Twin-Lead Radiator: Canam’s twin-lead open line radiator with low loss Delrin spacers provides an efficient FM signal in the tunnel. The radiation level inside the tunnel can be controlled by the mismatch of the terminations at the end of the transmission line. The open wire system has excellent longitudinal attenuation for FM frequencies and is a very efficient and cost effective particularly when the AM return wire is accommodated onto the Twin Lead.

The wire used for the twin-lead will vary depending if it is driven from one end or center fed. Wires are mounted on to standoffs using the Canam Technology Inc. EC-3 Delrin spacers.

The standoffs are typically spaced every 20-ft. inside the traffic area and 25 ft. in airducts. See the twin-lead radiator application note for installation details and options.

Canam’s Twin-lead TAS could be used for the following reasons:

Lower cost of materials:

• Twin lead uses #8 wire electrical wire
• Radiating cables are custom products requiring fasteners and connectors sold only through that cable manufacturer

Lower cost of installation:

• Twin lead stand-offs are every 20-feet
• Radiating cable requires standoffs every 5-feet

Lower cost of maintenance:

• #8 wire is inexpensive, readily available and easy to repair
• Radiating cable is expensive particularly for small orders; simple repairs can require specialized connectors that have to be special ordered and special training to repair a cable.

The following drawing depicts the typical Twin-lead Antenna structure that could be extended with adequate coverage for over a mile (5000+ feet):

Advantages of Canam’s Twin Lead Tunnel Antenna System

The Twin-lead Tunnel Antenna system is the most efficient and cost effective method for rebroadcast of the FM signal in an enclosed environment. The Twin-lead Tunnel Antenna System incorporates specially designed baluns, terminations and low-loss Antenna Spacers. 90% of the system components are readily accessible components, which can be purchased separately from local vendors. For example, the Cable Fasteners use standard cable ties and the Twin-lead Tunnel Antenna Cable is standard #8 electrical wire. The ability to buy system components locally is a huge advantage over radiating cable designs, which use proprietary components exclusively.

The Twin-lead Tunnel Antenna has a broad bandwidth enough to cover the FM/VHF bands as well as very good performance for UHF systems. Besides, it can be used as AM Radiator Wire in applications where separate tunnel radiators for AM and FM are not suitable. RF characteristics of twin-lead lines are very well understood and have been successfully installed and tested in short and long tunnels.