Radar dish Radar-dish antenna, Kennedy Space Center, Florida. © NASA

By Professor Eric Grove
Professor of Naval History, University of Salford

What is radar?

Radar uses reflected radio waves to detect objects and indicate their bearing, distance, altitude and speed. Because it uses radio waves radar can operate in any weather conditions.

How does it work?

A radar system consists of a transmitter and a receiver. When the waves sent out by the transmitter hit the object some of them are reflected back to the receiver. The received energy is very weak but it can be amplified to give an indication on a cathode ray tube. The amplification process means that radar has a much longer range than sound or visible light.

What do we use it for?

The first use of radar was air defence, but it was soon also being used to detect objects at sea, like surfaced submarines. It also made gunnery more accurate; radar sets were even installed in shells to make them explode as they passed or approached a target. Radar is still of great importance in military applications today - advanced systems are able to produce photographic quality pictures of scenes blacked out to other sensors. Besides military employment radar is also used to help forecast the weather, it is used by police to enforce speed restrictions and it has proven crucial in civilian air and sea travel - preventing collisions and generally helping navigation.

Can radar interfere with television signals?

In theory yes - but the technology of radar developed in parallel with that of television; Britain’s radar air defence system, the first in the world, had to transmit at a frequency that would not interfere with Britain’s pioneer TV broadcasts!