Build a 5-Element Yagi Antenna
The 5-element Yagi represents the point at which a Yagi antenna crosses from good to exceptional — forward gain of 9–11 dBd, front-to-back ratio exceeding 25 dB, and a beamwidth narrow enough to make azimuthal accuracy matter in pile-up operation. Two directors in front of the driven element, each progressively shorter and spaced for maximum forward gain, produce a beam that consistently outperforms any smaller Yagi on a band-by-band comparison. A 20m 5-element Yagi on a 40-foot boom is a contest-grade antenna that requires a real tower and heavy-duty rotator — this guide covers the design, element spacing optimization, the T-match feed system, mechanical assembly, and the verification process for a high-performance 5-element Yagi.
Element Arrangement and Roles
The 5-element Yagi extends the 3-element design by adding two director elements in front of the driven element. Each successive director is shorter than the previous and spaced to maintain constructive addition of forward-radiated energy:
W2PV / OWA 5-Element Design Dimensions
This guide uses the Optimum Working Antenna (OWA) 5-element design, which produces excellent gain across the full 20m band by sacrificing a small amount of peak gain for improved bandwidth and a more consistent SWR curve:
OWA vs Classic Design — Why This Matters
The OWA (Optimum Working Antenna) design philosophy, developed by John Lawson W2PV, differs from the classic Yagi design approach in a fundamental way that makes it far more practical for homebuilders:
- Classic design: maximizes forward gain at a single frequency. SWR rises sharply away from the design frequency, requiring an ATU or careful re-tuning to cover the full band.
- OWA design: sacrifices approximately 0.5 dB of peak gain to achieve SWR below 1.5:1 across the entire target band without a tuner. The SWR curve is broad and flat — a true no-tuner full-band antenna.
- 50 Ω direct feed: the OWA design produces approximately 50 Ω feedpoint impedance, allowing direct coax connection with only a current choke — no gamma match, beta match, or balun required. This is the single largest practical simplification over classic Yagi designs.
- The trade-off: for a 5-element OWA on 20m, peak gain is approximately 9.5 dBd rather than the 10.5–11 dBd of a gain-optimized design. In practice this 1 dBd difference is not operationally significant.
5-Element vs 3-Element — The Practical Difference
| Band | Reflector | Driven elem | Director 1 | Director 2 | Director 3 | Boom length |
|---|---|---|---|---|---|---|
| 10m (28.4) | 17.6 ft | 16.7 ft | 16.0 ft | 15.5 ft | 15.1 ft | ~22 ft |
| 15m (21.2) | 23.5 ft | 22.3 ft | 21.4 ft | 20.7 ft | 20.2 ft | ~30 ft |
| 17m (18.1) | 27.6 ft | 26.1 ft | 25.1 ft | 24.3 ft | 23.7 ft | ~35 ft |
| 20m (14.15) | 35.2 ft | 33.4 ft | 32.0 ft | 31.0 ft | 30.2 ft | ~44 ft |
Yagi 5 Element Calculator
This design has published dimensions for more than one band. The default shown below is the first/most common one on the page -- change the frequency and recalculate for the other bands.
Materials for a 20m OWA 5-element Yagi with direct 50 Ω feed, covering the full 20m band
Boom Sag and Structural Integrity
A 44-foot aluminum boom is at the limit of what can be built without trussing or special structural measures. Understanding the sag and stress involved helps design a mechanically sound antenna:
Wind Load and Rotator Requirements
The 5-element 20m Yagi presents substantial wind loading that requires a robust rotator and tower installation:
Element Taper Design for 20m
A 5-element 20m Yagi requires careful element taper design to balance mechanical strength against weight and wind resistance. This guide uses a three-section taper:
Tower and Mast Infrastructure
The 5-element 20m Yagi requires infrastructure that most operators do not already have — this is not an antenna to build as a first tower installation. Prerequisites before building this antenna:
- Tower: minimum 50 ft: a 5-element 20m Yagi at 50 feet has its main lobe at approximately 20° elevation — the minimum for serious DX operation. At 40 feet the lobe rises to 25° — still useful but not optimal. At heights below 40 feet the 5-element's advantage over smaller antennas diminishes because the height is the dominant limiting factor.
- Rotator: heavy-duty class: the Yaesu G-2800, M2 OR5500, or equivalent. These rotators are 3–5× the cost of small rotators but necessary for the wind loading this antenna presents.
- Thrust bearing: mandatory: a thrust bearing above the rotator carries the antenna weight and reduces torque on the rotator shaft. Without a thrust bearing, a heavy antenna like this wears out rotators in 2–3 seasons.
- Coax: LMR-400 minimum: at 50 feet of height, a 100-foot coax run to the shack is realistic. LMR-400 loses 0.14 dB/100 ft at 14 MHz — negligible. RG-8X loses 0.33 dB/100 ft — meaningful for a high-performance antenna where every fraction of a dB matters.
Building the 20m OWA 5-Element Yagi
This build assumes the tower and rotator infrastructure is already in place. All element cutting and boom assembly is done on the ground. The boom truss system is installed before raising. The OWA design's direct 50 Ω feed makes the feedpoint assembly the simplest of any Yagi in this series — just a coax connection and a current choke.
Build the Two-Section Boom with Sleeve Coupler
A 44-foot boom requires two 22-foot sections joined at the center. Cut two lengths of 2-inch OD aluminum tubing to 22 feet each. Join them with an 18-inch length of 1.75-inch OD tubing inserted inside both sections at the joint — the sleeve provides a rigid internal connection. Secure the sleeve to both boom sections with two bolts per side through all layers. Apply Noalox at the sleeve-to-boom contact surface before assembly.
Cut All Five Elements to Starting Lengths
Cut all five elements to starting lengths — each approximately 2 feet longer than the target final length to allow for trimming. Label each element clearly before cutting:
Build each element using the 2-section taper (1.25-inch center, 1.0-inch outer). Apply Noalox at all joints. Secure with two hose clamps and one lock bolt per joint. Deburr all cut ends before assembly — sharp aluminum edges cut hands and cause joint binding during telescoping.
Verify Individual Element Resonance
Verify each element's resonance individually before mounting to the boom — the same procedure used for the 3-element build, elevated on sawhorses at approximately 6 feet:
Mount All Five Elements to the Boom
Mount all five elements to the boom in correct sequence. Install the HDPE insulator plates at the driven element position only — all other elements mount directly to the boom metal-to-metal. Work from the rear of the boom toward the front, verifying each element is perpendicular to the boom and parallel to the other elements before tightening the U-bolt saddle assemblies.
After all five elements are mounted, sight along the boom from each end — all elements should appear as a single line when viewed from directly ahead or behind. Use a long straightedge or string line along the boom top surface to verify the boom is not twisted — any twist in the boom plane will rotate the polarization of individual elements relative to the others, degrading pattern symmetry.
Install the Boom Truss System
Before raising, install a boom truss to control sag. A boom truss uses a vertical mast extension (a 4–6-foot pole mounted above the mast attachment point) from which guy wires run to each boom tip. This is the industry-standard solution for long booms:
Build the OWA Feedpoint Assembly
The OWA design's direct 50 Ω feedpoint is the simplest feed system of any Yagi in this guide series. No gamma match, beta match, or impedance transformer is required — just a coax connection and a current choke:
Raise the Antenna — Multi-Person Operation
Raising a 44-foot, 65-pound antenna to tower height requires a minimum of three people and proper lifting technique. Do not attempt this with fewer than three people.
- Person 1: at the tower top, managing the antenna as it arrives and guiding it onto the mast
- Person 2: on a lower gin pole or ladder, managing the antenna midsection during the raise
- Person 3: on the ground, controlling a lifting line and managing the antenna base during the raise
Raise using a gin pole mounted above the mast. Attach a lifting bridle to the antenna at the balance point (not the mast attachment point) — the bridle should keep the antenna horizontal during the lift. Connect the boom to the rotator mast before releasing the lifting line. Verify the antenna can rotate freely through 360° before securing the coax.
Verify SWR at Operating Height
With the antenna at operating height and the feedline connected, sweep the NanoVNA at the shack end across 13.5–15.5 MHz:
On-Air Performance Verification and Documentation
Once SWR is confirmed, verify directional performance on-air. Use WSPR at 10W for 24 hours — a 5-element 20m Yagi at 50 feet should receive spots from 5,000+ miles consistently during a 24-hour WSPR run under normal propagation conditions. Compare spots in the beam direction vs the reverse direction: the front-to-back ratio should show up clearly as dramatically fewer and weaker spots coming from behind the antenna.
Document: all five element final lengths, spacings, feedpoint SWR across the band, WSPR spot results, front-to-back measurement on a specific signal, and antenna height. This documentation is invaluable if the antenna is ever damaged and needs rebuilding, or if elements slip and need restoration to original dimensions.
After the first month of operation, inspect all hardware: check hose clamp tightness, verify lock bolts are secure, inspect the feedpoint enclosure for water ingress, and re-apply Noalox to any joint showing oxidation. This first-month inspection catches any installation issues before they develop into performance problems or mechanical failures.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| SWR high across full 20m band (above 2:1 everywhere) | Driven element shorted to boom, or coax connection fault | Check DC resistance coax center to shield — should be open circuit; check DE insulator plates | Verify HDPE insulators present; check both coax connections at feedpoint SO-239 |
| SWR curve shifted — minimum below 14.000 MHz | All elements slightly too long | Measure each element — compare to target dimensions | Trim 1 inch from each element outer tip; re-measure SWR; repeat until curve is centered on 20m band |
| SWR curve shifted — minimum above 14.350 MHz | All elements slightly too short | Compare measured element lengths to targets | Elements cannot easily be extended at height; lower antenna and extend outer sections with sleeve couplers |
| OWA SWR not flat — high at one band edge but low at other | Director spacing error — one director position incorrect | Measure all element spacings against design values | Verify spacing of all five elements; correct any spacing more than 3 inches from design value |
| Good SWR but forward gain seems lower than expected | Elements misaligned — not all parallel or not perpendicular to boom | Sight along boom end-on — all elements should appear as single line | Loosen and re-align any twisted element; re-tighten U-bolt saddles |
| Boom drooping excessively after installation | Truss wires not under sufficient tension | Measure boom sag at center — should be under 6 inches | Increase truss wire tension by adjusting turnbuckles or truss attachment points |
| Rotator slipping — antenna does not track rotator commands accurately | Antenna wind load exceeding rotator rating | Check that rotator and antenna wind area ratings are compatible | Upgrade to higher-rated rotator; ensure thrust bearing is installed correctly above rotator |
Is a 5-element Yagi overkill for a typical amateur station?
For casual HF operating, contesting on a budget, or mixed-mode operation across multiple bands — yes, a 3-element Yagi on a modest tower is the more practical and cost-effective choice. The 5-element Yagi makes economic and operational sense for operators who contest seriously on 20m or 15m, who specifically target long-haul DX that requires maximum signal-to-noise advantage, or who have an existing tower and want to maximize its potential. The tower and rotator infrastructure needed for a 5-element 20m Yagi represents a larger investment than the antenna itself — budget accordingly. If you do not already have a 50+ foot tower with a heavy-duty rotator, a 3-element Yagi at good height is a better return on investment than a 5-element on an undersized tower.
Why use the OWA design instead of a gain-optimized design?
The OWA design's practical advantages outweigh its small gain deficit for almost all amateur operators. The flat SWR across the full 20m band means you never need to touch the ATU during a 20m operating session — simply tune the VFO and operate anywhere in the band. The direct 50 Ω feed eliminates the gamma match or beta match hardware and adjustment procedure entirely. And the slightly lower peak gain (9.5 dBd vs 10.5 dBd for gain-optimized designs) represents a 1 dB difference that is operationally invisible in most situations — the person at the other end cannot hear the difference between 9.5 dBd and 10.5 dBd. The only situation where the gain-optimized design is clearly preferable is in a single-frequency EME or weak-signal operation where every 0.1 dB matters — most operators are not in this category.
Can I build a 5-element Yagi for 15m instead of 20m?
Yes — a 15m OWA 5-element Yagi is one of the most popular homebrew beam antennas because the 30-foot boom is far more manageable than the 44-foot 20m version. The 15m version uses the same OWA design proportions scaled to 21.2 MHz — elements approximately 20–23 feet long, boom approximately 30 feet, and the same OWA direct-feed approach. A 30-foot boom on a standard guyed tower at 40–50 feet with a mid-class rotator handles this antenna well without the heavy-duty infrastructure required for the 20m version. Many operators build a 15m 5-element OWA as their primary contest antenna because 15m during solar maximum is the most exciting DX band and the compact antenna delivers competitive performance on a reasonable mechanical budget.
How does a 5-element compare to stacked 3-element Yagis?
Two stacked 3-element Yagis fed in phase can actually outperform a single 5-element Yagi in both gain and front-to-back ratio, particularly at lower elevation angles. A pair of 3-element Yagis stacked 40 feet apart (optimal for 20m) produces approximately 10–11 dBd forward gain with excellent pattern control — comparable to or better than a single 5-element. The stacked pair also has a narrower vertical beamwidth, which focuses the gain at lower elevation angles where DX signals arrive. The trade-off is the complexity of the stacking harness (a phasing line between the two antennas) and the requirement for two towers or a very tall single tower. Many serious contest operators prefer stacked 3-element arrays to single 5-element Yagis for these performance reasons, despite the greater infrastructure commitment.
What happens if an element section slips in high wind?
If an outer element section slips inward through its hose clamp joint, the element becomes shorter and the antenna resonance shifts upward. On the OWA design, which has a broad SWR curve, element slippage of 6–12 inches produces a measurable but not catastrophic SWR increase at the band edges. On a gain-optimized narrow-band design, the same slippage can render the antenna unusable on parts of the band. The lock bolt through each joint overlap is the primary defense against slippage — it provides a positive mechanical stop that the hose clamp cannot. Install lock bolts at every joint during the initial build and check their tightness during the first-month inspection. An element section that has slipped can usually be restored to its original position by loosening the hose clamp and extending the section back to the original overlap length, then re-tightening.
Do I need a lightning protection system for a 5-element Yagi?
Yes — a 50-foot tower with a 44-foot antenna is a significant lightning attractor and lightning protection is essential. A properly installed guyed tower with the tower itself well-grounded (each guy wire base grounded, tower base grounded, and a ring of ground rods around the base) provides reasonable direct-strike protection. A Polyphaser or ICE coax surge protector at the point where the feedline enters the building protects the radio from induced surges even when the direct-strike protection handles the main strike. Disconnect the coax and move it away from the radio when not operating during electrical storms — no surge protector substitutes for a physical disconnect during an active storm overhead. Many tower operators also install a static drain on the antenna itself — a 100K Ω resistor from the coax center conductor to ground at the feedpoint discharges static buildup on the antenna before it becomes a static discharge problem for the radio.