Why does Wi-Fi use the same frequency as microwave ovens?

When you start the microwave, do you lose the Wi-Fi signal on the nearby device? Wi-Fi and microwave ovens operate on the same frequency, which may cause interference. But why? And if so, why isn’t Wi-Fi cooking for you?

Microwave ovens and Wi-Fi use the same unlicensed spectrum

In 1947, the International Telecommunication Union established the ISM bands, abbreviated to Industrial, Scientific and Medical. The goal was to determine which devices could operate on certain radio frequency bands so that they would not interfere with other radio services.

The ITM has identified the 2.4 GHz band as unlicensed spectrum specifically for microwave ovens. This strip has three compelling properties: it does not require much power to broadcast, it is easy to maintain, and with relatively less power it can heat food. All of this lowered the cost and entry barrier for consumers.

As the name ISM suggests, the original intent was to be used only in devices that did not provide connectivity. In later years, the prospect of unlicensed spectrum has been exploited beyond its original purpose such as cordless phones, walkie-talkies and, more recently, Wi-Fi. The 2.4 GHz band was ideal with its low implementation cost, lower power requirements, and decent distance capabilities.

Microwaves are not a Faraday cage; They leak

Anything that operates on ISM bands must be designed to be non-portable to avoid interference, and Wi-Fi devices do have algorithms specifically for this purpose. However, the microwave is powerful enough to jam any nearby Wi-Fi signals.

Microwave ovens have shielding to prevent this, but they are not a perfect Faraday cage. The very nature of the mesh window on the door prevents this. It’s not uncommon for a microwave to leak — just look at one that hasn’t been cleaned in a while to see it. You will most likely see dirt and grease on the outside that could only come from food on the inside. If it can pass solid particles, then it can also pass radio waves.

Microwave ovens and Wi-Fi devices use a frequency similar enough that one can interfere with the other. Of course, your Wi-Fi won’t do anything noticeable to a microwave, partly because of its shielding, and partly because all it’s trying to do is heat your food.

No wifi can’t cook you

Wi-Fi and microwaves use an extremely similar radio frequency, but there are two major differences: focus and power. The Wi-Fi router sends its signal omnidirectionally. That is, it sends it in every direction in a circle as far as possible. A microwave, on the other hand, sends its signal in one direction, roughly toward the center of the oven. This signal continues until it reaches the wall, bounces off and returns (at a slightly different angle). This is not an ideal system due to the nature of radio waves and therefore every microwave has hot spots and cold spots. This is why microwave ovens have rotating plates.

Microwaves also consume more power than a Wi-Fi router; typically they generate 1000 watts of power. Conversely, a standard Wi-Fi router generates about 100 milliwatts (or 0.1 watts) of power. You will have to increase the power output of your Wi-Fi router by about 10,000 times and limit the beam to be able to cook anything.

You may not need a new microwave

If you see interference problems, you don’t need to replace your microwave; chances are the leak is tiny and not harmful to you. Wi-Fi is much more sensitive and doesn’t take long to resolve. Instead of replacing the microwave, you can move it. Alternatively, buy a new Wi-Fi router that operates on the 5GHz band. You will not only avoid interference from the microwave oven, but also prevent interference from your neighbors.

Image credit: Sergey91988 /Shutterstock.com