[HN Gopher] Ask HN: Does your microwave interfere with Bluetooth...
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Ask HN: Does your microwave interfere with Bluetooth? Mine does
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?
Author : Jeff_Brown
Score : 80 points
Date : 2023-10-05 12:47 UTC (10 hours ago)
| riffic wrote:
| microwaves emit RF, heavy concept right?
| freitzkriesler2 wrote:
| 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.
| gumby wrote:
| 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.
| aetherspawn wrote:
| 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.
| Ellipsis753 wrote:
| Yep. I've seen Bluetooth be affected by microwaves. Also seen
| WiFi be affected by Bluetooth. It doesn't mean your microwave is
| unsafe.
| runjake wrote:
| 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 wrote:
| 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.
| Eumenes wrote:
| 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 wrote:
| If that isn't a design feature, may be time for a new microwave
| friend.
| thomashabets2 wrote:
| 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
| anotherhue wrote:
| > 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.
| senectus1 wrote:
| nope.
|
| Had that happen once, swapped the microwave out and never
| happened again since.
| browningstreet wrote:
| 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.
| randyrand wrote:
| could be a continuously recording wireless camera that likes to
| hog spectrum
| browningstreet wrote:
| I live in deep suburban/exurbs and this feels quite likely,
| given the neighborhood. Everyone's wired for cameras and
| Amazon Key, etc.
| abdullahkhalids wrote:
| 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.
| xattt wrote:
| Sometimes it's things like baby monitors or low-cost cameras
| blasting analogue video.
| [deleted]
| Havoc wrote:
| The same can also be very localized. On my way to work there is
| a 2x2m spot in the middle of open space that does that too
| kiltedpanda wrote:
| Sounds like they have something pretty powerful swamping out
| that band.
|
| Even though the ISM (2.4 GHz) band is unlicensed, there are
| still regulatory limits to the maximum emission levels. Devices
| that exceed those levels are illegal to use. The FCC can apply
| hefty fines in certain cases.
|
| Fun story, I used to live in an apartment building and my car
| key fob wouldn't work when I parked close to the building. It
| would work on the other side of the parking lot though. Turns
| out someone was using a jammer because they hated the noise
| that cars make when they lock and unlock. They tried to blame a
| nearby military base, but I had some RF test gear and located
| the culprit. They turned it off pretty quick when I showed that
| they could be fined $10k per day.
| circuit10 wrote:
| Relevant XKCD: https://xkcd.com/654/
| andrewinardeer wrote:
| No, but my reclining chair's motor interferes with the digital
| signal my TV recieves.
| charles_f wrote:
| 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.
| crazygringo wrote:
| 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 wrote:
| 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.
| baal80spam wrote:
| Yes, sound in my headphones is distorted when I go near a working
| microwave oven.
| jraph wrote:
| 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 wrote:
| 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).
| kevinherron wrote:
| Not great, not terrible.
| ThatMedicIsASpy wrote:
| It destroys the wifi of whatever phone or tablet is next to it
| while running.
| counterpartyrsk wrote:
| Does the sound quality improve if either the phone or speaker are
| inside the microwave? We must test all possible scenarios.
| zzless wrote:
| 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 wrote:
| 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
| raminf wrote:
| 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/). 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.
| AndyMcConachie wrote:
| 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.
| vardump wrote:
| 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.
| takinola wrote:
| 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 wrote:
| MRI?
| mikewarot wrote:
| 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.
| NikkiA wrote:
| If it's an old microwave replacing the door seal would be
| cheaper and easier.
| anotherhue wrote:
| > 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.
| H8crilA wrote:
| 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 wrote:
| >but I don't have a microwave :)
|
| Living the dream!
| ethbr1 wrote:
| > _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-fa...
| itishappy wrote:
| > 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
| kiltedpanda wrote:
| 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.
| jrockway wrote:
| 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 wrote:
| 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 wrote:
| 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.
| function_seven wrote:
| Wow. I have no idea how I confused that.
|
| Yeah, the WiFi is improved. The Bluetooth is the same as
| it ever was.
|
| I pardon your confusion.
| mikestew wrote:
| Cool, I just thought I was missing out on something. :-)
| [deleted]
| TnRHL wrote:
| I think microwaves ovens are allowed to emit up to 1W of energy.
| As mikewarot said - it's amazing Wifi/BT works at all.
| freedude wrote:
| 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.
| trey-jones wrote:
| 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.
| regularfry wrote:
| Office microwaves (assuming it's not just a retail one that
| happens to be in an office) can be overpowered. Think the last
| one I was near was a 2.5kW unit.
| mschuster91 wrote:
| Good lord, who uses that much power in a microwave? 600W are
| enough.
|
| (Clearly, the idiots microwaving fish in them. In one office
| I know they put a sticker with a crossed-through fish symbol
| after one particularly pungent incident)
| freedomben wrote:
| Yes 600W are enough, but I once had a 1750W microwave and
| it was luxurious and ridiculously fast at warming. I would
| pop a bad of popcorn in like 30 seconds, or warm up a slice
| of pizza in 15 seconds. Makes me think like the difference
| between a Camaro and a Geo Metro
| TeMPOraL wrote:
| > _Good lord, who uses that much power in a microwave? 600W
| are enough._
|
| And next thing you'll say is that 1000W is enough for a
| kettle? 110V 15A AC is enough for an outlet?
|
| Here in Europe, we don't have the patience for slow-boil
| kettles and slow-boil microwaves :).
|
| (FWIW, I always stick to the full 1000W available on my
| microwave, and sorely miss the 1250W that my dad brought
| from Sweden when I was a kid.)
| ta1243 wrote:
| My headphones are fine, and the battery doesn't drop out either
| -- this 3.5mm cable is great.
| saiya-jin wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| >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 :|
| trey-jones wrote:
| I am also a get-up-and-pacer, and agree with your
| reasoning completely.
| warrenm wrote:
| I pace, too .. but not if I'm using a desktop - only when
| on the phone (and occasionally) with a laptop
| aimor wrote:
| You can build a "lectenna" and see where your microwave is
| leaking energy out.
|
| https://www.youtube.com/watch?v=V5SMF9p-4Q0
| causi wrote:
| 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.
| bearbin wrote:
| 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.
| baz00 wrote:
| My neighbour's microwave nukes my bluetooth entirely. I have
| moved to wired everything and life is good finally!
| jrs235 wrote:
| 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.
| ajb wrote:
| 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]
| zh3 wrote:
| 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 wrote:
| Where are you getting 2.5? 2450 +/- 50 is what I have seen.
| peterleiser wrote:
| 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 wrote:
| 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 wrote:
| 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.
| adrianmonk wrote:
| That's inconvenient, but it's definitely expected.
|
| From 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.
| magicalhippo wrote:
| 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-
| ov...
|
| [2]: https://www.nature.com/articles/521129f
| racl101 wrote:
| "Honey! I'm detecting some some major CMB! You gotta see this!
| Can you pop my lunch outta the micro too?! Thanks!"
| ethbr1 wrote:
| Can I interest you in some land in western Virginia?
|
| https://en.wikipedia.org/wiki/United_States_National_Radio_Q...
| TheAceOfHearts wrote:
| 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.
| Havoc wrote:
| Nope - zero interuptions. Using some cheap ikea microwave.
| vehemenz wrote:
| 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 wrote:
| Same. Airprods Pro are the first product i've ever used that
| experienced microwave interference.
| stringtoint wrote:
| 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.
| hulitu wrote:
| > Ask HN: Does your microwave interfere with Bluetooth? Mine does
|
| As far as i know you can make a complain by the FCC.
| willsmith72 wrote:
| I used to have to time my gaming around when roommates would be
| eating. Anything in the microwave was an instant dead connection
| eschneider wrote:
| 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 wrote:
| That sounds amazing. Are there more details like what sort of
| ads even?
| KMag wrote:
| 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?
| float4 wrote:
| 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.
| pi-rat wrote:
| 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 wrote:
| Would probably have been enough to change the wifi channel.
| geocrasher wrote:
| 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.
| Fnoord wrote:
| 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 wrote:
| 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 wrote:
| 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-
| tom...
| crazygringo wrote:
| 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.
| jcrawfordor wrote:
| 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
| p_l wrote:
| 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 wrote:
| Are they actually microwave instead of convection?
| p_l wrote:
| Depends on equipment of the plane - the original reasoning
| for making 2.4GHz the international dumpster spectrum was
| to install microwaves
| jbverschoor wrote:
| But we need to switch off WiFi and Bluetooth
| p_l wrote:
| That's because the equipment installed in the galley is
| going to be tested for operation with the specific
| aircraft.
|
| Meanwhile _phone_ radios (not WiFi, not Bluetooth) used
| to have interference issues with various aviation systems
| (with some 5G bands still causing issues).
|
| Additionally, outside of interference issues from _phone_
| systems (and various other non-ISM band radios), the
| order helps preventing people from doing stupid things
| with electronics during takeoff and landing, where sudden
| deceleration can cause things to go awry.
| jjtheblunt wrote:
| it's kind of funny because water resonates in that band,
| international consensus or not?
| Hello71 wrote:
| https://en.wikipedia.org/wiki/List_of_common_misconceptions
| :
|
| > Microwave ovens are not tuned to any specific resonance
| frequency for water molecules in the food, but rather
| produce a broad spectrum of frequencies, cooking food via
| dielectric heating of polar molecules, including water.
| Several absorption peaks for water lie within the microwave
| range, and while it is true that these peaks are caused by
| quantization of molecular energy levels corresponding to a
| single frequency, water absorbs radiation across the entire
| microwave spectrum.
| jcrawfordor wrote:
| I would contest Wikipedia's description here a bit
| because I think it confuses the issue of microwave
| emissions. A number of ISM bands were allocated for RF
| heating applications originally, 6.78MHz, 13.560MHz,
| 27.12MHz, 40.68MHz, 915MHz (commonly referred to as
| 900MHz), 2.45GHz (commonly referred to as 2.4GHz),
| 61.25GHz, 122.5GHz. These are just examples taken from my
| NTIA chart which doesn't call all of them out.
|
| The lower ones are largely historic, the very first RF
| heating experiments used HF and VHF low band which were
| easier to produce with the radio transmitter technology
| of the time, but not very efficient at all. The invention
| of the magnetron changed that, suddenly it was much
| easier to produce microwave radiation at high power
| levels, and so the inefficient HF/VHF RF heating devices
| have all but faded away (there are some specific
| technical applications that remain exceptions, as usual).
|
| The low frequencies are inefficient and difficult to
| produce with compact electronics, the high frequencies
| aren't very attractive for food heating applications
| because of the limited skin depth. So every microwave
| oven you're likely to run into operates at 2.4GHz, which
| is pretty much the sweet spot for food heating _among the
| allocated ISM bands_. That band is defined as 2.4GHz
| through 2.5GHz. So I quibble with describing microwaves
| as "broad spectrum." Magnetrons do not produce very
| narrow output, one of the reasons they aren't often used
| for radio transmitters today, but microwave ovens are
| required to constrain their meaningful output to within
| 50MHz of 2.45GHz. 100MHz is a _lot_ of bandwidth from a
| modern radio communications perspective, but isn 't
| really that wide from a perspective of physical effects.
|
| 2.45GHz was chosen as an ISM band in part because it had
| good properties for heating, but it wasn't put exactly on
| a resonance frequency for water or anything like that.
| The exact details of the selection process are obscure
| but 2.45GHz was already being used for experimental
| microwave heating before the ISM band was allocated, and
| I would imagine came out of some combination of ease of
| magnetron construction and reasonably good heating
| properties. It is documented, for example, that the EHF
| bands were never popular for consumer microwave heating
| because of poor efficacy with food, although they do have
| industrial applications (especially in welding).
|
| Given the history of the topic there's a decent chance
| that 2.45GHz came about because it was being used by
| experimental radar at the time, the main thing that
| magnetrons were being built for. Microwave heating was
| basically a byproduct of radar development during its
| early days of development.
| ahoka wrote:
| It's a myth, see the Wikipedia link in an above comment.
| ethbr1 wrote:
| And on the follow-up, "Why use 2.4(5) GHz for microwaves?"
|
| Because it happens to be a convenient frequency that water
| absorbs readily, which is the easiest way of heating up what
| we'd want to heat with a microwave (read: food).
|
| https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_...
|
| And once we'd polluted the frequency for any stable commercial
| use, why not use this weird carve-out for a little thing called
| WiFi?
|
| Rabbit hole: Apparently the precise mechanics of EM heating of
| molecules are surprisingly complex, and offer a number of
| frequency options. But this would have been the 1950s(?), so
| I'd assume they empirically determined a balance of
| functionality + technical feasibility for water, called it a
| lunch, and went to have five martinis in a practical fashion.
| tivert wrote:
| 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).
| vel0city wrote:
| 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.
| eosophos wrote:
| 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 wrote:
| "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/Do...
| gertlex wrote:
| 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.
| kpozin wrote:
| 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.)
| liminalsunset wrote:
| 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 wrote:
| I have one, and yes, much interference.
| lathiat wrote:
| 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.
| xattt wrote:
| I know of at least two Panasonic inverter microwaves that
| failed within a 5 year period of ownership.
|
| Mine emitted white smoke warming up some tea while I was in
| another room. I hope to God it wasn't beryllium.
|
| I still have a Panasonic OTR microwave, but it's inverterless.
| It appears to be an improved design of a GE model from the same
| OEM.
| Jeff_Brown wrote:
| Oh Christ. Mine has smelled a little like metallic smoke
| lately.
| instagib wrote:
| GE inverter microwave with interference 20-30ft away and it
| goes through a wall.
| callalex wrote:
| 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.
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