VertX Technical Architecture: Fewer Resonators, Better-Controlled Currents
VertX Technical Architecture: Fewer Resonators, Better-Controlled Currents
Three years of VertX testing shaped a deliberately simpler radiator set. A convenient feedpoint match matters, but preserving the intended radiator current and elevation pattern matters more.
VertX began from a familiar fan-vertical idea: give every band its own resonator and trim until every dip lands where expected. The analyser could be satisfied. The more important question was whether all those closely spaced wires still produced the current distribution and low-elevation response we wanted.
The current VertX decision: use the aluminium tube on 20 m, one dedicated wire on 15 m and three staggered wires across 10 m. Use tuner-assisted operation on 12 m and 17 m rather than crowding two more resonators into the same coupled structure.
See the available mechanical and balun variants, current radiator architecture and optional radial systems.
The Radiator Set Has Deliberate Jobs
| Band | Current radiator path | Engineering boundary |
|---|---|---|
| 20 m | Aluminium tube as the principal radiator | Installed match and pattern still depend on the radial field, ground, support and feedline boundary |
| 15 m | One dedicated wire | Tune and verify it with the complete antenna assembled |
| 10 m | Three staggered wires | Intended to cover a wide allocation; no universal branch frequencies or band-edge SWR are claimed |
| 12 m | Tuner-assisted operation | A tuner restores a load relationship, not a guaranteed efficiency or low-angle pattern |
| 17 m | Tuner-assisted operation | Current distribution and loss must be verified at the installed configuration |
The feedpoint is placed as low as mechanically practical. That keeps the mechanical layout and intended radial return plane clear; it is not presented as an automatic gain or takeoff-angle improvement.
Why Two Nearby Resonators Were Removed
Twelve metres is electrically close to the 10 m and 15 m structures. Seventeen metres is close to the 15 m wire and 20 m tube. In a common-feed structure, each conductor contributes mutual impedance to the others. Adding a wire can move several resonances and redistribute current even when the new wire is not the branch we intend to use on that band.
Repeated trimming can bring the impedance dips back. A tuner can also transform the complete load to a range the transmitter accepts. Neither result proves that the intended branch regained its original current amplitude and phase. It therefore does not prove that radiation efficiency or the low-elevation component remained intact.
RF.Guru measured the denser radiator set and decided that the interaction and tuning effort were not worth those two dedicated wires. This is a decision about this geometry and this product. Other dense fan antennas can work when their installed currents and patterns are controlled.
Why Three Wires Still Make Sense on 10 m
The Belgian 10 m amateur allocation runs from 28.000 to 29.700 MHz. That 1.7 MHz span is materially wider in fractional terms than 12 m or 15 m. One short, high-Q resonator can force a compromise between the lower and upper parts of the allocation.
Three modestly offset 10 m wires create staggered resonances for bandwidth. Because they operate at the highest frequency in VertX, their physical-length differences are small relative to the overall vertical structure. RF.Guru's testing found that this allowed useful bandwidth while keeping the vertical geometry deliberately compact.
The three wires still couple. They are not three independent antennas, and their exact frequencies, lengths and SWR envelope are production data rather than universal recipes. The engineering claim is limited to the measured design choice: the bandwidth benefit justified those three closely related conductors, while adding separate 12 m and 17 m resonators did not.
What the A/B/B/A Receive Comparison Established
RF.Guru compared VertX with a DX Commander at the same site using the A/B/B/A swap sequence also used for receive-antenna evaluation. VertX was consistently favoured on receive, with the clearest difference on 10 m, 12 m and 15 m. On 17 m and 20 m, the two antennas were broadly on par.
This comparison supports the design decision but does not isolate its cause. Reduced mutual coupling and a better-preserved current distribution are the working explanation. The site did not permit RF.Guru's drone-borne oscillator method for a far-field pattern plot, so no numerical gain or takeoff-angle conclusion is attached to the result.
The Tuner Solves the Port, Not the Pattern
On 12 m and 17 m, the tuner sees the combined impedance of the tube, the 15 m and 10 m branches, radial system, feedline and surroundings. It can transform that impedance. Its own loss, the feedline loss under mismatch and the current division within the antenna remain separate questions.
Do not read “tuner-assisted” as “same pattern as a resonant quarter-wave.” The current VertX architecture does not claim equal gain, efficiency or takeoff angle for 12 m and 17 m. Those claims require branch-current maps and installed field or pattern measurements.
Radials Follow Measurement, Not a Slogan
The VertX radial field is an on-ground return system. Rudy Severns, N6LF, measured the interaction of radial count, length, soil and frequency. His work does not support the internet shortcut that any larger number of shorter wires must beat a smaller number of useful long wires.
| Current optional kit | What it is good for | What not to claim |
|---|---|---|
| 16 × 5 m | Compact baseline with useful long radial coverage | Not equivalent to a perfect ground plane on every soil |
| 24 × 5 m | All-equal step up to 120 m of useful-length wire | Lower loss still depends on soil, layout and the complete installation |
| 32 × 5 m radials | The densest all-equal option with 160 m of useful-length wire | Not a universal optimum independent of soil, layout and installation |
Spread the available radials evenly and preserve the full five-metre conductor length wherever the site permits. Measure the finished system. The 24 × 5 m and 32 × 5 m options add equal-length angular coverage without making short radials the design objective.
Feedline Current Needs Its Own Check
The radial plate provides the intended return-current region. The coax exterior must not become an uncontrolled extra branch that changes tuning and pattern. Measure common-mode current around the complete coax at several repeatable positions. A choke or additional line isolator should be selected from the measured current path and its voltage, current, mismatch, duty-cycle and thermal requirements—not from a universal placement slogan.
How VertX Is Verified
- Calibrate the VNA at a declared reference plane and save complex impedance, not just minimum SWR.
- Map current on every accessible branch and around the complete feedline at repeatable positions.
- Compare the complete radiator set with a questioned branch removed or detuned, then restore it and repeat.
- Keep radial layout, coax route, tuner state, soil condition and nearby conductors fixed during comparisons.
- When the claim concerns takeoff angle, add a controlled field or pattern comparison. Input impedance is not a pattern measurement.
VertX Test and Pattern References
The following simplified pattern plots belong to the three-year VertX development and test record. They support the engineering discussion but are not universal far-field certificates for every installation. See the limits of simplified radiation models.
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Primary engineering references
Mini-FAQ
- Why did VertX remove dedicated 12 m and 17 m wires? In the tested geometry, their proximity to the neighbouring radiators added coupling and tuning complexity that did not justify retaining them.
- Does the tuner preserve low-angle radiation on 12 m and 17 m? Not by itself. It transforms impedance; current distribution, loss, efficiency and pattern require separate evidence.
- Why are there three 10 m wires? They create staggered resonances across Belgium's wide 28.000–29.700 MHz allocation while keeping the overall high-band geometry similar.
- Is the lowest possible feedpoint automatically better? No. It is the chosen mechanical and return-path geometry. Performance still depends on the complete installed current system.
- Which radial kit is best? The 16 × 5 m kit is a compact baseline; the 24 × 5 m and 32 × 5 m kits add equal-length coverage. None is universally optimum independent of soil and layout.
- What do the retained plots establish? They belong to the three-year VertX development and test record, but they are not universal far-field certificates for every installation.