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Question 1567: My microwave oven is interfering with my radio reception. Is it safe?

Our microwave oven is only 2 years old. Recently, we have noticed that when the microwave oven is being used and our kitchen radio is on, the radio has a lot of static. Is this an indication of a leak? Other than interfering with our radio, the oven appears to be working fine. RN, Bloomington, Illinois
Because the oven's microwave frequency is more than 20 times higher than anything a normal radio receives, I'd be surprised if the radio would notice even a pretty severe microwave leak. What you describe doesn't sound like it's caused by the microwaves. It sounds like it's caused by an electrical problem in the oven's high-voltage power supply.

An older oven would have used a heavy transformer, a capacitor, and a diode to convert ordinary household AC power to high-voltage DC power for its magnetron microwave tube. But since your oven was made recently, it probably uses a switching power supply to produce that high voltage. That supply contains a much more sophisticated electronic switching system to convert household AC power to high-voltage DC power. The new approach is cheaper and lighter, so it's taking over in microwave ovens. Just because it's more sophisticated, however, doesn't mean it's more reliable.

My guess is that the unit in your oven has a problem. If it has an intermittent contact in it or if there is a conducting path that is sparking somewhere in the power supply or in the unit as whole, they'll be randomly fluctuating currents present in the oven and those current fluctuations will produce radio waves. A sparking wire or carbonized patch on the power supply will start and stop the flow of current erratically and that can easily cause interference on the AM band. Ordinary AM radio is very susceptible to radio-frequency interference at around 1 MHz and sparking stuff tends to produce such radio waves. A car with a bad ignition system, a lawn mower, and a thunderstorm all interfere beautifully with AM reception. And I suspect that you've got a similar electrical problem in your oven. I doubt that your oven is a microwave hazard, but you should probably have a repair person to take a look at it. It shouldn't have anything sparking inside it.


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