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.

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