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Tracking Down Wi-Fi Interference?
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?"
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.
"Who is the Journal of Quantum Physics going to believe?" --Stephen Hawking
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.
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.
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.
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.
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.
-Todd
Omne ignotum pro magnifico.
Check for any satellites that track overhead at that time.
I remember when they used to open electric garage doors around the neighborhood....
Tried http://www.safelivingtechnologies.ca/rf/Products_RF_Shielding_Paint_HSF54.htm 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.
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
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.
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.
Will
This is very interesting - I've been experiencing extreme wifi interference issues since I moved to my new place (about a year ago) in Brooklyn. My neighborhood is not known as one of the more crime free boroughs in the city, and presumably as a result of that reputation, the neighboring building's backyard has an always-on sodium light at the ground floor (of the brightness and sickening color of your typical street-side sodium lamp). My bedroom (also on the ground floor, facing the backyard) experiences the worst effects of a very obvious latent interference in the area, that is lesser (but not gone) in the 5GHz range, but renders wifi nearly unusable in the 2.4GHz band (with the added interference of several other networks in that frequencey range close by - though there is 3 channel free band). I wonder if the sodium lamp is the issue...
The secret to creativity is knowing how to hide your sources. - Albert Einstein
Amateur are a Secondary User of the band and must accept interference from the industrial, scientific and medical (ISM) radio users.
Yes, we have priority, but we're not pricks. If someone came to my house to ask if my radio equipment is causing WiFi signal dropping from area houses, of course I'd be happy to help by solving the problem. Helping my neighbours change the WiFi channels or installing directional indoor antennas for them ($10 from DealExtreme) could help in this issue...
There are a lot of things that can hose WiFi. It is unlicensed spectrum. I wouldn't be surprised if you hooked up a wireless camera receiver in the frequency range of your wifi and got a peek inside somebody's house.
Sometimes the software on a pc or device shows it when you select a Wireless Network. Sometimes it doesn't.
Network Stumbler does.
Caveat: IBM customer engineer involved -> my tech-ish brother -> me. Take with requisite amount of salt.
Was shortly after the "foreign attachments" decision in an IBM antitrust case, which required IBM to post specs and allow other companies to build and plug in peripherals. During that period a bunch of multivendor projects got started - and many were the rounds of finger-pointing when it came time to integrate the products of a half-dozen or so vendors into a delivered system. This was one of 'em.
The system was being integrated at the install site - a building at an airport. Every piece had worked just fine in the vendors' labs. Nothing played well at all on the final site. Was a madhouse of vendor engineers trying to get things to play together.
At one point one of the engineers got sufficiently bugged by a flickering fluorescent light that he decided to do something about it. He got a ladder and turned off the lights preparatory to doing the fix - but the tube kept flickering. "Hey, guys. Look at this!"
Turned out the airport's search radar was right next door to this wooden building. Anyone familiar with transistor circuits and the number of volts-per-inch of signal strength needed to light an unpowered fluorescent lamp knows what that means.
They paneled the wall with aluminum. Everything started working. All shook hands and went home.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way