Why We Call the EFOC29 a Near-Resonant Multiband Antenna

Many hams throw every end-fed wire into the “EFHW” bucket, but the EFOC29 behaves very differently. It is closer to an off-center-fed dipole that just happens to be end-fed, with a short leg that you must treat as part of the antenna — not as disposable feedline you can bury.

The short version:

The EFOC29 is a near-resonant antenna with a workable SWR (< 3:1) on multiple HF bands, and often higher real efficiency than a classic EFHW, because more of the wire radiates at a sane impedance and the transformer is far less stressed.

What the EFOC29 Actually Is

A typical 80–10 m EFOC29 layout uses:

• Long leg: ~29 m (main radiator)
• Short leg: ~12 m (coax section or a dedicated counterpoise)
• Feedpoint: between the two legs
• Matching: 4:1 unun → 50 Ω
• Choke: placed at the end of the short leg (~12 m from the transformer)

Total length ≈ 41 m — essentially a half-wave on 80 m.

So the EFOC29 is:

A half-wave wire fed off-center, with the long side doing most of the radiating and the short side completing the current path.

This moves the impedance away from the extreme end-feed point and into a much more cooperative zone.

Near-Resonant Feedpoint vs Classic EFHW

In a true EFHW (EFHW-8010 style), the feedpoint sits at a very high impedance (2–4 kΩ), which requires a 49:1 or 64:1 transformer and produces:

• Extreme RF voltage at the feedpoint
• High ferrite stress and heating
• Sensitivity to gutters, walls, wet trees
• Narrow practical bandwidth

The EFOC29, however, is fed only ~25% from one end, giving 150–300 Ω on 80 m — ideal for a 4:1 unun. This produces:

• Lower voltage, higher current
• Cooler, more efficient transformer
• Much broader SWR curves
• Less sensitivity to surroundings

That’s why I call the EFOC29 a near-resonant multiband antenna: its feedpoint sits close enough to resonance that SWR stays within the comfort zone of most internal tuners.

Why the Short Leg Acts Like a Counterpoise (and Why You Must Not Bury It)

The short leg of an EFOC29 — whether it is coax shield up to the choke or a dedicated insulated wire — is part of the radiator.

It:

• Carries real RF current
• Defines the feedpoint impedance
• Completes the off-center-fed half-wave

If you bury the short leg or run it inside metal conduit:

• Radiation is suppressed
• Feedpoint impedance shifts unpredictably
• SWR becomes unstable
• The “near-resonant” behavior disappears

Rule of thumb:

• Transformer → choke: treat as antenna (keep in the clear)
• After choke: normal “quiet” coax (bury or route freely)

Why the EFOC29 Often Covers More Bands with < 3:1 SWR

The combination of:

• Low-to-moderate feedpoint impedance
• 4:1 unun
• Shorter high-band effective radiator

…results in broad, gentle SWR curves that many radios can tune without breaking a sweat. In practice you often get:

• 80 / 60 / 40 / 20 / 17 / 15 / 12 / 10 m with < 3:1 SWR
• 6 m sometimes usable depending on height and layout

Efficiency: Radiating Length vs λ (Why the EFOC29 Can Win)

Lower-Loss Transformer

A 4:1 unun at a few hundred ohms runs dramatically cooler and with less circulating reactive current than a 49:1 EFHW transformer.

This alone can recover a dB or more of radiated power in real-world installations.

More Favorable Length on the Upper Bands

A full-length 80 m EFHW is almost 4 wavelengths on 10 m → very narrow lobes, violent nulls.

The EFOC29 long leg is ~29 m → ~2.7–2.9 λ on 10 m → fewer nulls, broader lobes, more usable directions.

Combine that with lower transformer loss and the EFOC29 often becomes the more efficient real-world antenna above 20 m.

TL;DR

The EFOC29 is a near-resonant 80–10 m end-fed off-center antenna. It uses ~29 m as the main radiator and ~12 m as a short leg (coax or wire) feeding through a 4:1 unun and a choke. The feedpoint impedance is a few hundred ohms — not a few thousand — so SWR stays manageable (< 3:1 on several bands) and the transformer runs much cooler and as such more efficiently than a 49:1 EFHW. The short leg is part of the antenna: treat it like a counterpoise, but do not bury or enclose it. After the choke, the coax becomes “quiet” again.

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