A look at the Lichfield transmitter
- Population within measured contours: Primary 5.01 mn, Secondary 1.51 mn, Fringe 0.93 mn. Total 7.45 mn.
- Channel: Band III Channel 8 (vertically polarised)
- Vision Carrier Frequency: Actual 189.75 Mc/s
- Sound Carrier Frequency: Actual 186.25 Mc/s
- Effective Radiated Power: Vision 400 kw maximum. Sound 100 kw maximum.
- Power of Transmitters: Vision (peak white) 20 kW. Sound (carrier) 5 kW
- Heights above sea level: Site 500 ft. Mean aerial 1,450 ft.
- Location: 1° 45′ 40″ W, 52° 36′ 30″ N.
Lichfield (Channel 8)
Companies: Associated TeleVision (weekdays), A.B.C. Television (weekends)
Geographically, the siting of a station to serve the industrial Midlands proved fairly straightforward, because the service area of the BBC’s Band I station at Sutton Coldfield corresponded closely with that which the Authority also wished to achieve. High open ground in the area is scarce and, with reason, carefully protected. It was not therefore easy to find an acceptable site. A piece of land 500 ft. above sea level, about four miles north-east of the BBC station, was eventually secured. It lies near the Watling Street in the rural district of Lichfield, from which the station derives its name.
Initially, an available design of 450 ft. self-supporting steel tower was erected, carrying an omnidirectional aerial similar to the one used at Croydon but of twice the aperture. This enabled a service to be provided quickly. The station went into programme service on 17th February 1956 with a single 5 kW transmitter, giving an effective radiated power of 6o kW. A few months later the power was raised to 120 kW by paralleling two 5 kW sets into the split aerial. In November of the same year, after the main 20 kW transmitter had been installed, the power was raised to 200 kW e.r.p. This gave a population coverage of nearly 6.5 million within the o.25 mV/m contouur. From the start it was recognised that, because of the relatively low site, greater and more uniform coverage could be obtained with a higher mast and an aerial system with directional characteristics. Sufficient land was therefore acquired to permit this to be done later.
Early in 1961 it became possible to start the construction of a 1,000 ft. mast and an improved aerial. Both these were brought into service in July of the same year, thus allowing the original tower to be dismantled and re-erected for use at the Fremont Point station in the Channel Islands. The new aerial enabled the power radiated south towards Gloucester to be increased to 400 kW.
Towards East Anglia, however, the power had to be reduced to 100 kW to prevent harmful interference to viewers of the Netherlands Television Service on the Dutch coast. For this reason, the service to Midlands viewers living east of the station remained substantially unchanged. Over a semi-circle towards the north the radiated power was maintained at 200 kW. This was sufficient, with the higher aerial, to close the gaps between the service areas of Lichfield and the Winter Hill and Emley Moor stations. The effect of the new mast and aerial was a general all-round improvement in reception, both within the old service area and beyond. The predicted coverage is shown in the map opposite. The measured coverage has recently been completed and includes a population of 8.85 million within the 0.25 mV/m contour.