TV signals 'to replace radars' in aircraft tracking

Air traffic controller Nats is looking in to using TV signals to track aircraft as a cheaper alternative to radar.

During the trials, researchers said they were able to track 30 planes simultaneously flying at altitudes of up to 11,000ft by monitoring how aircraft interfered with TV signals. Traditionally TV signals use different chunks of the radio spectrum to radar, but both bounce off solid objects.  

The new system costs less, suffers less interference from wind farms and could be more accurate than radar, according to the researchers. However, they stressed that more work has to be done.

“Questions around resilience and service standards need to be answered and we’d need to explore formal agreements with the broadcasters, but this is very exciting and we’ll be looking to further develop the concept over the next five years,” said Nats engineer Nick Young.

The study involved a TV signal broadcast by a transmitter at Crystal Palace in London and specialist receivers were used to measure the directions of the signal reflected by the aircraft. They studied the time difference it took to be received compared to the unobstructed TV signal to then deduce the various planes’ locations.

“Specialist receivers then measure the directions of the signal echoes and the time taken for them to arrive in order to calculate the aircraft’s location,” said Young.

Another trial was conducted in Liverpool that suggested the signals were less susceptible to the interference wind turbines cause to traditional radar – a problem that has affected the renewables industry in recent years.

Radars can pick up the rotating blades of a wind turbine as they enter a specific velocity range – a typical wind farm can have turbines moving at aircraft speed, so radars may detect it, thinking it’s an aircraft.

Reductions in cost could be a considerable advantage, Young said, and it would also free up radio spectrum for other uses. It is not an entirely new idea: it was previously trialled in 1935 by radio innovator Sir Robert Watson-Watt.

The research was been carried out with the defence firm Thales UK and Roke Manor over the past two years.

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