Choosing the Right Antenna

Choosing the right antenna can be a daunting task. We have compiled some basic theory to help in your decision.

The 2 most important factors to consider when purchasing an antenna are the Mounting Position and the Radiating Pattern.

Mounting Position

An antenna needs a large uniform metal surface beneath the radiating elements to perfom correctly. This is referred to as the "Ground Plane". Therefore the best position to install an antenna is in the centre of a metal roof, however, this is not always possible. i.e on a mirror or bullbar. In this case a "Ground Independant" antenna should be used to give the correct radiating pattern without a metal surface

Radiating Patterns

It is also important to understand the relation of an antenna's gain to it's radiating pattern. The diagram below shows the radiating pattern of different gain antennas. As the electrical design of the antenna is modified to increase the gain, the omnidirectional patterns is squashed in the verticle plane, therefore furthering the signal's coverage. A high gain antenna will therefore give increased coverage on flat terrain but the elevation will be limited making it less suitable in mountainous country.