Hourly HAP Chart

Hourly Area Prediction (HAP) charts are designed for communications between a specified base station location, and another station located within a nominated area.  The HAP chart is a guide to frequency selection for HF communications between a specified station and a base station, in this case Seattle.  The recommended frequency for communications with the base at a given hour is read off from the point in the map corresponding to the mobile's location.  The predictions are made from real time data which are updated each hour.  If present, dashed lines delineate areas of unlikely communication.  

Ionospheric Map

The plot above shows a near real-time critical ionospheric frequency (foF2) map produced using automatically scaled ionogram profiles from the Australian region and around the world.  The above map can be used as a guide to NVIS ionospheric frequency support and to generate real time HF predictions (eg Hourly HAP charts) to assist the HF radio communicator.  A feature of the ionosphere is its ability to reflect radio waves. However, only radio waves within a certain frequency range will be reflected and this range varies with a number of factors.  This graphic updates every 15 minutes.