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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?"
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.
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.
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.
We had a lot of trouble with wireless disruptions around our office - I eventually bought a Wi-Spy (http://www.metageek.net/) 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.
Here's a cheap build-it-yourself spectrum analyzer: http://hackaday.com/2010/03/17/im-me-spectrum-analyzer/ The IM-ME can be had for about $15 or so, and is purportedly very hackable.
John
airodump-ng --showack -w output mon0
take note that all your idiotic neighbors all use channel 6 for everything.
decrypt WEP/WPA keys for router.
connect to router, login using default (never changed) credentials.
upload notepad.exe to router as a firmware upgrade.
no wireless devices running in range of your equipment.