Why an EFOC Is the Smarter Choice for Camper Installations

When space is limited — like on a camper — many operators default to an End-Fed Half-Wave (EFHW) antenna. While EFHWs are popular for their single-ended feed and simplicity, they have technical limitations that make them less than ideal for portable, low-profile setups. An End-Fed Off-Center (EFOC) provides a far more efficient, flexible, and predictable option — especially when installed as an Inverted-L using the camper roof as the feedpoint location.

The EFHW Problem in Camper Use

EFHW antennas — especially so-called “wideband” designs — are marketed as multiband solutions. In reality, they are not truly wideband; they rely on a transformer (often 49:1) that only works efficiently over a narrow range of frequencies. Outside that range, transformer loss increases and efficiency drops. On lower bands, the vertical orientation common in camper installations also adds ground loss unless the feedpoint is placed roughly half a wavelength above ground — impractical in most portable scenarios.

Why the EFOC Excels

An EFOC8, EFOC17, or EFOC29 shifts the feedpoint off-center, allowing the transformer to operate at a more optimal impedance ratio (often 4:1 to 6:1) rather than the extreme 49:1 of EFHWs. This reduces core loss, improves SWR bandwidth per band, and keeps current distribution more symmetrical for cleaner radiation patterns.

For a camper setup, placing the feedpoint on top of the vehicle keeps the matching unit away from ground loss. From there, the wire can run vertically for several meters and then horizontally or diagonally — making a highly effective Inverted-L.

Inverted-L Installation for a Camper

• Mast height: Use a 10 m or 16 m telescopic mast with a pulley at the top.
• Vertical spacing: Keep the vertical wire ~1 m away from the mast using a 1–2 m rope from the pulley.
• Horizontal run: Extend toward a convenient anchor point like a nearby tree, pole, or fiberglass support.
• Feedpoint: Mounted securely on the camper roof for minimal ground coupling.

This geometry gives a strong low-angle component for DX while still maintaining usable NVIS performance on lower bands. Unlike EFHWs, the EFOC transformer does not suffer the same level of heating or efficiency loss when operated multiband in this configuration.

Technical Advantages Over EFHW

• Lower transformation ratio → lower ferrite core heating.
• Better multiband efficiency due to less extreme impedance swing.
• Cleaner current distribution → more predictable radiation patterns.
• No reliance on lossy “compensation capacitors.”
• Can be tailored to target bands (8 m, 17 m, 29 m versions available).

What About Tuners?

One reason EFHWs are popular is that they often present a low-SWR point on multiple bands without a tuner. However, this is achieved through a single parallel resonant circuit (often the “compensation capacitor” in the transformer housing), which is inherently narrow-band and lossy on out-of-resonance bands. An external tuner paired with an EFOC offers far greater flexibility: modern tuners are highly efficient, and in a camper installation the coax run is so short that feedline loss is negligible. This means you can operate efficiently across all HF bands without depending on the compromises of a fixed parallel-resonant match.

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