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Posted by:greaneyr
Subject:Channel details detects activity on unused channels
Date:23:58:40 13/06/2011

> > Hi all
> >
> > I'm trying to understand the channel details screen a little better and thought I'd ask in here as I can't seem to find much explanation in the docs. When I go to the channel details screen (with channel hopping enabled) initially I see signals only on the channels I know have active access points on them. However, over time I gradually see activity on all 11 channels. I'm trying to understand why this is. I live in a sparsely populated area, and I know what the RF environment is like here. If kismet is picking up other access points on other channels, 1) the signals from them would be very weak and 2) there would not be enough to fill all 11 channels. None of the channels are 40MHz bonded channels either.
> There's a lot of spread - nominally an AP will leak over 3 channels easily, and often over more. Throw in multipath, reflections, and probably a driver timing error here and there where the driver tags a packet with the wrong frequency, and you'll get a slow creep.
> Look at the network details for your detected networks and you'll see the breakdown of what frequency it was actually seen on.

Thanks, that explains it. A lot of it was from the autogroup probe, originating from wireless clients around this area, presumably).

> > What I actually want is a device that can hop from channels 1 through to 11 and report the RSSI of whatever it hears, not just the strength of a valid 802.11 frame. This isn't what I'm seeing with kismet, is it? If it is, then there is potential to extend on this.
> You can kind-of-sort-of use the channel list as a spectrum analyzer, but it can only ever see 802.11 sources, so it's not going to help you identify non-dot11 interference. Your best bet for planning from a pure dot11 standpoint is to just work from the advertised channels.
> Your 802.11 card generally can't do this - it only reports dot11 packets. You want a spectrum analyzer - look at the wispy, for example. the ubertooth one also does spectrum and gets you bluetooth capture with kismet, too.

Thanks, yeah that's pretty much what I figured. I was just testing the water in case there's a cool way to do it using something free.

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