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Test Microwave for Radiation Leakage

ismymicrowaveleaking.isotropic.us

91–100 of 110 posts

Re: Test Microwave for Radiation Leakage

#91

Idk if OP is the person who wrote this, but on my device the red text about not turning the microwave on is not especially legible. I’d probably make that text a bit bigger and/or brighter. I expect most HN readers will know not to microwave a phone but you’d be surprised what people might do.

In dark mode it’s very legible. I expect most people know not to microwave their phones except maybe children.

I wouldn't count on that: many things that seem straightforward, especially to an adult tech-savvy person if those things are tech-related, are far from that for others. And even tech-savvy people can be (and often are) careless, distracted/preoccupied/unfocused, making mistakes; I think pressing a "start" button automatically upon closing the door is something that can happen easily. Also as a rule, extra guards, safety measures, and/or warnings are good, especially when irreversible damage can happen.

Edit: actually there's an example of an unexpected mistake in this thread already, in the comment by hanoz. As mentioned before, listing unplugging as the first step would be useful.

Re: Test Microwave for Radiation Leakage

#92

Earlier quoted context omitted.

thats an awful feature

It is pretty convenient as long as you aren't putting cell phones into it.

The screening/Faraday cage will still work with the mains power disconnected, so one should ensure the mains plug is removed before such a test.

Note: I'm a past master at destroying old electronics in my microvave (this way I can't change my mind later and then not throw it out).

About three seconds is all it takes (just time for the magnetron filament to warm up) - any longer and the stuff starts to stink from the heat. There's no second chance if you make a mistake.

Re: Test Microwave for Radiation Leakage

#93

Idk if OP is the person who wrote this, but on my device the red text about not turning the microwave on is not especially legible. I’d probably make that text a bit bigger and/or brighter. I expect most HN readers will know not to microwave a phone but you’d be surprised what people might do.

In dark mode it’s very legible. I expect most people know not to microwave their phones except maybe children.

> I expect most people know not to microwave their phones

I think you're vastly underestimating how little people know. A friendly FYI: seems you're in some kind of a bubble.

Personally I didn't learn about don't-microwave-metal (incl phones), until I was about 20 -- and at that time, I had already been studying physics at university for a year, and knew vastly much more than what most people ever will. I wouldn't say I was a child, at that time.

Be happy if people in general realize that photons and coronavirus aren't the same thing, although they're both small.

Re: Test Microwave for Radiation Leakage

#94

Earlier quoted context omitted.

It is pretty convenient as long as you aren't putting cell phones into it.

The screening/Faraday cage will still work with the mains power disconnected, so one should ensure the mains plug is removed before such a test. Note: I'm a past master at destroying old electronics in my microvave (this way I can't change my mind later and then not throw it out). About three seconds is all it takes (just time for the magnetron filament to warm up) - any longer and the stuff starts to stink from the…

This seems like an odd way to destroy electronics. What's wrong with a hammer?

Re: Test Microwave for Radiation Leakage

#95
post #89
post #57

Earlier quoted context omitted.

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…

> 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. Qu…

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.

Re: Test Microwave for Radiation Leakage

#96
post #33

Earlier quoted context omitted.

a cheap consumer RF meter detects "high" levels of RF from 5+ feet away, at least on the 4 or 5 random units I've tried. So the faraday cage doesn't seem to be doing its job in full.

A "high" from a random RF meter doesn't mean anything. Give me numbers in dBm/MHz.

No post body was provided.

Re: Test Microwave for Radiation Leakage

#97

Earlier quoted context omitted.

The screening/Faraday cage will still work with the mains power disconnected, so one should ensure the mains plug is removed before such a test. Note: I'm a past master at destroying old electronics in my microvave (this way I can't change my mind later and then not throw it out). About three seconds is all it takes (just time for the magnetron filament to warm up) - any longer and the stuff starts to stink from the…

This seems like an odd way to destroy electronics. What's wrong with a hammer?

It's quick and easy and less dangerous (and more final) than a hammer!

I've been known to change my mind half way through destroying something when I think of another use for it - the microwave method ensures that the part of me that doesn't like throwing out electronic things that still work always gets thwarted.

The idea of microwaving electronics came to me a long while ago for very different reasons. In the early days of microcomputer control systems I used to work with Intel Multibus computer systems (these are so old you better check this Wiki out to know what I'm talking about: https://en.m.wikipedia.org/wiki/Multibus).

In those days Multibus boards were hellishly expensive and we used quite a lot of them. If one went faulty then we either fixed it at board level or if it failed within the warranty period then we returned it to the agent who then had it fixed (boards were always repaired - never thrown away).

Anyway, one board we received had an intermittent fault and I had it returned under warranty and the agent supposedly fixed it and returned it but it was still intermittent (you know, it had one of those annoying intermittents that was rare enough for one to think the problem was fixed when it wasn't). This toing and froing to the agent occurred at least three times and the problem still wasn't solved so I put an end to it by putting the board in the department's lunchroom microwave.

The plan was to damage a sufficient number of ICs to render the board beyond economic repair (BER) but not make the matter of microwaving it obvious to the supplier. This was very successful, a new board with a different serial number was supplied and the intermittent problem disappead.

To accomplish a truly defective board without obvious signs of user 'abuse' requires some care. The aim is to provide just sufficient microwave energy to puncture or short-circuit the junctions in the ICs but to not make it obvious (in practice, about one second of RF is needed to accomplish this).

Excessive RF will heat the silicon to the point where it boils the ICs' encapsulating compound and one ends up with little craters in the middle of the ICs which make it obvious the board's been zapped.

Most microwave ovens take about 3 seconds before any RF appears (no RF will appear until the magnetron cathode is hot enough to become emissive), so it's important to calibrate your oven before embarking on such an exercise.

I've used this technique very effectivly a number of times over the years. I must mention another incident long after the first, however this one had nothing to do with Multibus.

It involved a setup jig for programming certain electronic equipment and its motherboard was about as complex as a Multibus one. When motherboards failed I either fixed them or returned them to the manufacturer's repairer who was in a third country (he was renowned for fixing dead boards that people like me considered BER).

Again, we had an intermittent board that had crossed the oceans a number of times and it was still intermittent so I finally gave it the microwave treatment and returned it to him. Right, this silly bugger actually wasn't going to let it defeat him, he returned the board to me with a message to the effect 'this was a very problematic board, I had to replace about half the ICs [about 50 total per board], seems it was hit by a lightening surge'. Well, the board worked - sort of - but it had new and different intermittents (presumably, some of the ICs he'd not replaced were suffering breakdown puncture in their SiO2 insulation and thus were experiencing partial failures).

I returned the board again without any extra zaping and this time it was replaced with a different one (presumably, he'd either given up on it or wasn't prepared for my wrath when or if it failed again).

BTW, one can get pretty good at this if you calibrate your microwave carefully. Such zapping should never exceed nuking more than about 25% of the ICs. This is usually sufficient to deter most diehard repairers whilst not drawing their attention to the actual cause of the failure.

Re: Test Microwave for Radiation Leakage

#98

Earlier quoted context omitted.

I strongly disagree. If you are idiot enough to microwave your own phone, that's on you. This post is fine, and interesting.

Calling people idiots for making mistakes is about the most boring thing I can imagine. I agree it shouldn’t be deleted, and that it’s interesting. But everyone flubs it from time to time, even people who like to think they’re above that.

There is a difference between making an understandable mistake and doing something that should make you ashamed for being that dumb.

Nuking your phone in the microwave is in the same category as baking it in the oven. You really shouldn't be surprised when you don't have a working phone anymore.

I don't think it is wrong of us to expect better from a bunch of adults. They should know better.

Re: Test Microwave for Radiation Leakage

#99

Earlier quoted context omitted.

This seems like an odd way to destroy electronics. What's wrong with a hammer?

It's quick and easy and less dangerous (and more final) than a hammer! I've been known to change my mind half way through destroying something when I think of another use for it - the microwave method ensures that the part of me that doesn't like throwing out electronic things that still work always gets thwarted. The idea of microwaving electronics came to me a long while ago for very different reasons. In the early…

Fair enough! Personally, when I reuse broken electronics, it's often because I'm scavenging more mechanical parts like ports and switches. I think those would tend to survive either method, as long as you're not utterly destroying the device.

Re: Test Microwave for Radiation Leakage

#100

Earlier quoted context omitted.

I keep hearing that for Faraday cages but its not clear to me why. Why should it be grounded? The cell signal in the Faraday cage causes a mirror signal on the cages inner surface and the cage’s conductivity ensures that the potential is zero elsewhere in the cage. Why do I need the ground? Is it a consequence of not having a perfect conductor?

The case itself becomes an antenna if it's not and just re-resonates the signal.

Does it though? At what frequency? In the limit of f=DC this is trivially not true.

Also, if that were the case, an airplane couldn't be made into a Faraday cage.

Also, the cage+Earth system would itself be an antenna.

If you need ground for a topologically imperfect cage, maybe… but I doubt it.

I think (but I don't know!) this is like the legends surrounding engine torque car guys believe. Electrical engineers putting everything to ground because they got burned

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