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4mula1
2007-09-01, 07:28
I have two SB3s, one in the kitchen on top of the microwave, the other in the living room hooked to my A/V stack. My wife and daughter are addicted to TV so I don't get to use that SB3 too much, but I get to use the one in the kitchen pretty much whenever I want. Before somebody quips that my wife should be in the kitchen and not me, I work first shift, she works second.

I quickly learned that when the microwave is on it will "disable" the SB3. Fair enough, I don't use the microwave too much anyway. Today I'm by myself and am listening to the SB3 in the living room and cooked something in the microwave. The audio stopped. Hmmm. I went and unplugged the kitchen SB3 and after a couple of seconds the music stuttered back to life and after about ten seconds everything was fine.

Seems that when one SB3 has a high level of interference and is trying to reconnect it can cause the server problems resulting in the rest of the SB3s to act up. My server is an Athlon 800MHz so it's not setting the world on fire.

Anybody experience something like this?

pfarrell
2007-09-01, 07:46
4mula1 wrote:
> Anybody experience something like this?

Its a feature of WiFi.
Microwave ovens use 2.4gHz because that is a frequency the resonates the
bond between the hydrogen and oxygen atoms in water. So it makes things
cook fast. When mircowave ovens were invented, no other radio engineer
wanted that frequency range, because water in plants would absorb it and
decrease range/distance, which is not what a radio or TV transmission wants.

When WiFi was invented, they found that 2.4gHz was unused and
unregulated world wide so they picked it. The reason it was unused was
that no sensible RF engineer wanted it.

Since then, BlueTooth and ZigBee and other communications technologies
also use 2.4gHz. So it is getting crowded. And all of them get clobbered
by some microwave ovens.

Some ovens are better sealed than others, so you might try that.
Or use a wire.

The short answer to your question is: yes, lots of ovens interfere with
SqueezeBoxes. It has nothing to do with your server.

--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

James_B
2007-09-01, 08:22
I have two SB3s, one in the kitchen on top of the microwave, the other in the living room hooked to my A/V stack. My wife and daughter are addicted to TV so I don't get to use that SB3 too much, but I get to use the one in the kitchen pretty much whenever I want. Before somebody quips that my wife should be in the kitchen and not me, I work first shift, she works second.


Anybody experience something like this?

I am in a pretty much identical position except my microwave does not intefere - but it might be slowly cooking the inisdes of my speakers.

Anyway unless you´re heating a lot of TV dinners (which it sounds like you are not) I guess it isn´t going to cause you much bother :)

SuperQ
2007-09-01, 08:39
Looks like most of the question is answered, but my suggestion is to get a new microwave.. I don't use mine very often either, but I have no wifi issues if mine is on. (I did real testing, bandwidth and latency tests while boiling a bowl of water :)

Any microwave that leaks enough RF to cause wifi problems needs to be replaced.

One of these days I'm going to pick up a WiSpy http://www.metageek.net/

danco
2007-09-01, 10:09
Nobody has yet commented that changing the wireless channel can often solve microwave interference problems.

pfarrell
2007-09-01, 10:11
danco wrote:
> Nobody has yet commented that changing the wireless channel can often
> solve microwave interference problems.

It does work sometimes. Worth a try.
But I never had any luck with it.

4mula1
2007-09-01, 15:46
I wanted to see if the SB3 on the microwave did in fact cause problems by creating a load on SlimServer trying to connect. I had the SB3 on the microwave off while playing music on both my living room SB3 and Softsqueeze.

That microwave must throw some major interference!!! The living room SB3 quit playing while Softsqueeze soldiered on. The test was over when the door on the microwave blew open (I had a pyrex jar with water in it). Don't know what caused that one!

Conclusion: My 4 year old won't be within three feet of the microwave while we're making popcorn. Since I don't use it that much it's not a big deal, I was just puzzled that it took down the other SB3 in an adjacent room.

Mark Lanctot
2007-09-01, 16:18
I thought I read somewhere that you can use an unlit fluorescent lightbulb as a microwave detector. It's supposed to glow when you hold it near the door seals if the microwave leaks.

muski
2007-09-01, 22:44
This has just starting happening to me, too. 4mula1, are you running an 802.11n network?

I just upgraded from an Airport Express (802.11g) to an Airport Extreme (802.11n) and now my SB3 loses it's connection every time the microwave is used.

I currently have the channel setting on my Airport Extreme to Automatic, but may fiddle with it.

(On the other hand I used to get network dropouts on my laptop all the time with my Airport Express, and now it never happens with the Airport Extreme...)

danco
2007-09-01, 23:59
danco wrote:
> Nobody has yet commented that changing the wireless channel can often
> solve microwave interference problems.

It does work sometimes. Worth a try.
But I never had any luck with it.

Worked fine for me. I used to have dropouts whenever I used the microwave, and they disappeared when I changed the channel. Maybe it depends on the microwave and the available channels.

Zten
2007-09-04, 09:21
I found some of my old posts on Microwave ovens:

Curious to know what WiFi channels the microwave would affect the most, I ran the throughput tests again with the access point set to different channels. On channels 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, the throughput was 660pps, 658pps, 655pps, 651pps, 643pps, 574pps, 434pps, 258pps, 178pps, 191pps, and 210pps, respectively. Based on these numbers, the microwave was most critically impacting channels 8, 9, 10, and 11.

I also found that the impact is more severe near edges of the range boundary of the access point where signal levels are lower. To test this, I lowered the transmit power of the access point to 1mW, which caused the signal power to decrease to -77dBm. This level is close to the range boundary of the WLAN.

As one would expect, the hit on throughput was even more with the weaker signals. The resulting throughput was about 10 percent lower than the case where the signal levels from the access point were higher at -63dBm.

What do you do about interference from microwave ovens?

Consider the following countermeasures:

Change access point channels. The microwave in use with this testing didnt severely degrade channels 1 through 6. As a result, avoid the use of these channels in areas of the building where microwave ovens operate. In fact, web browsing was very fast with the microwave running and the access point set to channel 1 and channel 6. Keep in mind, however, that your microwave ovens may operate at different frequencies within the 2.4GHz band. Check the label on the back of the microwave, which should provide the center operating frequency.
Avoid using the WLAN near microwave ovens. Keep at least ten feet away from operating microwaves while actively using WLAN applications. This eliminates working from most company break rooms when the microwave is in use. The actual impacts would only be intermittent, though, when someone runs the microwave for a few minutes while heating up a burrito or cup of soup.
As you can see, microwave ovens wont completely bring down your WLAN. Just be aware of the situation, and of the applicable countermeasures.

Table A-2 Channels for IEEE 802.11b

Channel Identifier Frequency in MHz Regulatory Domains
Americas (-A)
1
2412


2
2417

3
2422

4
2427

5
2432

6
2437

7
2442

8
2447

9
2452

10
2457

11
2462

Zten
2007-09-04, 09:25
So I ended up selecting a channel that was outside of my microwave oven's operating range and have been happy ever after:

My Microwave oven is running at 2450MHz. This is approximately WiFi channel 8.5 . Turn out I was using channel 7 on my WLAN. It makes sense that I get interference from the microwave becuase the WiFi channels are very wide and actually overlap channels +/- 2 channels away!


So then what channel should I use? To answer that question I took my laptop computer and used it as a receiver to measure my neighbors WiFi Channels they are using. I am in ear shot of signals from my neighbors on channels 1, 3, 6 (several folks on Ch 6), and 11.

So, I changed my WLAN to channel 4. Seems to be a channel that no one near by uses and best of all, no more drop outs when my wife runs the microwave oven!

Mark Lanctot
2007-09-04, 09:32
NetStumbler can be configured to measure and graph signal strength real-time. You ought to be able to see the effect of microwave interference as you change channels and turn on/off the microwave.

mortslim
2007-09-06, 00:37
an earlier post states:

Any microwave that leaks enough RF to cause wifi problems needs to be replaced.

however I am guessing that there are actually two issues being confused in this thread.

first is the implication of the above quote, and in another post about keeping your kids away from the popcorn cooking (forget about the fumes, if you've read the paper in the past few days) but this issues deals with harmful radiation.

but there is a separate issue of rf interference which is not harmful but still interferes with wifi.

what I mean is, I am three rooms over, at least thiry feet, and three walls from the microwave, and stil when it's a popping, the room is rocking. now please don't tell me i'm in danger, although my microwave is thirty years old.

i mean, come one guys, are you telling me that if the squeezbox is jiggling that far away it is like a canary in the coal mine. am I fried on the inside and didn't know it?

I am not an engineer but it seems that a microwave can have separate issues of rf interference and close by radiation.

right?

Heuer
2007-09-06, 02:32
You may also find problems caused by DECT telephones which operate on 1880-1900 MHz in Europe, 1920-1930MHz in the US (not sure about other countries). They are not particularly 'clean' and have been know to produce harmonics into the 2400 Mhz band. I had a system which closed down the wi-fi signal every tine a call was made/received. Options are to move to 5.8Ghz or 900Mhz models.

Worth considering if you are still having problems!

Mark Lanctot
2007-09-06, 05:41
an earlier post states:

Any microwave that leaks enough RF to cause wifi problems needs to be replaced.

however I am guessing that there are actually two issues being confused in this thread.

first is the implication of the above quote, and in another post about keeping your kids away from the popcorn cooking (forget about the fumes, if you've read the paper in the past few days) but this issues deals with harmful radiation.

but there is a separate issue of rf interference which is not harmful but still interferes with wifi.

what I mean is, I am three rooms over, at least thiry feet, and three walls from the microwave, and stil when it's a popping, the room is rocking. now please don't tell me i'm in danger, although my microwave is thirty years old.

i mean, come one guys, are you telling me that if the squeezbox is jiggling that far away it is like a canary in the coal mine. am I fried on the inside and didn't know it?

I am not an engineer but it seems that a microwave can have separate issues of rf interference and close by radiation.

right?

Actually they are one and the same BUT there are several things to consider:

1. The effects of microwave radiation is not at all like what the term "radiation" usually implies. Microwave radiation is non-ionizing, it does not have enough strength to damage DNA and cause cancer. Its only effects are thermal burns, and even then, the intensity has to be quite high - a microwave oven is specifically designed to concentrate the radiation onto the food.

2. Radiation decreases with the square of the distance. Double your distance and the radiation level decreases by 4. Quadruple the distance and it decreases by 16. This means even a badly leaking microwave oven will have little effect provided you're not right next to it.

3. The amount of energy needed to disrupt a 2.4 GHz radio signal (802.11g) versus the amount of energy needed to affect you are many orders of magnitude apart. So while your Squeezebox may be affected, the effects on you are not measurable. You're likely receiving more radiation from your router.

4. The term "radiation" has negative connotations, but in this case it just means energy transmitted from a point. An ordinary light bulb can be said to be giving off radiation as well.

Daryle Tilroe
2007-09-06, 22:49
4mula1 wrote:[color=blue]
Microwave ovens use 2.4gHz because that is a frequency the resonates the bond between the hydrogen and oxygen atoms in water. So it makes things cook fast.

Sigh... When will this myth get stamped out. 2.4 GHz is not any exact bond resonant frequency. The effect of microwaves here is dielectric heating of any polar molecules. 2.4 GHz was chosen somewhat for historical reasons by virtue of being an unlicensed industrial frequency that is a good compromise between absorbtion and penetration in water/most foods. It is also capable of being created by magnetrons and waveguides of a reasonable size for a small appliances. Commercially there are other frequencies used, I think 900 MHz is one. Although there are absorbtion peaks for water (again these are not any unique resonance since there are many different vibration and rotation modes all "smeared" together in liquid water), one near 3 GHz IIRC and, as mentioned above, it would actually be undesireable to hit them and have most of the energy dumped into the outer layers of your food.

muski
2007-09-08, 12:55
I changed the channel on my Airport Extreme from 'Automatic' to channel 1. Seems to have fixed things -- no more dropouts when the microwave is turned on.