Inverted-V Antennas: The Practical Compromise That Actually Works

The inverted-V is probably the most-built HF antenna in amateur radio, and for good reason. One support point in the center, two wires sloping down to stakes or tie-off points near the ground. No tower, no rotator, no elaborate rigging. And it actually works well enough to hold a conversation with someone three thousand miles away.

But there's a gap between "I threw up an inverted-V" and "I built an inverted-V that's optimized for my situation." The angle between the legs, the apex height, the feedpoint impedance, and the ground interaction all change performance in ways that matter. Let's dig into what's really going on with this antenna.

What Makes an Inverted-V Different from a Flat Dipole

An inverted-V is a half-wave dipole with the center raised and the ends drooping. Geometrically simple. Electrically, the drooping changes several things:

Radiation pattern: A flat dipole at half-wavelength height produces a figure-8 pattern broadside to the wire, with nulls off the ends. An inverted-V fills in those end nulls because the drooping elements radiate partially downward and in more directions. The result is closer to omnidirectional on the horizon. Less gain in any single direction, but coverage in more directions.

For HF work where propagation paths shift constantly, this is usually what you want. You're not pointing a beam — you're trying to hear and be heard from everywhere.

Feedpoint impedance: A flat half-wave dipole in free space presents about 73 ohms at the feedpoint. An inverted-V with a typical 90-degree included angle between the legs drops that to around 50 ohms. Look at that — nature gives you a near-perfect match to 50-ohm coax without a matching network.

This isn't coincidence. It's why the inverted-V became so popular. The impedance naturally falls right where you want it.

Bandwidth: Slightly narrower than a flat dipole because the effective height of the radiating elements is lower. But we're talking about a small difference in practice — maybe 50-100 kHz less 2:1 SWR bandwidth on 40 meters compared to a full-height flat dipole.

Dimensions: Getting the Length Right

The standard half-wave dipole formula:

Length (feet) = 468 / frequency (MHz)

This gives total length for both legs. Each leg is half of that.

For common HF bands:

Band Center Freq Total Length Each Leg 80m 3.75 MHz 124.8 ft 62.4 ft 40m 7.15 MHz 65.5 ft 32.7 ft 20m 14.175 MHz 33.0 ft 16.5 ft 15m 21.225 MHz 22.0 ft 11.0 ft 10m 28.4 MHz 16.5 ft 8.2 ft

But here's the thing everyone forgets: the inverted-V configuration makes the antenna electrically shorter because the drooping ends are closer to ground and the current distribution changes slightly. In practice, you need about 3-5% more wire than the formula suggests.

So for 40 meters: 65.5 feet × 1.03 = 67.5 feet is a better starting point. Cut long, trim to resonance.

The velocity factor of your wire matters too. Bare copper wire is close to 1.0. Insulated wire (like THHN from the hardware store) has a velocity factor around 0.95-0.97, which makes the antenna physically shorter for the same electrical length. If you're using insulated wire, the standard 468/f formula usually works without the additional 3-5% because the insulation effect and the inverted-V effect roughly cancel.

I spent an afternoon with an antenna analyzer proving this to myself after reading conflicting advice on QRZ forums. Built two 40m inverted-Vs side by side: one bare 14 AWG copper, one 14 AWG THHN. The bare wire needed 67 feet total to resonate at 7.15 MHz. The THHN version resonated at 65.2 feet. Both with 90-degree included angle, same 33-foot apex height. The difference tracked almost exactly with the THHN's velocity factor.

Apex Height: How High Is Enough?

Ideal apex height for a half-wave inverted-V is one-half wavelength above ground. For 40 meters, that's about 66 feet. For 20 meters, roughly 33 feet.

Reality check: most of us aren't putting up 66-foot masts for a wire antenna. So what actually happens at lower heights?

Quarter-wave apex height (33 feet for 40m): Works fine. Radiation angle increases slightly (your signal goes more upward), which is actually helpful for shorter-distance contacts within 500-1500 miles. You lose some DX capability compared to the ideal height, but not dramatically.

Low apex (20-25 feet for 40m): Usable but compromised. The antenna becomes more of a cloud-warmer — lots of high-angle radiation good for Near Vertical Incidence Skywave (NVIS) contacts out to about 300 miles. Long-distance DX performance drops significantly.

For most operators working the continental US on 40 or 80 meters, an apex height of 30-40 feet gives excellent results for the distances that matter. You don't need the theoretical ideal.

On 20 meters where the half-wavelength is only 33 feet, getting the apex to that height is very achievable. A single push-up mast or a tree branch at that height gives you a great performing 20m inverted-V.

The Included Angle: Don't Go Below 90 Degrees

The angle between the two legs (measured at the apex) is the included angle. A flat dipole has a 180-degree included angle. As you droop the legs more, this angle decreases.

• 120 degrees: Feedpoint impedance around 60 ohms. Pattern still fairly close to a flat dipole. Gentle droop.
• 90 degrees: Feedpoint impedance around 50 ohms. Good match to coax. More omnidirectional. This is the sweet spot.
• 60 degrees: Feedpoint impedance drops to 35-40 ohms. Legs are steep. Performance starts degrading because the ends are very close to ground and contribute less to radiation.

Going below 90 degrees isn't worth it. You lose efficiency, the impedance mismatch increases, and the legs are so low that they interact with ground in unfavorable ways.

Practical translation: if your apex is 33 feet and you want a 90-degree included angle, your leg endpoints should be about 33 feet horizontally from the center (measured along the ground). The legs make 45-degree angles with the vertical mast. At that angle, end height above ground is roughly 0 feet — meaning the wire tips are at or near ground level.

That's actually fine. Stake the wire ends a couple feet off the ground and you're close to that 90-degree angle.

Construction Details That Matter

Wire

14 AWG stranded copper works well. It's strong enough to support its own weight over the spans involved, flexible for easy deployment, and cheap. Hardware store THHN wire is fine — about $30 for 250 feet.

Avoid solid wire for portable use. It work-hardens and breaks at stress points. For permanent installations, solid wire is fine because it doesn't move.

For portable/field use, consider 18 AWG stranded speaker wire (separate the two conductors). Lighter weight, packs smaller, but don't use it for permanent installations where ice and wind loading matter.

Center Insulator and Feedpoint

You can buy a commercial center insulator with an SO-239 connector for $10-15. Or build one from a piece of plexiglass or cutting board. The goal: mechanically support the coax weight, connect the coax center conductor to one leg and the shield to the other, and keep the connection weatherproof.

A 1:1 choke balun at the feedpoint is recommended. Without it, common-mode current flows on the outside of the coax shield, distorting the pattern and potentially causing RFI in your shack. Wind 10-12 turns of your coax through an FT-240-31 ferrite toroid at the feedpoint. That's your balun. Cost: about $12 for the toroid.

Big mistake: skipping the balun. I ran my first inverted-V without one for six months. S7 noise floor in the shack. Computer hash on every band. Added the choke balun, noise dropped to S3. Six months of operating with unnecessary noise because I was lazy.

End Insulators and Tensioning

Dog-bone style ceramic or plastic end insulators ($2-3 each) work fine. Tie the wire through the insulator, then run a nylon cord from the insulator to your stake or tie-off point. The nylon cord acts as a strain relief and allows you to adjust tension without cutting wire.

Don't over-tension. The wire should have slight sag. Over-tensioned wire breaks in wind gusts or when ice loads it. Let it flex.

The Mast

For portable/field ops: a 31-foot Jackite fiberglass pole ($100) or a budget crappie pole from Amazon ($30-50) telescopes up and collapses for transport. Drive the base into soft ground with a ground stake, or use a drive-on mount plate.

For permanent installations: treated 4×4 lumber, aluminum EMT conduit (available at hardware stores in 10-foot sections — couple them together), or a surplus military mast section. A push-up TV mast also works and can be guyed at the top.

Here's something that catches people: the mast material matters if it's conductive. An aluminum mast at the center of your inverted-V sits right at the feedpoint where voltage is low and current is maximum. If the mast is within a few inches of the wire, it can couple and detune the antenna. Keep the wire at least 6-12 inches away from a metal mast, or use non-conductive material for the top section.

Multiband Inverted-V Options

A single inverted-V is a monoband antenna. Want multiple bands? Three options:

Fan dipole: Multiple pairs of legs from the same feedpoint, each cut for a different band. 40m legs and 20m legs from the same center insulator. Spread the legs apart slightly (12-18 inches separation) to reduce interaction. Works well for 2-3 bands. More than that gets mechanically complex.

Trap dipole: Parallel LC traps in each leg that electrically shorten the antenna on higher bands. Commercially available (Hustler, MFJ), or buildable. Traps add loss — typically 0.5-1 dB per trap. And they limit bandwidth. But it's one feedline and one antenna.

Linked dipole: Alligator clips or Anderson Powerpoles at calculated points on each leg. Unclip to shorten for higher bands. No loss, full bandwidth, but you have to physically change the configuration to change bands. Popular for SOTA/POTA where you pick a band and stick with it.

Tuning and Adjustment

With an antenna analyzer (NanoVNA, RigExpert, or similar):

1. Cut the legs 5% long
2. Raise the antenna to operating position
3. Measure SWR at your target frequency
4. If resonant frequency is too low (SWR dip below your target), trim equal amounts from each leg — 1 inch at a time on 20m, 3-4 inches at a time on 40m
5. If resonant frequency is too high, you cut too short. Add wire (or start over)

Always measure with the antenna at its final height. Lowering it to trim and then raising it again shifts the resonant frequency. This feels tedious, but it only takes 3-4 iterations to nail it.

Worthwhile: once tuned, record the exact wire lengths, the apex height, and the resonant frequency. If you take it down and put it back up at the same dimensions, it'll resonate in the same place.

Performance Reality Check

An inverted-V at a reasonable height won't beat a Yagi. It won't outperform a full-size vertical with an extensive radial field. It's a compromise antenna.

But it's a compromise that gets you on the air for under $50 in materials, requires one support point, goes up in 30 minutes, and works every band from 80 through 10 meters (with the right configuration). For most operators, that's exactly the right trade-off.

I've worked all 50 states, over 100 DXCC entities, and dozens of POTA activations on inverted-V antennas. Not because they're the best antenna, but because they're the antenna I actually build and use. The best antenna is the one that's in the air.