VertiCore 5/8λ for 4, 6, 10 and 12 m
VertiCore 5/8λ for 4, 6, 10 and 12 m
A full-length monoband radiator with an offset driving point, a raised four-radial plane and measured 1:1 balun options—designed as one repeatable RX/TX current system.
VertiCore's 5/8λ versions do not obtain their approximately 50 Ω feed from a hidden coil, trap or impedance-ratio transformer. The radiator connection is moved a short distance upward on the tube and the elevated radial plane moves with it. RF.Guru establishes that band-specific driving point by measuring the finished radiator, radial and balun assembly.
Why Use 5/8λ on These Bands?
A mechanically rigid full-length 5/8λ radiator is practical on 4 m, 6 m, 10 m and 12 m. The longer current distribution can favour a strong low-elevation component when the return system, height and surroundings support it. That makes the geometry attractive for DX, terrestrial propagation and sporadic-E operation where applicable.
| Band | Radiator | Return system | Operating context |
|---|---|---|---|
| 12 m | Band-specific 5/8λ aluminium radiator | Four elevated 45° 1/4λ radials | HF DX with a controlled monoband current system |
| 10 m | Band-specific 5/8λ aluminium radiator | Four elevated 45° 1/4λ radials | DX and sporadic-E operation |
| 6 m | Band-specific 5/8λ aluminium radiator | Four elevated 45° 1/4λ radials | Terrestrial, sporadic-E and other propagation modes |
| 4 m | Band-specific 5/8λ aluminium radiator | Four elevated 45° 1/4λ radials | Band-specific terrestrial and propagation openings |
A 5/8λ label alone does not guarantee a particular gain or takeoff angle. Those are installed-system outcomes determined by the full current distribution, ground, height, mast, feedline, nearby structures and loss.
The Offset Driving Point
Voltage and current are not constant along a resonant radiator. Changing the driving-point position samples a different local voltage-to-current ratio. VertiCore uses that fact directly: the feed connection is placed slightly above the mechanical end of the radiating tube.
The radial hub does not remain below while only the centre-conductor connection moves. The four-radial plane is raised with the feed connection. The lower radiator segment, upper radiator and elevated radials therefore form one defined electromagnetic structure.
This is a measured product geometry, not a universal recipe. Tube diameter and taper, lower-segment length, radial length/angle/height, mast and nearby conductors all affect the result. Copying one offset distance into a different structure does not reproduce VertiCore.
The Radials Complete the RF Circuit
The four elevated 45° quarter-wave radials carry return current and influence input resistance, reactance and pattern. Their rigid construction helps preserve geometry between installations, but final surroundings still matter.
- Install all four band-specific radials before measuring or tuning.
- Keep angle, height and nearby clearances symmetrical.
- Keep radial tips clear of soil, roofs, gutters, fences, wiring and accessible areas.
- Route the coax away from the radial plane at right angles initially.
- Recheck after the mast, bonding and all cable routes are final.
The 1:1 Balun Has a Different Job
The offset radiator/radial geometry establishes the nominal feed impedance. The measured 1:1 balun controls common-mode current on the coax exterior. It helps keep the feedline from becoming an uncontrolled additional radiator or return conductor, but it is not the mechanism that transforms an arbitrary 5/8λ input to 50 Ω.
SWR is not a common-mode measurement. A convenient feedpoint match can coexist with substantial current on the coax exterior. Measure installed feedline current and repeat when the coax, mast or nearby conductors move.
Understanding the Measured SWR
The production geometry is measured as a finished band-specific assembly. The useful record is complex impedance or S11 across the operating band at a declared reference plane. A remote shack-end reading includes the feedline transformation unless that line is characterized and de-embedded.
Small changes in radial angle, feed position, mast coupling, coax route and nearby objects can move both resistance and reactance. Fine adjustment therefore has to preserve the intended relationship between the radiator connection and radial plane; moving one part alone creates a different antenna.
Pattern, Efficiency and Match
A low SWR indicates that power can be accepted at the reference plane. It does not prove radiation efficiency, low ground loss or the intended elevation pattern. The same real input resistance can contain different proportions of radiation and loss.
The VertiCore 5/8λ geometry is designed for a strong low-elevation component, but the realised pattern must be interpreted for the installed site. Simplified model plots are useful for current and lobe trends; calibrated field measurements or a converged full-structure model are needed for exact installed gain and angle.
Why the Longer-Band Products Use 1/4λ
On 15 m, 17 m and 20 m, the VertiCore 1/4λ family keeps the full-size rigid structure within a more practical height. The choice is not a claim that one electrical length is universally efficient and the other is not; it balances mechanical size, monoband current distribution, installation and operating goal.
Installation and Power Boundary
- Assemble the correct band-specific radiator, raised feed structure, all four radials and selected 1:1 balun.
- Set feedpoint height from radial-tip clearance and site requirements, not from a universal takeoff-angle table.
- Measure complex impedance at the feedpoint and outside-of-coax current with the final mast and cable route.
- Test at increasing power while monitoring connector, feed contact, balun, joints and nearby dielectrics for heat or drift.
- Reinspect after weather events and periodically protect clean aluminium joints with compatible anti-corrosion compound.
The current VertiCore product offers measured and tested 6 kW and 9 kW balun service options. Usable power remains conditional on frequency, waveform, PEP and average power, duty cycle, tune duration, mismatch, feedline/connectors, temperature and installation. Applicable licensing and RF-exposure limits always govern operation.
Mini-FAQ
- Which bands use the VertiCore 5/8λ geometry? The band-specific 4 m, 6 m, 10 m and 12 m versions use 5/8λ radiators with four elevated 45° quarter-wave radials.
- How does VertiCore reach approximately 50 Ω without a base coil? The radiator connection is shifted upward and the radial plane moves with it. RF.Guru establishes the resulting driving point on the finished band-specific assembly by measurement.
- Does the 1:1 balun perform the impedance transformation? No. The radiator/radial geometry establishes the nominal input. The balun controls unwanted common-mode feedline current.
- Can I copy the same feedpoint offset to another 5/8λ vertical? Not reliably. Tube geometry, lower segment, radials, mast and surroundings all affect the driving point.
- Does the 5/8λ label guarantee a fixed takeoff angle? No. Installed height, ground, radial currents, mast, feedline, nearby structures and loss determine the realised elevation pattern.