The Hidden Truth About the Counterpoise: It's Not What You Think!

When it comes to end-fed or off-center-fed antennas, many hams obsess over the radiator length, feedpoint impedance, and the matching transformer. But one thing that often gets brushed aside—or misunderstood—is the humble counterpoise. Let's set the record straight.

Does the Counterpoise Radiate?

In most typical EFOC or OCF configurations, the answer is: barely. The counterpoise, often a 1–14 meter length of wire or coax shield, is not intended to radiate. Its job isn’t to add gain, improve pattern, or contribute to DX performance.

What it does do is provide an electrical path for current balance at the feedpoint, preventing your coax from becoming an unwanted part of the antenna system.

Why It Matters Anyway

While the counterpoise might not be radiating, it's far from irrelevant:

  • Provides a defined return path at the feedpoint, preventing the coax shield from becoming part of the differential RF circuit (skin effect)
  • Reduces unwanted shield currents that arise from feedpoint imbalance — these are often mistaken for common-mode currents but are actually due to the skin effect driving RF onto the outer braid
  • Improves impedance consistency, which can lead to more predictable SWR across multiple bands (though it does not “stabilize” SWR on its own)
  • Slightly shifts feedpoint impedance and resonance, requiring radiator trimming for optimal tuning on the intended bands

That said, if you already have a reasonable SWR and a decent tuner, there’s no point in obsessing over the counterpoise. It won’t significantly alter the antenna’s performance. The real work is done by the radiator.

Also worth noting: with modern low-loss coax, power loss with SWR under 6:1 is generally negligible for most amateur power levels. This makes the system quite forgiving.

How Long Should It Be?

There’s no magic number, but a good rule of thumb is 0.05 to 0.1 wavelengths of your lowest operating frequency. This often results in counterpoises between 1 and 14 meters long, depending on setup.

But there’s room for compromise:

  • If it's too long, it may develop unwanted resonances.
  • If it's too short,

    it may fail to sufficiently dissipate or suppress return currents flowing on the feedline.

How to Fiddle It Away Without Breaking the System

Sometimes, there's just no space for a proper counterpoise—or you want to keep things tidy. Here’s how to cleverly integrate or hide it:

  • Mount it down the mast: If your mast is conductive (e.g., aluminum), beware: it can couple with the counterpoise, effectively shortening its electrical length. If so, you may need to shorten the wire.
  • Use the coax shield itself: Many designs use the first few meters of coax braid as an implicit counterpoise. But then you’ll absolutely need a choke at the correct position (often 0.05–0.1λ from feedpoint).
  • Run it in the opposite direction of the radiator: Especially if the radiator is long, it’s better to place the counterpoise away from it, to reduce unwanted coupling.
  • If it’s longer than the mast: You have more freedom. Lay it out horizontally, slope it, or even zig-zag it—as long as it’s not near the main radiator.
  • If you’re mounting it vertically down the mast: For QRP and moderate power setups, that’s often enough. But for higher power, consider insulating it from the mast or using a dedicated radial wire.

Final Word

Don’t treat the counterpoise like an optional afterthought. Even if it’s not radiating, it holds your whole system together—literally and electrically.

And remember: the radiator (the longer wire) is what determines your resonant points and overall performance. That’s the part you trim to match your preferred bands. Always read the antenna manual—it’ll have precise guidelines on radiator length tuning.

When implemented right, the counterpoise is invisible. When done wrong, you’ll see the mess on your analyzer, your waterfall, and even your transceiver.

Your antenna deserves better than a floating feedpoint. Respect the counterpoise.

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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.