Mastering GPS Antenna Placement

Introduction

The location of your GPS antenna can have a big impact on the performance of your timing system. While many users focus heavily on hardware selection, the antenna installation location can make or break system reliability.

Critical Factors in Location Selection

Successful GPS timing implementations begin with selecting the location for your GPS antenna. The ideal position provides clear sky visibility. Ideally, the horizon should be visible in all directions. If nearby buildings make this impractical, try to position the antenna where it can see as much of the sky as possible.

You should also position the antenna away from potential sources of interference. Air conditioning units, radio transmitters, and high-voltage equipment all generate electromagnetic interference. This interference can negatively affect system performance. A thorough site survey before installation will help identify and avoid these potential problems.

Urban Environment Considerations

Building density creates additional challenges for installations in urban areas. The reflections and blockages caused by surrounding buildings (the urban canyon effect) can have a negative impact on timing accuracy. In these situations, we usually recommend installing multiple antennas. This provides consistent coverage as satellites move across the sky.

While mounting your antenna higher does typically improve urban canyon performance, this benefit needs to be weighed against increased cable length and installation complexity. In some cases, remote antenna units with remote GNSS decoders prove more effective than extremely long cable runs.

Cable Length and Signal Quality

The antenna cable plays an important role in the operation of your GPS timing system. Each additional metre of cable introduces signal loss and timing delays that need to be accounted for. While the cable delay can be compensated for in your GPS decoder, it is best to minimise cable length where possible.

For installations requiring cable lengths in excess of 50 metres, the installation of a remote GNSS decoder should be considered.

Lightning Protection Implementation

Due to their exposed position, rooftop GPS antennas need robust lightning protection. We recommend installing an inline surge protection device at the point where the antenna cable enters the building. The surge protection device must be grounded to a low impedance ground system and should be regularly inspected.

Maintaining Long-term Performance

We recommend you periodically inspect your antenna installation. Water ingress at cable connections, environmental changes and new construction can all affect the performance of your GPS timing antenna. A regular inspection schedule can help to ensure continued system reliability.

For detailed implementation guidance or site-specific recommendations, please contact our technical support team.