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Visitors to the Olympia Radio Show who see there the demonstrations of television reception from the Alexandra Palace will be interested in this description of the arrangements at the transmitting end. The alternative systems are described here.
From a hill 306 ft above sea level the BBCs new television station dominates London and a large portion of the Home Counties. It is built into the south-eastern corner of Alexandra Palace - a North London landmark and pleasure resort for more than sixty years - and from the larger bay windows of the upper offices below the aerial nearly all London can be taken in at a glance. The importance of height in this connection can hardly be over emphasised, for under normal conditions the range of the ultra short waves used for television is extended as the height of the transmitting aerial is increased.
Surmounting the reconstructed east tower, itself 80 ft high, is the tapering lattice mast rising to a height of 220 ft. Thus the aerial array for vision transmissions, which is mounted at the summit of the mast, is more than 600 ft. above sea level. Immediately below the vision aerial is the aerial for the accompanying sound transmissions.
Transmitting an outdoor view with a Marconi-EMI instantaneous camera.
The new station fulfils the recommendations of the Television Advisory Committee appointed to consider the development of television in Great Britain. Provision has accordingly been made for alternate experimental transmission by the systems developed by the Baird Television Company and the Marconi-EMI Television Company respectively. Each company has provided a complete television system, including both vision and sound pick-up apparatus and the television transmitter itself. The BBC has been responsible for the sound transmitter and its associated aerial, both of which were manufactured by Marconi's Wireless Telegraph Company.
In its main essentials, therefore, the equipment comprises a television studio for each system with an associated control room and ultra short wave television transmitter; and, in addition, an ultra short wave sound transmitter common to both systems.
To these bare necessities, however, much has been added to provide, in the words of the Television Committee, an extended trial of two systems, under strictly comparable conditions, by installing them side by side at a station in London where they , should be used alternately - and not simultaneously - for a public service. Provision has been made for the comfort of artists in the shape of dressing rooms and a restaurant, for staff accommodation, for the viewing and editing of films in miniature cinema, for the storing of properties and scenery, for many other adjuncts necessary to a smooth-working programme service. Practical experience during the next few months will doubtless disclose gaps in the existing equipment, but the station, as it now stands, constitutes the first step towards the creation and radiation of television programmes.
The ground-floor corridor houses the three transmitters, projection theatre, restaurant and scenery productions shop. Nearest to the entrance hall is the Marconi-EMI television transmitter which, like its Baird equivalent, operates on a frequency of 45 MHz (wavelength 6.67 metres).
The Sound Transmitter
Next is the sound transmitter hall which accommodates an ultra short wave installation of orthodox design for radiating speech and music accompanying the vision signals of both Baird and Marconi-EMI systems, Its operating frequency is 41.5 MHz (wavelength 7.23 metres).
Between the sound transmitter and the Baird plant is the film projection theatre, or miniature cinema, in which film excerpts can be selected and timed for inclusion in the transmissions. At least thirty people can be comfortably accommodated.
The Baird transmitter hall, with its control panel and array of generators and amplification stages, is at the south-west end of the corridor. Beyond this, at the south-west extremity of the BBC section of the Palace, is a large area intended either for scenery construction or for televising such objects as motor cars and animals which can not be brought into the studio or televised outside.
An interesting feature at this point is the ramp or sloping runway down which the television camera can travel to a concrete 'apron', approximately 1,700 sq ft, on the terrace outside, forming a platform for televising open-air performances or special experimental programmes.
Studios
An instantaneous television camera seen in action on the right of the Marconi-EMI studio.
On the second floor is the Marconi-EMI studio. Measuring approximately 70 ft by 30 ft, with a height of 25 ft, this studio is divided into two stages A and B - of which A, the larger, gives an acting area of approximately 24 ft. square. It is equipped with two sets of tableau curtains. Lining the studio on two sides are hanging velvet curtains running on two tracks, the front curtain being black and the back one white to allow for interchange of backgrounds. Each stage has separate lighting, controlled from a central switchboard. Emitron instantaneous television cameras are used. Across the middle of the studio runs a steel lighting bridge which will allow additional lights to be trained on either stage.
High up in the west wall a large plate-glass window indicates the position of the control room, where the producer and the engineering assistant operate. The floor, is covered with thick black linoleum and the walls are acoustically treated with an asbestos compound.
Next to the control room, already mentioned, is the Marconi-EMI telecine room containing two projectors and scanning cameras for televising films.
Leaving the EMII 'territory', the Baird telecine room comes next: It is also fitted with two projectors and the necessary equipment for film transmissions. Next to this room is an additional small studio to be used with the Baird Company's 'spot light'; system of direct television of three-quarter length portraits such was would be required for announcements and talks.
The intermediate film scanner in the Baird studio is seen on the left of the picture.
The main Baird studio is the same size as its EMI counterpart. The floors and walls are of similar construction, but the arrangement of the stages is different. The larger stage is placed diagonally to the intermediate film camera room, which is situated in the centre of the studio and looks rather like a bay window of a modern villa viewed from without. The curtains are the same as in the Marconi-EMI studio, but the hanging arrangements differ in that they have to suit the different position of the two stages.
A portion of the Baird control room.
Baird tele-cine scanner and control rack.
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