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Case Studies

Channel Tunnel Rail Link and London St Pancras Communication Antennas

Chelton has designed and manufactured antennas for Thales, for their use on Section 2 of the Channel Tunnel Rail Link (CTRL) project, between Fawkham Junction in Kent and London St Pancras International station. This section includes the provision of 65 km of new high-speed track, enabling speeds of up to 186 mph (300 km/hr); also, bridges and structures along the route, and the construction of the three developments at St Pancras, Stratford and Ebbsfleet stations.

Thales was commissioned for several key tasks relating to communications within the CTRL. These included the provision of improved GSM-R and Cab Secure Radio (CSR) coverage for the railway operators, to maximise safety, and that of coverage for the London Fire Brigade in the evacuation shafts from the CTRL tunnels and from the passenger exit shafts.

After evaluating suppliers, Thales appointed Chelton to design and manufacture a range of single- and multi-band antennas. From our previous associations, Thales was confident that we would provide exactly what was required, knowing that our antenna design, engineering, manufacturing and performance testing would support the needs of their customer.

The prestigious but demanding CTRL civil engineering project presented unique challenges for wireless communications, with 25% of the new route running within tunnels, and with trains travelling through at speeds of up to 150 mph. 

An environmental feature of this application was the wind speed caused by trains in tunnels and resultant vibration that would have to be absorbed. Antennas therefore had to be impervious to their surroundings, be tough, reliable, have low wind loading, and meet the RF requirements to an uncompromising specification. Antennas for installation within St Pancras International needed to be discreet in appearance, allowing them to merge into the background of the magnificent new station.

We designed eight antennas to meet these requirements, all of which had specific power levels, and that covered the frequencies for GSM-R, Cab Secure Radio and the London Fire Brigade services.

One of the development projects we undertook was that of a slim panel antenna that was designed to support the emergency services system in the London tunnels, along with the associated emergency evacuation routes. Mounted inside a firewall of an evacuation tunnel, this antenna features long length insulated cable so that the radio can be mounted at a safe distance, helping to ensure its continued use during an emergency. 

Chelton's design solution produced an antenna that maintained 8.4 dBi gain and provided full coverage down the shaft.


Thales is a leading international electronics and systems group, addressing defence, aerospace and security markets worldwide.