The services are based on HF radio utilizing the normal HF radio on board the aircraft.

Our main monitored frequencies are allocated by ICAO in frequency bands exclusively intended for Airline Operational Control traffic. In addition to these published frequencies we have a number of other frequencies that can be used as discrete frequencies for Phone Patches.

The characteristics of HF radio propagation give a very large area of coverage as a result of the reflection of the radio waves in the ionosphere as opposed to VHF, which only gives line-of-sight coverage to the horizon.

Our equipment is solely based within Sweden with our main receiver site at Enköping some 100 km west of Stockholm where we have both channel and variable receivers.

The transmitter site is located at Karlsborg, some 300 km southwest of Stockholm. This site houses a number of powerful transmitters with both omni-directional as well as directional antennas.

These sites are connected via leased lines to our Consoles at our Operation Center at Nacka Strand a few km east of the central parts of Stockholm.