KPC FIELD TOOL
RADIALS: HOW MANY & HOW LONG
The question every vertical owner asks. Pick your band and how your radials are laid out, and see how much signal you lose in the dirt, what one more radial buys you, and exactly what to cut.
Show as a table
- Raised radials must be tuned: about a quarter-wave each, because they are not touching the dirt.
- 2 to 4 radials is plenty when the base is 6–10 ft up. More than 4 adds little.
- Run them out evenly (2 opposite, 3 at 120°, 4 at 90°). One or two radials make the pattern lean toward them a little.
- Droop them 30–45° to raise the feed impedance toward 50 Ω, a better match.
- Keep the ends off the ground and away from people: the tips carry high voltage when you transmit.
All Bands At A Glance
On-ground lengths are the point where making them longer stops helping much for that many radials (average soil). Raised radials are a tuned quarter-wave.
Radials, Answered
Do on-ground radials need to be a quarter-wave long?
No. Radials lying on (or just under) the ground are detuned by the soil, so there is no magic length. What matters is how many you have and how far they reach. With only a few, short ones work almost as well as long ones. Long radials only pay off once you have a lot of them. Rule of thumb: more radials beats longer radials.
Why do raised radials have to be cut to length?
Up in the air, a radial acts like the other half of the antenna, so it needs to be resonant (about a quarter-wave). A few tuned raised radials, 6 ft or more up, can work about as well as dozens laid on the ground. Below 2–3 ft they start acting like ground radials again: more loss and harder to tune.
My SWR went up when I added radials. Did I break something?
Probably not. A vertical over a poor ground system shows extra resistance (the ground loss), which can make the SWR look great. As you add radials that loss drops and the feed heads toward about 36 Ω, which is about 1.4:1. A slightly higher SWR with more radials usually means more of your power is getting out.
Bare wire or insulated? Do they have to be straight?
Either wire works. Insulated wire lasts longer on the ground and is easier on hands; for raised radials it makes the tuned length a bit shorter (trim to resonance). Radials don’t need to be perfectly straight. Spread them out as evenly as the site allows and don’t let them bunch up. Connect them all together at the base of the antenna.
What about a multiband whip (17 ft or 25 ft)?
Ground radials work on every band at once, so cut them for the lowest band you use and they help on all the others. Raised radials are tuned for one band: for several bands use a set per band, or switch to radials on the ground.
Is a counterpoise the same thing as radials?
Not quite. End-fed and random-wire antennas use one counterpoise wire (17–25 ft is common) mainly to give the feedline current somewhere to go. A vertical depends on its radials far more, because the ground return is half of the antenna.
Park rules?
Lay radials where nobody walks, flag them, and pick them all up when you leave. Never stake into graves, historic sites or fragile ground. See antenna safety and park manners.