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  #1  
Old 11th April 2007, 03:14 PM
sideways Offline
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WiFi drops out when Microwave oven is on

Has anyone else noticed this phenomenon? I have a pci wifi card with rt2500 driver and a usb adapter with ndiswrapper. In both cases the wifi connection is dropped when I turn on the microwave

The problem only occurs for machines in different rooms to the access point. I used to think my wife was messing about with the router downstairs but it turns out she was using the microwave to sterilise baby stuff! The problem is even worse in a friends loft extension. He has a microwave in the room about 4-5m from the computer, and the access point is on the ground floor. We can't even heat up a couple of microwave burgers for 40 seconds without a dropout.

This article suggests using channels 1-6 to minimise the problem, but it didn't make a huge difference for me.
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  #2  
Old 11th April 2007, 03:56 PM
zeroelixis Offline
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The microwave uses the same frequency as the wireless router (2.4Ghz) and when on it may cause interference, although I'm pretty sure a well shielded/built microwave shouldn't cause such bad interference.
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  #3  
Old 11th April 2007, 04:38 PM
JoshuaWhite Offline
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A.) Your Microwave is pulling to much power on the circuit and your AP is loosing power.
B.) As ZeroElixis Wrote, Microwaves operate widband in the 2.4 GHz spectrum, and can cause interference, however they are shielded and shouldn't do so.
C.) Your microwave is leaking a small amount of interefence and your AP is junk/low power so it's noise threshold is to low.

If the problem is B, then it's a defective microwave and not really safe to be around, you should return it/call the manufacturer.
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  #4  
Old 11th April 2007, 04:56 PM
sideways Offline
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Quote:
Originally Posted by JoshuaWhite
A.) Your Microwave is pulling to much power on the circuit and your AP is loosing power.
B.) As ZeroElixis Wrote, Microwaves operate widband in the 2.4 GHz spectrum, and can cause interference, however they are shielded and shouldn't do so.
C.) Your microwave is leaking a small amount of interefence and your AP is junk/low power so it's noise threshold is to low.

If the problem is B, then it's a defective microwave and not really safe to be around, you should return it/call the manufacturer.
This happens with a least two microwaves, I assumed it was a common problem, and wanted to hear if anyone else had encountered it, I'm gonna get worried if it's just me.

I have read that a microwave with a worn or damaged protective mesh shield on the inside door can be dangerous since the actual microwaves are leaking trough the mesh, but I'd be surprised if rf emissions were dangerous.

Am I misunderstanding the technology here?

EDIT Am I being a bit dumb, microwaves are just em radiation, so wifi operates on low power microwave frequencies?

Last edited by sideways; 11th April 2007 at 05:10 PM.
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  #5  
Old 11th April 2007, 05:37 PM
Iron_Mike Offline
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Quote:
Originally Posted by JoshuaWhite
A.) Your Microwave is pulling to much power on the circuit and your AP is loosing power.
B.) As ZeroElixis Wrote, Microwaves operate widband in the 2.4 GHz spectrum, and can cause interference, however they are shielded and shouldn't do so.
C.) Your microwave is leaking a small amount of interefence and your AP is junk/low power so it's noise threshold is to low.

If the problem is B, then it's a defective microwave and not really safe to be around, you should return it/call the manufacturer.

Huh.....

ALL electronic devices devices leak RF and generate EMI except devices that are TEMPEST shielded which microwave ovens are not. RF doesn't pose any type of health risk UNLESS you standing in front of high power microwave transmitter while it is transmitting. The problem is the EMI generated from the microwaves, and how sensitive to EMI are the devices located by the microwave. Since the 2.4ghz wireless devices and microwave share the same sprectrum you have a couple different options.

1. Change to 5.8ghz wireless equipment
2. Don't use the microwave while using the wireless
3. Try to put a wall or two between your wireless devices and the microwave.
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  #6  
Old 11th April 2007, 06:17 PM
Dan Offline
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Iron_Mike has the way of it, Your microwave is a 600-1000 watt RF transmitter. Even being shielded, it will emit some RF noise. As a graphic example, try listening to an AM radio tuned to around 600 Khz or 1200 Khz, and then start the microwave. If you're even in the same house, you'll know about it!

[Heavy Sarcasm Alert]
The simplest solution is to write the FCC and demand they suddenly change their habits of many decades and begin to energetically enforce their own regulations regarding properly shielded consumer electronics!
[/Heavy Sarcasm Alert]

Realistically, re-orient the transmitting and receiving antennas, and learn to live with it.

Dan
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  #7  
Old 11th April 2007, 08:25 PM
Iron_Mike Offline
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For number 3 above, I didn't mean build some walls, just move the wireless or microwave to a different room so you have walls separating the devices....
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  #8  
Old 11th April 2007, 08:48 PM
paul matthijsse Offline
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Hey cool! I just checked this with my laptop downstairs, on which I am listening to a web radio via the access point upstairs, in my study. When I start the microwave in the kitchen, located some 4 meters from the laptop, the music is indeed interrupted (it stops, starts again; stops, etc.). Never noticed this before. Quickest workaround: do not use the microwave while listening to music, or vice versa! :-)
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  #9  
Old 11th April 2007, 09:11 PM
LinuxManMikeC Offline
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I had a problem with my US Robotics Router & Access Point restarting, which if I remember was due to the firmware resetting the router under certain conditions (including interferrence? though I never tied it to microwave usage). An update of the firmware fixed that.

Try all the wifi channels to see if one works.

If the microwave oven is leaking, there are little test thingies to check for excessive leakage. If that is the problem, get a new microwave. If the shielding is damaged then EM radiation, at potentially the same levels that cooks what is in the microwave, is escaping outside the microwave. Think about that. If the microwave is, I don't know, 5-10 years or older, I would check it regardless of wifi problems.

As already stated, play with the orientation of the antenna.

Edit: I have never noticed any significant interferrence from my microwave oven.

Last edited by LinuxManMikeC; 11th April 2007 at 09:14 PM.
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  #10  
Old 11th April 2007, 10:13 PM
sideways Offline
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What annoys me, is that I've been blaming ndiswrapper, linux native drivers etc for being poor software and causing dropouts, but after googling a bit I'm pretty convinced that microwave ovens are a very common reason for the connection failing.
We're in a block of apartments, and I think neighbours' microwave usage is also affecting us.

I have two machines in an upstairs bedroom, an access point in the living room and a microwave in the kitchen. The laptop in the living room is never affected, but the upstairs machines are, so putting walls in the way doesn't do much for us.

This is quite unbelievable. Did no one realise that the wifi frequency would be affected by a very common domestic appliance?

edit

and if I have to microwave something for +5 mins a large download will often fail (if I'm not using bittorent etc). Furthermore, the connection does not always reset itself automatically and I have to manually do a 'service network restart' (or even a 'modprobe -r ndiswrapper' and then reload) This caused me to lose 4 days of folding@home processing, when the client thought there was an unrecoverable error in the submission

Last edited by sideways; 11th April 2007 at 10:21 PM.
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  #11  
Old 11th April 2007, 10:37 PM
Iron_Mike Offline
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Quote:
Originally Posted by sideways
This is quite unbelivable. Did no one realise that the wifi frequency would be affected by a very common domestic appliance?
It had been well noted of the interference issues especially within the 2.4ghz frequency spectrum. This is why FCC has mandated certain restrictions when operating within this spectrum governing output power restrictions of devices. The 2.4ghz is part of what the FCC defines as the ISM spectrum, (Industrial, Scientific, Medical) This spectrum is pretty much free or very low cost to use so the markets build, and operate devices for this range of freqs as long as they adhere to the FCC restrictions. With a limited amount of bandwidth and so many manufacturers building devices, not all devices will play well others. Some devices are more sensitive to the EMI radiation than others. So like mentioned above, keep the EMI emissions to a minimum, reorientate the antennas, change to 802.11a equipment, etc......BTW who is the equivalent of the FCC in the UK??
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  #12  
Old 11th April 2007, 10:43 PM
sideways Offline
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Quote:
Originally Posted by Iron_Mike
keep the EMI emissions to a minimum, reorientate the antennas, change to 802.11a equipment, etc......BTW who is the equivalent of the FCC in the UK??
I have no control over the first, reorientating the antennas seems to not help (I tried altering by 90 degrees as suggested by some but it doesn't help) and switching to 802.11a is a no go with the drivers and hardware available to me. Why wasn't 802.11a made the standard I wonder?.


in the uk Ofcom is the nearest equivalent of the FCC

Last edited by sideways; 11th April 2007 at 10:47 PM.
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  #13  
Old 11th April 2007, 11:00 PM
scotta3234 Offline
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How about a signal booster?
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  #14  
Old 11th April 2007, 11:50 PM
Iron_Mike Offline
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You might try a high-gain antenna or signal booster usually an -4dbm or -6dbm is an option. Did you happen to look at what your signal strength is?? Look at it without the microwave on, and then with the microwave in use and see what the signal drop looks like....
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  #15  
Old 12th April 2007, 12:01 AM
sideways Offline
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I run kwifimanger to monitor the signal strength, don't know how accurate it is, but those green bars just disappear when the microwave goes on.

Thanks for you help guys, I will look into boosting the signal, although i have one of these rangemax routers which are supposed to boost coverage by 10x using 7 internal "smart antennas".

Ah well, I'm getting used to technological advances not being intelligently made available to consumers, at least the rest of the world hasn't got that ridiculously low quality dab (digital) radio system that we have here in the uk for instance.
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