Tunnel Portal Equipment

[BestWestern]

Hi All,

Can anybody come up with a definitive purpose for the aerial-like equipment which often hangs from the top of tunnel portals, or sometimes within the tunnel bore itself? These things are generally on a mounting bracket bolted just above the centre of the portal arch, with the device itself pointing back into the tunnel; or are fitted inside the tunnel bolted to the ceiling. My best guess would be NRN repeaters, does anybody else know better?!

 

[RPM]

You certainly see antenna for Cab Secure Radio on tunnel mouths. I've not seen one for NRN but they may occur. Presumably GSM-R antenna are being added to tunnels at the moment. Sorry that's a bit vauge, but I'm usually passing tunnel portals too fast to study them in detail!