[Retric]

> The same reason the metal grid works is why there doesn't need to be a perfect door seal. As long as as the gap is smaller than the wavelength of the microwaves, it's fine.

The issue is the gap in a door normally forms a long line.

The fact they interfere with WiFi should make it obvious the average microwaves faraday cage is far from perfect.

[dhdc]

The point of a microwave to have a faraday cage is not for preventing interference with wifi; the cage is there for preventing the microwave microwaving the user. At an average power of 1000W, even a thousand-fold attenuation (-30dB) means 1 watt/30dBm leaks out, minuscule for humans but enough to saturate typical wifi receivers.

[Retric]

The cage was originally there to make them more efficient, spraying microwaves into the room would mean you food takes a lot longer to cook.

Anyway, I don’t recall all the details but 1W from a microwave is probably an underestimate.

WiFi uses multiple separate frequencies and outside of what a microwave should be producing. So it’s significantly more energy to block it than you might think especially when the hub is closer to the device than the microwave.

PS: To be clear this is still a trivial amount of energy, just annoying when reheating food blocks WiFi.

[ganzuul]

> A Federal standard (21 CFR 1030.10) limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface.

So you were off by a factor of 200, and you can see that my referencing -40dB of attenuation was an underestimate. I do wonder what details it was that you thought you might recall.

Quite disappointed by HN standards of self-moderation yet again.

[Retric]

You’re way off, that’s 5 milliwatts per square cm times the surface area.

A 1 foot cube, has 6 faces of ~30 cm * 30 cm or 5,400 cm2. 5,400cm2 * 5mw = 27 watts. Of course 2 inches from the surface is a significantly larger box.

Of course that’s a legal maximum, most devices should be well below it.

[ganzuul]

You can melt stuff with 27W. Doesn't pass the smell test.

[Retric]

Sunlight is 93w/square foot, this would be under 4.5w/square foot good luck melting something at room temperature with that. I think you have a poor intuition about the difference between point sources and energy across an area.

Anyway, math is math but presumably this is why that’s the legal limit. It’s low enough to be safe while high enough not to be expensive for manufactures.