Build a 10m Half-Wave Dipole Antenna
The 10m half-wave dipole is the shortest, cheapest, fastest-to-build HF dipole on this site — at 28.4 MHz the whole antenna is barely 16.5 feet long, short enough to fit in a small yard or even mount indoors. What 10m lacks in year-round reliability it makes up for with genuinely exciting propagation: during solar maximum the band opens for worldwide F2-layer DX, and even at solar minimum, summer sporadic-E openings deliver strong, short-skip contacts on a band most stations leave quiet. This guide covers the complete build from wire cutting to verified resonance.
Choose Your Target Frequency
The 10m band spans 28.000 to 29.700 MHz — at 1.7 MHz wide, it is by far the widest HF band a dipole on this site covers, both in absolute terms and as a percentage of center frequency. That width means a dipole cut for one part of the band shows meaningfully higher SWR at the opposite end than the same cut would on a narrower band like 20m:
- CW and digital (FT8 at 28.074): 28.000–28.300 MHz — cut for 28.150 MHz
- Novice/Technician phone segment: 28.300–28.500 MHz — cut for 28.400 MHz
- General phone and DX: 28.500–29.300 MHz — cut for 28.900 MHz
- Best all-around compromise: 28.400 MHz — covers CW and both phone segments with a tuner at the extremes
Because 28.400 MHz sits near the low-middle of a very wide band, a dipole cut here still shows a rising SWR curve toward 29.700 MHz. If your operating interest is entirely in the upper phone segment, cut for 28.900 MHz instead rather than accepting the compromise.
Choose Your Configuration
At 16.5 feet total length, a 10m dipole is small enough that the usual configuration tradeoffs matter less than on lower bands — almost any support arrangement works:
- Flat (horizontal) — full performance, needs only about 8.5 feet of clearance per side. Trivially easy to fit even on a small lot or balcony.
- Inverted-V — a single 15–20 foot mast handles the whole antenna comfortably. The most common choice given how little support height 10m actually needs.
- Vertical dipole — mounted on a single non-metallic mast with the feedpoint at the bottom, giving a low-angle, roughly omnidirectional pattern useful for DX when a horizontal run isn't practical.
- Attic or indoor — the short overall length makes 10m one of the easiest HF bands to fit entirely inside an attic or even a large room, though nearby framing and wiring will detune it somewhat more than on lower bands relative to the wire's own length.
Because the whole antenna is so short, height above ground matters even more in relative terms than on 20m or 40m — a 10m dipole at 20 feet is already at half a wavelength, a genuinely useful height for DX.
10m Dipole Calculator
Everything you need to build a complete 10m dipole
Building the 10m Half-Wave Dipole
Follow these steps in order. The short wire length makes this one of the fastest dipole builds on this site.
Mark Out and Cut the Wire
Unroll the wire on a flat surface. Measure 8.5 feet from one end and mark with tape. Cut at this mark — this is your first leg, 3% longer than the calculated 8.24-foot resonant length to leave trimming room. Cut a second identical 8.5-foot leg.
Wind the Current Choke
Wind 7 turns of RG-8X coax through the FT-240-31 toroid — one turn less than the lower-band guides on this site, since choke impedance requirements scale down somewhat at 28 MHz, though 8 turns also works fine and gives more margin. Push the coax through the toroid hole, loop around the outside, and back through again for each turn.
Prepare the Coax End
Strip back 2 inches of outer jacket at the antenna end of the coax. Fold the braid back over the jacket without nicking strands. Strip 1 inch of dielectric to expose the center conductor. Tin both the center conductor and folded braid with solder.
Assemble the Feedpoint
If using a commercial dipole center, follow its instructions. If fabricating your own from PVC pipe or a small project box, drill two pairs of holes for 6-32 screws — one screw per side connects to the coax (center conductor to one side, braid to the other), the second screw on each side connects the antenna wire.
Strip 1.5 inches of insulation from each wire leg end, form a loop with round-nose pliers, and secure it under a screw and lock washer before soldering for electrical continuity.
Attach End Insulators and Support Rope
Thread each wire leg through an egg insulator at the far end. Double the wire back about 3 inches, wrap 4–5 times around the main wire, and solder the wrap. Attach at least 18 inches of Dacron rope to each insulator — this rope gap keeps the wire's electrical length clear of the support material.
Plan the Installation Layout
Walk the site and confirm your support points. For an inverted-V at 28.4 MHz, a center support of 15–20 feet already puts the antenna at half a wavelength or better — genuinely useful DX height on this band. Wire ends only need to clear 6 feet above ground. Route the coax to the shack before raising and leave a 12-inch drip loop just below the feedpoint.
Raise the Antenna
For an inverted-V, raise the center mast first with the feedpoint attached at the top, then pull each leg out to its end anchor and secure with modest tension. For a flat dipole, raise the center and one end, then the second end, adjusting tension until level.
Initial SWR Sweep
Connect the NanoVNA at the radio end of the coax and sweep 27.5 to 30.0 MHz. With legs cut to 8.5 feet, expect resonance around 27.7–28.0 MHz — slightly below target due to the long legs.
Trim to Target Frequency
Each 1 inch trimmed from both legs raises resonance by roughly 25–30 kHz on 10m — a noticeably bigger shift per inch than on lower bands because the wire is such a large fraction of the total wavelength.
Trim both legs equally in 3–4 inch increments and re-measure after each cut, switching to 1-inch increments as you approach the target.
Verify Across the Band
Once resonance is confirmed, sweep the full 28.000–29.700 MHz range. Because the band is so wide, expect SWR to rise noticeably at the far end (29.700 MHz) even with a good center-band cut:
- SWR at 28.000 MHz: 1.3–1.8:1
- SWR at 28.400 MHz: 1.1–1.4:1 (the resonance minimum)
- SWR at 29.700 MHz: 2.5–4:1 (expected — use a tuner this far from center)
Weatherproof the Feedpoint
Wrap self-amalgamating tape upward from below the feedpoint with 50% overlap, covering all connections and the coax entry. Apply a second layer of PVC electrical tape over it for UV protection.
Document and Make First Contact
Record the final leg lengths, installed height, and resonant frequency in your station log. Tune to 28.400 MHz and call CQ — 10m rewards patience over a solar cycle, so log every contact to track how conditions change over time.
Solar-Cycle-Dependent Propagation
10m is the most solar-cycle-sensitive HF band most hams regularly use. Near solar maximum, F2-layer propagation opens the band for worldwide DX for hours at a time, often with strong signals on very modest power. Near solar minimum, F2 openings become rare, but the band is far from dead — it simply shifts to relying on other propagation modes.
Sporadic-E — The Summer Bonus
Sporadic-E (E-skip) openings occur on 10m independent of the solar cycle, concentrated in late spring through summer. These openings produce strong, short-to-medium-skip signals (typically 500–1400 miles) that can appear even during the deepest part of a solar minimum, when F2 propagation is essentially absent. A dipole at even modest height works E-skip openings well — this is one of the few DX-capable propagation modes on HF that doesn't require chasing the solar cycle.
Why Height Matters More in Relative Terms Here
Because the 10m wavelength is so short, a modest physical height represents a large fraction of a wavelength compared to the same height on 40m or 80m. A 10m dipole at 20 feet is already above half a wavelength high — genuinely useful for low-angle DX. This is one reason 10m dipoles perform disproportionately well relative to their simplicity: the antenna doesn't need a tall tower to get a good takeoff angle the way a 40m or 80m dipole does.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| SWR high (3:1+) across entire band | Connection or wiring error | Inspect all feedpoint connections | Verify center conductor and braid are on opposite dipole sides; check for open connections |
| SWR changes when touching the coax | Common-mode current; no choke | Is the current choke installed? | Install or improve the current choke; add snap-on ferrite near the feedpoint |
| Resonance too low (below 28.000 MHz) | Wire legs too long | Measure actual leg lengths | Trim both legs equally — 1 inch per side raises resonance ~25 kHz |
| Resonance too high (above 29.700 MHz) | Wire legs too short | Measure actual leg lengths | Splice a short wire extension onto each leg end and re-tune |
| SWR fine but no signal reports during a known F2 opening | Antenna too low, or wrong operating window | Check propagation reports for the current solar flux and check your antenna's height in wavelengths | Raise the antenna if possible; monitor DX cluster spots to confirm the band is actually open |
| Band seems "dead" for weeks at a time | Normal low-solar-activity behavior on 10m | Check current solar flux index and sunspot number | Not a fault — try summer mornings/afternoons for sporadic-E instead of chasing F2 DX |
Is 10m worth building an antenna for right now?
Yes, regardless of where you are in the solar cycle. During high solar activity, 10m is one of the most productive DX bands available. During low activity, sporadic-E openings in late spring and summer still deliver strong regional and medium-distance contacts. The antenna itself is so cheap and quick to build that there's little reason not to have one up and ready for whenever the band opens.
Do I really need a current choke on a 10m dipole?
Yes — for the same reasons as on any other band. Without a choke, common-mode current on the coax distorts the pattern and makes SWR readings unreliable. A 7-turn FT-240-31 choke at the feedpoint is inexpensive and effective at 28 MHz.
Why is the SWR so much worse at the top of the band than on 20m?
The 10m band is 1.7 MHz wide — roughly 6% of its center frequency, compared to 20m's 350 kHz being about 2.5% of its center frequency. A dipole cut for the center of such a wide band will always show more SWR variation edge-to-edge than the same design on a proportionally narrower band. This is expected behavior, not a fault in the build.
What wire gauge should I use?
#14 AWG stranded copper-clad steel works well and is consistent with the rest of this site's dipole guides. Because the wire is so short and lightweight on 10m, even lighter #18–20 AWG wire is a fully viable option if you want to minimize visual impact or weight, particularly for a portable or attic build.
Can I use a 10m dipole on other bands?
Not usefully without a tuner — a 10m dipole is electrically too short on every lower HF band, and its harmonic relationships don't line up usefully with other ham bands the way a 40m dipole's harmonics reach 15m. Treat this as a dedicated single-band antenna, or add a second dipole on a different band fed with its own feedline if you want multi-band coverage from the same support.
How do I know if the band is actually open?
Check a DX cluster or the Reverse Beacon Network for recent 10m spots, and check current solar flux and sunspot numbers from a space weather site. Beacons in the 10m beacon sub-band (28.190–28.300 MHz) are another reliable way to confirm propagation to a specific direction before calling CQ.