5 Things to Consider when Choosing an Antenna
By Jerry Posluszny
November 3, 2020
What should you consider when choosing an antenna? From low profile mobile antennas that are designed for fleet management and smart highway systems to Omni-Directional base station antennas that are designed for cellular infrastructure and FirstNet rollouts, the right antenna is critical. But how do you know which antenna best fits your needs? Here are five things to consider when choosing an antenna and how Mobile Mark Antenna Solutions can help.
- Antenna Frequency: The bandwidth and frequency range of an antenna are related terms. The bandwidth of an antenna refers to the range of frequencies over which the antenna satisfies a particular parameter specification. The parameters generally specified are gain, radiation pattern, the VSWR etc. Most commonly, the VSWR is chosen as the parameter for bandwidth considerations and this bandwidth is called the impedance bandwidth.
- VSWR Specification: The Voltage Standing Wave Ratio (VSWR) is an indication of the amount of mismatch between an antenna and the feed line connecting to it. The range of values for VSWR is from 1 to infinity. A VSWR value under 2 is considered suitable for most antenna applications. A VSWR specification commonly adopted is a 2:1 VSWR, which means that the range of frequencies over which the VSWR is less than 2 is chosen as the bandwidth of operation.
- Antenna Gain: The Gain of an antenna is related to its directivity. Directivity is a numerical indication of the ability of an antenna to focus energy in a particular direction rather than spreading energy out uniformly over a wide-angle range. The gain of an antenna is its directivity reduced by the loss introduced by the antenna. The parameter that characterizes the loss of the antenna is called the radiation efficiency which has a value between 0 and 1.
- Omni-directional or Directional: An antenna that radiates and receives energy equally well in all horizontal directions is an omnidirectional antenna. An antenna also has the ability to focus energy in a particular direction which means it’s directional. Omni-directional antennas are best suited for applications requiring good all-round coverage. For some applications, all-round coverage is either not required or it is desirable to be able to focus the available energy radiated by the antenna in a specific direction. This will dictate the choice of antenna.
- Placement: To ensure the most optimal antenna placement, line-of-sight, height & distance between antennas and the curvature of the earth are all critical factors that must be considered. Antennas must be mounted as high as possible due to the line-of-sight range restrictions with VHF signals. The orientation of your antennas should always match (vertical-to-vertical/horizontal-to-horizontal) or be as close to the same plane as the transmit
This is just to get you started, stay tuned for 5 more things you need to know when choosing the right antenna!