The FullHalfWave Series (EF FHW): Dual Half-Wave EFHWs Reimagined for Real-World DX
What if we told you that you could get two half-wave resonant bands — like 40m & 20m or 20m & 10m — from a single end-fed wire, with no lossy traps, no weird current nulls, and no gimmicks? Meet the FullHalfWave series (EF FHW), a next-gen EFHW concept designed for serious DX performance in deceptively compact layouts.
What Makes It Special
The FullHalfWave antennas are dual half-wave (EF FHW) designs that use a non-resonant trap to preserve continuous current flow while subtly shifting the current distribution. This isn't a "multi-band compromise" — it's a deliberate DX build that treats both bands as first-class citizens.
Available Variants
- FullHalfWave 4020 → ~31.4 m of wire (40m + 20m half-wave)
- FullHalfWave 2010 → ~15.2 m of wire (20m + 10m half-wave)
⚠️ Due to the increased length, this technique is best suited for these two band combinations. Both offer exceptional performance when properly deployed.
Radiation Pattern Comparison
FullHalfWave 4020 (40m + 20m)
| Band | Wire Segment | Orientation | Avg Height | Takeoff Angle | DX Rating |
|---|---|---|---|---|---|
| 20m | First 10.7 m | Vertical or steep sloper | ~10–11 m apex | 15°–20° | ⭐⭐⭐⭐⭐ |
| 40m | Full 31.4 m | Inverted-L (4–6 m feed) | ~6 m avg | 25°–30° | ⭐⭐⭐⭐⭐ |
FullHalfWave 2010 (20m + 10m)
| Band | Wire Segment | Orientation | Avg Height | Takeoff Angle | DX Rating |
|---|---|---|---|---|---|
| 10m | First 5.2 m | Vertical | ~5–6 m | 10°–20° | ⭐⭐⭐⭐⭐ |
| 20m | Next 10.7 m | Vertical or sloper | ~10 m | 15°–25° | ⭐⭐⭐⭐⭐ |
Why These Dual EF FHWs Are DX Beasts
- Both bands resonate at half-wave length → optimal current peaks → full ERP output
- No resonant traps → minimal insertion loss, just current shaping via non-resonant trap
- FullHalfWave 2010 can be fully vertical → extreme low-angle performance in just 15m of wire
- FullHalfWave 4020 spreads energy across low angles for both bands — vertical + horizontal synergy
Transformer Matching & Feedpoint Behavior
| Variant | Primary Band | Feed Height | Feed Z Estimate | Recommended Transformer |
|---|---|---|---|---|
| FullHalfWave 4020 | 40m | 4–6 m | 3.5–4.5kΩ | 70:1 ✅ |
| FullHalfWave 2010 | 20m | 3–4 m | 2.2–2.5kΩ | 49:1 ✅ |
On 4020, the trap controls current distribution on 20m, but is electrically invisible for 40m — the whole wire radiates as a 40m EFHW.
70:1 provides a better match in most inverted-L setups for 40m where feedpoint impedance exceeds 3.5kΩ.
Theory Meets Reality
⚠️ This is currently a theoretical model. Matching, bandwidth, and real-world noise behavior still need to be field-tested. We will update this article with results once test deployments are complete.
The FullHalfWave EF FHW Series: 2 bands. Full half-wave resonance. Zero compromise.
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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.