Why an 80m/40m EFHW Inverted-L Outperforms a 10–13m High Vertical

We keep seeing the same story repeat itself: contest operators try a “practical” 10–13m vertical for 80m/40m… then swap it out after comparing it to a properly deployed EFHW Inverted-L. Not because verticals are “bad”… but because 80 meters punishes short verticals unless the return system is serious.

The differences in efficiency, radiation pattern, and matching/return-path losses often make the EFHW Inverted-L the more practical choice ... especially when the vertical cannot be supported by an efficient radial system on 80m.

(Inline note) This is a real-world comparison of typical installations. A full-size vertical over an excellent radial field can be outstanding ... it’s just rarely what people end up building.

Efficiency: where the 80m vertical usually bleeds power

On 40m, a 10–13m vertical can be quite usable. On 80m, that same radiator becomes electrically short (~0.12–0.16λ), and efficiency is often dominated by ground/return loss and loading loss.

On 80m, a 10–13m vertical is electrically short. Its radiation resistance is only on the order of a few ohms to roughly ~10Ω, so any series loss (ground/return resistance, coil loss, conductor loss) can easily become a large fraction of the total ... and efficiency drops fast unless the radial/return system and loading are excellent.

While it can work very well on 40m, using the same vertical on 80m requires significant loading/matching. The efficiency impact comes mainly from high RF current flowing through loss resistances (ground/return + loading components), not from “SWR” by itself.

What the EFHW Inverted-L does differently

• Cut for resonance on the intended band(s) and matched with an impedance transformer (UNUN). A tuner may still be used for full-band coverage, but you’re not relying on a high-current base-loading system like a short 80m vertical does.
• Half-wave in length: the end-feedpoint impedance at resonance is typically several kΩ. (That kΩ figure is feedpoint impedance at the end, not “radiation resistance”.)
• Often workable without a large buried radial field ... with one condition: it still needs a return path (counterpoise). Without proper choking/return-path control, the coax shield can become part of the antenna, changing SWR and pattern and causing RFI.

Radiation pattern: DX, regional, and what the “top wire” really does

A vertical and an Inverted-L can both radiate well ... but they don’t behave the same way across 80m and 40m in typical installations.

• Short vertical on 80m: performance depends heavily on how well you manage ground/return loss and loading loss. Even when efficient, a vertical is primarily a low-angle radiator, so it’s not the classic “best NVIS” choice compared with low horizontal wires.
• EFHW Inverted-L: a mix of lower-angle energy from the vertical section and higher-angle energy from the top horizontal section (useful for both DX and regional/NVIS paths on 80m), depending on height and geometry.

Usable performance across both bands ... but note that on 40m an 80m EFHW typically operates as a harmonic (often ≈1λ), so the pattern develops multiple lobes and nulls. Orientation matters.

Matching and losses: the part most “SWR debates” miss

A 10–13m vertical usually needs significant matching/loading on 80m. If the tuner is in the shack and you’re using coax, the high mismatch remains on the feedline, which can increase coax loss compared with a near-matched system at the antenna.

On 80m, the core issue is low radiation resistance: high RF current must flow to radiate power, and any series loss resistance (ground/return, loading coil, conductors) becomes a large percentage of the total ... so efficiency can be poor unless those losses are minimized.

Why RF.Guru Uses a 70:1 Transformer on 80/40 and 40m EFHW Inverted-L Antennas

A transformer ratio is not magic ... it’s simply chosen to transform the antenna’s real-world end-feed impedance down to ~50 Ω. A 70:1 impedance ratio corresponds to roughly 3500 Ω → 50 Ω (because 70 × 50 = 3500).

• Inverted-L geometry often shifts the real EFHW end impedance higher on low bands. In an Inverted-L where the vertical section starts at the feedpoint, ground interaction and current distribution change the end-feed impedance behavior. In our low-band Inverted-L designs (80/40 and 160/80), a higher-ratio transformer (about 68–70:1) tends to provide a more predictable match than the classic 49:1 approach that assumes ~2450 Ω. (49:1 can still “work” ... it’s just often not the cleanest match in this specific geometry.)
• 80/40 dual-band behavior: half-wave on 80m, harmonic on 40m. The ~41 m class radiator is half-wave on 80m and operates as a harmonic on 40m. In this deployment as an Inverted-L, we frequently see the “best practical match” land closer to a 70:1 transformation. That helps keep SWR in a usable range without relying on lossy “wideband tricks” ... and it improves high-power robustness by avoiding unnecessary current stress in the matching system.
• 40m monoband EFHW Inverted-L (EFHW40). Our 40m EFHW Inverted-L uses an integrated 70:1 UNUN because the real end-feed impedance in this configuration often maps cleanly toward 50 Ω with that ratio. We design the system (transformer + counterpoise/ground reference + choking strategy) as one RF solution ... not as disconnected parts.
• High voltage at the feedpoint. EFHW transformers operate at very high voltage at the antenna terminal (kV range at high power), so correct insulation, hardware, and safety spacing matter.

Bottom line: we use 70:1 on these Inverted-L EFHWs because it matches the actual several-kΩ end-feed impedances we commonly see on 80/40 and 40m in this geometry, resulting in lower SWR, more predictable deployment, and better high-power robustness than a one-ratio-fits-all approach.

Practical deployment: why this is often the “contest-friendly” choice

A 10–13m vertical benefits enormously from a good radial/return system ... especially on 80m, where radiation resistance is low and ground loss can dominate. That’s exactly why “it tunes” is not the same as “it’s efficient”.

An EFHW Inverted-L can be installed flexibly with one support ... but plan the return path: use a choke and a defined counterpoise/ground reference to keep SWR and pattern stable and to reduce RF in the shack.

Conclusion

A properly installed EFHW Inverted-L is often the better investment for reliable 80m + 40m performance ... especially if you don’t have the space (or desire) to install a serious radial system for a short vertical on 80m.

The win is rarely “because end-fed is magic”. The win is usually because you’re avoiding the worst loss mechanisms that short 80m verticals tend to suffer from in typical real-world installs ... and you’re deploying a system with controlled matching and a controlled return path.

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