About Counterpoise

About “Counterpoise” — What It Means, and Why You Probably Don’t Need One

First, a quick primer for newcomers

Before we tackle the word counterpoise, let’s get the basics straight.

An antenna is just a piece of wire (or several pieces) that radio energy flows into. To radiate that energy as radio waves, the electricity has to have somewhere to “push against.” Think of it like clapping your hands: you need two hands to make the sound. One hand alone doesn’t do much.

In antenna terms, those “two hands” are called the two halves of the antenna. In a classic dipole antenna, the two halves are obvious — it’s literally two equal wires sticking out from a center feed point, like a “T” lying on its side. The radio’s energy pushes one half positive while the other goes negative, then they swap, millions of times per second. That back-and-forth is what creates radio waves.

So where does the term counterpoise come in? When an antenna doesn’t have an obvious second half — for example, a vertical whip antenna mounted on the ground — engineers in the early days of radio added a network of wires under it to serve as the “missing half.” That network became known as a counterpoise: literally, something that counters and balances the main antenna.

The official definition

The ARRL Handbook (Straw, 2003) defines counterpoise as:

“A wire or group of wires mounted close to the ground, but insulated from the ground, to form a low impedance, high-capacitance path to ground. Used at MF and HF to provide an RF ground for an antenna.”

In plain words: a counterpoise is a set of wires sitting just above the dirt — not touching it — designed to look “electrically friendly” to radio energy so that the antenna has something to push against without actually being bolted to the earth.

Why the word causes so much confusion

The article “Counterpoise” by Owen Duffy, VK2OMD (ex VK1OD) points out that the term has drifted so far from its original meaning that it now means almost nothing specific:

“Counterpoise means all things to all hams. Because of its lack of clear and unique meaning, wise authors avoid its use. Let’s explore a rational meaning based on the roots of the word. It has two roots, counter and poise:”

• Counter — in the opposite direction
• Poise — in a state of balance

Put those together and “counterpoise” should mean something that balances the antenna by pushing in the opposite direction. That’s a useful concept — but only when the antenna actually needs that kind of help.

Where modern hams go wrong

Today, the word counterpoise gets thrown around constantly, especially in discussions about End-Fed Half-Wave (EFHW) antennas. A common belief is that you must add a short hanging wire — often called a “pigtail” — to the ground lug of the transformer for the antenna to work properly.

Here’s the problem: a single short wire dangling from the coax shield at the transformer is not what the ARRL definition describes. It is not:

“presenting low impedance, a high-capacitance path to ground.”

It’s just a piece of wire hanging in the air. It looks reassuring, but electrically it’s doing very little of what people imagine it’s doing.

So what counterpoise does an EFHW antenna need?

The honest answer: none.

Here’s why. An EFHW antenna is one half-wavelength of wire fed at its end. At that feed point, the impedance is naturally very high (a few thousand ohms), which is why we use a high-ratio transformer — the 49:1, 56:1, 64:1, or 81:1 UNUNs — to step it down to the 50 ohms your radio expects.

Because the antenna is already a complete half-wave radiator, the radio energy doesn’t need a separate “second half” hanging off the transformer. The antenna finds its own electrical path back to a low-impedance reference. In most installations, that path is:

the coaxial cable shield, running back to your shack, where it’s bonded to the grounding system at the entrance of your home — as required by the National Electrical Code, Article 810 (NEC-810).

That’s the real “return path.” Not a little pigtail.

What if the coax shield isn’t even connected?

Here’s where it gets interesting — and where physics quietly does the work for you.

Even if the coax shield is not connected to the secondary winding of the transformer, the antenna still works. The return path is established through something called displacement current.

Without getting too deep into the math, displacement current is what flows through a capacitor — and a capacitor doesn’t need a wire between its plates to “conduct.” It conducts through the electric field in the empty space between them. The whole world around the antenna — the air, the cable, the ground beneath it — forms a giant, distributed capacitor. Radio-frequency energy happily flows through that field, even where no copper wire exists.

We verified this on the bench. You can watch the test here, which shows no change in VSWR whether or not the coax shield is used as a so-called “counterpoise”:

Video: VSWR test with and without coax shield “counterpoise”

Even the experts say it’s a misused word

The late L.B. Cebik, W4RNL — one of the most respected names in amateur antenna analysis — opens his article “Counterpoise: On the Use and Abuse of a Word” with this:

“The term counterpoise has a long history in antenna engineering and amateur practice. Today, it may be among the most misused terms in amateur circles. Indeed, if we examine both the history of the term, its meaning, and its misuses, we might reach an interesting conclusion: there is no such thing as a counterpoise in antenna analysis, even though the term has a long and somewhat respectable use in antenna engineering.”

In other words, two of the most careful thinkers in the field — Duffy and Cebik — both arrive at the same conclusion: the word has been stretched so far that it’s lost its meaning, and most of what people call a “counterpoise” today isn’t really doing what they think it’s doing.

The bottom line

If you’ve installed one of our EFHW antennas and someone tells you that you need to add a counterpoise wire to make it work — politely smile and move on. The antenna is already complete. Mount it as high as you can, ground your coax properly at the entry to your home per NEC-810, and let the physics handle the rest.