As a quick check you could turn on a microwave oven. This will generate radio waves across the entire 2.4 GHz spectrum. An even better test would be a 2.4 GHz cordless phone – most seem to transmit a continuous signal in the vicinity of channel 1.
802.11 is a robust, wireless communications protocol that was designed to accommodate multiple 802.11 devices within close proximity. You could install multiple APs within a building and they would all work fine (for the most part) -- even if they were configured to use the same channel. That is, 802.11 devices and networks know how to play nicely in a crowded backyard. (NOTE: problems do arise, though, when large files are transferred or video data is streamed over the wireless network).
In order for the analyzer to detect a wireless device, that device has to (a) transmit continuously, and (b) the transmitted signal has to be strong enough and within range of the receiving antenna. 802.11 APs satisfy criteria (b), but unless the network they manage is actively transmitting data between devices then the only transmissions are occasional beacon packets from the access point. The beacon signals alone are not sufficient for the analyzer to pick up -- they are short in duration and occur approximately once every 100 millseconds. This is good because it means that 802.11 access points don't generate a lot of signal activity that could interfere with other types of wireless devices that operate in the 2.4x and 5.x GHz bands.
What kinds of devices could interfere with a Wi-Fi (i.e. 802.11) network?
When setting up a wireless network or troubleshooting a poorly performing one -- usually it's the non-802.11 devices that you have to worry about most. Things like wireless video or security cameras, bluetooth devices, cordless phones, wireless monitors, security systems, RF Excited lighting (Fusion lighting), wireless broadband (i.e. WiMAX), etc. Also, large file transfers and video streaming between 802.11 devices could degrade the performance of other wireless networks in the vicinity.
Using a 2.4 GHz cordless phone as an example, 3 important parameters that will affect how a device appears to the analyzer include the following -- the strength of the phone’s transmitted signal, the phone’s distance from the analyzer’s receiving antenna, and the orientation of the analyzer’s antenna relative to the radio waves transmitted by the phone. Changing the orientation of the analyzer’s antenna by rotating the device could change the results that are displayed. Another subtle effect, which is difficult to quantify but which you should keep in mind, is that when you move the transmitting device to different locations this will change the way the RF waves bounce off of objects and walls -- which could affect the power of the waves on the receiving antenna and the degree to which it is detected as interfering RF energy.
While the measurement is being performed temporarily power-off your known access point(s) – otherwise, legitimate network activity occurring over that channel will be interpreted as interference and could hurt that channel’s chances of being selected as the ‘Best’ channel.
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