What is the difference between a counterpoise and radials?

In the antenna world, the terms “radials” and “counterpoise” are often used interchangeably because they both serve the exact same electrical purpose: providing a return path for RF currents in an unbalanced antenna. Just like a battery needs a negative terminal to complete a circuit, an unbalanced antenna (like a vertical or an end-fed half-wave) needs a “second half” to push against so it can radiate efficiently. The difference largely comes down to geometry and how they interact with the physical earth.

Radials: A Specific Configuration

“Radial” refers to a specific physical layout. Radials are wires that spread out symmetrically from the feedpoint, like the spokes of a wheel. They are almost always used with base-fed vertical antennas to create a ground plane. There are two main types of radials, and they behave very differently:

• Ground-Mounted (Buried or on the surface): Earth is lossy at HF frequencies. If you pump RF into a vertical without radials, a lot of your transmit power simply heats up the dirt. Ground radials provide a low-resistance path for the RF to return to the feedpoint rather than getting absorbed by the soil. Because they are coupled to the earth, they are non-resonant. Having many shorter radials (e.g., 30 to 60 wires) is vastly better than having a few quarter-wave radials.
• Elevated Radials: If you raise the base of your vertical a few feet in the air, the radials are decoupled from the earth. They act as a true, isolated artificial ground plane. Because they are in the air, they are resonant and must be cut to exactly ¼ wavelength for the band you are using. You usually only need 2 to 4 of these per band.

Counterpoise: The Broader Concept

A counterpoise is any conductive mass used to substitute for an earth ground. Technically, a radial system is a type of counterpoise. But in everyday ham parlance, “counterpoise” usually implies a minimal, non-symmetrical solution used when a full radial field isn’t possible.

If you throw a single wire on the ground beneath an End-Fed Half-Wave (EFHW) or an inverted-L, you are using a counterpoise.

• Geometry doesn’t matter: A counterpoise can be a single wire dropping off a balcony, a chain-link fence, the metal roof of a shed, or even the shield of your coaxial cable (though using the coax often leads to nasty common-mode current in your shack).
• Capacitive Coupling: An elevated counterpoise acts like one plate of a large capacitor, with the actual earth acting as the other plate. It creates a virtual ground point.
• Tuning: For high-impedance antennas like an EFHW, a short, untuned counterpoise wire (often 0.05λ) is usually enough to balance the system.

At a Glance

Feature	Radials	Counterpoise
What it is	A specific geometric layout (spokes on a wheel).	The broader electrical concept (the “other half” of the antenna).
Typical Use	Quarter-wave verticals, ground planes.	End-fed antennas (EFHW, random wires), elevated setups.
Symmetry	Symmetrical to create an even radiation pattern.	Often asymmetrical (e.g., a single wire).
Earth Connection	Often laid on/in the earth to mitigate soil losses.	Often isolated from the earth to provide a virtual ground.

Ultimately, if you lay out 60 wires in a circle under your vertical, you’ve built a radial system. If you attach a single 15-foot wire to the ground lug of a 9:1 unun, you’re using a counterpoise.