Antennas for radio modems

Both omnidirectional and directional antennas are commonly used in radio modems. Omnidirectional antennas include fiberglass antennas, vehicle mounted antennas, and rod antennas.

Omnidirectional antennas are designed to transmit and receive radio signals in all directions. Most radio modems in master station adopt omnidirectional antennas because slave stations may be in any directions. Fiberglass antennas are often prefered in master stations and fixed slave stations. Vehicle antennas are commonly be mounted on top of vehicles to facilitate communication while the vehicle is in motion.

Directional antennas focus the radio signal in a specific direction, providing better signal strength and range in that direction. Directional antennas often achieve better communication performance at remote fixed slave stations.

Gain is an important parameter of an antenna. The higher the gain, the farther the communication distance, and the larger the volume.