The EFLW51: A Quick-and-Dirty Compromise for 160m

The End-Fed Long Wire 51 (EFLW51) antenna, with a total length of approximately 51 meters, is often seen as a quick-and-dirty solution to get on the 160-meter band. It has a reputation for being easy to match, especially when used with a high-impedance transformer like a 9:1 UNUN, making it an attractive choice for radio amateurs with limited space or resources. However, despite its ease of deployment, the EFLW51 comes with several limitations that make it far from a high-performance antenna.

Why 51 Meters? The 51-meter length is a convenient compromise—it’s long enough to provide resonance or near-resonance on 160 meters when matched correctly but not so long that it becomes unwieldy for the average backyard. This makes it a practical option for hams looking for a simple wire solution that “just works” on top band.

Matching vs. Performance While the EFLW51 may be easy to match with a tuner and a proper UNUN, matching doesn’t equate to efficiency. A matched antenna simply means that the impedance is transformed to a level your transmitter can handle—it says nothing about how well the antenna radiates. Due to its height (often low to the ground) and random length, the EFLW51 tends to suffer from high ground losses, poor radiation angles, and overall mediocre performance.

Not Great for Higher Bands The 51-meter length becomes more of a liability than a benefit above 80 meters. On bands like 20m through 10m, the wire length creates multiple high-impedance points and current nulls, leading to erratic SWR curves and inefficient radiation patterns. The result is a less predictable antenna that becomes harder to match and less effective the higher you go in frequency. In many cases, a dedicated antenna or a shorter multiband EFHW would outperform the EFLW51 significantly on those bands.

Use Case: Emergency or Stealth Setup Where the EFLW51 shines is in emergency or stealth setups. If you need to deploy something quickly, or if you're restricted to low-visibility antennas, it can be a lifesaver. It allows for basic operation across a wide frequency range with the help of a good tuner, making it a solid compromise when the ideal isn't possible.

Conclusion The EFLW51 is not a high-performance antenna—it's a compromise. It provides a quick and relatively easy way to get on 160 meters but sacrifices efficiency, especially on the higher HF bands. If you're aware of its limitations and use it within its strengths—primarily as a basic 160m solution—then it can be a useful part of your toolkit. Just don't expect DX-chasing performance on 20 through 10 meters.

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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.