Broadcasting in Britain: The Pre-War Years 1932-1939 

9 December 2022 tbs.pm/76324

 

Cover of Broadcasting in Britain

From ‘Broadcasting in Britain’, published in 1972 by HMSO

Throughout this period, building up the network of transmitters for the ‘National’ and ‘Regional’ programmes was a major task; by 1939, they achieved coverage of 94% and 87% respectively. The short-wave station at Daventry was expanded from two transmitters to eight, and a modest start was made in foreign-language broadcasting.

In studios, the BBC-Marconi ribbon microphone was generally adopted. Its excellent frequency response had the further merit of being the same for sounds from all horizontal directions.

The ‘Blattnerphone’ recording machine was taken over by the Marconi company and re-appeared, much refined, as the ‘Marconi-Stille’ recorder, but by 1935 its position was challenged by the development of a method of disc recording that allowed immediate playback; conventional gramophone recording involved a delay for processing. The new method used a metal disc coated with a layer of cellulose lacquer, in which the groove was cut; it was due to Cecil Watts, a musician with a talent for engineering, who in the early 1930s established the Marguerite Sound Studios (MSS) to exploit it. The BBC borrowed an MSS experimental recorder for tests in October 1933, and over the next year or two collaborated with Watts in improving the design. In June 1935, the BBC’s first disc recording ‘channel’ (two recorders) was installed at its music studios at Maida Vale, and by the end of 1936 two further channels had been added. Watts machines were also used for the BBC’s first mobile recording unit, introduced in 1935. This was housed in a large van, and gathered material for ‘feature’ programmes. Its two successors, which took the road in 1936, were even bigger, each containing a small studio. Built on bus chassis, they were legally restricted to 20 mph, and were unable to negotiate the roads in the remote regions that they had originally been intended to explore.

For ‘news’ applications, technical facilities obviously had to give way to mobility, and by 1938 portable equipment had been designed that could be carried on the rear seat of a large car; two sets of this equipment were in service at the outbreak of war.

From 1936, the BBC also used another method of recording which achieved better reproduction than was obtainable from tape or disc. This ‘Philips-Miller’ system (developed by Philips, Eindhoven, from patents by an American, Dr J A Miller) ingeniously combined disc and sound-on-film techniques. The recording medium was a clear film, 7mm wide, covered on its top side with a thin, opaque skin, It ran below a cutting stylus which was vibrated vertically by the sound signal. Because its cutting edge was shaped like a very shallow ‘V’ across the film, the vibrating stylus cut away a varying width of opaque skin. The resulting ‘variable area’ recording was ready for immediate playback by conventional optical means. Two channels of Philips-Miller equipment were in service from November 1938.

 

A microphone, shown whole and in parts. Inset, a 1960s microphone

The BBC-Marconi ribbon microphone (1934) and an AKG capacitor microphone (1969): The earlier microphone, despite its greater size, is much less complex than the later one, which includes an amplifier employing a field-effect transistor

 

Receivers

Between about 1927 and 1934, radio receivers developed rapidly. The battery-powered receiver, connected to an outdoor aerial and tuned in by manipulating two tuning controls and a reaction control, gave way to the all-mains superhet, with built-in moving-coil loudspeaker, automatic volume control and single-knob tuning. Its sensitivity enabled a fewer feet of wire within the room to serve as an aerial. This form of receiver was to undergo little basic change in the next twenty years.

The ‘superhet’ [originally ‘supersonic heterodyne’, then ‘superheterodyne’] principle has remained the basis of all subsequent receivers. It came into use because the so-called ‘straight’ set, in which the tuning knob had to vary all the tuned circuits simultaneously, could not readily achieve the selectivity demanded by the growing congestion of the broadcast wavebands; it was difficult to keep all the circuits in step as the receiver was tuned, and their performance inevitably varied across the waveband.

In a superhet, the signal from the aerial is ‘mixed’ with the output of a tunable oscillator, to form a signal at their ‘difference’ frequency. All the circuits that follow are permanently tuned to accept only one narrow range of ‘difference’ frequencies centred on, say, 0.5 MHz. Thus, if the oscillator frequency is 1.8 MHz, a station at 1.3 MHz is heard. Rotating the tuning knob changes the oscillator frequency to, say, 1.9 MHz, and brings in a station at 1.4 MHz.

 

A 1930s radio

Philips ‘Superinductance’ receiver, 1933: By good design, this ‘straight’ set was given a performance equalling that of contemporary ‘superhets’

 

This technique enables the tuned circuits that give the receiver its selectivity to be designed for optimum performance at a single frequency, and to be precisely adjusted, once and for all, during manufacture.

In the years immediately before the war, a short-wave band became an essential selling point on all but the cheapest receivers, though fewer British listeners made much use of it; they tended to confine their listening to the BBC, except on Sundays, when many chose the lighter fare offered by Radio Luxemburg [sic] or Radio Normandy. Under these circumstances, a more useful facility was push-button tuning, which was also widely installed. Over this period, the technical sophistication, stylish appearance and keen value of mass-produced receivers undermined home construction, and only a dedicated minority continued to build their own receivers.

Television

In February 1937 the television service adopted the 405-line standard exclusively, and in May the first television outside broadcast took place, when three cameras showed the Coronation procession as it passed Hyde Park Corner. Though the ‘Emitron’ camera tubes produced acceptable pictures despite the dull, rainy weather, they were not really sensitive enough for outside broadcasting, and later in the year were replaced by ‘Super Emitron’ tubes, about five times more sensitive. Outside broadcasts from Central London made use of a special balanced-pair cable, laid by the Post Office, to convey the vision signals to Alexandra Palace. It was found that, with suitable correction, signals could be sent through a mile or two of ordinary telephone circuit before reaching the special cable, thus extending its effective range.

 

View down into a television studio dressed as a domestic front room

The ‘Marconi-EMI’ studio at Alexandra Palace, 1936: The scope of early television programmes was restricted by cramped and poorly equipped studios

 

For more distant outside broadcasts the signal was sent back to Alexandra Palace by radio, using a 1 kW mobile transmitter operating at 64 MHz, and an aerial mounted on a fire-escape ladder.

By the end of the year the technical soundness of the system was established beyond doubt. The Emitron and Super-Emitron cameras produced excellent pictures, and the range of the transmitter exceeded expectations. The radio industry had risen to the challenge of incorporating a totally unfamiliar technology into receivers that the general public could handle. Nevertheless, public response was disappointing. Though 2,000 people a day had visited an ambitious television exhibition mounted at the Science Museum, fewer than 2,000 receivers had been sold.

 

A 'flip top' television receiver

Television receiver, 1938: Though the size of the screen was only 12 inches (305 mm), the tube was so long that it had to be mounted vertically and viewed by means of a mirror in the lid

 

One reason lay in the inadequate hours of transmission. Until the old ‘Baird’ studio was re-commissioned for 405-line operation late in 1938, there was only one studio, and it was possible to produce only two hours of material each day (from 3 to 4 and from 9 to 10), including a proportion of ‘repeats’; there were no Sunday programmes until April 1938. Sales of receivers were also restricted by their price, which was out of most people’s reach; the typical set of 1937 was a luxury model with a 12-inch (305 mm) screen and cost half as much as a small car. Finally, it seems likely that, with such spectacular advances so recently achieved, many people delayed buying receivers in the hope that better models would soon be available, or the fear that changes in transmission standards would make current models obsolete.

In February 1938 the Postmaster General announced that transmission standards would remain substantially unaltered for at least three years. Later that year, manufacturers considerably reduced the average price of a receiver by introducing models with smaller tubes, ranging from 9 in (229 mm) to 5 in (127 mm) in diameter. Sales improved, and by September 1939, when war closed the service down, about 20,000 sets were in use.

 

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