WiFi networks can reach only so far.

The range of wireless equipment such as the radios and antennas that are built into consumer equipment such as the AirPort Extreme Base Station can vary from network to network, even minute to minute. But when one node of a WiFi network is too far from another, communications between the two break down, and your network doesn’t work.

While WiFi signals are supposed to reach 150 feet in any direction from a gateway, that optimistic figure is rarely reached indoors. One common cause is absorption. Building materials between two points can soak up so much of the signal that one device can’t detect another. Brick is particularly bad for WiFi because brick retains water, which readily absorbs WiFi signals.

As a result, a gateway that delivers a perfect high-speed connection to a laptop from 500 feet away when it has a direct line of sight might be invisible to a laptop that’s 50 feet away when there’s a brick wall between them.

There are two main indicators that your wireless network is having range problems. First, WiFi networks you know are there don’t show up in the wireless menu. Second, when you do connect to a network, the wireless icon in the system menu bar shows just one or two signal-strength bars and frequently slips to no bars.

You can also check signal strength with iStumbler, a utility that shows you a list of all in-range WiFi networks and Bluetooth devices. Among other details, iStumbler shows you percentage values for the signal and noise of those nearby networks. If iStumbler shows a high noise value, then interference could be the reason you’re having network problems. But if the noise value and the signal value are both low, then range is the problem.

If iStumbler indicates that you’re having interference problems, you can solve them by following the advice here. If the problem really is range, there are several easy ways to solve it.

Tomorrow, I’ll share with you more solutions to resolve the weak wireless signal.