London Calling... 2LO Calling

The set of equipment which transmitted the BBC’s first ever programme, in 1922, is now part of the Science Museum’s collections. Find out here about its eventful history and preservation.

2LO

At first, valve radio sets with a loudspeaker were extremely expensive. Home construction reduced the costs somewhat, but most listeners started with a simpler and cheaper receiver called a crystal set, and listened through headphones.

 Crystal sets consisted of a tuned circuit and a crystal detector, and had no batteries as the power delivered to their headphones all came from the transmitter. Most designs used a wire ‘cat’s whisker’ touching a favourable spot on the crystal at just the right pressure. The slightest vibration, such as slamming a nearby door, could cause listeners to lose the programme altogether, until they carefully adjusted the set to bring it back.

Well-off listeners in 1923 could afford to buy a valve set, such as the Burndept Ultra IV, which cost £75 at 1923 prices. Learning to operate such equipment could be a daunting prospect (rather like buying a new home computer today), involving several pages of quite complex instructions to absorb.

‘Straight’ radio sets probably needed a garden aerial, but paradoxically sets with a ‘superheterodyne’ circuit had to have a less efficient indoor frame aerial. This was because such sets used an oscillator which was capable of radiating interference if the incoming signal was too strong. This unwitting transmission of interference (or ‘oscillation’) was a big problem for several years, and was taken very seriously by the Post Office - offenders ran the risk of having their licence withdrawn. Eventually better circuit design largely eliminated it.