The EFLW37: A Quick-and-Dirty Antenna for 80m Local Work

The End-Fed Long Wire 37 (EFLW37) is a 37-meter long wire antenna often deployed by radio amateurs looking for a simple and fast solution to get on the 80-meter band. It’s commonly used with a 9:1 UNUN and a tuner, making it attractive due to its flexibility and ease of matching. However, like its 51-meter cousin, the EFLW37 is a compromise antenna with distinct limitations.

Why 37 Meters? A 37-meter wire hits a sweet spot for those wanting basic 80-meter operation without needing a huge amount of space. It’s long enough to be usable on 80 meters, especially with tuner assistance, but short enough to fit into many average-sized gardens. It offers a relatively simple way to get on air quickly.

Matching vs. Efficiency The EFLW37 is easy to match using a 9:1 UNUN and an antenna tuner. But as with any antenna, easy matching doesn’t imply good performance. Especially at low heights—where many hams install these wires—ground losses dominate, and the antenna functions mostly as a cloud burner, radiating at very high angles. This is useful for local and regional contacts but poor for DX.

Unsuitable for Higher Bands Unlike end-fed half-waves that resonate on harmonic bands, the EFLW37 is a non-resonant long wire. This means that for bands like 15m and 10m, its length creates multiple impedance peaks and current nulls, making it difficult to match efficiently. Even if matched, its low height continues to hinder far-reaching radiation. Therefore, it’s not suitable as a multiband solution.

A Local-Only Performer The EFLW37 shines in specific use cases: NVIS (Near Vertical Incidence Skywave) communication on 80m and sometimes 60m. It can be excellent for local or regional nets, emergency communications, or chatting with nearby friends. For this role, its performance is quite acceptable.

Conclusion The EFLW37 is not a DX antenna—it’s a tool for quick deployment and local work on 80m. Its ease of setup and flexibility make it a go-to option for emergency use or for amateurs operating in constrained environments. Understand its limitations, and it will serve you well in its intended role.

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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.