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Wireless-Friendly Microwaves
Makarand writes "According to this article on ABC News, scientists at the University of Michigan in Ann Arbor have stumbled upon a simple and elegant solution to keep your kitchen microwave from
becoming a noisy nuisance to your home Wi-Fi network.
They found that they could focus the microwaves into a single frequency and
reduce noisy
microwave emissions by placing ordinary magnets in specific patterns along the magnetron .
New techniques to reduce microwave interference will be needed when
Wi-Fi enabled entertainment systems will allow digital audio and video to be transmitted
to different rooms of a house wirelessly. Packet drops in such a sytem would degrade the video and audio
experience."
In other news, I didn't even know about MW ovens as Wi-Fi nuisances...
Any other problem causing appliance I should know about?
Screw Wi-Fi. I'd be happy if my microwave just didn't whine and rattle because they didn't balance that turning thing. Damn, microwaves used to be fairly legit pieces of electronics. Now mine is about as well put together as one of those robot boxing games.
Low-noise microwave magnetrons by azimuthally verying axial magnetic field - here
$ strings FTP.EXE | grep Copyright
@(#) Copyright (c) 1983 The Regents of the University of California.
The article stresses that those microwave interferences can be curtailed with "ordinary magnets" placed "in a specific pattern" so why isn't there a DIY guide for figuring out that pattern and slapping the magnets on the side of the oven? I know I'm probably oversimplifying, but if you know the pattern at which your oven emmits the microwaves, it can't be too hard to figure out the pattern at which you can put the magnets. Am I missing something? Or is it simply because, as they mentioned, reducing microwave interferences is a huge market and "opensourcing" the method would stop that?
I will continue to have the people in the appartment next door toasting my WiFi.
The summary sez:"Packet drops in such a sytem would degrade the video and audio experience."
I'm much more concerned with interference from my WAN slowing down or altering the cooking time of my microwave!
Geek1: Hey guys, want some microwave popcorn?
Geeks: Sure!
Geek1: OK, turn off all the 802.11 stuff so it will cook.
I want to delete my account but Slashdot doesn't allow it.
They found that they could focus the microwaves into a single frequency
...
Why not go all the way and make the frequency and phase of the microwave oven's magnetron adjustable, add some kind of microcontroller to drive it, and a small cpu to implement the 802.11b stack. Then, from your laptop, run this script:
WIFI_IF=eth0
DATE=`date +%s`
while [ ! $TIMEOUT ];do
DATE_PREV=$DATE
tcpdump -i $WIFI_IF -c 1
DATE=`date +%s`
let TDIFF=DATE-DATE_PREV
if [ $TDIFF -gt 5 ];then
TIMEOUT=1
fi
done
echo "Coffee is hot!"
Ah, the marvels of technology
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
What are they going to transfer the digital video over? And chances are, that'll be TCP, which should automatically send the packet, right?
Unless it's analog video, then that would be different. Although our family has a 2.4GHZ wireless video transmitter thingy, I haven't noticed any signal degradation due to the microwave...
Founder of Mirror Moon - Tsukihime Game Trans
Don't mess with magnets at home! I jest wraps my microwave in aluminium foil. If it's good enough for my head, it's good enough for my microwave. Not only does this stop interference with my WiFi, but the voices come in even clearer.
Nobody in their right mind would drink MICROWAVE COFFEE, right? Right??
But if you like it, you might as well boil your sport socks and underwear, add a dash of pergamot and enjoy a hot cup of "coffee".
Great - any idea how long these leaking microwaves have been inducing microtumors in my brain? How much longer until they grew large enough to kill me? Or how much longer until they just weird me out and I go all Charles Whitman-like on your ass?
If your microwave is interfering with any WiFi device not adjacent to it then throw it out and get a new one. Any properly shielded microwave should NOT be interfering with your WiFi signal. I worked for 2.5 years with the guys at Cisco/Aironet and we could only find one 15 year old off brand microwave that we could get to cause any noticable loss of signal in our testing shacks (basically an RF isolated chamber enclosed by a Faraday cage). None of the microwaves in the building ever caused us any problems even though we had more WiFi equipment than any place on earth. And if you don't want to/can't replace the microwave then get an 802.11a capable radio, different spectrum =)
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
They could use a wireless frequency that isn't penetrating our bodies with microwaves?
I find it very discomforting to think that the 802.11 is the resonating frequency of water. When you hit water with it, it will agitate the molecules and things get hot and cooked. The average human is 50-65% water.
WHAT THE FUCK WERE THEY SMOKING AT THE FCC?
A microwave has that protective metal mesh for a reason. It is not cool to put a tiny microwave on your desk. It is not cool to put a tiny microwave in your lap.
...will finally be able to use Chris to wirelessly kill Lois in the new Family Guy season.
Microwaves DO interfere with WiFi. Case in point, when my wife is cooking here egg rolls in the microwave, my WiFi signal drops to zero. The microwave finishes and poof...11mb connections. If I can connect, I either get really really really SLOW connections, or I have to be ontop of the AP....literally! 2.4 GHz is what many call the garbage band...you got cordless phones, cellphones are close to it, microwaves, WiFi (both a and g), video units, intercoms, and just about anything you can think of all fighting for spectrum. 5GHz is going to be no better. I am waiting to see if the either start cleaning up 2.4 GHz which would be REALLY hard, or ramp up or down the frequency. I thing the 1.2 GHz ham band would be a good candidate for refarming. From Ham use, it's not even close to being useful for public service and even if there are radios, there's usually noone there even during rush hour. The range would be a bit better then 2.4Ghz and they could totally reserve it for WLANS of all types. As a ham, I am not usually in favor of killing a band (more in favor of addding ham bands), but almost no friends of mine work 1.2GHz and I am sure all of them would like a better WLAN connection! ;)
Gorkman
Is the noise generated by an average microwave really that bad? Maybe it's just mine but it dosen't affect any of my wifi cards at all.
It does however manage to wipe out the video sender which runs on 2.4GHz aswell.
the team had hoped their study would help create more efficient radar systems for the military.
They said they didn't achieve what they set out to - I wonder if they came up with anything else.
In this case, will the company get patent rights for commercial application since it was a military research investigation...
apparently if it's being reported.
Subduction leads to orogeny
There are already 802.11 video transmitters out there... but they're a bit expensive.
My x-10 audio/video sender gets nuked by my microwave, as does my linksys 802.11b access point's transmission signal. The microwave is brand new, and top of the line.
Incidentally, even my neighbours microwaves nuke my signal (I live in a condo).
geeks are cats who dig a certain kind of cool
But can I use the within my foil hat design to stop them probing my mind?
Rus
Cheap UK and US VPS
I know when I first got my WiFi, I couldn't figure out why I had such a bad signal. The AP was behind the microwave, with a wall in between. (New home, paper thin walls) I remembered that microwaves cause interference and I moved it to the other side of the computer room. The signal went to full. It is about time they did something about it.
How to build a MASER with your microwave oven using ordinary magnets.
I have the same problem, but with both devices. Was able to solve the phone interference by swithing channels on the WAP (unless you're standing on it and talking). The microwave is about 10 ft from the laptop I use to serve up my MP3's from my linux server, and it takes it out of service everytime. I've thought about switching to 802.11a, but afraid the signal level from oposite ends of the house might be an issue. Invariably, someone will decide to make popcorn on Friday night when we're listening to music -- poof, there goes the music!
/. post using fedora core 1)
If I can find a way to pull a CAT5 cable to the laptop, that will solve the problem.
(First
Commission Apple to come up with a case for microwave ovens based on the TiBook casing.
Voila - instant Faraday Cage.
I am sitting here testing a forward error correcting file transfer protocol and in a fit of boredom I turn to Slashdot. This article is very timely as I needed a way of injecting some noise into the system.
Test environment:
IBM T-21 laptop with Orinoco gold 802.11b wireless PCCard.
SMC di-pole wireless AP (Forget the model number) which in testing has turned out to be a very good AP with range exceeding all of the standard 802.11b AP/routers we have tested.
The test file is 4MB in size and we are sending it in both directions across the wireless network with and without error correction. No suprises here, with a perfect signal the file with error correction takes slightly longer to arrive due to the increase in size. Transfer rate is about the equivalent speed to a network file copy and slightly faster than ftp on the same network.
After reading the article I moved the laptop to within two feet (as measured from microwave to the antenna of the access card) and re-ran the tests.
With the microwave off, all tests ran as normal, with the microwave on I get the following results.
Network file copy: Failed with network timeout, network not available
Our FEC file copy: completed but very slow
Our Non-FEC file copy: failed due to loss
Time to look closer. I fired up the Orinoco client tools for site monitoring which allow you to view various network conditions. With the network off the signal was typically at -72db and the noise was measured at -92db. With the microwave on the signal would range between -72db and -60db and noise would range from between -90db and -63db. With the microwave on the signal quality would range between non-existent and 'good'.
Running our tests produced the following results.
Microwave off:
-------- Transfer Summary --------
Data bytes: 45638341
Elapsed time: 91.93 seconds
Effective rate: 3971.44 Kbps
Packets lost: 11
Packets sent: 46853
Requested Rate: 10000
Actual Wire rate: 4370.70 Kbps
Average loss: 0.02%
Average RTT: 35.88 ms
Microwave on:
-------- Transfer Summary --------
Data bytes: 45638341
Elapsed time: 390.71 seconds
Effective rate: 934.47 Kbps
Packets lost: 3225
Packets sent: 50067
Requested Rate: 10000
Actual Wire rate: 1098.95 Kbps
Average loss: 6.44%
Average RTT: 85.03 ms
The two important numbers are effective wire rate and packets lost. Keep in mind that repeated attempts at shell based file copies failed completely as did a non-fec file copy using udp and tcp. This looks like a problem that really does need a solution, at least for 802.11b.
Oh, and my microwave is a two year old top of the line KitchenAid built in so it is surrounded by an additional metal frame and all of the wooden cabinets (and whatever they contain). Even with all that extra shielding it was massivly effecting the wireless throughput and presumably anything else within range, scary, I won't be standing too close to the microwave from now on when its on thats for sure.
Simple, because microwaves operate at this frequency (and other reasons), the FCC declared this an 'unregulated' frequency. As long as you stay within certain rules, you can broadcast however you like in this range. Other frequency ranges sell for (lots of) money. Also, the way bandwidth is regulated, it would have been difficult and expensive to make inter-operable products in a different range. There is another range in the 5GHz area, but I think that's more expensive to produce (why it took longer).
I don't read AC A human right
I also have worked in an RF lab, and tested the office microwave ovens, which were definately cheap. They did have SOME leakage, but it was nowhere near the power of the wifi and similar signals we were working with.. extremely unlikely for it to cause inteference.
Yes, leakage happens around the door and window, but not if they are designed and built properly.
However, if the microwave simply supported an IR remote, then I could reprogram one of my hackable Radio Shack remote's buttons to pause the ReplayTV and mute the TV everytime I pushed the "cook" button. (Hmmm, I think I would use Shift-Freeze to be the "cook" button. :-)
802.11 is not operating at the resonance frequency of water. Water as a liquid does NOT have any resonance, but do have an absoprtion maximum at 8-200 GHz, depending on temperature.
Water vapour has a resonance at approx. 22GHz.
More easy-to-read info at: http://www.zyra.org.uk/microw.htm
Follow links for hard-core Maxwell stuff.
The full article uses the phrase "a specific pattern". The original /. poster says "patterns" plural. The actual paper covers precision adjustment and the methods and instumentation discussed in it show that there are quite a few variations, so the poster's capsule accout actually corrected an oversimplification in the popular press. Slashdot just committed accurate news reporting. What you want to bet that'll happen again?
This is one of those cases where highly trained professionals with university grade equipment can precisely tune a gadget, but the big question is will it scale? As cheaply as most microwave ovens are made, can the manfacturers afford to duplicate this method, or will we see a bunch of ovens being advertised as "low-interference", that are really no better than the old ones?
Who is John Cabal?
What about extremely simple and effective solution:
enclosing the oven in a Faraday's cage ?
I got extremely poor link quality from my 802.11b network - like, it would barely connect - until I tried changing the channel (from 3 to 12). This improved things enormously; I haven't tested all the channels to find the best one yet but it might be worth it if you're having problems, it definitely seems possible to get variations in signal quality within the 11b band.
"'I pass the test,' she said. 'I will diminish, and go into the West, and remain Galadriel.'"
- JRR Tolkien.
I suspect that, if this dude has a high-end built-in, then the dude has the microwave running on its own circuit. wouldn't this avoid the problem you mention, anon?
WiFi is an unlicensed, "Part 15" system. It has to accept all interference from all sources.
I'm not going to pay $2 more for a microwave just so people who can't figure out how to run ethernet can avoid dropped packets every time I warm up my cocoa.
JD
Every microwave I've ever taken apart just has the series of control parts (timer, switches, fuse) and the magnetron\waveguide assembly part of which is a feedhorn pointed directly into the cooking cavity.That's all it is. The metal chassis of the microwave reflects or grounds out the RF. The problem is not only does a microwave operate very,very close to the 2.5 gig band just like 802.11 spec it also has a crummy "see thru" screen on the front with holes punched out just slightly smaller than 1 or 2 mm. Just small enought to keep wavelengths around 10-12 centimeters and below inside the box and anything above that escapes. The magnetron is noisy, it emmits spurious rf across the spectrum. The FDA has emission standards for the later model ovens. 5 mWatt/sq.CM at any point within 10 CM of cooker! Most new microwaves do a lot better than that. Solution: obviously make better sheilding inside the box, maybe a wire webbing. (I wonder what's up with pacemakers?)
...will I still be able to make an EMP gun from such a microwave?
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
I worked out a microwave interference problem - it was the switching power supply that was causing it. Needed more common mode filtering.
How does water demodulate RF? To which mechanism are you referring?
/AC
And I thought I knew how inkjet priners work, but I fail to see the relveance to RF?
These researchers are a bunch of complete idiots. Microwave ovens are DESIGNED to operate over a varying range of frequencies. BY DESIGN.
The reason for this is that the variations in frequency mean that there are fewer "Hot Spots" in the oven where all the microwaves pass through, causing food to be cooked in a non-uniform manner.
The other reason that I know these people are not as intelligent as they could be is that magnetrons are modulated at 50/60 Hz specifically. By removing this modulation many of the effects can be removed similar to 'placing magnets'.
But WHY would you want to do this? The only reason I can see is if you want to turn your microwave into a 2.4 GHz frequency source at 700W... [Electronics World magazine has an article on this BTW].
As for the absorbtion of H20 being at 2.4 GHz, you are only off by an order or magnitude. The 2.4 GHz causes excitation of the O-H bond in H20... not absorbtion
Darryl
The proper solution to the microwave interference problem is to just make the microwave a proper client to the WLAN and have it do RTS/CTS before each blast!
The US and UK came out with 10 centimeter radar in 1943 to sink U-boats. It turned the war around for us! God Bless you Magnetron.
Anyway, that's more than 60 years ago. I've still not seen anything these guys have done that someone else should have already come up with by now.High frequency EM waves also travel around anything metal (skin effect), like sheet metal siding and power lines.
Look at the headquarters for NORAD. It's deep inside a mountain. But if a nuclear weapon went off nearby and the mountain just had one metal pipe connecting the inside to the surface, then a wicked EM burst would shoot straight in there and fry all sorts of electronic devices, the ones that weren't radiation hardened anyway.This is why I'm sticking with the sheilding idea for now.
Maybe these guys did more research than I've yet seen and they desrve more credit. In any case Lau, Gilgenbach, and Neculaes have some press so now they can get more grant money. Nice.The wavelenght of a microwave is about 11 cm. Holes in the shielding smaller than about 1 quarter wavelenght cannot be penetrated by the microwaves: they are all reflected.
Most microwaves actually have tamper proof door locks; if you try to jam them while the door is still open, the fuse is blown instead of radiation being emitted.
If you don' t believe it: look it up yourself or dissect your microwave to see for yourself.
This space is intentionally staring blankly at you
if you change the antenna on a magnetron (for instance if you drive a tuning screw into the waveguide) you can change the frequency a bit, but also increase the noise on the sides of the peak enormously. Now recognise that the cooking space in a microwave oven is an integral part of the waveguide, and you will realize this 'reseach' is very hypothetical. /etc will increase the noise. And that is a good thing in microwave ovens, als someone already pointed out: less cold spots in the oven.
I wonder how they would have fared if the used complete micowave ovens instead of just olde magnetrons from them. Just putting in metal racks
This space is intentionally staring blankly at you
Just do all of your wireless networking within a gigantic Faraday cage!!!
(The cup holder already works great)
No mod points, no meta-moderating/Firehose/all the other free work Slashdot wants me to do.
ok how can i use my microwave as an amp so that i don't have to worry about my neighbors microwave effecting my wlan?
seriously aside from being legaly and ethically wrong is there a reason that you could not use the microwave to amp 802.11b
Federal law limits the output of any 802.11 device at 1 watt max (200 milliamps-I think?). A small microwave has an output of 700 to 1200 watts, that's
10 amps.
If you have the skill to build a circuit that broadcasts wi-fi at over 10 amps go ahead. Let us know what happens.
The paper said they used a DC power supply, and only speculates about what would happen with a real el-cheapo microwave oven power supply.
This matters because you can shift the frequency of a magnetron slightly off nominal resonance by varying the power input.
Microwave ovens ship with the crudest imaginable high-voltage source and the magnetron voltage isn't even approximately constant.
If the oven's frequency is bouncing around the spectrum, other users may not be able to stay out of the way.
Geez these guys waste their time on rubbish. I used to do interference analysis on wireless systems in the 2.4Ghz range. I did it on Microwave ovens as well and NIST even put out a manual on Microwave oven intereference in the 2.4Ghz range.
It's RUBBISH! The packet loss is so insignificant it's ridiculous. Infact, if you are more than a few inches away from the oven (the front of it anyway) then the intereference is negligible.
GIVE ME A BREAK!
Instead of investing thousands of euros in a Faraday shielding, I can just turn on the microwave and disrupt annoying cellphone calls!
I think I will make a business of selling this 'incredible mobile phone jamming device' to restaurants and so.
Musicians don't die. They just decompose.
Now you add 802.11 and wireless phones to the mix. They're dropped in to the same ISM band because they don't have licenses for more desirable bands, and are supposed to be very short range convenience items so the interference isn't supposed to be a serious problem in any case. So they get sent to the cheap seats, behind the microwave ovens and with no elbow room between them and all the other SRO patrons of the 2.4GHz spectrum. The same theory also applies to 900MHz products and to 27MHz CB radios--they operate as no-guarantees guests in the ISM wastelands. They just happened to get the bands without the millions of low cost microwave ovens ;^)
What I'm leading up to is this: the companies making $29.95 microwave ovens for Wally World won't spend one cent to reduce interference for WiFi networks--not until the standards for ISM equipment are changed to force them to do so, and that isn't likely to happen any time soon. If you're using ISM spectrum for communications, it's entirely at your own risk. It's allowed because, after all, you're not going to interefere with the operation of a microwave oven. But the FCC never guaranteed you a clear channel; quite the contrary--the rules state that interference from ISM must be accepted when you borrow their allocated bands.
This should only be done as a desperate last resort. If you have neighbors who ruin the quality of life in your home because they insist upon playing loud music on a disc player (or any other electronic device) and the law refuses to help and you cannot move because property values are destroyed by the niose pollution, you can fight back with microwaves. Make a parabolic chamber about 1 1/4" thick. It should consist of two flat parabolas with a focal length of about 11/16" and 20" long. You will have a sort of pill box, the side of which is a parabolic reflector 1 1/4" wide and the microwaves will shoot out of the open end of the pill box. Surround this open groove like end with a second parabolic chamber that will refocus the line source formed by the groove like opening. This parabola will have the centre of the groove as its focal point and its focal length will be 1 1/4". It will be 10" long. This will beam a narrow pattern of concentrated microwaves that you can aim at an offending stereo. It will jam the circuits from 100 feet away but it is line of sight. At close range it can burn out a stereo. The probe from a magnetron is inderted through a hole made in the focal point of the first parabola, the power supply is hooked up and you are ready to go. Just aim it, step back, and plug it in. It takes up to 7 seconds to start up. If you are nervous about microwaves, do what I do. Wear a wire screen hood over the head and stuff the vaudevillian parts of the body into a tin can. (Actually it takes several minutes to do heat damage to any parts of the body and they usually shut off the stereo within seconds.) It takes at least 0.4 watts per square cm for an uninterrupted 5 minutes to cause testicles to explode and you will not even approach this, But rumors of people doing this and the ease with which it can be done will frighten people into keeping their unwanted music to themselves. However, do not do this unless every legal recourse has been thoroughly exhausted and document refusals of police and courts to help and do not tell them what you are about to do. If you are caught you will likely have a sympathetic juror who has also been victimized by forced loud music. It is also very difficult to catch you doing it without the legal complications of entrapment.
The only reason this research makes the front page is as attempt to be politically correct by putting the (severly lacking) research of a GYPSY researcher in the limelight.