The London Twin-Wave Broadcasting Station
Perhaps the most difficult problem which the designer of a Broadcasting Station has to face is the selection of a site which will meet the various essential requirements. Naturally the first step is to consider the exact nature of the service which the projected station is to give, and the circumstances in which the service will be received by the listening public.
The main object of the new London Station is to provide, for a region which consists mainly of London and the South-East Counties, a service of two contrasted programmes, both of which must be sufficiently strong to permit the use of inexpensive receiving apparatus.
Moreover, the important fact that the service had hitherto been provided by a transmitter situated in the heart of London had to be carefully borne in mind, because this transmitter gave overwhelming strength in all districts within a radius of, say, three miles, in spite of the fact that its power was comparatively small.
Naturally this fact affected the type, and even the condition, of receivers used by listeners living within this area, the result being that if an attempt was to be made to distribute the energy more evenly over the whole region by moving the site and raising the power of the transmitter, some dislocation was bound to occur in the immediate neighbourhood of the transmitter which was being replaced.
This difficulty would disappear to a large degree were the designer free to choose any wavelengths he liked for the new station. However, it is now well known that the scarcity of wavelengths available for the broadcasting services of Europe is a severe handicap to development.
Moreover, most of the wavelengths which are available are scientifically not the best possible for the purpose. As the direct result, the broadcasting station which does not possess one of the much-coveted long wavelengths (160 to 224 kilocycles per second; 1875 to 1340 metres) is automatically limited in the range it can give, however much power can be radiated by the aerial.
The economic power for the two wavelengths to be used at Brookmans Park cannot be laid down as a hard and fast quantity, but may be considered to lie between 30 and 50 k.w. of energy in the aerial, and the maximum range in these circumstances is of the order of eighty miles.
This, of course, assumes high quality reception, although, if the standard is lowered, the range is increased to a very large extent; but the B.B.C.'s Regional Scheme has been designed on a basis of high quality, and therefore the above range has to be assumed. These considerations largely determined the power to be used at Brookmans Park.
It was almost out of the question to consider building the new station close to the site of the old, owing to the large amount of space required for the twin transmitters and aerials, but, even apart from this difficulty, it would have been inadvisable for several reasons.
Perhaps the most important of these was the fact that the surrounding buildings would have absorbed a large proportion of the energy radiated and so produced wide variations in the amount of radiation in different directions.
The question then arose as to how far from London the site should be. The dislocation effect has already been mentioned, and this in itself indicated that it would be inadvisable to go much more than fifteen miles away from Oxford Street, in which the old station was situated.
Otherwise, of course, the existing insensitive receivers in the central districts of London would have become useless to their owners.
It was eventually decided that the station should be approximately due north of London and at a distance which was compatible with the above facts. The reasons for choosing a northerly direction are many, but it is only necessary to mention a few. In the first place, there were Government restrictions which made certain districts out of the question.
Again, it was necessary to be near one of the modern Post Office cable routes, in order to connect the new station with Savoy Hill by high quality telephone lines suitable for carrying music. Further, it was obviously desirable not to waste any serious amount of energy over the sea.
Several sites were considered, but none had the advantages of the remarkably flat stretch of land at Brookmans Park, on which the station now stands. It is fifteen miles from Charing Cross as the wireless waves travel, and stands some four hundred feet above sea level, and is therefore one of the highest points in Hertfordshire.
The buildings face the old Great North Road, on the other side of which is Brookmans Park itself, part of which is now rapidly being converted into a building estate. Brookmans Park gets its name from the family which held it in the reign of Henry IV. John Somers, the great Whig Lord Chancellor, lived in a stately old house on the estate, which was burnt down about thirty-five years ago. The mansion which replaced it was the home for many years of the Gaussen family, who sold it to the present owner.
The Broadcasting Station occupies what was once a single field of some thirty-four acres in extent. The building is of a somewhat peculiar shape to conform to the best possible lay-out of the plant, all of which is on the ground floor. The first portion of the building has two stories, but the upper story does not house any of the essential apparatus.
The office block, transmitter hall, and motor generator room, are faced with Portland stone, and the power-house, battery room, and repair shop, which are situated behind the main building, have a multi-coloured brick facing.
Next: The Aerial System
A History of Brookmans Park Transmitting Station by Lilian Caras 1982 (revised January 2002)
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