Beyond the line of sight HF communications propagate via the ionosphere. Many different modes of propagation may be supported and each may arrive at different time delays, and may be subjected to Doppler shift and spread due to bulk motion and turbulence in the ionosphere.

All of these parameters, and the received signal-to-noise ratio (SNR), can have an effect on HF communications systems. By measuring the HF channel, we provide data to facilitate HF simulator and modem development, with the goal of developing communications systems that are more reliable and can use increased data rates.

The Doppler and Multipath SOunding Network (DAMSON) is an ongoing collaboration between QinetiQ, the Canadian Communications Research Centre, the Norwegian Defence Research Establishment and the Swedish Defence Research Agency. The Wideband HF Ionospheric Sounder for Propagation Environment Research (WHISPER) is a recent development based on a prototype software radio, and allows sounding of HF channels up to 80 kHz bandwidth.