Near Real Time Ionosphere Opening Channel Information for HF near Vertical Incidence Skywave Communication over Kupang Nusa Tenggara Timur Indonesia

Near Vertical Incidence Skywave (NVIS) is one of the High Frequency (HF) radio communication modes that could be used for many activities on any circumstances due to its advantages. However, to ensure a communication’s success the working frequency or carrier frequency selection should be taken considerately based on the ionosphere condition that varies over time. This paper explains the development of the opening channel information system based on ionosphere observation over Kupang district, Nusa Tenggara Timur by pulsed HF radar or Ionosonde. The system periodically generates information from one-day observation of the Ionosonde’s echo intensity data (Ionogram) which were appended and converted to an image object. Further, the image processing technique is performed to reveal the information of the usable HF frequency range. The Connected Component Labelling and the Contour Detection methods were implemented to automatically determine the usable frequency of both the lowest and the most frequency values from echo data. The range of the frequency that could be reflected by the ionosphere is provided as the boundary of a lower and upper carrier frequency that could be chosen in NVIS communication as called usable HF frequency. This frequency-range information then could be used as a reference for selecting the carrier frequency with a radius up to 300 km from the center point of ionosphere observation.