WiFi Stumbler Scans Local Wi-Fi to Find an Interference-Free Channel
If you've been having trouble with your wireless signal the culprit might be interference from other wireless routers in the area. Free web-based tool WiFi Stumbler will show you which channel is least likely to cause interference.
WiFi Stumbler uses your computer's Wi-Fi antenna to scan local access nodes. You can do a wide open scan or narrow it down by the type of encryption, the manufacturer, the radio type, frequency, or channel.
When you're done with the scan you're presented with both a detailed listing and a chart showing the number of nodes. Using this information you can then switch your router to a less occupied channel—every router I've ever purchased has been set to Channel 6 for some reason and just getting it off 6 has been a huge help in every instance.
Have a favorite tool for tweaking your Wi-Fi? Let's hear about it in the comments.
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WIFI stumbler scanner
How to chose the right WiFi channel
By , in Wireless, posted: 26-May-2007 20:58
With increasing density of WiFi networks we're facing more and more WiFi networks popping up in our neighbourhoods, which may impact performance on your WiFi network, if frequencies interfere.
To scan your neighbourhood for active WiFi networks use "Netstumbler", an easy-to-use WiFi scanner for Windows. After starting Netstumbler will show you all discovered networks inlcuding the used channels.
Two WiFi networks operating on the same channel are forced to share bandwidth, as they can't "talk" simultaneously, which halves each network's bandwidth. In order to evade this effect, you need to change your access point's channel, but taking the adjacent one won't do it, as WiFi channels are arranged in an overlapping pattern, as you can see from this scheme:
Channel 1 overlaps channels 2 to 5, which therefore may not be used for a neighbouring WiFi network. If channel 1 is used, you should switch to channel >=6.
There must be a spacing of at least 5 channels (or more) between each WiFi network in order to avoid interferences.
Further, if all your WiFi-devices support 802.11g (the 54 MBit/s WiFi-variant), you should set your router to 802.11g-only mode, as the 802.11b-compatibility impacts on bandwidth and range even among 802.11g-devices. Another possible cause of low performance may be proprietary WiFi acceleration modes like "SuperG", "MAXg", "125 High Speed Mode" or "SpeedBooster", if not all devices in your network support the very same mode, why you should disable those.
Also note that a lot of cordless phones in NZ operate at the 2.4 GHz band like Wifi and so most of them cause interferences WiFi, that can't be avoided by a channel change, since those phones use a very broad spectrum or perform permanent frequency hopping.
If you own a 2.4 GHz phone, try switching it off and removing the power supply of it's base station. In case your wireless signal improves, replace your cordless phone with a new one operating at 1.8 GHz or 5.8 GHz.
Other related posts:
NZ's hopeless wireless market
To scan your neighbourhood for active WiFi networks use "Netstumbler", an easy-to-use WiFi scanner for Windows. After starting Netstumbler will show you all discovered networks inlcuding the used channels.
Two WiFi networks operating on the same channel are forced to share bandwidth, as they can't "talk" simultaneously, which halves each network's bandwidth. In order to evade this effect, you need to change your access point's channel, but taking the adjacent one won't do it, as WiFi channels are arranged in an overlapping pattern, as you can see from this scheme:
Channel 1 overlaps channels 2 to 5, which therefore may not be used for a neighbouring WiFi network. If channel 1 is used, you should switch to channel >=6.
There must be a spacing of at least 5 channels (or more) between each WiFi network in order to avoid interferences.
Further, if all your WiFi-devices support 802.11g (the 54 MBit/s WiFi-variant), you should set your router to 802.11g-only mode, as the 802.11b-compatibility impacts on bandwidth and range even among 802.11g-devices. Another possible cause of low performance may be proprietary WiFi acceleration modes like "SuperG", "MAXg", "125 High Speed Mode" or "SpeedBooster", if not all devices in your network support the very same mode, why you should disable those.
Also note that a lot of cordless phones in NZ operate at the 2.4 GHz band like Wifi and so most of them cause interferences WiFi, that can't be avoided by a channel change, since those phones use a very broad spectrum or perform permanent frequency hopping.
If you own a 2.4 GHz phone, try switching it off and removing the power supply of it's base station. In case your wireless signal improves, replace your cordless phone with a new one operating at 1.8 GHz or 5.8 GHz.
Other related posts:
NZ's hopeless wireless market
Q: What is the WiFi Stumbler?
A: The WiFi Stumbler is a browser-based wireless scanner tool that detects 802.11 wireless networks and displays useful information about the networks in an easily searchable, intuitive web interface. WiFi Stumbler can be used to optimize wireless network coverage, troubleshoot performance issues, detect rogue APs and perform basic pre-deployment site surveys.
Q: Can I use WiFI Stumbler when I am not connected to the Internet?
A: If your browser supports offline mode (currently only Firefox), then it can load WiFi Stumbler from its offline cache. This means that WiFi Stumbler will work in these browsers even when you are not connected to the Internet, as long as your wireless card is enabled. Simply visit the Stumbler page using Firefox once you are connected to the Internet. The site will ask for permission to use offline storage. Grant this permission, bookmark the page and you can revisit whenever you need to use WiFi Stumbler.
Q: How does the WiFi Stumbler work?
A: WiFi Stumbler captures data about nearby wireless networks from your computer's wireless card and displays it as a web page. It can even work when you are not connected to the Internet if your browser supports offline mode (currently Firefox only).
Q: Why is Stumbler a web-based tool instead of standalone, downloadable software?
A: By running in a browser, there is no need to download software to your computer. This makes it very easy to load and use since no software installation is required. It also can run on either a PC or Mac, unlike most downloadable software applications. In addition, as we will be continually adding new features to Stumbler, you will automatically get the latest version of the tool each time you reload the page.
Q: The WiFi Stumbler doesn't load on my computer/in my browser. Why not?
A: WiFi Stumbler requires Java support and does not currently support Linux. If your browser does not support Java or you are running Linux and you try to load WiFi Stumbler, you will receive an error message in your browser window. Currently, Google Chrome for Mac does not support Java so it will not run WiFi Stumbler. WiFi Stumbler is also currently a beta stage tool; if you encounter other problems getting Stumbler to load, please let us know using the Make a Wish box at the bottom of the page.
Q: I am getting an error message telling me that my browser doesn't support Java, but it does. Why isn't it working?
A: In order for WiFi Stumbler to load properly, you must be using a browser that supports Java, have the necessary plug-ins installed, have enabled Java and might need to install the latest version of Java (depending on your browser).
You can check to see if Java is working properly by going tohttp://www.realapplets.com/tutorial/HelloWorld.html. If you see the "Hey hey Hello world" applet inline in the middle of the page, then Java is installed and enabled in your browser. If you do not see it, then check to make sure that you have the Java plug-in installed. If the plug-in is installed and the page will not load, then there are a few other items to check.
For Firefox (recommended for support of offline mode):
If you are running Firefox 3.5.7 and earlier, check under Tools, Options, Content (Windows) or Preferences, Content (Mac OS X). Make sure that the checkbox "Enable Java" is checked.
If you are running Firefox 3.6, you will need to make sure that you have Java version 6 Update 10 or newer in order for WiFi Stumbler (or any other Java-based application) to run. You can get the latest version of Java at java.com.
You can check to see if Java is working properly by going tohttp://www.realapplets.com/tutorial/HelloWorld.html. If you see the "Hey hey Hello world" applet inline in the middle of the page, then Java is installed and enabled in your browser. If you do not see it, then check to make sure that you have the Java plug-in installed. If the plug-in is installed and the page will not load, then there are a few other items to check.
For Firefox (recommended for support of offline mode):
If you are running Firefox 3.5.7 and earlier, check under Tools, Options, Content (Windows) or Preferences, Content (Mac OS X). Make sure that the checkbox "Enable Java" is checked.
If you are running Firefox 3.6, you will need to make sure that you have Java version 6 Update 10 or newer in order for WiFi Stumbler (or any other Java-based application) to run. You can get the latest version of Java at java.com.
Q: Why does the bar graph at the top of the screen appear blank?
A: If you are viewing WiFi Stumbler in IE8, make sure that Compatibility Mode is turned on (under Tools). This should allow the graph to render properly.
Q: Why do some networks appear in gray and others are in dark gray?
A: Networks appearing in light gray were not detected in the latest scan but were detected recently. The last time a network was detected by Stumbler will appear under the "Last Seen" column. If an access point stops broadcasting its SSID (eg. it was unplugged) or local RF interference or environmental obstructions prevent broadcast beacons from reaching your client then the network might "disappear" for a few seconds, in which case it would turn light gray until it is picked up in another scan.
Q: Why don't all of my network broadcast SSIDs appear in the Network List?
A: If an SSID is broadcasting in 5 GHz only and the wireless card in the client on which you are running Stumbler on does not support 5 GHz then the SSID will not appear in the Network List.
A: If a network owner has disabled SSID broadcasting on their network, then the SSID is now "hidden". What that means is that the SSID name is no longer included in the the periodic broadcast beacons from the access point that alert local clients to the network. This is sometimes done as a security measure, as only clients that know the name of the network (or who use "sniffer" software programs) can associate to the network.
Q: Why does the same SSID appear twice with different MAC addresses?
A: If there are multiple access points in a network all broadcasting the same SSID, each AP will appear individually in WiFi Stumbler showing the same SSID. Also, if an access point contains multiple radios that are broadcasting the same SSID, each radio will appear individually in the WiFi Stumbler network list.
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