Current Distribution in Inverted-L Antennas

Classic radial-fed inverted-L vs. EFHW16080 68:1 vs. EFOC56 4:1

An inverted-L is not one single antenna type. It is a shape. The electrical behavior depends on where the antenna is fed, how long the wire is electrically, and what the system uses as the RF return path.

The most important rule is simple:

This is where many inverted-L discussions become confusing. A classic quarter-wave inverted-L, an EFHW16080 inverted-L, and an EFOC56 inverted-L may look similar in the garden, but electrically they are very different antennas.

The Classic Radial-Fed Inverted-L

A classic low-band inverted-L is basically a base-fed vertical monopole with the top bent over. It is usually around a quarter wavelength electrically and is fed against a buried radial field or elevated radials.

Classic base-fed inverted-L

       horizontal top section
             ┌──────────────────── free end
             │
             │
             │ vertical section
             │
feed/radials ┴

Current:
MAXIMUM near feed/base
decreases toward the open end

In this type of antenna, the highest current is near the base and feedpoint. That makes the lower vertical section and the radial system extremely important. The horizontal wire acts partly as top loading. It helps bring the antenna to resonance, changes the feed impedance, and can contribute some horizontally polarized radiation, but the vertical high-current portion is usually the main low-angle DX radiator.

This also explains why a classic inverted-L needs a real RF return system. A couple of ground rods is not a radial field. If efficiency matters, the antenna needs a good buried radial system or properly installed elevated radials.

What Happens When the Horizontal Section Is Lower?

In a classic inverted-L, lowering the horizontal section usually increases capacitance to ground, lowers the resonant frequency, changes the feed impedance, increases coupling to nearby objects, and may increase loss if the wire is very low.

But in most normal quarter-wave inverted-L installations, the main current maximum still remains near the base. The current distribution changes, but the main high-current region does not usually move far up the wire in the same way it does in a voltage-fed end-fed system.

This is why a classic inverted-L can still work well when the top wire slopes, bends, or follows the available garden layout, provided the vertical section is reasonable and the radial or counterpoise system is good. The danger is that ground loss can make the SWR look better while the real radiated power is worse.

The EFHW16080 Inverted-L With a 68:1 Transformer

The EFHW16080 is a different animal. It is a voltage-fed, high-impedance end-fed system. On 160 m, the wire is approximately a half-wave. The feedpoint is not a high-current base like in a classic inverted-L. It is normally a high-voltage, low-current point.

With about 81 to 82 m of wire, the main current maximum on 160 m is roughly halfway along the wire.

EFHW16080 on 160 m, simplified as about 1/2 wave total

feed end                                                far end
68:1                                                    open end
  │                                                        │
  └──── vertical ──── bend ───── horizontal wire ──────────┘

Current:
low at feed → rises → MAX around mid-wire → falls to low at far end

Using 81 m as a simple reference length, the 160 m current maximum is approximately:

81 m / 2 ≈ 40.5 m from the feedpoint

If the vertical section is 12 m, the main current maximum is roughly:

40.5 m - 12 m ≈ 28.5 m into the horizontal section

If the vertical section is 16 m, the current maximum is roughly:

40.5 m - 16 m ≈ 24.5 m into the horizontal section

These are simplified current-position estimates. Real positions shift with wire insulation, height above ground, bends, soil, nearby objects, transformer behavior, and the chosen operating frequency.

This is the key point: on 160 m, the strongest current in an EFHW16080 inverted-L may not be near the feedpoint at all. It may be well out in the horizontal or sloping section.

So yes, lowering the horizontal wire can have a much stronger effect than many operators expect. If the current-rich part of the antenna is low, close to trees, close to buildings, close to metal, or close to lossy ground, then the useful radiation, takeoff angle, pattern stability, and efficiency can all change significantly.

The EFHW16080 on 80 m

On 80 m, the same wire is close to a full wave. That produces multiple current lobes along the antenna.

EFHW16080 on 80 m, simplified as about 1 wave total

feed      max        min        max       end
 │         │          │          │         │
0 m      20 m       40 m       61 m      81 m

Current:
low → maximum → low → maximum → low

With a 12 m vertical section, the first current maximum is roughly:

20 m - 12 m ≈ 8 m into the horizontal section

That means on 80 m, the first current-rich part may sit near the bend or early in the horizontal wire. A second current maximum appears farther along the wire.

This is very different from the classic base-fed inverted-L. In an EFHW16080, the current maxima are not forced to stay at the feedpoint. They are set by the standing-wave pattern on the whole wire.

Does the EFHW16080 Need Radials?

Not in the same way as a classic quarter-wave vertical. But that does not mean it needs no RF return path.

An EFHW always uses something as the return side of the system. It may be a short counterpoise, the outside of the coax shield, nearby capacitance, a ground connection, or a combination of these. The better design approach is to make that return path controlled instead of accidental.

This is also why choke placement matters. A line isolator does not merely “clean up the coax.” It can define where the antenna system ends and where the feedline begins.

The EFOC56 4:1 Off-Center-Fed Inverted-L

The EFOC56 is different again. It is not a classic quarter-wave inverted-L, and it is not a conventional EFHW. It is an off-center-fed, voltage-fed system using a 4:1 transformer, with a long radiator and a defined return path.

In practical terms, it is intentionally arranged around a long radiator of about 56 m and a shorter return or counterpoise section of about 24 m, depending on the exact target frequency and installation.

EFOC56 concept on 160 m

short return / counterpoise      feed      long radiator
        ~24 m                     4:1          ~56 m
───────────────┬───────────────────────────────
               │
            transformer

Because the feedpoint is off-center, the current maximum is displaced. It is not at the feedpoint like a classic quarter-wave inverted-L, and it is not halfway from the feedpoint like a pure end-fed half-wave reference.

The EFOC56 on 160 m

If the total electrical system is roughly 80 m, then the center of the half-wave system is around 40 m from either end. With the feedpoint roughly 24 m from the short return end, the 160 m current maximum is approximately:

40 m - 24 m ≈ 16 m from the feedpoint into the long radiator

That is very important for an inverted-L installation.

EFOC56 inverted-L on 160 m, simplified

feed
  │
  │ vertical section, often 12–16 m
  │
  └──── horizontal or sloping radiator

Current:
moderate at feed → maximum near 16 m → falls toward far end

If the vertical section is 12 to 16 m, the 160 m current maximum can land near the top of the vertical section, near the bend, or just into the horizontal section.

This is one reason the EFOC56 can be attractive when space is limited. The high-current zone can be placed near the upper part of the support instead of deep out in the horizontal span. But it also means the vertical height, bend point, return path, and choke placement matter a lot.

The EFOC56 on 80 m

On 80 m, the total system is closer to a full wave. Using an 80 m total electrical length and a 24 m return side, the simplified current maxima are roughly at:

20 m and 60 m from the short end

Relative to the feedpoint at about 24 m from the short end, that means:

• one current maximum is about 4 m back into the return/counterpoise side
• one current maximum is about 36 m into the long radiator

This is why the EFOC56 return path and choke placement are not minor details. If the coax shield is intentionally used as part of the controlled return path, the choke defines where that return path stops and where the feedline begins.

Direct Comparison

Effective Installation Height, Takeoff Angle, and Efficiency

Height matters differently for these three antennas because the current maximum is not in the same physical place.

For top-band antennas, “height” should not only mean feedpoint height. The better question is:

This is why a classic radial-fed inverted-L, an EFHW16080 inverted-L, and an EFOC56 inverted-L can all produce useful low-angle radiation, but they do not reach their practical sweet spot at the same support height.

Classic Radial-Fed Inverted-L: Usable From About 9 m, Better Above 12–18 m

A classic quarter-wave inverted-L has its current maximum near the feedpoint and ground system. That is useful because the antenna behaves like a top-loaded vertical. Even with a modest vertical section, it can produce low-angle radiation because the vertical current starts at the base and the horizontal top wire adds capacitive loading.

In practice, a classic inverted-L can already be useful with a vertical section of about 9 m or more. Below that, it still works, but the vertical aperture becomes very short on 160 m and efficiency becomes increasingly dependent on the radial field and local ground loss.

The classic inverted-L improves strongly when the vertical section reaches 12 to 18 m. At that point, more of the high-current part of the antenna contributes useful vertical radiation, and the horizontal section becomes better top loading instead of just a low, lossy capacitance to ground.

The takeoff angle of a classic inverted-L is usually low enough for DX when the radial field is good and the vertical section is not extremely short. But the low-angle radiation is paid for with a large requirement: the return system must be excellent. A poor radial field turns part of the transmitter power into heat in the soil.

This is where the “120 radials” argument comes from. A classic inverted-L with a very good radial field can indeed be very efficient. But that does not mean every classic inverted-L is automatically more efficient than an EFHW or EFOC system. It only means the ground-return loss has been reduced. The remaining question is still how much useful current is actually radiating at a useful height and angle.

EFHW16080 Inverted-L: Wants More Height, Preferably 15 m or Higher

The EFHW16080 is more sensitive to the height of the horizontal section because the main current maximum on 160 m is not at the feedpoint. With an 81 to 82 m wire, the 160 m current maximum is roughly halfway along the wire. In a typical inverted-L installation, that often places the strongest current well into the horizontal or sloping section.

This means the EFHW16080 usually wants more physical height than a classic base-fed inverted-L. If the horizontal section is low, the current-rich part of the antenna is also low. That increases ground coupling, tree coupling, dielectric loss, pattern distortion, and nearby-object sensitivity.

As a practical rule, the EFHW16080 becomes much more convincing when the vertical support is around 15 m or higher, and better again when the horizontal section can remain high and clear over much of its length.

The EFHW16080 can still generate low-angle radiation in an inverted-L form. The vertical section contributes a vertical component, and the horizontal section acts partly as top loading and partly as radiator. But if the main current maximum is located in a low horizontal section, the antenna can become less efficient and more installation-sensitive than the SWR alone suggests.

This is why an EFHW16080 may look electrically “fine” at the transformer while still being compromised in real radiation efficiency. The transformer sees a high-impedance system. The receiver or transmitter sees a match. But the far field sees where the current actually flows.

EFOC56 Inverted-L: Often More Forgiving Around 12 m

The EFOC56 sits between the classic inverted-L and the EFHW16080. It is voltage-fed and off-center-fed, but its current maximum on 160 m is displaced closer to the feedpoint than in the EFHW16080.

With a long radiator of about 56 m and a defined return side around 24 m, the simplified 160 m current maximum can land roughly 16 m into the long radiator. In an inverted-L deployment with a 12 to 16 m vertical section, that places the high-current zone near the upper vertical section, near the bend, or just into the horizontal section.

That makes the EFOC56 attractive for lower practical support heights. A support around 12 m can already place a significant part of the high-current region near the top of the installation, instead of far out in a low horizontal wire.

The EFOC56 will usually not need a huge radial field like a classic quarter-wave inverted-L, but it absolutely needs a controlled return path. On some bands, the return side or coax-shield section can become current-rich. That means choke placement and return-path definition are not optional details. They are part of the antenna design.

Takeoff Angle: All Three Can Be Low, But Not for the Same Reason

All three antennas can produce useful low-angle radiation when installed above their practical minimum height. But the mechanism is different.

The important point is that “low takeoff angle” is not guaranteed by the name of the antenna. It depends on the current distribution and the physical location of the current-rich wire.

A classic inverted-L has the cleanest textbook low-angle story: vertical current near the base, horizontal top loading, radial return system. But it also has the highest ground-system demand.

The EFHW16080 has the highest height demand because its 160 m current maximum is often far into the horizontal section. It can work very well, but it does not like being low and surrounded by lossy objects.

The EFOC56 can be more forgiving in medium-height installations because the 160 m current maximum can sit closer to the upper vertical section or bend. That can make it a very practical compromise when 120 radials are not realistic.

Efficiency Is Not One Number

Total efficiency is not determined by the antenna type alone. It is the result of several losses added together:

• ground or radial-system loss
• return-path and common-mode loss
• transformer or matching loss
• conductor loss
• tree, roof, building, and soil coupling loss
• feedline loss caused by high SWR or uncontrolled current

This is why the statement “a classic inverted-L with 120 radials is the most efficient” is only partly true.

If the classic inverted-L has a good vertical section, a high top wire, excellent radials, low-loss wire, and no nearby lossy objects, then yes, it can be extremely efficient. In that idealized case, the 120-radial field strongly reduces ground loss and the system can be a superb top-band radiator.

But in real gardens, the answer is less absolute. Many installations do not have 120 full-size radials. Many have short radials, bent radials, poor soil, fences, sheds, buildings, wet trees, buried cables, and compromised feedpoint locations. In those cases, the classic inverted-L may still be good, but it is not automatically the winner.

Practical Efficiency Comparison by Deployment

A More Realistic Ranking

There is no universal efficiency ranking, but the practical behavior usually looks like this:

The Honest Conclusion

A classic inverted-L with 120 radials can be extremely good. But “can be” is not the same as “always is.” The radial field solves one major problem: ground-return loss. It does not automatically solve limited vertical height, low horizontal wire coupling, nearby objects, or pattern compromise.

The EFHW16080 and EFOC56 are not magic ways to escape physics. They still need a return path, height, current-rich wire in the clear, and good common-mode control. But they move the design problem away from “build a broadcast-style radial system” and toward “place the current maxima intelligently.”

So the real comparison is not “radials versus no radials.” The real comparison is:

Which design places the most useful current highest and clearest, with the least loss in the return system, transformer, ground, and surrounding environment?

That is why a 120-radial classic inverted-L may win in a large open field, while an EFOC56 or high EFHW16080 may be the smarter real-world solution in a normal property.

The Low-Angle Radiation Question

It is tempting to say that a classic quarter-wave inverted-L must always win because it has a current maximum at the base. But that is not the whole story.

That same current maximum is also very close to the ground system and lossy soil. A large radial field reduces the loss, but it does not make the earth perfect. Even many radials over good soil are still part of a real-world installation, not an ideal textbook ground plane.

An EFHW16080 inverted-L or EFOC56 inverted-L may not place the absolute current maximum at the base, but it can place important current-rich sections higher in the structure. The horizontal section also behaves partly as capacitive top loading and partly as radiator. In the right installation, that can still produce useful low-angle radiation on the top bands.

This does not mean the EFHW or EFOC approach is always better. It means the comparison is not as simple as “current maximum at the feedpoint equals better antenna.” The real question is where the current-rich wire sits in space, how much of it is vertical, how much is horizontal, how lossy the return path is, and how well common-mode current is controlled.

The Practical Answer

Yes, the current-distribution difference becomes much more prominent in voltage-fed inverted-L systems.

In a classic inverted-L, the current maximum is usually near the feedpoint and base. Lowering the horizontal part changes capacitance, impedance, ground coupling, losses, and pattern, but it usually does not completely relocate the main current maximum.

In an EFHW16080 inverted-L, the feedpoint is a current minimum and voltage maximum. On 160 m, the main current maximum is roughly halfway along the wire, often in the horizontal section. On 80 m, there are multiple current maxima. Therefore, horizontal wire height can directly affect the current-rich radiating portions.

In an EFOC56 inverted-L, the feedpoint is off-center rather than at the extreme end. On 160 m, the main current maximum can land near the top of a 12 to 16 m vertical section or near the bend. That makes the vertical height, bend point, horizontal height, return path, and choke placement very important. On 80 m, the return path can also become current-rich, so it must be treated as part of the antenna system.

So with an EFHW16080 or EFOC56, the question is not merely:

How high is the feedpoint?

The better question is:

Where are the current maxima on each band, and are those current-rich parts vertical, horizontal, high, low, clear, or close to lossy objects?

That question tells you far more about real inverted-L performance than the shape alone.

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