Omnidirectional antennas are a large category of antennas, which we briefly outlined in the previous comparison with directional antennas. In this issue, we will provide an in-depth analysis of omnidirectional antennas, from selection to use, what are their characteristics?
An omnidirectional antenna is an antenna that radiates or receives radio signals uniformly in all horizontal directions. It has a non-directional radiation pattern in the horizontal plane, which means that it does not focus energy in a specific direction like a directional antenna. Omnidirectional antennas are commonly used in amateur radios for local and regional communications, mobile and portable operations, and where communication with stations in all directions is required.
There are several types of omnidirectional antennas, with vertical, monopolar, and terrestrial antennas being the most common. Each type has a unique design, but they all function by evenly distributing radiant energy in a horizontal plane.
1. Dipole antenna
A dipole antenna has two conductive elements, such as a metal wire or rod, which are arranged in a straight line, and in the center of the dipole antenna, the conductive material is separated by an insulator. The RF voltage source is set in the center of the antenna. The voltage and current passing through these two conductive elements then generate electromagnetic or radio signals that radiate from the antenna in all directions.
2. Unipolar antenna
A monopole antenna is a straight rod-like conductor mounted vertically above the floor plan. It is half the size of a dipole antenna. Conductive rods work like resonators, radiating the input signal in all directions above the ground plane perpendicular to the length of the antenna.
3. Collinear antenna
A collinear antenna is a half-wave dipole antenna with multiple dipoles stacked vertically on top of each other, increasing the gain of the antenna in the vertical direction.
4. Whip antenna
A whip antenna is a flexible metal wire or rod. They are mainly used in portable radios, walkie-talkies, car antennas, etc.
5. Ground plane antenna
Ground plane antennas use a conductive ground plane mounted on the ground to improve the performance of the antenna.
To use an omnidirectional antenna efficiently, you also need to follow the general rules of antennas, which we will briefly list here.
1. Select the appropriate antenna type according to the operational requirements, such as frequency range, available space and required radiation pattern.
2. Install the antenna on a suitable support structure or mast, ensuring that it is properly grounded and oriented towards the desired polarization (horizontal or vertical).
3. Connect the antenna to the transceiver using a suitable feeder and an antenna tuner if necessary to match the impedance.
4. Monitor the received signal strength or SWR to ensure that the antenna is working properly. Transmit and receive signals, using an omnidirectional radiation pattern to communicate with stations in all directions.
The advantages and disadvantages of omnidirectional antennas are also very clear, and can be clearly understood in terms of installation, performance and use.
Omnidirectional antennas, like directional antennas, have begun to take shape and can be seen in all kinds of wireless connection fields.