The behavior of your radio could vary. If you’re associated at 2.4GHz the channel would be based on the AP you’re associated to and duty cycle would vary with the network activity. If your connection is good you wouldn’t probe much, if at all. If you’re associated at 5GHz you may occasionally probe on 2.4, but otherwise you wouldn’t see your 2.4GHz radio. If you’re not associated your laptop would probe frequently on all channels and duty cycle would alternate between probing and listening.
FWIW, my first thought was exactly what Jake suggested, but I didn’t think the fall-off at the edge of the channel was quite sharp enough to be from a properly functioning nearby radio. That shoulder should be about 30dB down instead of 10dB. It also seems way too strong 65MHz away at channel 14. Even if the noise floor is -70, the interference is clearly still falling off at channel 12. On the other hand, -20dBm is really strong, so either the malfunctioning radio is really booming or you’re very close to it. When our Proxim’s failed they behaved as if they were using the full 100mW Tx power, but even at that power you would have to be within 15 feet of the radio to get -20dBm. Let us know what you figure out. It should be a learning opportunity either way. From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]] On Behalf Of Gray, Sean Sent: Wednesday, March 08, 2017 4:54 PM To: [email protected] Subject: Re: [WIRELESS-LAN] 2.4 GHz Interference Just curious, but if my Surface was the cause of the problem and I always used the same set-up for the Wi-Spy, wouldn’t I always see this signature? This is something that seems to occur quite randomly so far. From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]] On Behalf Of Jake Snyder Sent: March-08-17 2:21 PM To: [email protected] <mailto:[email protected]> Subject: Re: [WIRELESS-LAN] 2.4 GHz Interference Try putting your laptop in airplane mode. My guess is the SpecAn is in very close proximity to the laptop. That horizontal slope indicates the wispy is VERY close to a wifi device (aka your surface). That's why it looks like OFDM, because it is. Getting your wispy close to an AP will look the same. Sent from my iPhone On Mar 8, 2017, at 1:56 PM, Gray, Sean <[email protected] <mailto:[email protected]> > wrote: Nope, the spectrum analyzer is going directly into a Surface Pro 2. From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]] On Behalf Of Jake Snyder Sent: March-08-17 1:30 PM To: [email protected] <mailto:[email protected]> Subject: Re: [WIRELESS-LAN] 2.4 GHz Interference Are you using a USB 3.0 hub? On Mar 8, 2017, at 1:23 PM, Jason Heffner <[email protected] <mailto:[email protected]> > wrote: I’ve seen something similar when running some of the older Cisco controllers. If you ruled out everything else and are starting to look for devices causing interference I'd check out some of your wireless mic systems. We had some 800Mhz that we had to salvage that were causing harmonic distortion on 2.4GHZ similar to this on the lower channels. On Mar 8, 2017, at 2:32 PM, Gray, Sean <[email protected] <mailto:[email protected]> > wrote: Hi Everyone, I’ve been doing a little spectrum analysis around campus and I keep seeing the same interference signature in different buildings. I was wondering if anyone had seen anything like this before. It is typically visible for well over 10 minutes at a time and then it completely disappears. Thanks Sean Sean Gray | B.Sc (Hons) Voice, Collaboration & Wireless Network Analyst ITS, University of Lethbridge ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at <http://www.educause.edu/discuss> http://www.educause.edu/discuss. <Unknown Interference Source.PNG> ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss.
