Microwave ovens spray electromagnetic radiation, typically at about 1000 watts at a frequency 2450 MHz. In addition, because microwave ovens are trying to do cooking, not wireless communication, they tend to pretty much indiscriminately spray microwaves with as much power as allowed. Hence, while the ovens are massively shielded to prevent the 1000 watts of power from escaping, they no doubt leak, mostly around the door. The FCC requires that microwave ovens “leak” no more than 2 milliwatts (+3 dBm) at 1 inch from the door. Now I don’t actually know who decided to put the microwave oven at 2450 MHz, but they obviously weren’t thinking about WiFi back then. The figure below illustrates the position microwave ovens as they relate to 802.11bg channels.
So, what is the impact on WiFi? Well, like most things it depends, assuming you don’t do something really dumb like putting your WiFi access point on top of your microwave, you probably won’t notice any catastrophic effects. From the figure, you can note that all the WiFi channels overlap and that the microwave oven falls squarely on top of channels 7 to 11 and no doubt bleed over into adjacent channels beyond 7 and 11 as well – but don’t panic. In the world of WiFi, a microwave oven will just look like noise, so as long as you’re not too close to the microwave. This begs the question – what is too close?
In my house, the favorite place to use a WiFi enabled laptop is the kitchen counter and it typically involves snacking at the same time, which may mean using the microwave. I don’t know whether or not I’m “typical,” but it works for me. In any event, this puts my laptop about 6 feet from the microwave and 24 feet from my WiFi Access Point. So using this environment, what is the microwave’s impact on WiFi performance, using different WiFi channels? Since I like to be away from the norm, I’ve always tended to put my WiFi network on Channel 1. I do this because the default channel is 6 and like to be as far away, channel wise, from most of the other networks in my neighborhood. However, it also has the benefit of being far away from the microwave frequency as well. On channel 1, running a simple file transfer test from a server in my house, I notice a 21% reduction in real payload data throughput from 14.4 to 11.3 Mbps. When I move the WiFi access point to channel 9, the reduction is 51% to 7.1 Mbps. As expected, results were not quite as bad on channels 6 and 11.
Now I know many of you may be unhappy with these results. Just remember, that it still works, throughput is not awful – you probably wouldn’t notice on an internet download and microwaves tend not to be on for very long. Of course, if you really aren’t happy, make sure that you have your WiFi channel set to channel 1 and to sit on the couch, farther away from the microwave.