Replacing QRP EFHW with EF-OCF (EFOC): Same Convenience, More Honest

If you like the “one-end deployment” convenience of an EFHW but you’re tired of the system looking “too good” on an SWR meter (while behaving unpredictably in real installs), an EF-OCF setup is a very reasonable swap.

This article is pure HF: the goal is predictable multiband behavior for 0–20 W stations, without pretending that SWR equals efficiency.

What an EF-OCF really is

In the common EF-OCF (sometimes described as an end-connected OCF dipole or an EFOC) implementation, you’re building an off-center-fed dipole where the feedline exits at one end, but the RF behavior stays closer to a “real” OCF than to a magical end-fed.

• Electrically, it’s an OCF dipole with a feedpoint impedance typically in the few hundred ohms range.
• Matching is typically done with a 4:1 transformer at the feedpoint.
• The “short leg” is intentionally created by allowing a controlled length of coax shield to radiate.
• A 1:1 current choke is placed at a defined point to stop feedline radiation beyond that location.

Why EF-OCF is more honest about SWR and performance

It doesn’t pretend everything is 50 Ω on every HF band

A multiband EF-OCF is built around reasonable SWR across many bands, not “perfect SWR everywhere.” In practice, you’ll often see:

• Some bands look great without a tuner.
• Some bands are “fine” but not pretty.
• Some bands may still want a tuner — and that’s normal for multiband HF wire antennas.

That’s the point: you see the tradeoffs clearly, instead of having them hidden by a matching trick that makes the meter happy.

Lower ratio matching is usually easier to do efficiently

EFHW systems commonly require high transformation ratios because the feedpoint is at a high-impedance end-voltage point. EF-OCF moves the feedpoint to a region that’s typically much friendlier for matching, so a good 4:1 transformer is often a lower-loss, lower-stress solution in the real world.

Feedline radiation is controlled instead of ignored

Many end-fed debates boil down to one reality: the coax shield will radiate unless you deliberately control it. EF-OCF makes that mechanism explicit, then stops it with a defined choke point. That usually translates to:

• fewer “surprise” RFI issues in the shack
• more repeatable deployments (especially portable)
• a cleaner way to separate “antenna” from “feedline” after a known point

Where I²R fits for QRP

The I²R story matters in two different ways:

Efficiency and percentage loss

The fraction of power lost is mostly determined by the ratio between radiation resistance and total loss resistance.

Component heating and absolute watts

The heat in lossy parts scales with power. Jumping from 5 W to 20 W is 4× the power, and that can turn a “barely acceptable” transformer, choke, trap, or connection into something that runs warm and quietly eats dB.

This is one reason EF-OCF can be a very practical QRP choice: you’re often not forcing small hardware to do a huge ratio transformation at a nasty impedance point.

HF QRP antenna picks

0–5 W

• Linked dipole / resonant dipole / inverted-V — high efficiency, low avoidable loss, very predictable.
• Full-wave loop — often efficient and can be pleasantly quiet.
• Doublet + ladder line + tuner — one of the best true multiband HF solutions because ladder line stays low-loss even with high SWR.
• Quarter-wave vertical with real radials — excellent DX angles if the radial system is done properly.
• EF-OCF (done intentionally) — end-fed-like deployment convenience with more controlled, repeatable behavior.

5–20 W

• All of the above still apply.
• Trapped dipoles (good designs) become more practical.
• Moderately shortened dipoles can be fine (avoid extreme loading if you can).
• End-fed random wire + tuner can work well (but only if you treat counterpoise and common-mode control seriously).

EF-OCF checklist for repeatable results

• Place the choke where the design expects it — that location defines the radiating coax section.
• Keep the radiating coax section away from the operating position — it is part of the antenna.
• Use a solid 4:1 transformer and a real current choke — build quality matters more than “marketing ratios.”
• Accept that some bands want a tuner — that’s not failure; it’s multiband HF reality.
• Don’t confuse SWR with efficiency — a “pretty” SWR curve can hide loss, and a “meh” SWR curve can still radiate very well with a low-loss system. Read the SWR myth explainer with real numbers.

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