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Wi-Fi Cards Can Now Detect Microwave Ovens

timothy posted about 2 years ago | from the now-how-much-would-you-pay? dept.

Wireless Networking 124

An anonymous reader writes "Researchers at UW Madison have used regular WiFi cards to detect non-WiFi interference sources like microwave ovens, Bluetooth devices, cordless phones, Xbox controllers and video cameras. They call their software Airshark. Current products like Wispy, Spectrum Expert are expensive and need extra hardware, whereas Airshark is a software-only solution that can directly work on the Wi-Fi cards on your laptops and APs. This also paves way several interesting applications. For example, your WiFi network will not be affected anymore just because your neighbor switched on a microwave oven or a cordless phone — the newer WiFi APs will be able to switch the channels and adapt to the interference accordingly."

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124 comments

You must live in the boonies (1)

Anonymous Coward | about 2 years ago | (#37504882)

If you live in a city or in the suburbs, you can see LOTS of WiFi access points already, so switching to a different frequency won't get you to an interference free channel! Maybe you'll get to a little less populated one, but not interference free!

Re:You must live in the boonies (0)

Anonymous Coward | about 2 years ago | (#37504952)

I live in the boonies. I don't like nosy neighbors, or people in general. I can't even see another router on my scan. And I can grow pot in relative seclusion. The only thing I miss is being able to walk down to the gas station for more beer after I've already had too much to drive!

Re:You must live in the boonies (1)

sycodon (149926) | more than 2 years ago | (#37506138)

My microwave is always running off. This should make it easier for me to find it.

Re:You must live in the boonies (1)

rgbatduke (1231380) | more than 2 years ago | (#37507468)

Ah, AC, you sly devil. So that's where you got off to, when you left the less-anonymous city.

Down here in NC folks have several good solutions to the beer problem, including making their own (which is way, way better than the beer you can get in any gas station in the boonies unless for you US corporate beer is the epitome of corn-flavored goodness) or saying screw the beer and turning their malted corn directly into an untempered distilled spirit, made (as you say) in relative seclusion. I can only guess that you live in the northern boonies.

Of course, true boonie-dwellers in NC often eschew newfangled contraptions like wi-fi, cell phones, phones, microwave ovens, and computers, and only use electricity to run their well-pump and refrigerator and lights. They often cook whole pigs or vats of deer, squirrel, and groundhog into a thick nourishing stew and aren't averse to using the occasional revenuer or overly nosy neighbor (seeking to unrighteously rip-off some of that pot) as mulch for their barley or corn crop. Occasionally they can spell and still have all of their teeth. But we don't often hear from them on /.

rgb

Re:You must live in the boonies (1)

mattventura (1408229) | about 2 years ago | (#37505112)

Or use 5 or 5.8ghz. Even if there are tons of devices, it has many times more spectrum than the 802.11b/g band.

Re:You must live in the boonies (1)

Dogtanian (588974) | more than 2 years ago | (#37505234)

Or use 5 or 5.8ghz. Even if there are tons of devices, it has many times more spectrum than the 802.11b/g band.

What's the deal with 802.11n and the 5 GHz band? I've seen a lot of N equipment that only seems to support the 2.4 GHz band- I'm guessing because it's cheaper to only have one radio?- so is is the case that N equipment doesn't *have* to support 5 GHz? (*)

At any rate, it sounds like buying 5 GHz-supporting N equipment would be worth the extra money. I made sure my first router and card (circa 2005) supported 802.11a even though it cost more because I suspected congestion might become a problem and the less-popular A used.... 5 GHz. (Wireless was just starting to become mass-market popular at that point). Didn't need it as it happens, but I'd still use the same strategy again if I could.

(*) Guess in theory they could make a single-radio 5 GHz only version, but since that wouldn't be backward-compatible with all the B and G (i.e. 2.4 GHz) equipment out there, people probably wouldn't like that.

Re:You must live in the boonies (1)

bemymonkey (1244086) | more than 2 years ago | (#37506572)

Yup, cheapo 802.11n stuff doesn't support 5GHz. The only reason I'm still running 2.4GHz is my Android smartphone... stupid cheapo Broadcom BCM4329 doesn't support 5GHz.

At least all my Thinkpads support 5GHz and the router's dual band...

I can definitely recommend going with 5GHz if you don't need all too much range (through walls and such) and the airwaves around 2.4GHz are crowded in your neighborhood.

Look at this crap... my neighborhood at 2.4GHz: http://dl.dropbox.com/u/7086491/pictures/2.4ghz.PNG [dropbox.com]

And 5GHz: http://dl.dropbox.com/u/7086491/pictures/5ghz.PNG [dropbox.com]

The non-blue bars are other networks and interference from other networks. Crazy huh? Thank God I'm the only one around here who's discovered 5GHz so far ;)

If only all wifi devices could work cooperatively (4, Interesting)

Skinkie (815924) | about 2 years ago | (#37504910)

Then the entire spectrum problem is solved, and everything would be autoconfigured for the basic paradigm: connectivity. Now I don't expect a microwave to give me food-over-ip, but I would expect a neighbor wifi cell, helping my AP to extend the signal, if my client would move out of range (aka: has more noise).

Re:If only all wifi devices could work cooperative (2)

morcego (260031) | about 2 years ago | (#37504970)

The technology allows for this already. However, the security and privacy implications are big. Not to mention bandwidth limitations. And switching capability. And routing tables. And ARP tables. And those are the problems I though about while typing this. I'm sure there are several others.

Re:If only all wifi devices could work cooperative (1)

Zorpheus (857617) | more than 2 years ago | (#37505226)

Not an expert on this, but couldn't the other hub just relay the encrypted signal, without dectrypting it? Then there is no security problem.

Re:If only all wifi devices could work cooperative (1)

morcego (260031) | more than 2 years ago | (#37505480)

You are talking about point to point encryption. Yes, it would be possible, assuming you are able to establish encrypted point to point connections to all services you connect to. Or you can setup a VPN to a "relay" server. The first is simply not a reality at this point, and the second is something most people wouldn't know how to do.

Privacy would still be a problem, because anything up to Layer 3 would not be encrypted in the scenario you propose. Depending on how it is implemented, even Layer 4 would not be encrypted. Regardless, a lot of identifiable information (privacy issue, not necessarily security) would still be available.

Re:If only all wifi devices could work cooperative (1)

CityZen (464761) | about 2 years ago | (#37505120)

It's call mesh networking. If everyone did it, we wouldn't need telcos (or ISPs) so much.

Re:If only all wifi devices could work cooperative (0)

Anonymous Coward | more than 2 years ago | (#37505450)

Good luck connecting across the Pacific or getting reasonable response times from half way across the continent then.

Re:If only all wifi devices could work cooperative (1)

LordLimecat (1103839) | more than 2 years ago | (#37506122)

In this ideal world of yours, what incentive is there for ISPs to maintain their networks, as you have effectively cut them out of the loop?

You do realize that you would need a backbone SOMEWHERE unless you wanted horrific latency, for example to get traffic from coast to coast?

Re:If only all wifi devices could work cooperative (0)

Anonymous Coward | more than 2 years ago | (#37506664)

YOU do realize that if we want or need that backbone, which we do, as you correctly point out, then we will motherfucking pay for having that backbone. No reason to pay for unnecessary shit. Fucking corporate asslicker idiot.

Re:If only all wifi devices could work cooperative (1)

hedwards (940851) | about 2 years ago | (#37505158)

Well, it's not just that, it's that the devices are designed to give the most range possible without going with a unidirectional antenna. And the problem is that it worked fine when the 802.11b devices were first rolling out because few people had them, but as they've gotten to be common, you then have to deal with a dozen WAP competing for scarce spectrum.

And all is well and good if you have a large property, but if you're in an apartment and just need something that's fast and can let you move from the desk to the kitchen table, say 15' away, having a device cranking out enough power to go 200' is way too much power.

Re:If only all wifi devices could work cooperative (1)

instagib (879544) | more than 2 years ago | (#37507212)

say 15' away, having a device cranking out enough power to go 200' is way too much power

The WiFi routers I've seen have a setup were one can adjust the output power. Of course, almost noone sets it to something sensible, which means my neighbour's signals a stronger than my own in parts of the apartment (on the other hand, that same inability to configure WiFi means they all fight around the channels 1-4, so I can avoid them).

Routers should have an automatic power adjustment for the devices it has connected. Is this technically possible?

Re:If only all wifi devices could work cooperative (1)

laederkeps (976361) | more than 2 years ago | (#37507412)

LTE does something like this, where the base station continuously analyzes the radio spectrum and
figures out the optimal frequency (it uses multiple separate ones for the same cell) and the optimal
transmission power (for both downlink and uplink transmissions).

Part of the definition of optimal here is not so strong as to interfere with neighbouring cells more than necessary

In theory, you could implement some inter-AP protocol as part of a WiFi standard to allow them to
determine their resepective interference patterns on each other and cooperate better.

Re:If only all wifi devices could work cooperative (3, Informative)

tuxicle (996538) | about 2 years ago | (#37505186)

802.11a devices (operating at 5.45 GHz) are already supposed to detect radar signals and switch channels if one is found. This is particularly a problem in Europe, where most weather monitoring radars are C-band, and share the same frequency band as 802.11a.

Re:If only all wifi devices could work cooperative (4, Informative)

complete loony (663508) | more than 2 years ago | (#37505524)

Hi, I'm working for The Serval Project [servalproject.org] , and like other projects related to wifi mesh routing, we do have high level goals like this. And we're actively trying to make them a reality.

One of our staff just returned from a presentation to IEEE, to propose a more open standard for the next 802.11 spec.

The basic premise of our proposal is that the protocol for using wifi devices to route traffic should be dealt with in kernel or user space. Not in the radio spec. And that adhoc, and 802.11s are useless for this task (Damn you BSSID, why you change?). We also think that security and perhaps even error correction should be dealt with via a VPN or baked into the application layer.

We want the next wireless spec to include a basic packet radio mode, operating in any unlicensed white-space spectrum, that gives as much control as possible to higher levels of the OS. So that new interesting ideas are easier to experiment with and implement.

And we've been invited to the next IEEE working group to help make it happen.

Google owns Meraki (0)

Anonymous Coward | more than 2 years ago | (#37506234)

Google already owns Meraki, builders of great mesh gear that does just this. There are multitudes of open source projects also with low cost gear. San Francisco is meshed nicely if you look at their map at meraki's website. Of course you do need gateways, 5 hops max before latency becomes a real issue, and how do you stop the freeloaders? In a perfect world it'd be nice, realistically it's a neat concept but a niche market.

Re:If only all wifi devices could work cooperative (1)

Grieviant (1598761) | more than 2 years ago | (#37507600)

Yup, Shannon be damned. Frequency agility, which has been used in various radios for decades, will solve all these pesky spectrum crowding problems.

Like IMing in the same house (2)

EmagGeek (574360) | about 2 years ago | (#37504922)

"Honey, did you leave the microwave on?"

"I don't know, Dear, let me log into my PC and check."

Re:Like IMing in the same house (2)

maxume (22995) | about 2 years ago | (#37504972)

Right, because no one has neighbors in close proximity or anything silly like that.

Re:Like IMing in the same house (1)

zippthorne (748122) | about 2 years ago | (#37505022)

Erm.. Is it even possible to "leave the microwave on?" Aren't they all on timers?

Re:Like IMing in the same house (1)

grub (11606) | about 2 years ago | (#37505084)


Nomally, yes.

~20 years ago I had a microwave with a dial timer that stopped working but still kept the mic "running". Sometimes it would blow an internal fuse if you opened the door while operating, I got tired of changing the internal bit and wired it out. The part bypassed was the door safety assembly. Basically the thing would run with the door open and never stopped.

I had to warn anyone that was over to hit RESET before opening the door. Girlfriend moved in and we kept her microwave. Wimp.

Serious end note: I called my microwave "Ol' Auschwitz".

Re:Like IMing in the same house (0)

Anonymous Coward | about 2 years ago | (#37505108)

Can you say cancer cannon?

1) Point at obnoxious neighbour
2) Leave on
3) Profit!

Re:Like IMing in the same house (1)

LordLimecat (1103839) | more than 2 years ago | (#37506134)

Microwaves have never been shown to have any link whatsoever with cancer, nor has there ever been demonstrated any means by which they might cause it. The radiation is non-ionizing, and the effects we've seen it cause can be summed up as thermal (heats up water molecules really well), and electric (can induce arcing on metal).

If you can think up some reason microwaves are more likely to cause cancer than infrared, visibile light, and radio waves, Im sure the listening scientific community would love to hear it.

Re:Like IMing in the same house (1)

maxwell demon (590494) | more than 2 years ago | (#37507544)

If you can think up some reason microwaves are more likely to cause cancer than infrared, visibile light, and radio waves, Im sure the listening scientific community would love to hear it.

Microwaves enable you to prepare food, which may contain carcinogens. I doubt that you can do that with infrared, visible light or radio waves.
SCNR

Re:Like IMing in the same house (1)

ae1294 (1547521) | more than 2 years ago | (#37505244)

Nomally, yes.

~20 years ago I had a microwave with a dial timer that stopped working but still kept the mic "running". Sometimes it would blow an internal fuse if you opened the door while operating, I got tired of changing the internal bit and wired it out. The part bypassed was the door safety assembly. Basically the thing would run with the door open and never stopped.

I had to warn anyone that was over to hit RESET before opening the door. Girlfriend moved in and we kept her microwave. Wimp.

Serious end note: I called my microwave "Ol' Auschwitz".

Why not just wire the fuse part outside the unit?

Re:Like IMing in the same house (2)

grub (11606) | more than 2 years ago | (#37505262)

The fuse would still pop. Hey I was 25ish and stupid. Now I'm 45 and stupid.

Re:Like IMing in the same house (1)

laederkeps (976361) | more than 2 years ago | (#37507418)

Now I'm 45 and stupid.

Prolonged exposure to microwave radiation does that do you.

Re:Like IMing in the same house (1)

jones_supa (887896) | more than 2 years ago | (#37506412)

Creepy. I myself have an old Sharp microwave (built like a tank) and it has this designed behavior where it runs the fan (along the light bulb) also when the door is open, creating a feeling that the machine is running. The turntable and magnetron are then not active though...

Download link? (0)

Anonymous Coward | about 2 years ago | (#37504974)

RTFA. See a paper, but no link to binaries. Oh, "So far the researchers haven't commercialized Airshark.", right...

Why is there still microwave oven interference? (2)

vadim_t (324782) | about 2 years ago | (#37504978)

I thought that shielding was well understood and in fact a good reason of the part why microwave ovens are a common household item.

Could anybody with experience in these matters explain where the leak is coming from, and why do they still exist? Is it impractical or physically impossible to have perfect shielding for some reason?

Re:Why is there still microwave oven interference? (1)

maxume (22995) | about 2 years ago | (#37504990)

My el-cheapo microwave says on the box that it has 1500 watts of cooking power. Wifi stuff works over a couple of watts.

I see those numbers and I'm not surprised that the one can bother the other, but I don't have the EM smarts to know how easy it would be to shield the microwave enough to get the emissions down to (the equivalent of) a watt or two.

Re:Why is there still microwave oven interference? (5, Interesting)

bbn (172659) | about 2 years ago | (#37505068)

WIFI is only allowed to transmit 100 mW (0.1 watt).

Even if only 0.01% of the microwave is leaking it is still more powerful than the WIFI. And even less is required if you do not have a perfect WIFI signal to begin with.

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | more than 2 years ago | (#37505502)

Whenever I operate my 1w Alfa card with a high gain antenna I always try to keep it away from my crotch.

Re:Why is there still microwave oven interference? (2)

bill_mcgonigle (4333) | more than 2 years ago | (#37506328)

Even if only 0.01% of the microwave is leaking it is still more powerful than the WIFI.

Usually it's not any leaking from the cooking chamber, those are pretty well shielded, but the power supplies, which aren't well shielded.

I've read that it has to do with the AC duty cycle, but I previously had a Panasonic that ran on a DC inverter (supposed to make the microwave cooking better, but didn't) and it had terrible WiFi interference.
  'Microwave robustness' and 802.11g didn't do a darn bit of good (maybe because there was no duty cycle?).

Anyway, I set out to buy new microwave ovens and return them until I found a clean one, and got lucky on a Kenmore the first time. It's the gigantic one with the rounded inside corners, and I can sit at the table less than 10 feet away and not see a dB loss on the WiFi. IIRC it's made by one of the Korean companies (LG, Samsung?) It can handle a 9x13 casserole dish too, so double-plus good.

Re:Why is there still microwave oven interference? (1)

gman003 (1693318) | about 2 years ago | (#37505104)

According to Wikipedia, the safety regulations are "5 milliwatts per square centimeter, measured 5 cm from the surface" (although it cites this as "over the lifetime of the device" - I'm unsure if that means "the total amount over its life" or "the maximum released at any time during its life"). Given their 28x38x25cm measures for a "standard" microwave, that comes out to 5.4 watts. Output power on most Wifi devices is 100-200mW. So yeah, it's completely plausible that a microwave can leak enough radiation to interrupt Wi-Fi, but still meet every health and safety regulation.

Re:Why is there still microwave oven interference? (1)

mpe (36238) | more than 2 years ago | (#37506820)

My el-cheapo microwave says on the box that it has 1500 watts of cooking power. Wifi stuff works over a couple of watts.

In order to get that amount of microwave energy you'd need something in excess of 2kw of electrical energy. If you are in North America 1.5kw makes rather more sense as power consumption. The term "cooking power" could turn out to be as much a fiction as "music power".

Re:Why is there still microwave oven interference? (1)

maxume (22995) | more than 2 years ago | (#37507252)

It probably doesn't even say exactly that on the box.

Re:Why is there still microwave oven interference? (2)

djscoumoune (1731422) | about 2 years ago | (#37505058)

My parents bought a microwave oven this summer and we placed a cell phone in and called it. It rang so I doubt microwave ovens are properly shielded. It was a Samsung btw but all brands are probably the same.

Re:Why is there still microwave oven interference? (2)

networkzombie (921324) | about 2 years ago | (#37505096)

Really? I installed my Whirlpool microwave and neither my cell nor my GF's cell (ATT & Verizon) receives any text, call, or email while in the microwave. I test it often. If I were you I would stop using your Samsung microwave, or at least get a remote control for it so you can cook from down the street.

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | more than 2 years ago | (#37505422)

Did you microwave it first?

Re:Why is there still microwave oven interference? (1)

cffrost (885375) | more than 2 years ago | (#37506598)

If a microwave oven were leaking enough energy to be harmful, wouldn't that energy be perceptible as warmth/pain? Let's suppose that's not the case; what type of injury could be inflicted that would not be apparent to the exposed person?

Re:Why is there still microwave oven interference? (1)

Auntiegrav (2462228) | more than 2 years ago | (#37507800)

http://www.lifeenergies.com/symptoms/sysrmfi.htm [lifeenergies.com] Symptoms of radio wave sickness Neurological : headaches, dizziness, nausea, difficulty concentrating, memory loss, irritability, depression, anxiety, insomnia, fatigue, weakness, tremors, muscle spasms, numbness, tingling, altered reflexes, muscle and joint paint, leg/foot pain, "Flu-like" symptoms, fever. More severe reactions can include seizures, paralysis, psychosis and stroke. [Possibly MS as well.]

Re:Why is there still microwave oven interference? (1)

analyst-cz (1386075) | more than 2 years ago | (#37506944)

Really? I installed my Whirlpool microwave and neither my cell nor my GF's cell (ATT & Verizon) receives any text, call, or email while in the microwave. I test it often.

[joke]
Well, I repeated your tests and I can confirm: not only my cell does not receive any text, call, or email while in the microwave, but even for infinite time afterwards. Maybe due to the apparent design change, which occurred during the microwave exposition? You did not mention any visible changes...

Used methodology: put cell into microwave, set at least 700 W power, apply for at least 1 minute. Visible changes comes after some first 10 secs. My neighbor even reported (using the same methodology) explosion (probably caused by battery) after some 40 secs.
[/joke ]

Sorry for this lightweight spam, but I could not help myself.

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | about 2 years ago | (#37505146)

Except you cell phone most like works on 800/850/1800/1900 or possibly 1700/2100. Different wave lengths (although close in the higher bands) than the 2400MHz a microwave is shielded for

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | about 2 years ago | (#37505170)

What makes you think it shields against cell phone frequencies?

Re:Why is there still microwave oven interference? (1)

Osgeld (1900440) | more than 2 years ago | (#37505532)

so what, celphones work on a different frequency, shielding is not the same as a Faraday cage

Re:Why is there still microwave oven interference? (1)

LordLimecat (1103839) | more than 2 years ago | (#37506142)

It doesnt work that way. Microwave ovens are designed to block microwave radiation at the wavelength they produce; sticking a completely different EM source inside it and noting that the radiation isnt blocked doesnt show you anything. Wavelength plays a big part in it.

Re:Why is there still microwave oven interference? (1)

mpe (36238) | more than 2 years ago | (#37506836)

My parents bought a microwave oven this summer and we placed a cell phone in and called it. It rang so I doubt microwave ovens are properly shielded.

All that proves is that it dosn't block 1.9GHz, 1.8GHz, 850kHz, 900kHz, 450kHz or whatever the phone was using.
You might just as well put a battery powered radio inside. Or even declared it was not "properly shielded" because you could see inside!

Re:Why is there still microwave oven interference? (2)

stms (1132653) | about 2 years ago | (#37505062)

I don't have much experience with this kind of thing but from what I can extrapolate from this [wikihow.com] wikihow article it's just that some microwaves are poorly designed or are old.

Re:Why is there still microwave oven interference? (1)

tuxicle (996538) | about 2 years ago | (#37505162)

Perfect anything is impossible to achieve when dealing with microwave devices, in my opinion. Particularly shielding - you can reduce it down to a point, and it gets expensive the lower you go. For instance, "quiet chambers" used when testing for EMI compliance typically have doors with beryllium-copper fingers that try to create a faraday shield to keep out external interference. I've never seen any commercial microwave oven that uses these - for good reason too, since they're expensive and won't last very long in a kitchen environment.

Most microwaves would try to ensure that the gap between the metal door and the body is small enough that the waveguide thus formed would have significant attenuation at 2.45 GHz. Any waveguide has a "cutoff" frequency, below which propagation can only occur through evanescent waves, which decay very rapidly. However, the relative power levels involved (microwaves generate 1 kW, or about 60 dBm, while WiFi receivers are sensitive down to about -90 dBm, or 1 picowatt) means that evanescent waves that escape can cause interference.

Re:Why is there still microwave oven interference? (1)

maxwell demon (590494) | more than 2 years ago | (#37507588)

Aren't the fingers there to avoid reflection of the inside radiation? In that case, they would be counter productive for microwave ovens; you definitely do not want the internal radiation to be absorbed by the walls.

Re:Why is there still microwave oven interference? (1)

tuxicle (996538) | more than 2 years ago | (#37507976)

You must be referring to the foam absorbers [djmelectronics.com] used in an anechoic chamber, these are used for absorption. I was referring to finger stock [majr.com] that's used to minimize leakage out (or into) an enclosure with a door.

Re:Why is there still microwave oven interference? (1)

Osgeld (1900440) | more than 2 years ago | (#37505522)

yes it is impossible to have perfect shielding, for your average 30$ microwave, and even if it would probably blow something open from steam pressure inside

Re:Why is there still microwave oven interference? (2, Informative)

complete loony (663508) | more than 2 years ago | (#37505574)

Why else do you think 2.4 Ghz wifi is unlicensed spectrum? It's mainly *because* microwaves make it useless for much else.

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | more than 2 years ago | (#37506348)

shielding for microwaves is a matter of attenuation, as in, if you want any type of window whatsoever to see the food inside, some microwaves are going to get through the holes in the metallic grid that is on the window -- just very very little.

Re:Why is there still microwave oven interference? (0)

Anonymous Coward | more than 2 years ago | (#37506812)

It's from those people who take the 3-prong plug on the microwave oven, plug that into a 3-to-2 prong adapter, then into an ungrounded receptacle. No grounding means no Faraday cage, turning the machine into an antenna.

I've done this plenty (5, Funny)

ModernGeek (601932) | about 2 years ago | (#37504982)

When my downloads get slow and I can't refresh slashdot, it means it's time to take a break because mom is making me a snack upstairs.

Move time! (0)

Anonymous Coward | about 2 years ago | (#37504984)

"Hey I'm trying to stream a movie here! Oh wait it's the microwave? Can you bring me some popcorn?" 'Nuff said. ;)

Microwave channel = 2450 MHz (1)

dougmc (70836) | about 2 years ago | (#37505056)

Most microwaves oven are supposed to work right at 2450 MHz, so if you want to avoid microwave ovens (which you should if there's one in the area and it's used often), you want to use the highest or the lowest numbered WiFi channel -- you don't need a spectrum analyzer to tell you that.

But if you want to see the results of one on many microwave ovens ... here you go [bldrdoc.gov] . It looks like the exact bandwidth used by their signals vary quite a bit, though my advice above still stands in the majority of cases.

Of course, there are other 2.4 GHz band users as well, and a scanner could be useful for pinpointing those.

If you buy one of the CHEAP WiFi Detectors (2)

MindPrison (864299) | about 2 years ago | (#37505092)

(not to be confused with the WIFE Detector(tm) )

then you can indeed detect a microwave oven, and pretty much anything that spews out parasitic signals from 1500-3000 Mhz.

*Technical explanation coming up*
This is due to the cheap construction of those So Called WiFi detectors, they're not digital, they're in fact analog receivers that only detect any modulation on the band (very VERY wide-band / BroadBand reception)... it's just a glorified Crystal Radio with a small half-coil, 3-4 transistors to amplify anything...any signal picked up by the small 1 cm internal antenna, and 1 transistor to switch on a led (or 3-4 resistors, if it's sophisticated and have 3-4 leds...ha ha) ;)

There...now the Chinese can mass-produce them, I just literally gave you the schematics for it... ...oh wait!

Re:If you buy one of the CHEAP WiFi Detectors (1)

networkzombie (921324) | about 2 years ago | (#37505164)

This reminds me of my poor-man's EMI-RFI detector. Whenever someone asks me why their software threw an error I tell them it is probably EMI from the fluorescent lights or their improperly shielded power strip. When they call bullshit I grab the wand from my tone kit and presto! As it gets closer to the field it gets louder. They think I'm a genius and of course, I am! Also, they don't even know what a tone kit is so the genius bar isn't very high. I hope I don't get sued for using that term.

Re:If you buy one of the CHEAP WiFi Detectors (1)

jovius (974690) | more than 2 years ago | (#37506662)

Could it be possible to create a 3D image of your surroundings by some triangulation and delicate signal processing of WIFI signals? The more there are microwave sources the better the result.

Re:If you buy one of the CHEAP WiFi Detectors (1)

Arlet (29997) | more than 2 years ago | (#37507082)

That would be tricky. A lot of things tend to reflect the 2.4 GHz signals, and the reflections interfere with the signal. A fun experiment is to attach a 2.4 GHz antenna to a spectrum analyzer, and move it around. Just moving it a few inches back and forth has enormous effect on the signal strength (that's why a lot of gear has two antennas).

Maleficence (1)

mr100percent (57156) | about 2 years ago | (#37505102)

I was going to say how this sounds like a potential invasion of privacy, but then I realized that the police knowing you have a microwave or Xbox controller probably isn't something to worry about.

Re:Maleficence (1)

CAIMLAS (41445) | more than 2 years ago | (#37506256)

You're correct; however, if I can detect someone's 2.4GHz wireless security camera(s), it's another story. It really would be an invasion of privacy at that point, assuming I'm intent upon invading your privacy.

Microwave covers the whole 2.4 Ghz wifi band (1)

CityZen (464761) | about 2 years ago | (#37505110)

The only escape is the 5 Ghz band, but if you could use that, you'd be doing so in the first place.

Re:Microwave covers the whole 2.4 Ghz wifi band (0)

Anonymous Coward | more than 2 years ago | (#37506146)

NO. I manage 802.11n certified networks(5Ghz) and they are great if you have a direct line of sight between the AP and the client. In most offices and homes you don't have that convenience, in which case, 5Ghz sucks. As soon as there is a physical obstacle, signal reception drops off.

Re:Microwave covers the whole 2.4 Ghz wifi band (1)

CityZen (464761) | more than 2 years ago | (#37508080)

You're agreeing with my me. 5 Ghz doesn't penetrate stuff well at all, which means obstacles both help prevent outside interference as well as block your desired signal. When you can use it, it's great, but you often can't.

Source (1)

colsandurz45 (1314477) | about 2 years ago | (#37505148)

So where's the source code for this?

Re:Source (1)

mene (1660015) | more than 2 years ago | (#37506762)

So where's the source code for this?

Not the sources, but they put out a couple of FREE iOS and Android Apps: http://itunes.apple.com/us/app/network-test-networktest-org/id433948720?mt=8 [apple.com] https://market.android.com/details?id=com.measurement.frontend [android.com]

So, no maemo/meego version then (1)

Eunuchswear (210685) | more than 2 years ago | (#37506832)

Drat

Android phone please (1)

cultiv8 (1660093) | more than 2 years ago | (#37505242)

I would love to use my Bionic, headset, GV and sipdroid [sipdroid.org] over wifi, currently not possible b/c of wifi interference [google.com] .

Re:Android phone please (0)

Anonymous Coward | more than 2 years ago | (#37506462)

I would love to use my Bionic, headset, GV and sipdroid [sipdroid.org] over wifi, currently not possible b/c of wifi interference [google.com] .

It's not only possible, but the link you provided says exactly how to do it.

Can't avoid Bluetooth either (0)

Anonymous Coward | more than 2 years ago | (#37505256)

Bluetooth hops across the 2.4 Ghz spectrum. You can configure a Bluetooth host to avoid a given wifi channel, but it doesn't work the other way around. Again, the only way to avoid it is to not use the 2.4 Ghz band.

We've got to install microwave ovens. (0)

Anonymous Coward | more than 2 years ago | (#37505298)

Custom kitchen, deliverieieies.

Using NetStumber to measure microwave oven leaks (1)

Mozz Alimoz (245834) | more than 2 years ago | (#37505378)

I had a microwave oven that consistently stopped my Netflix videos streaming over WiFi every time someone made a cup of tea.
I was able to prove a contributing issue was related to its poor door seal letting microwaves out using the free WiFi tool NetStumbler [wikipedia.org] (Also known as "Network Stumbler").

NetStumbler has can graph the Signal/Noise ratio of a WiFi station over time. If you put a laptop running NetStumber in a microwave (Don't turn on the microwave!) you should see the signal to noise ratio drop 30 dBm [wikipedia.org] as the door shielding attenuates the WiFi signal. If not, you probably have an old oven that has developed a wonky door seal.

In my case, I was able to feel the microwave door close a little more as I pressed the handle. And after alternating pressing and releasing the door without changing my body position, 10 seconds on 10 seconds off, I was able to clearly see a 5 dBm difference in the WiFi signal to noise ratio on my old oven. That didn't happen on my new oven.

I also saw other people comment that if a cell phone rings inside a microwave, then that's a sign the microwave is leaky. I doubt that's reliable, since many cell phones use a different frequency than microwave ovens. And they don't report signal strength accurately.

But can it detect... (1)

DragonHawk (21256) | more than 2 years ago | (#37505394)

But can the researchers detect the government mind control rays transmitted from cell phone towers? If it could do that, I wouldn't have to wear this tin-foil hat all the time!

Or! (0)

Anonymous Coward | more than 2 years ago | (#37505396)

Just stop using your microwave. There are few good reasons to do so.

Seriously we've become so fucking lazy that we can't even surf porn without being interrupted by a Lean Cuisine?

New function for tricorder-like apps. (1)

Commontwist (2452418) | more than 2 years ago | (#37505518)

Handy-dandy microwave signal detector! Hey, if your app can tell between wifi and microwave then that would be a neat thing to be able to track.

Easy fix (0)

Anonymous Coward | more than 2 years ago | (#37505660)

Cook real food. One the range or in the oven. Disregard microwave ovens.

Re:Easy fix (1)

wierd_w (1375923) | more than 2 years ago | (#37505802)

Sadly the 1950s style jiffy pop always seems to burn the popcorn.

Toaster ovens burn the bag.

That leaves hot air poppers, but they spew rf noise worse than microwave ovens do. (The momentary contacters in the hot air blower act like spark gap transmitters, and blanket a large spectrum. Same with hair driers btw.)

So, how am I supposed to make popcorn, eh?

Re:Easy fix (2)

YrWrstNtmr (564987) | more than 2 years ago | (#37506184)

So, how am I supposed to make popcorn, eh?

Bag of regular popcorn.
Medium size pot, with lid
Oil, or I prefer bacon grease

Put it on the stove, on just above medium *
Put a thin layer of oil in the bottom
Put two and only two kernals in it.
When the first one pops, turn the heat down a little *
Put in one and only one layer of kernals on the bottom
Put the lid on the pot
When it is 2 seconds between pops, it is done.
During popping, you may give the pot one and only one shake.

* your stove settings may vary

UW! (0)

incripshin (580256) | more than 2 years ago | (#37505738)

Nice, I know the second author of that since I just got my masters there in CS. Also, screw 'UW-Madison'. It is 'UW' and I hate that people put it on the same level as all the other bullshit UW-* schools (http://www.wisconsin.edu/campuses/ [wisconsin.edu] ).

Eh, what? (2)

russotto (537200) | more than 2 years ago | (#37505810)

First of all, switching channels to avoid a microwave is futile... the magnetron isn't all that frequency stable and the peak tends to wander across the band as a result.

Second, 802.11g/n uses OFDM. You get narrowband interference, you reduce the rate on the affected subcarriers. It's built in.

Third, I'm fairly sure using a wifi card as a spectrum analyzer has been done before.

Re:Eh, what? (0)

Anonymous Coward | more than 2 years ago | (#37506474)

First of all, switching channels to avoid a microwave is futile... the magnetron isn't all that frequency stable and the peak tends to wander across the band as a result.

Second, 802.11g/n uses OFDM. You get narrowband interference, you reduce the rate on the affected subcarriers. It's built in.

Third, I'm fairly sure using a wifi card as a spectrum analyzer has been done before.

First, what you say is partly true --- peak does tend to wander, although the amount of drift is limited to the higher WiFi channels (mostly tends be around ch. 8 - ch. 11). Thus, changing the channel for e.g., to 1 does make sense. I put my home WLAN on channel 1, and it works much better when I use my microwave oven. Second, You CANNOT reduce the rate on selected sub-carriers in 802.11. You can do this in OFDMA, not OFDM which is used in 802.11 a/b/g/n. And Third, there are companies like Aruba, Meraki which claim to do spectrum analysis on a WiFi card, but there little documentation on "how" to do this. This work seems interesting to me as they at least tell us how to do this using a WiFi card (if one is willing to put in the effort of reading the report that is!). It would definitely be nice to see how their solution compares to that of Aruba and Meraki

How about one that can't (2)

Hentes (2461350) | more than 2 years ago | (#37505830)

This is cool but I would be far more interested in a card that does NOT detect microwave signals.

This is new? (0)

Anonymous Coward | more than 2 years ago | (#37505928)

My 3 yr old dell D830 has a BCM4315/BCM22062000 chipset with a utility that detects congestion in the wireless G band. Used it to find an Epson printer that was committing a wireless DOS attack on my network. These things are nice to have if you are a geek for hire. Unfortunatly, the bastrds at Apple pulled all useful apps like this for their walled garden because the script kiddies were using them for malfesance. Bummer.

Re:This is new? (0)

Anonymous Coward | more than 2 years ago | (#37506608)

Detecting congestion? Yes. Which device caused the congestion? No.

True Story (2)

flatulus (260854) | more than 2 years ago | (#37506190)

In 1992 I was at an IEEE 802.11 meeting (that's WiFi, if you didn't know it by that name). My company was presenting a "pre-standard" wireless LAN design that we were developing, to be considered as a contribution to the standard.

Someone asked "Why does your design have so much error correction coding? Are you expecting the RF environment to be that bad?"

I replied, "Well, I haven't seen any 'Listen Before Cook' microwave ovens out there!"

This got a few chuckles and we moved along.

Many years later, I was doing some patent searches, and I came upon Patent number 6,346,692, titled "Adaptive Microwave Oven"

I'll be damned! Somebody actually patented the "Listen Before Cook microwave oven!"

So now we have WiFi devices detecting microwave ovens. That seems obvious to me. But I'm still waiting for a commercially available microwave oven that will avoid stomping on my WiFi signal :-)

FWIW, The 802.11 Media Access Control (MAC) protocol effectively avoids microwave ovens most of the time, because the magnetrons in consumer microwave ovens only operate on a "half wave" basis. This means they're off at least half the time. A microwave oven during its "on" time looks indistinguishable from another WiFi transmitter, and so your WiFi device simply waits until the microwave oven turns off before transmitting the next packet. This results in slower throughput, but isn't a show stopper.

The bigger problem is that since the microwave oven doesn't listen before turning on its magnetron, it tends to "stomp on" your WiFi signal occasionally. This, combined with the fact that the majority of IP based communications is TCP (and TCP sees every packet loss as congestion, causing it to slow down for the next few-to-tens of seconds), results in more throughput loss than is strictly related to the number of packets "stomped upon."

Re:True Story (1)

catmistake (814204) | more than 2 years ago | (#37507210)

But I'm still waiting for a commercially available microwave oven that will avoid stomping on my WiFi signal :-)

That'd be nice, but I'm waiting for a reverse microwave: instead of heating food by exciting water molecules with microwaves, it cools stuff by sucking out the microwaves... so you put your warm beer in there and a minute later its frosty cold and completely drained of microwaves.

Handy smartphone and ps3 controler detector (1)

madhi19 (1972884) | more than 2 years ago | (#37506360)

I could so see an application that let you detect and pinpoint a phone or any bluetooth device that you lost around the house. The problem is a thief could also be using it to pinpoint what houses got the good electronic shit just by driving around or what houses are empty just by looking for who not using anything! Hell you want to steal dozen of cell phones you just drive to the nearest parking lot with this thing.

Wi spy expensive ? (0)

Anonymous Coward | more than 2 years ago | (#37506712)

I recently bought a wispy plus for about $200.

It was worth every cent

Perhaps the author lives in a cardboard box

Re:Wi spy expensive ? (1)

CityZen (464761) | more than 2 years ago | (#37508138)

There's also the Ubiquiti AirView, which I see is available for as low a $40 now.

Assistance (0)

Anonymous Coward | more than 2 years ago | (#37507450)

My magnetron is fed a sample from my wifi transmitter so nuking food doesn't stop me from nuking Zergs. :O

But apparently can't detect name interference... (1)

Shoten (260439) | more than 2 years ago | (#37508892)

They should have done a little Googling before they decided on a name...there's already a commercial product (albeit a very different one) that uses the name "AirShark":

http://www.itrbo.com/airshark/airshark.html [itrbo.com]

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