A 20 m Tuned Vertical or a Low-Band EFHW Inverted-L?
A 20 m Tuned Vertical or a Low-Band EFHW Inverted-L?
A 20 m base-fed vertical can be a serious 80-metre antenna and can be matched on 160 metres. A long EFHW inverted-L can be an attractive two-band alternative when a large radial field is impractical. Neither wins by name: compare current distribution, every dissipative element and the installed field at the elevation angles you need.
If I have enough space for a long low-band wire but cannot build the radial system a ground vertical deserves, I will usually investigate the EFHW inverted-L first. If the site can support an effective radial field and the goal is low-elevation radiation, the vertical deserves an honest comparison. The tuner is not the deciding factor; the whole current path is.
Joeri's practical position: do not force a 20 m radiator to carry the 160-metre job merely because a tuner can produce 50 Ω. But do not award the contact to the longer inverted-L before measuring its transformer, return path, common-mode current and actual pattern.
The Same 20 m Radiator Is Two Different Electrical Lengths
A 20 m vertical is close to a quarter wavelength in the middle of the 80-metre amateur band and close to one eighth wavelength in the middle of 160 metres. Exact electrical length changes with conductor diameter, loading, top capacitance, nearby conductors, soil and operating frequency.
Near a quarter-wave mode, a base-fed vertical can place substantial current along the conductor and can be efficient when the return system has low loss. On 160 metres the same bare radiator is electrically shorter. A matching network can cancel its input reactance and transform the remaining resistance, but it does not make the physical current distribution equal to that of a taller radiator.
Top loading is a valid way to change that distribution. A capacity hat or horizontal top wire can raise radiation resistance and reduce the inductive loading required compared with base loading alone. Once top loading is added, however, the system is no longer the simple 20 m vertical in this comparison; model and measure the real structure.
Shorter Does Not Mean Useless—but Loss Has Less Room to Hide
For a series representation at one declared feedpoint, a useful first-order efficiency expression is:
η = Rradiation / (Rradiation + Rloss)
This ratio is meaningful only when radiation and loss resistances belong to the same equivalent circuit and reference plane. It does not permit an EFHW's kilohm input resistance to be compared directly with a monopole's base radiation resistance.
As a vertical becomes electrically shorter, its radiation resistance normally falls. Ground-system resistance, loading-coil resistance, matching-network resistance and conductor loss can then consume a larger fraction of accepted power. That is why the 160-metre case is demanding—not because using a tuner is inherently wrong.
An efficient matching network with suitable component Q, voltage clearance and current capability can transform a difficult load with modest loss. A poor network can waste power. The only defensible number comes from the actual complex load, components, frequency, power, duty cycle and temperature.
The Vertical's Other Half Is the Radial System
A base-fed vertical is not a one-wire antenna. Its radials, ground screen, connections and soil coupling form the return side of the RF circuit. Current lost in resistance around the feedpoint does not become useful radiation, even when SWR is low.
Rudy Severns, N6LF, measured real verticals while varying radial count, length, elevation and soil relationship. His 160-metre work found a site-specific progression as an on-ground radial field grew from four to sixty-four conductors. The transferable lesson is the method, not a universal count: performance depends on total conductor geometry, current division, soil, symmetry and surroundings.
A few elevated radials can work well when their lengths and currents are controlled, but asymmetry and nearby conductors can detune them and divide current unequally. An on-ground field is usually less resonant and more tolerant, but its optimum conductor allocation remains a site and budget decision. Measure radial currents and field change rather than counting wires as a badge.
The EFHW Inverted-L Moves the Compromise
A low-band EFHW inverted-L uses a much longer conductor arranged so the installed system operates near a half-wave mode on the lower band and a higher mode on the upper band. Bending the wire allows one support to carry a vertical section while the remainder runs horizontally or slopes away.
That longer current distribution can be valuable when the alternative is an electrically short 160-metre vertical with a compromised return field. It also creates different constraints: high RF voltage near the end-fed terminal, a demanding impedance transformer, significant space for the upper wire and a return path that must be declared rather than assumed away.
The EFHW can work without a large monopole-style radial field. It cannot work without electromagnetic return current. The return may include an intentional conductor, local capacitance, a controlled length of coax exterior, support metal and nearby structures. If that path is undefined, the feedline and station wiring can become part of the antenna.
High Feedpoint Impedance Is Not High Radiation Resistance
An EFHW is fed near a high-voltage, low-current part of its installed standing-wave distribution. The high input resistance seen there is a port property. It is not automatically the antenna's radiation resistance, and it is not evidence that transformer, conductor or environmental loss is small.
The impedance transformer must be tested across the installed complex-load region. Magnetising impedance, leakage inductance, winding capacitance, core and copper loss, voltage margin, flux and thermal equilibrium all matter. A nominal ratio is neither a bandwidth nor a power rating.
The transformer and the common-mode choke do separate jobs. The transformer converts the differential load presented at its output. A separately specified choke establishes the chosen boundary for coax-exterior current. Choke placement follows the intentional return branch and a band-by-band exterior-current map, not one copied fraction of a wavelength.
A Tuner Match and an EFHW Match Need the Same Accounting
The comparison is not “lossy tuner versus efficient transformer.” Both networks can be excellent or poor. Include these terms at the same input reference plane:
- 20 m vertical: radial and soil return loss, loading or tuning-network loss, conductor and connection loss, feedline loss and unintended feedline-exterior current.
- EFHW inverted-L: transformer loss, conductor and connection loss, intentional and unintended return-path loss, choke loss, feedline loss and environmental coupling.
A tuner at the vertical's base can keep the long station coax close to 50 Ω. A tuner in the shack can leave the coax carrying a severe mismatch, adding dissipation according to line type, length, frequency and load. Likewise, a low SWR behind an EFHW transformer says nothing about the transformer's insertion loss or temperature.
Pattern Can Reverse an Efficiency Ranking
A vertical over an effective return system can produce useful low-elevation radiation. That may be exactly what a distant path needs. An inverted-L has vertical and horizontal current components, but they cannot be divided into a simple “vertical equals DX, horizontal equals local” rule. Their fields combine in amplitude and phase over real ground.
The vertical-section height, bend position, horizontal-wire height and direction, return path, feedline exterior, terrain and nearby structures all influence the inverted-L's azimuth and elevation pattern. On the higher band, additional current maxima can create more lobes and nulls. Ground conductivity and topography change both antennas.
A stronger signal on one receiver does not by itself identify higher total efficiency. The winning antenna may simply place more of its accepted power toward that bearing and elevation. That is still a useful win—provided we name it correctly.
| Question | What decides it |
|---|---|
| Which loses less accepted power? | Radial or return loss, matching-network or transformer loss, conductor loss and feedline loss at one declared boundary. |
| Which is stronger for DX? | Installed gain at the relevant bearing and elevation, with equal accepted power and controlled propagation. |
| Which is better regionally? | Useful high-elevation field for the actual path, not the presence of a horizontal wire by itself. |
| Which is easier to maintain? | Available supports, radial access, transformer or tuner weather protection, voltage clearance and inspection. |
| Which covers both bands? | Measured impedance, network range and loss, bandwidth, current control and pattern on each band separately. |
Bandwidth Is a Clue, Not an Efficiency Meter
An electrically short vertical with substantial loading often has a higher system Q and narrower matched bandwidth than a less heavily loaded structure. That can make tuning sensitive to rain, vegetation or nearby objects. Yet a broad SWR curve can also come from loss, and an EFHW transformer can narrow or reshape the apparent response.
Record the complex feedpoint impedance and network settings across the band, not only the 2:1 SWR width at the transmitter. Then measure loss and temperature. Bandwidth helps diagnose the system; it does not independently certify radiation efficiency.
Choose from the Site You Actually Have
I investigate the long EFHW inverted-L first when the site offers one high support and enough horizontal space but cannot accept a substantial radial field. The extra wire may produce a more useful low-band current distribution than forcing a bare 20 m vertical onto 160 metres.
I investigate the vertical first when a maintainable radial system is practical, low-elevation coverage is the priority and the site can support an efficient base network. On 80 metres, the 20 m radiator is already close to a natural quarter-wave starting point. On 160 metres, top loading or a larger structure may improve the design before we ask a tuner to solve everything at the port.
Space, storm loading, safe clearances, construction cost and band-change speed are legitimate engineering constraints. The best station antenna is the one whose measured performance and operating burden fit the job.
Run the Comparison at Equal Accepted Power
- Freeze both geometries: record every conductor, support, radial or return path, feedline route, bond, terrain feature and nearby metal object.
- Measure complex impedance: place calibrated reference planes at the antenna terminals and station input; sweep both bands rather than one spot frequency.
- Measure network loss and stress: use representative complex loads, operating power and duty cycle; record voltage, current and equilibrium temperature.
- Map return current: measure radial-current division and coax-exterior current at repeatable positions.
- Model the complete structure: include the inverted-L bend, horizontal leg, vertical return system, intended coax section, mast and defensible ground parameters.
- Compare fields: use equal accepted power, simultaneous remote receivers or rapid A/B/B/A switching, fixed receiver settings and a restored baseline.
RF safety: EFHW terminals and wire ends can carry high RF voltage; matching coils and elevated radials can also develop hazardous voltage. Keep accessible areas outside the assessed exposure and touch boundaries, maintain mechanical and electrical clearance, de-energise before adjustment and verify component temperature at the intended power and duty cycle.
Bottom line: a 20 m vertical with a tuner is not automatically a poor 160/80-metre antenna, and an EFHW inverted-L is not automatically better. When the vertical's radial and loading compromises are severe, I expect the longer inverted-L to be the stronger starting point. When the vertical has an effective return system and the right installed pattern, it may win. Measure the complete systems and let the path decide.
Primary technical references
- Rudy Severns, N6LF — Ground-System Performance, Part 1: Test Setup and Instrumentation
- Rudy Severns, N6LF — 160-Metre Vertical Ground-System Experiment
- IEEE Std 145-2025 — Standard for Definitions of Terms for Antennas
- Recommendation ITU-R BS.705-2 — HF transmitting and receiving antenna characteristics and diagrams
- Numerical Electromagnetics Code — NEC-2 User's Guide, Part III
- NIST — A Two-Port Model for Antennas in an Arbitrary Environment
- Recommendation ITU-T K.52 — Guidance on complying with RF electromagnetic-field exposure limits
Mini-FAQ
- Can a 20 m vertical work on 160 metres? Yes. It can be matched and can radiate useful signals, but as an electrically short vertical its efficiency is particularly sensitive to radial, soil, loading-network and conductor loss.
- Is the same vertical naturally suited to 80 metres? A 20 m radiator is close to a quarter-wave starting point around the middle of 80 metres. The installed resonance, impedance and pattern still depend on the return system and environment.
- Does a tuner make the 20 m vertical electrically taller? No. A tuner transforms the port impedance. Top loading or a physically larger current-carrying structure changes the current distribution.
- Does an EFHW inverted-L avoid every radial and counterpoise? It can avoid a large monopole-style radial field, but it still needs a measurable return through an intentional conductor, capacitance, coax exterior or a controlled combination.
- Is an EFHW transformer always less lossy than a vertical tuner? No. Either network can be efficient or lossy. Compare them with representative complex loads, power, duty cycle, voltage, current and temperature.
- How do I decide which antenna is better? Compare both at equal accepted power, measure every loss and return current, and evaluate installed field strength at the bearings and elevation angles your paths require.