Short Radials and the Myth: Misreading Rudy Severns' Work
There’s a persistent misinterpretation in ham radio circles, often repeated by antenna kit sellers, that undermines vertical performance: the idea that "short radials work just as well", supposedly based on Rudy Severns’ (not “Severens”) (N6LF) work. The truth? That’s not what Rudy showed at all.
The Origin of the Myth
Rudy Severns (not “Severens”) (N6LF) is a respected RF engineer who published detailed measurements and NEC models of vertical ground systems, including "Ground Systems as a Part of Antenna Systems." One of his findings was that a very large number of short radials can partially approximate a field of fewer long radials. But his data has been badly simplified into the myth that "just a few short radials are good enough." That’s false.
What Rudy Actually Said
- Dozens of short radials (60+ at 0.05–0.1 λ) can approach the efficiency of fewer long radials.
- If you reduce both length and number, efficiency collapses — ground resistance rises sharply.
- The "diminishing returns" curve begins only after you’ve already laid down substantial copper. Below that, every missing meter counts heavily.
The Science: Ground Resistance Matters
The efficiency of a vertical is determined by the ratio of its radiation resistance (Rr) to the sum of Rr plus loss resistance (Rg + Rloss). Ground loss (Rg) is directly tied to the quality and extent of the radial system.
The difference between 2 Ω and 10 Ω of loss resistance is not subtle. That’s the difference between being heard at S7 and fading below the noise.
| Radial Setup | Approx. Ground R (Ω) | Efficiency vs 35 Ω Rr | Power Lost |
|---|---|---|---|
| 4 × short (2 m @ 40 m) | ~10 Ω | ~78% | ≈1.1 dB |
| 8 × short (2 m @ 40 m) | ~6–8 Ω | ~82–85% | ≈0.7–0.9 dB |
| 16 × 0.25 λ (10 m @ 40 m) | ~3–4 Ω | ~90–92% | ≈0.4–0.5 dB |
| 32 × 0.25 λ (10 m @ 40 m) | ~1–2 Ω | ~95–97% | ≈0.1–0.2 dB |
Values are indicative and vary with soil conductivity, moisture, and installation quality — but the trend is universal.
Raised Radials: An Alternative Approach
There is one valid shortcut: tuned elevated radials. Instead of dozens of wires on the ground, you can use 2–4 radials cut to roughly ¼λ and elevated at least 0.05–0.1λ above ground. These act as efficient current return paths without relying on soil conductivity. The result: efficiency nearly equal to a dense ground field, with far less copper.
- Requires careful trimming of each radial to resonance.
- Placement height matters — too low, and soil losses creep back in.
- Best suited for monoband or narrow-band verticals, since each set of radials must be cut for the operating frequency.
Elevated radials don’t replace a ground field in multiband verticals — but on single-band designs, 2–4 tuned radials can rival or outperform 60+ short wires on the ground.
Practical Advice for VertX Users
The RF.Guru VertX multiband vertical is engineered for efficiency from 20 through 6 meters. To unlock that performance:
- Minimum radial length: ~3.2 m (≈0.25 λ at 20 m)
- Recommended number: 16 or more
- Performance-maximized: 32+ radials, 3.2–3.5 m each, evenly spread around the base
Don’t fall for the “4 short radials is fine” story. You’ll get an SWR dip — but you’ll also lose multiple dB of ERP. That’s the difference between a strong DX contact and being buried in QRM.
Conclusion
Rudy Severns (not “Severens”) never claimed that a handful of short radials work as well as long ones. His carefully controlled work showed that short radials only work when you have many — and they still don’t beat long radials in efficiency. Elevated radials, on the other hand, can be a smart alternative for monoband setups. Misreading his results leads directly to weak signals and frustrated operators.
If you want your vertical to deliver, don’t skimp on radials. More copper in the ground — or tuned wires elevated — equals more dB in the air.
Mini-FAQ
- Do short radials really work? — Only in very high numbers (60+). A handful of short radials will cause major efficiency losses.
- Why are long radials better? — They couple more effectively to ground, keeping ground resistance low and efficiency high.
- Can I use just 4 or 8 short radials? — You’ll get a low SWR, but your signal will be down several dB compared to a full field.
- Are elevated radials effective? — Yes, 2–4 tuned elevated radials can rival a dense ground system — but only for narrow-band/monoband verticals.
- What’s best for VertX? — At least 16 radials of ~3.2 m, ideally 32+ for maximum efficiency on 20–6 m.
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