Sensofusion AIRFENCE Sensor

The AIRFENCE Sensor from Sensofusion (Finland) is a passive RF sensor for drone detection that monitors 70 MHz to 6 GHz and can be networked to cover larger areas. It is mounted on buildings or vehicles and can therefore be used stationary or vehicle-mounted. The sensor itself weighs 5 kg, the complete case about 25 kg.

The manufacturer gives up to 10 km of range with a single sensor unit. That is a value under favourable conditions: the range of a passive sensor depends on the drone’s transmit power, line of sight and radio environment, and it drops in a city. The receive range of 70 MHz to 6 GHz takes in the control links at 868 and 915 MHz, the connections at 2.4 and 5.8 GHz and lower frequencies on which unusual links may sit. Remote ID broadcasts in the 2.4 GHz band also lie within range; whether they are evaluated depends on the software.

The sensor only receives and does not interfere with the drone’s radio link. Whether and how receiving and evaluating third-party radio signals is permitted (secrecy of telecommunications, data protection) has to be clarified for Germany and Poland before use. If a sensor network is used to locate signal sources, that additionally touches data protection. Jammers may be operated only by authorities in Germany and Poland (Section 91 TKG, Article 42 of the Polish Electronic Communications Law).

In selection it counts where the sensor is mounted: on a building it gains height and line of sight, on a vehicle mobility, but it loses steady alignment. The case of about 25 kg has to be allowed for in transport and set-up. For a position rather than a presence alert, several networked sensors are needed. The signature library needs upkeep; antennas, cables, connectors and weather protection need checking. Drones that do not transmit, such as autonomous or fibre-optic controlled ones, stay invisible.