High frequency direction finder is a term used in radio communication to describe a device used for determining the direction from which a radio signal is coming. It is also known as HFDF and is used for military purposes such as locating enemy ships and submarines. Other synonyms for this term include radio direction finder, radio compass, and radio bearing indicator. The device works through the use of multiple antennas that are strategically positioned to receive signals from different directions. By analyzing the signals received, the direction of the source can be determined. This technology has played a significant role in military operations, search and rescue operations, and navigation for many years.