might contain notch filters to remove known, but unwanted, signals which could impairs the system's ability to process weaker signals. Some of these issues are covered in RF chain. See also Amateur radio direction finding Amplitude monopulse AN/FLR-9, a cold war US Air Force HF direction finding system. AN/FRD-10, a cold war US Navy HF direction finding system. Automatic direction finder (ADF) Acronyms and abbreviations in avionics Battle of the Beams Cardioid Compass Electric beacon Emergency locator beacon Emergency position-indicating radiobeacon station High-frequency direction finding Huff-Duff Geolocation Indoor positioning system Modern dead drop techniques MUSIC (algorithm) Phase interferometry Position fixing Radio determination Radio fix Radio location Radio navigation Real-time locating system Signals intelligence TDOA Traffic analysis VOR/DME Wullenweber References Bibliography Radio Direction Finding Applications Literature (RDF Products) Doppler Systems Application Notes (Doppler Systems) Automatic identification and data capture Radio-frequency identification Avionics Geopositioning American inventions Radio navigation Italian inventions Aircraft instruments Air navigation Navigational aids