Burndept 'Ethodyne' superheterodyne radio receiver, 1925.
© Science Museum / Science & Society Picture Library
Radio receiver with Amplion loudspeaker with wooden horn of 1925. In 1917, Edward Howard Armstrong (1890-1954) developed the superheterodyne electronic circuit, which significantly improved the sensitivity and selectivity of radio receivers over a wide range of frequencies, making amplifier tuning unnecessary. This made the task of tuning the radio receiver to different stations much more simple and straightforward. 'Superhet' radios had to use an indoor frame aerial because such sets used an oscillator which was capable of radiating interference if the incoming signal was too strong. This was a big problem for several years, before better circuit design largely eliminated it. Burndept was one of the first companies to produce radios in Britain, beginning in the early 1920s.