Final Thoughts

Focused Reflectors

The basic idea is to shape a piece of hardware cloth into a parabolic reflector, and put the antenna of your access point at or close to that focus. The parabola doesn't have to be a parabola of rotation -in other words, a parabolic dish-like those used for receiving satellite TV, especially in the old days. (Remember when neighborhood wars were fought over people who wanted to mount 7-foot satellite parabolic dish antennas in their backyards?) It can be nothing more than a flat piece of metal shaped to parabolic form in the horizontal dimension only. The focus of such a parabola is a vertical line, not a point, but if you park a Wi-Fi omnidirectional antenna at that focus line, the reflector will focus incoming microwaves onto that antenna, and focus the microwaves coming off the antenna into a beam.

In case you can't yet see in your mind what I'm talking about, the finished reflector is shown in Figure 17.2, along with a D-Link DWL-900AP+ access point. In the photo, the antenna of the access point is positioned so that it falls precisely at the reflector's linear focus. Microwave energy leaves the access point's omnidirectional rubber antenna in all directions. The energy radiated back toward the reflector bounces back and forward, along with the energy radiated in a forward direction. The parabolic shape of the reflector confines most of the energy coming off the antenna into a relatively narrow beam. Position the reflector carefully, and you can aim that beam in any direction you choose. I aimed it toward the corner of my living room, down along the long axis of my house, and the field strength there came up radically (see Figure 17.3).

Figure 17.2: A Parabolic Mesh Reflector.

Figure 17.3: Aiming the Beam into the House.

The reflector had reshaped the AP's field to something longer and narrower than its original shape. I discovered that I had created a new dead spot at one corner of the house, but that wasn't a potential work location.