Ask HN: Does your microwave interfere with Bluetooth? Mine does • Hacker News Board

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

#91

Post by ethbr1 » Thu, Oct 05, 2023, 9:16 PM UTC

jcrawfordor wrote: post #74

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…

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.

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

#92

Post by ThePowerOfFuet » Thu, Oct 05, 2023, 9:18 PM UTC

p_l wrote: post #79

jcrawfordor wrote: post #74

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…

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.

Are they actually microwave instead of convection?

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

#93

Post by p_l » Thu, Oct 05, 2023, 9:19 PM UTC

ThePowerOfFuet wrote: post #92

p_l wrote: post #79

Earlier quoted context omitted.

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.

Are they actually microwave instead of convection?

Depends on equipment of the plane - the original reasoning for making 2.4GHz the international dumpster spectrum was to install microwaves

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

#94

Post by racl101 » Thu, Oct 05, 2023, 9:20 PM UTC

magicalhippo wrote: post #66

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

"Honey! I'm detecting some some major CMB! You gotta see this! Can you pop my lunch outta the micro too?! Thanks!"

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

#95

Post by nkerkin » Thu, Oct 05, 2023, 9:26 PM UTC

liminalsunset wrote: post #69

kpozin wrote: post #12

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.)

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.

I have one, and yes, much interference.

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

#96

Post by eschneider » Thu, Oct 05, 2023, 9:29 PM UTC

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.

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

#97

Post by ethbr1 » Thu, Oct 05, 2023, 9:31 PM UTC

mikewarot wrote: post #3

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.

> 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 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...

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

#98

Post by ethbr1 » Thu, Oct 05, 2023, 9:34 PM UTC

magicalhippo wrote: post #66

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

Can I interest you in some land in western Virginia?

https://en.wikipedia.org/wiki/United_States_National_Radio_Q...

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

#99

Post by aetherspawn » Thu, Oct 05, 2023, 9:36 PM UTC

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.

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

#100

Post by jbverschoor » Thu, Oct 05, 2023, 9:38 PM UTC

p_l wrote: post #93

ThePowerOfFuet wrote: post #92

Earlier quoted context omitted.

Are they actually microwave instead of convection?

Depends on equipment of the plane - the original reasoning for making 2.4GHz the international dumpster spectrum was to install microwaves

But we need to switch off WiFi and Bluetooth