What was "Mandrel"?

Short answer

"Mandrel" was the codename for a jammer developed at the British Telecommunications Research Establishment and deployed against the Freya and Würzburg radars by aircraft of 515 Squadron and 100 Group. In the US it was built as the AN/APT-3. Freya was an early warning radar.

Published: November 5, 2026 · Updated: November 5, 2026 · Edited by Above Ten Thousand · Editorial policy

Boulton Paul Defiant Mk I in flight

A codenamed jammer

"Mandrel" was the codename for a jammer developed at the Telecommunications Research Establishment (TRE) and deployed against the Freya and Würzburg radars, used by aircraft of 515 Squadron and 100 Group. The Freya it targeted was an early warning radar. The equipment was also built in the United States under the designation AN/APT-3.

The squadron that carried it

515 Squadron was formed from the Defiant Flight, also known as the Special Duties Flight, an electronic countermeasures unit equipped with the Boulton Paul Defiant Mk.II, at RAF Northolt on 1 October 1942, moving that same month to RAF Heston. Assigned to 11 Group, the squadron carried out radar-jamming missions with the Moonshine and Mandrel equipment.

Mandrel and Moonshine

Moonshine was the codename for the ARI TR1427 (Airborne Radio Installation Transmitter Receiver), a British airborne jammer and simulator, also developed at TRE, fitted to the 20 modified Boulton Paul Defiants of 515 Squadron to defeat the Freya radar.