Hourly NAP Charts
Real time NAP charts are limited in area to the SWS real time Australia/NZ foF2 map area of coverage. Perth IN01 and Port Hedland INO1 HAP charts (which the Perth-PortHedland NAP is based) extend outside this range (to 70 degrees East). The 70 degrees east charts are based on the SWS World foF2 map. For this reason there are two NAP charts for the Perth Port Hedland INO1 NAPs, one using the Australian real time foF2 map, the other the world real time foF2 map.
The Darwin site can sometimes be affected by interference so alternative NAPs are available for domestic HF communications without the Darwin site.