High-frequency direction finder (HFDF) is a term used in the field of radio direction finding. It refers to a piece of equipment used to locate the source of a radio signal. While the term HFDF is commonly used, there are also several synonyms and related terms that can refer to the same type of equipment. These include radio direction finder, high-frequency radio direction finder, radio direction finding equipment, radio direction-finding system, and high-frequency locator. Regardless of the specific terminology used, the technology behind these devices remains the same, housing a variety of electronic components designed to detect and locate radio signals in real-time.