A Spots Independent for NVIS Channels Observation

The Ionosphere layer is used as a reflective mirror of the HF radio communications system. They have dynamic characteristics that are constantly changing at any time and place. It is need a reliable prediction system to be able to estimate the condition of the ionosphere. The term "forecast" is adopted for the practical schemes which are based on solar-terrestrial relations. In the case of zero lead-time, the forecast becomes a real-time probing of ionosphere, or well known as Real Time Channel Evaluation (RTCE) for HF communication. The term "now-casting" also used to describe an observation-intensive approach at very short term (up to one hour) ionopheric forecasting. Since the era of the 2000s the HF radio has advanced to be an intelligent HF radio system that is able to adapt to the condition of propagation at any time in order to maintain the quality of communication performance. The main component of the intelligent HF radio implementation is a low-power sounding/beacon system to probe the propagation conditions of each available HF channel. Implementation of sounding /beacon technology with small signal was of course still very secret, since then a group of scientists Amateur Radio member introduce/unlock this beacon/ sounding technology, which then called WSPR. With this openness of WSPR technology, we will replicate and integrate this small signal beacon/sounding technology in an intelligent HF communications system that is expected to be of immediate benefit to open communications in mountain-covered areas, in NVIS mode, or directly build HF radio networks throughout Indonesia in the sky wave mode, to respond to disaster mitigation. In this study we tried to carry out a simple probing/sounding technique by using WSPR. We concluded that the SNR of observations values are comparable with those of VOACAP simulation software Furthermore, we found that there is no difference observations results between two receivers located more than 100 Km away. We also concluded that both receivers only received sky wave signals.