Section 4.4: Dipoles and Vertical Antennas #

You’re ready to get on the air with your new General privileges, but maybe a tower with a beam antenna isn’t in your immediate future. Good news—the vast majority of successful HF contacts happen with simple wire dipoles and vertical antennas. These workhorses of amateur radio have launched countless DX adventures and provided reliable communication for generations of hams. Understanding how to optimize these fundamental antennas will transform your HF experience from frustrating to fantastic.

Dipole Antennas: Your Gateway to HF Success #

Picture this: with just two pieces of wire and some coax, you can work stations on the other side of the world. That’s the magic of the dipole antenna—it transforms electrical energy into radio waves that bounce off the ionosphere and travel thousands of miles. The dipole works because it creates a resonant structure that efficiently radiates your signal into space.

The dipole’s effectiveness comes from its radiation pattern. Unlike a light bulb that shines equally in all directions, a dipole focuses its energy in specific directions.

Key Information: The radiation pattern of a dipole antenna in free space is a figure-eight at right angles to the antenna.

This figure-eight pattern means your signal radiates strongest broadside to the wire—perpendicular to its length. Orient your dipole so this maximum radiation heads toward your target areas, whether that’s Europe, Japan, or your favorite net control station.

Height Transforms Your Dipole’s Performance #

Here’s something that surprises many new General operators: the same dipole antenna can behave completely differently just by changing how high you hang it. Height doesn’t just affect signal strength—it fundamentally changes where your signal goes and how well your antenna matches your radio.

When you mount a dipole low (less than a half wavelength high), something interesting happens. The ground reflection changes your radiation pattern from that classic figure-eight into something more like a cloud overhead.

Key Information:

• If a horizontal dipole HF antenna is less than 1/2 wavelength high, its azimuthal radiation pattern is almost omnidirectional at elevation angles higher than about 45 degrees
• The feed point impedance of a horizontal 1/2 wave dipole antenna steadily decreases as its height is reduced to 1/10 wavelength above ground

This height effect creates two distinct operating modes. A low dipole sends most energy upward—perfect for NVIS (Near Vertical Incidence Skywave) work within a few hundred miles. Raise that same antenna above a half wavelength, and it transforms into a DX machine with a lower radiation angle. The impedance change from height also explains why your SWR might be different than expected—that theoretical 73-ohm dipole impedance assumes free space, not real-world installation heights.

Feed Point Magic: Controlling Impedance #

Want to match your antenna to different feed line impedances? The secret lies in where you connect your feed line. A dipole offers different impedances at different points along its length, giving you a natural impedance transformer.

Key Information: The feed point impedance of a 1/2 wave dipole steadily increases as the feed point is moved from the center toward the ends.

At the center, you get the familiar 73 ohms (in free space). Move toward the ends, and impedance climbs into the thousands of ohms. This principle powers several antenna designs, from the classic center-fed dipole that matches well to 50-ohm coax, to end-fed antennas that require special matching transformers to handle their high impedance.

Building Your Dipole: From Formula to Reality #

Converting your General privileges into on-air contacts starts with cutting your dipole to the right length. The magic number 468 gives you a quick way to calculate dipole length—it accounts for the “end effect” that makes practical antennas slightly shorter than theoretical half wavelengths.

Let’s see this formula in action for popular General class frequencies.

Key Information:

• The approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz is 33 feet
• The approximate length for a 1/2 wave dipole antenna cut for 3.550 MHz is 132 feet

These calculations give you starting points—expect to trim a few inches for perfect resonance. That 33-foot dipole for 20 meters fits in many suburban yards, while the 132-foot 80-meter dipole might require some creative installation techniques!

The Inverted V: One Support, Full HF Coverage #

Not everyone has two tall supports perfectly spaced for a flat dipole. Enter the inverted V—a clever solution that needs just one central support while maintaining excellent performance.

Key Information: The common name of a dipole with a single central support is an inverted V.

The inverted V design brings practical advantages beyond saving a support structure. Its sloping legs create a radiation pattern that blends horizontal and vertical characteristics, often providing more consistent coverage than a flat dipole. The downward angle also typically lowers the feed point impedance to around 50 ohms—a perfect match for your coax without any additional matching devices. Many hams find the inverted V becomes their go-to antenna because it performs well while fitting into real-world constraints.

End-Fed Antennas: Feed Line Freedom #

Sometimes your perfect antenna location puts the center right where you can’t reach it—over a pond, across a neighbor’s property, or high in a tree. End-fed half-wave (EFHW) antennas solve this dilemma by moving the feed point to one end, letting you keep your radio connection accessible while the antenna stretches to wherever it needs to go.

This convenience comes with a technical challenge. Remember how moving the feed point toward the ends increases impedance? At the very end, you’re dealing with extreme values.

Key Information: The feed point impedance of an end-fed half-wave antenna is very high.

We’re talking several thousand ohms—far from the 50 ohms your radio expects. Modern EFHW antennas solve this with impedance transformers (often called “ununs”) that convert these high impedances down to usable levels. The result? An antenna you can deploy from your shack window, feed at ground level, or string up in configurations impossible with center-fed designs.

Horizontal vs. Vertical: Choosing Your Polarization #

Every antenna decision involves trade-offs, and polarization is no exception. Your choice between horizontal and vertical polarization affects everything from DX performance to local noise levels. Understanding these differences helps you pick the right tool for your operating goals.

Horizontal antennas like dipoles offer a significant efficiency advantage for most amateur stations. The physics of how radio waves interact with the ground favors horizontal polarization.

Key Information: An advantage of using a horizontally polarized as compared to a vertically polarized HF antenna is lower ground losses.

Think of it this way: vertical antennas must push their signals through the ground to create their radiation pattern, losing energy in the process. Horizontal antennas interact with the ground differently, reflecting signals with less loss. This efficiency advantage is especially pronounced over typical suburban soil. However, verticals shine in other ways—they’re compact, don’t need tall supports, and can provide excellent low-angle radiation for DX when properly installed.

Vertical Antennas: Your Window to the World #

When horizontal space is at a premium but you still want to work DX, vertical antennas become your best friend. A vertical takes up no more ground space than its base, reaches straight up into the sky, and can deliver surprisingly strong signals to distant stations. The secret lies in their unique radiation characteristics and simple installation requirements.

The vertical’s superpower is its omnidirectional coverage. Unlike beams that must be rotated or dipoles that favor certain directions, verticals hear and transmit equally in all directions.

Key Information: The radiation pattern of a quarter-wave ground-plane vertical antenna is omnidirectional in azimuth.

This 360-degree coverage means you’ll never miss a rare DX station calling from an unexpected direction. It also makes verticals perfect for nets, emergency communications, or any time you need to maintain awareness in all directions. The trade-off? You can’t focus your signal like a beam antenna, but many operators find the convenience of omnidirectional coverage outweighs the lack of gain.

The Secret to Vertical Success: Radials #

Here’s what many new General operators don’t realize: a vertical antenna is only half the story. The other half—the part that makes or breaks your signal—is the ground plane system. Think of radials as the other half of your antenna, providing the “mirror” that allows your vertical to radiate efficiently.

For ground-mounted verticals, proper radial installation makes the difference between a mediocre antenna and a DX powerhouse.

Key Information: The radial wires of a ground-mounted vertical antenna system should be placed on the surface or buried a few inches below the ground.

The radial system acts like a shield, preventing your precious RF energy from being absorbed by lossy ground. More radials mean better shielding and stronger signals. While perfection might require 120 radials, don’t let that discourage you—even four radials provide noticeable improvement over none, and 16-32 radials achieve most of the possible gain. For elevated verticals, you need fewer radials (typically 2-4) since they’re not fighting ground losses directly.

Fine-Tuning Your Vertical’s Match #

A quarter-wave vertical naturally presents about 36 ohms impedance—close to 50 ohms but not quite perfect. This small mismatch usually works fine, but for optimum performance, you can adjust the impedance using a clever trick involving your radial system.

The angle of your radials controls more than just the ground plane—it also affects feed point impedance. By tilting the radials, you change how the antenna “sees” its environment.

Key Information: To adjust the feed point impedance of an elevated quarter-wave ground-plane vertical antenna to be approximately 50 ohms, slope the radials downward.

Angling radials downward at about 45 degrees raises the feed point impedance from 36 ohms to nearly 50 ohms—a perfect match for your coax. This technique works especially well with elevated verticals where you have full control over radial positioning. It’s one of those elegant solutions that uses antenna geometry to solve an impedance problem without any additional components.

Sizing Your Vertical for Success #

Building a vertical starts with getting the length right. Since a vertical is essentially half of a dipole (the other half being its image in the ground plane), we use half the magic number: 234 instead of 468.

Let’s calculate a practical example for 10 meters.

Key Information: The approximate length for a 1/4 wave monopole antenna cut for 28.5 MHz is 8 feet.

That’s remarkably manageable—an 8-foot vertical for 10 meters fits almost anywhere! This compact size makes verticals especially attractive on higher bands where even modest heights achieve excellent low-angle radiation for DX work.

Random Wire Antennas: The Compromise That Works #

Life doesn’t always provide perfect antenna situations. Maybe you’re in an HOA-restricted neighborhood, renting, or just need something temporary. Random wire antennas—essentially any wire that isn’t cut to a specific resonant length—offer a path to get on the air when conventional antennas aren’t possible.

Random wires come with a unique challenge that catches many operators off guard. When you connect a non-resonant wire directly to your equipment, the antenna system becomes unbalanced.

Key Information: A characteristic of a random-wire HF antenna connected directly to the transmitter is that station equipment may carry significant RF current.

This RF in the shack can cause everything from “hot” microphones to computer interference. The solution involves creating a complete antenna system: use an antenna tuner to achieve a match, add a counterpoise wire to provide a return path for RF currents, and consider an unun (unbalanced-to-unbalanced transformer) at the feed point. With these additions, a simple random wire can provide surprisingly good performance across multiple bands.

NVIS: Your Regional Communication Powerhouse #

Sometimes DX isn’t the goal. When disasters strike, during emergency nets, or for reliable statewide coverage, you need signals that blanket your region without skipping over nearby stations. Near Vertical Incidence Skywave (NVIS) turns conventional antenna wisdom upside down—literally—by sending signals straight up to rain back down across hundreds of miles.

NVIS works by deliberately creating a high-angle radiation pattern. Instead of fighting to get your antenna higher for DX, you optimize for regional coverage.

Key Information: A horizontal dipole antenna most effective as a Near Vertical Incidence Skywave (NVIS) antenna for short-skip communications on 40 meters during the day is one placed between 1/10 and 1/4 wavelength above the ground.

For 40 meters, this means mounting your dipole just 13-33 feet high—easily achievable heights that would horrify DXers but create perfect regional coverage. The low height causes your signal to launch nearly straight up, reflect off the ionosphere, and return in an umbrella pattern that covers everything from your QTH out to about 300 miles. Mountains, valleys, and terrain obstacles become irrelevant when your signal arrives from above. This makes NVIS invaluable for emergency communications, regional nets, and any time you need consistent coverage of your state or surrounding area.

Practical Antenna Solutions #

Your General privileges span nine HF bands, but that doesn’t mean you need nine antennas. Multiband designs like trap dipoles, fan dipoles, and end-fed antennas can cover multiple bands from a single feed point. Open-wire fed dipoles with a tuner offer perhaps the most flexibility—one antenna for all bands—at the cost of dealing with ladder line routing.

Limited space? Physics is your friend on higher bands where antennas shrink dramatically. That same dipole that needs 132 feet on 80 meters fits in 16 feet on 10 meters. Magnetic loops, loaded antennas, and even attic installations can get you on the air when outdoor space is restricted. The key principle: any antenna beats no antenna.

A few hard-won installation tips: Height helps more than anything else. Baluns aren’t optional—they prevent feed line radiation and RFI. Water infiltration kills connections faster than anything, so weatherproof everything.

Remember, even modest antennas work DX when conditions cooperate. Focus on getting something in the air, then improve it over time. Your first antenna won’t be your last, but it will be the one that gets you started.

Your Antenna Journey Begins #

The dipoles and verticals we’ve explored form the foundation of most amateur stations. These fundamental antennas deliver real results—whether you’re working DX with a simple dipole at 30 feet or using an NVIS configuration for regional emergency nets. Master these basics and you’ll understand principles that apply to every antenna you’ll ever use.

What happens when your radio adventures take you beyond the shack? Your General privileges aren’t limited to fixed stations. The real magic happens when you take amateur radio on the road—working HF mobile during your commute or setting up portable in that perfect hilltop park. The challenge is making effective antennas that fit these constraints while still getting out. Next, we’ll explore how clever engineering solves the seemingly impossible problem of fitting HF antennas on vehicles and in backpacks.