y-Parc (Channel 11)

Company: Wales (West and North) Television

This group of stations was planned to bring Independent Television programmes to the Welsh-speaking populations of West and North Wales, including the area bordering on Cheshire which contains the towns of Denbigh, Mold and Wrexham. The populated areas are mainly along the west coast from Pembroke to Anglesey, and on the north coast from Conway and Llandudno to Prestatyn.

The technical problem was unusually complicated. It has been solved by the establishment of three stations, one on the Prescelly mountains in Pembrokeshire, one on the Lleyn Peninsula, and one on the Clwydian Range of mountains in the Flint-Denbigh area. This plan departed considerably from an earlier one based on sites previously selected for BBC Band I stations.

ill-preselli
Presely

A site for the Presely station was found at Foel Drych 1,100 ft. above sea level, where a 770 ft. mast was sufficient to give the required coverage, although the radiation pattern of the transmitting aerial had to be extremely complicated. A narrow beam radiating 8o kW to the north was required to ensure a reliable programme link to the Arfon relay station. A beam of 100 kW to the south-east, in the direction of Carmarthen and Llanelly, was necessary to ensure that the service area of Presely joined that of St. Hilary; and a broad lobe of 5o kW to the south-west was needed to serve Pembrokeshire. At the same time severe power restrictions had to be incorporated in several directions to avoid co-channel interference in the service areas of the ITA’s transmitters at Strabane, Burnhope and Lichfield, the Kilkenny station of the Irish Republic, and the French stations serving the coast of Brittany. Intensive development was necessary to construct an aerial with this complicated radiation pattern.

The unattended Arfon station, which rebroadcasts the Presely transmissions, is at Bryn-ychain, ten miles south of Caernarvon, 950 ft. above sea level. A 1,ooo ft. mast was used to “see” over the mountains of Portmadoc to the coast of Cardigan Bay from Harlech to Barmouth, and to ensure the link with the service area of Presely. A directional aerial was again necessary. 10 kW is radiated to the north and south-west, 5 kW to the east and south-east, and 2.5 kW to the west.

The third station is at Moel-y-Parc, a peak in the Clwydian Range 1,100 ft. above sea level, and serves the North Wales area. A 750 ft. mast was found adequate to reach the coastal resins from Conway to Prestatyn, which are shielded by mountains close to the coast. The radiation pattern of the transmitting aerial is approximately semicircular, 25 kW being radiated from south-east to north-west with reduced power to the north and east. This was necessary to cover the Welsh areas but to avoid overlap with English areas already served by Winter Hill. Moel-y-Parc rebroadcasts the transmissions from the Arfon station, conveyed to it by an off the air pick-up at Nebo, in Anglesey, followed by a microwave link.

All three stations for the west and north of the Principality were in programme service by early 1963.

Central Scotland

Scottish

  • Population within measured contours: Primary 3.23 mn, Secondary 0.54 mn, Fringe 0.21 mn. Total 3.98 mn.
  • Channel: Band III Channel 10 (vertically polarised)
  • Vision Carrier Frequency: Nominal 199.75 Mc/s. Actual 199.7305 Mc/s
  • Sound Carrier Frequency: Nominal 196.25 Mc/s. Actual 196.2395 Mc/s
  • Effective Radiated Power: Vision 475 kw maximum. Sound 120 kw maximum.
  • Power of Transmitters: Vision (peak white) 2 x 10 kW. Sound (carrier) 2 x 2.5 kW
  • Heights above sea level: Site 900 ft. Mean aerial 1,850 ft.
  • Location: 3° 52′ 25″ W, 55° 51′ 45″ N.

Black Hill (Channel 10)

Company: Scottish Television

The construction of this station, on a site 900 ft. above sea level and midway between Glasgow and Edinburgh, began in the late summer of 1956. The station was designed to serve the central lowlands of Scotland, covering a population of nearly four millions within the o.25 mV/m contour.

The selection of the site was straightforward, but there was difficulty in obtaining the land.

A study of the topography within the required service area of this station established the need for a 750 ft. mast and it was evident that the best possible coverage could be obtained only by using a directional aerial system. It was important that, if possible, both Dundee in the north-east and the towns on the Ayrshire coast in the west should be included in the service area. Little benefit, however, would result from radiating high power into the hilly north-westerly or south-easterly directions. It thus appeared that an aerial having an elliptical power distribution pattern with its major axis aligned to the north-east and south-west would provide the best result. However, an international limitation on power in certain directions made it necessary to compromise and to design an aerial whose radiation pattern can best be described as “boot”-shaped, the “heel” (250 kw) directed towards the south-west and the “sole” (475 kW) directed to the north-east. A power of about 150 kW was adequate for the northwest and south-west directions.

ill-black hillA novel 16-stack vertically-polarised directional aerial system was developed, possessing many useful features, which attempted to approximate to the optimum power-radiation pattern. The aerial was located centrally within the mast structure to radiate through the opening of the lattice steel formation of the mast, mainly to reduce the wind loading and icing on the exposed site.

Unfortunately, complex anomalies in the behaviour of this aerial caused its performance to deviate from the prediction. The desired power in the various directions was not completely achieved, while the radiation in the south-west sector in the direction of Ayr was predominantly horizontally instead of vertically polarised. The result was a marginal shift in the potential service area of the station. These anomalies had to be accepted for the time being, and the station came into service on 31st August 1957.

In 1959 it was decided to replace the “inside the mast” aerial by one of more conventional form, with the radiators mounted outside the mast. In order to ensure continuity of service, it was also decided to erect the replacement aerial on a new 1,ooo ft. mast near the original mast.

The difficult task of constructing the new mast close to the old began in August 1960. It was brought into use together with the new aerial on 10th July 1961. The 750 ft. mast was dismantled and has been used at the Selkirk station in the Borders. The performance of the new aerial at Black Hill is satisfactory and has resulted in an enlargement of the service area and in improvements to reception generally.

South Wales and West of England

TWW

  • Population within measured contours: Primary 1.517 mn, Secondary 1.0 mn, Fringe 0.77 mn. Total 3.287 mn.
  • Channel: Band III Channel 10 (vertically polarised)
  • Vision Carrier Frequency: Nominal 199.75 Mc/s. Actual 199.7305 Mc/s
  • Sound Carrier Frequency: Nominal 196.25 Mc/s. Actual 196.2395 Mc/s
  • Effective Radiated Power: Vision 200 kw maximum. Sound 50 kw maximum.
  • Power of Transmitters: Vision (peak white) 20 kW. Sound (carrier) 5 kW
  • Heights above sea level: Site 400 ft. Mean aerial 1,100 ft.
  • Location: 3° 24′ 15″ W, 51° 27′ 25″ N.

St. Hilary (Channel 10)

Company: T.W.W.

This station brings the Independent Television programmes to the Welsh and English populations adjacent to the Severn Estuary and the Bristol Channel. With the limited number of Band III channels available to the Authority, each one had to be used to serve the maximum possible geographical area. In May 1955, studies were begun to determine which of a number of approaches to the problem of covering South Wales, North Somerset and North Devon was the best. The coverage potential of sites to the south of the Estuary in the Mendips and the Quantocks, as well as on the north shore in various parts of South Wales, was investigated.

A site was selected at St. Hilary Down, on the Welsh side of the estuary, between Cardiff and Swansea, and 400 ft. above sea level. This gave the maximum potential population coverage of the densely populated areas of industrial South Wales and Monmouthshire, and was adjacent to the BBC Band I station at Wenvoe a few miles to the east, serving broadly the same geographical area.

ill-st hilaryThe mast height at St. Hilary is 750 ft. The Authority would have preferred 1,000 ft., but air navigation considerations precluded this. Even so, approval for the site had to be withheld by the Glamorgan County Council pending a public enquiry, held in March 1957, to resolve the objections to the mast lodged by the airline companies operating from the nearby Rhoose Airport. The effective radiated power is 200 kW omni-directional, because directional characteristics would have been of little avail in improving the service for the many valleys of South Wales, which radiate northwards like spokes of a wheel from the “hubs” of Cardiff and Newport.

A major redesign of the aerial system had to be undertaken, because the intended “inside the mast” type of aerial, the prototype of which had just been tested at the Black Hill station in Scotland, had been found to be deficient.

The station was opened for programmes, with an aerial of more conventional design, on 14th January 1958. It has given the high grade of service predicted, but the fundamental limitations of Band III transmission and reception in mountainous terrain when compared with Band I led to some public disappointment about the comparative grades of service in some shielded locations in the deep valleys of South Wales and also in low-lying parts of the cities of Bristol and Bath. The use of well designed receiving aerials and of more sensitive “fringe area” receivers has overcome, in part, the low signal strength and the “ghost” images experienced in such localities.