For many of us, the nearest we get to a satellite earth station is when the Sky installer bolts a dish to the roof of the house. This is usually a simple process involving a ladder, a drill and 30 minutes. A gateway earth station – a large dish used to send and receive huge bandwidth TV and internet signals – involves a different scale of planning and installation.
Figure 1: 9.2m antenna (Picture taken from www.cpii.com)
Planning and building a gateway Earth Station is a complex project. The steps are similar, whether the antenna is located in Stevenage or Stockholm, although weather conditions and access to power sometimes affect the design. For the purposes of this example, the key elements for a typical 9.2m antenna earth station located in the United Kingdom and with an existing Data centre on site will be covered.
An earth station comprises of four sub-systems: Foundation, power, antenna and racking. Figure 2 summarises the key stages and approximate timescales in the gateway procurement:
Figure 2: Timeline for the key subsystems of an earth station procurement
Just like building a house, the installation begins with a foundation that will carry the physical load. The antenna location survey is critical and can take up to two months. The key elements to consider are the soil structure, road access to site for crane and large lorries, site security, planning permission for high structure, and a radio frequency interference (RFI) survey for potential obstacle and potential interferer. Due to cable losses, Radio Frequency (RF) equipment cannot be located more than 50m from the antenna subsystem, which means that additional shelter may be required if the datacentre hosting the network equipment does not meet this requirement.
From the start of mobilising the site, some activities can be run in parallel. The main modules are the civil work for the antenna foundation, which can take up to three months, and the power installation can take up to four months if the site is located close to a power grid.
On completion of the antenna pad foundation, the antenna building work can start. It usually involves a team of three staff working throughout the entire construction and specialists coming along to perform specific tasks on the antenna, taking around two months.
Once built, the various elements must work together as a functional system. Figure 3 shows the high-level interfaces between the main subsystems:
Figure 3: Interfaces between high level subsystem of a Gateway
On completion of the mechanical structure of the antenna, the final stage is the antenna testing, which can take around one month. This verifies the antenna performance and ensures that all equipment is calibrated and functioning as expected. Servo motors align the antenna, which must be highly accurate to ensure reliable connection to the satellite and performance – small errors can lead to poor signals and high interference. Antenna radiation patterns are measured using known satellites sources, in order to verify the antenna gain performance and Effective Isotropic Radiated Power (EIRP). The quality of the signal is assessed for EIRP (power) and frequency stability. Finally, the Ground Control Equipment (GCE) subsystem is verified to ensure the elements of the earth station can be monitored and controlled from a central point.
Once the antenna is handed over by the contractor, the operator usually proceeds with internal RF end-to-end testing with the satellite which can take couple of weeks before being fully operational.
Each project is unique, and the local conditions need to be adapted to as well as the country’s regulations which can impact the overall timescale of the project. The antenna build usually has a fixed timeline and takes into account potential delays including planning permission authorisation, site survey results which can require change of design for the foundation or contractor delays. Finally, the new earth station will require local license to operate.
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