Slashdot: News for Nerds


Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Tracking Down Wi-Fi Interference?

kdawson posted about 4 years ago | from the hello-fcc-i'd-like-to-report-hello?-hello? dept.

Wireless Networking 499

Nicros writes "Almost every evening, between 8:30 and 10:00, my Wi-Fi just dies. This, in itself, could be explained by a crappy Wi-Fi source or some hardware failure, except that I know both of my neighbors are experiencing the same loss of signal at the same time. While the Wi-Fi is down, the LAN is OK, and anything plugged into Cat5 can access the Internet just fine. One possibility comes to mind — perhaps some other neighbor arrives home and turns on their router from 8:30 to 10:00? And something in their signal is hosing our Wi-Fi? I have tried looking around for software to help identify the source of interference, but either the programs are ridiculously expensive for a home user, or else my card (Intel Link 1000 BGN) isn't supported. (Netstumbler is an example of the latter.) Any suggestions on how I can track this down?"

cancel ×


Come on Obama! (-1, Offtopic)

Anonymous Coward | about 4 years ago | (#32726146)

Show us the real birth certificate! Or else admit that you, Barack Hussein Obama are a Muslim born in Kenya and stop lying to us.

Re:Come on Obama! (-1, Troll)

Anonymous Coward | about 4 years ago | (#32726262)

Try not to put your finger on the antenna. Ask an iphone 4 user for why that is a bad thing.

Re:Come on Obama! (-1, Troll)

Anonymous Coward | about 4 years ago | (#32726624)


Only in Kenya! (-1, Offtopic)

Anonymous Coward | about 4 years ago | (#32726656)

we got the lions
only in kenya ,
going to kenya,
we got lions,
we got the tigers,
only in kenya ,
got lions and tigers only in kenya ,
we got norway,
oh kenya
where the giraffes are
and the zebras
we going to kenya
we can't believe it

report it to the fcc (2, Interesting)

Surt (22457) | about 4 years ago | (#32726150)

Let them track it down for you, it's their job. Have your neighbors report the problem also. For 3 reports they'll be there next day with triangulation equipment.

Re:report it to the fcc (0)

Anonymous Coward | about 4 years ago | (#32726264) is an unlicensed service. Unlicensed services do not receive any special protection. This is not a licensed service, FCC does not care.

Re:report it to the fcc (3, Informative)

Anonymous Coward | about 4 years ago | (#32726320)

Unlicensed means you can operate such a device without an operator's license.

It does *not* mean that the FCC doesn't care, or that they won't investigate interference.

Re:report it to the fcc (4, Interesting)

FSWKU (551325) | about 4 years ago | (#32726326)

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:

  1. This device may not cause harmful interference, and
  2. This device must accept any interference received, including interference that may cause undesired operation.

Meaning that the FCC won't do anything if your microwave is making your router go wonky. But since there is something causing outside interference to multiple people, they WILL track it down, as that means there is a device somewhere in your neighborhood that is violating the first part of the above condition.

Re:report it to the fcc (0)

Anonymous Coward | about 4 years ago | (#32726630)

Unless what's causing the interference isn't a part 15 device.

Re:report it to the fcc (2, Insightful)

dattaway (3088) | about 4 years ago | (#32726370)

WiFi is an unlicensed service. Unlicensed services do not receive any special protection.

I've known a few people who had visits from the FCC for unlicensed transmitters...

Re:report it to the fcc (5, Insightful)

Bing Tsher E (943915) | about 4 years ago | (#32726628)

It's an unlicensed service, provided you use licensed hardware to operate on it. That means, there's FCC certification behind all the commercial wifi gear you use. If you modify it or add on power boosting transmitters, you're using unlicensed hardware and the FCC will come after you.

Re:report it to the fcc (5, Informative)

GSloop (165220) | about 4 years ago | (#32726422)

I don't know if they'll come and check things out, but they do care about unlicensed bands - if you're way outside the power envelope allowed, I'm sure they'll whack you upside the head just as bad as if you were doing it in licensed spectrum.

Given the symptoms, I wouldn't be surprised to find something in the spectrum being used that IS outside the allowed power-limits.

However, I think you're more likely to get results if you find out what the offending device/person/entity is and asking them to help resolve the conflict. If they don't then you can move on to a complaint with the FCC based on power-output.

Re:report it to the fcc (0)

Imrik (148191) | about 4 years ago | (#32726462)

That's kind of the problem, they don't know what the offending device/person/entity is and know of no way of tracking it

Re:report it to the fcc (1)

blueg3 (192743) | about 4 years ago | (#32726496)

Enter the clever technology of triangulation.

Re:report it to the fcc (4, Informative)

Urza9814 (883915) | about 4 years ago | (#32726516)

...enter the FCC. That's kinda what they do....

Re:report it to the fcc (2, Informative)

GSloop (165220) | about 4 years ago | (#32726536)

You'll find a prior posted thread of mine about a spec analyzer. Perhaps it's out of financial range for the poster, since they seem to want a virtually no-cost solution, but I do offer suggestions on a spec analyzer for around $100, which is pretty good.

I didn't want to dupe that info in this thread, and it wasn't exactly the point of my post anyway. The GP claimed the FCC didn't care about unlicensed spectrum, but they do. However, they'll care a lot more if you show up with some real data - rather than "someone" must be doing something bad since my wifi doesn't work.


Re:report it to the fcc (5, Informative)

plover (150551) | about 4 years ago | (#32726610)

Here's a cheap build-it-yourself spectrum analyzer: [] The IM-ME can be had for about $15 or so, and is purportedly very hackable.

Change channel / Try Kismet (4, Insightful)

originalhack (142366) | about 4 years ago | (#32726160)

First thing to try is setting your AP to a different channel.

If that doesn't set you right, get a USB Wifi device that is supported under Linux and fire up Kismet and identify any strong signals nearby.

Re:Change channel / Try Kismet (0)

Anonymous Coward | about 4 years ago | (#32726386)

I agree with this. In ddwrt you have an option to see all other AP and the channels threw broadcast at. I set mine's to two channels apart and it was a difference as night and day. My first clue to the original culprit was that the speed would go back to normal after my neighbor went to sleep..

Re:Change channel / Try Kismet (0, Troll)

mysidia (191772) | about 4 years ago | (#32726614)

Imagine if your neighbor tried that with TV...

<PersonA> Your interfering with my television during prime time..

<Neighbor> Pls Nevermind the interference.

<PersonA> But I want to watch Fox news and you're completely scrambling it.....

<Neighbor> Feh. Then go watch CNN instead, it's on a different channel and will probably work. Problem solved.

Re:Change channel / Try Kismet (3, Funny)

PrecambrianRabbit (1834412) | about 4 years ago | (#32726668)

But I want to watch Fox news and you're completely scrambling it.....

*confused* But I thought Fox news was already scrambled!

It could be any number of things. (4, Informative)

IANAAC (692242) | about 4 years ago | (#32726162)

I had a neighbor that had an old 2.4 GHz cordless phone that used to interfere with my WiFi signal.

Once he got a 5 GHz phone all was well.

Long story, short: lots of things use the 2.4 GHz spectrum. It may not have anything to do with WiFi.

Cordless phones (4, Informative)

Dan B. (20610) | about 4 years ago | (#32726272)

I will add my 2c and say it is the increased usage of cordless 2.4GHz phones during those hours. Some of the (cheap) units don't behave particularly well with WiFi and I've personally seen just one phone cause a complete outage of all WiFi in a house.

Chances are that one of your neighbours with a teenage daughter bought some cheap but funky looking cordless phone off eBay and uses it every night during your outage window.

Re:Agree - Old wireless house phones! (5, Informative)

Anonymous Coward | about 4 years ago | (#32726306)

This is exactly the problem we had with our apartment neighbor's teenage daughter. 8:30pm -10:00 pm fits the high school homework phone schedule.
A gift of 5 GHz wireless phones to the neighbors (in exchange for their old phones of course) cleaned up our mutual WiFi problems.
Took the old phones and dumped them into ATT Wireless Store's recycle bin.

Re:Agree - Old wireless house phones! (2, Informative)

dmneoblade (848781) | about 4 years ago | (#32726508)

Nowadays it might be better and cheaper to go with 1.3 Ghz phones. Uses the TV bands that were freed up. I have one and have wonderfully interference-free calls.

Re:It could be any number of things. (5, Informative)

fake_name (245088) | about 4 years ago | (#32726588)

We had a lot of trouble with wireless disruptions around our office - I eventually bought a Wi-Spy ( for $99 because the productivity loss was getting bad enough to justify the cost of the hardware.

Running a spectrum analyzer, and moving around the office (spending a few minutes in each spot ) was a great way to see what interference was where, and it's great to be able to "see" the 2.4Ghz spectrum instead of just look at what wireless networks exist.

Don't bet on it being wifi. (5, Informative)

BabaChazz (917957) | about 4 years ago | (#32726166)

An associate of mine reported the same issue. In his case it was a failed security lamp that was trying to come on at sunset and failing; it was only when the ballast gave up after an hour and a half that his wifi -- and his AM radio -- came back. Note that many security lights are sodium arc or mercury vapor arc; not much is as hard on RF in general as a big fat arc.

Try it the low tech way... (5, Insightful)

javaguy (67183) | about 4 years ago | (#32726170)

...put a sign in your front window or building lobby asking if anyone else is having the same problem, or uses electrical equipment only between those times. Make it a friendly note, with smiles, rainbows, and unicorns, so you don't offend anyone or make it look like a witch. As a bonus you get to know your neighbours.

microwave ovens (0)

Anonymous Coward | about 4 years ago | (#32726172)

Are you or neighbors cooking with microwaves during that time? They leak like mad. Try using channel 1.

Re:microwave ovens (1)

uniquegeek (981813) | about 4 years ago | (#32726274)

That reminds me, welding will bork things up spectacularly. Not likely in this case, I think, but worth a mention.

Buy a cheap supported wifi card? (5, Insightful)

millisa (151093) | about 4 years ago | (#32726176)

If you are finding your fancy wifi card isn't supported by stumbler and other free channel overlap type tools . . . why not buy a cheap wifi card to use with those apps? You could always drop it back on craigslist/ebay (or even return it to the store claiming it doesn't match your curtains).

Also, InSSIDer (4, Informative)

millisa (151093) | about 4 years ago | (#32726228)

inSSIDer []
I've been pretty happy using that to help find the best channel for my WAPs in congested areas. If you really believe it might be a neighbor jumping online from 8:30 to 10, that could help. I haven't yet found a card it doesn't work with under windows (assuming you are running windows...)

Re:Also, InSSIDer (0)

Anonymous Coward | about 4 years ago | (#32726304)

I second this. I have used inSSIDer and the Wi-Spy hardware for a couple years now and they'll get you 99% there. Leave your laptop in a different place each day logging when the interference occurs and you'll start to see lots of great info about it and can zero in on it pretty quickly.

If you want to quickly and effectively get it sorted out, pony up the couple of bills to do it properly, or pay someone to do it properly. "Change channels" and similar solutions are just cross-your-fingers voodoo without any data to support those decisions.

Re:Buy a cheap supported wifi card? (0, Troll)

PinkyGigglebrain (730753) | about 4 years ago | (#32726648)

Good idea, only your over looking that for some people even a $5 dollar card can be out of their budget, even for the time needed to resell it. Likely not the case this time but not everyone has spare money to throw a problem.

I have the same problem in the AM (1)

TyroneShoe (912878) | about 4 years ago | (#32726180)

I have a similar problem in the morning with my WiFi over a similar time period (1 to 2 hours). I considered that it could be interference from a rogue AP as well and tried shuffling around the channels my AP was broadcasting on but with no luck. Another thought was that there are high-tension power lines near me and perhaps (100% speculation) that higher load in the AM causes some kind of RF interference... Ultimately, I purchased a Netgear WNR3700 which is a dual-band A/B/G/N AP and that sort of solved my problem; my 5Ghz wireless N access in unaffected by the issue so the only PC in the house impacted is my wife's laptop which only can do 2.4Ghz wireless-N

That's weird... (4, Funny)

Anonymous Coward | about 4 years ago | (#32726186)

That's the same time I microwave up all my hotpockets for the next day's raiding Ice Crown Citadel...

Re:That's weird... (1)

Bai jie (653604) | about 4 years ago | (#32726308)

I love a man that comes to raids prepared. Flasks, Potions and Hot Pockets!

Any more info? (1)

blackicye (760472) | about 4 years ago | (#32726192)

Are you using Wireless a/b/g or Draft-n?

Are you still able to view broadcasted SSIDs?

define "dies" (1)

MichaelSmith (789609) | about 4 years ago | (#32726194)

What trace information do you have? For example I run netbsd on my wife router and if the wifi interface goes down or stops working I would look in /var/log for trace information.

How close are your neighbors? Do you live on a farm? Or in a block of small apartments? Maybe you have a channel space issue.

Re:define "dies" (5, Funny)

Anonymous Coward | about 4 years ago | (#32726246)

For example I run netbsd on my wife router really does run on anything!

Did you get your wife from Stepford?

Re:define "dies" (1)

MichaelSmith (789609) | about 4 years ago | (#32726296)

Its not good just previewing you have to read as well.

Use your local ham radio club (5, Insightful)

crath (80215) | about 4 years ago | (#32726196)

Talk to someone in your local ham radio club and see if they have a member with a spectrum analyzer and a directional antenna. Have them come out to the house and do some direction finding to determine who is transmittin on the WiFi freqeuncies in your neighbourhood.

Be polite. Ask nicely. Buy them pizza and beer to say thank you.

Hams are nice guys and gals and they will probably be happy to help out.

The ARRL website can probably provide a contact for your local ham radio club.

Re:Use your local ham radio club (1, Redundant)

jarrettwold2002 (601633) | about 4 years ago | (#32726336)

^That right there, is just plain old good idea.

Re:Use your local ham radio club (5, Interesting)

bezenek (958723) | about 4 years ago | (#32726396)

First try what is suggested by BabaChazz in his comment above and is what most Hams would do to start. Listen for the noise on an AM radio. You do not want FM, as one of the characteristics of FM is to block this noise.

Take your (preferably hand-held) radio and tune it somewhere on the dial where there is no station. Then, you can try moving it around your computer to hear all of the RF interference your motherboard, etc. are giving off. If you cannot hear this noise, something is wrong with the radio--be sure it is set to AM. :-)

Leave the radio on, and you might hear the noise start at the time your WiFi drops. If you do not, the interference is not covering the AM frequencies (an arc will cover everything), and it is probably time to call in a Ham.
It is likely you will hear it.

If you hear it, you can walk around inside and outside your house listening for where the noise gets stronger. Often this will be tracked down to a phone pole or something else.

Once you find it, contact the appropriate person (electric distribution supplier, city, etc.) Convincing someone to fix a problem like this is not always easy.


Re:Use your local ham radio club (1)

bitbucketeer (892710) | about 4 years ago | (#32726660)

i'd go with the spectrum analyzer... if it's a strong enough signal to desense the tuner in his AM radio, it should be pretty easy to find.

Re:Use your local ham radio club (1)

adolf (21054) | about 4 years ago | (#32726426)


I haven't met a ham yet that wasn't a proper thinking sort of fellow, with a willingness to help other folks solve problems (especially if the problems are interesting to them).

Sometimes, though, it's not something so complicated that outside help is needed.

I once troubleshot a WiFi link that spanned two buildings, a block or two apart. Things had been stable since we installed it a year or two prior, but suddenly it would drop out completely a few minutes at a time, between 11:45 and 12:30.

The likely culprit? A leaky microwave oven operated at some nearby business at lunch time. The fix was completely unscientific: We changed channels, and the interference ceased being a problem.

Perhaps in the case of this particular Ask Slashdot, there is a 2nd-shift worker who tends to nuke their dinner every night when they get home.

Of course, if it is a microwave and it's nuking the entire band such that the interference cannot be avoided by using a different channel, then the only solution is to find the offending microwave and destroy it. (Ideally, this happens after you and the other affected neighbors pool a few dollars to help buy the person a new microwave, which is a far more sensible approach than complaining to the FCC or somesuch.)

Hey Nicros (5, Funny)

Anonymous Coward | about 4 years ago | (#32726208)

I'd help you buddy, but every night between 8:30 and 10:00pm I'm working on my microwave disruptor beam. If it happens any other time, let me know and I'll be glad to pop over and take a look.

Could be a lot of things (1)

taustin (171655) | about 4 years ago | (#32726216)

During a remodel of one of my employer's stores, we have trouble with our RF gun (laser scans bar codes, then prints price labels, runs off of 802.11whatever). When I went to troubleshoot it, near as I could figure, the contractors working upstairs has something that was putting out so much RF interference, the gun wouldn't boot because it couldn't read the flash memory soldered to the circuit board. Once the contractors left, it was all back to normal.

Try a Network Monitor (-1, Redundant)

stcorbett (1712020) | about 4 years ago | (#32726222)

Is the interference possibly another network broadcasting on the same 802.11 channel? Try using a wireless network monitoring program like AP Grapher for Os X or Net Stumbler for Windows. You'll be able to see the channel, signal strength of your wireless network and your neighbors and possibly the interfering network.

Re:Try a Network Monitor (1, Informative)

DavidRawling (864446) | about 4 years ago | (#32726402)


... or else my card (Intel Link 1000 BGN) isn't supported. (Netstumbler is an example ...)


Try using a wireless network monitoring program like ... Net Stumbler for Windows.

Yes, I know this is slashdot, and we don't read the articles; but is it too much to ask for you to read the freaking SUMMARY before you reply with a useless load of blather?

Think Geek is your friend. (0)

Anonymous Coward | about 4 years ago | (#32726226)

You could try to find it with something like this. []

Re:Think Geek is your friend. (1)

lengau (817416) | about 4 years ago | (#32726350)

Wouldn't it just be cheaper at that point to just get a supported (by Kismet/whatever) USB wifi card?

Re:Think Geek is your friend. (1)

EvanED (569694) | about 4 years ago | (#32726510)

While $50 isn't cheap, it's still a fair bit of money for something that is likely a bit of a longshot. From the description it sounds likely to NOT be other Wi-Fi, so a device that looks for Wi-Fi connections isn't the appropriate tool.

have you tried... (4, Informative)

uniquegeek (981813) | about 4 years ago | (#32726240)

Happens the same whether you're on channel 1, 6, or 11? (the only b/g channels that don't overlap)

I know in my high-rise apartment, almost everyone is on channel 6, and I wouldn't be surprised if peak usage was mid-evening.

Did you double-check that some rule didn't accidentally get selected, which filters you out (either in the router interface... of you're using software that has scheduling...)

If you're using a radio type that is using the 5Ghz channel, someone's old beastly cordless phone might be affecting it too. If you're using a dual-band radio on your router, try using the other band and see what happens.

Running Wireshark (free) might not tell you what specifically is causing the problem, but you can narrow it down to see if packets are timing out, or getting filtered. Maybe there's traffic you didn't expect to be there? []

Triangulate with spectrum analyzer or SNR readings (1)

antiduh (548973) | about 4 years ago | (#32726242)

You'll need a spectrum analyzer and an 2.4 GHz antenna. First, I'd confirm that it's interference just observing high noise at that time, then I'd start taking measurements around the area. A high gain directional antenna would be helpful, but you can triangulate just by observing the strength of the noise from several spots around your neighborhood, though, you might have trouble with the signal strength varying too much as you move the cable and connectors around. You might be able to do all the same with just the wireless adapter and some software like kismet.

inexpensive device (0)

Anonymous Coward | about 4 years ago | (#32726244)

This is inexpensive for what your looking for.

hard to solve (2, Interesting)

Anonymous Coward | about 4 years ago | (#32726254)

I used to work several military trade shows at m last job, bringing in all kinds of weird stuff we were doing with wireless tablets and iphones and junk, just to show off what we could do... would stay up till 3am getting everything looking right, would show up 7:30am to make sure the morning of everything was good to go, then boom 8:30am rolled around and everyone fired up there demo hardware and all wireless in the building stopped working, it was ridiculous, happened at three different shows, we kept buying nicer wifi gear each time and failed miserably, until the 4th show that year and a particular company no showed.
The next show they were at and sure enough everything came down not just for us but all the booths in the hall and the hotels wifi, it did not take us very long to get a group together and head over there with the convention staff demanding that they shut everything down until they determine which device was the issue.
They had some very unhappy phb's screaming about ruining there day, but we didn't care, i got my 125 dollar dinner and it was all good.


Anonymous Coward | about 4 years ago | (#32726280)

Lookie here. We done caught us some commie spies. You know what we do to commie spies? We shoot them, that's what we do. Then we go out and find some more, and shoot them, too !!

Go 802.11n (1)

gzipped_tar (1151931) | about 4 years ago | (#32726288)

Give up. The 2.4GHz bands are hopelessly cluttered. Adopt 802.11n before your neighbor does.

Re:Go 802.11n (4, Informative)

GSloop (165220) | about 4 years ago | (#32726364)

You realize that N doesn't spec frequency, right?

802.11n can run in 5Ghz spectrum, but can also run in 2.4 spectrum. So, simply saying "use N" doesn't mean anything in terms of frequency.

In fact, most of the "consumer-grade" 802.11n equipment is 2.4Ghz exclusively.

I'd mostly agree that 5Ghz spectrum will be less cluttered, but I'd also guess that decent equipment using the tech in the N standard will do a lot better in 2.4 than b/g will. Multiple spacial streams, and (when implemented beam-forming) as well as beneficial use of "multi-path" etc will probably make N a lot better in most environments regardless of spectrum.

Re:Go 802.11n (2, Interesting)

Will.Woodhull (1038600) | about 4 years ago | (#32726602)

While this branch of the discussion is technically interesting, I don't think a technical solution that allows pollution to continue unchecked is as appropriate as a political solution of identifying the polluter and requiring him to clean up his act. RF interference, which is probably what is going on, is definitely a form of pollution.

Is there a railroad yard or industrial site that is using remote controlled locomotives or other RC equipment in the neighborhood? The intensity of interference and the consistent schedule suggests something industrial. Possibly something that is designed to function inside a Faraday cage but the cage has been left open. It can seem awful convenient to inexperienced technicians to just leave the cover plate off so they can more quickly do the scheduled inspections and servicing....

I think you've got enough evidence to involve the FCC. So long as they are aware of the timing and do the testing when things are on the fritz, they should be able to either rule out RF interference or find the cause fairly quickly.

InSSIDer (4, Informative)

whoisrich (1194797) | about 4 years ago | (#32726290)

Netstumbler did not support my wifi card but came across InSSIDer which is free, and allowed me to easily see channel usage in the neighbourhood. They also sell USB spectrum analyzers for non wifi interference which is what you may need. []

Spec analyzer mode on ubiquity equipment/AP (4, Informative)

GSloop (165220) | about 4 years ago | (#32726310)

Get either the USB stick or one of the 2.4Ghz supported AP's from Ubiquiti. []

The newest firmware supports a Spec analyzer mode - quite good, IMO - and it's not limited to WiFi equipment - anything in the radio spectrum is "seen."

Their wireless bridges in the 5Ghz spectrum using N tech (dual spacial streams) are seriously killer too - if you've got a wireless bridge, or WISP type situation, it's really, really cheap stuff. I'm likely to end up with 2.4 ghz and 5Ghz units just for spec analysis on the cheap. The units then double as AP's / routers / Bridges. (And at around $100 each, they're pretty awesome - Bullet M5, and Nano Station M5's for example.Find a wireless N bridge that will hold links over miles that are that cheap anywhere else!)

For around $100 you could have a nice AP and a spec unit in the same hardware. Antenna, unless built into the unit is a bit more difficult/pricey, but still do-able.

Anyway, I've got a setup using them in a PtMP setup, and though it's not miles, I'm seriously impressed - and the cost factor is simply *insanely* cheap. []


No 1 Suspect: Microwave Oven (1)

rips123 (654488) | about 4 years ago | (#32726314)

Typical Microwave ovens operate at up to 1000W @ 2.4Ghz. Typical WiFi operates at 20mW @ 2.4Ghz. Yes, a Microwave oven is shielded in a metal box but 20mW is only 1/50,000th of the power of a microwave so even the slighest noisy leak from the microwave is going to look like some serious noise to the WiFi. At my parents place, the range of the WiFi drops in half whenever the Microwave is on.

Re:No 1 Suspect: Microwave Oven (0)

Anonymous Coward | about 4 years ago | (#32726376)

2.5 straight hours of microwave use every day? Not likely unless his neighbor is trying to mutate into a superhero. My money is on a cordless phone or a zigbee music system like Sonos.

Re:No 1 Suspect: Microwave Oven (1)

HTMLSpinnr (531389) | about 4 years ago | (#32726594)

Typical WiFi operates at 20mW @ 2.4Ghz.

Typical AP power is closer to 50-75mW (17-19dBm) - only low power WiFi sharing devices like MiFi would be as low as 20mW. Also worth remembering that your NIC will typically transmit back at a similar power if able.

Got an iPhone? (1)

christoofar (451967) | about 4 years ago | (#32726316)

If you got an iPhone or a Driod, you can get WiFi-Fo-Fum. Go into your router settings and make sure you're broadcasting your SSID and lock on to it on the smartphone. I've found dead spots in my rowhome (3 stories) where there were just Faraday-like dead spots in my house and one was near my basement PC. Repositioned the antenna and all was back to normal. I also can't walk near the spots when I'm using my mobile or the calls cut off, too.

Re:Got an iPhone? (1)

ekgringo (693136) | about 4 years ago | (#32726592)

This app sounded interesting so I checked the app store for it. Apparently it is no longer available on non-jailbroken iPhones.

Re:Got an iPhone? (1)

plover (150551) | about 4 years ago | (#32726640)

This app sounded interesting so I checked the app store for it. Apparently it is no longer available on non-jailbroken iPhones.

Thus, the spirit jailbreak was born. You'll seriously not regret it nearly as much as buying the damn locked down phone in the first place.

Part 15 devices... (2, Interesting)

sillivalley (411349) | about 4 years ago | (#32726318)

As a Part 15 device, you have to put up with what other devices are doing.

My first guess would be a non-802.11 device such as a video or audio sender. They can take out many 2.4GHz channels at once, where a microwave oven usually only knocks out a couple.

One workaround is to go to 5GHz -- you're still under Part 15 and susceptible to interference, but there's less of it, a lot more channels, and you can find a 40 MHz channel for 802.11n.

Without something that acts like a spectrum analyzer (such as a real spectrum analyzer -- but some modern access points and other 802.11n devices offer spectrum analysis/FFT capabilities), it's going to be difficult to identify your interference source.

Using a simple reflector such as a parabolic reflector or a corner reflector, you might have a better chance at establishing a direction for your interference source.

Re:Part 15 devices... (1)

darrylo (97569) | about 4 years ago | (#32726474)

My first guess would be a non-802.11 device such as a video or audio sender. They can take out many 2.4GHz channels at once, where a microwave oven usually only knocks out a couple.

This, or, as others have said, an old cruddy analog 2.4GHz wireless phone. A microwave is also unlikely due to the long interference period, unless someone is trying to cook everyone around him ....

Re:Part 15 devices... (1)

SheeEttin (899897) | about 4 years ago | (#32726638)

As a Part 15 device, you have to put up with what other devices are doing.

"You" being the device, yes. The user does not have to put up with it.
In any case, the other half of the part 15 rule citation is "this device may not cause harmful interference". If the interfering device is subject to part 15, it is clearly not following that rule...

General electrical interference (2, Interesting)

Anonymous Coward | about 4 years ago | (#32726324)

Keep an open mind to ANY device which could be turning on and off during the problem times.
I also had this problem and after weeks found it to correspond with the watering schedule for my garden - the water pump was on the other side of the wall to my router and was causing the interference.

Finding the source (1)

dgreer (1206) | about 4 years ago | (#32726328)

Get a radio capable of doing a spectrum analysis a directional antenna (e.g. a yagi or something similar) and a non-directional omni antenna. A connectorized Motorola Canopy would be ideal (but a bit expensive).

Connect the omni first and take a spectrum analysis before and during the interference period to identify the signature of the interfering signal. Once you know what to look for, switch to the directional and use it to find the direction of the signal. Make sure you keep in mind the reception pattern of your antenna when you're doing this, as a Yagi will have 3 lobes, one larger than the other two so make sure that you've zeroed in the largest lobe on the signal.

One thing about the signature: You MAY find that the signal "hops" around. Some SCADA systems use such signals, and it's not uncommon for SCADA systems to have a periodic pattern that repeats every 24 hours.

Oh, and you pretty much have to find this yourself, FCC won't get involved until you can pretty much prove to them that somebody is interfering with you and that they are NOT a licensed user (who likely would have a variance for using higher power than your Part 15 equipment).

Good luck!

Re:Finding the source (0)

Anonymous Coward | about 4 years ago | (#32726568)

The Ubiquti M series product line has a spectrum analyzer built in. They are cheaper than Canopy and the interface looks better.

Try changing the channel in your wireless router. (0)

Anonymous Coward | about 4 years ago | (#32726334)

Try changing the channel in your wireless router. Most set to channel 6 by default.

Re:Try changing the channel in your wireless route (1)

HTMLSpinnr (531389) | about 4 years ago | (#32726570)

Try changing the channel in your wireless router. Most set to channel 6 by default.

Remember, when choosing a channel, only 1, 6, and 11 are non-overlapping with each other - anything in between steps on the channel space of 1 and 6, or 6 and 11. Also, many (but not all) microwaves will impact the channel space between 6 and 11+, generally making 1 a better choice.

Try doing a "survey" using your wireless driver's built-in tools (most Broadcom adapters have some sort of rudimentary tool - Intel should as well). Even just a list of nearest neighbors will help you identify what channels are nearby and at what strengths. Out of 1, 6, or 11, pick something that is within the least occupied space (least number of APs or weakest AP). If your nearest neighbors are using 1 and 6, and another particularly ignorant/rude neighbor is using 3, your only real choice is 11. Now if it's 1, 6, and 9, you're kinda hosed, and you'll have to hope the channel 1 AP is furthest away because the guy using 9 is impacting 1 and 6 (just as the guy using 3 is impacting 1 and 6).

Google search turns up tons of results, but hopefully this paints a reasonable picture: []

Unfortunately your NIC doesn't do 802.11a/n - otherwise I'd suggest looking into a dual-band 802.11n router. Tons of non-overlapping channels to pick from, but the range won't be quite as good (and you'll still have to steer clear of the 5.8ghz cordless phones).

If it's really bad, have your neighbors help pitch in for a WiSpy 2.4x (~$200) which could be used to pin-point the culprit. When you're done, sell it on eBay to recoup most of the cost. Probably cheaper than having a wireless survey team coming "onsite" to validate w/ their pricey Cisco Spectrum Expert device. They'd be able to tell pretty quickly if you're dealing w/ someone who loves their microwave popcorn, a wireless video streaming device, some sort of Zigbee (though those are usually pretty low power compared to Wi-Fi and narrow-band in comparison), frequency hopping device (cordless phone, etc).

possible ISP problem? (1)

tofu2go (727555) | about 4 years ago | (#32726358)

Are you absolutely certain it is the wifi? It could be your ISP. You didn't mention whether you were on DSL or Cable. I'm on cable, and I know that whenever my ISP resets my dynamic IP, my router locks up and I have to power cycle it. If it is always happening at the same time, it could be your ISP doing something on a regular schedule.

Re:possible ISP problem? (1)

MayonakaHa (562348) | about 4 years ago | (#32726476)

Possibly, but he DID mention that the LAN works fine and anything wired up doesn't lose connectivity.

Re:possible ISP problem? (0)

Anonymous Coward | about 4 years ago | (#32726612)

This sort of thing happens to me too, but my router doesn't seem to freak out quite so much ... it resets itself. I lose internet for perhaps 30 seconds and then I am back in business.

Noisy WIFI (1)

WarJolt (990309) | about 4 years ago | (#32726362)

I doubt it's noisy transmitter because it's unlikely a WIFI radio will interfere with all channels simultaneously. Make sure you try different channels.

If you use linux and your card supports packet injection you can use airodump to capture packets and see who is transmitting the most data. You may also be able to walk around with your laptop and find which direction the signal gets stronger.

Re:Noisy WIFI (0)

Anonymous Coward | about 4 years ago | (#32726404)

You shouldn't need packet injection to use airodump. You need the driver to support monitor mode.

Baby monitors -- evil incarnate (4, Interesting)

Anonymous Coward | about 4 years ago | (#32726390)

Baby monitors. One of the few devices that can completely trash all wi-fi frequencies in an area, not just for 1-20 minutes like a microwave but for years on end. Especially older models which use an analog signal.

I had a similar problem (2, Insightful)

sdavid (556770) | about 4 years ago | (#32726392)

I think it is caused by an analog 2.4 ghz phone, and someone chats during that time period. I had one of those phones and found that when I used it it hosed most of the available channels. Replacing the phone solved the problem and doubtless made my neighbors' lives easier. After a move, the same pattern showed up. The solution was a dual-band router.

Wi-Spy Spectrum Analyzer (0)

Anonymous Coward | about 4 years ago | (#32726420)

Buy a Wi-Spy! This does exactly what you ask with helpful pictures and is what I purchased for this.

Check the microwave oven! (1)

johanwanderer (1078391) | about 4 years ago | (#32726432)

Your microwave oven operates on the same frequency as Wifi, and 8:30-10:00pm seems like a likely time for it to be running.

It's also easy to test :) if you turn it on and your wifi disconnect... bingo, time for a new, less-leaking microwave oven :)

Good luck!

Re:Check the microwave oven! (0)

Anonymous Coward | about 4 years ago | (#32726484)

Hello? This is the police. We've tracked the interference. It's coming from inside your microwave! Get out of your microwave!

Re:Check the microwave oven! (1)

plover (150551) | about 4 years ago | (#32726670)

Your microwave oven operates on the same frequency as Wifi, and 8:30-10:00pm seems like a likely time for it to be running.

Holy crap, dude, what do you cook every night that you have to nuke it for 90 minutes??? Seriously, that's a hell of a long time to run a microwave oven, and really odd that someone would cook the same microwave meal night after night.

If you're that desperate, you're likely cooking Hot Pockets or microwave burritos, and those take only a few minutes to turn from frozen and inedible to warm and inedible.

2.4GHz - 5GHz (1)

Qrypto (462155) | about 4 years ago | (#32726454)

I think one of your neighbors is talking to someone at the same time every night using his cordless phone. This could cause the type of interference if you are operating on the same channels and your antennas are positioned such that the RF waves are canceling each other. Try rotating your router 90. Seriously. Or if possible set your router to 5Ghz mode exclusively assuming your neighbor has a 2.4Ghz Phone.

Ham radio (0, Troll)

SpacePunk (17960) | about 4 years ago | (#32726470)

I once had wireless internet from a local ISP. Between myself and the tower was a ham radio operator that evidently likes to walk all over the frequencies. I could never get the douche bag to quit fucking things up on a regular basis.

What's your location again? (3, Interesting)

djupedal (584558) | about 4 years ago | (#32726504)

Check for any satellites that track overhead at that time.

I remember when they used to open electric garage doors around the neighborhood....

RF shielding paint? (2, Interesting)

MikeFM (12491) | about 4 years ago | (#32726506)

Tried [] RF Shielding paint? I always wondered if such paint would help. Of course it might kill your cell reception. If so, might be fun to paint your apartment in it before you move or maybe your bosses office when he is away.

Use a cheap (real) spectrum analyzer (2, Interesting)

tehaynes (853811) | about 4 years ago | (#32726520)

Using the 'Spectrum Analyzer' features built in to most APs and wireless clients will only show you other WiFi traffic not noise (almost always true). Also, they are not very portable. The earlier post about asking you local Ham Radio club is a good idea if there is anyone available and many Hams don't have equipment to listen to 2.4 or 5 GHz. You can search on google and other places for a 'usb wifi spectrum analyzer' for less than $50 that plugs in to your laptop. Be careful and read the specs though as some required that you use them in DOS mode. This will let you look at the actual received power level across the whole spectrum. You can walk around with a laptop until you find the noise source. It is still a steep price to pay for a one time fix. If you are the crafty type you can get a ez430-RF2500 target board for $22 from Texas Instruments [] . You will need to search for a software load that make it a SA but the are many instructions online. If you don't want to roll your own and get a prebuilt solution you can use the Ubiquiti AirView2 [] for ~$40. This is a very nice tool. You could even split the cost with your neighbors or pool money or request the person with the noisy device foot the bill for finding it.

Re:Use a cheap (real) spectrum analyzer (2, Informative)

bassman998 (922503) | about 4 years ago | (#32726620)

I've been using the Wi-Spy from Metageek at work. I hadn't heard of the Ubiquity AirView. It looks like it's pretty competitive with the Wi-Spy -- apparently it uses the same chip, and the software has similar features. It'd be great if the AirView software had device signatures, but it appears that they're pretty receptive to feature requests through their forums. I'll definitely have to keep that product in mind as a recommendation to others. Thanks!

Wi-Spy USB Spectrum Analyzer (3, Informative)

bassman998 (922503) | about 4 years ago | (#32726534)

Metageek [] has a few products in their Wi-Spy USB Spectrum Analyzer family. The cheapest one (the 2.4i [] ) is $99, and the next model up (2.4x [] ) is $199. It analyzes the entire 2.4GHz spectrum using your laptop and lets you see potential sources of interference. The 2.4x version allows you to use their more advanced software which also has device signatures -- you can overlay signal patterns of various types of devices (microwave, cordless phone, wireless baby monitors, etc.) on top of the signal density graph in order to identify what's causing the interference. I use the DBx version (2.4 + 5GHz) at work, and it's great for helping to find problems.

Light Dimmer switch (1)

lyallp (794252) | about 4 years ago | (#32726542)

I had a similar problem but it was affecting ADSL.
It turned out to be a light dimmer switch.
Try wandering around turning off lights...

InSSIDer (0)

Anonymous Coward | about 4 years ago | (#32726548)

Might do the trick to figure out where the interference is coming from, if it's another wireless network. I've had it work with a Broadcom card in Windows 7 that wouldn't work with Netstumbler. Might work with yours.

Or you could get your hands on a WRT54G (borrow or cheap on eBay), install Tomato or something like it, and run the site survey tool. Figure out if there's some kind of channel overlap problem.

Have you tried lining your apt in aluminum foil? (0)

Anonymous Coward | about 4 years ago | (#32726558)

It protects against more than just aliens you know. Here's an example:

Back in the 80's (1)

codepunk (167897) | about 4 years ago | (#32726646)

Back in the mid 80's I would have been the guy you where looking for. The guy with a 4 element beam antenna that was nearly the size of my house roof. Running a 4K watt bi-linear amplifier on a old but great tube driven DAK radio. I could speak to god on a clear night with that rig. My neighbors however where not that happy hearing my key pinger blare across their tv sets.

WiSpy (1)

pestilence669 (823950) | about 4 years ago | (#32726650)

WiSpy + walking around = finding your noise
Load More Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Create a Slashdot Account