"Consumer electronic devices are designed to be used in a certain environment and interact with electromagnetic fields," says Carnegie Mellon electrical and computer engineering professor James Hoburg. And with so many gadgets hanging around in such a narrow range of frequencies, things can get crowded. Many routers, along with all Bluetooth devices, transmit at 2.4 GHz. Wireless home phones broadcast at 900 MHz, 1.9 GHz, 2.4 GHz and 5 GHz. Cellphones, depending on the carrier, communicate at 850 MHz, 1.7 GHz and 1.9 GHz. This, a thin, patchy section of the electromagnetic spectrum below 5 GHz, is where our gadgets live. (High-school physics refresher: Wavelengths get shorter as frequency gets higher, and a 1-GHz wave measures about 12 inches.) Range, antenna size and cost requirements conspire with stringent government regulations to relegate most personal electronics to an even narrower range of frequencies.
We use only a portion of the spectrum for wireless communication, the broad swath from about 30 Hz to 300 GHz. So what is it? How can you stop it? Radio OveractiveĮlectromagnetic radiation lies behind everything from gamma rays to visible light to your kid's walkie-talkie. RFI has been an irritant throughout mankind's love affair with electronics, particularly with wireless gadgets.
RFI takes many forms, and they're all ugly: A humming microwave chokes a Wi-Fi connection a baby monitor brims with noise an audio recording made with a laptop fizzles and pops.
What you experienced, in other words, is radio-frequency interference, or RFI. That's because what you've just heard is the noisy pulse of a cellphone's transmitter, amplified by either the station's studio equipment or your car's stereo. Within moments a cellphone will ring, either in the radio studio dozens of miles away, or inside your own vehicle. The jarring interruption is as familiar as it is mysterious. No, not your favorite tune, but your least favorite sound: a bzzt-baba-bzzt-baba-bzzzzzzzt that pierces through your car-stereo speakers. Then, after a moment of pregnant silence, you hear it. After an eternity of chatter and commercials, the radio DJ is about to play the song you've been waiting for.
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