Radio theory on car locks

Headshot of Pierra Willix
Pierra WillixBusselton Dunsborough Times
Email Pierra Willix
Professor Steven Tingay
Camera IconProfessor Steven Tingay Credit: The West Australian

Reports of cars’ central locking systems not working throughout the Dunsborough town centre have been attributed to radio waves bouncing off each other.

After social media posts last week about residents having problems locking their cars in parking bays along Dunn Bay Road, Seymour Road and Cyrillean Way, the Times spoke to John Curtin Distinguished Professor and expert in astronomy and astrophysics Steven Tingay.

Professor Tingay said the layout of the buildings in the surrounding area could be affecting the locking systems, which use radio waves to send signals to the cars to lock.

“The radio waves bounce off all sorts of objects in the vicinity, such as your car and other cars, shopping trolleys, and all the surrounding buildings,” he said.

“So, at the location of your car, the signal that gets received is the sum of all these reflected signals adding up. If the signals add up in the wrong way, they can actually cancel each other out and the strength of the signal will not be high enough to trigger the locking mechanism.”

He said he had not heard about this particular issue before but it did not surprise him.

“It is the same issue as with Wi-Fi, mobile phone reception, and other communications systems that use radio waves,” he said.

Professor Tingay said the issue could be worse for certain cars or certain radio frequencies and would depend on both the location of the car and the person using the remote control.

“There are lots of complicated factors contributing to this effect,” he said.

“These systems are cleverly designed to be robust to these effects and work well in the vast majority of situations.”

As for how to overcome the problem- Professor Tingay suggested people having trouble locking their cars should try moving about 10m away and trying again, which changed the geometry and the signals reaching their cars.

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