What is a counterpoise in an antenna system?

What is a counterpoise in an antenna system?

• A. A conductor or system of conductors used as a substitute for ground; can also be used as a ground reflector (NVIS)
• B. A protective shield around the feedline
• C. A type of coaxial cable used for isolation
• D. An insulating material around the antenna base

Answer: (A)

A counterpoise provides the RF return path when the actual earth ground isn’t a reliable or adequate reference for the antenna. It is a conducting surface or network placed at or near the feedpoint that acts as the artificial ground plane for the antenna system. With a counterpoise, the current has a proper path to return, which stabilizes impedance and improves radiation efficiency. It can be a single conductor or a set of radials laid out around the base, and in some setups it also serves as a ground reflector to shape the pattern for NVIS, boosting short-range, earth-to-sky propagation. It isn’t shielding around the feedline, a special coax, or insulating material—those don’t provide the necessary RF return or ground plane.

A counterpoise provides the RF return path when the actual earth ground isn’t a reliable or adequate reference for the antenna. It is a conducting surface or network placed at or near the feedpoint that acts as the artificial ground plane for the antenna system. With a counterpoise, the current has a proper path to return, which stabilizes impedance and improves radiation efficiency. It can be a single conductor or a set of radials laid out around the base, and in some setups it also serves as a ground reflector to shape the pattern for NVIS, boosting short-range, earth-to-sky propagation. It isn’t shielding around the feedline, a special coax, or insulating material—those don’t provide the necessary RF return or ground plane.