Four hard places
Each has its own structure, its own standard and its own way of failing. All four are delivered the same way: designed, supplied, installed, commissioned, and measured against the specification before handover.
AM/FM rebroadcast with audio break-in
Broadcast radio carried through the bore so drivers keep the station they entered on, and an override that interrupts every carried service with a live announcement from the tunnel control room.
- SERVICES CARRIED
- AM, FM, DAB+
- FM HEADEND
- 87.5 – 108 MHz
- DAB HEADEND
- 174 – 230 MHz
Band-selective BDA coverage for underground rail
Radio coverage carried into running tunnels and onto platforms from a donor link to the serving base station site, amplified band-selectively so only the nominated services are re-radiated.
- DONOR LINK
- 698 – 890 MHz
- AMPLIFIER
- 800 – 890 MHz, band selective
- PLATFORM
- 806 – 870 MHz
Channelised repeater coverage underground
Two-way radio carried from a surface headend down the decline and shaft to the working levels, using a channelised repeater rather than additional base stations.
- HEADEND
- DSPbR, up to 8 channels
- BANDS
- VHF / UHF / 700 / 800 MHz
- CROSS BAND
- Supported
In-building distributed antenna system
Coverage taken from a rooftop donor link and distributed through the building on one riser, so below-grade floors and lift shafts are served as well as the floor plates.
- DONOR LINK
- 698 – 890 MHz
- AMPLIFIER
- 800 – 890 MHz, band selective
- RISER
- 7/8 in HELIAX
Distribution differs by place, and so does the coverage curve. The tunnel, rail and mine systems use radiating cable, where level declines with cable loss and is restored at each amplifier. The in-building system uses discrete ceiling antennas, where level peaks under each antenna and dips between them.