GPS (Global Positioning System) systems work by receiving signals from satellites. This is not possible without an antenna. While most GPS units, including phones and portable navigation units, have built-in hidden antennas, some offer the option of adding an external antenna. While it is usually not necessary to install an external GPS antenna, there are cases where it can help.

Whether installed in a phone or in the back of a vehicle, there are two types of GPS antennas: passive and active. Passive antennas passively receive GPS signals and transmit those signals to a GPS navigation device. Active units contain an amplifier that allows the antenna to receive signals from greater distances. Amplified antennas nearly double the signal reception range of a GPS device.

Active antennas are generally more expensive and difficult to install than passive antennas. However, these antennas can be installed further away from a GPS tracker. For this reason, they are better suited for large vehicles or situations where a signal must be maintained.

GPS devices work by receiving signals from a network of satellites. By taking into account the direction and signal strength of satellites in the network, a GPS device can determine its physical position on Earth accurately, usually as a dot on a digital map.