Listed below are requirements for selecting an optimal installation location for your GNSS antenna. For instructions on how to install a GPS/GNSS antenna, the signal cable, and accessories such as surge protectors, weatherproofing kits, or amplifiers, refer to the documentation that came with the respective equipment.
Regarding the selection of a suitable antenna location, the following recommendations generally apply:
- A clear view of the sky down to the horizon in all directions is recommended for the most optimal satellite reception. The mounting location of the external GNSS antenna should be free of objects that could obstruct satellite visibility from straight overhead to within 20 degrees of the horizon in all directions.
- GPS antennas need to be separated from surrounding metallic materials. Any metal in the area changes the shape of the reception pattern of the antenna. Any buildings or metallic materials close to the antenna can create shadows which can shield the antenna from receiving in that particular direction.
- Separation between multiple antennas: If the antennas are installed too close together there could potentially be interaction between the antennas and a resulting loss of sensitivity. This could also adversely affect the search pattern of the antennas, resulting in fewer satellites being tracked.
- Ideally, antennas should be separated as much as physically possible, so as to help isolate them from being simultaneously affected by the same anomaly (such as a nearby lightning strike or a falling object, for example). The minimum GNSS antenna-to-antenna distance is 39 inches (1 meter).
- GPS antennas are receive-only antennas which do not intentionally transmit any signals. Even though this reduces the amount of separation needed between multiple antennas, a few meters of separation are recommended to isolate the antennas from each other, in order to limit any possible EMI interference caused by the active components inside the antennas.
- If a noticeable decrease in sensitivity (resulting in weak signal strengths) and/or very few satellites being tracked is noted, try repositioning the antennas to improve the satellite reception.
To optimize timing accuracy, the GNSS receiver attempts to track satellites that are spread out as far as possible across the sky. The GNSS receiver must track at least four satellites in order to obtain time synchronization. Obstructions that block a significant portion of the sky result in degraded performance.
Mount the antenna at the desired location. Connect the supplied cable to the antenna. Take appropriate lightning precautions as necessary. The GNSS antenna must be mounted such that the antenna points to the sky, i.e. the connector side pointing down.
Note: Spectracom recommends applying an appropriate silicon grease to the cable connection at the GNSS antenna in order to protect the connection from moisture. An additional weatherproofing kit (P/N 221213) containing butyl rubber and plastic tape is also available from Andrews Corporation, USA, phone +1.800.255.1479.