In addition to antenna frequency, consider the following criteria when selecting an antenna.
There are antennas that can be used for indoor application or outdoor application. One important aspect of an antenna is whether it is weather sealed to protect it from environmental damages.
| Differences | Indoor antenna | Outdoor antenna |
|---|---|---|
| Use | Can only be used in indoor installations. Indoor antennas must not be used for outdoor installations. | Used for indoor as well as outdoor installations. During indoor installations, outdoor antennas can be used in freezers and coolers to handle harsh temperatures. |
| Connector type | RP-SMA plug | N-plug connector |
| Lightning protection | Not required | Required. But, lightning protection is not required when the antenna is installed in indoor locations. |
| Antenna pattern | Description |
|---|---|
| Omni-Directional | Signal radiates from the antenna in all directions on the horizontal plane. |
| Directional | Signal radiates in a specific direction, typically described as a beam of given width, expressed in degrees in the horizontal and vertical plane. |
| Antenna type | Description |
|---|---|
| Panel | A panel antenna is a flat antenna mounted to a wall or other vertical surface and radiates RF energy (radio waves) directionally away from the wall. They usually have gain greater than 5 dBi and are not suitable for omni-directional situations. Ideally suited for long hallways. |
| Patch | A patch antenna is a flat antenna mounted on the ceiling but whose pattern is omni-directional. Most of the energy goes out horizontally to the sides of the antenna and equal in all directions. |
| Dipole | A dipole antenna is a tubular antenna that can be either a pipe shape, a straight flexible rod or a paddle. This antenna has an omni-directional pattern when placed in a vertical position. It usually has 2 dBi of gain. |
| Dipole array | Essentially a dipole, a dipole array is two or more dipoles that are placed one on top of the other, requiring a longer tube to hold them. The advantage of a dipole array is that it has higher gain. |
| Parabolic grid | A parabolic grid antenna is a very directional, dish-like antenna. Its parabolic reflector focuses the RF energy like a flashlight. Most of the time the radiating element is a dipole, but when combined with the dish, it becomes very directional with gain up to 24 dBi. Usually used in long point-to-point systems. |
| Yagi | A yagi antenna is a antenna that has an internal structure resembling that of typical antennas used for TV reception (a series of rods perpendicular to a main rod, making a triangular shape). This is a directional antenna with less gain than the PGA, typically around 13 dBi. It can be used in either point-to- point situations, or to cover a very long, narrow area in point-to-multi-point situations. |
| Polarized panel | A polarized panel antenna is a multi-port panel antenna with different linear polarization alignments on the different ports. Common polarization alignment orientations are Vertical/Horizontal and Vertical/ 45°-Slant. Polarized panel antennas are useful on outdoor Line-of-Sight links, and are also used in indoor deployments for improved coverage uniformity at the expense of slightly reduced range. |
| Antenna characteristics | Description |
|---|---|
| Frequency | The frequency band within which the antenna performs at the stated specifications. |
| Gain (dBi) | The relative amplification of the antenna with respect to an equivalent isotropic antenna, expressed on the decibel logarithmic scale. |
| Cable loss (dBi) | The signal strength loss introduced by the cable connected to the antenna expressed on the decibel logarithmic scale. |
| Net gain (dBi) | The resulting amplification of the antenna paired with its cable. |
| Polarization | The orientation of the electrical field which the antenna is optimized to receive. If the transmitting and receiving antennas are both linear polarized, then turning one 90° so that they are cross polarized will reduce the range significantly. |
| Voltage Standing Wave Ratio (VSWR) | Voltage Standing Wave Ratio (VSWR) is the ratio of maximum voltage to minimum voltage along the line. Expresses the degree of match between the transmission line and the terminating element (antenna). When VSWR is 1:1 the match is perfect, a VSWR of 1.5:1 corresponds to 96% power efficiency. |
| Azimuth 3dB beamwidth | Width of the antenna beam on the horizontal plane expressed in degrees. |
| Elevation 3dB beamwidth | Height of the antenna beam on the vertical plane expressed in degrees. |