The End-Fed Half-Wave (EFHW) antenna has become a popular choice for HF enthusiasts due to its simplicity and efficiency. For low-band operation on 160m and 80m, the inverted-L configuration offers an effective compromise between vertical and horizontal radiation patterns. This article compares the performance of the EFHW16080 antenna when deployed with a 15m mast versus a 20m mast, focusing on radiation patterns, NVIS (Near-Vertical Incidence Skywave) vs DX performance, and overall efficiency.

The EFHW 160/80m Inverted-L Setup

The EFHW16080 is designed as a dual-band antenna, offering full-size efficiency on both 160m and 80m. It is typically deployed as an Inverted-L, where the first portion rises vertically before transitioning to a horizontal section. The height of the vertical segment significantly impacts the takeoff angle, ground losses, and overall radiation pattern.

Comparison: 15m vs 20m Mast

Parameter	15m Mast Configuration	20m Mast Configuration
Vertical Segment	15m vertical + horizontal	20m vertical + horizontal
Ground Losses	Higher due to lower vertical section	Lower due to increased height
NVIS (80m Band)	Stronger NVIS for regional contacts	Slightly reduced NVIS effect
DX Performance (80m Band)	Good DX, but more energy at higher angles	Lower takeoff angle, better DX
DX Performance (160m Band)	Moderate DX capability	Improved DX due to lower takeoff angle
Efficiency	Slightly lower due to higher near-field losses	Higher efficiency due to better elevation
Mechanical Load	Lower wind load, easier installation	Higher wind load, more robust support needed

Radiation Pattern Considerations

80m Band:

• The 15m mast results in a stronger NVIS signal, ideal for regional contacts within a few hundred kilometers.
• The 20m mast lowers the takeoff angle slightly, making it better suited for DX contacts but still usable for NVIS.

160m Band:

• The higher 20m mast significantly improves DX performance by lowering the takeoff angle.
• The 15m mast results in higher-angle radiation, making long-haul DX more challenging.

Efficiency and Losses

• The vertical section of the Inverted-L contributes to ground-wave coupling, and ground losses increase with a shorter vertical element. The 20m mast has a clear advantage in reducing near-field ground losses.
• Radial systems and grounding remain critical for both configurations, but the 20m version benefits from less dependency on a large radial network compared to the 15m version.

Practical Considerations

Installation and Structural Concerns

15m Mast:

• Easier to install, lower wind load.
• Suitable for locations with space constraints or moderate wind conditions.

20m Mast:

• Requires a stronger guying system.
• Provides better long-distance performance, especially on 160m DX.

Conclusion

For operators focusing on NVIS and regional contacts, the 15m mast offers a more practical setup. However, for those prioritizing DX performance, especially on 160m, the 20m mast is the superior choice due to its lower takeoff angle and improved efficiency. The decision ultimately depends on available space, installation complexity, and the operator’s primary communication goals.

Article written by Joeri Van Dooren, ON6URE – RF engineer, antenna designer, and founder of RF.Guru. With extensive experience in active and passive antenna systems, high-power RF transformers, and custom RF solutions, Joeri shares insights into cutting-edge radio communication technologies.