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Thread: 5 pictures.

  1. #1

    Default 5 pictures.

    A picture is worth a 1000 words they say, so 5 pictures must be worth...

    I recently purchased a WiSpy 2.4x Spectrum Analyser, but was initially greatly disappointed in its performance. (I am a retired electronics engineer with experience of large, expensive Spectrum Analysers). Figure 1 shows my initial results with lots of high level noise across the 2.4GHz spectrum. I thought that the WiSpy was defective and was about to return it for replacement. However, I decided to experiment further. The results of my experiments are below:-

    Fig 2 shows the noise is slightly reduced by turning off the WiFi scanning (from the Chanalyser WiFi menu).
    Fig 3 shows that the noise is totally removed by physically switching off the laptop WiFi.
    In Figs 1, 2, 3 no significant data is being transmitted. The rounded spectrum implies that just the SSID beacon is being broadcast.

    In Fig 4, catchup TV video is being streamed to a 2nd laptop in another room. The flat spectrum top indicates 802.11g transmission. Note from the waterfall display that the data is not continuous, but is downloaded in bursts as required. Laptop 1 WiFi is still off.
    In Fig 5, WiFi has been turned back on, but WiFi scanning is off. As before, the wideband noise has increased considerably.
    In Fig 6, which I am blocked from sending, the WiFi scanning was turned back on and the noise level increased even more.

    Both laptops are running Windows 7. Laptop 1 is a Dell Latitude E5520 and laptop 2 is an HP Pavilion dm1.
    The noisy results are not peculiar to the Dell. I get the same results if I fit the WiSpy to the HP.

    Conclusion.
    The WiSpy is working OK, but to view a clean spectrum it is necessary to turn off the laptop WiFi.
    Simply switching off the WiFi scanning via the Chanalyser menu is unsatisfactory.
    This information appears to be missing from the User Guides. I hope that others will find this information useful.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2

    Default

    Quote Originally Posted by bnichlsn View Post
    The WiSpy is working OK, but to view a clean spectrum it is necessary to turn off the laptop WiFi.
    That is correct. I leave Wi-Fi scanning on because I find out the amount of "interference" to be negligible compared to the amount of data that I can glean from the beacons. They may cause some activity here and there, but in the end I think they are worth it.

    Thanks for posting your results!
    Joel, Mobility+, ECSE, CWNE #233
    Technical Trainer
    MetaGeek

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