Inverted-U Configuration for the EFHW16080

Our 81 m end-fed half-wave antenna for 160 m and 80 m is typically installed as an inverted‑L or sloper. However, when two elevated supports are available, a shallow inverted-U layout can offer excellent performance for both DX and NVIS operation, with a balance between low-angle efficiency and horizontal coverage.

Physical Configuration

  • Total wire length: 81 m
  • Transformer: 68:1 (designed for ~3400 Ω feedpoint impedance)
  • Feedpoint location: At the base of one leg, ~2 m above ground
  • Wire runs upward at ~45° to a central horizontal span (10–15 m high), then slopes downward at ~45° to the far support
  • End support height: 5–6 m
  • Horizontal span: ~30 m between end supports

Visual layout:

     /------------------\
    /                    \
   /                      \
--                          --

Current Distribution and Behavior

In this configuration, the current maximum is near the feedpoint, rising along the first sloping leg and into the start of the horizontal span. Current tapers toward the far end of the wire, reaching a minimum at the far end. This is typical of end-fed designs, where current distribution is asymmetrical.

Radiation Characteristics

  • 160 m: Operates as a half-wave antenna with strong low-angle radiation due to elevated current near the sloping and horizontal sections. Excellent for DX and NVIS.

  • 80 m: Operates as a full-wave with two broadside azimuth lobes and a moderate take-off angle, supporting both DX and NVIS depending on propagation and height.

This antenna supports dual-mode operation: low-angle radiation for DX and higher-angle components suitable for regional NVIS communication.

Advantages

  • Dual-band 160 m and 80 m operation with one wire
  • Low-angle DX and NVIS performance
  • Feedpoint remains near ground for easy access
  • No ground radials required; coax shield and a high-Z stainless steel ground stake are typically sufficient
  • Balanced horizontal layout reduces pattern distortion

Considerations

  • Common-mode current risk due to near-ground feedpoint; use a choke near the shack
  • Maintain height of the horizontal section for low-angle efficiency
  • Avoid nearby structures that may couple into the sloping legs

Summary Table

Parameter Value / Recommendation
Wire length 81 m
Transformer type 68:1 UnUn (matched to 3400 Ω)
Feedpoint height ~2 m
Horizontal span height 10–15 m
End-point height 5–6 m
Horizontal span width ~30 m
Counterpoise Coax shield (laid out or buried)
Choke recommendation Place common-mode choke near shack

When to Choose This Layout

  • You want a compact, dual-band antenna for 160 m and 80 m
  • You have two elevated supports and room for 81 m of wire
  • You need a balance of low-angle DX and NVIS coverage
  • You prefer a ground-level feedpoint for ease of installation and troubleshooting

This layout is an efficient, field-friendly option that supports both local and long-distance HF communication — all from a single wire with minimal infrastructure.

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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.