Science Questions

Why does a mobile phone interfere with the radio or stereo?

Sun, 6th Apr 2008

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Question

Brian Randall asked:

Iíve got a question regarding mobile phone interference. If my mobile is in close proximity to, say, my stereo it interferes with it. It causes that beep-be-beep beep-be-beep noise. Why doesnít my mobile phone interfere with itself then, when itís playing music for example?

Answer

The reason why your phone interferes with your stereo is your stereo is actually a very inefficient radio. Itíll convert radio signals into sound signals. This used to happen when I was a kid. I lived right at the bottom of a hill of a really powerful medium wave transmitter. Because the signal was so powerful all sorts of things that wouldnít act as radios will suddenly start behaving like ones. I could pick up Radio 5 on my computer and all sorts of things like that. So basically itís picking up the mobile phone which is transmitting digital data which makes that horrible de-beep and chghghghgh type noises. You can also design the radio inside the phone so that itís designed to ignore the wavelengths which itís transmitting on. So anything about 2 or 3 GHz it will completely ignore them.

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