Stop Asking One Antenna to Cover 80–10 Metres
Stop Asking One Antenna to Cover 80–10 Metres
One multiband antenna can be convenient and genuinely useful. The mistake is expecting the same conductor, at the same height, with the same return path to be equally good at low-band work, upper-HF DX and every path in between.
RF.Guru working definition: Common-mode current is the non-cancelling phasor-sum current in a specified set of conductors, evaluated at a defined cross-section and using a declared current-direction convention. In the intended differential transmission-line mode, the outgoing and return currents are equal and opposite, so their phasor sum is zero. When they do not cancel, the remaining current must close through another reference or return path—such as the outside of a coax shield, a mast, equipment chassis, station wiring, nearby structures, earth, the operator, or distributed coupling through the environment.
This broader working definition is especially useful in practical antenna systems. On transmit, non-cancelling current on the outside of the coax can make the feedline and connected structures part of the radiating antenna system unless that path is intentional, clearly defined and properly controlled—for example by providing the required return path and placing a suitable common-mode choke at the correct boundary.
Any antenna asked to cover 80 through 10 metres must make trade-offs. That is not an insult and it does not make the antenna bad. A wide-coverage wire may be exactly right for a portable station, a small garden or an operator who values one feedline and rapid band changes. Convenience is a legitimate engineering requirement.
The trouble begins when “it tunes” becomes “it does every job.” Across a four-to-one frequency span, the same wire changes electrical length dramatically. Current maxima move, the number and direction of radiation lobes change, ground interaction changes, and the feedline or supporting conductors may become a larger part of the installed antenna. A tuner can present a suitable impedance to the transmitter; it cannot restore a pattern that the geometry does not produce.
The practical starting point: give 80 and 40 metres a dedicated low-band system, then choose a separate upper-HF wire or vertical for 20 through 10 metres. The split makes each current path, pattern and installation compromise easier to inspect. It is a design method—not a universal two-antenna performance guarantee.
Low Bands and Upper HF Are Different Jobs
On 80 and 40 metres, available height and space usually dominate the design. A wire that is low in wavelengths can still make excellent contacts, but its ground loss and elevation pattern depend on its height, vertical and horizontal proportions, bends, end clearance and return path. “Inverted-L” describes a shape, not one fixed pattern.
On the upper bands, that same long wire is several wavelengths long. It may offer useful gain in some directions, deep nulls in others and multiple elevation lobes. That can be an advantage when a lobe serves the desired path; it can also be the reason a station sounds strong in one direction and absent in another. Calling the wire an 80–10-metre antenna says which bands can be matched. It does not describe the azimuth or elevation pattern on each band.
DX is not one take-off angle either. ITU-R P.533 treats elevation angle as a path, mode and ionospheric-height variable. A low-angle lobe is useful for many long paths, but it is not the only angle that can support DX. The right question is whether the installed antenna puts useful field into the angles and directions required at that time—not whether its category is “vertical” or “wire.”
Give 80 and 40 Metres Their Own Current Path
A dedicated low-band antenna lets the supports, wire shape and common-mode boundary be chosen for 80 and 40 metres instead of inheriting an upper-band compromise. One RF.Guru example is the EFHW8040 dual-band inverted-L. Its role in this station plan is deliberately narrow: handle 80 and 40 metres while another antenna handles upper HF.
An end-fed half-wave is not a one-wire circuit with no return. Transformer capacitance, an intentional counterpoise or local reference, the exterior of the coax, nearby conductors and the choke boundary all influence the installed current path. The feedline should therefore be routed deliberately, exterior-shield current should be measured at several positions on both bands, and any choke placement should be verified after installation.
This is where the split pays off. The low-band antenna can be raised, bent or moved to suit its own current distribution without pretending that its 10-metre pattern must remain useful. It also makes honest comparisons possible: change the low-band geometry, restore the baseline, and compare the same paths without changing the upper-HF antenna at the same time.
High voltage and public access: end-fed antennas have high-voltage regions. Support strength, end clearance, weather protection and a controlled exclusion area must be designed before transmitting. A convenient feedpoint is not permission to put an energised conductor within reach.
Choose the Upper-HF Antenna by Mission
Once 80 and 40 metres have their own system, the upper-HF choice becomes clearer. The options below are not a ranking. They solve different mechanical, directional and return-path problems.
| Upper-HF choice | Why it belongs in the plan | What still needs proof on site |
|---|---|---|
| VertX fan vertical | A dedicated 20–10-metre vertical system with separate upper-band radiator functions and a defined radial/return system. | Branch currents, radial loss, feedline exterior current, mutual coupling and the installed elevation pattern. |
| EFOC8 upper-HF wire | A compact 20–6-metre end-fed off-centre wire when a horizontal or sloping wire suits the site better than a ground-mounted vertical. | Current distribution, intended return path, choke boundary, feedline participation and band-by-band pattern. |
| XentrX vertical dipole | A 40–6-metre off-centre vertical-dipole geometry when a traditional radial field is impractical. | Current balance between the two radiator sections, common-mode current on the feedline, nearby-conductor coupling and installed pattern. |
For the original station strategy, VertX is the direct upper-HF vertical choice and EFOC8 is the wire alternative. XentrX addresses the operator who wants vertical polarisation without building a conventional monopole radial field. Its lower radiator section supplies the intended differential return conductor; that does not make feedline common-mode current impossible or remove the need for measurement.
The current VertX architecture also shows why “more bands on one feedpoint” is not automatically better. Its deliberately limited radiator set avoids adding a separate resonator for every nearby band. Matching can be recovered after coupled elements move one another's impedance, but acceptable SWR does not prove that branch-current phase, efficiency or elevation pattern stayed where intended. That is why the design treats mutual coupling as something to manage and measure, not something a tuner erases.
Two Antennas Do Not Automatically Beat One
Dividing the work removes one compromise but introduces others. Two transmit antennas can couple to each other. The unused feedline can become a parasitic conductor. An antenna switch has finite isolation. Nearby masts, radial wires and building metal can alter both systems. If both antennas are connected to separate radios, transmit interlocking and filtering become station-safety requirements rather than optional refinements.
A single well-installed multiband doublet, loop or end-fed wire may outperform a badly installed two-antenna system. It may also be the only practical choice. The recommendation is therefore not “buy two antennas.” It is “stop hiding different jobs behind one coverage label.” If one antenna is chosen, document which jobs it must do and accept the measured compromises knowingly.
Measure the Split at the Same Reference Plane
SWR is only one part of the comparison. A fair station test keeps transmitter power, measurement reference plane, feedline loss, receiver state and propagation interval under control. The result should combine current-path evidence with on-air evidence.
- Record each antenna's complete geometry, height, ground or counterpoise arrangement, feedline route and choke configuration.
- Measure complex impedance at a declared reference plane rather than comparing one antenna at the feedpoint with another through an unknown length of coax.
- Map exterior-feedline current at repeatable positions on every band used.
- Use a validated NEC model or measured field pattern to identify lobes and nulls; do not infer pattern from SWR.
- Compare wanted-signal SNR or calibrated field strength in an A/B/B/A sequence, using multiple stations and paths rather than one fading signal.
- Repeat after restoring the first configuration so that propagation drift is less likely to masquerade as antenna improvement.
NEC can compute segment currents, input impedance and far-field pattern for a declared geometry and ground model. Those outputs are related, but they are not interchangeable. A model that matches measured impedance still needs its geometry, loss assumptions and pattern checked against the installed antenna.
A Better 80–10-Metre Station Strategy
The direct RF.Guru position remains simple: when space and switching permit, separate the low-band and upper-HF jobs. Use a dedicated 80/40-metre system such as the EFHW8040 for the low bands. Choose VertX when the upper-HF mission calls for a fan vertical, EFOC8 when a compact upper-HF wire suits the supports, or XentrX when a vertical-dipole geometry is preferable to a monopole radial field.
Then test the installed station. Do not claim that the vertical always has the lower useful angle, that the wire always has lower noise, or that two antennas always radiate more efficiently than one. Those outcomes depend on the site, geometry, ground, feedline current, loss and the propagation path being served.
Bottom line: one 80–10-metre antenna is a valid convenience choice. A divided station is the stronger engineering choice when you want each band group to have a deliberate current path and a pattern you can inspect. Coverage belongs on the label; performance belongs in the measurements.
Engineering and product records checked
Mini-FAQ
- Is one 80–10-metre antenna always a bad choice? No. It may be the best choice for limited space, portable operation or simple switching. Its band-by-band pattern and loss still need to be understood.
- Why separate 80/40 metres from upper HF? The two band groups impose different electrical lengths, support constraints, ground interaction and useful patterns. Separate systems make those compromises easier to control and measure.
- Is a vertical always best for upper-HF DX? No. A vertical may provide useful low-angle radiation, but terrain, radial loss, surrounding conductors and the required path angles determine the installed result.
- Does an EFHW need a return path? Yes. The intentional counterpoise or local reference, coax exterior, transformer capacitance, nearby conductors and choke boundary participate to different degrees.
- Does a vertical dipole eliminate common-mode current? No. It provides two intended radiator sections, but imbalance and feedline coupling can still put current on the coax exterior.
- How do I prove the two-antenna plan is better? Compare complex impedance, exterior-feedline current, accepted power and repeatable A/B/B/A field or SNR results at the same reference plane and operating conditions.