Passive vs. Active GPS Antennas

The difference between passive, active, internal, and external antennas.

Person driving while using GPS
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GPS (Global Positioning System) systems work by receiving signals from satellites. That isn't possible without some kind of antenna. While most GPS units, including phones and portable navigation units, have hidden antennas built into them, some include the option of adding an external antenna. While it usually isn't necessary to install an external GPS antenna, there are cases where it can help.

Overall Findings

Passive GPS Antenna
  • Unpowered: Idly picks up GPS signals in the air to help locate a navigation device.

Active GPS Antenna
  • Powered: Amplifies antenna signal to greatly increase reception range of GPS device.

Passive vs. Active GPS Antennas

Whether installed in a phone or to the rear of a vehicle, there are two types of GPS antennas: passive and active. Passive antennas idly receive GPS signals and pass them on to a GPS navigation device, while active units include a powered amplifier that allows the antenna to pull signals from larger distances. Amplified antennas can nearly double the signal reception range of a GPS device.

Active antennas are typically more expensive and more difficult to install than passive antennas, but they can be installed further away from a GPS tracker. For this reason they are better suited for large vehicles or situations where it is critical that a signal is maintained.

GPS Reception Interference

GPS devices work by receiving signals from a network of satellites. By accounting for the direction and signal strength of satellites in the network, a GPS device is able to precisely locate its physical position on Earth, usually in the form of a dot on a digital map.

When an obstruction blocks a GPS device's view of the sky, it may be unable to identify satellite signals. This can result in either a failure to locate a device or degraded location accuracy. Tall buildings are a common source of signal degradation, as are the metal roofs of cars and trucks.

The risk of signal obstruction can be mitigated by placing a GPS device on or next to a vehicle window, but not always. Thicker roofs, for example, are more difficult for signals to penetrate than thinner ones, and tinted windows can have tiny metal particles that block GPS signals.

Who Needs a GPS Antenna?

Most GPS navigation devices come with internal antennas that work fine in the vast majority of cases. In some instances an external antenna is used to remotely feed information to the GPS device. This is mostly used when there is too much interference or an obstructed line of sight between the GPS unit and the sky. External antennas are also useful in lieu of older GPS units with dated internal antennas.

If you find that your GPS unit sometimes fails to obtain a signal, or if it seems inaccurate at times, then an external antenna may fix the problem. It’s cheaper and easier to try moving the unit around in your car first, since that may help alleviate obstruction and interference issues, but you may find that the only viable solution is to install an amplified external antenna.

If you’ve been using a GPS unit for a while, and you’ve never noticed any signal loss or accuracy issues, then you probably don't need an external antenna. If you find that your GPS unit often fails to obtain a signal, or if it seems inaccurate, then an external antenna may fix the problem. Another situation where an external antenna could help is if you're traveling off grid or into a remote region, where GPS reception is uncertain.