The FullHalfWave Series (EF FHW): Dual Half-Wave EFHWs Reimagined for Real-World DX

What if a single end-fed wire could be designed to target two half-wave resonant bands, such as 80m and 40m or 40m and 20m, without relying on conventional high-Q resonant traps? That is the idea behind the FullHalfWave series, also referred to as EF FHW: a dual-band end-fed half-wave concept being developed for practical inverted-L installations.

The goal is not “multi-band magic.” The goal is a deliberate two-band wire antenna where both intended bands are treated as real design targets, not accidental tuner matches.

What Makes the FullHalfWave Concept Different?

The FullHalfWave antennas are dual half-wave EF FHW designs that use a non-resonant current-shaping element instead of a conventional resonant LC trap. This element is intended to influence the current distribution on the higher band while allowing the full wire length to remain useful on the lower band.

That distinction matters. A conventional resonant trap creates a sharp frequency-selective interruption in the antenna. The FullHalfWave approach is intended to be more gradual: current shaping instead of hard band switching.

Available Design Variants for Inverted-L Installations

• FullHalfWave 8040 → approximately 61.0 m of wire, targeting 80m and 40m half-wave operation
• FullHalfWave 4020 → approximately 31.4 m of wire, targeting 40m and 20m half-wave operation

Due to physical length and the way the current-shaping element is intended to work, this concept is best suited for these two band combinations. Final dimensions, matching, bandwidth, and installation sensitivity still need to be confirmed through modelling and field testing.

Why an Inverted-L Layout?

An inverted-L is often a practical way to install a long low-band wire when a fully vertical radiator is not possible. The vertical section contributes useful vertically polarized radiation, while the horizontal top section provides electrical length and helps complete the half-wave structure.

For DX-oriented work, the vertical rise is important. A taller vertical section generally improves the low-angle radiation component, especially on the lower band. However, the final pattern depends strongly on installation height, soil, nearby structures, feedline routing, and the exact ratio between the vertical and horizontal sections.

FullHalfWave 8040 Design Target

On 80m, vertical height is especially important. More vertical rise generally improves the low-angle component, but actual results depend heavily on the installation environment.

FullHalfWave 4020 Design Target

Why This Concept Is Technically Interesting

• Both bands are treated as intentional design targets rather than incidental tuner matches.
• The wire lengths are chosen to support half-wave operation on the lower band and controlled operation on the higher band.
• The design avoids using a conventional high-Q resonant trap as the main band-separating mechanism.
• The inverted-L layout may provide a useful mix of vertical and horizontal radiation components, depending on height and geometry.
• The current-shaping element is intended to influence the higher-band current distribution without behaving like a traditional resonant trap.

These points describe the design intent. They should not yet be read as measured gain, measured efficiency, final bandwidth, power-handling, or confirmed DX-performance claims.

Transformer Matching and Feedpoint Behavior

Actual feedpoint impedance will vary with wire height, vertical-to-horizontal ratio, ground conditions, nearby structures, feedline routing, transformer construction, and any counterpoise or common-mode control used. The transformer ratios above should therefore be considered starting points for testing, not final universal recommendations.

About the Non-Resonant Current-Shaping Element

On each design, the non-resonant current-shaping element is intended to have its strongest effect on the higher band, while allowing the full wire to remain active on the lower band. This is different from using a conventional resonant trap that sharply isolates part of the wire at a specific frequency.

The expected behavior still needs to be confirmed with measured and modelled data. In particular, current-distribution plots are essential. Without current-distribution data, it is not possible to prove that the higher-band section behaves as intended or that the lower-band current remains clean across the full wire.

Validation Still Required

Before final performance claims are made, the FullHalfWave concept should be supported by measured or published data, including:

• NEC or equivalent current-distribution models for both bands
• Feedpoint impedance and SWR sweeps across the intended band segments
• Measured bandwidth in representative inverted-L installations
• Transformer loss and temperature testing at defined power levels and duty cycles
• Common-mode current measurements with practical feedline lengths
• Field reports comparing real installations against the modelled behavior

Once those results are available, this article can be updated with measured data, installation notes, and any necessary design changes.

The FullHalfWave EF FHW Series

The FullHalfWave EF FHW Series is an experimental dual-band end-fed half-wave concept for operators who want to explore practical inverted-L antennas for two related HF bands. The design target is simple: two intentional half-wave bands from one wire, using current control rather than conventional resonant trap switching.

For now, the correct technical position is clear: promising concept, interesting current-shaping approach, but still pending validation before claims about final efficiency, gain, bandwidth, DX performance, or power handling can be made.

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