A radio communications system for the English Channel Tunnel

The authors describe the 2-way, 42-channel VHF radio communications system supporting the construction activities of the English Channel Tunnel. The system was designed to use radiating coaxial cable and bidirectional repeater line amplifiers as the principal signal distribution scheme. Attention is given to signal distribution, channelization, frequency reuse methods, signaling schemes, and the audio interconnection used in a system utilizing 42 channels of radio communication to support tunneling operations. Link performance calculations are presented including intermodulation and thermal noise considerations. For the designed maximum of 23 cascaded amplifiers the system carrier-to-intermodulation ratio was 24.8 dB. Actual measurements in the Service Tunnel agree with predictions.<
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