A radio antenna is a useful electrical device that generates radio waves from electric power and also turns radio waves into electric power. It is a necessary item for listening to the radio with your radio receiver or transmitter. Antennas have a wide range of applications and you should know their features to choose the right one for your device.
Radio Antenna Direction
Antennas are versatile and receive radio waves equally from all horizontal directions. Such antennas are omnidirectional. However, many radio antennas have one or more preferential directions and these are high gain or directional antennas. High gain antennas can include additional surfaces or elements, such as parabolic reflectors or horns and parasitic elements, that direct the waves into the desired radiation pattern. You need to consider your radio and antenna needs before choosing amongst these types of antennas to ensure you purchase the correct one.
Radio Antenna Frequency Efficiency
Most antennas radiate efficiently at a certain frequency. Antennas that radiate over very wide ranges of frequencies are not as efficient as those that specialise in certain ranges. For instance, the simple Hertzian dipole antenna is small, but quite inefficient. The half-wave dipole, on the other hand, has high efficiency when the signal wavelength is double the electrical length of the antenna. Be sure to consider the frequencies and efficiency of an antenna before making a purchase.
Radio Antenna Basic Models
Knowing the basic radio antenna models can help you purchase the right one. The dipole antenna is a simple antenna that includes two wires pointing in opposite directions and it also serves as a reference model for other antennas. The dipole is omnidirectional when perpendicular to the antenna axis. The Yagi-Uda antenna is a directional dipole with parasitic elements that increase functionality. The random wire antenna is a very long wire with one end on the radio and another in free space in any way convenient. This antenna also requires an antenna tuner. The horn antenna is for high gain purposes and it requires lots of space. Horns are suitable for all frequencies, but tend to be impractical for lower frequencies. The parabolic antenna is best for high gain applications, such as satellite dishes. The patch antenna is a square conductor over a ground plane.
Radio Antenna Characteristics
Depending on your requirements for the radio antenna and its application, you need to consider an array of characteristics. The main performance specifications are the directions and the resulting gain. You could also focus on the impedance, bandwidth, current and voltage distribution, field regions, aperture, and efficiency.