477 MHz, 26 MHz, 27 MHz, mobile phone, AM/FM, antennas
Manufactured to exacting high standards to accessorise the GME range of market leading radios. Suitable for all applications whilst offering exceptional performance, reliability and value.
Two important factors when choosing an antenna are the mounting position and the desired radiating patterns for the terrain inwhich the antenna is to be used.
An antenna needs a large uniform metal surface beneath the radiating elements to perform correctly. This is referred to as a ‘ground plane’. Therefore the best position to install an antenna is in the centre of a metal roof, however, this is not always possible and installation on a bull bar or mirror mount is often necessary. In this case a ‘ground independent’ antenna should be used to give the antenna its desired radiating pattern without a metal ground plane.
Radiating pattern on a flat metal surface
The direction of a ‘non ground independent’ antenna radiation pattern varies with the vehicle mounting position as shown right.
Rear – Strongest to the front, weak to the rear.
Left – Strongest to the right, weaker to the left (Antenna right – vice versa).
Centre – All directions equal (best).
The antenna to suit the terrain
Lower gain antennas are more suited to hilly terrain where reception does not depend on the angle of the antenna, as shown in figure 1 of the brochure linked below.
It is important to understand the relation of an antenna’s gain to its radiating pattern, as shown in figure 2 of the brochure linked below. As the electrical design of the antenna is modified to increase the gain, the omnidirectional pattern is squashed in a vertical plane and is enhanced in a horizontal plane. This expands the signal’s coverage. A high gain antenna will therefore give increased coverage on flat terrain but the elevation will be limited making it unsuitable in mountainous regions.