Half-Wave Verticals: Why No Radials Needed and How to Build One

Most vertical antenna guides start with the same warning: you need radials. Lots of them. Lay down 60 quarter-wave wires and pray your neighbors don't notice. But half-wave verticals sidestep that entire headache, and understanding why they work without a ground plane makes you a better antenna builder.

This guide covers the physics, the practical design trade-offs, and a full build walkthrough for a 20-meter half-wave vertical that'll get you on the air without burying copper in your yard.

Why Quarter-Wave Verticals Need Radials (Quick Refresher)

A quarter-wave vertical is literally half an antenna. The radiating element is 1/4 wavelength tall, and the ground system — radials, ground screen, or the earth itself — acts as a mirror to create the "missing" half. Without adequate radials, current has nowhere to return efficiently. You get high ground losses, lousy efficiency, and a radiation pattern that's more like a flashlight pointed at the dirt.

The standard recommendation from the ARRL Antenna Book is 60 radials at 0.2λ or longer. That's roughly 10,000 feet of wire for a 20-meter band installation. Not exactly apartment-friendly.

The Half-Wave Difference: Complete Antenna, No Mirror Needed

A half-wave vertical is a complete radiating system. Both halves of the current distribution exist on the element itself — current is maximum at the center and drops to zero at both ends. There's no "missing half" that needs a ground image to complete.

Here's the thing. A half-wave antenna has high impedance at its feed point when end-fed (around 2000-5000 ohms depending on height and surroundings). The current minimum is at the base, which means minimal current flows into whatever's below the antenna. Minimal current at the ground connection means minimal ground loss.

That's the entire secret. Not magic. Just physics.

Compare this to a quarter-wave vertical where maximum current occurs right at the base, flowing directly into (and being lost in) whatever ground system you've provided.

Real-World Performance Without Radials

I built my first half-wave vertical for 20 meters back in 2019, mounted on a 10-foot mast clamped to my deck railing. No radials. No ground rods connected to the antenna. I was skeptical — years of reading about radial systems had me convinced I was wasting my time.

First evening on FT8, I logged 23 contacts across Europe and South America from my QTH in Virginia. Not earth-shattering DX, but from a stick on a deck with zero ground system? I was sold.

Now, "no radials needed" doesn't mean "immune to ground effects." The antenna still benefits from being away from lossy surfaces. Height matters. Getting the base at least 8-10 feet off the ground noticeably improves low-angle radiation. But you're not losing 3-6 dB to a crappy radial system, which is the typical penalty for a quarter-wave vertical with only 4-8 radials.

Design Options: J-Pole vs. End-Fed Half-Wave

Two main approaches exist for building a half-wave vertical without radials:

J-Pole (end-fed via matching stub)

The J-pole uses a quarter-wave matching section at the bottom — essentially a shorted transmission line stub that transforms the high impedance at the element's end down to 50 ohms. Total length is about 3/4 wavelength. It's elegant, single-band, and tunes by sliding the feed tap point.

End-Fed Half-Wave with transformer (EFHW)

This uses a 49:1 (or 64:1) impedance transformer at the base to match the high feed impedance directly to 50-ohm coax. More compact than a J-pole and the transformer can be wound to cover multiple bands if you accept some compromise.

I'll get hate for this, but: the J-pole is overrated for most HF operators. It works great on 2m/70cm where total antenna length is manageable, but on HF bands, that extra quarter-wave stub adds significant length and mechanical complexity. A well-built EFHW transformer gives you more flexibility for roughly the same performance.

Step-by-Step: 20-Meter EFHW Vertical Build

Materials

• 33.6 feet of #14 AWG stranded copper wire (or aluminum for weight savings)
• FT-140-43 ferrite toroid (or two stacked FT-114-43)
• 150 pF capacitor rated 1kV or higher (across secondary — optional, aids SWR)
• 50-ohm coax connector (SO-239)
• Weatherproof enclosure for transformer
• Support mast: fiberglass pushup pole, 33+ feet (Spiderbeam or Jackite)

Transformer Winding

The 49:1 unun (unbalanced-to-unbalanced transformer) is the heart of this antenna.

On the FT-140-43 toroid:

• Primary: 2 turns of #18 AWG enamel wire
• Secondary: 14 turns of #18 AWG enamel wire
• Wind in the same direction, connect the end of the primary to the start of the secondary

Turns ratio is 7:1, which gives impedance ratio of 49:1. That transforms 2450 ohms down to 50 ohms. Close enough for most real-world half-wave installations.

Some builders add a 150 pF capacitor across the secondary winding. This compensates for stray capacitance and sharpens the SWR dip. Not strictly necessary but it helps get below 1.5:1 across more of the band.

Wire Length Calculation

For a half-wave on 20 meters (14.1 MHz center):

λ/2 = 468 / f(MHz) = 468 / 14.1 = 33.19 feet

Start at 33.6 feet and trim. Seriously. Always cut long and trim short. You can't add wire back.

The velocity factor of bare wire in free space is essentially 1.0, but end effects and proximity to supports will lower resonance slightly. Expect to trim 2-4 inches for a clean SWR minimum at your target frequency.

Assembly

1. Wind the transformer and test with an antenna analyzer before sealing. You want to see roughly 50 ohms resistive across your target frequency range with a dummy load on the secondary. Use a 2.4K resistor across the secondary — you should read close to 50 ohms on the primary.

2. Solder the wire element to the secondary high-impedance side of the transformer.

3. Connect a short ground lead from the transformer input ground to the coax shield. This isn't a radial — it's just completing the unbalanced circuit. A 6-inch pigtail is fine. Some builders add a single counterpoise wire of about 0.05λ (roughly 3.5 feet for 20m). This can improve SWR stability but isn't mandatory.

4. Mount the transformer enclosure at the base of your mast. Run the wire straight up, secured to the fiberglass pole with cable ties every 3-4 feet.

5. Attach coax and route it away from the antenna at 90 degrees if possible.

Tuning

With an antenna analyzer (NanoVNA works perfectly here):

• Sweep 13.5-14.5 MHz
• Find the SWR minimum
• If it's below 14.0 MHz, trim 1 inch at a time from the top
• If it's above 14.35 MHz, you've trimmed too much (this is why we start long)

Target: SWR below 1.5:1 across the phone portion (14.15-14.35 MHz) with SWR below 2:1 across the full band.

Common Mistakes

• Running coax parallel to the antenna: This couples common-mode current onto the shield, which effectively becomes a radial (or worse, part of the radiator). Use a choke at the feedpoint. Seriously.
• Mounting too low: With the base at ground level, you're basically making a ground-mounted vertical with terrible efficiency. Get the base up. Even 6 feet helps.
• Wrong ferrite material: Fair-Rite Type 43 material is correct for HF (1-30 MHz). Type 31 works for lower HF/MF. Don't use Type 61 — it's for RF suppression above VHF, not power transformers at HF.
• Insufficient turns: If you see transformer core heating at 100W, you need more turns or a bigger core (step up to FT-240-43). The core must not saturate.

Performance Expectations

A properly built half-wave vertical for 20m, with the base 8-10 feet above ground and the tip at 42+ feet, will give you:

• Roughly 0.5-1.5 dBi gain at low elevation angles (good for DX)
• Omnidirectional pattern
• Bandwidth of 200-300 kHz at 2:1 SWR
• Handles 200W SSB comfortably with FT-140-43 core (for higher power, use FT-240-43)

Not bad for $30 in parts and an afternoon.

Wrapping Up

Half-wave verticals aren't mysterious. They work because they're complete antenna systems that don't rely on ground image currents. Skip the radial field, wind a transformer, hang some wire, and get on the air. The performance-to-effort ratio is about as good as it gets in amateur radio.

Your next step: grab an FT-140-43 toroid and some magnet wire. The transformer takes 20 minutes to wind and test. The rest is just hanging wire.