Can your microwave really thwart car thieves?

Aug 12th '22

You might have seen recent headlines about the president of the AA choosing to keep his car keys inside his microwave oven after one of his family’s cars was stolen from their driveway.


And his microwave isn’t the only line of defence used by Edmund King to foil would-be thieves. He claimed he keeps his car keys inside a Faraday pouch (we’ll explain what this is later!), which sits inside a metal box, which is in turn stored in the microwave.


  • But why would he want to do this?

It’s all down to one of the modern-day methods used by thieves to steal cars, taking advantage of the keyless fobs that are used by many car manufacturers and models.


These keyless fobs use radio frequencies to communicate with your car, allowing it to unlock and start it when you have it in your possession. Sadly for car owners, thieves are sometimes able to use bits of tech that capture and amplify these frequencies in a way that helps them to gain access to your car.


And if they can get near enough to the fob, for example by lurking close to your home or in your driveway, they can do this while it is inside your house – where you might think it’s safe.


The rogue technology does this by extending the range of the fob, allowing a transmitter used by the thieves to mimic your fob, unlocking your car and allowing it to be started – this is because lots of car models now use a keyless ignition, which don’t need a key to be inserted in order to start the car.


Once the nearby thieves have unlocked and started your car, it’s in their control and it might be the last time you see it.


  • Foiling the thieves

This is why some people keep their car key fob inside a Faraday pouch or bag. In simple terms, this is a fabric container that also contains some metal – such as copper – in its construction which blocks some or all of the radio waves that it uses to operate. That means a car key fob, for example, won’t work from inside the pouch.


This then means car thieves can’t use their rogue technology to take advantage of the fob’s frequency to gain access to a car.


Faraday pouches can be bought from a range of retailers for as little as a few pounds, and many car owners believe they’re a good way of protecting themselves from keyless car thefts.


But if Edmund King uses a Faraday pouch, why would he feel the need to supplement this by putting the pouch inside his microwave?


Well, a microwave provides protection for your car fob in a broadly similar way to a Faraday pouch.


Your microwave oven uses very high-power radio waves to heat water molecules in food, cooking it in a much shorter time than other forms of cooking.


We wouldn’t necessarily want these waves bouncing round our kitchens – so to make sure they’re used efficiently and targeted at our ready meals or jacket potatoes, microwave ovens are built using materials that electromagnetic waves can’t pass through, so they can’t escape the oven.


It’s this construction that helps a microwave oven to behave in the same way as a Faraday pouch, and potentially offer an extra level of protection. But how effective and worthwhile is it?


No Faraday pouch is 100% perfect, which means some radio waves may still get through, although at a much weaker level. Putting the pouch inside a microwave oven means radio waves would have to get through two barriers and the signals would be even weaker on the outside. The effect of this is to reduce the distance over which the fob would operate – to an impossibly small distance from the car or a thief’s equipment. And this in turn means thieves can’t be successful if they’re trying to capture the frequency of your key fob from somewhere near your home.


So, in short, Edmund King is on to a good thing with his microwave security measure.


However, if you’re tempted to use your microwave oven as an extra barrier for the car thieves – remember to tell everyone in your home. The last thing you want is for your car keys to be cooked alongside your dinner…


Source: Office of Communications (Ofcom)