I had been bugging my friend who owns a local Deli for years to add free wifi so his customers could come and do some work while eating or having their morning coffee. When he finally agreed, what I thought would be a 30 minute setup turned into a serious scooby-doo mystery.
I setup the router as you would normally, and when plugged in, everything worked as planned, but when I tried to connect wirelessly. I could see the acess point, but my computer just wouldnt connect. Then, I would see the access point come and go. I tried the usual changing of channels and surveying what other stuff was going on on channels 1-11, but nothing worked. We returned the router thinking it was a hardware problem, but on the 2nd router, the same problem happened.
This time I took the router home and it worked fine, there was something weird about being in the Deli that was causing the problems. We thought it might be his wireless phones, so we unplugged them all and took out the backup batteries, but no luck.
We later discovered that the router seemed to work fine during off hours (not 9-5 mon-sat), but at 9am mysteriously it would just crap out. I was doing some testing one morning when I saw the Jeweler next store come in, and just when they came in, the thing stopped working. So we asked, what did you turn on, they said nothing, just the lights! My brother who makes his living doing this sort of thing (building way complex wireless networks for police, fire etc) said he would bring his Spectrum Analyzer the next time he came up, and that with his directional antenna, maybe we could track it down. The first time he came, it was a Sunday and unfortunately the problem was gone, so he couldn't find anything, everything was working great.
The next time we got there on a Saturday morning at 8:45 am and everything was working great, we watched for the Jeweler and sure enough, about 10 minutes after they came in, the problem started happening. We knocked on their door to ask what they just turned on, and they said "Nothing" again, we asked if we could bring in our Spectrum Analyzer, and after some negotiations with the manager she let us in (good think the Deli Owner knows them well), after about 5 minutes of walking around, my brother points up the the top left corner of a side room and says, whats that? (pointing to a wireless security camera), thats the source of the interference. We asked the guy if he had turned it on, he said no, its always on. What we figured out was its motion activated, so it goes to sleep during off hours, but once a employee or customer walks by, it turns on and starts transmitting. It turns out the Jeweler, was taking all the wifi spectrum, he was running his router on Channel 1, one camera on 6, and another on 11. The bad thing about these wireless security cameras is they dont show up on your computer when you are looking at whats out there, so you think, hey channel 11 should be clear. Also 802.11 networks generally get along better because of the protocols, but this camera was just totally blowing out the spectrum.
So the end solution is to, help the guy wire this camera, or buy him a newer 5.8 ghz
camera that will not interfere with the Deli wifi network!