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| Microwave oven PWM frequency |
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| John Heath:
I can see there are more than a few who are not buying the microwave oven problem in the 802 IEEE standards for WIFI , XBEE and blue tooth. I can understand why as you would think they would be smart enough to separate 1000 watt microwave oven frequency from .1 watt communication frequencies. Sadly they did not separate them. Even Sadder if it is your phone that rings when computer communications are down. |
| tooki:
--- Quote from: Red Squirrel on February 13, 2018, 03:14:21 am ---Technically your wifi should not be affected by the microwave. I don't know how good of a test this is but I did a ping -f to my phone's IP and microwaved a glass of water on high with phone sitting next to the microwave and I had no packet loss. --- End quote --- I suspect it depends on several things: 1) the selected WiFi channel 2) the specific microwave oven model 3) the relative location of the WiFi router and the microwave The last, in particular, I’ve found to make a huge difference: if the microwave oven is between the router and the client, performance will suffer (sometimes to the point of not functioning at all). I just experienced this at a friend’s house. If they’re equidistant but in different directions, it usually works fine. --- Quote from: John Heath on February 13, 2018, 09:31:28 am ---I can see there are more than a few who are not buying the microwave oven problem in the 802 IEEE standards for WIFI , XBEE and blue tooth. --- End quote --- Yeah, I dunno. I’ve experienced it enough times firsthand to know it’s a real problem. That said, I’m still waiting for documentation about these laws you’re claiming. --- Quote from: John Heath on February 13, 2018, 09:31:28 am ---I can understand why as you would think they would be smart enough to separate 1000 watt microwave oven frequency from .1 watt communication frequencies. Sadly they did not separate them. --- End quote --- I already explained to you why they’re on the same band. It’s not random coincidence! --- Quote from: John Heath on February 13, 2018, 09:31:28 am ---Even Sadder if it is your phone that rings when computer communications are down. --- End quote --- Huh what? |
| richard.cs:
There is a microwave oven avoidance mode in one of the WiFi specs, I think it just keeps the packet lengths down to 8 ms or something relatively simple like that. Note that this is taking advantage of microwave ovens running with half-wave rectified power, but it's not the reason they work that way. Microwave ovens do that because it's cheap. The magnetron produces a fairly pure single frequency tone, but with a weak voltage dependence to it sweeps in frequency during the (slightly less than) half a cycle that it's active and this makes it more interfering than might be expected. The one dual-magnetron microwave I've had apart runs them on opposing half-cycles. I suspect that this is both to clean up the input current waveform a bit but also to prevent them from injection locking - if they end up locking in frequency you get a single standing wave pattern and the cooking is no more even than a single magnetron microwave (which is one of the alleged advantages). This means that at full power there is minimal dead time. Interference with WifFi is certainly a real effect, I have a pretty little graph of WiFi data transfer rate against time where you can see the effect of my microwave when on 50% power, the low-frequency PWM is visible in the data rate. This should be entirely expected given that the shielding on a microwave oven often only gives about 30 dB attenuation so gives leakage on the order of a Watt. |
| John Heath:
There is also the crowding of WIFI channels. Each year it gets worse. As much as 50 WIFIs all frequency hopping trying to sneak a byte or 2 through a limited shared number of channels. There are free apps for cell phones to monitors how crowded it is. There is also the window problem if you need to go building to building. Not sure why but there are some types of glass used in windows that acts like a mirror at 2.4 GHz. You can be better off trying to penetrate a brick wall than a glass window. 5 GHz does not help. |
| Psi:
Microwaves that control the power level by ~0.25 HZ pwm are pretty annoying. I would recommend replacing it with an inverter microwave. When you need to warm up something slowly, like on 'low power' the pulses of full power usually burn/cook it instead. A good example is anything with egg in it, like warming up hollandaise sauce, it's almost impossible to not ruin it. But with an inverter oven you don't get these problems. |
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