The following artical is taken from the Wireless and Electrical Trader magazine of the 13th October 1951. The official opening of the station took place on October 12, from the Town Hall, Manchester. Special programmes, including some outside broadcats from the North, were televised to mark the extension of television to this large new area.
Holme Moss Brings Television to Eleven Million People
THE B.B.C. programme for the extension of television in Great Britain took another stride forward by the official opening on October 12 of the Holme Moss transmitter, situated on the Pennines about 9 miles to the S.W. of Huddersfield.
The Hoime Moss station, which is deigned to bring television within reach of 11 million people, over and above the 18 million already served by the Alexandra Palace and Sutton Coldfield stations, is on the highest site of any British TV trans mitter, existing or projected, being 1,750ft above sea level.
The station comprises a building housing the two main transmitters for vision (45 kW) and sound (12kW), a smaller building for two stand-by transmitters (vision 5 kW, sound 2 kW), a 750ft main aerial mast and a 150ft stand-by aerial mast. The vision transmitter operates on a carrier frequency of 51.75Mc/s (5.8m) and the sound transmitter on 48.25 Mc/s (6.2m), these being in channel 2 of the British television band.
Hoime Moss transmits the same programmes as the stations in the London and Midland regions, which are sent from London via Birmingham and Manchester over co-axial cables rented from and operated by the G.P.O. The signals can be sent in both directions simultaneously. In the unlikely event of a breakdown in the co-axial link, it has already been found that a receiving aerial mounted several hundred feet up the main transmitting aerial mast is capable of providing a signal direct from Sutton Coldfield for modulating the Hoime Moss transmitter as a temporary expedient. Estimated field-strength contours for the new transmitter are shown in the map below.
The site and the station itself, being on a wild moorland, have presented many difficulties in clearing, design and construction. In particular, many precautions have had to be taken to proect the installations from the effects of winter, including high winds and heavy snow-drifts. Special provision for heating and ventilation, as well as for the comfort, feeding and sleeping of the staff, who may be marooned in the station for long periods, has been necessary.
The main mast, 750ft high and weighing 140 tons, follows broadly the design of that at Sutton Coldfield. Up to 610ft the mast is of triangular section open steel-work, and for the next 100ft it is circular, with provision for slot aerials for V.H.F. transmission in the future. Above the circular section is a square-section topmast supporting the television aerial.
The supporting steel stay ropes are designed to deal with more severe conditions than at Sutton Coldfield, including severe gales equivalent to 125 m.p.h. at the mast head, and a ½-inch coating of ice throughout. No lift is provided, partly because it would probably be unusable when most needed, and partly on account of the fact that, as the sound and vision combining filter is housed in the main building, there is less equipment at the mast-head likely to need attention.
The section of the building housing the main transmitters is divided longitudinally into three main-areas. In the central area are the sound and vision transmitters in line, and behind them the second area is divided into three, the centre section containing the power conversion plant, and the two end sections the valve cooling plants. Along the other side of the transmitter hall, formng the third section, is the control room, placed centrally, and flanked by the vision and sound lines termination rooms.
Final stage of the main transmitter's modulator
with each valve indivicually metered.
The vision transmitter is the most powerful in service anywhere in the world (though the Sutton Coldfield transmitter can now be raised to 45-kW output, it is understood). It is 31ft long, and is divided into eight cubicles, with R.F. stages arranged in order of increasing power from left to right, and modulator stages from right to left.
The sound transmitter is 15ft 6in long, and is similar to that at Sutton Coldfield, with an output of 12kW. Each transmitter has its own valve cooling plant (water cooling for the vision output stage, and air cooling for the remainder), and use is made of the heat generated to warm the building.
The vision transmitter supplies a double sideand signal to its output feeder, and the upper sideband of this signal is attenuated in the vestigial sideband filter connected between the transmitter output and the combining unit. The latter combines the outputs from the sound and vision transmitters and feeds the combined output to the 51.5 ohm 5in diameter co-axial feeder leading to the aerial. This unit avoids the use of the diplexer at the top of the mast, as at Sutton Coldfield.
The aerial array (which radiates both vision and sound signals) comprises eight
vertical folded dipoles arranged in two identical groups of four, one above
the other. The dipoles are made of galvanized steel strip and incorporate 7½kW
heaters to prevent ice formation. They are improved versions of those at Sutton
Both sound and vision transmitters are operated from a single control desk in the control room, which has two 12in picture monitors showing the picture at the modulator input, and as radiated.
Installed in a separate room are the stand-by transmitters which can be connected to the main or reserve aerials by switches. They are quite independent of the equipment in the main building, and can be quickly put into service if required. They have their own small control desk.
The vision signals radiated from Hoime Moss give a quality of picture unimpaired by the coaxial cable links from Alexandra Palace. Viewers in the North can count on a picture in every respect equal to that received in the London area.
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