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Ask HN: Does your microwave interfere with Bluetooth? Mine does

119 points by Jeff_Brown 3y ago

I can see the Faraday cage in my microwave. It's never cooked anything outside of it. But if I put my phone on one side of it and a Bluetooth speaker on the other, running it interrupts the connection to the speaker. Sound gets through but it's choppy. Seems bad, right?

hulitu 3y ago
> Ask HN: Does your microwave interfere with Bluetooth? Mine does As far as i know you can make a complain by the FCC.
kevinherron 3y ago
Not great, not terrible.
mikewarot 3y ago
There's about 1000 watts of RF inside the microwave, it has to be attenuated to less than a few microwatts on the outside to avoid congestion, as they use the same frequency band. I'm amazed WiFi or Bluetooth ever works at all. 8) You can thank Hedy Lamar for that. Try cleaning the mating surfaces around the door thoroughly. If that doesn't work, consider replacing the microwave or relocating the speaker.
- H8crilA 3y ago
  The microwave RF emission is actually very narrowband, though the frequency drifts all the time. Bluetooth uses FHSS so it will eventually go though, unless the noise is so powerful that it saturates the receiver. I'd post a screenshot from a HackRF-produced waterfall, but I don't have a microwave :). Some wifi controllers can measure energy in the spectrum and can be used to plot a simple waterfall.
  - grepfru_it 3y ago
    >but I don't have a microwave :) Living the dream!
- NikkiA 3y ago
  If it's an old microwave replacing the door seal would be cheaper and easier.
- anotherhue 3y ago
  > You can thank Hedy Lamar for that. eh... maybe. Don't forget the microwave isn't CW so there's plenty of transmission slots available on the off cycle.
- jrockway 3y ago
  Wifi has an "interference robustness" option which is designed with microwave ovens in mind. The power output of a microwave is a sine wave, because it's powered from your AC line power, and doesn't emit energy during the zero crossings. "Interference robustness" times packet sends (and lengths) to be when the microwave is producing the least amount of power. Thus, you spend half of every 60th of a second irradiating your food, and the other half downloading videos. (Needless to say, having this on and your microwave going in the background reduces throughput. But, dropped packets are worse than small packets that always get through, and this aims to eliminate completely stomped-on packets.) Wifi also has a listen-before-talk model. If it "hears" a microwave running, it thinks it's another station transmitting, and backs off. This feature of the protocol is why long-range networks worked so poorly in the past. If station A can't hear station B, but the AP can hear both of them, then A and B are going to step on each other and the AP won't be able to communicate with either station. This is why the "enterprise" way of deploying networks was to have a ton of access points running at low power; that works well with the listen-before-talk model since the AP likely can't talk to or hear stations that are too far away for the stations in its range to hear. I don't know if interference robustness still exists in modern standards, as I haven't seen it in a control panel for decades, but it was definitely in 802.11b. I have never tested Bluetooth (or read the standard), but basically... the industry knows this is a problem, and handled it a long time ago. Bluetooth might ignore the problem because it plans on frequency-hopping (away from the microwave) anyway, but like all software, that can easily be bugged.
  - function_seven 3y ago
    I have an inverter microwave. Before I went crazy with APs around my house, that microwave would win the war; no zero-crossings to sneak a packet by it. Now my bluetooth only drops when I'm fairly close to the microwave as it runs. (EDIT: my WiFi, not my Bluetooth)
    - mikestew 3y ago
      Are you saying that adding WiFi APs improved your Bluetooth connections when the microwave is running? Or is there such a thing as Bluetooth APs? Pardon my confusion.
- ethbr1 3y ago
  > Try cleaning the mating surfaces around the door thoroughly. (I'm obviously not an electrical engineer, given this is 10x stuff) If we're talking a 2.45 GHz microwave signal, that's a 12.2 cm wavelength. But I thought for shielding you only needed to have gaps of <wavelength to null emissions. Is there some fractional-wavelength propagation, or is my understanding of EM shielding off-base? How are microwaves noisy? E.g. https://physics.stackexchange.com/questions/269672/does-a-faraday-cage-block-outgoing-signals https://physics.stackexchange.com/questions/269672/does-a-fa...
  - itishappy 3y ago
    > Is there some fractional-wavelength propagation? "Propagation" is probably not the right word, but fractional wavelengths can "leak" some amount of field. https://en.wikipedia.org/wiki/Evanescent_field https://en.wikipedia.org/wiki/Evanescent_field
    - londons_explore 3y ago
      Notably, that field is powerful enough that microwave doors need to be about an inch thick. The rest of the inch is just empty space and a sheet of plastic to stop you putting your fingers into the evanescent field. Unfortunately there were a few microwaves sold recently in Europe which forgot that design element, and if you pointed at food while cooking it, you would cook your fingers too.
  - kiltedpanda 3y ago
    You're right. The rule of thumb for EMC engineers is to bond joints at no further than wavelength/10 where the wavelength corresponds to the highest frequency that you wish to maintain good shielding effectiveness. Some MIL projects use wavelength/100.
  - londons_explore 3y ago
    But the gap around the door might only be millimeters wide, but it is 30cm or more long. It is "both* dimensions that must be a long way below the wavelength to keep microwaves in. Instead the door seal uses a technique called a quarter wave choke. It relies on reflecting back any microwaves wanting to escape, and by making incoming and reflected waves perfectly cancel, no power is transmitted. As OP said, even a small amount of soup dripped onto the seal and your microwaves will all start escaping.
- Varriount 3y ago
  I wonder if building a faraday cage around it would do anything.
baal80spam 3y ago
Yes, sound in my headphones is distorted when I go near a working microwave oven.
counterpartyrsk 3y ago
Does the sound quality improve if either the phone or speaker are inside the microwave? We must test all possible scenarios.
- zzless 3y ago
  I understand this is a (good) attempt at humor but this might be an interesting idea to see if Bluetooth leaks from inside the microwave oven (or from the outside in). Of course, the microwave has to stay off, naturally :)
AuthorizedCust 3y ago
Microwaves are well known to interfere with 2.4 GHz communications. That’s one of Bluetooth’s channels. https://en.m.wikipedia.org/wiki/2.4_GHz_radio_use https://en.m.wikipedia.org/wiki/2.4_GHz_radio_use
deleted 3y ago
[deleted]
causi 3y ago
Depends on both the microwave and the bluetooth device in question. My favorite pair of headphones are rather inexpensive and my microwave is a couple decades old and very high-wattage, and I get interference if I stand within a couple feet of it. I haven't had any other microwave or any other bluetooth device experience noticeable interference.
zh3 3y ago
Microwaves typically run 2.500GHz, most bluetooth and wifi is from 2.400 to 2.480GHz to keep some space between them (so if you want to minimise WiFi/Microwave issues on 2.4Ghz, use a low WiFi channel). Bluetooth is adaptive and will hop frequencies to find quiet space in the range above, however microwaves are an intermittent source so when they go on the leakage will kill any bluetooth that's on a nearby frequency. An easy way to see this is with a BBC microbit; you can measure the signal strength on channels 1 to 100 (2.4 to 2.5GHz in 1MHz steps) and so plot the local RF sources (WiFi, Bluetooth, Microwave, etc.).
- anotherhue 3y ago
  Where are you getting 2.5? 2450 +/- 50 is what I have seen.
  - zh3 3y ago
    From Nordic Semi (nrf52 chips behind most BLE/ANT+ implementations these days). Seems microwave ovens use the + side of the tolerance (2.45+0.5_ so they suggest sticking to 2.40 to 2.48 (channels 1 to 80 in their parlance).
    - anotherhue 3y ago
      Interesting, I wonder if this might just be due to the dominance of one particular magnetron design / manufacturer. Thanks for getting back to me.
float4 3y ago
What happens when you place your phone in the microwave (don't turn the oven on, obviously) and walk away with your speaker? I'm curious what kind of range you're getting. For reference: I just tried this with iPhone 13 mini + WH-1000XM3 and the connection dropped after ~5 meters.
kpozin 3y ago
My data is anecdotal, but I've observed that Panasonic inverter ovens that I've used interfered in the 2.4GHz range, while models of other brands (e.g. GE) have not. (This is unfortunate because Panasonic seems to be the only brand that can actually adjust power output, whereas the others simulate lower power levels by cycling on and off.)
- lathiat 3y ago
  Adjusting the power output is the definition of “inverter” basically. A few brands offer it, it seems like it was probably patented as it was only 3-4 higher end well known brands at least in Australia. Inverters themselves are potential noise sources though so may be part of the issue but other implementations may not interfere.
- callalex 3y ago
  You can thank terribly written intellectual property laws for that exclusivity. It’s not like inverters are some kind of new technology, and yet here we are.
  - londons_explore 3y ago
    I suspect the inverter design is now cheaper too. The traditional design needs all power to go through a transformer. A 1 kilowatt 60Hz transformer necessarily uses a lot of copper and steel. The inverter design can use MOSFETs (theoretically cheap, but a reasonable IP cost) and far less copper and steel.
- liminalsunset 3y ago
  LG now sells inverter microwaves under the NeoChef brand, I believe. I saw one in a second hand store recently so they've existed for a while now. I haven't tested one to see if it interferes with anything, though.
  - nkerkin 3y ago
    I have one, and yes, much interference.
freitzkriesler2 3y ago
Microwaves aren't perfect faraday cages and a little spectrum bleed does happen. Not enough to cook you but definitely enough to make your wifi call or Bluetooth device can get iffy if the microwave is in the path of the sender and receiver.
crazygringo 3y ago
Around 15 years ago my wireless Magic Mouse's pointer movements would become so choppy as to become unusable not just if my microwave was in use, but also if a neighbor's was. But upgrading to a new laptop+mouse fixed it, and I've never had a problem since. Since they're on roughly the same frequency, interference makes sense. Microwave ovens are high-energy, Bluetooth is low-energy, so minor leakage can still have a big effect. But there's no health concerns or anything, precisely because it's still so low-energy. (You can't cook food with Bluetooth!) But it does seem like some Bluetooth chips/stacks are better at hopping around frequencies to avoid it than others, or that particular devices just develop bugs.
- vehemenz 3y ago
  I've never seen this with a microwave, but this exact thing (Bluetooth mouse choppiness) happens with interference from other Bluetooth devices in the vicinity, especially when pairing. Most microwaves do produce some BT interference, so I am not surprised that the symptoms would be similar.
baz00 3y ago
My neighbour's microwave nukes my bluetooth entirely. I have moved to wired everything and life is good finally!
Ellipsis753 3y ago
Yep. I've seen Bluetooth be affected by microwaves. Also seen WiFi be affected by Bluetooth. It doesn't mean your microwave is unsafe.
senectus1 3y ago
nope. Had that happen once, swapped the microwave out and never happened again since.
jraph 3y ago
Didn't Wi-Fi originally use 2,4 GHz because it was free to use (without needing a license), because of the noise produced by microwaves on this frequency?
- anotherhue 3y ago
  Yes, 1946 was when the FCC opened up 2450 +/- 50 Mc (later MHz), for microwave and medical diathermy use. It was later, in the 80s that they allowed intentional emission. Either as CDMA or FHSS. Within a year we had Wi-Fi (CDMA) and Bluetooth (FHSS).
adrianmonk 3y ago
That's inconvenient, but it's definitely expected. From https://en.wikipedia.org/wiki/ISM_radio_band https://en.wikipedia.org/wiki/ISM_radio_band : > The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific, and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) energy in these bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices are limited to certain bands of frequencies. In general, communications equipment operating in ISM bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation in these bands. > Despite the intent of the original allocations, in recent years the fastest-growing use of these bands has been for short-range, low-power wireless communications systems, since these bands are often approved for such devices, which can be used without a government license, as would otherwise be required for transmitters; ISM frequencies are often chosen for this purpose as they already must tolerate interference issues. Cordless phones, Bluetooth devices, near-field communication (NFC) devices, garage door openers, baby monitors, and wireless computer networks (Wi-Fi) may all use the ISM frequencies, although these low-power transmitters are not considered to be ISM devices. So basically the microwave oven's Faraday cage needs to block enough for safety. There are regulations about the radio spectrum, but they allow it to emit some.
vehemenz 3y ago
Yes. My work microwave is just at the end of my Bluetooth range for my Airpods Pro. If the microwave is off, then my signal is basically fine and won't cut out. Once I turn the microwave on, all are bets off, and it cuts in and out.
- laweijfmvo 3y ago
  Same. Airprods Pro are the first product i've ever used that experienced microwave interference.
Fnoord 3y ago
It did with anything 2.4 GHz (BT, WiFi, Logitech nRF, etc etc). I threw my microwave away. Not really missed it, it was a waste of space, but anyone who wants to do a deauth attack can also get you to disconnect from WiFi. Right now we got two airfryers, an oven (airfryers are basically mini ovens), and a mini pizza oven. The latter is pretty bad and hard to operate but because our main oven is broken, its as good as it gets. Not much edible comes out of a microwave. The tastes are almost always bland. I'd rather not eat. For my young kids I get to cook plain stuff, they don't enjoy anything complex but like the same stuff like pasta over and over again. We used au bain-marie in past. It requires a little bit more planning but nothing dramatic.
- crazygringo 3y ago
  I use my microwave constantly, but it's all for defrosting. Once the food is no longer frozen but not yet piping hot, it then goes into the toaster oven or skillet or whatever to finish heating including crisping/browning. It's great because it not only saves significant time, but loses less moisture. Heating from frozen in an oven dries things out too much, or you have to use up aluminum foil to wrap it, which is annoying and a waste. Also obviously microwaves are great for soup.
  - Fnoord 3y ago
    We eat soup once a week, on Saturday usually. I open the package (like this [1]), put it in a pan. Warm it up and... have soup. With a fresh baguette, some hummus or aioli or whatever. No microwave required. If its frozen soup (made in bulk it is very cheap) then it just has to be put out early enough. A microwave could help to defeat bad planning or tough time schedule. [1] https://www.ah.nl/producten/product/wi920/ah-rijkgevulde-tomatensoep https://www.ah.nl/producten/product/wi920/ah-rijkgevulde-tom...
    - crazygringo 3y ago
      Well sure. Like I said, the main benefit of the microwave is to defrost faster. Nothing requires a microwave. And soup doesn't benefit from browning or crispness so you can heat it up in the microwave the whole way. There's nothing wrong with the pan, it just takes longer. And there isn't any taste/texture benefit over the microwave in the case of soup.
Eumenes 3y ago
I noticed a quirk in my microwave recently if you apply pressure to the door handle it'll turn on the microwave. Kinda spooky.
- ilc 3y ago
  If that isn't a design feature, may be time for a new microwave friend.
jrs235 3y ago
I had a microwave that interfered with my 2.4 Ghz WiFi signal. If the microwave ran for more than 30 seconds any devices connected to the 2.4 Ghz SSIDs would "stop working". I assume is was due to too much noise caused by the microwave. Devices connected to the 5 Ghz SSIDs worked fine.
TnRHL 3y ago
I think microwaves ovens are allowed to emit up to 1W of energy. As mikewarot said - it's amazing Wifi/BT works at all.
trey-jones 3y ago
Anytime somebody runs the microwave in my office, my headphones start crackling. I'm sitting probably 20 feet from the microwave and my computer (source of the bluetooth signal) is right next to me.
- ta1243 3y ago
  My headphones are fine, and the battery doesn't drop out either -- this 3.5mm cable is great.
  - saiya-jin 3y ago
    I think we should adapt it into devices like phones, after all who doesnt like cheap quality audio hardware that just works (TM), and for some reason doesnt degrade or die after few years due to batteries?
    - warrenm 3y ago
      I hate cabled headphones on a portable device Physically tethering to something designed to be slipped into a pocket, put in case, set down on the table while I walk around, etc is stupid Physically tethering to a stationary object (that you can't really use if you walk away form it) makes sense in some cases
      - aidenn0 3y ago
        I like headphones primarily on devices that go in my pocket because they move with me. When I use headphones at a non-portable device I'm likely to damage them by walking away with them on. I use a BT headset at my PC for this reason; I can get up and pace &c. without worrying. Quick tip if you are using wired headphones while doing chores: run the cable under your shirt; that should leave little-to-no exposed cable to snag on things.
        warrenm 3y ago
        >run the cable under your shirt; that should leave little-to-no exposed cable to snag on things ...except your shirt when you take your phone out of your pocket to change what's playing, answer a message, etc :|
gertlex 3y ago
My microwave is less than 2 feet from my wifi router :D (but yeah, mostly use 5GHz channels for wifi) I have no issue listening to podcasts in the kitchen while the microwave is running. I'm using Logitech H800 headphones (modified with wires going to my hearing aids). If I put my phone in my GE microwave, I have sound breakup issues within 2-3 feet away from the microwave. Sounds like it's better "shielded" than some others mentioned here.
gumby 3y ago
Is the interference from leaking microwaves themselves or resonant leakage from the magnetron and/or support circuitry which is desired to be as cheap as possible? Also you can’t really see the cage: that mesh you see in the window is indeed designed to block emission, but in a cheap one you can often see a gap between the mesh and the bezel, and of course the shell is a cheaply assembled rectangle without tight corner fittings so is probably leaking a small amount here, especially at the back, where they assume a wall will catch any leaks.
vel0city 3y ago
At an old apartment my Chromecast would become unusable whenever I'd use the microwave in the other room. It took me a bit to understand why every now and then it would just take a dump, turns out it was my roommate cooking dinner. Meanwhile my current microwave I can cook and be on bluetooth headphones paired to my laptop across the house and there's no issue. Some microwaves are better shielded than others. It might be leakage from the actual cook box, it might be leakage from all the extra circuitry. Even though the frequency of most microwave's primary element is going to be a little higher than what Bluetooth is supposed to run on, if there's enough energy leaking you'll still potentially drown out the signal. Filters, especially ones made to be kind of cheap, aren't perfect and can't always filter out everything. And as mentioned you're trying to catch a few milliwatt signal right next to something that's trying to generate and contain a 1,000,000 milliwatt signal.
aimor 3y ago
You can build a "lectenna" and see where your microwave is leaking energy out. https://www.youtube.com/watch?v=V5SMF9p-4Q0 https://www.youtube.com/watch?v=V5SMF9p-4Q0
TheAceOfHearts 3y ago
My Bluetooth headphones usually experience connectivity issues if I have line of sight with my running microwave. Interestingly it only happens sometimes. Usually audio will stop playing or cut off until there's a wall between me and the microwave.
pi-rat 3y ago
My first microwave absolutely wrecked 2.4 ghz wifi, replaced it after a few years and the new one didn’t. Didn’t have many BT devices back then, but bet it would jam them as well.
- thomashabets2 3y ago
  Would probably have been enough to change the wifi channel.
eosophos 3y ago
Yes. I've wondered about this for a while. Because although the microwave is supposed to be fully shielded, when I take EMF readings on it with my TriField TF2 EMF meter, it's spitting out >100mW/m^2 when it's turned on. And I've seen this happen with just about every microwave I've tried this on. The only ones that haven't seem to be those expensive integrated under-counter ones where the tray slides out rather than opens like a door. Also my phone still works/receives calls when I put it in there, so it can't be as good of a faraday cage as it's supposed to be...
- TheRealPomax 3y ago
  "Microwaves are supposed to be perfectly shielded" is one of those myths that just won't die. Microwaves are allowed to leak a lot, with exactly "how much" dependent on whatever agency writes the rules where you live of course =) In the US, for instance, it's the Center for Devices and Radiological Health (CDRH), part of the FDA, that sets the rules for microwaves, with the performance standard set forth by CDRH allowing leakage (measured at five centimeters from the oven surface) of 1 mW/cm² at the time of manufacture, and a maximum level of 5 mW/cm² during the lifetime of the oven.[1] A strong wifi router or bluetooth transmitter may be transmitting at one or two orders of magnitude greater than the microwave's allowed to leak, but if you're closer to the microwave than the wifi/bluetooth transmitter, or the microwave is simply between you and the wifi/blueooth transmitter, or especially if you have a low power transmitter, that microwave's going to wreak havoc. [1] https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e3.pdf https://transition.fcc.gov/Bureaus/Engineering_Technology/Do...
thomashabets2 3y ago
I used an SDR to check my microwave's emissions. They were pretty narrow and stable-ish. Not stable like an actual radio, but not all over the place wrecking all of the wifi channels. I've not had it interfere with bluetooth or wifi. Bluetooth frequency hops, and moves away from channels with interference (dropped frames), doesn't it? I have a couple of illustrations at https://blog.habets.se/2017/06/Microwave.html https://blog.habets.se/2017/06/Microwave.html
- anotherhue 3y ago
  > Bluetooth frequency hops, and moves away from channels with interference (dropped frames), doesn't it? Hops yes, remembers to avoid certain channels, maybe. IIRC the hop sequence is controlled by the master device so that might add a layer of confusion if it isn't experiencing the issue. > I used an SDR to check my microwave's emissions. They were pretty narrow and stable-ish. Yes, the issue is it's manufacturing dependent, so a different batch of those same magnetrons the next weeek would have different properties. Hence the wide band.
charles_f 3y ago
I have the same interference with the microwaves at work. There's also a small plaza in what's considered the very center of my city where I get tons of interference (sound basically keeps cutting as if I was losing connection). There's a subway station underground, and some trolley cables suspended in the air, so maybe there's some sort of power converter underground.
ThatMedicIsASpy 3y ago
It destroys the wifi of whatever phone or tablet is next to it while running.
circuit10 3y ago
Relevant XKCD: https://xkcd.com/654/ https://xkcd.com/654/
browningstreet 3y ago
My neighbors have something crazy emanating from their house. None of my Bluetooth devices, from Bose to Plantronic to new AirPods Pro, survive signal connectivity when I walk past their house. The connection gets very disrupted and the devices have trouble reconnecting. So I have to leave everything off when I go for a run and not connect headphones until I make it to the end of the street. It’s weird.
- deleted 3y ago
  [deleted]
- abdullahkhalids 3y ago
  Crazy story that someone at the local radio astronomy observatory told me. Context: Radio observatories need to minimize as much radio interference as possible. Typically, they are some distance away from population, and people are asked not to use phones within a couple of km of them. Inside the premises no unshielded electronics are allowed. If any are used, you can immediately see the effects on the data being collected by the telescope. Anyway, these guys were getting some sort of strong interference signal at 4 pm every day. They could not figure out where it was coming from. They eventually decided that it was not coming from within, but from somewhere outside the observatory. They got some triangulation equipment out and over the course of several days, finally determined that the signal was coming from a house a couple of km away. So they went over and knocked. Asked the owner what was going on. Turned out, the guy had a electric can opener, and every day at 4 pm he would open a can to feed his dogs. That was the interference signal they were getting all the way to the observatory! Eventually, after some back and forth, they got the guy a new can opener they had vetted to not cause an interference signal.
- randyrand 3y ago
  could be a continuously recording wireless camera that likes to hog spectrum
  - browningstreet 3y ago
    I live in deep suburban/exurbs and this feels quite likely, given the neighborhood. Everyone’s wired for cameras and Amazon Key, etc.
AndyMcConachie 3y ago
My bluetooth often dies when I'm near tram tracks and their overhead electric lines in my city. Kind of annoying given that there are tram tracks everywhere.
willsmith72 3y ago
I used to have to time my gaming around when roommates would be eating. Anything in the microwave was an instant dead connection
geocrasher 3y ago
I once had a microwave I called "The WiFi Killer". I work from home, and did then too, and every time one of my kids, or my wife, would use the microwave, I'd get knocked offline. They do work at 2.4Ghz, and this microwave was pretty old. Replaced it and never had another problem.
peterleiser 3y ago
You can demonstrate WiFi interference by putting a laptop next to your microwave and running a ping test to your WiFi router. I can put my laptop about 4 feet away from my microwave and the ping test hangs as soon as the microwave starts. The ping test resumes as soon as the microwave stops.
- teeray 3y ago
  I haven’t had my afternoon coffee yet, and I read this as though the ping test stops when you put your laptop in the microwave and turn it on.
  - TeMPOraL 3y ago
    It should stop as soon as you close the doors, I think, or else RF interference is the least of your problems with the microwave.
  - peterleiser 3y ago
    Lol! It's tempting. Very tempting.
magicalhippo 3y ago
One thing is Bluetooth. Imagine spending 4 years trying to figure out the source of some mysterious signals registered by your giant radio telescope, only to find it was due to the microwave[1][2] used by the operators to heat hot pockets or whatever. [1]: https://www.theguardian.com/science/2015/may/05/microwave-oven-caused-mystery-signal-plaguing-radio-telescope-for-17-years https://www.theguardian.com/science/2015/may/05/microwave-ov... [2]: https://www.nature.com/articles/521129f https://www.nature.com/articles/521129f
- racl101 3y ago
  "Honey! I'm detecting some some major CMB! You gotta see this! Can you pop my lunch outta the micro too?! Thanks!"
  - basementcat 3y ago
    I had a colleague who "discovered" a pulsar that later turned out to be a radar at San Francisco International Airport. I occasionally still text them photos of the "pulsar" when I have a layover at SFO.
- ethbr1 3y ago
  Can I interest you in some land in western Virginia? https://en.wikipedia.org/wiki/United_States_National_Radio_Quiet_Zone https://en.wikipedia.org/wiki/United_States_National_Radio_Q...
- klyrs 3y ago
  Now I'm imagining a collaboration among radio-astronomers to microwave their lunches at the same time around the globe. Who would set up the prank: grad students making a secret pact at a conference to prank their professors, or vice verse?
tivert 3y ago
In the early days of Wifi, it was pretty common to have your connection drop out whenever someone used the microwave. Both systems use the same frequency band. I assume modern Wifi has gotten better at chugging through the interference (and perhaps microwave-makers better at shielding).
andrewinardeer 3y ago
No, but my reclining chair's motor interferes with the digital signal my TV recieves.
jcrawfordor 3y ago
Bluetooth and WiFi both borrow their spectrum from microwave ovens. It's typical and expected that microwave ovens will cause some interference with other users of the 2.4GHz ISM band that are very nearby. Microwaves operate at very high power levels and are required to be shielded for human safety, but the permissible leakage power is relatively high compared to typical WiFi and Bluetooth devices---there's a simple reason why. From a legal perspective, Bluetooth is essentially pretending to be a microwave oven and making use of the permitted leakage power. This is the cost of the historical regulatory situation that most of these unlicensed radio services use the ISM bands originally allocated for microwave heating. One of the advantages of newer WiFI standards, particularly WiFi 6E, is that they finally change this situation by using the U-NII bands allocated specifically for unlicensed short-range digital communications, rather than for microwave heating. Mind that this is all in the context of US spectrum regulations, although other countries have largely harmonized their approach. I have a lengthier treatment of the topic here: https://computer.rip/2022-04-14-unlicensed-radio.html https://computer.rip/2022-04-14-unlicensed-radio.html
- p_l 3y ago
  The international allocation of 2.4GHz spectrum for microwaves happened at lobbying of USA, but is global - and exists in order for airplane galleys to be equipped with microwave heaters and be allowed to travel internationally.
  - ThePowerOfFuet 3y ago
    Are they actually microwave instead of convection?
    - p_l 3y ago
      Depends on equipment of the plane - the original reasoning for making 2.4GHz the international dumpster spectrum was to install microwaves
      - jbverschoor 3y ago
takinola 3y ago
There's a particular spot on a local highway that interrupts my wireless CarPlay connection if I spend too long in it (eg when traffic is slow). It's right next to an exit with a bunch of buildings (including a hospital) so I'm sure there is some massive emitter in one of those buildings. I'm still at a loss about what could cause that kind of interference inside a major city and still be legal.
- KMag 3y ago
  MRI?
- a_t48 3y ago
  Sounds like Berkeley or North Oakland. :) I have the same issue, I never considered Bluetooth interference.
- oasisaimlessly 3y ago
  WiFi and Bluetooth have basically zero legal protection. FCC Part 15 "this device must accept any interference received, including interference that may cause undesired operation."
Havoc 3y ago
Nope - zero interuptions. Using some cheap ikea microwave.
stringtoint 3y ago
My bluetooth headphones occasionally drop the connection for a moment when I'm standing to my microwave which is warming up food. 2.4GHz after all. Bluetooth and USB 3 don't play along that well either btw.
ajb 3y ago
Tangentially related: knowing they use the same frequency band, I actually used the work microwave oven as a faraday cage for testing our product which used bluetooth. (Close door, observe signal drop behavior). I was bemused to note that you could still connect to a device inside the oven, over short distances... Hopefully the attenuation was sufficient for safety when using it to cook! [ For clarity - the oven wasn't on when I used it as a faraday cage]
riffic 3y ago
microwaves emit RF, heavy concept right?
runjake 3y ago
Nope, this is completely normal. Many commenters are saying microwaves are pretty narrowband. Maybe some are, but I've done spectrum analysis on a few college-dorm-level microwaves in our office with a Wi-Spy and all 3 of these microwaves spam all of the 3 usable 2.4ghz wi-fi channels when cooking. We see similar fun in iMac labs, when they're all (attempting to) use Bluetooth Apple Magic Keyboards at once.
Tommstein 3y ago
In a related question, does anyone know why my Bluetooth earbuds frequently experience brief disruptions when crossing the street at intersections? It happens far too reliably to be a coincidence.
eschneider 3y ago
I once worked for a startup that was trying to stream ads over bluetooth using microwavable foods. It _worked_, but ultimately used too much bandwidth to be practical at the resolutions advertisers wanted.
- daveevad 3y ago
  That sounds amazing. Are there more details like what sort of ads even?
  - pcthrowaway 3y ago
    I agree, technically fascinating, but also... incredibly scummy. As if adtech didn't have enough invasive tools in their arsenal
- KMag 3y ago
  Can you explain a bit more how this worked? The food item harvested energy from the microwave, and modulated the leaked microwaves/transmitted its own signal to hijack nearby bluetooth audio devices to play audio ads?
  - eschneider 3y ago
    Basically, yes.
aetherspawn 3y ago
Yes, my flatmate had a very old 20+ yrs old microwave (the type with a mechanical dial) and when he used it my WiFi would completely drop out until the cooking was done. I bought him a new microwave because I was sick of dropping zoom calls. The modern LG microwave was much better and has virtually no effect on the WiFi.
raminf 3y ago
The 2.4GHz spectrum is shared between Bluetooth and WiFi 802.11b/g. A few years ago, I was doing some work using an Ubertooth-One scanner (https://greatscottgadgets.com/ubertoothone/ https://greatscottgadgets.com/ubertoothone/). It was showing the traffic on different channels. My wife stuck a burrito to warm up in the microwave a room away (30-40 ft). This was with a brand-name model, so presumably properly shielded, etc. Nope. The entire spectrum just went white with noise on all channels. Once the microwave cycle ended, it still took a good 15-30 seconds before the airwaves calmed down and went back to normal traffic.
freedude 3y ago
The microwave became a second class citizen in our kitchen when we got the toaster oven/air fryer combo unit and then was relegated to the garage on top of the fridge. We still use it for popcorn and the occasional hot cocoa and if my coffee gets cold on the weekend I'll wander out there to warm it up. It is almost unneeded. WiFi is better as a result.
bearbin 3y ago
An interesting construction detail of the cheap modern microwave is that it only operates on one half of the mains electric waveform: microwaves use a single high-voltage diode which acts both as half-wave rectifier and voltage doubler. Thus the magnetron only operates for 10 ms in every 20 ms. In theory 2.4 GHz communication protocols can easily time their transmissions to fit in the gaps left by the microwave. 50% bandwidth loss but no other effect. This obviously isn't foolproof in practice, when 2.4 GHz was a thing I remember my WiFi dropping off whenever somebody was nuking some food. But perhaps this might have been a quirk of my Panasonic inverter microwave - which obviously is not the simple standard circuit.
vardump 3y ago
My microwave oven definitely interferes with anything Bluetooth, like headsets etc. Although audio still somewhat works from a laptop upstairs ~30-50 ft away. Anyways, this is normal. Microwave oven generates a lot of 2400-2500 MHz ISM band noise. You're fine.
matthew-wegner 3y ago
I have a waterpik whose motor absolutely obliterates 2.4ghz. I sometimes use it while wearing bluetooth headphones, and music immediately stops. It took me awhile to figure it out (I thought it was my head leaning down and putting a metal pegboard between me and my work machine, but nope).
nmstoker 3y ago
London Underground announcements in certain stations seem to break Bluetooth really frequently. I suspect that at some point, the message is being transmitted by radio and this must be at a frequency that interferes. Also seen on platform WiFi messed up in a similar fashion - this causes the most grief when calling over WiFi kicks in, you make a call only to find it get wrecked the moment they start announcing. Luckily in some stations you actually get a better signal over mobile, so simply turning off WiFi resolves the problem.
lamontcg 3y ago
My waterpik kills bluetooth to my airpods.
nilsherzig 3y ago
Somewhat related, my bluetooth headphones get some static noise when I use my induction oven. On max power ~1900w it disrupts my headphones in a ~2m range haha
chrismorgan 3y ago
Related question: I used to be able to use wifi when my microwave was running. Then one day with no apparent change it started interfering, so that I can no longer use wifi if the microwave is roughly between the two devices connecting over wifi. Of other microwaves I’ve encountered, most haven’t interfered with wifi, but one or two have. Is this a problem?
fbrncci 3y ago
There is this very popular night market where I live, and whenever I drive through a corner of this market, the Bluetooth in my car just stops. I always wondered what this was. There is just so much interference on a square meter.
simne 3y ago
Everyone, who see possible interference from microwave, should ask nearest service and make checks, as this could be manufacturer defect or just leakage of old insulation (rust under paint), and it could be dangerous for health. PS and yes, my friend once found rust hole in old microwave, so this is not very rare thing.
- balaji1 3y ago
  I have wondered about danger to health. The microwave interference is obvious with the airpods.
  - simne 3y ago
    It's not good. May I just fortunate, but I have not seen any problems from old mature manufacturers, like Panasonic. Sure, I mean new microwave, or in absolutely perfect state.
craigdalton 3y ago
Yes, we had an LG microwave, took it back after 3 weeks because it knocked out both wifi and Bluetooth. The store didn't want to refund. Said it had to go to warranty repair. Repair shop said they cannot decrease RF emissions, store begrudgingly gave credit.
cyanydeez 3y ago
Sounds like. A microwave problem
bannanman 3y ago
My microwave sat Infront of a phone jack. (we had ADSL2 for internet) Every so often out internet would just stop. Finally realized it was the microwave pumping interference into the jack it took out the internet. Also worth noting, if it was a bad rain storm the internet would drop in speed.

119 points by Jeff_Brown 3y ago

hulitu 3y ago

> Ask HN: Does your microwave interfere with Bluetooth? Mine does As far as i know you can make a complain by the FCC.

kevinherron 3y ago

Not great, not terrible.

mikewarot 3y ago

There's about 1000 watts of RF inside the microwave, it has to be attenuated to less than a few microwatts on the outside to avoid congestion, as they use the same frequency band. I'm amazed WiFi or Bluetooth ever works at all. 8) You can thank Hedy Lamar for that. Try cleaning the mating surfaces around the door thoroughly. If that doesn't work, consider replacing the microwave or relocating the speaker.

H8crilA 3y ago
The microwave RF emission is actually very narrowband, though the frequency drifts all the time. Bluetooth uses FHSS so it will eventually go though, unless the noise is so powerful that it saturates the receiver. I'd post a screenshot from a HackRF-produced waterfall, but I don't have a microwave :). Some wifi controllers can measure energy in the spectrum and can be used to plot a simple waterfall.
- grepfru_it 3y ago
  >but I don't have a microwave :) Living the dream!
NikkiA 3y ago
If it's an old microwave replacing the door seal would be cheaper and easier.
anotherhue 3y ago
> You can thank Hedy Lamar for that. eh... maybe. Don't forget the microwave isn't CW so there's plenty of transmission slots available on the off cycle.
jrockway 3y ago
Wifi has an "interference robustness" option which is designed with microwave ovens in mind. The power output of a microwave is a sine wave, because it's powered from your AC line power, and doesn't emit energy during the zero crossings. "Interference robustness" times packet sends (and lengths) to be when the microwave is producing the least amount of power. Thus, you spend half of every 60th of a second irradiating your food, and the other half downloading videos. (Needless to say, having this on and your microwave going in the background reduces throughput. But, dropped packets are worse than small packets that always get through, and this aims to eliminate completely stomped-on packets.) Wifi also has a listen-before-talk model. If it "hears" a microwave running, it thinks it's another station transmitting, and backs off. This feature of the protocol is why long-range networks worked so poorly in the past. If station A can't hear station B, but the AP can hear both of them, then A and B are going to step on each other and the AP won't be able to communicate with either station. This is why the "enterprise" way of deploying networks was to have a ton of access points running at low power; that works well with the listen-before-talk model since the AP likely can't talk to or hear stations that are too far away for the stations in its range to hear. I don't know if interference robustness still exists in modern standards, as I haven't seen it in a control panel for decades, but it was definitely in 802.11b. I have never tested Bluetooth (or read the standard), but basically... the industry knows this is a problem, and handled it a long time ago. Bluetooth might ignore the problem because it plans on frequency-hopping (away from the microwave) anyway, but like all software, that can easily be bugged.
- function_seven 3y ago
  I have an inverter microwave. Before I went crazy with APs around my house, that microwave would win the war; no zero-crossings to sneak a packet by it. Now my bluetooth only drops when I'm fairly close to the microwave as it runs. (EDIT: my WiFi, not my Bluetooth)
  - mikestew 3y ago
    Are you saying that adding WiFi APs improved your Bluetooth connections when the microwave is running? Or is there such a thing as Bluetooth APs? Pardon my confusion.
ethbr1 3y ago
> Try cleaning the mating surfaces around the door thoroughly. (I'm obviously not an electrical engineer, given this is 10x stuff) If we're talking a 2.45 GHz microwave signal, that's a 12.2 cm wavelength. But I thought for shielding you only needed to have gaps of <wavelength to null emissions. Is there some fractional-wavelength propagation, or is my understanding of EM shielding off-base? How are microwaves noisy? E.g. https://physics.stackexchange.com/questions/269672/does-a-faraday-cage-block-outgoing-signals https://physics.stackexchange.com/questions/269672/does-a-fa...
- itishappy 3y ago
  > Is there some fractional-wavelength propagation? "Propagation" is probably not the right word, but fractional wavelengths can "leak" some amount of field. https://en.wikipedia.org/wiki/Evanescent_field https://en.wikipedia.org/wiki/Evanescent_field
  - londons_explore 3y ago
    Notably, that field is powerful enough that microwave doors need to be about an inch thick. The rest of the inch is just empty space and a sheet of plastic to stop you putting your fingers into the evanescent field. Unfortunately there were a few microwaves sold recently in Europe which forgot that design element, and if you pointed at food while cooking it, you would cook your fingers too.
- kiltedpanda 3y ago
  You're right. The rule of thumb for EMC engineers is to bond joints at no further than wavelength/10 where the wavelength corresponds to the highest frequency that you wish to maintain good shielding effectiveness. Some MIL projects use wavelength/100.
- londons_explore 3y ago
  But the gap around the door might only be millimeters wide, but it is 30cm or more long. It is "both* dimensions that must be a long way below the wavelength to keep microwaves in. Instead the door seal uses a technique called a quarter wave choke. It relies on reflecting back any microwaves wanting to escape, and by making incoming and reflected waves perfectly cancel, no power is transmitted. As OP said, even a small amount of soup dripped onto the seal and your microwaves will all start escaping.
Varriount 3y ago
I wonder if building a faraday cage around it would do anything.

baal80spam 3y ago

Yes, sound in my headphones is distorted when I go near a working microwave oven.

counterpartyrsk 3y ago

Does the sound quality improve if either the phone or speaker are inside the microwave? We must test all possible scenarios.

zzless 3y ago
I understand this is a (good) attempt at humor but this might be an interesting idea to see if Bluetooth leaks from inside the microwave oven (or from the outside in). Of course, the microwave has to stay off, naturally :)

AuthorizedCust 3y ago

Microwaves are well known to interfere with 2.4 GHz communications. That’s one of Bluetooth’s channels. https://en.m.wikipedia.org/wiki/2.4_GHz_radio_use https://en.m.wikipedia.org/wiki/2.4_GHz_radio_use

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causi 3y ago

Depends on both the microwave and the bluetooth device in question. My favorite pair of headphones are rather inexpensive and my microwave is a couple decades old and very high-wattage, and I get interference if I stand within a couple feet of it. I haven't had any other microwave or any other bluetooth device experience noticeable interference.

zh3 3y ago

Microwaves typically run 2.500GHz, most bluetooth and wifi is from 2.400 to 2.480GHz to keep some space between them (so if you want to minimise WiFi/Microwave issues on 2.4Ghz, use a low WiFi channel). Bluetooth is adaptive and will hop frequencies to find quiet space in the range above, however microwaves are an intermittent source so when they go on the leakage will kill any bluetooth that's on a nearby frequency. An easy way to see this is with a BBC microbit; you can measure the signal strength on channels 1 to 100 (2.4 to 2.5GHz in 1MHz steps) and so plot the local RF sources (WiFi, Bluetooth, Microwave, etc.).

anotherhue 3y ago
Where are you getting 2.5? 2450 +/- 50 is what I have seen.
- zh3 3y ago
  From Nordic Semi (nrf52 chips behind most BLE/ANT+ implementations these days). Seems microwave ovens use the + side of the tolerance (2.45+0.5_ so they suggest sticking to 2.40 to 2.48 (channels 1 to 80 in their parlance).
  - anotherhue 3y ago
    Interesting, I wonder if this might just be due to the dominance of one particular magnetron design / manufacturer. Thanks for getting back to me.

float4 3y ago

What happens when you place your phone in the microwave (don't turn the oven on, obviously) and walk away with your speaker? I'm curious what kind of range you're getting. For reference: I just tried this with iPhone 13 mini + WH-1000XM3 and the connection dropped after ~5 meters.

kpozin 3y ago

My data is anecdotal, but I've observed that Panasonic inverter ovens that I've used interfered in the 2.4GHz range, while models of other brands (e.g. GE) have not. (This is unfortunate because Panasonic seems to be the only brand that can actually adjust power output, whereas the others simulate lower power levels by cycling on and off.)

lathiat 3y ago
Adjusting the power output is the definition of “inverter” basically. A few brands offer it, it seems like it was probably patented as it was only 3-4 higher end well known brands at least in Australia. Inverters themselves are potential noise sources though so may be part of the issue but other implementations may not interfere.
callalex 3y ago
You can thank terribly written intellectual property laws for that exclusivity. It’s not like inverters are some kind of new technology, and yet here we are.
- londons_explore 3y ago
  I suspect the inverter design is now cheaper too. The traditional design needs all power to go through a transformer. A 1 kilowatt 60Hz transformer necessarily uses a lot of copper and steel. The inverter design can use MOSFETs (theoretically cheap, but a reasonable IP cost) and far less copper and steel.
liminalsunset 3y ago
LG now sells inverter microwaves under the NeoChef brand, I believe. I saw one in a second hand store recently so they've existed for a while now. I haven't tested one to see if it interferes with anything, though.
- nkerkin 3y ago
  I have one, and yes, much interference.

freitzkriesler2 3y ago

Microwaves aren't perfect faraday cages and a little spectrum bleed does happen. Not enough to cook you but definitely enough to make your wifi call or Bluetooth device can get iffy if the microwave is in the path of the sender and receiver.

crazygringo 3y ago

Around 15 years ago my wireless Magic Mouse's pointer movements would become so choppy as to become unusable not just if my microwave was in use, but also if a neighbor's was. But upgrading to a new laptop+mouse fixed it, and I've never had a problem since. Since they're on roughly the same frequency, interference makes sense. Microwave ovens are high-energy, Bluetooth is low-energy, so minor leakage can still have a big effect. But there's no health concerns or anything, precisely because it's still so low-energy. (You can't cook food with Bluetooth!) But it does seem like some Bluetooth chips/stacks are better at hopping around frequencies to avoid it than others, or that particular devices just develop bugs.

vehemenz 3y ago
I've never seen this with a microwave, but this exact thing (Bluetooth mouse choppiness) happens with interference from other Bluetooth devices in the vicinity, especially when pairing. Most microwaves do produce some BT interference, so I am not surprised that the symptoms would be similar.

baz00 3y ago

My neighbour's microwave nukes my bluetooth entirely. I have moved to wired everything and life is good finally!

Ellipsis753 3y ago

Yep. I've seen Bluetooth be affected by microwaves. Also seen WiFi be affected by Bluetooth. It doesn't mean your microwave is unsafe.

senectus1 3y ago

nope. Had that happen once, swapped the microwave out and never happened again since.

jraph 3y ago

Didn't Wi-Fi originally use 2,4 GHz because it was free to use (without needing a license), because of the noise produced by microwaves on this frequency?

anotherhue 3y ago
Yes, 1946 was when the FCC opened up 2450 +/- 50 Mc (later MHz), for microwave and medical diathermy use. It was later, in the 80s that they allowed intentional emission. Either as CDMA or FHSS. Within a year we had Wi-Fi (CDMA) and Bluetooth (FHSS).

adrianmonk 3y ago

That's inconvenient, but it's definitely expected. From https://en.wikipedia.org/wiki/ISM_radio_band https://en.wikipedia.org/wiki/ISM_radio_band : > The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific, and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) energy in these bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices are limited to certain bands of frequencies. In general, communications equipment operating in ISM bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation in these bands. > Despite the intent of the original allocations, in recent years the fastest-growing use of these bands has been for short-range, low-power wireless communications systems, since these bands are often approved for such devices, which can be used without a government license, as would otherwise be required for transmitters; ISM frequencies are often chosen for this purpose as they already must tolerate interference issues. Cordless phones, Bluetooth devices, near-field communication (NFC) devices, garage door openers, baby monitors, and wireless computer networks (Wi-Fi) may all use the ISM frequencies, although these low-power transmitters are not considered to be ISM devices. So basically the microwave oven's Faraday cage needs to block enough for safety. There are regulations about the radio spectrum, but they allow it to emit some.

vehemenz 3y ago

Yes. My work microwave is just at the end of my Bluetooth range for my Airpods Pro. If the microwave is off, then my signal is basically fine and won't cut out. Once I turn the microwave on, all are bets off, and it cuts in and out.

laweijfmvo 3y ago
Same. Airprods Pro are the first product i've ever used that experienced microwave interference.

Fnoord 3y ago

It did with anything 2.4 GHz (BT, WiFi, Logitech nRF, etc etc). I threw my microwave away. Not really missed it, it was a waste of space, but anyone who wants to do a deauth attack can also get you to disconnect from WiFi. Right now we got two airfryers, an oven (airfryers are basically mini ovens), and a mini pizza oven. The latter is pretty bad and hard to operate but because our main oven is broken, its as good as it gets. Not much edible comes out of a microwave. The tastes are almost always bland. I'd rather not eat. For my young kids I get to cook plain stuff, they don't enjoy anything complex but like the same stuff like pasta over and over again. We used au bain-marie in past. It requires a little bit more planning but nothing dramatic.

crazygringo 3y ago
I use my microwave constantly, but it's all for defrosting. Once the food is no longer frozen but not yet piping hot, it then goes into the toaster oven or skillet or whatever to finish heating including crisping/browning. It's great because it not only saves significant time, but loses less moisture. Heating from frozen in an oven dries things out too much, or you have to use up aluminum foil to wrap it, which is annoying and a waste. Also obviously microwaves are great for soup.
- Fnoord 3y ago
  We eat soup once a week, on Saturday usually. I open the package (like this [1]), put it in a pan. Warm it up and... have soup. With a fresh baguette, some hummus or aioli or whatever. No microwave required. If its frozen soup (made in bulk it is very cheap) then it just has to be put out early enough. A microwave could help to defeat bad planning or tough time schedule. [1] https://www.ah.nl/producten/product/wi920/ah-rijkgevulde-tomatensoep https://www.ah.nl/producten/product/wi920/ah-rijkgevulde-tom...
  - crazygringo 3y ago
    Well sure. Like I said, the main benefit of the microwave is to defrost faster. Nothing requires a microwave. And soup doesn't benefit from browning or crispness so you can heat it up in the microwave the whole way. There's nothing wrong with the pan, it just takes longer. And there isn't any taste/texture benefit over the microwave in the case of soup.

Eumenes 3y ago

I noticed a quirk in my microwave recently if you apply pressure to the door handle it'll turn on the microwave. Kinda spooky.

ilc 3y ago
If that isn't a design feature, may be time for a new microwave friend.

jrs235 3y ago

I had a microwave that interfered with my 2.4 Ghz WiFi signal. If the microwave ran for more than 30 seconds any devices connected to the 2.4 Ghz SSIDs would "stop working". I assume is was due to too much noise caused by the microwave. Devices connected to the 5 Ghz SSIDs worked fine.

TnRHL 3y ago

I think microwaves ovens are allowed to emit up to 1W of energy. As mikewarot said - it's amazing Wifi/BT works at all.

trey-jones 3y ago

Anytime somebody runs the microwave in my office, my headphones start crackling. I'm sitting probably 20 feet from the microwave and my computer (source of the bluetooth signal) is right next to me.

ta1243 3y ago
My headphones are fine, and the battery doesn't drop out either -- this 3.5mm cable is great.
- saiya-jin 3y ago
  I think we should adapt it into devices like phones, after all who doesnt like cheap quality audio hardware that just works (TM), and for some reason doesnt degrade or die after few years due to batteries?
  - warrenm 3y ago
    I hate cabled headphones on a portable device Physically tethering to something designed to be slipped into a pocket, put in case, set down on the table while I walk around, etc is stupid Physically tethering to a stationary object (that you can't really use if you walk away form it) makes sense in some cases
    - aidenn0 3y ago
      I like headphones primarily on devices that go in my pocket because they move with me. When I use headphones at a non-portable device I'm likely to damage them by walking away with them on. I use a BT headset at my PC for this reason; I can get up and pace &c. without worrying. Quick tip if you are using wired headphones while doing chores: run the cable under your shirt; that should leave little-to-no exposed cable to snag on things.
      - warrenm 3y ago
        >run the cable under your shirt; that should leave little-to-no exposed cable to snag on things ...except your shirt when you take your phone out of your pocket to change what's playing, answer a message, etc :|

gertlex 3y ago

My microwave is less than 2 feet from my wifi router :D (but yeah, mostly use 5GHz channels for wifi) I have no issue listening to podcasts in the kitchen while the microwave is running. I'm using Logitech H800 headphones (modified with wires going to my hearing aids). If I put my phone in my GE microwave, I have sound breakup issues within 2-3 feet away from the microwave. Sounds like it's better "shielded" than some others mentioned here.

gumby 3y ago

Is the interference from leaking microwaves themselves or resonant leakage from the magnetron and/or support circuitry which is desired to be as cheap as possible? Also you can’t really see the cage: that mesh you see in the window is indeed designed to block emission, but in a cheap one you can often see a gap between the mesh and the bezel, and of course the shell is a cheaply assembled rectangle without tight corner fittings so is probably leaking a small amount here, especially at the back, where they assume a wall will catch any leaks.

vel0city 3y ago

At an old apartment my Chromecast would become unusable whenever I'd use the microwave in the other room. It took me a bit to understand why every now and then it would just take a dump, turns out it was my roommate cooking dinner. Meanwhile my current microwave I can cook and be on bluetooth headphones paired to my laptop across the house and there's no issue. Some microwaves are better shielded than others. It might be leakage from the actual cook box, it might be leakage from all the extra circuitry. Even though the frequency of most microwave's primary element is going to be a little higher than what Bluetooth is supposed to run on, if there's enough energy leaking you'll still potentially drown out the signal. Filters, especially ones made to be kind of cheap, aren't perfect and can't always filter out everything. And as mentioned you're trying to catch a few milliwatt signal right next to something that's trying to generate and contain a 1,000,000 milliwatt signal.

aimor 3y ago

You can build a "lectenna" and see where your microwave is leaking energy out. https://www.youtube.com/watch?v=V5SMF9p-4Q0 https://www.youtube.com/watch?v=V5SMF9p-4Q0

TheAceOfHearts 3y ago

My Bluetooth headphones usually experience connectivity issues if I have line of sight with my running microwave. Interestingly it only happens sometimes. Usually audio will stop playing or cut off until there's a wall between me and the microwave.

pi-rat 3y ago

My first microwave absolutely wrecked 2.4 ghz wifi, replaced it after a few years and the new one didn’t. Didn’t have many BT devices back then, but bet it would jam them as well.

thomashabets2 3y ago
Would probably have been enough to change the wifi channel.

eosophos 3y ago

Yes. I've wondered about this for a while. Because although the microwave is supposed to be fully shielded, when I take EMF readings on it with my TriField TF2 EMF meter, it's spitting out >100mW/m^2 when it's turned on. And I've seen this happen with just about every microwave I've tried this on. The only ones that haven't seem to be those expensive integrated under-counter ones where the tray slides out rather than opens like a door. Also my phone still works/receives calls when I put it in there, so it can't be as good of a faraday cage as it's supposed to be...

TheRealPomax 3y ago
"Microwaves are supposed to be perfectly shielded" is one of those myths that just won't die. Microwaves are allowed to leak a lot, with exactly "how much" dependent on whatever agency writes the rules where you live of course =) In the US, for instance, it's the Center for Devices and Radiological Health (CDRH), part of the FDA, that sets the rules for microwaves, with the performance standard set forth by CDRH allowing leakage (measured at five centimeters from the oven surface) of 1 mW/cm² at the time of manufacture, and a maximum level of 5 mW/cm² during the lifetime of the oven.[1] A strong wifi router or bluetooth transmitter may be transmitting at one or two orders of magnitude greater than the microwave's allowed to leak, but if you're closer to the microwave than the wifi/bluetooth transmitter, or the microwave is simply between you and the wifi/blueooth transmitter, or especially if you have a low power transmitter, that microwave's going to wreak havoc. [1] https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e3.pdf https://transition.fcc.gov/Bureaus/Engineering_Technology/Do...

thomashabets2 3y ago

I used an SDR to check my microwave's emissions. They were pretty narrow and stable-ish. Not stable like an actual radio, but not all over the place wrecking all of the wifi channels. I've not had it interfere with bluetooth or wifi. Bluetooth frequency hops, and moves away from channels with interference (dropped frames), doesn't it? I have a couple of illustrations at https://blog.habets.se/2017/06/Microwave.html https://blog.habets.se/2017/06/Microwave.html

anotherhue 3y ago
> Bluetooth frequency hops, and moves away from channels with interference (dropped frames), doesn't it? Hops yes, remembers to avoid certain channels, maybe. IIRC the hop sequence is controlled by the master device so that might add a layer of confusion if it isn't experiencing the issue. > I used an SDR to check my microwave's emissions. They were pretty narrow and stable-ish. Yes, the issue is it's manufacturing dependent, so a different batch of those same magnetrons the next weeek would have different properties. Hence the wide band.

charles_f 3y ago

I have the same interference with the microwaves at work. There's also a small plaza in what's considered the very center of my city where I get tons of interference (sound basically keeps cutting as if I was losing connection). There's a subway station underground, and some trolley cables suspended in the air, so maybe there's some sort of power converter underground.

ThatMedicIsASpy 3y ago

It destroys the wifi of whatever phone or tablet is next to it while running.

circuit10 3y ago

Relevant XKCD: https://xkcd.com/654/ https://xkcd.com/654/

browningstreet 3y ago

My neighbors have something crazy emanating from their house. None of my Bluetooth devices, from Bose to Plantronic to new AirPods Pro, survive signal connectivity when I walk past their house. The connection gets very disrupted and the devices have trouble reconnecting. So I have to leave everything off when I go for a run and not connect headphones until I make it to the end of the street. It’s weird.

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abdullahkhalids 3y ago
Crazy story that someone at the local radio astronomy observatory told me. Context: Radio observatories need to minimize as much radio interference as possible. Typically, they are some distance away from population, and people are asked not to use phones within a couple of km of them. Inside the premises no unshielded electronics are allowed. If any are used, you can immediately see the effects on the data being collected by the telescope. Anyway, these guys were getting some sort of strong interference signal at 4 pm every day. They could not figure out where it was coming from. They eventually decided that it was not coming from within, but from somewhere outside the observatory. They got some triangulation equipment out and over the course of several days, finally determined that the signal was coming from a house a couple of km away. So they went over and knocked. Asked the owner what was going on. Turned out, the guy had a electric can opener, and every day at 4 pm he would open a can to feed his dogs. That was the interference signal they were getting all the way to the observatory! Eventually, after some back and forth, they got the guy a new can opener they had vetted to not cause an interference signal.
randyrand 3y ago
could be a continuously recording wireless camera that likes to hog spectrum
- browningstreet 3y ago
  I live in deep suburban/exurbs and this feels quite likely, given the neighborhood. Everyone’s wired for cameras and Amazon Key, etc.

AndyMcConachie 3y ago

My bluetooth often dies when I'm near tram tracks and their overhead electric lines in my city. Kind of annoying given that there are tram tracks everywhere.

willsmith72 3y ago

I used to have to time my gaming around when roommates would be eating. Anything in the microwave was an instant dead connection

geocrasher 3y ago

I once had a microwave I called "The WiFi Killer". I work from home, and did then too, and every time one of my kids, or my wife, would use the microwave, I'd get knocked offline. They do work at 2.4Ghz, and this microwave was pretty old. Replaced it and never had another problem.

peterleiser 3y ago

You can demonstrate WiFi interference by putting a laptop next to your microwave and running a ping test to your WiFi router. I can put my laptop about 4 feet away from my microwave and the ping test hangs as soon as the microwave starts. The ping test resumes as soon as the microwave stops.

teeray 3y ago
I haven’t had my afternoon coffee yet, and I read this as though the ping test stops when you put your laptop in the microwave and turn it on.
- TeMPOraL 3y ago
  It should stop as soon as you close the doors, I think, or else RF interference is the least of your problems with the microwave.
- peterleiser 3y ago
  Lol! It's tempting. Very tempting.

magicalhippo 3y ago

One thing is Bluetooth. Imagine spending 4 years trying to figure out the source of some mysterious signals registered by your giant radio telescope, only to find it was due to the microwave[1][2] used by the operators to heat hot pockets or whatever. [1]: https://www.theguardian.com/science/2015/may/05/microwave-oven-caused-mystery-signal-plaguing-radio-telescope-for-17-years https://www.theguardian.com/science/2015/may/05/microwave-ov... [2]: https://www.nature.com/articles/521129f https://www.nature.com/articles/521129f

racl101 3y ago
"Honey! I'm detecting some some major CMB! You gotta see this! Can you pop my lunch outta the micro too?! Thanks!"
- basementcat 3y ago
  I had a colleague who "discovered" a pulsar that later turned out to be a radar at San Francisco International Airport. I occasionally still text them photos of the "pulsar" when I have a layover at SFO.
ethbr1 3y ago
Can I interest you in some land in western Virginia? https://en.wikipedia.org/wiki/United_States_National_Radio_Quiet_Zone https://en.wikipedia.org/wiki/United_States_National_Radio_Q...
klyrs 3y ago
Now I'm imagining a collaboration among radio-astronomers to microwave their lunches at the same time around the globe. Who would set up the prank: grad students making a secret pact at a conference to prank their professors, or vice verse?

tivert 3y ago

In the early days of Wifi, it was pretty common to have your connection drop out whenever someone used the microwave. Both systems use the same frequency band. I assume modern Wifi has gotten better at chugging through the interference (and perhaps microwave-makers better at shielding).

andrewinardeer 3y ago

No, but my reclining chair's motor interferes with the digital signal my TV recieves.

jcrawfordor 3y ago

Bluetooth and WiFi both borrow their spectrum from microwave ovens. It's typical and expected that microwave ovens will cause some interference with other users of the 2.4GHz ISM band that are very nearby. Microwaves operate at very high power levels and are required to be shielded for human safety, but the permissible leakage power is relatively high compared to typical WiFi and Bluetooth devices---there's a simple reason why. From a legal perspective, Bluetooth is essentially pretending to be a microwave oven and making use of the permitted leakage power. This is the cost of the historical regulatory situation that most of these unlicensed radio services use the ISM bands originally allocated for microwave heating. One of the advantages of newer WiFI standards, particularly WiFi 6E, is that they finally change this situation by using the U-NII bands allocated specifically for unlicensed short-range digital communications, rather than for microwave heating. Mind that this is all in the context of US spectrum regulations, although other countries have largely harmonized their approach. I have a lengthier treatment of the topic here: https://computer.rip/2022-04-14-unlicensed-radio.html https://computer.rip/2022-04-14-unlicensed-radio.html

p_l 3y ago
The international allocation of 2.4GHz spectrum for microwaves happened at lobbying of USA, but is global - and exists in order for airplane galleys to be equipped with microwave heaters and be allowed to travel internationally.
- ThePowerOfFuet 3y ago
  Are they actually microwave instead of convection?
  - p_l 3y ago
    Depends on equipment of the plane - the original reasoning for making 2.4GHz the international dumpster spectrum was to install microwaves
    - jbverschoor 3y ago

takinola 3y ago

There's a particular spot on a local highway that interrupts my wireless CarPlay connection if I spend too long in it (eg when traffic is slow). It's right next to an exit with a bunch of buildings (including a hospital) so I'm sure there is some massive emitter in one of those buildings. I'm still at a loss about what could cause that kind of interference inside a major city and still be legal.

KMag 3y ago
MRI?
a_t48 3y ago
Sounds like Berkeley or North Oakland. :) I have the same issue, I never considered Bluetooth interference.
oasisaimlessly 3y ago
WiFi and Bluetooth have basically zero legal protection. FCC Part 15 "this device must accept any interference received, including interference that may cause undesired operation."

Havoc 3y ago

Nope - zero interuptions. Using some cheap ikea microwave.

stringtoint 3y ago

My bluetooth headphones occasionally drop the connection for a moment when I'm standing to my microwave which is warming up food. 2.4GHz after all. Bluetooth and USB 3 don't play along that well either btw.

ajb 3y ago

Tangentially related: knowing they use the same frequency band, I actually used the work microwave oven as a faraday cage for testing our product which used bluetooth. (Close door, observe signal drop behavior). I was bemused to note that you could still connect to a device inside the oven, over short distances... Hopefully the attenuation was sufficient for safety when using it to cook! [ For clarity - the oven wasn't on when I used it as a faraday cage]

riffic 3y ago

microwaves emit RF, heavy concept right?

runjake 3y ago

Nope, this is completely normal. Many commenters are saying microwaves are pretty narrowband. Maybe some are, but I've done spectrum analysis on a few college-dorm-level microwaves in our office with a Wi-Spy and all 3 of these microwaves spam all of the 3 usable 2.4ghz wi-fi channels when cooking. We see similar fun in iMac labs, when they're all (attempting to) use Bluetooth Apple Magic Keyboards at once.

Tommstein 3y ago

In a related question, does anyone know why my Bluetooth earbuds frequently experience brief disruptions when crossing the street at intersections? It happens far too reliably to be a coincidence.

eschneider 3y ago

I once worked for a startup that was trying to stream ads over bluetooth using microwavable foods. It _worked_, but ultimately used too much bandwidth to be practical at the resolutions advertisers wanted.

daveevad 3y ago
That sounds amazing. Are there more details like what sort of ads even?
- pcthrowaway 3y ago
  I agree, technically fascinating, but also... incredibly scummy. As if adtech didn't have enough invasive tools in their arsenal
KMag 3y ago
Can you explain a bit more how this worked? The food item harvested energy from the microwave, and modulated the leaked microwaves/transmitted its own signal to hijack nearby bluetooth audio devices to play audio ads?
- eschneider 3y ago
  Basically, yes.

aetherspawn 3y ago

Yes, my flatmate had a very old 20+ yrs old microwave (the type with a mechanical dial) and when he used it my WiFi would completely drop out until the cooking was done. I bought him a new microwave because I was sick of dropping zoom calls. The modern LG microwave was much better and has virtually no effect on the WiFi.

raminf 3y ago

The 2.4GHz spectrum is shared between Bluetooth and WiFi 802.11b/g. A few years ago, I was doing some work using an Ubertooth-One scanner (https://greatscottgadgets.com/ubertoothone/ https://greatscottgadgets.com/ubertoothone/). It was showing the traffic on different channels. My wife stuck a burrito to warm up in the microwave a room away (30-40 ft). This was with a brand-name model, so presumably properly shielded, etc. Nope. The entire spectrum just went white with noise on all channels. Once the microwave cycle ended, it still took a good 15-30 seconds before the airwaves calmed down and went back to normal traffic.

freedude 3y ago

The microwave became a second class citizen in our kitchen when we got the toaster oven/air fryer combo unit and then was relegated to the garage on top of the fridge. We still use it for popcorn and the occasional hot cocoa and if my coffee gets cold on the weekend I'll wander out there to warm it up. It is almost unneeded. WiFi is better as a result.

bearbin 3y ago

An interesting construction detail of the cheap modern microwave is that it only operates on one half of the mains electric waveform: microwaves use a single high-voltage diode which acts both as half-wave rectifier and voltage doubler. Thus the magnetron only operates for 10 ms in every 20 ms. In theory 2.4 GHz communication protocols can easily time their transmissions to fit in the gaps left by the microwave. 50% bandwidth loss but no other effect. This obviously isn't foolproof in practice, when 2.4 GHz was a thing I remember my WiFi dropping off whenever somebody was nuking some food. But perhaps this might have been a quirk of my Panasonic inverter microwave - which obviously is not the simple standard circuit.

vardump 3y ago

My microwave oven definitely interferes with anything Bluetooth, like headsets etc. Although audio still somewhat works from a laptop upstairs ~30-50 ft away. Anyways, this is normal. Microwave oven generates a lot of 2400-2500 MHz ISM band noise. You're fine.

matthew-wegner 3y ago

I have a waterpik whose motor absolutely obliterates 2.4ghz. I sometimes use it while wearing bluetooth headphones, and music immediately stops. It took me awhile to figure it out (I thought it was my head leaning down and putting a metal pegboard between me and my work machine, but nope).

nmstoker 3y ago

London Underground announcements in certain stations seem to break Bluetooth really frequently. I suspect that at some point, the message is being transmitted by radio and this must be at a frequency that interferes. Also seen on platform WiFi messed up in a similar fashion - this causes the most grief when calling over WiFi kicks in, you make a call only to find it get wrecked the moment they start announcing. Luckily in some stations you actually get a better signal over mobile, so simply turning off WiFi resolves the problem.

lamontcg 3y ago

My waterpik kills bluetooth to my airpods.

nilsherzig 3y ago

Somewhat related, my bluetooth headphones get some static noise when I use my induction oven. On max power ~1900w it disrupts my headphones in a ~2m range haha

chrismorgan 3y ago

Related question: I used to be able to use wifi when my microwave was running. Then one day with no apparent change it started interfering, so that I can no longer use wifi if the microwave is roughly between the two devices connecting over wifi. Of other microwaves I’ve encountered, most haven’t interfered with wifi, but one or two have. Is this a problem?

fbrncci 3y ago

There is this very popular night market where I live, and whenever I drive through a corner of this market, the Bluetooth in my car just stops. I always wondered what this was. There is just so much interference on a square meter.

simne 3y ago

Everyone, who see possible interference from microwave, should ask nearest service and make checks, as this could be manufacturer defect or just leakage of old insulation (rust under paint), and it could be dangerous for health. PS and yes, my friend once found rust hole in old microwave, so this is not very rare thing.

balaji1 3y ago
I have wondered about danger to health. The microwave interference is obvious with the airpods.
- simne 3y ago
  It's not good. May I just fortunate, but I have not seen any problems from old mature manufacturers, like Panasonic. Sure, I mean new microwave, or in absolutely perfect state.

craigdalton 3y ago

Yes, we had an LG microwave, took it back after 3 weeks because it knocked out both wifi and Bluetooth. The store didn't want to refund. Said it had to go to warranty repair. Repair shop said they cannot decrease RF emissions, store begrudgingly gave credit.

cyanydeez 3y ago

Sounds like. A microwave problem

bannanman 3y ago

My microwave sat Infront of a phone jack. (we had ADSL2 for internet) Every so often out internet would just stop. Finally realized it was the microwave pumping interference into the jack it took out the internet. Also worth noting, if it was a bad rain storm the internet would drop in speed.