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

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

#112

Earlier quoted context omitted.

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…

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)

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.

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

#113

Earlier quoted context omitted.

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)

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.

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.

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

#114
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.)

GE inverter microwave with interference 20-30ft away and it goes through a wall.

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

#115

Earlier quoted context omitted.

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.

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.

Cool, I just thought I was missing out on something. :-)

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

#116
post #78
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.)

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.

Oh no. Is that something that happens? Mine has smelled a little like metallic smoke lately.

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

#117
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.

it's kind of funny because water resonates in that band, international consensus or not?

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.

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

#118
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.

it's kind of funny because water resonates in that band, international consensus or not?

It’s a myth, see the Wikipedia link in an above comment.

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

#119
post #97

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.stackexch…

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.

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

#120
post #84

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.

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.

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.
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