Which term is a ground-based radio transmitter that transmits energy in all directions?

• A. Nondirectional Radio Beacon
• B. NAV/COM
• C. NDB
• D. NM

Answer: (C)

A ground-based transmitter that radiates energy equally in all horizontal directions is a nondirectional beacon. This omnidirectional pattern provides a stable reference signal for aircraft navigation, allowing an ADF system to determine the bearing to the beacon regardless of where the aircraft is located around it. The beacon transmits on LF/MF bands and is identified to pilots so they can align their course to or from the beacon. The term used for this type of transmitter is nondirectional radio beacon, abbreviated NDB. The other options refer to different things: NAV/COM are onboard navigation and communication radios, and NM is a unit of distance, not a transmitter.