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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

#61
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.)

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.

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

#62
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.

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

#63

Earlier quoted context omitted.

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.

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)

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

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

#64

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.

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.

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

#65
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.

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

#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

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

#67
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).

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

#68

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.

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.

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

#69
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.

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

#70
post #24

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…

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 an…

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...

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