Which Antenna Build

The antenna you build depends on a few things:

• Your skill level;
• Radiation pattern;
• Weatherproofing;
• Materials and tools available.

Most people will ignore the first point, and to a degree, the last point. An important point to consider is what you will use the antenna for. If you're doing this for fun or learning, the antenna you choose is pretty much immaterial. If you plan to put the antenna into production, you need to consider the radiation pattern of the antenna you require, and find the design most suitable.

An antenna is not a mythical device that boosts the power of your wireless gear. Imagine it like a pair of binoculars. Without them, you can see most things in front of you. With them, you can only see a small section of the area in front of you, but you can see it clearly. An antenna merely focuses the radio waves in the direction you require.

Antennas are usually referred to as either omni-directional (often shortened to omni) or uni-directional (often shortened to directional). Omni-directional antennas throw the signal out in a big 360 degree circle, often described as a doughnut. As the gain of the antenna increases, the doughnut gets squashed until it eventually looks like a pancake. The distance between the edges of the pancake is much greater meaning a longer range, but the pancake is thin, so alignment becomes more important.

A uni-directional antenna throws the signal in a single direction, in a way somewhat similar to a zoom lens on a camera. In the same way that a bigger zoom on a camera enables you to see further, a bigger gain antenna allows you to communicate futher away. As with omni-directional antennas, the higher the gain, the more critical the alignment becomes.

To sum up, if you're going to build an antenna to connect to the Bristol Wireless network, you are best advised to build a directional antenna. Find the one that you prefer, and build it. You may wish to discuss this further on the mailing list, where more specific advice can be given.

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