Okay, enough people commented on this that I had to dig out my documentation. FWIW, this is what my co-worked documented. My previous summary was not totally accurate. This was discovered by one of my co-workers, not myself.
-----snip-------- From: [EMAIL PROTECTED] (name withheld to protect against spam) Subject: Some Occupancy Sensors May Cause WiFi Interference So what interferes with 802.11b/g wireless? So far the list seems to be short; microwaves, 2.4 GHz cordless telephones, existing WiFi or Bluetooth equipment...... nuclear reactors!? Now add some occupancy sensors to the list. Specifically, Hubbell MyTech 24KHz ceiling mount sensors, manufactured about ten years ago. I've attached a picture of a newer model; the one that I had problems with is shaped more like a square. They're used to turn lights on and off when people enter large rooms and to regulate heating and air conditioning. 24KHz doesn't sound like WiFi right? Most wireless devices have emissions at some multiple of their operating frequency, in this case 10x. This is called a harmonic frequency and normally these emissions are filtered out. Ten years ago there wasn't much going on with the unlicensed ISM band so my best guess is that the 2.4 GHz harmonic was not filtered out to save costs. I first observed the interference using our Surveyor software although Surveyor did not detect any wireless devices. Curiously, NetStumbler detected an infinitely increasing number of wireless MAC address on an invisible SSID, all operating on channel 10. If I place the NetStumbler tool next to one of the sensors, the SNR goes off the charts every time I wave my hand in front of the sensor. A new random MAC address often times pops up. The MAC addresses aren't registered with any specific manufacturer. They start out with 02:00 and are random for the remaining characters. It might be that NetStumbler is attempting to treat the interference as an actual WiFi device. Anyways, it's something to look out for! -----snip-------- Mark Lachniet _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
