Why We Love Doublets (and Why the G5RV Fails)
There is a deep and enduring love among seasoned radio amateurs for the humble doublet antenna. Suspended high and fed with open-wire line straight into a good tuner system, the doublet is simple, elegant, and forgiving. It’s the kind of antenna that, once installed properly, becomes a reliable workhorse.
In contrast, the G5RV and its many siblings are often more trouble than they’re worth. Sure, on paper they promise multiband capability without fuss. But in practice? They’re a house of cards held together by theoretical idealism — and they crumble like a poorly impeded apple cake at the first sign of real-world complexity.
Mark’s take on this topic: Our friend Mark — K3ZD (“Ham Florida Man” on YouTube) — delivers a video in the same spirit: skeptical of the G5RV hype and giving well-deserved praise to the straightforward doublet. Watch it here:
The Doublet: Unapologetically Honest
A doublet is a center-fed dipole of any convenient length, typically 2×13 m to 2×40 m, fed with open-wire or ladder line (450–600 Ω). At RF.Guru we use high-power 600 Ω open-wire feedline for maximum efficiency and minimal loss. There is no built-in expectation that it will be resonant on any band — and that’s a feature, not a bug. High feedpoint SWR is handled where it belongs: at the tuner. The balanced line keeps loss negligible, even under mismatch. The result is repeatable multiband performance with modest sensitivity to weather and surroundings.
- Height & pattern: ~0.5 λ on the band of interest gives strong low-angle energy; higher adds useful lobes on higher bands.
- Feedline discipline: Keep balanced line away from metal, route symmetrically, avoid sharp bends.
- Matching: Use a balanced tuner, or an unbalanced tuner with a 1:1 current balun on the output to the ladder line.
What makes the doublet so attractive is its brutal honesty. It makes no secret of its needs. It says, "I’ll work across many bands — but give me height, give me balance, and give me a good tuner."
The G5RV: A Misunderstood Trickster
More trouble than it’s worth, prone to crumble like a house of cards or a poorly made apple cake!
The G5RV, created by Louis Varney (G5RV), is a ~31 m dipole with a specific length of twin-lead designed as a frequency-dependent matching stub. It was originally intended for 20 m only. Over the years, folklore inflated it into a “multiband miracle.”
The system relies on a delicate interplay between:
- The antenna’s height above ground (current distribution changes)
- The exact length and impedance of the stub feedline
- The coaxial feed and any tuner used
This is a precarious, carefully tuned game. When everything is perfect — height, environment, feedline length, ground conductivity — it can provide decent performance on multiple bands. But when conditions change? Rain, wind, seasonal moisture, or even leaves brushing the feedline can shift the impedance enough to detune the whole system. And suddenly your G5RV turns into an obstinate, mismatched wire that no tuner can coax back to life.
- Built-in loss path: High SWR often rides on the coax, which multiplies loss with frequency.
- Environment-sensitive: Rain, foliage, or minor height changes can skew the impedance dramatically.
Apple Cake and Other Siblings
Many variants of the G5RV have sprung up over the years:
- ZS6BKW: A re-optimized version for better multiband coverage, especially on 10 and 17 meters.
- W5GI "Mystery Antenna": A G5RV-style system with phasing lines to emulate gain patterns — another cake balanced on toothpicks.
- G0FAH Optimized G5RV: Another attempt to tweak the feedline length for better matching.
Each one tries to mitigate the G5RV’s instability by shifting the game board, but they still rely on a complex interplay of environment, height, and coaxial interaction. They are intricate solutions to a problem that doesn’t exist if you just run a doublet and feed it properly.
Why the Doublet Wins
- Consistent: Once up, it doesn’t care much about weather or leaves.
- Efficient: Balanced line = negligible loss under mismatch.
- Scalable: Works from QRP to QRO with the right tuner and balun.
- Honest: Doesn’t pretend to be resonant. It just works — with help.
Practical Doublet Setup
- Wire: Longest symmetrical span possible (2×13 m, 2×20 m, or more).
- Height: Aim for ~0.5 λ on your primary band.
- Feedline: 450–600 Ω ladder line, routed clear of metal and siding.
- Tuner: Balanced preferred; if unbalanced, add a 1:1 choke balun on output.
- Choking: If coax is used inside, choke it at the tuner input.
Reality check: “Resonant 1:1 SWR” ≠ efficient. With doublets, low line loss + proper matching beats paper-perfect SWR every day.
- On the line: High SWR increases current/voltage peaks → extra loss in coax dielectric and copper.
- In the transmatch: Large |X| forces high circulating currents/voltages → I²R losses in coils and ESR in capacitors.
- At the radiator: That’s where you want the power. Matching closer to the feedpoint cuts line loss dramatically.
Useful math: reflection coefficient |Γ|=(SWR−1)/(SWR+1); mismatch loss ML=−10·log10(1−|Γ|²). These describe the match at a point — not total system efficiency.
| Aspect | Doublet | G5RV |
|---|---|---|
| Design intent | General multiband via ladder line + tuner | Originally 20 m only; folklore inflated |
| Feedline | 450–600 Ω balanced, low loss even mismatched | Coax with stub → coax loss rises under SWR |
| Weather stability | Relatively stable; insensitive to rain/leaves | Highly sensitive; rain/moisture shifts impedance |
| Efficiency | High, even under mismatch | Lossy when SWR high on coax |
| Complexity | Simple wire + tuner | Delicate interplay of height, stub length, environment |
Final Thoughts
The G5RV is clever engineering for a specific purpose, stretched by folklore into a one-size-fits-all promise. A well-sited doublet is simpler, more efficient, and predictable across HF. Build it once, feed it right, and enjoy years of dependable multiband operation.
So next time you’re tempted by the apple cake of multiband magic, remember: sometimes the simplest solution, fed right and tuned well, is the sweetest.
Stick with the doublet. Leave the house of cards to the magicians.
Mini-FAQ
- Isn’t a G5RV “multiband without a tuner”? — Only if lengths and heights align perfectly. In most cases, a tuner is still needed, and coax loss rises under SWR.
- What’s the best doublet length? — The longest symmetrical span you can manage. Length + height define lobes and coverage.
- Do I need a balun? — Yes, if your tuner is unbalanced. Use a 1:1 current balun on the tuner output feeding the ladder line.
- Can I run QRO? — Absolutely. Balanced line handles power well; ensure your tuner/balun are rated for it.
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