When public broadcasting began in the early 1920s, the most widely available receivers were crystal sets. Crystal sets could only be listened to through earphones and required a long aerial which was usually strung us in the garden like a clothes line. Tuning was very difficult; the crystal had be touched at exactly the right spot with a piece of metal known as a “cat’s whisker”. Crystal sets were cheap and were often built by hobbyists from components or kits.
During the 1920s, radios with valve amplifiers gradually superseded crystal sets. Early radios were cumbersome with separate receivers, aerials and batteries but technical advances meant that by the early 1930s all of the components could be housed in one cabinet powered by mains electricity.The first radios were free-standing pieces of furniture.
These were superseded by mantle models. At first these, like the floor-standing radios, had wooden cabinets.
Bakelite cases came into use in the 1930s and plastics in the 1940s.
Transistors began to replace valves from the 1950s, allowing radios to much smaller and more portable.