These Two Inverted L End-Fed Antennas Will Crush DX on 160/80m and 80/40m

When chasing performance on the low bands, two practical end-fed inverted-L designs stand out:

• 160/80m end-fed inverted L with a high-ratio transformer around 68:1
• 80/40m end-fed inverted L with a high-ratio transformer around 70:1

Both are single-wire, single-feedpoint antennas intended to provide useful low-angle radiation on the low bands while remaining simpler to install than a full-size vertical, a large radial-fed system, or a multi-support wire array.

But they are not magic antennas. Their performance depends heavily on installation height, wire layout, soil conditions, transformer quality, common-mode control, and the quality of the RF return path or counterpoise system.

The Big Correction: Wire Length and Wavelength

The most important correction is simple: a 38–41 m wire is not a full wave on 80 m, and it is not two wavelengths on 40 m.

• 38–41 m is approximately a half-wave wire on 80 m.
• 38–41 m is approximately a full-wave wire on 40 m.
• 79–81 m is approximately a half-wave wire on 160 m.
• 79–81 m is approximately a full-wave wire on 80 m.

That correction matters because current distribution determines where the antenna actually radiates. In an end-fed half-wave or full-wave system, the feedpoint is typically a high-voltage, low-current point. The strongest radiation normally comes from the current-rich sections of the wire, not simply from the feedpoint or from the vertical section because it happens to be vertical.

160/80m End-Fed Inverted L with 68:1 Transformer

Geometry and Design

• Wire length: approximately 79–81 m
• Feedpoint height: minimum around 1 m, ideally 2–5 m
• Vertical section: preferably at least 15 m tall, with the remainder horizontal or sloped
• Matching: high-ratio transformer, typically around 68:1
• Grounding/counterpoise: a ground rod may help with static bleed and safety bonding, but it should not be treated as a complete RF ground

Behavior on 160 Meters

At approximately 79–81 m total length, the antenna is roughly a half-wave end-fed wire on 160 m. It is not a quarter-wave top-loaded vertical in the classical radial-fed sense.

In an inverted-L layout, the vertical section can contribute useful vertically polarized radiation, especially when it is tall. However, the current maximum of a half-wave end-fed system is normally away from the feedpoint. With a 15 m vertical leg, the strongest current on 160 m may still be well into the horizontal or sloping section.

That means the horizontal section is not just a harmless top wire. Its height, route, nearby objects, and loss environment can strongly affect performance.

Behavior on 80 Meters

On 80 m, the same 79–81 m wire is approximately one wavelength long. This creates multiple current lobes along the wire and a more directional pattern than a simple vertical. Depending on height and orientation, it can provide useful DX performance, but it should not be described as an omnidirectional vertical antenna.

Why It Works

• The total wire length is close to a half wave on 160 m and a full wave on 80 m.
• The vertical section can add useful low-angle, vertically polarized radiation.
• The high-impedance feedpoint can be transformed toward 50 ohms using a suitable high-ratio transformer.
• The single feedpoint keeps the installation practical for real gardens and field sites.
• A controlled RF return path and proper choking make the system more predictable.

80/40m End-Fed Inverted L with 70:1 Transformer

Geometry and Design

• Wire length: approximately 38–41 m
• Feedpoint height: minimum around 1 m, ideally 2–5 m
• Vertical section: preferably at least 15 m, with the remaining wire horizontal or sloped
• Matching: high-ratio transformer, typically around 70:1
• Grounding/counterpoise: counterpoise wire, radials, or a controlled coax-counterpoise section is strongly preferred over relying on a ground rod alone

Behavior on 80 Meters

A 38–41 m wire is approximately a half-wave end-fed antenna on 80 m. This is the classic high-impedance end-fed half-wave condition. The 70:1 transformer is used to transform the several-kilohm feedpoint impedance closer to the impedance range expected by 50-ohm coax.

In an inverted-L layout, the vertical section can help produce lower-angle radiation than a low horizontal wire. The exact result depends on the vertical height, the position of the current maximum, the horizontal length, the soil, and nearby conductive or lossy objects.

Behavior on 40 Meters

On 40 m, the same 38–41 m wire is approximately one wavelength long. The antenna behaves as an end-fed full-wave wire. The radiation pattern becomes more lobed and directional than on 80 m, with useful gain in some directions and weaker coverage in others.

That is not a defect. It is simply full-wave wire behavior. Orientation matters more on 40 m than many operators expect.

Why It Works

• The wire is close to a half wave on 80 m and a full wave on 40 m.
• The vertical section can contribute useful low-angle radiation when current-rich parts are placed favorably.
• There are no traps or loading coils in the radiating wire.
• The feedpoint can be matched with a suitable high-ratio transformer.
• A deliberate counterpoise and common-mode choke help reduce shack RFI and pattern uncertainty.

Transformer Impedance Ratios: Why 68:1 and 70:1?

Both designs can present high feedpoint impedances, often in the several-kilohm range. The exact impedance depends on wire length, frequency, height, ground conditions, nearby objects, transformer construction, and how the return path is implemented.

A 68:1 or 70:1 transformer transforms that high impedance down toward the range expected by 50-ohm coax. The difference between 68:1 and 70:1 is not critical. These ratios are practical engineering choices, not sacred numbers.

For higher power, the transformer must be designed for the expected voltage and flux levels. End-fed half-wave and full-wave antennas can produce high RF voltage at the feedpoint, especially when the match is imperfect or the antenna is operated outside its intended range.

Ground Rods, Radials, and the RF Return Path

A ground rod is not the same thing as an efficient RF ground. It may be useful for static bleed, lightning protection bonding, or safety grounding, but by itself it is usually a lossy and unpredictable RF return path on the low bands.

End-fed antennas always need some form of return current. If no deliberate counterpoise, radial system, or controlled coax counterpoise is provided, the coax shield and connected station equipment often become part of the antenna system.

That may still make contacts, but it can also:

• increase loss, especially on 160 m;
• raise the received noise floor;
• distort the radiation pattern;
• create RF in the shack;
• make tuning change when coax length, routing, or grounding changes.

For more predictable results, use one or more of the following:

• several short counterpoise wires near the feedpoint;
• a modest radial field, especially for 160 m operation;
• a deliberately used coax counterpoise section, followed by a strong common-mode choke;
• bonding to an existing low-impedance ground system where appropriate;
• good weatherproofing and strain relief at the transformer.

Common-Mode Current: Do Not Let the Coax Decide the Antenna

In an end-fed system, the coax often becomes part of the RF return path unless the installation deliberately controls where the antenna ends and where the feedline begins. This is why choke placement matters.

A choke placed directly at the transformer may suppress current too early if the system has no other return path. A choke placed after a defined counterpoise or coax-counterpoise section can help define the antenna boundary more cleanly.

Summary Table

Conclusion

Both antennas can be effective low-band DX solutions for operators who want useful performance from a single wire and a single feedpoint. The key is to describe them correctly.

The 38–41 m version is approximately a half-wave antenna on 80 m and a full-wave antenna on 40 m. The 79–81 m version is approximately a half-wave antenna on 160 m and a full-wave antenna on 80 m.

Installed with a tall vertical section, a suitable transformer, a deliberate RF return path, and common-mode control, these inverted-L end-fed antennas can deliver strong real-world performance. Without those details, they may still make contacts, but efficiency, noise, pattern, and RF-in-the-shack behavior become much less predictable.

• No traps or loading coils in the radiating wire
• Useful low-angle radiation when installed with sufficient vertical height
• Single feedpoint and relatively simple deployment
• Best results when used with a proper RF counterpoise, radial system, or controlled coax-counterpoise section

If you only have room for one long wire, an end-fed inverted L can be an excellent choice. Just remember that the ground system, counterpoise, current distribution, and choke placement matter just as much as the wire length.

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