Counterpoise & Radials
The “other half” of vertical and end-fed antennas: what radials and counterpoises do, and how many you really need.
Half the antenna you can’t see
A dipole has two halves. A vertical or end-fed antenna only shows you one. The other half is the ground system, or counterpoise, and it carries just as much current. Without a good one, much of your power heats the dirt instead of radiating.
Ground-mounted radials
- Wires laid on or just under the ground, spreading out from the base of the vertical like spokes.
- Their length isn’t critical. More radials matter more than longer radials.
- A practical target is 16 radials or more; 32 or more gets most of the benefit. Even 4 to 8 is much better than none.
Elevated radials
- Raised a few feet off the ground, radials work much better, and just 2 to 4 are enough.
- Elevated radials should be about a quarter-wave long and cut to resonance, since they’re tuned like part of the antenna.
- Slope them down slightly to raise the feed impedance closer to 50 ohms.
Counterpoises for end-feds and mobiles
- An end-fed antenna still needs something to push against: a short counterpoise wire, the coax shield or the vehicle body.
- If the coax shield ends up as the counterpoise, RF can come back into the shack. A choke at the feedpoint and a deliberate counterpoise wire keep it under control.
- On a vehicle, the metal body is the counterpoise. Good bonding between the mount and the body makes a big difference.
Signs your ground system needs work
- SWR that changes when you touch the radio or the coax.
- RF “bite” on the microphone or the radio case.
- Signals well below what others report with similar antennas.
Try it: Counterpoise Visualizer
Change the settings below and watch the antenna respond. Start with no radials, then add a few, raise them, or switch on the choke.
Elevated radials sit at the height shown. At 0 they lie on the ground.
No counterpoise
Your settings
The radiator carries a standing wave: current is highest at the feed point and falls to zero at the top. Every bit of current that goes up the radiator has to come back from somewhere. Radials give it a planned path. Without them, it uses the outside of your coax.
Elevation pattern (side view)
Azimuth pattern (top view)
A vertical is omnidirectional: the same in every compass direction. Radials change how strong the circle is, not its shape. With no counterpoise the coax radiates too, which skews the pattern.
The counterpoise as a capacitor plate
1. Every antenna is two halves
A dipole has two legs. A vertical has one, so it needs something to push against. That’s the counterpoise: radials, a ground plane, a car roof, or, by accident, your coax.
2. A capacitor to earth
An elevated counterpoise and the earth form a capacitor, C = ε·A/d. RF current flows through that capacitance instead of through lossy soil, which is why a few elevated radials can work as well as dozens buried.
3. No counterpoise: RF in the shack
The braid has an inside and an outside surface. Your signal travels on the inside. The return current a vertical needs ends up on the outside, so the coax radiates, and RF follows it to your radio, mic and computer.
4. Radials plus a choke: clean shack
Radials give the return current its own path. A 1:1 choke at the feed point (ferrite beads or a coil of coax) blocks what’s left from flowing down the outside of the coax.
Rules of thumb
| Situation | What works |
|---|---|
| Radials on or in the ground | More is better, and length isn’t critical. 16 to 32 radials of λ/8 to λ/4 get you most of the benefit. Four is far better than none. |
| Elevated radials (above about 0.05 λ) | Two to four radials cut to resonance, about λ/4, sloping slightly downward. Length matters here. |
| Ground rod only | Needed for lightning and electrical safety, but it’s a poor RF counterpoise on its own. |
| End-fed and portable antennas | Use a short counterpoise wire (often 0.05 λ or more) plus a choke, or the coax becomes the counterpoise. |
| RF in the shack | Add or improve radials, add a 1:1 choke at the feed point, and a second choke where the coax enters the house. |
About the numbers: this is a teaching model, not an antenna modelling program. The pattern uses the standard ground-reflection maths for a vertical over real soil. Ground loss uses approximate figures based on the classic Brown, Lewis and Epstein radial measurements. Use it to understand the trends, then use your analyzer and your ears.
Last updated October 2026.