WiMo’s Radials Guide: Where Useful Advice Becomes a Myth

Every few weeks I try to help radio amateurs move one step away from an old myth. Bad explanations do not stay on the page: they become unstable tuning, RF on microphone cables, noisy receivers and disappointed operators. That is why WiMo’s public guide to radials and counterweights caught my attention. A respected retailer can teach a great deal. It can also give an installation-dependent shortcut far more authority than it deserves.

My objection is to specific engineering claims, not the people who wrote them. There is worthwhile advice here: the return system matters, an earth rod is not a radial field, and elevated wires behave differently from wires touching soil. The trouble begins when those useful distinctions turn into universal promises.

The Good Starting Point: The Whip Is Not the Whole Antenna

A vertical does not simply need something called “ground.” It needs a defined RF return structure. Radials, a counterpoise, a vehicle body or a metal roof can provide it. The coax exterior, mast and station wiring can provide part of it too—whether you intended that or not.

Defining that path is an engineering advantage: tuning and current distribution become less dependent on whichever cable, hand or support happens to be nearby. A low-loss radial system directs more accepted power toward radiation instead of soil heating. Those are concrete reasons to build the return system well, not merely reasons to collect more measurements.

An EFHW Can Dispense With a Radial Field—not With Return Current

WiMo exempts the end-fed half-wave from conventional radials on the basis of its high feed impedance. Later, its FAQ acknowledges a small counterpoise or coax-shield section. That later distinction is important.

A high-impedance feed normally carries less terminal current than a low-impedance feed for the same accepted power into a resistive load. It does not make that current zero. A short intentional conductor, distributed capacitance, coax exterior or support can supply the complementary path. “No quarter-wave radial field” and “no return system” are different statements.

If the coax becomes that return conductor, adding a choke changes the antenna boundary and can shift tuning. The useful answer is to define the intended return structure and the choke boundary together. It is not to claim that the missing half of the circuit has vanished.

Soil Damping Does Not Make Every Radial Length Irrelevant

The guide treats ground-laid radials as non-resonant and makes their exact length irrelevant. A dense radial field can indeed be forgiving; that is not a blanket rule for four wires on a lawn.

Soil adds loss and changes electrical length. Sparse radial systems can still exhibit resonance-related loss and length sensitivity. In Rudy Severns, N6LF’s 7.2 MHz experiment, the change with ground-radial count was linked to resonances in sparse screens. He also warned against turning a result at one site into a universal prescription.

My practical distinction is simple: freedom from precise trimming is not freedom from adequate radial length and area. With a sparse system, investigate length, soil contact, routing and feedline interaction. With a denser field, small differences between individual wire lengths often matter less than the total return structure.

More Short Wires Are Not an Unlimited Substitute for Extent

WiMo’s short-versus-long rule favours numerous short conductors. Coverage near the feedpoint is valuable, but a radial field also needs useful physical extent.

For a fixed wire budget, count and length trade against one another. The appropriate balance depends on wavelength, soil and the antenna geometry. Cutting every radial very short to increase the count does not guarantee lower loss. Nor does a handful of exceptionally long wires automatically use the available copper well.

I would first use the space sensibly, provide a sound common connection, distribute the wires across the available ground and retain useful length on the lowest intended band. Then improve the parts of the return system still costing performance. That is a design direction; “length never matters” is not.

Height and Droop Are Design Variables, Not Magic Thresholds

The guide gives a one-to-two-metre elevation threshold and connects radial droop with a 50 Ω match and flat DX radiation.

One metre is a different electrical distance on 160 m and 2 m. Soil coupling changes continuously, not at a universal height marker. N6LF’s elevated-ground-system work examines the influence of asymmetry, radial count and nearby conductors. Fewer resonant radials can work well, but their layout and environment deserve more attention, not less.

Drooping radials can move a quarter-wave ground-plane feed resistance toward 50 Ω. That is a useful matching technique. It does not independently set the complete elevation pattern. Height, soil, radiator geometry, mast and feedline currents still shape the result. Choose droop for the installed design; do not treat the angle as a switch that sends every watt toward the horizon.

The Coax Velocity Factor Belongs to a Particular Mode

The guide places a choke using a quarter wavelength multiplied by the cable’s shortening factor. That is the wrong shortcut for an exterior-shield counterpoise.

The manufacturer’s usual coax velocity factor describes propagation between the centre conductor and the inner shield surface. The exterior current sees the jacket and the surrounding air, ground, mast and other conductors. Its electrical length is not automatically the same.

Tom Rauch, W8JI, explains why there is no universal feedline length that removes common-mode current: routing, grounding and surroundings change the circuit. A free-hanging special case does not become a general installation recipe.

A current probe around the complete cable responds to the non-cancelling current. Map several positions: one convenient minimum can sit beside a maximum. Use a calibrated transfer factor and check probe loading and frequency limits; the Rohde & Schwarz EZ-17 specifications illustrate those instrument requirements.

A Plastic Handheld Has Not Escaped the Other Conductor

The guide describes handheld antennas as typically half-wave or 5/8-wave dipoles overcoming the missing chassis ground. That is not a reliable general explanation.

Many handheld antennas are loaded monopoles or related compact structures. A plastic enclosure still contains a PCB ground, battery, shields and connectors. The operator and attached cables also change the coupled system. A genuinely balanced dipole is possible, but a product’s length label does not prove that topology.

Texas Instruments’ antenna guide, section 5.1.2, shows the effect of changing ground-plane size on match and pattern. The practical lesson for a handheld is to include the radio and its use position. If grip or a microphone cable changes performance, the “invisible” conductors are telling you something.

Capacitive Coupling Is Real; Its Impedance Is Not Zero

WiMo correctly identifies capacitive coupling in magnetic mounts, but describes its effectiveness too broadly.

Paint and a protective pad can form the dielectric between a mount and the car body. RF current can cross that capacitance without a DC metal-to-metal connection. The magnitude of capacitive reactance is |X_C| = 1/(2πfC): frequency and capacitance matter. Mount area, pad thickness, placement and vehicle geometry therefore matter too.

A mount that provides a satisfactory return at VHF is not thereby certified for a heavily loaded low-HF whip. The useful conclusion is to select the mount and coupling for the actual frequency and current—not to reject magnetic mounts, and not to assume insulation is electrically invisible.

A Match Is One Result, Not the Verdict

The guide links tuned radiator/radial harmony with maximum radiated power. Tuning alone cannot establish that result.

SWR describes reflection relative to the line impedance at a named plane. It does not separate radiation resistance from soil, conductor or matching loss. A lossy return system can make the feed impedance look convenient while wasting power. Conversely, an efficient antenna may need a matching network. Measure match to arrange power transfer; assess losses and the wanted pattern to decide what the antenna does with that power.

Keep elevated radial ends out of reach of people and animals. They can carry high RF voltage. WiMo’s warning is useful; equal voltage at every radial end and the vertical tip is not a universal identity. Current division, coupling and geometry decide the distribution. Ordinary insulation is not permission to touch an energised conductor.

The Explanation I Would Give a New Antenna Builder

• Build a deliberate, suitably low-loss return structure; do not substitute an earth rod for a radial field.
• Distinguish dense ground radials from sparse or elevated systems before choosing a length rule.
• Keep adequate extent as well as coverage near the feedpoint.
• Include the coax exterior, support and surrounding conductors whenever they carry current.
• Select the choke boundary for that current system, not from an unrelated velocity factor.
• Separate matching, efficiency, pattern and safety. Improving one does not automatically certify the others.

This is not a conclusion that antennas are too complicated to compare. It tells you what to improve: reduce avoidable loss in the return structure, remove uncontrolled feedline participation and choose a geometry that serves the intended path. Those changes have an engineering purpose beyond making the meter look happy.

Retailers can help the hobby enormously. My criticism of this guide is that its certainty sometimes outruns its explanation. Radials are not magic accessories, and polished wording is not a certificate of correctness. The real antenna is the complete current path. Teach that clearly and many of these myths lose their footing.

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