External links List of North American navigation aids from airnav.com A list of navigation aids with entries missing from the above UK Navaids Gallery with detailed Technical Descriptions of their operation Flash-based ADF instrument simulator Large selection of beacon related resources at the NDB List Website The NDB List Radiobeacon Photo Gallery On The art of NDB DXing [archived] Database with NDBs Automatic Direction Finder Aeronautical navigation systems Radio navigation Beacons