Do HF Verticals Need Radials? What the Measurements Say
Signal Lab · Verticals
Do HF Verticals Need Radials? What the Measurements Say
Most ground-mounted HF verticals are half an antenna. The other half is supposed to be in your lawn: a fan of wires called radials. How much wire, and what you lose without it, is not a matter of opinion. One ham measured it, carefully, in a field in Oregon, and published every number.
This page walks through what he found, a one-minute test to see whether it applies to the antenna you are considering, and the other way to build a vertical: one that carries its own other half.
Why a Monopole Needs Wire in the Ground
A classic quarter-wave vertical is a monopole: one radiating element, fed against the earth. The RF current that flows up the element has to return through the ground near its base. Soil is a poor conductor, so some of your power heats the dirt instead of leaving as signal. Radials give that return current a copper path. The more radials, and the better laid out, the less power the soil eats.
What N6LF Measured
Rudy Severns, N6LF, spent a year measuring real verticals over real soil, adding radials a few at a time and recording the change in signal at a receiving antenna. His results ran in a seven-part QEX series in 2009 and 2010 and a summary in QST, March 2010. Three findings matter to anyone choosing a vertical:
On 40 meters, taking a quarter-wave vertical from no radials (a single ground stake) to 64 radials gained about 2.6 dB. Shorter, loaded verticals gained more, about 3.4 dB, because they lose more without help. Most of the improvement came with the first 16 radials. (QEX, May/June 2009, Part 4)
On 160 meters, going from 4 to 64 radials, each 130 feet long, raised the signal about 2.5 dB. That sounds small until you translate it: it is the difference between roughly 50% efficiency and over 90%. Sixty-four 130-foot radials is more than 8,000 feet of wire. N6LF's 160 m measurements →
A few long radials on the ground can be worse than expected. With sparse radial systems lying on the soil, he found ground loss can rise when the radials are made long, and shortening them can actually help. More copper is not automatically better; the layout matters. (QEX, January/February 2009, Part 2)
The short version: a ground-mounted monopole with a skimpy radial field can be throwing away close to half its power on the low bands, and fixing that takes dozens of wires and a lot of lawn. N6LF on radial design and efficiency →
The One-Minute Test
Open the manual for the vertical you are considering and search for the word "radials." If it tells you how many to lay, how long to make them, or how much better the antenna works with them, it is a monopole, and N6LF's numbers apply to it. Budget the wire, the staples and the afternoons, and plan where the field goes.
That is not a knock on any antenna. Monopoles over a good radial field are fine antennas, and many of the best low-band stations in the world use them. The question is only whether your yard can hold one.
The Other Way: A Vertical That Carries Its Own Other Half
Not every vertical is a monopole. A vertical dipole puts both halves of the antenna above ground, in aluminum, and the lower half carries the return current that a monopole would push through the soil. Nothing to bury, and nothing for the dirt to steal near the base. Half-wave designs and vertical dipoles from several makers work this way; it is how every Greyline is built.
A Greyline DX Vertical is an off-center-fed vertical dipole, 12 to 28 feet in the standard line and up to 41 feet in the HD Series, matched on every band from 160 through 6 meters by a wide-range tuner. It stands the same on sand, rock, a deck or a rooftop, because it never needed the ground to finish the job.
The Honest Caveat
Ground still matters for every vertical, ours included, far out from the antenna: the soil well beyond your property shapes how much low-angle signal survives the trip. No radial field changes that; N6LF's own modeling shows that far-field loss is almost independent of the radials. What radials fix is the loss near the base. A vertical dipole simply does not have that loss to fix.
Your Height, in One Page
Leave your email and we’ll send the one-page version of the Selection Guide: three questions that pick your height, to keep by the shack.
Choosing
If you have an open field, the patience to lay 32 or 64 radials and a lawn you never plan to dig, a well-built monopole over a real radial field is a fine antenna. If you have a suburban lot, a rooftop, rocky ground, a deck, or a spouse who would like the lawn back, a vertical dipole gets you on every band without the wire.
The DX Verticals → Find your height in four taps →
Sources
Rudy Severns, N6LF, "Experimental Determination of Ground System Performance for HF Verticals," Parts 1-7, QEX, 2009-2010; "An Experimental Look at Ground Systems for HF Verticals," QST, March 2010; notes at antennasbyn6lf.com. More of what we read is on the Bookshelf and in the Reading Room.
73 · Jon KL2A · Greyline · 435-200-4902
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