CL-40 Antenna


Self-supporting, Capacitive Top-loaded Antenna

The CL-40 antenna is designed to provide a complete antenna-tuning-matching package when supplied with a Nautel Automatic Antenna Unit to interface directly at a 50 ohm unbalanced level with low/medium power transmitters in the LF and MF bands.

It is particularly suitable for radiobeacon installations normally fitted with a whip where low profile and better efficiency and bandwidth are important.


Highlights include:

  • Increased efficiency.
  • Small footprint.
  • Ease of installation and maintenance.
  • Suitable for Marine Coastal Stations.
  • Ground Plane.
Increased Efficiency

The effective radiated power from an electrically short LF/MF antenna is proportional to the square of the antenna’s effective height. The values of HE for a conventional, base fed, vertical radiator without capacitive top loading elements such as a whip antenna is 0.5. The CL-40 design includes a capacitive top loading element structure and a loading coil at the mid point of the antenna height which contains approximately 90% of the inductance required to series resonate the antenna capacity. These two elements increase the effective height (He) of the CL-40 to approximately 75% of its physical height of 40 feet (12.2 m). The capacitive top loading element structure offers the additional benefit of improved antenna system bandwidth.

Small Footprint

The antenna is a self-supporting antenna, with no guys, and is ideally suited for locations where space is at a premium.

Ease of Installation and Maintenance

The lightweight construction of the CL-40 which includes a winch for raising and lowering the antenna provides for easy installation, inspection and maintenance requirements. The antenna can be raised and lowered once assembled via the included winch in a few minutes.

Suitable for Marine Coastal Stations

The CL-40 is supplied with components including stainless steel cable and wire which are suited for the marine environment found at coastal stations around the world.

Ground Plane

A suitable ground plane configuration, based on site conditions and required antenna system performance will be recommended by Nautel.