The twin antennas on access points and Peripheral Component Interface (PCI)-based interface cards can be tilted and rotated. Usually, they are most efficient when pointed straight up. If your laptop’s cardbus interface is not getting a strong signal, you can often improve it by rotating the laptop or simply sliding it over a few inches.

In theory, the signal will be strongest if the antenna points toward the access point or wireless router like a compass needle. Some of these cards now have more than one built-in antenna to avoid dead spots, but the rest have their built-in antennas oriented in the worst possible way: They are horizontal, and they are separated from the chassis of the laptop by half an inch or less.

This sends the radiation pattern up and down, which is fine if you happen to be upstairs from your access point. If you are downstairs from one, you’ll have a problem because access points have dead spots directly underneath.

Apple’s built-in interfaces deal with small-card coverage problems by placing a built-in antenna on the side of the liquid crystal display (LCD), which is vertical when being viewed. Other manufacturers are following suit.

If your environment is unusually difficult for some reason, you may have to resort to an external or add-on antenna, but lower-priced peripheral cards won’t come with accommodating sockets or plugs. If you anticipate this problem, buy a NIC that does have an antenna socket. (In late 2002, Linksys introduced an add-on antenna range extender.)

As standardized as these interfaces have become, none of the antenna jacks are of a consistent factor and intentionally so, thanks to FCC regulation section 15.203. It was intended to discourage experimentation by users. You must either buy the manufacturer’s own brand of antenna or search for an adapter at an electronics store.

Unfortunately, the radio frequency (RF) signal is attenuated somewhat every time it must traverse an adapter. It is natural for some folks to want to experiment and get the maximum range from their equipment.

This is one of the primary motivating challenges behind amateur radio, for instance, but good reasons exist for getting a ham license and experimenting that way instead of doing so with your Wi- Fi equipment. The reasons against experimenting with Wi-Fi apparatus are as follows:

• Wi-Fi interfaces were not designed to be tampered with.
• Doing so violates FCC regulations.
• You might ruin the equipment if you don’t make it less efficient.
• Letting your signal out lets others in.
• You don’t need to. It almost always works fine as is.

Putting an external antenna on your roof to cure a few dead spots below is counterproductive. The signal from the interface will be soaked up by a long transmission line and be cut every time it must jump a connector or adapter.

Omnidirectional antennas are least sensitive below. An antenna on the roof is subject to weathering, lightning, and water in the form of rain, fog, and condensation.

Water can be particularly troubling at 2.4 GHz. That particular frequency was originally chosen for microwave ovens because it was well suited for heating water, meaning that water absorbs it. Bolting a Wi-Fi antenna to your chimney may give you coverage all over the block on a sunny day, but hardly anything in a dense fog.

Also, if it works well in winter, it may gradually go deaf in the spring, as the trees put on foliage. Putting your access point next to a water cooler or an aquarium is an obvious mistake.

Your fish will stay healthy, but a large tank will act like a black hole.Window plants and potted palms are also mostly water. So are people, which is why you can block the link from a laptop simply by resting your arm against the interface card.

Even if all your workstations have an adequate signal from your access point, one other check you should make with your signal-strength laptop is to walk around the periphery of your home to determine where the coverage pattern ends. Believe it or not, too much signal spilling out to the street is not necessarily a good thing.

It can interfere with neighbors’ Wi-Fi networks, especially in high-concentration areas such as apartment complexes. A full rate of 11 Mbps can be maintained even if the reported signal strength is less than half the maximum. As mentioned repeatedly, a sloppy signal makes your access point more vulnerable to those on the outside.

Most laptops come with built-in Wi-Fi interfaces these days, and many employees carry them home as tools for the job. So an increasing number of users are equipped to find your access point and use it if you allow them to.

If you want to use a laptop at a great distance outside, temporarily place the access point antenna so that it looks out a window. It’s more likely that you will wind up placing your base station so that its signal is deliberately weaker.

If you need to connect a distant office, a backyard workshop, or a separate wired network, you can use a wireless alternative to stringing a long wire between buildings. A Wi-Fi bridge consists of two specialized base units that work together as a radio “extension cord” for a wired network.

Their specific purpose is to extend the range of a wireless network or fill in a dead spot. They can be used to connect a wired hub or switch or any Ethernet-compatible wired peripheral also, such as a printer or distant server. Together with an amplified transmitter and a focused, directional antenna, a network’s straight-line range can be stretched for miles with these bridges.

Another factor to consider, especially for base stations, is jamming. Wi-Fi shares the upper part of its 11-channel frequency band with microwave ovens. Modern ovens are well shielded, but don’t ask for trouble by putting your access point on top of a microwave or even in the same room with one.

Other sources of radio interference include older cordless phones, wireless video cameras, and some baby monitors. Check the label to see if they run in the 2.4 GHz band, and if they do, move them or the base station.

It’s not a good idea to plug the base station into the same outlet with one of these either, since the mutually interfering signals can leak through the power cords. Interference may not stop your link entirely or all the time, because it was designed to be robust. But noise on the air close to your Wi-Fi system’s ear can force it to slow down.

If you examine your configuration screen’s signal report, and it shows a strong signal but slow throughput, you should turn off suspect sources until the problem clears.