During her World War 2 service, Diamantina carried two radar rigs, a Type 271 surface search radar in the upper compartment and a Type 286Q air search radar in the lower compartment. Both gave early warning to the crew of approaching (enemy) ships/aircraft while the surface search radar could also assist with navigation through island waters.
The Type 271 antenna was located on the roof of the compartment in an enclosed cylinder while the air search antenna was located at the top of the mast. Signals from the antenna were fed to receivers in these compartments. Here operators interpreted the “blips” on the screens and were able to determine the range to the target. This information was used by the Gunnery Officer to prepare the guns for action.
For those interested in vintage radar systems, step inside the 271 compartment and take a seat. The small, circular display, known as an A-scope, shows a 360-degree arc around the ship. It gives a clearer graphic description of the radar signals. And like the men in the Asdic office, the radar operators could immediately inform the captain if they picked up anything ominous on their screen.
As the aerial was manually rotated, the operator would obtain the bearing of the contact by checking the direction the aerial was pointing. The large circular display, above, is the Plan Position Indicator that has the ship in the centre.
The development of the Type 271 radar has been described as the most significant technological achievement of the Second World War. Its compact cavity magnetron (a type of radio valve) drastically reduced the size of radar sets and produced centimetre wavelength radar beams that gave sufficient definition to detect submarines. The set was small enough to be fitted in the convoy escorts.
The Type 271 could detect a destroyer at 14 km, a surfaced submarine at 8 km and even a submarine periscope at 3 km. Where the dark of night had once given cover to an attacking submarine, radar-fitted convoy escorts could now detect hostile vessels at any time of day or night and counter-attack, often before the submarine could fire its torpedoes.
The radar sets were manned 24 hours a day while the ship was at sea.