Tuning Advice for EFLW Antennas

 

The End-Fed Long Wire (EFLW) antennas are straightforward to set up and forgiving when it comes to tuning, making them ideal for multiband HF operations. Follow these simple steps to ensure optimal performance:

1. Initial Setup

  • Mounting Height: Aim for a height of 6–10 meters for general use. Lower heights are acceptable for NVIS (80m and 40m) operations.
  • Clear Area: Keep the wire away from large metal objects, buildings, or dense vegetation to avoid detuning.
  • Feedpoint Position: Secure the feedpoint and ensure it’s well-grounded.

2. Measure and Adjust SWR

  • Use an antenna analyzer or SWR meter to check performance across the desired bands.
  • Adjust the Wire Length:

3. Environmental Adjustments

  • Recheck tuning periodically, especially after seasonal changes or weather events.
  • If tuning changes significantly, ensure all connections are secure and check for corrosion.

4. Optional Antenna Tuner

  • While most EFLW antennas do not require a tuner for multiband use, a tuner can help optimize performance for outlier frequencies or mismatched loads.

5. Proven Lengths

The following wire lengths have been tested and proven effective when paired with a 9:1 unun and a suitable antenna tuner.

21.64 meters is a versatile length that performs well on the 40m-10m bands, with 80m being usable but somewhat compromised due to the shorter wire length.

36.27 meters extends coverage to include 160m, although its performance on this band is limited, while it works effectively from 80m-10m. (alternative length is 35.5 meters)

For more robust multi-band coverage, 50.6 meters supports 160m-10m, though its efficiency on 160m remains a compromise. (alternative length is 49.38 meters)

These lengths are designed to avoid resonances, ensuring broad-band operation with minimal tuning challenges.

The typical SWR values for a long wire antenna with a 9:1 unun vary significantly across the bands due to the inherent impedance mismatches and how the wire length interacts with specific frequencies. Below is a general guide to the expected SWR values across common amateur bands, assuming no tuner is used:

General SWR Characteristics

1. 160m (1.8 MHz):

    • SWR: Often high (5:1 or more), especially for shorter wires (e.g., <36.27 m). Longer wires (e.g., 50.6 m) may show improvement but still require a tuner.

2. 80m (3.5–4.0 MHz):

    • SWR: Typically moderate to high (2:1 to 4:1), depending on wire length. A 36.27 m wire works reasonably well here.

3. 40m (7.0–7.3 MHz):

    • SWR: Usually lower (1.5:1 to 3:1), as this band is well within the effective range for most wire lengths.

4. 20m (14.0–14.35 MHz):

    • SWR: Often low (1.5:1 to 2.5:1). This is one of the more efficient bands for many long wire lengths.

5. 15m (21.0–21.45 MHz):

    • SWR: Can range from low to moderate (1.5:1 to 3:1), depending on the exact length of the wire.

6. 10m (28.0–29.7 MHz):

    • SWR: Typically low (1.5:1 to 2.5:1). Most wire lengths perform well on this higher-frequency band.

Key Notes:

• High Impedance Variations: A 9:1 unun reduces the impedance mismatch but cannot guarantee a perfect match across all bands.

• Counterpoise/Ground: A good counterpoise or ground system significantly impacts SWR performance and overall efficiency

By using a tuner, the system becomes far more versatile and capable of operating effectively across all bands.

Conclusion

EFLW antennas are simple and efficient multiband solutions. With minimal tuning adjustments and proper setup, they deliver excellent performance for both DX and local communication. Enjoy the ease and flexibility these antennas provide!