SANSA app calculates best HF communication channel

November 27th, 2019, Published in Articles: EngineerIT, Featured: EngineerIT

The South African National Space Agency (SANSA), based in Hermanus, has developed  a new application (app) that will assist users of the high frequency spectrum (3 – 30 MHz) to plan the frequencies that will provide the best and most reliable communication channel at any given time of the day or night between any two points or locations in between.

HF communications is dependent on the status of the ionosphere which in turn is affected by space weather and the 11-year solar cycle. The current solar cycle, cycle 24, is at its minimum with no visible sunspots on most days. During the first half of next year, solar scientists are predicting that cycle 25 will start and over the next five or six years build to its maximum and then slowly start reducing to a minimum by 2031 when cycle 26 will be in the wings. Solar activity is measured by the number of sunspots visible on the sun and used as a major factor in predicting which frequency will provide the best communication between two points.

SANSA operates the Space Weather Regional Warning Centre for Africa and keeps a close eye on space weather and issues warnings when solar flares occur. Solar outbursts may disrupt HF communication and if severe may cause damage to satellites and even electrical infrastructure on earth.

Solar scientists, after a recent review of data collected from satellites and other solar observations, predict that solar cycle 25 will the lowest in 200 years and only reach 60% of the sunspot numbers recorded during solar cycle 24.

The SANSA app, called “Ionospheric Characterisation Analysis and Prediction tool” (IOCAP) comes at the right time says its developer Piet van Zyl. “It will assist HF communication users, such as the SANDF and other government and civil agencies, to plan their communication channels.”

IOCAP is a very innovative tool that replaces older systems that were difficult to use and required specialists to get meaningful information and frequency predictions.

IOCAP includes a facility to consider the difference between the technical specification of radios and antennas used at either end. It is one thing to predict how well a high power fixed station at a headquarters in Cape Town will be received by a field station in, for example, the bush of  Mozambique, but it is another scenario of how well the field station operating on very low power and a small whip antenna will be heard in Cape Town. IOCAP considers both sides and calculates the best possible frequency at any given time to facilitate two-way communication. This is of upmost important in military and disaster relief communications.

HF communications is still widely used despite satellites which prove not always to be reliable. This was clearly shown during various disaster relief operations in the USA, India and Indonesia as well as more recently during the Mozambique Hurricane disaster when cellphone communication systems became overloaded and fell over and satellite phones did not operate due to the heavy cloud cover.

In civil aviation many long-distance carriers keep contact with their base using HF radio. IOCAP can be used to calculate which frequency at any given point during the flight will provide the best communication.

“We have designed IOCAP with the user in mind yet using more sophistication by using smart software algorithms to evaluate all the options which up to now were not possible. The tool also helps train new recruits on how to make sense of scientific theories behind frequency predictions, making it a valuable training tool”, Piet van Zyl said. “We have also included, what we called the ‘triangle of prediction’ which uses a colour displaying the quality of the prediction (as shown in Figure 1). If all three triangles are green there is a high reliability, two triangles green show a low to medium probability of communication and three red triangles, no communication possible.”

IOCAP has undergone extensive field trails and will be ready for release early in 2020

Contact SANSA,


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