Feasibility study of data transmission via HF link from a small UAV platform

Abstract: The High Frequency (HF) band, 3-30 MHz, is used when no infrastructure for long-range communications is available. New technology, such as digital signal processing enables higher data rate in the HF band, which in 2000s has resulted in increased commercial use. Reflection of radio waves in the ionosphere allows for beyond horizon communication, and are a unique property of the HF band. However, properties of the ionosphere are highly dependent of radiation from the sun, which varies with geographical location, season and time. The use of unmanned areal vehicle (UAV) has increased during the past years. In this project it is investigated if a HF transmitter can be placed on a small UAV platform. The objective is to get an estimation of the probabilities for successful HF transfer of real-time data from a small UAV. For example, the data could be sensor- or position data. When studying a complex problem having several parameters, such as a HF communication system, it is necessary to use the systems approach. This report illustrates the impact of size of the transmitting antenna, transmitter output power and bandwidth as well as different sources of noise and its levels. The results and analysis, made in this project, shows that there are feasible solutions for every tested case except at very high latitudes. Frequency planning, that is finding the less occupied channel, is almost as important as maximizing the signal to noise ratio. This project has been carried out on behalf of ÅF Technology in Solna, Sweden.