RAAF 227 Radar Bunker
In 1942, approval was granted for the establishment of radar equipment at Yanchep. The site became fully operational on 27 October 1943. The 227 Radar Unit was formed in August 1943 and was responsible for the operation of the radar, and reporting to the Western Australian Air Defence Headquarters. The unit was a combination of Royal Australian Air Force (RAAF) and Women's Auxiliary Australian Air Force (WAAAF) personnel.
Two concrete huts, 40 metres apart, housed the radar equipment. The southern hut contained the transmitter and the northern hut the receiver. The daily unit operational occurrence reports do not record any actual tracking of enemy aircraft although the unit had the distinction of being responsible for the first genuine air raid alarm for the city of Perth. Just after midday on 10 March 1944, radar operators observed multiple aircraft blips, some 150 miles to the north of Perth. Authorities decided that they could not wait any longer for positive confirmation of enemy activity and a full scale air raid alarm was sounded throughout the city of Perth. No aircraft were spotted, and a later investigation suggested it had been the result of enemy jamming.
- "State Heritage Register" (PDF). 2002. Retrieved 2013-01-20.