How to prevent microwave cooking from slowing down your entire home's WiFi, using 802.11n 5GHz WiFi

Posted by Paul Braren on Oct 15 2013 (updated on Mar 11 2017) in
  • HowTo
  • iPad
  • iPhone
  • Network
  • microwave-casts-wifi-shadow

    Tonight, I was listening to This Week In Computer Hardware 195, where 5 minutes in, hosts Patrick Norton and Ryan Shrout have an interesting discussion about the wireless interference issue with USB 3.0, especially when external USB 3.0 drives are in use. It's all described with scientific precision in this excellent Intel article:
    USB 3.0* Radio Frequency Interference Impact on 2.4 GHz Wireless Devices White Paper, April 2012.

    The TWiCH hosts go on to explain their own flaky wireless mouse stories. This reminded me of the interesting effects my kitchen's microwave oven has on my 2006 vintage Microsoft Bluetooth Wireless Laser Mouse 8000. When my mouse gets a little jumpy, I know somebody is cooking in the kitchen below me.

    So, where am I going with this? Well, I've also noticed the far bigger effect microwave cooking has on my family's wireless surfing. WiFi access is nearly obliterated. Only when microwaving something. A huge hit in speed is noticed, not just in the kitchen, but in the adjoining rooms room too, and even upstairs. Definitely an  annoyance if I'm on a Facetime call, for example. One reason my work computers are all wired, full-time.

    These microwave interference effects have been noted for years, back in 2003 here for example, which goes on to explain why Channel 9 is the worst 2.4GHz WiFi channel to pick. I didn't find changing channels helped me much.

    So, what to do about this microwave interference?

    Well, our family recently made the move to iPhone 5 cellphones, and their new WiFi capabilities, listed on Apple's specifications page as 802.11a/b/g/n Wi-Fi (802.11n 2.4GHz and 5GHz). That 5GHz compatibility really caught my attention. Why? Well, I already own a dual-band Cisco Linksys E4200 WiFi router, described on TinkerTry here, and at Cisco here. And I already have both 2.4GHz and 5GHz frequencies active.


    Yet, I wasn't really using the 5GHz frequency for anything. So once I got iPhone 5 in the house, we tried good old SpeedTest.

    The positive effect was big. While moving channels on 2.4GHz didn't help, moving frequencies, from the 2.4GHz to 5GHz, helped a great deal. Instantly resolved the severe speed slowdowns. Throughout the house. And the result wasn't at all subtle, as shown in the video below.

    Try this test out for yourself! Your results will likely be very similar on newer Android devices that are 5GHz capable, such as the Android Galaxy S III. Same goes for Windows 8 Phone devices, like the HTC 8X. And of course, newer laptops, with a built-in 802.11n 5GHz antenna.

    Don't forget to "forget" the 2.4GHz WiFi connection on your cellphone, so when you return back to your home, you'll be sure it's connected only to the 5GHz frequency.

    Please comment below, to let us know your thoughts, or how you do with your own tests.

    802.11n 2.4GHz, with microwave off
    802.11n 2.4GHz, with microwave running during download portion of test [seen in video]
    802.11n 5GHz, with microwave running throughout the test [seen in video]

    While recording the video (with another iPhone 5), I didn't have any other big bandwidth intensive tasks going on on my entire network, wired or wireless. I do have a DECT headset, that wasn't in use (cradled), but doesn't seem to affect speed tests at all even when in use, since it's 1.9GHz. You'll also notice in the video that my home's WiFi is the only one picked up in this room, so neighbor interference is minimal. FYI, I didn't have luck with messing with Channel Width or Channel Number on the 2.4GHz frequency: the microwave has always had an effect on wireless speed in my household, for roughly a decade now, even back to the 802.11b days.

    Additional Sources:

    wikiHow - to do Anything, How to Check a Microwave for Leaks, July 17, 2012

    SmallNetBuilder's How To Fix Your Wireless Network - Part 1 - RF Basics, Interference, OCT 2007, CRAIG ELLISON

    Cisco's 20 Myths of Wi-Fi Interference, 2007, here's an excerpt:

    For example, microwave ovens emit interference on a 50 percent duty cycle (as they cycle on and off with the 60-Hz AC power). This means that a microwave oven operating at the same frequency as one of your 802.11 access points can reduce the effective throughput and capacity of your access by 50 percent. So, if your access point was designed to achieve 24 Mbps, it may now be reduced to 12 Mbps in the vicinity of the microwave when it operates. If your only application on the WLAN is convenience data networking (for example, Web surfing), this loss of throughput may not be immediately obvious. But as you add capacity and latency-sensitive applications such as voice over Wi-Fi your network, controlling the impact of interference will become a critical issue.

    So yes, perhaps the ~7 year age and potential RF "leakiness" of my microwave factor in here, but my door seals are in great shape. Nevertheless, I'll be doing further tests. And it'd be helpful if you'd share your experiences below as well. Easy, no login/password required!

    Jan 14 2013 Update

    Because moving from 802.11 2.4GHz up to 5GHz involves an increase in frequency, it can result in a decrease in range in your home. I'd suggest keeping the router on the second level of 2 story homes, and walking around the home and performing speed tests, to determine if you have adequate coverage, even when not cooking.

    Also be aware that newer cordless phones use the DECT 6.0 standard, which moves you away from the crowded 2.4GHz band. I happen to own a non-DECT, 5.8GHz cordless phone system, Uniden's TRU8866, and haven't experienced any issues with interference. In other words, any cordless phone calls I have going on don't seem to affect my WiFi speeds.

    See also:

    Sep 19 2013 Update

    My Bluetooth Microsoft Mouse is situated about 8" from my cell phone stand, seen here. If I go with the 2.4GHz WiFi, my mouse gets jumpy during larger downloads on the iPhone. If I go over to 5GHz, no issue with the mouse, at all.

    Oct 15 2013 Update

    The answer to this problem for our household's Yoga 13 was simple in the end, even though it can only do 2.4GHz. You see, at some point, our Linksys E4200 router had been set to auto for the 2.4GHz WiFi. This meant at some point we wound up on Channel 11, known to be a problem for microwave interferce. Read more about it in the old but still very relevant article here. So I moved our Linksys E4200 router 2.4GHz WiFi to channel 1, and speed tests now only ~30% degraded versus no microwave running (versus 100% degraded before the channel change). This is a good outcome.

    Mar 11 2017 Update

    Eventually, I found much faster speeds across all the living spaces in my family's home by going mesh, with wired backhauls. No more microwave interference. I've been with eero now for about 7 months now, and it's been mostly very good, see: