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Thread: help with identifying interference

  1. #1

    Default help with identifying interference

    I am trying to confirm interference issues. On the attached graph, I see minor bluetooth interference, but do not understand why I get signals across the entire band when downloading a large file. This pattern only occurs at one location in the site. Could it be caused by reflection off the solar panels installed on the roof above this location? Network link is on channell 11. Any help would be greatly appreciated!
    Last edited by MetaGeek; 10-20-2009 at 05:20 PM. Reason: added image

  2. #2

    Default spectrum

    What type of download is occurring, what type of devices is the download from/to. I don't see this creating a problem, especially on the lower bands. Do you have a scan without a download to compare, or do you have a recording you can submit that has a note or timestamp on when the download started?

    This would likely help determine if the download is creating the noise, and then if that is the case we can determine if the device is responsible. It may take some more tests/scans, but sometimes that is what it takes.

    my $.02

  3. #3

    Default I'm downloading a large

    I'm downloading a large (500MB) test file off the web (http). The access points are 802.11B and you can literally watch the -90dB broad spectrum line fill in the second a download begins (but only in this one location). I will attach the wdr and another wdr without the download. Without it, the band is still noticeable (other laptops connected to the AP) but far less pronounced). Connecting from a Lenovo T500 (Intel 5100 AGN) to a Cisco Aironet 1200 AP (channel 11, WEP encryption)

    You can find the files here:

    Hopefully the names are self explanatory. I appreciate the help!

    The download begins ~1:20 into the recording.
    The download ends ~9:30 into the recording.
    A second download starts up ~17:38.

  4. #4

    Default I couldn't access that link, wanted login/password

    can you update it or provide some type of access?


  5. #5

    Default Sorry here's the public

    Sorry here's the public link:

  6. Default I don't see anything

    I don't see anything necessarily wrong with the shape of the recording. A lot of access points take up the entire band. We have some in our recordings library.The solar panels could definitely be a problem due to multipath.* Any flat and metal object could be problematic.* I definitely don't see much interference happening.Was this capture created next to the AP or next to the client experiencing connectivity issues?

  7. #7

    Default It was taken next to the

    It was taken next to the client having the connectivity problems. The interesting thing here is that the recordings at other locations in the building do not show activity across the entire band, nor does this behavior happen at other locations (ruling out my equipment causing the issue (i think)). Could multipath cause this? There is also a transformer about 20 yards away directly in line of sight through a window. Any way that could be creating intermittent drop outs?

  8. #8

    Default Also of note, this office

    Also of note, this office has a wire-mesh inbox/outbox and pencil holder on the desk, could these be messing with the signal?

  9. Default If a signal was causing

    If a signal was causing intermittent dropouts, you would see it with your Wi-Spy.* Can you confirm that the access point is indeed below -100dBm in that capture?* That would be my number one guess at this point.* For a good solid connection you want about -60dBm.

  10. Default No. Shouldn't be a problem.

    No. Shouldn't be a problem. But feel free to use "poor wi-fi connection" as an excuse to get them to clean their desk

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