1935

Daventry Experiment

The Daventry experiment detects an aircraft by reflected radio waves

The transmitter was a BBC station already broadcasting from Daventry. The receiver had been built to study the ionosphere, then carried into a field to look for a bomber.

26 February 1935: a bomber flies through a borrowed beam

On 26 February 1935, Robert Watson-Watt and Arnold Wilkins staged a feasibility demonstration in a field near Weedon, Northamptonshire, using transmissions from the BBC Empire short-wave station at Daventry — 10 kilowatts at a wavelength of 49 metres.

An RAF Handley Page Heyford bomber flew repeatedly through the beam at a reported 5,000 feet while the ground team watched a cathode-ray display for fluctuations caused by radio energy reflected from the aircraft.

The display responded while the bomber was approximately eight miles away.

Repurposed apparatus, not a radar set

The receiver had originally been used by the National Physical Laboratory for ionospheric measurements. The demonstration repurposed existing apparatus and a broadcasting transmitter rather than employing a completed operational radar set.

It revealed the aircraft's presence through interference between the direct and reflected continuous-wave signals. It did not yet measure a target's range and bearing the way the later pulsed system would.

The acronym "radar" came later; the British work was then described as radio detection, or RDF.

What the Air Ministry took away

The Air Ministry had rejected a radio "death ray" as impractical. Watson-Watt then submitted a 12 February memorandum proposing aircraft detection by reflected radio waves, and officials required a convincing demonstration before committing to development.

A. P. Rowe attended for the Committee for the Scientific Survey of Air Defence and was convinced that an aircraft could be detected by reflected radio signals. Secret government development work followed, moving to Orfordness and later Bawdsey, where pulsed aircraft-detection systems were produced.

Scholarly histories describe radar as a case of simultaneous invention across several countries, and distinguish Daventry as a decisive British feasibility demonstration rather than the invention of radar.

Sources

Researched 23 Aug 2026 8 sources 2 audit passes Date corrected

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date corrected. The research places this at 1935-02-26.