Radio recording technology
Empire Service requirements
The development of the Empire Service which started in 1932 raised in an acute form the need for an efficient but cheap high quality recording system so that programmes could be repeated at different times of the day to suit the local listening hours in different parts of the world. Up to the outbreak of war, much development was done and at that time the BBC already had three systems of recording in current use: magnetic recording on steel tape, a mechanical system of recording on film for subsequent photo-electric reproduction, and a system of recording by lateral cut in a cellulose coating on metal discs.
Wartime needs enormously increased the demands on the recording services, both for home and overseas programme purposes, and in the disc system alone over 5,000 discs a week were used by 1944.
The record machine made records in the form of discs which were somewhat similar in appearance to ordinary 12-inch gramophone records, but consisted of a coating of special cellulose varnish on a base of aluminium. They were ready for playing as soon as the record had been cut, without any of the elaborate intermediate processes involved in making ordinary records, and each disc could be played twenty or thirty times before it became noticeably worn.
Electric currents, corresponding to the sound waves picked up by the microphone, cause vibrations of a recording stylus which cuts a wavy spiral track in the varnish on the surface of the disc. The spiral motion is obtained by causing the recording head which carries the stylus to move slowly across the surface of the disc while the latter is rotating on the turntable.
When the disc is played, currents similar to those which were applied to the recording cutter are produced by the vibrations of the needle in the gramophone pick-up; after amplification these currents can be made to reproduce the original sound through a loudspeaker, either directly or through the medium of wireless transmission.
The recording of sounds and interviews outside of the confines of a studio could sometimes be done by roving microphones, connected by telephone line to a studio centre; but for places remote from telephone lines, or at times unsuitable for broadcasting, a mobile recording unit was essential.
There were two kinds of mobile equipment: a heavy type mounted in a large van, and a light portable apparatus carried in a saloon car. The recording machines which were similar in principle to those used in the disc-recording rooms at BBC studios.
BBC mobile recording vans
A mobile unit of the heavier type consisted of a motor van, weighing about six tons when laden, the body of which was divided into two compartments. One compartment was acoustically treated so as to form a small studio suitable for speech. The other contained two sets of recording equipment (so that a continuous recording could be made by passing 'from one turntable to the other' as each disc was finished) together with the associated amplifiers, the controlling and switching equipment, and the battery-charging plant.
Recordings could be made either of speech from the microphone in the studio compartment, or of speech or other sounds picked up by other microphones outside the van and connected to it by cables. The van could work away from its base, if necessary, for several weeks at a time and, since the equipment was all operated from batteries which could be charged from the engine of the van, it was self-contained and independent of electric supply mains.
The size of the van made it possible to accommodate the most complete technical equipment for controlling the programme and checking the accuracy of the recording, and also to employ the most robust and convenient form of recording apparatus. The turntables could be made level by hydraulically-operated adjustments so that recordings could be made when the van was standing on a slope. The speed of the turntables could be accurately adjusted, and gramophone pick-ups and a loudspeaker were provided for reproducing sound from the records when necessary.
Archie P Lee described his first pre-war experience of the mobile recording unit, which had been specially brought up from London to cover the International Sheep Dog Championships at Ayr Racecourse:
This proved to be a vehicle as huge as a furniture van — or today's television mobile control room. Its front wheels had pneumatic tyres but the rear ones were shod with solid rubber. The several hundredweights of recording machinery packed into that seven-ton truck were very delicate as well as very heavy, so the engine was fitted with a 'governor' which shut off the power as soon as you went above 20 miles an hour. The journey from London to Ayr had taken a week.
During the early part of the Second World War, one of the units was under Richard Dimbleby in France, and the other under Bernard Stubbs based on London. The former enabled listeners at home to hear at first hand about the life and war service conditions of the Forces in France. On the Home Front, the recording van was busy touring dockyards, hospitals, munition factories and ARP centres. It recorded the rich voices of the two eye-witnesses of the early German air raids over eastern Scotland.
Wartime mobile recording units
In 1938 the BBC News Department felt the need for a mobile unit which could travel rapidly to any part of the country, obtain a topical news story, and bring the records back the same night (to London or any other BBC studio centre) to be included in the news bulletins. The apparatus had to be sufficiently compact to fit into an ordinary saloon car, light enough to be carried into a building or set up in an aeroplane, and robust enough to withstand travelling over bad roads at high speeds. Although it would normally be used in the car, the apparatus had to be readily movable so that it could be carried by hand to places to which the car could not be taken. It had also to be independent of external power supplies and to be suitable for use not only as a recording unit, but also for direct outside broadcasting work where suitable Post Office telephone lines were available to carry a live 'broadcast'. It was also necessary to provide facilities for reproducing a recording and connecting the output to a telephone line where there was not time to bring the records to a studio centre.
The resulting machine which BBC engineers came up had some disadvantages: it could not make a continuous recording lasting longer than the duration of a single disc (about four minutes), and it lacked many of the facilities and refinements which are provided by the heavy van. But where speed was essential it had a great advantage, because the saloon car was not subject to the statutory speed limit of 20 miles an hour, which was imposed on the large van; moreover, it could be manoeuvred more easily in narrow streets and parked in more restricted spaces.
With reference to the photograph, the supply unit is seen on the floor behind the driver's seat. The amplifier rests on the top of it and the recording machine stands on the rear seat of the car. The batteries were carried in the luggage boot and their connecting cables run through the back of the rear seat. The luggage boot also contained cable drums holding up to 400 yards of screened microphone cable; telephone sets for communication between the microphone points and the recording engineer in the car; the three-channel mixer; loudspeakers; a telescopic microphone stand; and a kit of tools. There were also headphones for checking the programme when it is not convenient to use a loudspeaker.
If the recording was made in Britain, the disc would normally be taken to one of the BBC studio centres or played back in the car itself, the output being connected by a telephone line to the studio centre. For reproducing recordings in this way, the car was taken to a telephone exchange where connections could be made directly to the telephone lines. In order that the recording could be started at precisely the right moment to fit into the broadcast programme of, it was necessary for the recording engineer in the car to hear the cue which was the signal for him to lower the pick-up on the record and 'fade up' the output. This cue was either taken on another telephone line from the studio centre, or on a portable receiver tuned to the programme. In the latter case, the recording engineer would hear the announcer say: "We are now taking you over to... to hear our observer, whose commentary has been recorded earlier to-day" — or the commentator would speak directly at the microphone, starting on a signal from the engineer, to link together the various recorded items into a connected story.
For recordings made overseas, the discs would typically be played back from a short-wave transmitter and picked up again in Britain. However, when short-wave reception was poor, as it often was, the messages from overseas would have to be read-out by the announcer in the studio.
Although the equipment was normally operated from the car while stationary, recordings were made while on the move — following processions, in aeroplanes in the air, in express trains, at sea, and even in a submarine diving.
Recording cars were based at many different points in Great Britain and in the Middle East. Correspondents would be accompanied by an engineer who would operate the equipment. During the months when it seemed that Britain itself might be invaded the BBC had appointed war correspondents and recording engineers in all its regions; and had equipped them with transport and recording gear and with secret lists of transmitting stations and telephone lines, so that if the Germans had attempted to land there would be some chance of receiving true accounts of what had happened.
The Scottish Recording Unit played a very important role during the Second World War. In the course of a tour during August 1944, the car travelled from Glasgow up to the Highlands, via Glencoe, Ballachulish, Fort William, Inverness, and on to Tain, then struck back along Loch Ness to Kyle of Lochalsh on the western mainland, where it was shipped to the Island of Lewis. Recordings were made all along the route. In the following month the recording car was shipped to the Orkney Islands for the recording of Navy Mixture and other programmes. There was yet another visit to the Island of Lewis in December, when gear and personnel made a perilous and hazardous journey by air, on a war news assignment.
The midget recorder was designed by the BBC Research Department for recording live action on the war front in places inaccessible to the Type C Recorder. The intention was that it could be carried and operated by one man — the War Correspondent. Weighing 42 pounds, no external batteries were needed, but the quality of reproduction was better than many other heavier types of portable recording apparatus.
Previous experience has shown that a man can normally carry 35 lbs. with reasonable ease for moderate distances, but that considerable difficulty is experienced in carrying 50 lbs. for even short distances under active service conditions. An attempt was therefore made to restrict the total weight of the equipment to about 40 lbs.
- BBC Handbook 1941, 103.
- 'Archie P. Lee Remembers', Radio Times (Scotland Edition), Issue 3215, 27 June 1985, 66.
- BBC Handbook 1940, 17.
- BBC Handbook 1941, 103–108.
- BBC Handbook 1943, 101.
- BBC Handbook 1943, 59.
- BBC Year Book 1945, 32.
- BBC Year Book 1945, 78–9.
- 'The Design of the BBC Midget portable disc recorder', BBC Research Department, 10 November 1944.