Why Your EFHW Is Eating Your Signal – And the EFOC Isn’t
If you think all end-fed antennas are created equal, think again. The EFOC (End-Fed Off-Center) consistently outperforms the classic EFHW (End-Fed Half-Wave) in real-world multiband operation. The reasons come down to transformer losses, feedline interaction, and how the designs handle impedance across multiple bands.
Transformer Losses: EFOC vs EFHW
Traditional EFHWs rely on high-ratio impedance transformers (49:1 or 64:1). These ratios are inherently inefficient: too many turns of wire, higher leakage inductance, and more ferrite heating. At 100 W, you can easily lose 1.5–2 dB in the transformer alone — that’s up to 35% of your signal wasted before it leaves the feedpoint.
The EFOC, by contrast, uses a simple 4:1 UNUN. With far fewer turns and a lower voltage ratio, losses are negligible (<0.1 dB), even at high power. Less ferrite stress means more RF is radiated instead of being burned off as heat.
The Masking Trick of EFHWs
Many EFHWs use a series compensation capacitor to “smooth” the SWR curve. This makes the SWR meter look friendly, but the losses remain. The capacitor doesn’t fix the transformer inefficiency—it simply hides it. Worse yet, the apparent good match on 80m and 60m is often an illusion, with over half the input power lost in the transformer and feedline.
At RF.Guru, we do not sell “broadband EFHWs” for bands below 20m. No ferrite material can efficiently cover 80–10m with one transformer. Instead, we tailor cores to specific bands and never rely on capacitors to mask poor efficiency.
Total Losses: Transformer + Feedline
Even with decent SWR figures, EFHWs suffer significant real-world losses. The table below compares typical EFHW designs with our EFOC approach at 100 W input power, including coax losses on a 20–30 m run.
Realistic Efficiency Comparison @ 100W Input
| Band | EFHW SWR | EFHW TX Loss (dB) | EFHW Coax Loss (dB) | EFHW Total Loss | EFOC SWR | EFOC Loss (Total dB) |
|---|---|---|---|---|---|---|
| 80m | 2.5:1 | 1.8 | 0.25 | 2.05 | 2.0:1 | 0.21 |
| 60m | 5.0:1 | 1.3 | 0.62 | 1.92 | 2.2:1 | 0.23 |
| 40m | 2.0:1 | 0.7 | 0.21 | 0.91 | 1.8:1 | 0.19 |
| 30m | 3.5:1 | 1.2 | 0.45 | 1.65 | 3.5:1 | 0.45 |
| 20m | 1.5:1 | 1.0 | 0.17 | 1.17 | 1.4:1 | 0.16 |
| 17m | 4.0:1 | 0.9 | 0.55 | 1.45 | 2.9:1 | 0.28 |
| 15m* | 2.8:1 | 1.2 | 0.29 | 1.49 | 2.0:1 | 0.19 |
| 12m* | 6.0:1 | 1.4 | 0.77 | 2.17 | 3.2:1 | 0.35 |
| 10m* | 1.8:1 | 1.1 | 0.20 | 1.30 | 1.6:1 | 0.18 |
*Note: EFHW SWR figures on 15–10m are often worse without a capacitor “fix.” Transformer stress is highest on these bands, leading to reduced efficiency and premature ferrite heating.
EFOC Advantage: Real-World Efficiency
- Lower ratio transformers = minimal heating
- Better impedance match = lower coax loss
- Shorter wire length = fewer installation compromises
- Predictable lobes = more consistent DX performance
- All-band usability with realistic efficiency, not capacitor illusions
Stop burning watts. Ditch the EFHW. Switch to EFOC.
Mini-FAQ
- Why is my EFHW inefficient? — High transformer ratio, ferrite heating, and capacitor tricks hide SWR but not losses.
- Does the EFOC need a tuner? — Sometimes on fringe bands (30m, 17m, 12m), but SWR stays under 3:1 in most installs.
- Is the EFOC better for DX? — Yes. Lower losses and more predictable lobes give it the edge on high bands.
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