Why the EFOC29 Works Perfectly on 80 m in Europe
but Americans Need a Tuner
The EFOC29 is designed around the European 80 m allocation (3.5–3.8 MHz). In Europe, this band aligns cleanly with the natural harmonic structure of a 29 m off-center-fed wire using a 4:1 UNUN and a 12 m counterpoise section in the coax.
In the United States, however, the situation is very different. What Americans commonly refer to as “80 m” above 3.8 MHz is actually the 75 m band segment — and this part of the spectrum is not a harmonic match to 40 m or 20 m.
Because of this, the EFOC29 will still radiate well in the US, but the SWR point for the upper band (3.9–4.0 MHz) naturally sits much higher than in Europe. As a result, an external tuner is required for American operators who wish to operate above 3.8 MHz.
The Key Difference: 80 m in Europe vs 75 m in the US
| Region | Band Allocation | Effect on EFOC29 |
|---|---|---|
| Europe | 3500–3800 kHz | Full band aligns with natural 80 m resonance → tuner optional |
| United States | 3800–4000 kHz (“75 m”) | Not a harmonic → resonance point too low → tuner required |
The EFOC29 is built to be a true multiband performer without traps, coils, or complex wire breaks. But harmonic antennas depend heavily on where the fundamental frequency is placed — and European 80 m sits lower than the American operating segment.
Why the Upper US Segment Cannot Be Harmonic
The physics of harmonics are simple: the 40 m, 20 m, 15 m, and 10 m bands align nicely when the fundamental is around 3.55–3.7 MHz.
If you shift the base resonance to 3.9 MHz:
- 40 m shifts upward
- 20 m shifts upward
- 10 m becomes chaotic
- The entire multiband behaviour becomes less predictable
This is why we do not tune the EFOC29 for the US 75 m segment: doing so would degrade performance on all higher HF bands.
Europe: A Perfect Fit
In Europe the band sits exactly where a 29 m end-fed off-center antenna wants to resonate. The result:
- Excellent SWR in the lower half of 80 m
- Tunable upper half (even with small internal tuners)
- Beautiful harmonic alignment on 40/20/10 m
- No traps, no inductors, no losses
This is why the EFOC29 is especially attractive for portable operators, SOTA, POTA, and small-garden HF setups in CEPT regions.
What American Operators Should Expect
If you operate in the 3.8–4.0 MHz “75 m” US segment, you’ll simply need a tuner — even a small internal tuner will do.
At 3.5–3.8 MHz, the antenna behaves normally. Above 3.8 MHz, the mismatch grows, because 75 m is not the second or third harmonic of anything in the rest of the HF band plan.
This is normal and expected behaviour for any harmonic-derived multiband wire antenna.
Mini-FAQ
Frequently Asked Questions
- Do European operators need a tuner on 80 m? — Only at the upper edge. Most of the EU band sits near the natural resonance of the wire.
- Do Americans need a tuner on 75 m? — Yes. The band is not harmonic and sits above the natural resonance.
- Will retuning the antenna fix it? — Not without breaking 40/20/10 m performance. We do not recommend it.
- Is performance affected? — No. With a tuner, the EFOC29 performs extremely well on US 75 m.
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