125W Antenna Tuning Unit

ATU500SR 125W

Vector Series Antenna Tuning Unit

Since introducing the world’s first totally solid-state, high power radio beacon in 1970, Nautel has supplied the highest quality and reliability in non-directional radio beacons.

The most recent Vector Series Transmitters and Antenna Tuning Units continue this heritage and provide a dramatic improvement in system coverage.

Note: ATU500SR is shown with optional sunshield.


The Nautel Vector System offers a unique, patented solution to maintain system coverage regardless of undesirable antenna effects such as salt build-up on antenna insulators and ground plane resistance changes.

Highlights include:

  • Automatic antenna capacitance tuning using dual astatically wound loading coils.
  • Standard adjustable series resistor optimizes the tradeoff between antenna efficiency and bandwidth.
  • Remote control and monitoring of the ATU to limit worker exposure to strong RF fields, in keeping with Safety Code 6 / IEEE C95.1-1999.
  • Compliant with the specifications and recommendations of ICAO Annex 10, Vol. 1, Part 1, Section 3.4.
  • Cabinet enclosure designed to meet IP66 standard.
Automatic Antenna Capacitance Tuning Using Dual Astatically Wound Loading Coils

The capacitive portion of the antenna impedance is automatically matched using dual astatically wound loading coils.

The dual astatic pair has a lower field than a single coil solution and this reduces eddy currents induced in the ATU enclosure.

Standard Adjustable Series Resistor Optimizes the Tradeoff Between Antenna Efficiency and Bandwidth

High ‘Q’ antenna systems, with narrow bandwidth, can cause undesirable sideband attenuation to the modulation frequency.

The optional internal series resistor bank allows for the insertion of resistance in series with the antenna to reduce the ‘Q’ of the antenna system and thereby increase the bandwidth of high ‘Q’ antenna systems.


Remote Control & Monitoring of the ATU to Limit Worker Exposure to Strong RF Fields

The ATU may also be controlled and monitored via the GUI to limit the operator’s exposure to the strong RF field of the antenna in keeping with Safety Code 6 / IEEE C95.1-1999.

Remote control and monitoring of the NDB transmitter and ATU is available via the optional VR-Link remote control and monitoring system.