DroidProp is professional HF propagation prediction software for 3 to 30 MHz, powered by VOACAP (Voice of America Coverage Analysis Program). This app is mainly intended for ham radio operators and SWLs (shortwave listeners).All calculations are done in the device. No Internet connection is required, except for automatic updates of the sunspot numbers at regular intervals.Due to the usage of a full fledged VOACAP-installation, the app has to be installed in the phone-internal memory (APP2SD is not possible). This is due to technical restrictions. It requires about 9 MB (after installation) flash storage plus approx. 120 kB / predictionPermissions:INTERNET: Required to download current SSN dataEXTERNAL STORAGE: Required for VOACAP runtime filesLOCATION: Required to use current position for a site