If you havent got Network Stumbler for Windows -NetStumbler to its friends - you should. This utility can be found at www.netstumbler.com. Net Stumbler is an all-purpose software tool that, among other things, lets you detect unauthorised rogue access points in your workplace or other networks that may be causing interference on your network. You can even use it for war driving (hunting around looking for open wireless access points).
Its also very useful for analyzing your broadcast coverage - it can find locations with poor coverage in your wireless network and help you position your access points antenna to improve the reach of your wireless network.
NetStumbler includes a most useful field strength and signal-to-noise ratio display. By wandering about with a notebook running NetStumbler, you can easily detect weak spots and dead spots in your APs (access points) coverage, as well as determine the edge of an APs useful range.
NetStumbler is also useful in testing the relative effectiveness of Wi-Fi antennas, by placing a laptop running NetStumbler in a fixed position and then aiming antennas at it from some distance away. If the antennas are all at the same distance from the PC, NetStumblers readings will accurately reflect how well they work with respect to one another. Highly recommended if you have reception problems.
Use ping to compare latency
If you dont have or want to get NetStumbler theres always good old Ping (packet internet groper), the humble command-line TCP/IP diagnostics tool. While most Wi-Fi devices provide a rough indication of signal strength you might find it helpful to use Ping to measure the response time or latency across your wireless link and orientate your access points antenna to achieve the smallest time on average. To do this, open command prompt, click Start, All Programs, Accessories and then click Command Prompt.
At the C: prompt enter the following command to run Ping indefinitely: ping 192.168.0.1 -t
Here 192.168.0.1 is the IP address of my access point -- yours will most probably be different, so run IPCONFIG at a command prompt -- normally the AP will be the same as the gateway. You will then see ping responses on the screen. Look across to the time field and adjust your access points antenna (or indeed the whole AP, cable lengths permitting) to achieve the smallest time in (ms) milliseconds. Enter a Ctrl, C to terminate the ping.
replace your antenna for better coverage
If your AP doesnt reach those parts of your building youd like it too, consider fitting a higher gain antenna. The standard antenna that comes with an access point usually has a low gain (around 2dB). If the access point has a removable antenna, then replacing the default antenna with a higher gain omnidirectional antenna boosts range significantly, typically adding 6dB to the system, or about a four-fold increase in signal power.
For about £25 Ive fitted a large 6dB antenna (made by Linksys) to my trusty Netgear DG834G to boost its reach by about 25 percent.