End-fed λ/4 antennas, such as the ground plane, require low-loss RF ground systems in order to perform efficiently. Center-fed λ/2 antennas, such as the dipole, do not. However, good grounding is advisable for any antenna system in order to minimize interference and electrical hazards.
Electrical versus RF Ground
At A, the correct method for grounding multiple units. At B, an incorrect method creates RF ground loops.
Electrical grounding is important for personal safety. It can help protect equipment from damage if lightning strikes in the vicinity. It also minimizes the risk of electromagnetic interference (EMI) to and from radio equipment. In a three-wire electrical system, the ground prong on the plug should never be defeated, because such modification can result in dangerous voltages appearing on exposed metal surfaces.
A good RF ground system can help minimize EMI, even if it is not necessary for efficient antenna operation. Above figure shows a proper RF ground scheme (A) and an improper one (B). In a good RF ground system, each device is connected to a common ground bus, which in turn runs to the earth ground through a single conductor. This conductor should be as short as possible. A poor ground system contains ground loops that can act like loop antennas and increase the risk of EMI.
Radials and the Counterpoise
With a surface-mounted vertical antenna, there should be as many radials as possible, and they should be as long as possible. They can lie on the surface or be buried a few inches underground. The greater the number of radials of a given length, the better the antenna will work. Also, the longer the radials for a given number, the better. The radials should all converge toward, and be connected to, a ground rod at the feed point.
A counterpoise is a means of obtaining an RF ground or ground plane without a direct earthground connection. A grid of wires, a screen, or a metal sheet is placed above the surface and oriented horizontally, to provide capacitive coupling to the earth. This minimizes RF ground loss. Ideally, the radius of a counterpoise should be at least λ/4 at the lowest operating frequency.