Short range HF radio channel measurements: Search for one path channels

Abstract

High frequency (HF) radio channel is diverse since it could be a single path channel or a multipath channel. However, there is lack of information about what is the ratio between these. Herein, results from a measurement campaign in Finland for ground wave and near vertical incidence skywave (NVIS) paths are reported. It was observed that one path channels are rather widely available and in ground waves they dominate. This means that channels for high modulation orders (high data rate HF) are available and should be searched for during the link establishment process. Unfortunately, the current link establishment processes do not support that such that maybe it is time for improvements. Another observation was that if channels are available at all, then usually there are multiple channels available. This means that recently introduced wideband (up to 24 kHz) and multiband (several 3 kHz bands) HF communications have room.